Manual of Modern Hydronics

Transcription

1 Manual of Modern Hydronics SECOND EDITION Residential Industrial Commercial Snow and Ice Melt Professional Radiant Heating Solutions

2 M ANUAL OF M ODERN H YDRONICS

3 This manual is published in good faith and is believed to be reliable. Data presented is the result of laboratory tests and field experience. IPEX maintains a policy of ongoing product improvement. This may result in a modification of features or specifications without notice by IPEX. All rights reserved. No part of this book may be used or reproduced in any manner whatsoever without prior written permission. For information, address IPEX, Marketing, 2441 Royal Windsor Drive, Mississauga, Ontario L5J 4C IPEX WR003UC

4 INTRODUCTION MODERN HYDRONICS Each year, construction begins on tens of thousands of new buildings all across North America. Thousands more undergo renovation. Whether new or remodeled, most of these buildings will require the installation or alteration of a comfort heating system. Along with hundreds of other decisions, the owners of these buildings must eventually select a heating system. Unfortunately and in most cases unintentionally the choice is often based on factors that in the end, don t provide the comfort the owner or the occupants are expecting. In many cases the heating system, which is often thought of as a necessary but uninspiring part of the building, is selected solely on the basis of installation cost. In other cases, the selection is based strictly on what the builder offers or recommends. Still other times, the choice is based on what s customary for the type of building being constructed or its location. Such decisions often lead to years of discomfort in thermally-challenged buildings. In retrospect, many people who have made such decisions and lived with the consequences would quickly change their mind if given the opportunity. Most would gladly spend more (if necessary) for a heating system that meets their expectations. It doesn t have to be this way! Few people don t appreciate a warm, comfortable interior environment on a cold winter day. A warm home or workplace lets them forget about the snow, ice, and wind outside. It s an environment that encourages a sense of well being, contentment, and productivity. Hydronic heating can provide such an environment. It can enable almost any building to deliver unsurpassed thermal comfort year after year. Hydronics technology is unmatched in its ability to transfer precise amounts of heat where and when it s needed. The warmth is delivered smoothly, quietly, and without objectionable drafts that cause discomfort, or carry dust 1

5 THE IPEX MANUAL OF MODERN HYDRONICS and airborne pollutants through the building. Properly designed hydronic systems are often significantly less expensive to operate than other forms of heating. A wide variety of hydronic heating options exist for everything from a single room addition to huge industrial and commercial buildings. Knowledgeable designers can configure systems to the exact needs of each building and its occupants. The systems can then be installed without compromising the structure or aesthetics of the building. In short, hydronic heating is for discriminating people who expect buildings to be as comfortable to live and work in as they are elegant to look at. Hydronic heating sets the standard of comfort, versatility and efficiency against which other forms of heating should be measured. Now Is the Time There has never been a better time for heating professionals to be involved with hydronics. New materials, design tools and installation techniques offer unprecedented and profitable opportunities to progressively-minded professionals. IPEX produced this manual to assist you in deploying hydronic heating technology using the latest design and installation strategies. It is our goal to help you to meet the exact needs of your customer using the finest methods and materials available for modern hydronic heating. We want to inspire your thinking, and give you a can do attitude when faced with job requirements that often lead to compromise when undertaken without the versatility hydronics has to offer. A Universal Piping System Piping is obviously a crucial component in any hydronic system. Not only must it safely contain heated and pressurized water but it must also resist corrosion, withstand thermal cycling and be easy to install. Kitec XPA TM pipe was launched by IPEX in 1988 as a multipurpose pressure pipe with many potential uses in hydronic heating, including potable water distribution. Kitec s construction combines the best properties of both aluminum and cross-linked polyethylene (a.k.a. PEX) to create a unique composite tube that can be used in applications often beyond the limits of either metal or plastic alone. The aluminum core of Kitec pipe provides strength, yet allows for easy bending. It results in a tube that expands and contracts far less than all plastic tubing when heated and cooled. It also provides an extremely effective barrier against oxygen penetration, which can lead to corrosion of other hydronic system components. The outer PEX layer protects the integrity of the aluminum core, shielding it from abrasion or chemical reactions when embedded in materials such as concrete. The inner PEX layer provides a smooth surface for excellent flow characteristics as well as chemical resistance. The unique construction of Kitec tubing also provides excellent flexibility for easy installation, especially in tight situations where rigid pipe is simply out of the question. Unlike most plastic tubing, Kitec retains the desired shape when bent. It can also be easily straightened for a neat and professional appearance in exposed locations. Kitec pipe is truly a universal product suitable for all types of service in hydronic heating systems. From heated floor slabs, to heated walls and ceilings or snowmelting systems to baseboard circuits, you ll find the qualities Kitec possesses will soon make it the tubing of choice for all your hydronic heating needs. From piping to systems In addition to Kitec tubing, IPEX also offers a complete line of accessories such as tubing connectors, adapter fittings, manifolds and WarmRite Floor Control Panels. These products are designed to allow fast and easy installation and can be used in a variety of applications. In the sections that follow, we ll show you how to apply these products in new ways that let you design and install systems that epitomize the quality and comfort hydronics has long been known for. These are techniques that let you profitably take on the challenging jobs others stay away from while steadily building your reputation as a true comfort professional. Together with IPEX, you can successfully harness the almost endless possibilities offered through modern hydronics technology. 2

6 THE IPEX MANUAL OF MODERN HYDRONICS TABLE OF CONTENTS Section 1: Consider the Possibilities! Section 2: Heat Source Options Section 3: Water Temperature Control Section 4: Radiant Floor Heating Methods Section 5: Radiant Walls and Ceilings Section 6: Manifold Systems Section 7: Pre-Assembled Control Panels Section 8: Distribution systems for Hydronic Heating Section 9: Designing Multiple-Load Hydronic Systems Section 10: Radiant Pipe and Tubing Section 11: Hydronic Snow and Ice Melting Section 12: IPEX Radiant TM Design Software Appendix 5

7 SECTION 1 CONSIDER THE POSSIBILITIES! Question: What kinds of heating loads can be handled using modern hydronics technology? Answer: Almost any load you can think of! For years the concept of hydronic heating evoked thoughts of cast-iron radiators or fin-tube baseboards in homes and commercial buildings and not much else. Early hydronic systems were usually classified as being residential or commercial in nature. Residential systems were the domain of plumbing / heating contractors. Rule of thumb design was usually good enough given the limited variety of systems installed. The piping and control methods used in these systems remained essentially unchanged between the 1950 s and the 1980 s in North America. Commercial hydronic systems were a world apart from their residential counterparts. Techniques such as primary / secondary piping, multiple water temperature distribution systems, and outdoor reset control were successfully deployed in commercial systems, but almost never considered for residential applications. A New Era for Hydronics Times have changed considerably, hydronically speaking. Residential and commercial systems now share some common piping and control strategies. Successful installation strategies first developed decades ago are being redeployed using modern materials and control strategies that ensure decades of reliable and energy efficient operation. 7

8 THE IPEX MANUAL OF MODERN HYDRONICS The days when hydronic systems consisted solely of cast-iron radiators, copper or black iron pipe and fintube baseboard are gone. New hardware such as Kitec pipe and WarmRite Control Panels now make it possible to install quality systems that serve a multitude of heating loads. Modern systems can incorporate a variety of heat emitters. Each are selected to match the exact thermal, aesthetic and budget constraints of a project. Today, hydronic heating contractors are being asked to furnish heating systems for everything from small apartments to large custom-built houses, as well as a variety of commercial buildings. Each job brings its own particular set of requirements. Many modern systems contain several types of heat emitters operating at different water temperatures and divided up into a dozen or more independently controlled zones. Some contractors hesitate to take on such challenging systems. Others recognize that with the right materials and design methods, these systems are not only possible, but also offer excellent profit potential as well as the likelihood of future referrals. Contractors who recognize what modern hydronics technology has to offer, and who take the time to learn how to apply new design techniques and hardware, are enjoying unprecedented business growth. Discriminating clients seek out these hydronic specialists because they offer what their competition cannot the ability to pull together modern materials and design methods to create heating systems specifically tailored to their client s needs. To take advantage of such opportunities, you need to know how to use these modern piping and control techniques. That s what this manual is all about. It will show you how to use Kitec pipe, WarmRite Control Panels, and other hardware to assemble state-of-theart hydronic systems that deliver comfort, economical and reliable operation and most importantly, satisfied customers. Armed with this knowledge you ll find modern hydronic heating to be among the most satisfying and profitable niches in the HVAC industry. IPEX Incorporated is ready, willing, and able to help you achieve the many benefits offered to those who know how to apply modern hydronics technology. One System that Does It All The concept that best describes modern hydronic heating is: One heat source serving multiple loads Those loads include: Radiant heating of floors, walls and ceilings Baseboard heating Panel radiators Hydro-air subsystems Indirect domestic water heating Intermittent garage heating Pool and spa heating Snow melting District heating of several adjacent buildings Agricultural / horticultural loads such as animal enclosures, greenhouse heating, and turf warming Many projects may have several of these loads, each requiring heat in different amounts, at different times and at different temperatures. For example, the space heating loads of a given building might best be served by a combination of hydronic heat emitters. Some areas might be perfect for radiant floor heating while others are better suited to radiant ceiling heating. Still other areas might be ideal for baseboard or even ducted forced-air through an air handler equipped with a hot water coil. Almost every house and commercial building also needs domestic hot water. In some cases, this load can be as large or larger than the space heating load. Many facilities are also perfect candidates for hydronic snow melting - if those in charge are aware of the benefits it offers compared to traditional methods of snow removal. Some designers approach situations like these by proposing a separate, isolated hydronic system for each load. One boiler to heat the building, another to melt the snow in the driveway, and perhaps still another to heat the pool. The same building might also use one or more direct-fired domestic water heaters. Although such an approach is possible, it seldom takes advantage of the unique ability of hydronics to connect all the loads to a single heat source. The latter approach often reduces the size and cost of the overall system. It also makes for easier servicing and reduces fuel consumption. Such a synergistic system is made possible through modern hydronics technology. 8

9 SECTION 1 CONSIDER THE POSSIBILITIES From Simple to Sophisticated and easily mounted unit. All that s left to do is to pipe Let s look at the versatility of modern hydronics technology in meeting the demands of both simple and sophisticated load requirements. We ll start with something basic: a floor heating system for a small addition to a home. Because the load is small, a water heater will be used as the heat source. It, as well as the other system components, is shown in figure 1-1 Figure 1-2 the WarmRite control panel to the water heater, connect the floor circuits, and then route power to it. Although this system is very simple in concept and construction it s also capable of delivering comfort far superior to its alternatives, several of which may cost more to install as well as to operate. Figure 1-1 Although the installer could purchase components (such as the manifolds, a bronze circulator, expansion tank) and all the valving separately, using a WarmRite control panel can save much time and labor. All the needed components are preassembled into a compact A Slightly Larger Requirement A typical home often has a design heating load greater than what can be supplied from a residential water heater, especially if the same unit also has to supply domestic hot water. In such cases a boiler is a more appropriate heat source. Figure 1-3 is an example of a hydronic system that Figure 1-3 9

10 THE IPEX MANUAL OF MODERN HYDRONICS supplies space heating through a radiant floor subsystem as well as domestic hot water via an indirect water heater. Two WarmRite control panels are used to provide the water and electrical control functions for the space heating portion of the system. In this case, electric valve actuators have been included in the WarmRite control panels to allow individual temperature control of several rooms. An external injection mixing system has been installed between the WarmRite control panels and the primary loop, to vary the water temperature supplied to the floor circuits based on outside temperature (e.g. outdoor reset control). This mixing system also protects the boiler from flue gas condensation that can be caused by low return water temperatures. Multiple Water Temperatures...No Problem Some buildings may require (or some customers may prefer) different types of hydronic heat emitters that operate at different water temperatures. For example, a portion of a building may use radiant floor heating. The tubing circuits in the heated floor slab might operate at 105 deg. F. water temperature at design conditions. Another part of the building may be heated with fintube baseboard that needs 180 deg. F. water at the same time. Providing these multiple water temperatures is relatively straightforward using the piping/control scheme depicted in figure 1-4. Notice that the manifold supplying the baseboard circuits is piped directly into the primary loop and thus receives hot (180 deg. F.) water. The floor heating circuits are supplied with reduced water temperature through use of an injection mixing system and the WarmRite control panel. Note that all components related to run the floor heating circuits are integrated into one preassembled WarmRite control panel. The boiler also supplies hot (180 deg. F.) water to the heat exchanger of the indirect water heater for fast recovery. This system now serves three different heating loads using two water temperatures. But that s far from pushing the limits of modern hydronics technology. A Sophisticated System Suppose that after discussing the above system, your customer asks if you can also provide snow melting, occasional garage heating or pool heating. Maybe even all three at the same time. This is an opportunity where Figure

11 SECTION 1 CONSIDER THE POSSIBILITIES hydronics can really come through. It is a situation where you can provide an efficient customized system that s exactly right for your customers needs. Figure 1-5 depicts one way such a system could be assembled. Think of this system as a collection of subassemblies plugged into a common source of heated water: the primary loop. The floor heating subassembly appears the same as in figure 1-4 except now there are two of them. It s simply plugged into larger primary loop. Likewise, the manifold supplying the baseboard zones is plugged into the primary loop the same as in figure 1-4. What s new are the subassemblies that supply the heat exchanger for the snow melting and pool heating systems. Think of the heat exchangers as the separating point between the hot water in the primary loop and the fluids that carry heat to the snow melting circuits and the pool. The heat gets passed from one fluid to the other, but the fluids themselves never mix. The power plant for this sophisticated system is a pair of boilers controlled by a staging control. This concept called a multiple boiler system is now common in larger residential as well as commercial systems. The multiple boiler system is sized to deliver the proper amount of heat when all the loads that are capable of running simultaneously are doing so. Such an approach yields higher seasonal efficiency compared to a single large boiler. It also adds to the system s reliability since one boiler can still operate should the other be down for service. The system shown in figure 1-5 uses state-of-the art piping and control techniques to serve all the heating loads of a large house with many amenities. It also makes use of Kitec and WarmRite hardware to speed installation and ensure top quality. The sections to follow discuss many of the key concepts and available options for assembling both simple and sophisticated hydronic systems. Learn them, apply them, and then take pride in providing your customers with the comfort and efficiency that only modern hydronics technology can deliver. Figure

12 SECTION 2 HEAT SOURCE OPTIONS A wide variety of heat sources can be used with hydronic heating systems. They include gas- and oil-fired boilers, hydronic heat pumps and domestic water heaters to name a few. Some are better suited to higher temperature systems, while others are ideal for low temperature systems. This section briefly describes the characteristics of several heat sources suitable for hydronic systems. More detailed information pertaining to their selection and installation is best found in manufacturer s literature and manuals. Relevant building / mechanical codes should also be consulted for specific installation requirement. The information at the end of this section allows designers to compare the cost of energy provided by several common fuels based on their local cost and the efficiency at which they are converted to heat. 2-1 Conventional Boilers The most common hydronic heat source is a conventional gas- or oil-fired boiler. They are available with heat exchangers made of cast-iron, steel and finned copper tubing. Although designed to operate at relatively high water temperatures, conventional boilers can be adapted to lower temperature hydronic systems such as radiant floor heating by using a mixing device. Their ability to produce high temperature water makes them a good choice in systems where both low temperature and high temperature heat emitters are used. The term conventional describes boilers that are intended to operate without sustained condensation of the flue gases produced during the combustion process inside the boiler. These flue gases are made up of water vapor, carbon dioxide, and trace amounts of other combustion products depending on the fuels used, and the tuning of the burner. All boilers experience temporary flue gas condensation during cold starts. If the boiler is connected to a low mass 13

13 THE IPEX MANUAL OF MODERN HYDRONICS distribution system that is designed to operate at higher water temperatures fin-tube baseboard for example such flue gas condensation is short-lived. It rapidly evaporates as the boiler warms above the dew point of the exhaust gases. However, when a conventional boiler serves as the heat source for a low temperature distribution system it is imperative to keep the inlet temperature to the boiler above the dew point of the exhaust gases. For gas-fired boilers, the inlet water temperature during sustained operation should not be less than 130 deg. F. For oilfired boilers, it should not be less than 150 deg. F. Failure to provide such boiler inlet temperature protection will cause the water vapor (and other compounds present in the exhaust gases) to continually condense on the internal heat exchanger surfaces. The acidic nature of such condensate can cause swift and severe corrosion along with scale formation inside the boiler. It can also rapidly corrode galvanized vent piping, as well as the deterioration of masonry chimneys Hydronic distribution systems with high thermal mass can also cause prolonged flue gas condensation as the system warms up to normal operating temperature. A cool concrete slab with embedded tubing circuits is a good example. As the slab begins to warm, its thermal mass can extract heat from the circulating water stream 3 to 4 times faster than normal. Since the rate of heat release from the water is much higher than the rate of heat production, the water temperature (in an unprotected boiler) will quickly drop well below the dew point temperature of the exhaust gases. The boiler can operate for hours with sustained flue gas condensation. Such a situation must be avoided. The key to avoiding low boiler inlet water temperature is preventing the distribution system whatever type it happens to be from extracting heat from the water faster than the boiler can produce heat. Modern mixing devices can automatically monitor and adjust boiler return temperature by limiting the rate of heat transfer allowed to pass through a mixing device and into the distribution system. The piping concept is shown in figure 2-1. The details involved in providing boiler return temperature protection will be discussed in section Condensing Boilers In contrast to conventional boilers, gas-fired condensing boilers are specifically designed to promote condensation of the water vapor that is produced during combustion. They use large internal heat exchanger surfaces to coax as much heat as possible from the exhaust gases. The heat exchanger surfaces are made of high-grade stainless steel or other special alloys, and are not corroded by the acidic condensate that forms as the flue gases cool below the dew point. When properly applied in low temperature hydronic systems, such boilers can attain efficiency of 95+ %. Although they are more complicated and more expensive than most conventional boilers, condensing boilers are well suited for low temperature hydronic systems such as slab-type floor heating, snow melting, pool heating and low- to medium- temperature domestic water heating. The lower the temperature of the water returning from the distribution system, the greater the rate of condensate formation, and the higher the boiler s efficiency. Although condensing boilers can be used as heat sources for higher temperature hydronic systems, this is generally not advisable. The higher operating water temperatures prevent the boiler from operating with sustained flue gas condensation. Under such conditions their efficiency is comparable to that of a conventional boiler. Again, the key to attaining high efficiency from a condensing boiler is matching it with a lowtemperature distribution system. Systems with condensing boilers typically do NOT use mixing devices between the boiler and the distribution Figure 2-1 Figure

14 SECTION 2 HEAT SOURCE OPTIONS system. This helps offset a portion of the boiler s higher cost. Most condensing boilers can also be side wall vented through a 2 CPVC pipe. This too lowers installation cost relative to boilers vented through a chimney. Figure 2-2 shows how a condensing boiler would be piped in a typical floor heating system. 2-3 Tank-type Water Heaters Some hydronic systems can use tank-type domestic water heaters as their heat source. Usually the size of such systems is limited by the heating capacity of the water heater. Residential water heaters have heat outputs in the range of 15,000 to 40,000 Btu/hr. This usually limits their application to small apartments or modest residential additions. Figure 2-3 Because tank-type water heaters are designed to operate at lower water temperatures, mixing devices are not usually used between the tank and the distribution system. The tank is directly piped to the distribution system as shown in figure 2-3. The tank s thermostat is set for the desired supply water temperature. In some systems a water heater is expected to supply both domestic hot water and space heating. Although possible under some circumstances, the designer must ensure that the heating capacity of the water heater can handle both the space heating and domestic water heating loads. If these loads occur simultaneously, it is usually necessary to make the domestic water heating load a priority over the space heating load. Temperature controls can be used to temporarily suspend heat output to the space heating system until the domestic water heating load subsides and the tank temperature recovers. Opinions vary on the suitability of circulating potable water through the space heating circuits. Under some circumstances, the potable water can remain stagnant in the space heating circuits for several months allowing for the possibility of microbe growth. Because potable water is used in the space heating circuits, all metal components must be bronze or stainless steel to resist corrosion from the oxygen-rich water. There is also the possibility of scale or sediment in the space heating system due to contaminants in the potable water. The preferred approach to such dual use systems is to separate the space heating portions of the system from those containing domestic water using a small stainless steel heat exchanger as shown in figure 2-4. Because the heat exchanger isolates the space heating components the distribution system must have an expansion tank, pressure relief valve and air separator. Figure

15 THE IPEX MANUAL OF MODERN HYDRONICS 2-4 Geothermal Heat Pumps Geothermal heat pumps are one of the newest heat sources suitable for some types of hydronic heating systems. They extract low temperature heat from a tubing circuit buried in the earth, or directly from water wells or other sources of water such as a large pond or lake. Using a refrigeration system similar to that in a central air conditioner, the heat captured from the earth is boosted in temperature and then transferred to a stream of water flowing to the distribution system. As with condensing boilers, no mixing device is required between the heat pump and the distribution circuits. However, if the distribution system is divided into several independently controlled zones, an insulated buffer tank should be installed between the heat pump and the distribution system as shown in figure 2-5. This tank allows the heat output rate of the heat pump to be different than the heat extraction rate of the distribution system. It prevents the heat pump from short cycling under low load conditions. As with condensing boilers, geothermal heat pumps attain their highest efficiency when matched to lowtemperature distribution systems. Slab type radiant floor heating systems operating at water temperatures in the range of 100 to 115 deg. F. at design conditions are ideal. The lower the water temperature, the higher the heat pump efficiency the system can operate at. Avoid geothermal heat pumps in systems requiring design water temperatures above 130 deg. F. In addition to heating, geothermal heat pumps can also supply chilled water for hydronic cooling applications. The most common approach uses an air handler equipped with a chilled water coil. Other terminal units such as radiant ceiling panels can be used for chilled water cooling, but such systems require accurate and reliable dew point control to avoid condensation on the chilled surfaces. A separate air handler is usually required to control humidity. Figure

16 SECTION 2 HEAT SOURCE OPTIONS 2-5 Thermal Energy Storage Systems Many electric utilities offer off-peak electrical rates. Power that is purchased during off-peak hours is usually much less expensive than during periods of high demand. A hydronic heating system is an excellent means of taking advantage of these rates. The idea is to purchase the electricity during the off-peak period and store the energy as heated water. This water is then used to heat the building during the on-peaks periods when electrical rates are higher. A schematic showing how this concept can be implemented is shown in figure 2-6. The beginning of an off-peak charging cycle is initiated by a switch contact in the electric meter. At this point, one or more electrical heating elements are turned on to heat water in the large, well-insulated storage tank. Charging continues for several hours, and the tank become progressively hotter. If heat is needed by the building during the charging cycle, some of the tank water is routed out through the distribution system the same as any other time of day. By the end of the charging cycle the water temperature in the tank may be as high as 200 deg. F. When the switch contact in the meter opens, the electrical elements are turned off. The hot water in the tank contains the heat needed for most if not all of the on-peak hours to follow. Low temperature distribution systems such as radiant floor heating are ideally suited to such a heat source. Their low operating temperature allows the tank to be deeply discharged and thus maximizes its heat storage capability. The heat stored in a heated floor slab also allows the system to coast through the last 2 to 4 hours of the on-peak period should the energy in the tank be depleted. A mixing device installed between the storage tank and the distribution system automatically reduces the water temperature supplied to the distribution system as necessary. Figure

17 THE IPEX MANUAL OF MODERN HYDRONICS 2-6 Wood-fired Boilers When firewood is readily available and competitive in cost with conventional fuels, wood-fired boilers are another possible hydronic heat source. In some systems, a wood-fired boiler is used in tandem with a conventional fuel boiler. The piping concept is shown in figure 2-7. Each boiler is piped as a secondary circuit into a common primary piping loop. This arrangement allows either boiler to operate without circulating hot water through the other (unfired) boiler, thus reducing heat loss. System controls are usually configured so the conventional fuel boiler automatically assumes the load as the fire dies down in the wood-fired boiler. Heat output from a wood-fired boiler is harder to control than that from a conventional boiler. A large volume of water in the system adds to its stability. The water volume may be contained in the wood-fired boiler itself or in a separate insulated thermal storage tank. Such a tank must be well insulated so that it can store heat for several hours with minimal losses. The concept is also shown in figure 2-7. Some wood-fired boilers are not pressure rated. The water chambers inside the boiler are vented directly to the atmosphere. Although opinions vary on how best to connect such open system boilers to hydronic distribution systems the conservative approach is to install a stainless steel heat exchanger to isolate the boiler water from that in the pressurized distribution system. Not only does this allow the distribution system to be pressurized for quiet, air-free operation, but it also protects the cast iron and steel components in the distribution system from the possibility of corrosion through contact with boiler water that has a higher concentration of dissolved oxygen. Figure

18 SECTION 2 HEAT SOURCE OPTIONS 2-7 Comparing Fuel Costs In many cases the heat source is selected based on the type of fuel that is available or determined to be most economical over the life of the system. The commonly used fuels are sold in different units such as kilowatthours for electricity, therms for natural gas, gallons for fuel oil and face cords for firewood. To perform an accurate comparison it is necessary to express the cost and energy content of each candidate fuel on a common basis. The formulas in figure 2-8 allow the cost of heating energy from each of several fuels to be expressed on the common basis of dollars per million Btu s of delivered heat. This is abbreviated as $/MMBtu. These formulas take into account the cost, purchase units, as well as efficiency of the heat source in converting the fuel into useful heat. Figure

19 SECTION 3 WATER TEMPERATURE CONTROL All hydronic heating systems must control the water temperature supplied to their heat emitters. A simple system may only need to supply one water temperature to all the loads it serves. A more sophisticated system containing several types of heat emitters may need to simultaneously supply two or more water temperatures. This section discusses several methods of water temperature control and the hardware necessary to accomplish it. 3-1 Setpoint control The simplest method of water temperature control is called setpoint control. As its name implies, a single (set) water temperature is supplied to the distribution system regardless of which loads are active, or how great the demand for heat is (as long as there is a demand). To prevent short cycling of the heat source or other equipment in the system, setpoint controls require an operating differential. This refers to the variation in temperature between which control closes or opens its electrical contacts. A contact closure is the most common way to turn the heat source on and off. For example, a setpoint control with a setting of 180 deg. F. and a differential of 10 deg. F. would turn the heat source off at 180 deg. F. and back on when it the temperature drops to 170 deg. F. Some setpoint controls center their differential on the setpoint. A device of this type, when set to 180 deg. F. and a 10 deg. F. differential, would open its electrical contacts to turn the heat Figure

20 THE IPEX MANUAL OF MODERN HYDRONICS source off at 185 deg. F. and close them when the sensed temperature drops to 175 deg. F. Figure 3-1 compares these two types of setpoint control. Some setpoint controls have fixed (non-adjustable) differentials, while others provide an adjustable differential. The narrower the differential, the closer the water temperature stays to the desired setpoint. However if the differential is too narrow, the heat source or other equipment in the system could experience excessively short operating cycles that reduce their efficiency and shorten their life. Heat source operating differentials in the range of 10 deg. F. are common in hydronic systems. Systems using setpoint controls provide the same average water temperature to the loads whenever there is a call for heat, regardless of the rate of heat input required by the load. For example, a boiler operated by a setpoint control supplying a circuit of fin-tube baseboard would deliver hot water (perhaps averaging around 175 deg. F.) whether the outdoor temperature was -10 deg. F. on a cold January night, or 50 deg. F. on a mild October afternoon. To prevent overheating under all but design load conditions, flow must be periodically interrupted by turning off the circulator or closing the zone valves. To keep room temperature variations to a minimum, it s important to have a thermostat with a narrow differential of perhaps 1 or 2 deg. F. If the thermostat has an anticipator it should be carefully set for the electrical current flow through it during its on-cycle. They are: 1. boiler reset control 2. mixing reset control A boiler reset control takes over operation of the burner from the standard (fixed) high limit control supplied with most boilers. As the outside air temperature changes, the reset control continually recalculates how high the boiler water temperature will be allowed to climb and operates the burner accordingly. Boiler reset is well suited for systems using relatively high temperature hydronic heat emitters, like baseboard or panel radiators. However, because conventional boilers should not operated for prolonged periods at temperatures below the dew point of their exhaust gases, boiler reset is limited when used in conjunction with low temperature heat emitters. In such cases, boiler water temperature can only partially reset down to a user-selected minimum temperature setting as shown in figure Outdoor reset control Rather than deliver heat in spurts, an ideal system would continually adjust its rate of heat delivery to match the heat loss of the building. The indoor air temperature would remain constant, and there would be no difference in comfort regardless of outside conditions. Outdoor reset control (ORC) was developed for this purpose. It enables heat to flow from the heat emitters to the space being heated at just the right rate. ORC is increasingly recognized as the preferred method of water temperature control, especially for high thermal mass floor heating systems. All outdoor reset controls use outside air temperature to determine the ideal target water temperature to be supplied to the system s heat emitters. The colder it is outside, the higher the water temperature. The goal is to match the rate of heat delivery to the rate of heat loss from the building. There are two methods of using reset control in a hydronic system. Each can be used by itself, or the two can be used in combination. Figure 3-2 For the case shown, the boiler outlet temperature would not be reduced below 140 deg. F. This water temperature happens to correspond to an outside air temperature of 25 deg. F. Air temperatures of 25 deg. F. and higher represent a large percentage of the heating season in many parts of North America. This implies the 140 deg. F. water temperature supplied to the heat emitters will be higher than necessary during much of the heating season. The room thermostat must turn the circulator (or zone valve) on and off to prevent overheating under these conditions. 22

21 SECTION 3 WATER TEMPERATURE CONTROL Figure 3-3 Mixing reset control requires a mixing assembly between the boiler loop and a separate distribution circuit. This assembly could contain a modulating 2- way, 3-way, or 4-way valve, or a variable speed injection pump as depicted in figure 3-3. These options are discussed in more detail later in this section. The mixing assembly provides the proper supply water temperature to the distribution system. When necessary, it also acts as a clutch to prevent the cold thermal mass of a distribution system from extracting heat faster than the boiler can produce it. This latter function, commonly called boiler protection, is crucially important when a conventional boiler provides heat to a slab-type floor heating system. Mixing reset control allows deep reduction in the water temperature supplied to the distribution system while simultaneously protecting the boiler from low inlet water temperatures. Boiler reset can be used in combination with mixing reset in the same system. The concept is shown in figure 3-4. The boiler reset control monitors and adjusts the water temperature in the primary loop by varying the firing cycles of the boiler(s). The primary loop temperature is often partially reset to prevent the boiler(s) from operating below dew point temperature. The mixing reset control operates the mixing device to reduce the primary loop water temperature as appropriate for the loads they serve. Some systems may have two or more independent mixing devices supplied from a common primary loop. Figure

22 THE IPEX MANUAL OF MODERN HYDRONICS An example of the reset lines for a system using both boiler reset and mixing reset is given in figure 3-5. Notice that the primary loop has a minimum supply temperature of 140 to protect the boiler from sustained flue gas condensation. However, the mixing reset control can reduce the temperature of the water to the distribution system all the way down to room air temperature. 3-3 Mixing requirements Several types of mixing devices can be used to reduce the water temperature supplied from the heat source to the distribution system. These include 2-way, 3-way, and 4-way valves as well as several forms of injection mixing. Controlling the water temperature supplied to the distribution system is often not the only function of the mixing device. In systems using a conventional boiler as the heat source the mixing device must also prevent low inlet water temperatures that can cause sustained flue gas condensation within the boiler. This second requirement applies when any type of fuelburning boiler that s not designed to operate with sustained flue gas condensation is paired with a low temperature distribution system. Most conventional gas- and oil-fired boilers fall into this category. Failure to provide this protection can result in severe corrosion and scaling within the boiler. This not only shortens boiler life, but it can also lead to failure of vent piping and spillage of combustion products into the building. Unfortunately, the need to protect the boiler inlet temperature is often viewed as secondary to providing the proper supply temperature to the distribution system. This is an oversight with potentially deadly consequences. It is generally recognized that maintaining return temperatures of 130 deg. F. or higher for gas-fired boilers, and 150 deg. F. or higher for oil-fired boilers will eliminate the damaging effects of flue-gas condensation. There are exceptions, and boiler manufacturers should be consulted regarding the minimum operating temperature of their equipment. Condensing boilers, discussed in section 5, are specifically designed to withstand sustained flue gas condensation and don t need return temperature protection. The cooler the return water temperature the higher their efficiency. In most cases a mixing device is not needed when a condensing boiler is used to supply heat to a low temperature hydronic distribution system as long as the supply temperature matches the design criteria. Figure

23 SECTION 3 WATER TEMPERATURE CONTROL Hydronic heat sources that don t produce flue gases don t need to be protected against flue gas condensation. These include electric boilers, hydronic heat pumps, thermal storage tanks, and heat exchangers way thermostatic mixing valves One of the most common mixing devices used in low temperature hydronic systems is a 3-way thermostatic valve. It has two inlet ports one for hot water, the other for cold and a single outlet port for the mixed stream. Inside the valve is a shuttle mechanism that determines the proportions of hot and cold water allowed into the valve. The shuttle is moved up and down inside the valve body by the expansion and contraction of a wax-filled actuator. The sealed wax assembly is heated by the mixed flow across it. If the mixing stream is slightly too hot, the wax assembly expands, forcing the shuttle to partially close the hot inlet port and simultaneously open the cold inlet port. A knob on the valve sets the actuator to the desired outlet water temperature. As the temperatures of the incoming hot and cold streams change, the wax-filled actuator moves the shuttle to maintain the set outlet water temperature. Some 3-way mixing valves are operated by a gas-filled bellows actuator rather than an internal wax-filled actuator. Their sensing bulb contains a fluid that increases in pressure when heated. This increased pressure causes the valve to partially close the hot water port as it opens the cold water port. A knob on the valve is used to set the desired mixed water temperature. The preferred location of the temperature-sensing bulb is downstream of the distribution loop circulator. This ensures thorough mixing by the time the flow passes by the sensing bulb. Improper placement of the sensing bulb can cause erratic operation. The most accurate temperature sensing takes place with the sensing bulb is immersed in the flowing water. If this is not possible the bulb should be tightly strapped to the pipe and covered with pipe insulation. The piping schematics in figure 3-6 show one piping arrangement for a 3-way valve. This piping arrangement is appropriate if (and only if) low inlet water temperatures or reduced flow rates under low load conditions do not adversely effect the heat source. Reduced boiler flow rate is seldom a problem for high mass boilers or storage tanks. However, low mass boilers, heat pumps or electric boilers may require a minimum flow rate whenever they operate. In such Figure

24 THE IPEX MANUAL OF MODERN HYDRONICS cases, the heat source should be equipped with its own pumped bypass circuit as shown in figure 3-7. With this arrangement, flow through the heat source does Figure 3-7 not change regardless of the flow proportions through the 3-way valve. Connections from the bypass circuit to the remaining piping system are made using primary secondary tees to prevent interference between the two circulators. 3-way thermostatic valves supply the distribution system with a fixed water temperature regardless of the heating load. Under partial load conditions, the system will overheat the building unless flow through the heat emitters is interrupted when the desired room temperature is attained. A single 3-way thermostatic mixing valve that controls water temperature to the distribution system does NOT protect a conventional boiler from flue gas condensation. Figure 3-7 shows that a portion of water returning from the distribution system goes directly back to the boiler. When the distribution system operates at low temperatures, this return water will cause sustained flue gas condensation in the boiler. This must be avoided. One way to protect a conventional boiler from sustained flue gas condensation is to install a second 3-way thermostatic mixing valve as shown in figure 3-8. The additional valve monitors return temperature, and if necessary, mixes hot water from the boiler with cool return water from the return side of the primary loop to boost water temperature entering the boiler. Some manufacturers even build this thermostatic valve into their boilers. Figure

25 SECTION 3 WATER TEMPERATURE CONTROL way motorized mixing valves 3-way valve bodies can also be paired with precision motorized actuators. An electronic controller regulates such actuators. The resulting motorized valve system can supply either fixed or variable water temperatures to a radiant panel. The valve body used for this type of mixing system is often different from that used for a 3-way thermostatic valve. It has a rotating (as opposed to linear motion) shaft. As the shaft rotates through approximately 90 degrees of arc, the internal spool simultaneously opens one inlet port and closes the other. This regulates the proportions of hot and cold water entering the valve, and thus determines the mixed outlet temperature. The actuating motor turns the valve shaft very slowly. Rotating the shaft through 90 degrees of arc may take 2 to 3 minutes. This slow rotation is not a problem given the slow response of many high mass distribution systems. It actually helps stabilize the system against overshooting or undershooting the target water temperature. A temperature sensor attached to the piping leading to the distribution system measures the mixed water temperature leaving the valve. It provides feedback to an electronic controller that regulates the valve motor. If the temperature is exactly where it should be, the motor does not change the valve s stem position. If the supply temperature is slightly low, the motor very slowly rotates the valve stem to allow more hot water to enter the mix and vice versa. Since the sensor is downstream of the valve s outlet port, it provides constant feedback to the controller allowing it to fine tune water temperature. The piping for a 3-way motorized valve is shown in figure 3-9. Note the use of a boiler loop with a pair of closelyspaced tees to interface to the distribution system. This accomplishes two important functions. First, it prevents the boiler loop circulator from interfering within the flow through the 3-way valve. Second, it provides another mixing point (shown as point B) allowing hot water in the boiler loop to mix with cool water returning from the distribution system before entering the boiler. The controller operating the valve motor senses both system supply and boiler return temperature. When necessary, the controller can partially close the hot port of the 3-way valve to prevent the distribution system from extracting heat faster than the boiler can produce it. This allows a single 3-way motorized valve to control both the supply temperature, and protect the boiler form low inlet temperature. Most controllers used for mixing valves are able to provide either setpoint or outdoor reset control. The latter cannot be accomplished (automatically) with 3- way thermostatic valves. A single 3-way motorized valve piped and controlled as described provides more versatility than does a pair of 3-way thermostatic valves. Figure

26 THE IPEX MANUAL OF MODERN HYDRONICS way motorized mixing valves Another mixing device that has seen extensive usage in systems pairing a conventional boiler and low temperature distribution system is a 4-way motorized mixing valve. These valves were designed to provide both supply temperature control and boiler return temperature boosting. Figure 3-10 shows a cross section of a typical 4-way valve body. Figure 3-10 Hot water from the boiler is mixed with cool return water from the distribution system at two locations inside a 4-way valve. In the upper mixing chamber, the hot and cool water streams mix to form the stream supplied to the distribution system. At the same time, mixing also occurs in the lower valve chamber. Here the objective is to boost the temperature of the water returning to the boiler. As with motorized 3-way valve systems, a temperature sensor mounted on the supply pipe to the distribution system provides feedback to the valve controller. Another temperature sensor mounted near the boiler return allows the controller to monitor boiler inlet temperature. When necessary, the controller would partially close the hot inlet port to the valve to prevent the distribution system from extracting heat faster than the boiler can produce it. The recommended piping for a 4-way mixing valve is shown in figure Closely- spaced tees are used to connect the valve to the boiler loop. This prevents flow interference between the boiler circulator and distribution circulator. The valve draws hot water from the boiler loop using the momentum of the flow returning from the distribution system. The boiler loop also ensures adequate flow through the boiler under all conditions. It s important to understand that merely using a 4-way mixing valve body in a system does NOT guarantee that the distribution system will receive the proper supply temperature. Neither does it guarantee the boiler is protected from low inlet water temperatures. For proper control, the valve must react to both the supply and boiler return temperatures. To do so, it must be Figure

27 SECTION 3 WATER TEMPERATURE CONTROL directed by a controller that senses both supply and return temperature. It s pointless to install a 4-way valve body while omitting the actuator / controller it needs for proper operation. 3-7 Injection Mixing (the concept) Injection mixing is one of the simplest yet most versatile methods of controlling the water temperature in a hydronic distribution system. The concept is shown in figure Hot water from the boiler loop is pushed through a pipe called an injection riser. It enters the side port of a tee at point (A) where it mixes with cool water returning from the distribution system. The blending of these two streams determines the supply temperature to the secondary circuit. The greater the flow rate of hot water entering the tee, the warmer the distribution system gets and the greater its heat output. Injection mixing is ideal for systems pairing a conventional boiler to a low temperature distribution system. The large temperature difference ( T) between the incoming hot water and the outgoing return water allows a high rate of heat transfer using a minimal injection flow rate. 3-8 Injection mixing using a 2-way valve Figure 3-12 One of the devices used for injection mixing control is a modulating 2-way valve. Either a non-electric thermostatic actuator or motorized actuator operates the valve. The piping concept is shown in figure Hot water from the boiler loop is drawn into the supply injection riser at point B. It passes through the injection control valve and enters the side port of a tee at point C where it mixes with cool return water from the distribution system. The flow rate through the injection risers depends on the stem position of the injection control valve, as well as the flow restrictor valve s setting. The greater the injection flow rate, the Figure

28 THE IPEX MANUAL OF MODERN HYDRONICS Figure 3-14 higher the water temperature supplied to the distribution system and the greater its heat output. In a typical low temperature floor heating system supplied by a conventional boiler, the flow rate through the injection control valve is about 15 to 20% of the flow rate in the distribution system. This allows a relatively small modulating injection valve to regulate a large rate of heat transfer. When a motorized valve operated by an electronic controller is used, boiler protection is accomplished by monitoring the boiler inlet temperature and partially closing the injection valve when necessary to prevent the distribution system from absorbing heat faster than the boiler can produce it. Unlike a motorized valve with a smart controller, a single thermostatic 2-way modulating valve cannot control both the supply temperature to the distribution system and the inlet temperature to the boiler. To protect the boiler, it is necessary to use another mixing device that can monitor and adjust the boiler inlet temperature when necessary. Figure 3-14 shows the use of a 3 way thermostatic valve for this purpose. When using a 2-way valve for injection mixing, be sure the tees at points A and B in figure 3-13 are as close as possible. Also be sure there s a vertical drop of at least 18 inches between where the return injection riser connects to the boiler loop and where it connects to the distribution system. This drop forms a thermal trap to reduce heat migration into the distribution system when no heat input is needed. It is important to select the injection control valve based on its Cv rating, NOT the size of the injection riser piping. Oversized injection valves will not produce smooth heat input control under low load conditions. Undersized injection valves will cause excessive head loss and may not be able to deliver design load heat transfer rates. Before selecting the injection control valve, calculate the necessary injection flow rate under design load conditions using the following formula: Formula 3-1 Where: f i = Q 500 x (T 1 _ T2 ) fi = required design injection flow rate at design load (in gpm) Q = Heat input to distribution at design load conditions (in Btu/hr) T1 = water temperature being injected (in deg. F.) T2 = water temperature returning form distribution system (in deg. F.) 500 = a constant for water (use 479 for 30% glycol, 450 for 50% glycol) Select an injection control valve with a Cv factor approximately equal to the injection flow rate just calculated. 30

29 SECTION 3 WATER TEMPERATURE CONTROL Once the system is operational, set the flow restrictor valve so the injection control valve remains fully open at design load conditions. This allows the valve to operate over its full range of stem travel as heat input to the distribution system varies from zero to full design load. 3-9 Injection mixing using a variable speed pump Another method of injection mixing uses a small wet rotor circulator operated at variable speeds as the injection device. The piping concept is shown in figure Hot water from the boiler loop is drawn into the supply injection riser at point B. It enters the side port of a tee at point C, where it mixes with cool water returning from the distribution system. An equal flow rate of cool return water flows back from the distribution system to the primary circuit through the other riser. The flow rate of hot water passing through the supply riser is controlled by the speed of the injection pump. The faster the pump runs, the faster hot water flows into the distribution system and the greater its heat output. In a typical low temperature floor heating system supplied by a conventional boiler, the flow rate through the injection pump is about 15 to 20% of the flow rate in the secondary circuit. This allows a relatively small injection pump to control a large rate of heat transfer. The injection mixing control also protects the boiler by monitoring the inlet temperature and reducing the speed of the injection pump when necessary to prevent the distribution system from absorbing heat faster than the boiler can produce it. When using variable speed injection mixing, be sure the tees at points A and B in figure 3-15 are as close together as possible. Also be sure there is a vertical drop of at least 18 inches between the (return) injection riser connection to the primary circuit and its connection to the secondary circuit. This drop forms a thermal trap to reduce heat migration into the distribution system when no heat input is needed. In a properly balanced system, the injection pump should run at full speed when the system is operating at design load conditions. Achieving this balance requires adjustment of the balancing valve located in the return injection riser. There are several ways to set this valve. One of the easier ways is to use a valve that has built-in measuring capability. Many circuit-setter type valves are available for this purpose. To properly set the circuit setter valve, it s necessary to calculate the required injection flow rate under design load conditions using formula 3-1. With the injection pump running at full speed, partially close the circuit setter valve until it indicates a flow equal to the value calculated. Figure

30 SECTION 4 RADIANT FLOOR HEATING METHODS The availability of modern materials such as Kitec pipe has allowed the market for hydronic radiant floor heating to increase approximately ten fold over the last decade. Installation methods have been developed for many types of floor constructions in residential, commercial and industrial buildings. Each year these installation techniques allow thousands of buildings to be equipped with what many consider to be the ultimate comfort heating system. 4-1 What is radiant heating? Before discussing the installation details of radiant floor heating, it s important to have a clear understanding of how radiant heating works as well as how it differs from other forms of heating. Nature has three means of transferring heat from objects at a given temperature to objects at lower temperatures. Conduction is how heat moves through solid materials, or from one solid material to another when the two are in contact. If you stand barefooted on a cool basement floor slab, heat transfers from your feet to the floor by conduction. Convection is how heat moves between a solid surface and a fluid. The fluid may be either a liquid or a gas. Hot water flowing through a pipe transfers heat to the inside wall of the pipe by convection. Likewise, air flowing across the heat exchanger inside a furnace absorbs heat from the hot metal surfaces. Radiant heat transfer occurs when infrared light leaves the surface of an object and travels to the surface(s) of other cooler objects. Unlike conduction and convection, radiant heat transfer does not require a fluid or solid material between the two objects transferring heating. It only requires a space between the two objects. Solar energy travels approximately 93 million miles from the sun to the earth, through the emptiness of space, solely as radiant energy. The radiant energy only becomes sensible heat when absorbed by a surface. 33

31 THE IPEX MANUAL OF MODERN HYDRONICS The radiant energy emitted by the relatively low temperature heat emitters used in hydronic heating is technically described as infrared electromagnetic radiation. It s simply light that the human eye can t see. However, other than the fact that it s invisible, infrared light behaves just like visible light. It travels in straight lines at the speed of light (186,000 miles per second), and can be partially reflected by polished metallic surfaces. Unlike warm air, radiant energy travels equally well in any direction. Up, down or sideways, direction simply doesn t matter. This characteristic allows a heated ceiling to deliver radiant heat to the room below. The radiant energy emitted by a warm floor, wall or ceiling is a completely natural phenomenon that s literally as old as the universe itself. A surface warmed by sunlight gives off infrared radiation just like one warmed by embedded tubing. The latter simply uses a different heat source and transport system to deliver heat to the surface. Most low temperature radiant panels emit less than 1/10 the radiant flux of bright sunlight, and all of it is infrared as opposed to ultraviolet light. Even the human body gives off infrared radiation to cooler surrounding surfaces. 4-2 The Benefits of Hydronic Radiant Floor Heating Radiant floor heating is considered by many as the ultimate form of comfort heating. In addition to the advantages of hydronic heating in general, warm floors provide benefits that virtually no other system can match. Any one of these benefits can become the hot button that convinces a discriminating customer to install a hydronic radiant floor heating system. Here s a summary of these key benefits. Unsurpassed thermal comfort: Buildings equipped with radiant flooring have interior environments that are highly favorable to human thermal comfort. Unlike many systems that directly heat the air, radiant floor heating gently warms the surfaces of objects in the room as well as the air itself. The warm surfaces significantly reduce the rate of heat loss from the occupants, allowing most to feel comfortable at room temperatures 3 to 5 deg. F. lower than with other methods of heating. The air temperature at floor level is slightly higher than the average room temperature. This significantly reduces the rate of heat loss from the feet and legs. Several feet above the floor, the air temperature begins to decrease. Most people tend to feel more alert with slightly lower air temperatures at head level. The lowest air temperatures in the room typically occur just below the ceiling. The result is reduced heat loss through the ceiling insulation and hence lower heating costs. A system that s out of sight: Most people realize that just about every occupied building in North America needs a heating system. However, few enjoy looking at the heat emitters that are a necessary part of that system. The fact that such heat emitters often restrict furniture placement further adds to their invasiveness. With hydronic radiant floor heating, the floor surface is the heat emitter. There s no need to compromise the aesthetics of the space or restrict furniture placement. It s a system that gives your clients a building interior that s as thermally luxurious as it is aesthetically elegant. A quiet system: One of the strengths of hydronic heating is its ability to deliver heat without delivering noise. A properly designed radiant floor heating system is the epitome of silence. The gas or oil burner on the boiler is often the only component that makes any detectable noise, and it s usually located in the mechanical room away from the occupied spaces. A clean system: One of the biggest complaints associated with forced air heating is its tendency to distribute dust, odors and germs throughout a house. In contrast to whole house air movement, hydronic flooring heating creates very gentle (imperceptible) room air circulation. Many people who suffer from allergies have found that radiant floor heating doesn t aggravate the symptoms the way a forced air system often does. A durable system: A slab type floor heating system is nearly as indestructible as the slab itself. It s the ideal way to heat garage facilities, industrial buildings, recreation rooms or other buildings with high interior traffic. A system that reduces fuel usage: Hydronic floor heating systems have a proven record of reduced energy usage relative to other forms of heating, both in residential and commercial / industrial buildings. The savings result from several factors such as the ability to sustain comfort at lower indoor air temperatures, reduced air temperature stratification, non-pressurization of rooms (which leads to higher rates of air leakage), and the ability to operate with lower water temperatures. Savings vary from one building to the next. Although some projects have shown savings in excess of 50%, a more conservative estimate is 10 to 20% in savings. As energy costs continue to escalate, the ability to 34

32 SECTION 4 RADIANT FLOOR HEATING METHODS reduce fuel consumption will play an increasingly important role in how heating systems are selected. Hydronic radiant floor heating can keep energy costs to a minimum while also delivering exceptional comfort. It s truly the benchmark system against which all other methods of heating will be compared. 4-3 The History of Hydronic Radiant Floor Heating The origins of hydronic radiant floor heating date back to the early 1900s when systems were installed using wrought iron and steel piping. During the 1940s and 50 s, many radiant floor heating systems were installed by embedding copper tubing in concrete slabs. Although the installations were somewhat crude in comparison to today, these early systems quickly proved they could deliver unsurpassed comfort. Some of these early systems are still in operation. However, others have long since been abandoned due to fatigue or corrosion of the embedded metal tubing. Although the comfort they delivered was exceptional, too many of the early systems using embedded copper, steel or iron pipe eventually developed leaks. Consumer confidence in the thought that a hydronic floor heating system could provide both comfort as well as a long, trouble-free service life steadily declined. The debut of central air conditioning in the late 50 s, along with strong promotion of forced air (ducted) systems as a preferred means of delivering both heating and cooling all but eliminated the use of hydronic floor heating. Or so it seemed. Ironically, as the hydronic floor heating market was nearing extinction in North America, a new tubing material was being developed in Western Europe. That material was cross-linked polyethylene (or PEX). It would soon prove to be the single biggest factor underlying the reemergence of hydronic floor heating in North America. Europeans had amassed considerable experience with PEX and PEX-AL-PEX tubing in floor heating applications by the time these products made their first appearances on the North American market in the early 1980 s. Slowly but surely these modern piping materials demonstrated they could deliver comfort, easy installation and long life. The rest as they say is history. Today consumers are learning about new methods for installation of hydronic floor heating as never before. They are seeking qualified professional installers and quality products. Kitec pipe and WarmRite accessories let you give these discriminating consumers exactly what they re looking for. Read on to see all the different ways these systems can be installed. 4-4 Slab on Grade Systems As the past has demonstrated, concrete slab-on-grade floors are ideal for hydronic floor heating. The number of buildings with this type of floor construction is huge. It includes a significant percentage of single family houses as well as a large percentage of commercial buildings. Some of the best floor heating opportunities are in garage facilities such as automotive service centers, town highway garages, fire stations and aircraft hangers. These buildings almost always have uncovered concrete floors, and benefit tremendously from the warm, dry floors that hydronic floor heating can provide. finished flooring adhesive concrete slab pipe wire mesh insulation vapor barrier foundation compacted fill CONCRETE SLAB ON GRADE with under slab insulation 35

33 THE IPEX MANUAL OF MODERN HYDRONICS finished flooring adhesive pipe max. 2" from surface wire mesh concrete slab "chair" vapor barrier foundation compacted fill CONCRETE SLAB ON GRADE with no under slab insulation Installation Procedure: Figure 4-1 shows a cut-away view of a modern heated slab-on-grade floor. The installation of a heated floor slab begins by verifying the subgrade has been properly leveled and compacted. Although the heating system installer is probably not responsible for this aspect of Figure

34 SECTION 4 RADIANT FLOOR HEATING METHODS construction, failing to check for proper subgrade preparation could eventually compromise the embedded tubing circuits. It could also leave the installer having to defend why the floor heating system isn t at least partly responsible for cracks in the slab or other defects. After the subgrade has been prepared, the soil vapor barrier and underslab insulation should be installed. Some building specifications may not call for an underslab vapor barrier. However, its ability to resist moisture migration from the underlying soils can be indispensable, especially when wood products are used as the finish flooring. Heat loss from the edge and underside of a heated slab on grade can be substantial, especially in areas with high water tables or where the slab rests on bedrock. Edge and underslab insulation are essential in reducing these losses. They are a necessary part of any quality floor heating system. Not taking steps to mitigate such heat loss is like leaving the windows open throughout the winter. Realistically there s only one opportunity to install underslab insulation before the slab is poured. Discovering high downward heat loss after the system is in operation is a situation that s virtually impossible to correct. It makes little sense to attempt the installation of a high quality heating system while omitting crucial and relatively low cost details. Do it right the first time. The most commonly used material for slab edge and underside insulation is extruded polystyrene. It s sold in 2 by 8 foot and 4 by 8 foot sheets in several thicknesses. It s also available in several densities to handle different floor loading. Extruded polystyrene panels are highly resistant to moisture absorption, and have a well-established record in ground contact insulation applications. New insulating materials are developed to promote the use of under slab insulation. One of them is called radiant barrier foil. It is a composite of plastic and aluminum layers. The concrete Barrier Foils consists of an aluminum layer sandwiched between two layers of bubble insulation. The insulating effect of this new product is comparable with the rigid foam products, but its handling and resistance to mechanical damage is far superior. The amount of underside insulation depends on several factors. Among them are: The severity of the climate: colder climates justify edge- and underside insulation of greater R-value. The cost of energy: higher energy costs justify edge- and underside insulation of greater R-value. The thermal resistance (R-value) of the floor covering(s): high thermal resistance coverings justify edge- and underside insulation of greater R-value. The shape of the slab: slabs with high ratios of edge length to floor area justify edge- and underside insulation of greater R-value. In most buildings the underslab insulation should have a minimum R-value of 5. In colder climates, it is often recommended that the outer 4 feet of the slab (referred to as the outer band ) have R-10 underside insulation. The insulation is generally omitted under structural bearing points such as beneath interior columns or bearing walls. The edge of the slab is especially vulnerable to heat loss. It should be insulated to a minimum of R-5 in mild climates and R-10 in colder climates. The next step on most installations is to locate and temporarily mount the manifold station(s). If one or more of the manifold stations will be located within a stud cavity, it s imperative to make accurate measurements when fixing the manifold s location. The manifolds can be temporarily bracketed to a plywood panel supported on wooden or steel stakes driven into the subgrade (as shown in figure 4-2) Figure

35 THE IPEX MANUAL OF MODERN HYDRONICS Once the insulation is in place, the steel reinforcement for the slab is installed. Most concrete slab on grade floors use welded wire fabric (WWF) for reinforcement and crack control. WWF comes in sheets or rolls. It should be placed directly on top of the underslab insulation. Edges should be overlapped approximately 6 and tied together. Tubing installation takes place one circuit at a time. Begin by securing one end of the circuit to the supply manifold. Roll out the coil like rolling a tire following the layout pattern. The composite pipe, because of the metal content, allows laying the pipe roughly without tying down immediately. This allows it to run the full loop and get the end out to the manifold. Make sure the end reaches the manifold and then tie the piping to the wire mesh. The main difference to laying PEX tubing is that the pipe stays in place and does not want to go back to the coil shape. This is why there is no need to use an uncoiler. If the uncoiler is available, it is also possible to lay the pipe using it. In this case place the tubing coil on an uncoiler and pull the tubing from the coil as needed. Keep plenty of slack ahead of you as the tubing is fastened in place. Kitec tubing should be secured to the WWF using either twisted wire ties or nylon pull ties. The tubing should be tied to the WWF reinforcing every 60 to 72 on straight runs, and two ties at the bend on each side. When all circuits have been installed, prepare the manifold(s) for pressure testing. Install a pressure gauge in one end of either the supply or return manifold and a schrader air valve in the other end. Plug the unused manifold ends. Use an air compressor to increase the pressure in the circuits to about 100 psi. Use a soap bubble solution to check for leaks at the manifold connections. Leave the circuits pressurized for at least 24 hours. If the air pressure drops double check all manifold connections for possible leaks before inspecting the tubing. Aside from the possibility of extreme damage from other construction activity, it s very unlikely that the tubing is the source of the air leak. Still, a pressure test is mandatory on any radiant tubing installation. If the WWF has to be positioned in the slab, be sure the concrete placement crew knows to lift the tubing and WWF prior to starting the pour. If the WWF has to be positioned within the slab, it has to be lifted or chaired up to the final position before the concrete is poured. The WWF and attached tubing should be lifted up so the pipe center is 2 below the slab surface. This allows the slab to respond faster when warm water circulates through the tubing. From the heat output point of view, the position of the piping in the slab is not so critical if full slab insulation is used. Appropriate thermal break will direct the heat flow towards the surface. If insulation is not used the pipe position is critical and in this case the piping has to be lifted to 2 below the surface. As long as the pipe is kept 2 below the surface saw cut control joints will not affect the pipe. If deeper than 3/4 saw cuts are planned the pipe position has to be adjusted accordingly. Anywhere where full cut control joints are used (slabs are separated) a protective sleeve has to be used on the pipe passing through. The sleeve has to be 12 long centered on the joint and approximately 1 diameter. The sleeve reduces stress on the tubing should the slab move slightly at the control joint. 4-5 Thin Slab Systems There are several methods of installing hydronic radiant heating over a conventional wood-framed floor. One of the most common is called a thin slab system. The concept is shown in figure 4-3. Thin slabs consist of either a specially formulated concrete or poured gypsum underlayment. Both types of slabs have installation requirements that must be carefully coordinated with the building design process. One requirement that must be accommodated is that thin-slabs typically add 1.25 to 1.5 inches to the floor height. This requires adjustments in the rough opening heights of windows and doors as well as the height of door thresholds. It will also affect the riser heights on stairs. Another issue that must be addressed is the added weight of the thin-slab. Poured gypsum thin-slabs typically add 13 to 15 pounds per square foot to the dead loading of a floor structure. Standard weight concrete thin slabs add about 18 pounds per square foot (at 1.5 thickness). Never assume the proposed floor structure can simply support the added weight of either type of thin-slab. Have a competent designer or structural engineer verify what, if any, changes are necessary to support the added load. The additional floor thickness and weight are easily managed if planned into the building as it is designed. However they can present obstacles in retrofit situations. Poured Gypsum Thin-slab systems Poured gypsum underlayments have been used for many years for floor leveling as well as to enhance the acoustic and fire resistance properties of wood-framed floors. They also function well as the slab material for thin-slab floor heating systems. In most cases, the slab is installed by a subcontractor trained and equipped to 38

36 SECTION 4 RADIANT FLOOR HEATING METHODS Figure 4-3 finished flooring adhesive gypsum slab pipe sealant subfloor floor joist under side insulation 39

37 THE IPEX MANUAL OF MODERN HYDRONICS Figure 4-3A finished flooring adhesive concrete slab pipe polyethylene sheet subfloor floor joist underside insulation THIN SLAB ON WOOD FRAMED FLOOR concrete slab 40

38 SECTION 4 RADIANT FLOOR HEATING METHODS mix and place the materials. Installation Procedure Installation begins by stapling the tubing to the subfloor. A pneumatic stapler with a special attachment allows the staples to be quickly placed without damage to the tubing. It s the preferred attachment method for all but very small thin-slab areas. Once all tubing circuits have been installed they should be pressure tested as described earlier. Next the floor is sprayed with a combination sealant/bond enhancement coating. This minimizes water absorption into the subfloor as well as strengthening the bond between the slab and subfloor. The poured gypsum underlayment consists of gypsum cement, masonry sand, admixtures and water. The product is prepared is a special mixer usually placed outside the building, and is then pumped in through a hose. As the product is poured, it self-levels with minimum floating. Some installers prefer to install the gypsum slab in two layers (or lifts ). This minimizes any differential shrinkage in the slab, resulting is a very flat finish surface. When poured gypsum underlayment cures, it resembles plaster and is almost as hard as standard concrete. However, unlike concrete it is NOT intended to serve as a permanent wearing surface. With the proper preparation, a poured gypsum slab can be covered with almost any finish flooring including carpet, sheet vinyl, ceramic tile and glue-down wood flooring. Always follow the gypsum underlayment manufacturer s procedures to verify that the slab is adequately cured that and the surface is properly prepared before installing finish flooring. Poured gypsum slabs are water-resistant not waterproof. The slab will eventually soften if exposed to water for prolonged periods. They should not be installed under conditions where rain or other sources of moisture can accumulate. They should also not be installed in areas that are likely to experience flooding. Concrete Thin-Slab Systems A specially formulated concrete mix can also be used to create a heated thin-slab floor. The mix proportions are given in figure 4-4 The installation of a concrete thin-slab differs considerably from that of a poured gypsum slab. Concrete is not self-leveling. It must be screeded flat when placed. To simplify screeding, the concrete thin-slab is best poured before walls are constructed. Figure 4-4 Unlike with gypsum underlayments, it s crucial to prevent the bottom of the slab from bonding to either the subfloor or any wall framing it may contact. The goal is to allow the wood floor deck and concrete thinslab to move independently of each other during curing or seasonal moisture changes. This reduces tensile stresses that can crack the slab. It s also important to divide large floor areas into a grid of smaller areas using plastic control joint strips. As the concrete cures, cracks will develop directly above these strips. These controlled cracks preempt random cracking of the slab. The slab should be cured for a minimum of 3 weeks prior to being heated. This allows time for the concrete to develop strength before being exposed to thermal stresses. To drive off any residual moisture, the slab should also be operated (heated) for several days prior to installation of the finish floor. With either type of thin-slab it s imperative to install underside insulation. When the space below the heated floor is also heated, use a minimum of R-11 underside insulation. If the space below the floor is partially heated, install a minimum of R-19 insulation. If the space below the heated floor is an unheated crawl space, install a minimum of R-30 underside insulation. Although these suggested underside R-values are conservative, the installer should verify they meet or exceed local energy code requirements. 41

39 THE IPEX MANUAL OF MODERN HYDRONICS The concept of thin slab installation can be used retrofitting radiant floor heating to existing concrete surfaces. A thin over pour or topping pour is created on the existing surface. Figure 4-4a shows the layers of the installation. Ideally the new layer is separated with a thin layer of insulation. This will drive the heat upwards where we need it and provide quick reaction time. Generally ½ to 1 rigid foam is used. Using a vapor barrier ensures that no moisture gets into the heated layer. A new type of insulation is also now available. Two layers of bubble insulation with aluminum foil in between has a comparable insulating effect to the rigid foam. It also acts as a vapor barrier. The most difficult part when laying pipe on existing concrete is how to fasten the pipe. Individual clips can be used, though it is very Figure 4-4a finished flooring adhesive concrete slab pipe insulation existing concrete TOPPING POUR ON CONCRETE FLOOR 42

40 SECTION 4 RADIANT FLOOR HEATING METHODS time and labor consuming. Special plastic staples or clips can be used when 1 foam is used as insulation. Another effective way is to use pipe track, sometimes called rail fix, to hold the pipe in place. This 6.5 feet long plastic channel is mounted to the floor at 3 points. The pipe clips into the side cutouts perpendicular to the track. 1¼ -1½ thickness of smooth regular concrete is poured to cover the pipe and create a very effective thermal mass. There are no structural or strength issues the original slab takes care of that. The doors have to be adjusted accordingly to accommodate the level increase. 4-6 Tube & Plate Systems A concrete or gypsum slab acts as a thermal wick to help spread the heat releases from the embedded tubing across the floor surface. However, there are situations where slab installation is not an option. In such cases the heat dispersion can be provided by highly conductive aluminum plates. Kitec PEX-AL-PEX pipe is ideal for tube and plate applications. Its rate of thermal expansion is very close to that of the aluminum heat dispersion plates. This greatly reduces the potential for expansion sounds as the system warms and cools. Figure 4-5 shows the general concept of a tube and plate system. Notice how the aluminum plates are shaped to fit the perimeter of the tubing. Heat transferred from the tubing to the trough portion of the plate conducts out along the wings of the plate. Because aluminum is an excellent heat conductor, these relatively thin plates can disperse across the floor almost as well as a slab yet at a tiny fraction of the weight and only about 1/2 the added floor height of a thin-slab. They are a versatile component both for floor heating systems as well as radiant walls and ceilings. The heat is conducted to the plate from the pipe and spreads along the flat "wings". The large contact surface evenly conducts the heat to the floor. plates used in joist space heating system (below subfloor) finished flooring subfloor heat transfer plate pipe plates used with sleeper system (above subfloor) heat transfer plate pipe finished flooring spacer (sleeper) subfloor THE CONCEPT OF TUBE & PLATE SYSTEMS Figure

41 THE IPEX MANUAL OF MODERN HYDRONICS Above Floor Tube & Plate Systems Figure 4-6 shows the installation of an above floor tube and plate system. Here the tubing and plates are located on the top side of the floor deck. The tubing can be run in virtually any direction. The system can be adapted to several types of finish flooring, and is particularly well suited for nailed down wood floor installations. Figure 4-6 finished flooring spacer (sleeper) pipe heat transfer plate subfloor floor joist underside insulation SLEEPER SYSTEM ON WOOD FRAMED FLOOR above floor tube and plate 44

42 SECTION 4 RADIANT FLOOR HEATING METHODS Installation Procedure: Begin by fastening 5/8-3/4 plywood or oriented strand board (OSB) sleepers to the floor. The sleepers are placed to create 3/4 wide grooves into which the tubing and trough portion of the plates are recessed. To minimize any squeaks, the sleepers should be glued as well as nailed (or screwed) to the subflooring. Grooves for the return bends, as well as other curved tubing paths can be formed by routering out the 3/4 plywood or OSB. Another way is to place triangular shaped spacers to support the secondary floor layer at finished flooring spacer (sleeper) pipe subfloor floor joist underside insulation SLEEPER SYSTEM ON WOOD FRAMED FLOOR above floor tube 45

43 THE IPEX MANUAL OF MODERN HYDRONICS curved areas. The plates are set into the grooves with ends spaced about 1 apart. Pull each plate against one edge of the sleeper and tack it in place with two or three light gauge staples on the same side (and only on this side). This allows the plate to expand as the tubing is pushed into it as well as when the plate heats and cools. Then tubing is laid out and pushed into the grooves in the plates. Stepping on the tube as it aligns with the grooves ensures it is pushed all the way into the groove. It is NOT necessary to install silicone caulking into the troughs of the plates when installing Kitec PEX-AL-PEX pipe. Above floor tube and plate systems are ideal when nailed-down wood flooring will be installed. The flooring can be placed directly over the tube and plates without needing an additional cover sheet. The flooring should be installed with its long dimension perpendicular to the tubing. Nails can be driven through the heat transfer plates, through the sleepers and into the subfloor. Be careful not to drive nails through the tubing on return bends or other areas when the tubing is not visible as the flooring is laid. If the tubing needs to run parallel to the flooring at times, it is best to drill a shallow hole through the subfloor and route the tubing through the floor framing where it is protected against nail punctures. The tubing can also be plunged beneath the subfloor and then routed up through the bottom plate of a partition to connect to the manifolds. For other types of flooring, it is necessary to install a thin 1/4 or 3/8 cover sheet over the tube and plates to serve as a smooth stable substrate. Plywood is often used as the cover sheet under vinyl flooring or carpet. Cement board has also been used under ceramic tile. All tubing circuits should be pressure tested prior to installing the cover sheet. The tubing should remain pressurized as the cover sheet is installed. Be careful not to drive fasteners through the tubing when securing the cover sheet. The same concept of the sleeper system can be used in low heat load installations, but without the heat transfer plates mostly for floor warming systems. The wood structure is a poor conductor of heat so there is limited heat transfer sideways. The relatively thin layer directly above the pipe will allow a lot more heat through than sideways. This results in large local temperature differences depending on the position of the pipe. This effect limits the amount of heat that can be transferred without creating high temperature lines on the floor surface. The spacing used should be 6-8 and again only a limited amount of heat output can be provided. To overcome this limitation, some manufacturers produce pre-routed plywood sheets with aluminum layer attached to it to improve sideways transfer. Below floor tube & plate systems It s also possible to fasten the tubing and aluminum heat dispersion plates against the bottom of the subfloor. Below floor tube and plate systems work well when raising the floor level is not an option. The concept is shown in figure 4-7. The plate cradles the tubing against the subfloor as well as disperses the heat across the floor to avoid objectionable variations in floor surface temperatures. The ideal installation conditions for this system would be completely unobstructed floor joist cavities. However this is often not what the installer has to deal with. In some cases, plumbing, electrical, ducting or other utilities may already be routed through the joist cavities. This could make access to the underside of the subfloor difficult or even impossible. Always inspect the underside of the floor deck before committing to a below floor tube & plate installation method. 46

44 SECTION 4 RADIANT FLOOR HEATING METHODS Figure 4-7 finished flooring pipe heat transfer plate subfloor floor joist underside insulation JOIST SPACE HEATING below floor tube and plate 47

45 THE IPEX MANUAL OF MODERN HYDRONICS With a below floor installation, the tubing is pulled into one joist cavity at a time and fastened up along with the heat dispersion plates. The suggested installation sequence is depicted in figure 4-8. The holes in the floor framing must be large enough for the tubing to be easily pulled through. As with thin-slab systems, it s imperative to install underside insulation. When the space below the heated Preparation: floor is also heated, use a minimum of R-11 underside insulation. If the space below the floor is partially heated, install a minimum of R-19 insulation. If the space below the heated floor is an unheated crawl space, install a minimum of R-30 underside insulation. Although these suggested underside R-values are conservative, the installer should verify they meet or exceed local energy code requirements. THREADING pipe IN for joist space heating systems Make a sketch of the floor surface and joists through which piping will be threaded and installed. Identify the manifold location and route to the manifold for each pipe loop. Measure the length of the floor joist and multiply the joist length by two. This defines the footage of pipe per joist cavity when floor joists are installed on 10" through 18" centers. When floor joists are on 10" through 18" centers, two runs of pipe are installed in each joist space. Three runs of pipe are installed in a joist space when joists are spaced greater than 18" apart. Calculate the number of joist spaces you can cover with the pipe coil length you are using. For example, if the joist is installed on 18" centers and it is 20 feet long, multiply 20 x 2 to get 40 feet of pipe per cavity. Assuming a 300 foot coil length, 7 joists cavities could be covered. BUT, remember that you need to allow for the length of pipe running from the manifold and back again. In this example and depending on the manifold location perhaps only 6 cavities can be filled. Pre-drill holes in the floor joists through which pipes will run. Two 1/2" pipes require a 1-1/2" diameter hole, while four 1/2" pipes require a 2" diameter hole. Holes should always be straight and aligned. Holes must be drilled in the center of the floor joist and at least one foot away from the end of the joist support point. This sketch shows the completed installation from below. The following figures lead us through a step by step process. 48 Figure 4-8

46 SECTION 4 RADIANT FLOOR HEATING METHODS Pull pipe from the uncoiler and thread it through the pipe holes making a loop in each bay. The loops needn t be too long, leave just enough hanging from the joist that allows you to handle the pipe. Leave the pipe end hanging free in the last bay. Return to the first bay. Pull enough pipe from the uncoiler to create a large loop. Move the slack from the first bay over to the second bay, then over to the third, fourth, etc., until the last bay has enough pipe to run back to the manifold and complete the pipe loop inside the bay itself. Keep moving the slack! 49

47 THE IPEX MANUAL OF MODERN HYDRONICS Use the pipe from the last bay and run it back to the manifold in the same joist holes as the loops. If the slack in the last bay is not sufficient to run back to the manifold, feed more pipe from the uncoiler through the bays until the desired length is achieved. Attach the pipe to the manifold. Ideally, you should leave enough pipe hanging from the last bay to form the first finished section of the floor. Lift the pipe loop up into the joist space and begin fastening the pipe to the subfloor. Always start fastening the pipe on the side of the loop that runs back to the manifold. If more pipe is needed to complete the loop, it can be fed from the neighboring joist space. The slack in the last bay has disappeared and the pipe is now attached to the subfloor. Move back to the first bay and pull more pipe from the uncoiler until a large amount of slack exists. Transfer this slack through adjacent bays until it arrives in the second to last bay. Lift the slack up and fasten the pipe in this joist space as before. Continue this process until all joist spaces are complete. The installation is nearly complete! Once all bays are finished, measure the distance from the first bay to the manifold. Cut the correct length of pipe from the uncoiler making certain to leave enough pipe to connect to the manifold. This process involves a good deal of pipe threading, but it eliminates pipe kinks and reduces stress on the pipe. Two people can work very effectively together with this installation method - one feeding pipe while the other fastens pipe in the joist space. 50

48 SECTION 4 RADIANT FLOOR HEATING METHODS For joists installed on greater than 18" centers, three runs of pipe are required in each joist space. The pipe handling and installation technique is similar in concept to that described in steps 1 through 8. Create pipe slack and transfer the slack to adjacent bays as before. Note in the following sketch however, that pipe enters the bay at one end of the joist and exists at the opposite end in order to accommodate three runs of pipe. 51

49 THE IPEX MANUAL OF MODERN HYDRONICS 4-7 Suspended tube systems The ability of Kitec PEX-AL-PEX piping to handle relatively high water temperatures makes it possible to install a suspended tube system as depicted in figure 4-9. The tubing is placed within the air cavity between the floor joists. The tubing gives off direct radiant energy to the surfaces within the joist cavity. The outside of the tubing also gives off heat to the surrounding air, establishing a gentle convective circulation within the joist cavities. The warm air flows across the underside of the subfloor transferring more heat to it. Suspended tube systems have some unique benefits. They don t require heat dispersion plates and thus reduce installation cost. They operate at high water temperatures under design load conditions and thus can often be piped directly to a boiler without needing a mixing valve. When the tubing is suspended below the subfloor, it is not subject to puncture from the nail points associated with installation of hardwood flooring. Kitec PEX-AL-PEX piping is ideal for suspended tube systems. Its aluminum core provides the structure that prevents the tubing from sagging between supports when operated with high water temperatures. As with all floor heating systems, it s imperative to install underside insulation. This must be a reflective insulation system meaning that there is a shining reflective metal surface facing the pipe. There has to be an air gap between the pipe and the reflective layer minimum 2 or more. Foil faced batting insulation or the aforementioned bubble insulation can be used. The bubble insulation is different from the one used with concrete. The aluminum layer is exposed on one side minimum and is always facing the piping. The insulating layer can be one or two layers of plastic bubble depending on the amount of insulation required. Figure

50 SECTION 4 RADIANT FLOOR HEATING METHODS When the space below the heated floor is also heated, use a minimum of R-11 underside insulation. If the space below the floor is partially heated, install a minimum of R-19 insulation. If the space below the heated floor is an unheated crawl space, install a minimum of R-30 underside insulation. Although these suggested underside R-values are conservative, the installer should verify they meet or exceed local energy code requirements. Threading the pipe into the joist space is identical to the method explained under the section discussing joist space heating with heat transfer plates. The fastening of the pipe is different in this case. There are three main ways to secure the pipe; stapling to the underside of the subfloor; using a pipe hanger to suspend the pipe in the joist cavity; or use a nail clip to nail the pipe directly to the side of the joist. Stapling to the floor is very simple, however the pipe is close to the surface and can be punctured easily from above. The other two overcome this problem, but an extra item pipe hanger or nail clip is used. In high heat load installations, the direct stapling to the underside can result in high and low temperature lines on the floor. The fastest and easiest to install is the nail clip method. They all have their advantages and disadvantages. It s possible to staple Kitec pipe directly against the underside of the subflooring without using heat dispersion plates. As discussed above this approach is only suggested for low heating load situations such as rooms that have minimal if any exterior exposure. Without either a slab or aluminum heat dispersion plates, the floor s ability to spread the heat laterally away form the tubing is more limited. Still, when the design heat load of the space doesn t exceed 15 Btu/hr/sqft, this installation method can deliver adequate heat output at reasonable water temperatures. finished flooring subfloor pipe reflective layer min. 2" air gap floor joist underside insulation JOIST SPACE HEATING below floor tube stapled finished flooring subfloor pipe in pipe hanger pipe hanger floor joist reflective layer min. 2" air gap underside insulation JOIST SPACE HEATING below floor tube suspended 53

51 THE IPEX MANUAL OF MODERN HYDRONICS finished flooring subfloor pipe in pipe hanger pipe hanger reflective layer min. 2" air gap floor joist underside insulation stapled inside the joist cavity Reflective foil insulation (aluminum-bubble) JOIST SPACE HEATING below floor tube suspended finished flooring subfloor pipe in pipe hanger pipe hanger floor joist reflective layer under side insulation stapled to the bottom of the joists Reflective foil insulation (aluminum-bubble) JOIST SPACE HEATING below floor tube suspended finished flooring 1"- 2" distance from floor subfloor pipe mounted with nail clip reflective layer min. 2" air gap floor joist underside insulation JOIST SPACE HEATING below floor tube clipped to joist 54

52 SECTION 4 RADIANT FLOOR HEATING METHODS In this chapter, we pointed out the effects of the floor construction method on the radiant floor heating system. As a summary, it is probably fair to say that piping can be fitted into any floor surface and there are numerous variations to fit the project circumstances. It should also be clear that there are important differences between these methods and some are better suited than the other for effective heat transfer. The following image (figure 4-10) illustrates the heat transfer process during joist space installation using heat transfer plates or direct staple up. The image speaks for itself and gives very good reasons to consider using the heat transfer plates wherever it is possible. Comparison of floor surface temperatures with and without heat transfer plates for 1/2" tubing 8" o.c., operated at 100ºF and 140ºF water temperatures Figure

53 SECTION 5 RADIANT WALLS AND CEILINGS Although the majority of hydronic radiant heating systems are installed in floors, the walls and ceiling of a room can also make excellent radiant panels. This is possible because radiant energy travels equally well in any direction. Just as visible light travels downward and sideways from a ceiling fixture to illuminate the surfaces below, infrared light (e.g. radiant heat) will travel to warm the objects in the room below. Experience with hydronic ceiling heating in North America dates back to the 1940s. Many systems were installed using both copper and iron tubing embedded in plaster on lathe ceilings. These systems demonstrated that radiant ceiling heating is not only feasible, but also able to create excellent comfort conditions. Some of these systems are still functioning today. 5-1 Advantages of Radiant Walls and Ceilings Hydronically heated walls and ceilings offer several unique advantages compared to one or more of the floor heating options discussed in section 4. In circumstances where floor heating is not possible due to floor covering selections, heating load requirement (or other considerations) a heated wall or ceiling may be an ideal alternative. Keep the following advantages in mind as you evaluate your installation options. The output of heated walls and ceilings is not affected by floor coverings or furniture. Even a heated floor that s initially installed with a low resistance covering may, at some future date, get covered with a high resistance finish floor that could substantially reduce its heat output. Most walls, and in particular ceilings, are unlikely to get more than a few coats of paint over the life of the system. Rooms such as bathrooms and kitchens often have a significant portion of their floor area occupied by base cabinets, islands, appliances or other objects that prevent the underling floor from being an effective heat emitter. In contrast, the ceilings of such spaces usually provide a virtually unobstructed surface from which radiant heat can be emitted. A radiant ceiling will also warm the countertop, floor 57

54 THE IPEX MANUAL OF MODERN HYDRONICS and tub surfaces below. In rooms where prolonged foot contact with the floor is likely, the maximum floor surface temperature should not exceed 85 deg. F. This limits the heat output from a heated floor to 35 to 40 Btu/hr/sq. ft. However, this temperature limit does not apply to heated walls and ceilings. A heated ceiling 8 feet above can be operated at temperatures as high as 100 deg. F. A 9 ft. tall ceiling can be operated as high as 110 deg. F. At these surface temperatures, heat outputs in excess of 70 Btu/hr/sqft are possible from either a heated wall or ceiling. Because of the higher outputs, the area of the radiant panel can often be reduced. This in turn reduces installation cost. Heated walls and ceilings typically have very low thermal mass and can respond quickly to changing load conditions. This is especially advantageous in rooms with significant solar gains or other sources of internal heat. This fast response is also beneficial for spaces that need to be quickly restored to normal comfort after prolonged setback periods. Heated walls and ceilings typically add very little weight to the structure and thus don t require structural alterations. Heated ceilings usually require less vertical space than most types of floor heating instalations. This may be a significant advantage in retrofit situations, especially in basements with limited head room. Heated ceilings create very little air distubance in the room below. Approximately 95% of the output from a heated ceiling is in the form of radiant energy. Very little convection is created. The reduced air movement is especially desirable in rooms where dust movement and drafts need to be avoided. A radiant wall is an excellent addition to a walk-in shower. The warmed surface greatly improves the comfort over that of cold tile surfaces, especially if one or more walls are exposed to outdoor ambient conditions. The heated wall can be used to supplement the output of a heated floor. It also helps dry the shower walls quickly after a bath. Radiant walls make an excellent supplement to floor heating for indoor pool enclosures. In many cases, the amount of floor area available is limited due to the size of the pool. A low profile radiant wall will not only supplement the heat output, but will also significantly improve the comfort and help dry water splashed on the wall. 5-2 Radiant Wall Construction Radiant walls can be constructed using a variation of the tube and plate system described in section 4. Figure 5-1 shows how the components go together. In most rooms, it s neither necessary nor desirable to heat an entire wall from floor to ceiling. A better approach is to heat a low perimeter band along the wall. The heated area may extend 3 to 4 feet above the floor. This approach tends to direct the radiant energy into the lower (occupied) portion of the room. A perimeter band can often be planned to run beneath the windowsill level to keep the tubing layout simple. Since the tubing is only installed in the lower portion of the wall, there s much less chance of it being struck by a nail (such as when a picture is hung on the wall). A chair rail molding often provides a convenient architectural divider for a transition between the heated lower portion of a wall and the unheated upper portion. Installation: If the tube and plates will be installed on the inside surface of an exterior wall, be sure that the wall is well insulated. To keep the outward heat loss comparable to that of a non-heated wall, the R-value of the wall insulation should be increased by about 50%. A vapor barrier should also be installed on the warm side of the insulation. If the tube and plates will be installed on an inside partition, an R-11 fiberglass batt or other insulation with equivalent R-value should be installed behind the tube and plate system to steer the heat in the desired direction. Begin by ripping 3/4 plywood sheets into strapping boards. The strapping boards, shown in figure 5-1, should have width 3/4 less than the tube spacing to be used. They can be nailed or screwed to the wall framing leaving a 3/4 gap between each adjacent row. These gaps accommodate the tube and trough portion of the heat dispersion plates. Most walls require electrical outlets. When the wall will be clad with a tube and plate system, the junction box must extend an additional 3/4 out beyond the face of the wall studs to accommodate the added thickness of the strapping. It s usually easiest to install the necessary junction boxes before fastening the 3/4 plywood strapping to the wall. The tubing and aluminum heat dispersion plates should be kept at least 2 away from the junction boxes to minimize heat transfer to the box and the electrical device it contains. 58

55 SECTION 5 RADIANT WALLS AND CEILINGS Figure 5-1 Where the tubing needs to form a return bend, hold the strapping short of the end of the wall by a distance approximately equal to the radius of the tube bend. A 1.5 x 3/4 plywood strip should be installed at the ends of the wall as a solid surface to which the wall finish can eventually be fastened. Be sure to plan where the tubing will enter and exit the wall. Figure 5-2 shows these details. After the strapping is installed, the aluminum heat dispersion plates can be set in place and tacked using 2 or 3 staples through one wing of the plate. Be sure to pull the trough portion of the plate to one side of the strapping before stapling it. This creates a slight gap on the other side of the trough allowing the plate to expand slightly as the tube is pressed in place. Leave a gap of approximately 1 inch between ends of adjacent plates. Uncoil the Kitec pipe and press it into the plates. Be sure to leave enough slack at the beginning and end of the serpentine pattern to connect the circuit to a manifold. A rubber-faced mason s float makes an excellent tool for tapping the tubing into the plates without denting them. After the circuits have been pressure tested, the wall can be covered with drywall or other panels. If the wall is to be finished with ceramic tile, the tubing and plates can be covered with a layer of cement board. The tile would then be bonded to the cement board with thin set mortar. Be sure not to drive fasteners through the tubing when installing the wall covering. 59

56 THE IPEX MANUAL OF MODERN HYDRONICS vapour barrier Figure 5-1A 60

57 SECTION 5 RADIANT WALLS AND CEILINGS Figure Radiant Ceilings Construction The same tube and plate system used for a heated wall can also be used to create a radiant ceiling. Essentially the whole system is simply rotated by 90 degrees. The concept is shown in figure 5-3. Installation: Again, it is suggested that any electrical boxes on the ceiling be installed with an additional 3/4 projection below the ceiling framing prior to installing the strapping. After the strapping is installed, the aluminum heat dispersion plates can be set in place and tacked using 2 or 3 staples on one side of the plate. Be sure to pull the trough portion of the plate to one side of the strapping before stapling it. This creates a slight gap on the other side of the trough, allowing the plate to expand slightly as the tube is pressed into place. Leave a gap of approximately 1 inch between ends of adjacent plates. Uncoil the Kitec pipe and press it into the plates. A rubber-faced mason s float makes an excellent tool for tapping the tubing into place without denting the plates. The slightly overbent shape of the heat dispersion plates will hold the tubing up after it is pushed tightly into place. After the circuits have been pressure tested the ceiling can be drywalled. Leave some air pressure in the tubing as the drywall is installed. Because of the plywood strapping, additional screws and nails can be used if necessary to ensure the drywall is pulled tightly against the tubing and plates. Snap a chalk line halfway between the rows of piping and install the drywall fasteners along it. Be especially careful not to drive fasteners through the tubing near the return bends. 61

58 THE IPEX MANUAL OF MODERN HYDRONICS Figure 5-3 Figure 5-3A 62

59 SECTION 6 MANIFOLD SYSTEMS 6-1 Introduction The vast majority of new hydronic radiant heating systems use one or more manifold stations as the connecting points for the tubing circuits. All manifold stations consist of a supply manifold and a return manifold. The manifold station might be equipped with trims such as valve actuators, circuit flow meters, isolation valves and venting/draining components. The necessary trim is determined by how the system is intended to operate. For example, it s possible (although not always necessary) to operate each radiant panel circuit on the manifold station as an independent zone. A tubing circuit that heats the floor of the master bathroom could operate while the circuit(s) serving the bedroom adjacent to it remain off. This section discusses the various manifold systems available from IPEX and suggests where each is appropriate. 6-2 Zoning Considerations Hydronic heating has long been known for its ability to provide heat precisely when and where it s needed. If the building occupants desire a bathroom maintained at 75 deg. F., a child s bedroom at 65 deg. F., and an unused guest room at 55 degree F., hydronic heating can easily accommodate their needs. Before planning the location of manifold stations, decisions need to be made on how the areas will be zoned. One option is to treat the entire building as a single zone. This is appropriate when the following conditions are met: The occupants want to keep all rooms at similar and constant (although not necessarily identical) temperatures. All rooms have similar internal heat gains from sunlight, equipment, people and other sources. 63

60 THE IPEX MANUAL OF MODERN HYDRONICS If temperature setback is used, all rooms will operate on the same setback schedule. There is relatively good air flow between rooms. The doors between individual rooms and interconnecting spaces are left open most of the time. If these conditions are met, the entire building could be controlled as a single zone using a single thermostat (or other type of interior air temperature sensor). Since the control hardware is minimized, this approach will reduce installation cost. When the conditions described above are not met, it s appropriate to plan the system for multiple zones. When planning for multiple zones consider the following: What group of areas (if any) tend to have similar temperature requirements at the same time of day. For example, a home may have two or more bedrooms that are unoccupied during the daytime and thus could be kept at a reduced temperature to reduce fuel usage. What areas have similar internal heat gain patterns. For example on sunny days some rooms may receive enough direct solar heat gain to offset most of their heating load, even when it s very cold outside. A properly zoned system should allow the heat input from the hydronic system to these rooms to stop under such conditions. At the same time, other rooms that don t experience these heat gains should receive the necessary heat input to maintain their set temperatures. What areas have heat emitters with similar thermal mass. A room with a higher thermal mass system such as a heated concrete slab will not warm nor cool as fast as an otherwise identical room heated by fin-tube baseboard. If these two rooms were on the same zone, and that zone was operated with a temperature setback strategy, or experienced significant solar heat gain, the two rooms cannot respond comparably. The room heated by fin-tube baseboard could quickly interrupt heat input when solar heat gains occur, while the room with the heated slab would likely overheat due to the significant amount of heat stored in the slab. A common misconception about zoning: Some heating system designers feel that every room that may, at some point, need to be at a temperature different from that of other rooms, must be operated as an independent zone with its own thermostat. This is not true. It s possible under the right circumstances to maintain rooms at different air temperatures even though they are grouped together as a single zone and operated by a single thermostat. One way to accomplish this is through the heat output capacity of the heat emitters. Imagine two identical rooms that have the same heating load. One has 10 feet of baseboard; the other contains 12 feet of the same baseboard. Water at the same temperature is supplied to both baseboards at the same time. Obviously there will be greater heat output into the room with the longer baseboard and thus it will attain a higher air temperature under all load conditions. In the case of radiant panel heating, the output of the panel at a given water supply temperature can be altered by changing the amount of pipe used in the floor. The easiest way to achieve this is to vary the tube spacing. Again, imagine two identical rooms with a heated slab floor. In one room the tubing is spaced 9 inches on center. In the other the tubing is spaced 12 inches on center. Assuming both rooms are supplied with the same water temperature at the same time, the room with the closer tube spacing will receive more heat input and thus attain a higher air temperature. Another method of controlling heat output, one that can be adjusted once the heat emitters are installed, is by varying the flow rate through individual heat emitters. Once again imagine two identical rooms with identical heating load, and identical heat emitters. Both rooms are controlled from a single thermostat, and have the same supply water temperature while operating. If the flow rate through one baseboard is reduced using a balancing valve, the average water temperature in that heat emitter will decrease as will its heat output. Thus the room operated at the lower flow rate will stabilize at a lower air temperature. Understanding the above concepts and applying them when appropriate can reduce system costs. It also doesn t mandate the installation of individual room thermostats when they are not necessary. 6-3 Type of Manifolds Manifold stations can be constructed using either valved or valveless manifold components. Valved manifolds are either supplied with a shut-off valve for electrical actuator or balancing valve for each connected circuit. The valves allow the flow rate through individual tubing circuits to be adjusted, or completely stopped if necessary. Valveless manifolds, as their name implies, do not have this capability. They serve solely as a header for the attached circuits. In situations where individual flow control of each 64

61 SECTION 6 MANIFOLD SYSTEMS circuit is desired a valveless manifold is installed as the supply manifold where each tubing circuit begins, and a valved manifold is installed as the return manifold where each circuit ends. This allows the optimal flow direction through the manifold valves. Figure 6-1 shows a 4-circuit valved as well as valveless manifold. A valveless manifold can also be combined with a zone valve as shown in figure 6-2 when several circuits are to be controlled from a single thermostat. This option is less expensive than installing several valve actuators on individual circuits and controlling them as a group. Figure 6-1 Figure 6-2 Valveless Manifold Systems There are radiant panel heating applications where valveless manifold systems are well suited. Recognizing such situations often allows the installed cost of the system to be reduced. An appropriate application for valveless manifolds is when a large building area is to be heated as a single zone. The large area requires several tubing circuits that all operate at the same time with the same supply water temperature. Provided that circuit lengths are kept within 10% of the same length, such circuits can be connected to a single valveless manifold. The designer should recognize that circuits connected to valveless manifolds cannot be individually balanced or isolated. They also must be purged simultaneously when the system is filled. The designer should ensure that adequate means of high capacity purging are provided for each valveless manifold station. In most cases, the advantage of being able to isolate and shut down the loops far outweigh the cost saving by using valveless manifolds. Valved Manifold Systems In many hydronic systems including those supplying radiant panels as well as other types of heat emitters, the flow resistance of each connected circuit can vary considerably. For example, in the case of radiant floor heating, one tubing circuit my be 60 feet long while another, connected on the same manifold, may be 300 feet long. If such circuits are connected to a valveless manifold station, the flow rates will be higher in the shorter circuits. This may not allow sufficient heat delivery in the areas served by the longer circuits. A manifold station with circuit balancing valves on either the supply or return manifold allows the flow resistance of each circuit to be adjusted. This helps ensure that each circuit delivers the proper flow rate to its heat emitter. Valved manifolds also allow the possibility of individually controlling each attached circuit. The most common approach is to attach an electric valve actuator to each valve bonnet on the manifold as shown 65

62 THE IPEX MANUAL OF MODERN HYDRONICS in figure 6-3. As it s screwed onto the manifold valve, the actuator pushes the valve s stem to its fully closed position. When low voltage (24VAC) is applied to the actuator it retracts its stem allowing the spring inside the valve body to open the valve s plug. The valve opens to its full position. The flow balancing is set on the balancing valve on the other manifold. There are manifold types where the travel of the valve stem can be adjusted. The manifold valve only opens to its set balancing position when the actuator is powered up. This allows the valve to provide the proper balancing for the circuit when it s open as well as a means of on / off flow control when an actuator is attached. In summary, the following manifold variations are used in hydronic systems; Plain manifold Manifold with plain shut off valves Manifold with provision for electrical valve actuator Manifold with flow rate indicator Manifold with balancing valve Manifold with balancing valve and flow rate indicator built-in 6-4 Locating Manifold Stations The number and placement of manifold stations in a building depends on the following: Will all floor circuits operate at the same supply water temperature? A given manifold station can only supply one water temperature to all its circuits at one time. If the system requires more than one supply water temperature at a given temperature, it will need at least two manifolds (one for each water temperature). Can all floor circuits be routed from a single manifold without excessive leader lengths? Leader length is the portion of the circuit Figure

63 SECTION 6 MANIFOLD SYSTEMS between the manifold station and the room where the circuit will release most of its heat. Such lengths should be kept to a minimum. Is the diameter of the manifolds sufficient to handle the entire system flow? To avoid noise and possible erosion due to high flow velocities, a 1" manifold should generally be limited to 11 circuits, and a 1.25" manifold limited to 15 circuits. Projects with a high number of circuits are usually better served by designing for multiple manifold stations. What locations are available for manifold stations? Manifold stations can be mounted both horizontally and vertically. In either case it is imperative to provide access to the manifold station. Try to avoid locations where furniture or other heavy or difficult to move objects would block such access. Try to find locations where the manifold access panel does not detract from the interior aesthetics of the building. In buildings with public access, the manifold stations are generally provided with lockable enclosures, or are located in areas where only authorized personnel have access. How many floor levels does the building have? It s often convenient to provide at least one manifold station on each floor level of a building. The reason is to minimize leader length in tubing circuits. Will some circuits be filled with an anti-freeze solution while others operate with water? Circuits operating with anti-freeze solutions must be supplied through different manifolds than those operating on water. Whenever possible, manifold stations should be located so that circuits can be routed away from them in several directions. This typically reduces the length of circuit leaders. In buildings with wide, spreadout floor plans, it is usually better to install two or more manifold stations (each with circuits clustered around it) rather than attempting to route all circuits back to a single location. The latter approach tends to create situations where tubing is closely packed along hallways that have very low heating requirements. Figure 6-4 shows an example of what can happen when the manifold station(s) are poorly placed. Note the concentration of tubing down the hallway. Figure

64 THE IPEX MANUAL OF MODERN HYDRONICS Manifold Mounting Manifold stations are often mounted within the hollow cavity between wall studs. The lower manifold should be mounted feet. The top manifold should be feet above the floor to allow some flexibility in the tubing from where it penetrates the floor surface to where it connects to the manifold. It s important that tubing penetrates the floor surface within the stud cavity. In the case of slab systems, the stud cavity doesn t exist at the time the manifold station is placed. Accurate measurements are essential to making sure the tubing penetrations remain inside where the wall will eventually be located. For slab type floor heating systems, some installers make a wooden tubing template block that aligns the tubing where it penetrates the slab surface with the manifold connections above. The template block is supported on two driven stakes. The top of the block should be set at the same elevation at the top of the slab. The template block is typically the same width as the wall framing and remains in place after the slab is poured. Other installers erect a temporary support for the manifold stations as shown in figure 6-5. This allows the tubing circuits to be connected to the manifold stations for pressure testing prior to the pour. After the walls are framed, the plywood backer can be removed and the manifold brackets secured to permanent framing. All tubing should be sleeved where it enters and exits a slab surface. The sleeving protects the tubing from trowel edges when the slab is finished, as well as from other physical damage over the life of the system. When the manifold station is to be mounted within a Figure

65 SECTION 6 MANIFOLD SYSTEMS wall framing cavity, that cavity must be sufficiently deep. A 2x4-framed wall with a stud thickness of 3.5 inches is a bare minimum. A 2x6-stud cavity 5.5 inches deep provides an easier installation. The installer might also look for the opportunity to fur out the interior wall of a closet to provide a deeper mounting cavity. The manifold mounting brackets should be secured to a solid wall, or a plywood panel that itself is secured directly to framing. Be sure to make the access opening large enough to install valve actuators if they are planned at the present or may be added in the future. Manifold stations can also be mounted horizontally. A good example is a manifold station secured to the underside of a framed floor deck as shown in figure 6-6. Tubing circuits from a thin-slab or tube & plate floor heating system can drop down through the sub floor and connect to the manifold station. Mounting one or more manifold stations to the underside of a framed floor with access from the basement eliminates the need for access panel in the finished space above. route tubing through shallow holes in subfloor Figure 6-6 floor joist underside insulation 6-5 Manifold Piping Options return topping pour plywood subfloor When multiple manifold stations will be operated at the same supply temperature, they should be piped in parallel as shown in figure 6-7. Never connect multiple manifold stations in series with each other. The resulting pressure drop would be very large. The downstream manifold would also operate at a lower temperature and greatly reduced heat output. Good hydronic piping design encourages the installation of valves that can isolate major system compoplywood panel manifold station supply Figure

66 THE IPEX MANUAL OF MODERN HYDRONICS nents from the balance of the system should they require service. Installing a pair of full port ball valves on the supply and return side of each manifold station to provide such isolation is considered good practice. IPEX offers such valves that thread directly to the manifolds. IPEX manifolds can be configured with adapters allowing them to be supplied using either copper tubing or large diameter Kitec pipe. Distribution piping for multiple manifold systems can be set up several ways depending on the flow requirements and routing requirement. These methods include: Trunkline piping Homerun distribution piping Parallel primary / secondary piping The concept of trunkline piping is shown in figure 6-8. Each manifold station taps into a common supply (trunk) pipe as well as a common return (trunk) pipe. Because this is a form of parallel piping, each manifold station receives the same water temperature (assuming minimal heat loss along the trunk piping). Trunkline distribution piping can be constructed of Figure

67 SECTION 6 MANIFOLD SYSTEMS either rigid metal pipe or larger diameter Kitec pipe. It can be routed through the framing cavities of the building, in a mechanical chase above the ceiling, or even under the floor slab. In the latter case, flexible Kitec PEX-AL-PEX or PEX tubing is recommended. Portions of the trunkline piping may need to be insulated to minimize heat transmission to floor areas en route to the farther manifold stations. The size of the supply trunkline pipe can generally be reduced as flow is removed at each manifold station. Likewise, the piping size of the return trunkline is usually increased as return flow is added at each trunkline. The flow velocity at any point in the trunkline piping should not exceed than 4 feet per second to minimize flow noise. Another option is to pipe each manifold as a homerun circuit as depicted in figure 6-9. A header is the mechanical room handling the supply and return flow to each manifold station. Homerun systems generally use small tubing than trunkline systems. Smaller diameter Kitec PEX-AL-PEX or PEX tubing is easier to route through confined building cavities smaller tubing, especially in retrofit applications. Homerun systems are another form of parallel piping and thus deliver the same water temperature to each manifold station. Figure

68 THE IPEX MANUAL OF MODERN HYDRONICS Another method of supplying multiple manifold systems with the same water temperature is primary/secondary piping. Figure 6-10 depicts the concept. Note that each manifold station now has its own circulator. This circulator can be smaller than a single circulator that provides flow to the entire distribution system and all manifold stations. It can also be independently controlled if necessary. A pair of closely spaced tees connects the manifold riser piping to a crossover bridge in the primary loop. This detail allows any of the manifold circulators to operate without interference with the circulator in the primary loop. The use of primary/secondary piping to supply multiple manifold stations is generally not necessary in residential and light commercial systems. However, it does provide an option to a large central pump and numerous control valves in larger industrial systems. See more details of piping systems in chapters 8 and 9. Figure Manifold Accessories IPEX also offer manifolds with built-in flow indicators / balancing valves. They allow the flow in each circuit to be read as well as adjusted. When a manifold with flow indicators / balancing valves is used, it should be installed as the return manifold. A valveless manifold can be used on the supply side. If valve actuators will also be installed, the other manifold must be valved to accommodate the loop valve actuator. Manifold stations can also be equipped with air venting options as well as fill/drain valves. A float type air vent on the top manifold assists with air removal when the system is filled. When fill / drain valves are installed each manifold station can be individually purged. These accessories are shown in figures along this chapter. 72

69 SECTION 7 PRE-ASSEMBLED CONTROL PANELS General There is an endless variety of design options for hydronic systems. Every installation is designed as a specific project using a combination of pipe, manifolds and individual components to construct a heating system. Depending on the project specifications and features and factoring in individual preferences, even similar projects can show major variations in design and components. Despite this, it is possible to find similarities and create "standard" assemblies that are versatile enough to cover these variations while using basic common principles. This is the fundamental goal of the IPEX Pre-assembled Control Panel concept Panel Design Process IPEX analyzed the similarities and the likely variations in design based on a series of specific heating applications. The goal was to offer a number of pre-designed and pre-assembled control panels that installers can choose from to match the project at hand. By looking at the details of the heating application, the appropriate supply and return manifolds and controls can be selected and assembled in a professional enclosure. The potential result would be time and money saving off-the-shelf solutions that put a professional finishing touch to almost any radiant heating application. In order to establish the final panel offering though, a number of design questions had to be addressed. Will the hydronic system operate as a closed loop system or an open loop system? What pressures will the piping system operate under? Answering these two questions narrows the selection of components considerably. How will the heat input be controlled? Do we need to control every pipe loop independently? Would zone control be more appropriate? Again, answering these questions further defines the specific components necessary for the project. 73

70 THE IPEX MANUAL OF MODERN HYDRONICS The IPEX WarmRite Control Panel product line was developed using this process, in combination with valuable feedback from the North American market place. The result is the following eleven different Control Panels (CP) Injection Mixing CP Recirculating Zone CP Recirculating Zone CP with Expansion Tank CP with Heat Exchanger Floor Warming CP Multi Zone Manifold Station Manifold Station with Circulator Manifold Station Snowmelt / Industrial CP Injection Mixing Secondary CP Isolation Module Each control panel is described in this section. However, because the panels have numerous common elements, a review of their similarities is in order. For detailed information, application notes and installation / operation manuals are available for each panel Operating Principles All panels are designed to control the average floor temperature required to compensate for ongoing heat loss. Each panel does this by cycling between heat input (on cycle) and no heat input (off cycle). During the on cycle, additional heat is added to the pipe loops to bring the floor temperature to its desired level. The ratio between the on and off cycle is proportional to the average heat needed in the floor. Simply put, if it is warm outside the heat loss is low. The on cycle is short and the off cycle is long. If the opposite is true and it is cold outside, the heat loss will be high causing the on cycle to be long and the off cycle to be short. In principle, radiant floor systems are designed so that on the coldest day of the year, the on cycle will operate 100% of the time Supply Water Temperature Most panels operate on constant supply temperature. Only the Injection Mixing Control Panel modulateschanges continuously-the supply temperature based on outdoor reset. The Control Panel with Heat Exchanger and the Floor Warming Control Panel have a built-in tempering valve to set the supply temperature. These three panels control the floor supply temperature so no external supply water temperature control is needed. All other panels rely on receiving the calculated design water temperature Space Temperature Control Most of the panels are primarily operated as a zone control mechanism. They can provide loop control if necessary, but one should always consider the way the building is used and clarify if zone control is appropriate, or if loop by loop control is needed. Loop by loop control always requires more hardware components than zone control. Designers should consider how the building is used. Who is using it? What comfort level is required? How even and constant is the required indoor temperature? What level of accuracy is required from the control system? One must first identify what is really required and design accordingly Why zone control? It is fair to say that the most fundamental requirement of every heating system is to provide constant temperature in the heated space. There are exceptions of course, but mostly a set temperature is desired throughout the heating season. The opposite of this occurs if a building needs to be heated only for a short time, then cooled and heated again. In most cases, high mass radiant floor may not be the best option for this type of heating pattern. Where radiant heating thrives is in constant temperature environments. This being the case, the fundamental requirement is to be able to set a desired temperature and allow the system to maintain it - this is what zone control does best. To clarify, zone control means that all pipe loops (or heat emitters) connected to a manifold are controlled by one thermostat or sensor. However, this does not mean that the temperature must be the same in all areas covered by the loops from a single manifold. Different temperatures can be set within the zone by adjusting the balancing valve on each loop. Adjusting the flow rate loop results in different temperatures in the areas covered by the loops Setting the Temperature All panels have a balancing valve for each pipe loop fitted on the return manifold. Most panels also have flow rate indicators on the return manifold. The desired temperature relationship can be set easily and with no additional hardware-i.e. a thermostat in every room and an actuator on every loop. This approach to temperature control works very well as long as the preference 74

71 SECTION 7 PRE-ASSEMBLED CONTROL PANELS is for a consistent temperature pattern which is not often altered. The temperature difference between the areas will remain the same unless the balancing valves are readjusted. Naturally there are applications when the temperature setting has to be changed more frequently - such as a motel where guests change every day, and with them so do individual comfort requirements. Perhaps in our own home there is a guest bedroom that is only used sporadically. In these cases, separate thermostats are required. The pipe loops serving these spaces will have valve actuators connected to the appropriate room thermostat. When the room is occupied and that thermostat calls for heat, valves open on those loops until the appropriate setting is satisfied. The provision for individual loop valves is available on all WarmRite Floor control panels designed for residential or office environments. Industrial and Secondary Injection Mixing Control Panels differ from the others in that the environments they are designed for rarely require loop by loop control. In large areas, the flow adjustment in a single loop has virtually no effect on the overall heat output. There are no sophisticated balancing or actuated valves in these panels because they are not required. All of the other control panels have been designed to accommodate individual loop by loop control when required. Every panel designed for closed loop systems has an automatic air vent on the supply manifold and a fill/drain valve on both manifolds. Each is equipped with a pressure gauge on the return manifold and two temperature gauges: one for supply and one for return water temperature. The temperature drop in the system characterizes best how the unit is operating Protection from Overheating All panels - except the manifold station - are fitted with a limit thermostat to protect the floor from overheating. Floor surface temperature should be less than 85 deg. F. for human comfort. The limit thermostat monitors the supply water temperature which is proportional to the floor surface temperature. If the supply temperature reaches the setpoint, the limit thermostat turns off the heat input. This is a factory setting based on typical concrete slab installations. When higher supply temperatures are required, it can be readjusted accordingly. See the Application Notes and Installation / Operation Manual supplied with each panel for more details. 75

72 THE IPEX MANUAL OF MODERN HYDRONICS 7-2 CONTROL PANELS Injection Mixing Control Panel Operation: This panel is designed to control supply fluid temperature by injection mixing. The WarmRite Control provides variable speed operation of an injection circulator based on outdoor air temperature. This panel is ideal when supply temperature control is required. The application of this panel is extended to control the return water temperature for conventional boilers by installing the return water temperature sensor. automatic airvent pressure / temperature gauges supply manifold limit sensor secondary circulator injection circulator When the control is in the outdoor reset mode, the speed of the injection circulator is varied to maintain a target fluid temperature in the supply manifold based on outdoor air temperature. The return manifold control can alternately be used as a set point fill/drain control. In this mode, the speed of the injection valve circulator is varied to maintain a user adjustable INJECTION MIXING CP supply fluid temperature. A room thermostat monitors the desired room temperature and turns the mixing control off when the zone(s) is satisfied. isolating valves WarmRite control The panel is operated as a single zone system by using the thermostat to activate the control. The secondary circulator operates continuously providing even heat distribution during the heat up and cool down cycles. The panel can be operated with subzones set up on a single zone panel. The system thermostat is operating the main heat input while the subzone thermostats operate the loops fitted with valve actuators. The sub zoning should not exceed more than 50% of the loops. The panel can be operated as a multiple zone system. The on/off valves located on the supply manifold are fitted with optional electrical valve actuators to control individual loops in the system. In this application, every actuator is connected to a thermostat located in the area served by the loop. When the thermostat calls for heat, the actuator opens the loop allowing flow. When all loops are satisfied, the secondary circulator is shut down and the injection control is disabled. The panel operation is controlled by closure of a dry contact. An example of devices that can provide this are: two and three wire room thermostats, programmable thermostats, set point controls, integrated building controls, etc. Balancing valves with flow indicators on the return manifold allow the user to adjust and visually monitor the flow rates of each loop. A circulator control module contains a 24V transformer, a circulator relay, a dry contact enable, and an adjustable high limit which prevents the supply fluid from exceeding the desired temperature. Valves on the supply and return manifolds allow each loop to be isolated when necessary. The optional actuators and thermostats must be ordered separately according to the project specifications. actuator module (3z) circulator control module The panel operation is controlled by closure of a dry contact. An example of devices that can provide this are: two and three wire room thermostats, programmable thermostats, set point controls, integrated building controls, etc. SUPPLY RETURN 76

73 SECTION 7 PRE-ASSEMBLED CONTROL PANELS Recirculating Zone Control Panel Operation: This panel is designed as a manifold station that provides constant circulation in the distribution system. There is no supply water temperature control in the panel. The panel operates primarily as a single zone system maintaining the average space temperature. A thermostat and a diverting valve control the heat input. It cycles the heat-input on/off to match the average heat load requirement in the zone. Fluid circulates from the heat source to the panel and through the floor piping. When the zone is satisfied, the diverting valve closes the path to the heat source and removes the external enable signal. The fluid continuously circulates in the floor piping, providing even heat distribution both on heat up and cool down cycles. Balancing valves with flow indicators on the return manifold allow the user to adjust and visually monitor the flow rates of each loop. A circulator control module contains a 24V transformer, a circulator relay, a dry contact enable, and an adjustable high limit which prevents the supply fluid from exceeding the desired temperature. Valves on the supply and return manifolds allow each loop to be isolated when necessary. pressure / temperature gauges supply manifold fill/drain valve purge valve limit sensor return manifold RECIRCULATING ZONE CP actuator module (3z) circulator circulator control module diverting valve isolating valves The panel operation is controlled by closure of a 24V dry contact. An example of devices that can provide this are: two and three wire room thermostats, programmable thermostats, set point controls, indoor/outdoor reset controls, integrated building controls, etc. SUPPLY RETURN 77

74 THE IPEX MANUAL OF MODERN HYDRONICS Recirculating Zone Control Panel with Expansion Tank Operation: This panel is designed as a manifold station that provides constant circulation in the distribution system. There is no supply water temperature control in the panel. The panel operates primarily as a single zone system maintaining the average space temperature. A thermostat and a diverting valve control the heat input. It cycles the heat-input on/off to match the average heat load requirement in the zone. Fluid circulates from the heat source to the panel and through the floor piping. When the zone is satisfied, the diverting valve closes the path to the heat source and removes the external enable signal. The fluid continuously circulates in the floor piping, providing even heat distribution both on heat up and cool down cycles. Balancing valves with flow indicators on the return manifold allow the user to adjust and visually monitor the flow rates of each loop. A circulator control module contains a 24V transformer, a circulator relay, a dry contact enable, and an adjustable high limit which prevents the supply fluid from exceeding the desired temperature. Valves on the supply and return manifolds allow each loop to be isolated when necessary. The panel operation is controlled by closure of a 24V dry contact. An example of devices that can provide this are: two and three wire room thermostats, programmable thermostats, set point controls, indoor/outdoor reset controls, integrated building controls, etc. pressure / temperature gauges supply manifold fill/drain valve expansion tank limit sensor return manifold actuator module (3z) circulator circulator control module shut off valve diverting valve isolating valves RECIRCULATING ZONE CP with EXP. TANK Installed By / Installe Par SUPPLY RETURN 78

75 SECTION 7 PRE-ASSEMBLED CONTROL PANELS Control Panel with Heat Exchanger Operation: This panel is designed to separate the secondary system fluid from the primary system fluid by utilizing a plate heat exchanger, and is recommended for applications that use an open loop system as the heat source or in applications where a water/glycol mixture is used in the secondary heating loop. The secondary system is filled during installation and operates as a closed loop circuit. The panel comes with an expansion tank and relief valve for the secondary side of the system. The design supply fluid temperature in the primary loop is set with a tempering valve. The panel is operated as a single zone system by using a thermostat to activate the primary circulator. The secondary circulator operates continuously providing even heat distribution during the heat up and cool down cycles. The panel can also be operated as a multiple zone system. The on/off valves located on the supply manifold can be fitted with optional electrical valve actuators to control individual loops in the system. In this application, every actuator is connected to a thermostat located in the area served by the loop. When the thermostat calls for heat, the actuator opens the loop allowing flow. When all loops are satisfied, the primary and secondary circulators are shut down. pressure relief valve pressure / temperature gauges automatic airvent shut off valve supply manifold purge valve limit sensor expansion tank return manifold CP with HEAT EXCHANGER secondary circulator shut off valve actuator control (x3) circulator control module heat exchanger manual airvent isolating valves primary circulator tempering valve Balancing valves with flow indicators on the return manifold allow the user to adjust and visually monitor the flow rate of each loop. The circulator control module contains a 24V transformer, a circulator relay, a dry contact enable, and an adjustable high limit which prevents the supply fluid from exceeding the desired temperature. Valves on the supply and return manifolds allow each loop to be isolated when necessary. The optional actuators and thermostats must be ordered separately according to project specifications. The panel operation is controlled by closure of a 24V dry contact. An example of devices that can provide this are: two and three wire room thermostats, programmable thermostats, set point controls, indoor/outdoor reset controls, integrated building controls, etc. SUPPLY RETURN 79

76 THE IPEX MANUAL OF MODERN HYDRONICS Floor Warming Control Panel Operation: This panel is designed to operate floor warming and basic heating systems. This panel incorporates non-ferrous components to allow use with the domestic water supply where permitted. programmable thermostat with slab sensor pressure / temperature gauges actuator module (3z) circulator control module The panel is supplied with a programmable thermostat to sense slab temperature or air temperature depending on the application. In a floor warming application the thermostat is programmed to sense slab temperature. In a space heating application it is programmed to sense air temperature, or optionally air and slab temperature. The thermostat can be programmed to circulate the water throughout the year to prevent stagnation when utilizing a domestic water heat source. A built in tempering valve allows control of supply water temperature. supply manifold purge valve limit sensor return manifold FLOOR WARMING CP circulator tempering valve isolating valves The panel is operated as a single zone system by using the thermostat to activate the circulator. The panel can be operated as a multiple zone system. The on/off valves located on the supply manifold can be fitted with optional electrical valve actuators to control individual loops in the system. In this application every actuator is connected to a thermostat located in the area served by the loop. If periodic circulation to avoid stagnation is required, all thermostats on the system must be programmable thermostats with timer capabilities. Balancing valves with flow indicators on the return manifold allow the user to adjust and visually monitor the flow rate of each loop. The circulator control module contains a 24V transformer, a circulator relay, a dry contact enable, and an adjustable high limit that prevents the supply water from exceeding the desired temperature. Valves on both the supply and return manifolds allow for isolation of the loop when necessary. The panel operation is controlled by closure of a 24V dry contact. The panel comes complete with a programmable thermostat, but also may be controlled by devices such as: two and three wire room thermostats, set point controls, indoor/outdoor reset controls, integrated building controls, etc. RETURN SUPPLY 80

77 SECTION 7 PRE-ASSEMBLED CONTROL PANELS Multi Zone Manifold Station Operation: This panel is used as multiple zone system. The on/off valves located on the supply manifold are fitted with electrical valve actuators to control individual loops in the system. Every actuator must be connected to a thermostat located in the area served by the loop(s). When the thermostat calls for heat, the actuator opens the loop allowing flow. The pressure balancing bypass valve equalizes the changing head loss conditions as various loops open and close. When all loops are satisfied the dry contact in the circulator control module opens. Balancing valves with flow indicators on the return manifold allow the user to adjust and visually monitor the flow rates of each loop. A circulator control module contains a 24V transformer, a circulator relay, a dry contact enable, and an adjustable high limit which prevents the supply fluid from exceeding the desired temperature. Valves on the supply and return manifolds allow each loop to be isolated when necessary. The thermostats must be ordered separately according to the project specifications. automatic airvent pressure / temperature gauges actuators fill/drain valve supply manifold actuator module (x3) actuator actuator module module (x3) (x3) limit sensor actuator module (x3) circulator control module Each actuator's operation is controlled by closure of a 24V dry contact. An example of devices that can provide this are: two and three wire room thermostats, programmable thermostats, set point controls, integrated building controls, etc. pressure balancing bypass return manifold fill/drain valve MULTI ZONE MANIFOLD STATION isolating valves SUPPLY RETURN 81

78 THE IPEX MANUAL OF MODERN HYDRONICS Manifold Station with Circulator Operation: This panel is designed as a basic manifold station. The panel is operated as a single zone system by using a thermostat to activate the circulator. The panel can also be used as multiple zone system. The on/off valves located on the supply manifold can be fitted with optional electrical valve actuators to control individual loops in the system. In this application, every actuator is connected to a thermostat located in the area served by the loop. When the thermostat calls for heat, the actuator opens the loop allowing flow. When all loops are satisfied the circulator is shut down. fill/drain valve pressure / temperature gauge automatic airvent supply manifold limit sensor Balancing valves with flow indicators on the return manifold allow the user to adjust and visually monitor the flow rates of each loop. A circulator control module contains a 24V transformer, a circulator relay, a dry contact enable, return manifold and an adjustable high limit which prevents the supply fluid from exceeding the desired temperature. Valves on the supply and return manifolds fill/drain valve MANIFOLD STATION with CIRCULATOR allow each loop to be isolated when necessary. The optional actuators and thermostats must be ordered separately according to the project specifications. actuator module (x3) circulator control module circulator isolating valves The panel operation is controlled by closure of a 24V dry contact. An example of devices that can provide this are: two and three wire room thermostats, programmable thermostats, set point controls, indoor/outdoor reset controls, integrated building controls, etc. RETURN SUPPLY 82

79 SECTION 7 PRE-ASSEMBLED CONTROL PANELS Manifold Station Operation: This panel is designed as a basic manifold station. The panel is operated as a single zone system by using a thermostat to activate the external zone valve or a circulator. The panel can also be used with limited number of subzones. The on/off valves located on the supply manifold can be fitted with optional electrical valve actuators to control individual loops in the system. In this application, every actuator is connected to a thermostat located in the area served by the loop. When the thermostat calls for heat, the actuator opens the loop allowing flow. Balancing valves with flow indicators on the return manifold allow the user to adjust and visually monitor the flow rates of each loop. The unit has no integral zone control device. When a zone valve or circulator is attached to the manifold station a Circulator Control Module has to be fitted in the system. This controls the zone valve or circulator and the loop valve actuators for the subzones. The circulator control module fill/drain valve fill/drain valve pressure / temperature gauge automatic airvent supply manifold return manifold limit sensor MANIFOLD STATION isolating valves contains a 24V transformer, a circulator relay, a dry contact enable, and an adjustable high limit which prevents the supply fluid from exceeding the desired temperature. Valves on the supply and return manifolds allow each loop to be isolated when necessary. The optional actuators and thermostats must be ordered separately according to the project specifications. SUPPLY RETURN 83

80 THE IPEX MANUAL OF MODERN HYDRONICS Snowmelt / Industrial Control Panel Operation: This panel is designed to operate snowmelt or industrial heating systems, which are usually designed with pipe loops of equal length. In these circumstances individual loop flow rate adjustment is not required, nor is recirculation necessary. An external control turns the circulator on when heat is required. Valves on the supply and return manifolds are used if flow rate compensation is required. They may also be used to isolate each loop for installation and servicing ease. A pressure / temperature actuator circulator circulator control module gauge module control contains a 24V transformer, a circulator relay, a dry contact automatic enable, and an adjustable high airvent (3z) module limit which prevents the supply fluid from exceeding the desired temperature. supply manifold limit sensor The panel operation is controlled by closure of a 24V dry contact. An example of devices that can provide this are: two and three wire room thermostats, programmable thermostats, set point controls, indoor/outdoor reset controls, snow melt controls, integrated building controls, etc. pressure relief valve fill/drain valve return manifold SNOWMELT / INDUSTRIAL CP circulator isolating valves SUPPLY RETURN 84

81 SECTION 12 DESIGNING MULTIPLE-LOAD HYDRONIC SYSTEMS Injection Mixing Secondary Control Panel Operation: This panel is designed to function as a remote secondary circuit of an injection mixing system to heat large commercial/industrial spaces. This design concept takes advantage of the high temperature drop across the injection bridge which allows for low flow rates. The reduced flow rates in turn allow the use of smaller pipe sizes from the boiler room to the remotely mounted panel. Large commercial/industrial spaces often require multiple remotely mounted manifolds. This panel allows a single WarmRite Control and injection circulator to provide the required temperature fluid to all panels, eliminating the need for multiple controls. pressure / temperature gauge automatic airvent actuator module (x3) circulator control module The secondary circuit in the panel constantly circulates the fluid in the floor loops. The room thermostat provides a call for heat to the centrally located WarmRite control. supply manifold limit sensor circulator Balancing valves on the supply and return manifolds are used if flow rate compensation is required. They may also be used to isolate a loop when necessary. A circulator control module contains a 24V transformer, a circulator relay, a dry contact enable, and an adjustable high limit which prevents the supply fluid from exceeding the desired temperature. fill/drain valve return manifold INJECTION MIXING SECONDARY CP secondary mixing tees isolating valves SUPPLY RETURN 85

82 THE IPEX MANUAL OF MODERN HYDRONICS Isolation Module Operation: This module is designed to isolate the liquid used in the heating loop from the liquid used in the heat source. For example, a snowmelt system operating with water-glycol mixture is connected to a heat source operating with water or separating a heating system from a domestic water heat source. The primary side of the heat exchanger is connected to the heat source. The primary circulator and the isolating valves are included in the panel. The secondary side contains an expansion tank, pressure relief valve, and isolating valves. Each circuit is monitored with a pressure / temperature gauge. A circulator control module contains a 24V transformer, a circulator relay, a dry contact enable, and an adjustable high limit that prevents the supply fluid from exceeding the desired temperature. The panel operation is controlled by closure of a 24V dry contact. An example of devices that can provide this are: two and three wire room thermostats, programmable thermostats, set point controls, indoor/outdoor reset controls, integrated building controls, etc. exp. tank supply pressure / temperature gauges limit sensor pressure relief valve return secondary heat exchanger return circulator control module primary circulator supply primary SUPPLY S RETURN P RETURN P SUPPLY 86

83 SECTION 8 DISTRIBUTION SYSTEMS FOR HYDRONIC HEATING There are several methods of transporting water from a hydronic heat source to one or more heat emitters. The method used depends on: How much water has to be moved? Can the heat emitters operate properly at different water temperatures? Do some portions of the piping system need to operate as different zones? Are there several circulators that must operate simultaneously? What type of pipe will be used to convey heated water to the heat emitters? This section examines several classic hydronic distribution system configurations. It also discusses several unique ways to use PEX-AL-PEX pipe to create distribution systems that are easy and fast to install, as well as efficient to operate. 8-1 Series Loop Systems The simplest way of connecting two or more hydronic heat emitters is in a series loop. Heated water flows into the first heat emitter, gives up some heat, exits that heat emitter and enters the next one in the loop. An example of a series piping loop using composite piping to connect several fin-tube baseboards together is shown in Figure 8-1. Series piping circuits, although simple to build do have a number of limitations. Chief among these limitations is the lack of individual heat output control for each heat emitter. Series loops should be limited to a building area that can be controlled as a single zone. Avoid series circuits if one or more of the heat emitters is located in a room with high internal heat gains compared to other rooms. 87

84 THE IPEX MANUAL OF MODERN HYDRONICS Figure 8-1 If the water temperature supplied to a series loop is changed to increase or decrease the heat output of one heat emitter, the output of all other heat emitters on the loop will be effected. This also holds true if one attempts to adjust heat output by changing the flow rate through the loop. Another potential limitation of series loop is excessive head loss (e.g. pressure drop). In a series loop the head losses (pressure drops) of each heat emitter and interconnecting piping add together. Too many heat emitters in series could lead to high pressure drops and low flow rates. This often shows up as under heated rooms near the end of the loop. Series loops containing several heat emitters should be designed to accommodate the drop in water temperature from one heat emitter to the next. If the flow rate in the circuit is known, the temperature drop across each heat emitter can be determined using formula 8-1: Where: T = Temperature drop across the heat emitter (deg. F) Q = Rate of heat output by the heat emitter (Btu/hr) f = Flow rate in the circuit (in gpm) 500 a constant for water (use 479 for 30% and 450 for 50% glycol) For example: Assume water enters a length of fin-tube baseboard at 170 deg. F. and 2 gpm. The baseboard releases heat at a rate of 10,000 Btu/hr. What is the outlet temperature from the baseboard? T= Q 500 x f = 10, x 2 = 10ºF Formula 8-1 T = Q 500 x f Solution: Therefor the water exits at = 160 deg. F. Formula 8-1 can be used sequentially to determine the 88

85 SECTION 8 DISTRIBUTION SYSTEMS FOR HYDRONIC HEATING temperature drop from one heat emitter to the next. Remember that as the water temperature drops in the downstream direction the size (or length) of the heat emitter needed for a given heat output increases. 8-2 Home Run Distribution Systems The ability of PEX-AL-PEX extends far beyond radiant panel heating systems. Its ability to handle relatively high water temperatures combined with ease of installation makes it ideal for piping traditional hydronic heat emitters such as fin-tube baseboard, cast-iron radiators and baseboard, and panel radiators. The concept for a home run piping system is shown in figure 8-2. It employs the same piping and manifold components used for radiant panel systems. The difference is that the tubing circuits are not part of the heat emitter. Instead, they carry heated water to and from individual heat emitters. In a home run system each heat emitter has its own supply and return tube. This allows each heat emitter to be supplied with approximately the same water temperature. The drop in water temperature associated with a series loop system is no longer an issue. Each heat emitter connected to the manifold can be sized at the same water temperature. Since the heat emitters don t have to be up sized to compensate for reduced water temperature the overall cost of the heat emitters selected may be reduced. Homerun systems also allow each circuit to be controlled as an independent zone. When each room is served by its own homerun circuit the temperature of each room can be adjusted as desired. Unoccupied rooms can be set at low temperatures to conserve fuel. Heat output to a room that experience solar heat gains can be interrupted when necessary without compromising comfort in other rooms. The temperature in bedrooms can be reduced during sleeping hours if desired, while bathrooms can remain warm for showers and baths. One way of providing room-by-room zone control is by adding low voltage electric valve actuators to the valves on the manifold. These actuators are controlled by the thermostats in each room. When the room thermostat calls for heat it sends a 24 volt AC signal to the associated actuator. The actuator then opens the manifold valve to which it is attached. An isolated end switch with the valve actuator provides a contact that is used to turn on the circulator and heat source. Non-electric thermostatic radiator valves (TRVs) can also be used in conjunction with a homerun distribution system to provide individual temperature control in each room. TRVs adjust the flow rate of heated water through the heat emitters to regulate heat output. They do not have the ability to signal for circulator or boiler operation. In this type of distribution system the circu- Figure

86 THE IPEX MANUAL OF MODERN HYDRONICS lator runs continuously throughout the heating season. The water temperature supplied to the heat emitters is often regulated by an outdoor reset control. The colder it is outside the warmer the water temperature. Still another benefit of homerun distribution systems is the reduced pressure drops they create in comparison to a series piping loop. Lower pressure drops often allow a smaller, less power consuming circulator to be used. This saves not only on installation cost, but also on operating cost over the long life of the system. When designing a homerun distribution system keep in mind that some hydronic heat emitters such as panel radiators and lengths of fin-tube baseboard can be sized to operate with temperature drops as high as 40 deg. F. under design load conditions. Such high temperature drops allow significant reductions in the flow rate supplied to the heat emitters. This in turn can allows the use of small tubing such as 3/8 Kitec PEX- AL-PEX for the homerun circuits. For example, a panel radiator delivering 10,000 Btu/hr with 180 deg. F inlet, and 140 deg. F. outlet water temperature only needs about 0.5 gpm of flow. This could easily be handled by 3/8 tubing. Such small diameter tubing is easily routed through framing cavities, even cavities that are closed off. In general, if a piece of electrical cable can be pulled through the building from one location to another, so can a length of small diameter composite tubing. This makes the homerun approach ideal for retrofit jobs where framing cavities may have limited access. When individual circuit control is used, a differential bypass valve should be installed across the manifold as shown in figure 8-2. It provides a flow bypass that prevents the circulator from dead heading when all the manifold valves are closed. Adjust the knob on the differential pressure bypass valve so it just begins bypassing flow when all the zone circuits are on, then increase the pressure setting slightly. As the individual homerun circuits close off the bypass valve will take an increasing percentage of the manifold flow and prevent the circulator from imposing a high pressure differential on the circuits that remain active. 8-3 Parallel ( 2-pipe ) Distribution Systems Another hydronic distribution system that supplies approximately the same water temperature to each heat emitter is called a parallel (or 2-pipe ) system. In this type of system, each heat emitter is piped into a crossover bridge that crosses from a supply main to a return main. Direct Return Piping: One form of a parallel (2-pipe) distribution system is specifically called a direct return system. An example of the piping arrangement is shown in figure 8-3. Figure

87 SECTION 8 DISTRIBUTION SYSTEMS FOR HYDRONIC HEATING Figure 8-4 Notice that the crossover bridge closest to the supply side of the heat source and circulator is also the closest to the return end of the system. The farther out the other crossover bridges are the longer the flow path of the circulating water. To obtain the proper flow rate through each heat emitter a flow balancing valve must be installed in each crossover bridge. The amount each balancing valve is closed depends on the intended flow rate through each heat emitter as well as its position on the mains. Although it is possible to calculate the necessary Cv setting of each balancing valve this is seldom done. Instead, the valves are set through a trial and error process until the heat outputs of all heat emitters are acceptable. Parallel direct-return distribution systems can be constructed of Kitec PEX-AL-PEX pipe. Larger diameter composite piping can be used to create the mains, while small pipe sizes can be used to create the rungs. Notice how the pipe size of the mains decreases as the distribution system expands away from the mechanical room. Reverse Return Piping: Another variation on the parallel piping concept is called a reverse return system. An example is shown in figure 8-4. In a reverse return system the first crossover bridge attached to the supply main is, in effect, the last to be attached to the return main. This arrangement helps equalize the piping path length through each heat emitter. This in turn help naturally balance flow through the system, especially with the attached heat emitters have similar flow resistance. Because of its ability to be self balancing reverse return systems are often preferred over direct return systems. The optimal arrangement of a parallel reverse return circuit within a building is shown in figure 8-5. Notice that the distribution system makes a loop around the building rather than a dead end at the farthest point out. 8-4 Primary/Secondary Distribution Systems The concept of primary / secondary (P/S) piping dates back to the 1950s when it was applied mostly for larger commercial systems, especially chilled water cooling applications. However, renewed interest in radiant floor heating, combined with increasingly sophisticated residential and light commercial applica- 91

88 THE IPEX MANUAL OF MODERN HYDRONICS Figure 8-5 tions prompted designers to look for a piping method more flexible and forgiving than the standard 2-pipe system. They soon rediscovered the elegant simplicity of primary / secondary piping, and were able to successfully integrated with modern controls. Today method of piping is rapidly becoming the standard setter as the backbone upon which to build modern multi-load / multi-temperature hydronic systems. The fundamental concept of a P/S system is to uncouple the pressure differential established by any given circulator, from that established by other circulators in the same system. P/S piping allows each circulator in the system to operate with virtually no tendency to induce flow, or even disturb flow, in circuits other than it s own. In effect each circulator thinks it s circuit is the only circuit in the system. This allows a number of circulators with different head and flow rate characteristics to operate simultaneously without interfering with each other. The Primary Loop: All primary /secondary systems have a primary loop that serves as the hot water bus bar for one or more secondary circuits. An example of a simple primary circuit is shown in figure 8-6. The function of the primary circuit is to deliver hot water to each of the secondary circuit attached to it. Figure

89 SECTION 8 DISTRIBUTION SYSTEMS FOR HYDRONIC HEATING Figure 8-7 The primary circulator produces flow in the primary loop only, and is NOT intended to create or even assist with flow in any of the secondary circuits. Each secondary circuit is attached to the primary circuit using a pair of closely spaced tees as shown in figure 8-7. Since the pressure drop between the closely spaced tees is almost zero, there s virtually no tendency for flow in the primary circuit to create flow in the secondary circuit. When a secondary circulator is turned on, it establishes its own pressure differential in its secondary circuit. This in turn draws flow from the upstream tee in the primary loop, sends the flow through the secondary circuit, and returns it to the downstream tee in the primary loop. The primary loop functions as the source of hot water as well as a return path, instead of direct piping connections to the heat source itself. The primary loop also becomes the pressure reference point for the secondary circuits. It acts as the point of connection to an expansion tank for each of the secondary circuits. Because of this, it s important that each secondary circulator pumps into its associated secondary circuit, (e.g. away from the expansion tank reference point). This allows the pressure in the secondary circuit to increase when the secondary circulator operates. Series Primary Loops: A series primary loop is created when two or more secondary circuits are arranged in sequence along the primary loop as shown in figure 8-8. When designing a series primary loop it s necessary to account for the temperature drop associated with each operating secondary circuit. Formula 8-1, repeated below, can be used for this purpose. Formula 8-1 T = Q 500 x f Where: T = Temperature drop in the primary loop across the tees of an operating secondary circuit (deg. F) Q = Rate of heat delivery to the secondary circuit (Btu/hr) f = Flow rate in the primary circuit (in gpm) 500 a constant for water (use 479 for 30% and 450 for 50% glycol) 93

90 THE IPEX MANUAL OF MODERN HYDRONICS Figure 8-8 The heat emitters in the various secondary circuits need to be sized for the water temperature available to them based on where they connect to the primary circuit. The farther downstream a given secondary circuit connects to the primary loop, the lower the water temperature it has available (assuming the upstream secondary circuits are operating). It s usually best to place secondary circuits with higher temperature requirements near the beginning of the primary circuit, and those that can work with lower water temperatures near the end. If a conventional boiler is used as the heat source always check that the water temperature at the end of the primary loop (when all loads are operating) is above the dew point of the boiler s exhaust gases. Minimum return temperatures of 130 deg. F. for gas-fired boilers, and 150 deg. F. for oil-fired boilers are often suggested. Preventing Heat Migration: It s very important to protect secondary circuits from off-cycle heat migration (e.g. the undesirable flow of hot water into a secondary circuit when its circulator is off). This migration is causes by two factors. First there s the natural tendency of hot water to thermosiphon through an unblocked piping loop located above the heat source. Hot water is lighter than cool water. Given an unblocked piping path that rises above the heat source this difference in buoyancy will maintain a weak, but persistent flow. Under such conditions the piping loop and any heat emitter it contains serves as a heat dissipater that could easily overheat spaces that simply don t need any heat input at the time. Another factor that causes heat migration is the fact that the pressure drop between the closely-spaced tees where the secondary circuit connects to the primary loop is not quite zero. The slightly higher pressure at the upstream tee will try to push some hot water into the secondary circuit. Every secondary circuit in a P/S system must include detailing to prevent heat migration when its circulator is off. One method is to install a flow-check valve (which has a weighted plug) on both supply and return 94

91 SECTION 8 DISTRIBUTION SYSTEMS FOR HYDRONIC HEATING risers of the secondary circuit. The opening pressure of these valves is about 1/4 psi. This is sufficient to prevent buoyancy forces from setting up a thermosiphon flow pattern when the secondary circulator is off. A spring-loaded check valve is an acceptable alternative to a flow-check in these locations. These details are shown in figure 8-9. Two other options exist for the return riser of a secondary circuit. One is the under slung thermal trap shown in figure 8-9. Another is a swing check. Neither of these can stop forward flow caused by buoyancy forces and therefore should only be used on the return side of a secondary circuit. Purging: The closely spaced tees connecting a secondary circuit to the primary circuit make it difficult to purge the secondary circuits by forcing water around the primary loop. The solution is to install separate purging valves on the return side of each secondary circuit as shown in figure 8-9. During purging the ball valve is closed forcing pressurized make-up water in the desired direction through the secondary circuit as air is blown out through the open hose bib. Sizing the Primary Circulator: Every circulator in a P/S system functions as if it were installed in an isolated circuit. The primary circulator does not assist in moving flow through any of the secondary circuits, or vice versa. The function of the primary loop is simply to convey hot water from the heat source around the primary loop. In the process the water temperature drops by some intended design T. The flow rate necessary to deliver the output of the Figure

92 THE IPEX MANUAL OF MODERN HYDRONICS heat source using a selected temperature drop can be found using formula 8-2: Formula 8-2 Where: f primary = f primary = Flow rate in the primary circuit (gpm) Q = Heat output rate of the heat source (Btu /hr) T = Intended temperature drop of the primary circuit (deg. F.) 500 = A constant for water at an average temperature of 140ºF., (use 479 for 30% glycol, 450 for 50% glycol) For example: Assume a primary circuit is connected to a boiler having an output rating of 100,000 Btu/hr. The intended temperature drop of the primary loop with all secondary loads operating is 20 deg. F. What is the necessary primary loop flow rate? Solution: f primary = Q 500 x T The designer now chooses a piping size and estimates the head loss of the primary loop based on this flow rate. A circulator capable of providing the necessary head at the calculated flow rate is then selected. Notice there was no need to examine the specifics of the secondary circuits when selecting the primary loop circulator. Selecting a high temperature drop ( T) for the primary circuit results in lower flow rates, and often reduces primary loop pipe size. It may also reduce the size of the primary loop circulator. However, selecting a large temperature drop also implies lower supply water temperature to secondary circuits located farther downstream along the primary loop. This is fine for systems using both high temperature and lower temperature heat emitters provided the higher temperature secondary circuits are located near the beginning of the primary loop, while those with lower water temperature requirements are located near the end. Split Primary Circuits: Q 500 x T = 100, x 20 = 10gpm When the same water temperature needs to be supplied to each of several secondary circuits, the primary circuit can be split into several parallel crossover bridges as shown in figure Each crossover bridge should have a flow-balancing valve so flow rates can be proportioned to the loads being supplied. See figure For example, if one crossover bridge serves a load that has twice the heating requirement of a load on another crossover bridge, that bridge should have about twice the flow rate of the other. The pipe sizes of the crossover bridges can even be different if necessary depending on the flows needed. The split primary loop approach is especially helpful when several of the secondary circuits need to operate within a narrow water temperature range. Secondary Circuit Design: Figure 8-10 The design of secondary circuits is not limited to a series loop of heat emitters. Any piping design that could be connected to a boiler can also be connected to the closely spaced tees at the P/S interface. Some examples are shown in figure The secondary circuit risers can even be treated as headers from which two or more independently controlled zone circuits can begin and end. Another option is to configure the secondary circuit as a two pipe direct- or reverse-return subcircuit. The secondary circuit can also be set up as a home run subsystem use several independent circuits of Kitec pipe to supply individual heat emitters. Secondary circuits can also contain a mixing device allowing them to operate at lower water temperatures than the primary loop. Examples are shown in figure

93 SECTION 8 DISTRIBUTION SYSTEMS FOR HYDRONIC HEATING Figure 8-11 Figure

94 THE IPEX MANUAL OF MODERN HYDRONICS When a mixing device is used to reduce the supply temperature in the secondary circuit the primary loop creates a second mix point that boosts water temperature returning to the heat source. With the proper controls, this configuration can reliably protect a conventional boiler against sustained flue gas condensation. The possibilities of what can be constructed using the piping techniques discussed in this section are nearly endless. The next section will show you how to apply these piping techniques when necessary to create sophisticated multi-load / multi-temperature systems. Figure

95 SECTION 9 DESIGNING MULTIPLE-LOAD HYDRONIC SYSTEMS 9-1 Introduction There was a time when residential hydronic heating consisted of 1 to 3 zones of baseboard piped from a single boiler. Space heating was always considered the main load. Domestic hot water was sometimes provided using a tankless coil suspended in a boiler that had to remain hot 24 hours a day, 365 days a year. Today, residential and light commercial hydronic systems are often more sophisticated than those used in larger buildings. In addition to multiple methods of space heating, these systems almost always provided domestic hot water heating. Many go further to provide snow-melting, intermittent garage heating and perhaps even warm the backyard swimming pool. This section shows how an integrated multi-load hydronic system can be assembled. It will look at ways to configure the heat source, pipe the system and even select control strategies that allow all the loads to operate in an optimal manner. 9-2 Benefits of an Integrated Multi-load System Hydronic systems are unmatched in their ability to merge several loads into a single integrated system in which a single heat plant supplies all loads. This approach increases the duty cycle of the heat plant relative to the individual duty cycles of several direct-fired appliances. Higher duty cycle yields higher seasonal efficiency and lower fuel consumption. A single heat plant eliminates the need for multiple dedicated heat sources, each with their own fuel supply, ventilation, exhaust, electrical, space and maintenance requirements. Since all heat source equipment can be located in one area, service personnel do not have to move throughout the building to access it. The mechanical room can be properly vented. The chance of carbon monoxide spillage 99

96 THE IPEX MANUAL OF MODERN HYDRONICS is reduced. Should such spillage occur, there is a better chance of detecting it prior to its spread through the building. The heat plant used in most integrated multi-load hydronic systems is one or more gas- or oil-fired boiler(s). Water in the temperature range of 180 to 200 degrees F. is produced for loads such as fin-tube convectors and domestic water heating. Medium and low temperature water for other loads is achieved by blending hot water with cooler return water using one or more of the mixing strategies discussed in section 6. Integrated multi-load hydronic systems can also take advantage of load diversity. It s the concept that all loads in a multiple load system almost never demand full heat input at the same time. Thus, it s almost never necessary to size the heat plant equal to the total of all loads operating simultaneously at maximum output. In the unlikely event all loads did call for maximum heating at the same time the system s controls can invoke prioritized load shedding. Heat input to lower priority loads like garage floor heating and pool heating can be temporarily interrupted so heat can be redirected to higher priority loads like domestic hot water production and space heating. When the high priority loads are satisfied, heat output is directed to making up the heat deficits of the low priority loads. The large thermal mass of slab-type floor heating and swimming pools make boiler sizing more a matter of how much energy can be delivered over a period of several hours, rather than how much instantaneous capacity is available. 9-3 Multiple Boiler Systems In some multi-load systems, a single boiler can supply all the loads. For larger capacity systems (or systems in which the load can change dramatically from one minute to the next) a multiple boiler system is an ideal solution. Boilers attain their highest efficiency when running continuously. Multiple boiler systems in which each boiler is individually controlled as a stage of heat input encourage longer on-cycles for the individual boilers and thus higher overall heat plant efficiency. The owner is also likely to save thousands of dollars over the life of the system because of this higher efficiency. Longer duty cycles also yield longer life and reduced maintenance for components such as hot surface igniters, oil burners and relays. Other benefits of multiple staged boiler systems Figure

97 SECTION 9 DESIGNING MULTIPLE-LOAD HYDRONIC SYSTEMS include: The ability to provide partial heat delivery if one boiler is down for servicing. The use of smaller/lighter boilers that are easier to install, especially in retrofit situations. The ability to place all the heat generation in one location and thus eliminate several other dedicated heat sources distributed through the building. To achieve maximum efficiency, the multiple boiler system should be designed so heated water is NOT circulated through unfired boilers. Doing so uses the unfired boiler(s) as heat dissipaters. Although there are several possible ways to achieve this, the piping shown in figure 9-1 is considered by many to be the simplest and most efficient approach. In this configuration, each boiler s circulator operates only when that boiler is firing. The flow check valves prevents gravity circulation or reverse flow at all other times. This arrangement also supplies each boiler with the same (lowest possible) return temperature. The cooler each boiler operates, the higher its efficiency. System controls are configured to prevent any of the boilers from operating at temperatures low enough to cause sustained flue gas condensation. Multiple-boiler systems are usually operated by a staging control. Such controls have the ability to determine the appropriate water temperature for the load(s) that are active at any given time, and then steer the water temperature supplied to the distribution system toward this target temperature. For space heating loads the water temperature is often reset based on outdoor temperature as discussed in section 6. When the load is supplied through a heat exchanger (such as with snow melting, pool heating, or domestic water heating), the control is usually configured to deliver a high (but fixed) water temperature regardless of the outdoor temperature. Figure 9-2 shows how a 3-boiler system can be piped to provide heat to both domestic water heating and space heating loads. Notice the closely-spaced tees that connect the boiler Figure

98 THE IPEX MANUAL OF MODERN HYDRONICS manifold piping to the distribution system. This piping arrangement allows the boiler system to hand off heat to the distribution system without interference between the various circulators. Also notice the placement of the supply temperature sensor for the boiler staging control. This placement is necessary because the boiler circulators will only operate when the boilers are being called for by the boiler staging control. Do not place the supply sensor on the boiler manifold piping since there will be times when the boiler circulators will be off, yet a load still exists in the distribution system. Without flow through the boiler, manifold piping heat cannot be delivered to the distribution system. 9-4 Providing Domestic Hot Water Most integrated multi-load hydronic systems supply domestic hot water using an indirect water heater. Upon a call for domestic water heating, hot boiler water is circulated through a heat exchanger built into the hot water storage tank. One method of piping an indirect water heater is as a secondary circuit to a primary loop as shown in figure 9-3A. If this arrangement is used, the DHW tank should be the first secondary circuit connected to the primary loop. This provides the hottest water to the tank s heat exchanger for fast recovery. Always install a flow-check valve in the supply line leading to the tank s heat exchanger. This prevents the possibility of heat migration due to buoyancy forces and/or slight pressure differentials between the closelyspaced tees connecting the tank s heat exchanger to the primary loop. It also prevents hot water in the tank from establishing a convective cooling loop when the circulators are off. Piping the DHW tank as a secondary circuit requires hot water to flow around the entire primary loop whenever there s a call for domestic water heating. To minimize piping heat loss, this piping arrangement should only be used for short primary loops that run within the mechanical room. Preferably, the primary loop and DHW secondary loop piping will be insulated to further reduce piping heat loss. The system designer should also take note that if the DHW tank is not operated as a priority load, all downstream secondary circuits will receive reduced water temperature while the DHW load is operating. The heat emitters in the downstream secondary circuits should be sized to accommodate this reduced water temperature if extended demand for domestic water heating is likely to occur simultaneously with maximum space heating demand. Another piping option for connecting an indirect water Figure 9-3A 102

99 SECTION 9 DESIGNING MULTIPLE-LOAD HYDRONIC SYSTEMS Figure 9-3B heater into the system is shown in figure 9-3B. The indirect water heater is now connected as a parallel circuit to the primary loop. It can operate independently of the primary loop. If the water heater is located close to the boiler and the piping circuit between the two is short, piping heat loss during the DHW cycle is minimal. Furthermore, this arrangement doesn t reduce the water temperature supplied to the primary loop should that loop be operating simultaneously with domestic water heating. Because of these advantages, the parallel piping arrangement is often preferred over piping the indirect water heaters as a secondary circuit. 9-5 Adding Space Heating Loads Most modern integrated multi-load hydronic systems are configured around a primary/secondary piping system. The details and options available for primary/secondary piping were discussed in section 8. The backbone of the system is the primary loop. It conveys hot water to one or more secondary circuits that, in turn, convey that water to the heat emitters. Each secondary circuit can be thought of as a subassembly that is plugged into the primary loop. When the system serves several loads that operate over a wide range of water temperatures, the loads requiring the high water temperatures should be piped in near the beginning of a series-type primary loop, while those requiring lower temperatures are connected near the end. This allows the loads to accommodate the decreasing water temperature around the primary loop. Designers should investigate the possibility of operating primary loops with temperature drops of 30 to 40 degrees F. under design load conditions, (instead 103

100 THE IPEX MANUAL OF MODERN HYDRONICS of the typical 20 degrees F.). The greater the temperature drop, the lower the primary loop flow rate can be to deliver all the output of the heat source. In many cases the size of the primary loop piping as well as the primary circulator can be reduced when the loop is designed around a higher temperature drop. A smaller circulator could significantly reduce the electrical energy used by the system over its lifetime. When designing a series primary loop, it s necessary to account for the temperature drop associated with each operating secondary circuit. Formula 8-1, repeated below, can be used for this purpose. Formula 8-1 T = Q 500 x f Where: T = Temperature drop in the primary loop across the tees of an operating secondary circuit (deg. F) Q = Rate of heat delivery to the secondary circuit (Btu/hr) f = Flow rate in the primary circuit (in gpm) 500 a constant for water (use 479 for 30%, and 450 for 50% glycol) The heat emitters in the various secondary circuits need to be sized for the water temperature available to them based on where they connect to the primary loop. The farther downstream a given secondary circuit connects to the primary loop, the lower the water temperature available to it (assuming the upstream secondary circuits are operating). If a conventional boiler is used as the heat source, the designer should also verify that the water temperature at the end of the primary loop (when all loads are operating) is high enough to prevent sustained flue gas condensation within the boiler or its vent piping. Refer to section 5 for a more detailed discussion of this topic. Figure 9-4 depicts a system using a single boiler to supply radiant floor heating as well as an indirect water heater. The floor heating system consists of three manifold stations piped in parallel. This arrangement supplies the same water temperature to each manifold station (as discussed in section 8). The supply water temperature to the floor circuits is controlled by a variable speed injection mixing system. Note that the DHW tank is connected as a parallel Figure

101 SECTION 9 DESIGNING MULTIPLE-LOAD HYDRONIC SYSTEMS Figure 9-5 circuit to the primary circuit. Also note the locations of the temperature sensors providing feedback to the injection controller. Figure 9-5 expands the system of figure 9-4 by adding a series of secondary circuits supplying finned-tube baseboard. Since the baseboards need to operate at a higher water temperature than the floor heating circuits, the secondary circuit supplying them is connected to the primary loop upstream of the injection mixing system. The distribution system is further expanded in figure 9-6 by adding a heat exchanger to supply heat to a garage floor heating subsystem that will be filled with a glycol solution allowing it to be completely turned off when desired. The temperature of the glycol solution is controlled by a variable speed injection pump that regulates the hot water flow through the hot side of the heat exchanger. The controller operating the injection pump monitors its own return temperature sensor located near the inlet of the boiler. When necessary, this controller reduces the hot water flow through the garage heat exchanger to prevent the cold garage floor slab from removing heat from the system faster than the heat plant can produce it. The heat exchanger, like the DHW tank, is connected as a parallel (rather than secondary) circuit. In the event the heat exchanger and the DHW tank are allowed by the controls to operate at the same time, this arrangement makes the highest water temperature in the system available to both loads. When the DHW tank or garage floor heat exchanger call for heat, (as evidenced by a contact closure of either a thermostat or aquastat) the boiler staging control receives a setpoint demand. In this mode, the target water temperature leaving the boiler manifold piping is typically in the range of 200 deg. F. When either of the space heating loads calls for heat, the boiler controller receives a heating demand. In this mode, the target water temperature is calculated by the boiler control based on the current outdoor temperature (e.g. outdoor reset control). 105

102 THE IPEX MANUAL OF MODERN HYDRONICS Figure 9-6 Figure 9-7 adds one more subassembly to the system. It s a secondary circuit consisting of a small circulator and homerun manifold station supplying several small heat emitters. Some of these heat emitters may be towel warmers in the building. Others may supplement the output of a heated floor in certain high load areas of the building. The home run approach as described in section 6 allows small diameter Kitec or PEX tubing to be routed through the building structure much like electrical cable. It also allows for individual circuit control and supplies the same water temperature to each circuit. Another modification shown in figure 9-7 is using an external stainless steel heat exchanger between the system water and a conventional hot water storage tank. A stainless steel or bronze circulator must be used between the storage tank and the heat exchanger. This arrangement can be used in situations where the heat transfer capacity of an indirect water heater (with its own internal heat exchanger) is not sufficient to transfer the full heat output of the heat plant to the domestic hot water load. When heat transfer between the heat plant and domestic hot water load is bottlenecked, the boiler will climb to its high limit temperature before the DHW load is satisfied and shut off during part of the cycle. As such, the heat plant is not delivering its full potential heat output rate to the load. Ensuring that this doesn t happen is important in systems that supply domestic hot water to homes with multiple bathrooms, especially those equipped with high water usage fixtures. 9-6 Summary of Design Concepts Here s a summary of the concepts to remember when designing multi-load hydronic systems: Use a single heat plant to supply all heating loads rather than using several dedicated heat sources. Examine load diversity when sizing the heating plant. Consider the likely total heat needed by 106

103 SECTION 9 DESIGNING MULTIPLE-LOAD HYDRONIC SYSTEMS Figure 9-7 the loads over a period of several hours. Use prioritized load shedding (when necessary) to handle unusually high load requirements. Use a multiple boiler system rather than a single large boiler when the system has a wide range of load requirements (such as a high intermittent demand for domestic water heating). When using multiple boilers, configure the piping and controls so heated water is not circulated through unfired boilers. When using multiple boilers, connect the boiler manifold to the distribution system with a pair of closely-spaced tees to prevent interference between the boiler circulators and those in the distribution system. Use a series primary loop when the water supply temperatures of the secondary loads vary over a wide range. Connect high temperature secondary circuits near the beginning of a series primary loop, and lower temperature loads near the end. Use a parallel primary secondary piping when the water supply temperatures of the secondary circuits are all similar. To minimize piping heat loss connect the indirect DHW tank as a parallel (rather than secondary) circuit. To reduce pipe size, pump size and operating cost, consider designing series-type primary loops for a temperature drop of 30 to 40 degree F. under full load. For maximum recovery rate, ensure that the full output of the heat plant can be delivered to the water heater without the boilers reaching their high limit temperature settings. Use an external heat exchanger if necessary to ensure full heat transfer to the domestic hot water storage tank. 107

104 SECTION 10 RADIANT PIPE AND TUBING IPEX is a leading supplier of thermoplastic piping systems, providing customers with one of the world s largest and most comprehensive product lines. Included in this offering are the two leading products for hydronic radiant heating Kitec XPA pipe and oxygen barrier PEX tubing. Kitec XPA and PEX tubing have each played an important role in the impressive growth of hydronic radiant system popularity in North America. Used in radiant floor heating for residential, industrial and institutional projects, radiator and baseboard hook-up, snowmelt systems and more, XPA and PEX transport liquid from heat source, to heat zone and back again. But why choose PEX tubing for a given radiant heating installation instead of XPA pipe? The answer is really based on personal preference. Some contractors prefer PEX tubing for staple-up applications between floor joists stating that PEX tube is more flexible and less prone to kinking than XPA pipe. Others find smaller 3/8 diameter PEX tube ideally suited for topping pour installations where floor to ceiling height is limited or were changing the floor elevation is restricted. Some say there is no discernable difference between the two and the matter is cost. Still, others feel that XPA pipe is by far the superior pipe for hydronics. The facts show that both PEX tubing and XPA pipe are viable products with decades of proven performance in all manner of hydronic applications. As the world s leading supplier of thermoplastic piping systems, IPEX offers industry the two leading options for hydronic pipe and tubing. In time, the debate over which is better XPA or PEX will sort itself out. Kitec XPA Pipe Great ideas are often born by merging the strengths of one product with those of another. Kitec XPA (X-linked Polyethylene Aluminum) pipe is the result of one of these great ideas. It combines the strength of metal with the 109

105 THE IPEX MANUAL OF MODERN HYDRONICS longevity of plastic and it brings some unique benefits to the hydronic radiant heating market. XPA s aluminum core is what sets it above all other heating pipes. In combination with x-linked polyethylene and specialized adhesive layers that bond the components together, this aluminum core is responsible for most of XPA pipe s unique features and benefits. Thanks to its aluminum core, XPA pipe is stronger than typical heating PEX tubing. XPA pipe exhibits greater long term pressure ratings (25% higher operating pressure than PEX tube), greater burst pressure resistance, greater hoop strength for resistance to crushing, greater beam strength for less sagging. Oxygen Barrier PEX Tubing PEX tubing is universally recognized as the most widely used radiant heating tube. Its light weight, flexibility and wide availability make it a natural choice for radiant heating applications. IPEX offers a full range of oxygen barrier PEX tubing sizes to round out its industry leading offering of WarmRite Floor hydronic radiant heating components. PEX manifold fittings are designed to quickly and easily connect PEX tubing to the full range of standard WarmRite Floor chrome manifolds. And pre-assembled WarmRite Floor control panels accept PEX tubing as well. In order to facilitate a technical comparison between XPA pipe and PEX tubing, the following information is arranged to show XPA details along side PEX. Kitec XPA Pipe Dimensions in inches PEX Tubing Dimensions in inches Nominal Size Average I.D. Average O.D. Weight lb / 100 ft Volume U.S. gal / ft Nominal Size Average I.D. Average O.D. Weight lb / 100 ft Volume U.S. gal / ft 3/ / / / / / / / Dimensions in mm Dimensions in mm Nominal Size Average I.D. Average O.D. Weight g / m Volume l / m Nominal Size Average I.D. Average O.D. Weight g / m Volume l / m

106 SECTION 10 RADIANT PIPE AND TUBING XPA pipe is easily shaped by hand, Keeps its shape XPA pipe loops can be easily shaped by hand to a radius of 5 times the pipe O.D. And thanks to the aluminum core XPA pipe maintains the shape that you bend it to this is of great benefit when installing radiant heating loops especially when compared to PEX tubing. Larger pipe sizes may require a bending tool to achieve the minimum radius shown. When uncoiled, PEX tubing tries to revert back to its smaller coil size. This makes installation somewhat more challenging and requires PEX tube to be secured at closer intervals in order to maintain its installed position. As well, PEX tubing is less malleable than XPA pipe and therefore has larger allowable bending radii than XPA. Nominal Pipe Size in mm 3/8 9 1/2 12 5/8 16 3/ Oxygen permeation XPA Pipe Min. Bend Radius in mm PEX Tubing Min. Bend Radius in mm Unlike barrier PEX tubing with its externally applied oxygen barrier XPA pipe houses an aluminum oxygen barrier permanently in between layers of plastic. This means that damage due to installation and construction is avoided making the oxygen barrier a permanent and reliable component of your heating system. XPA pipe limits oxygen permeation to 0.006g/m 3 /ºC/day, 25 times better than the acceptable standard. PEX tubing has its EVOH oxygen barrier located on the outside of the tubing. This layer limits oxygen permeation to minimum acceptable amount of 0.10 g/m 3 /ºC/day. XPA Pipe built in safety against ground source contaminants That same aluminum core that provides such an excellent and permanent oxygen barrier, acts as a first line of defense against ground source contamination such as termiticide. IPEX XPA pipe can be buried directly below grade and in the slab without fear of ground source contamination. PEX tubing should be treated as a thermoplastic piping material in relation to its permeability. Thermoplastic systems including PEX should not be used if ground source contamination is a threat. Low Expansion and Contraction The coefficient of linear expansion for XPA pipe is very similar to copper 1.3 x 10-5 in./in./ºf (0.23mm/10m/ºC). As an example, one hundred feet of XPA pipe with a 10ºF rise in temperature will expand only inches. PEX tubing on the other hand has a linear expansion / contraction 7 times greater than XPA pipe. One hundred feet of PEX tubing expands and contracts at a rate of 1.1 inches per 10ºF change in temperature. The following charts provide a quick reference for expansion / contraction of 100 feet (30.5m) of Kitec XPA pipe and PEX tubing. Approximate linear expansion / contraction of 100 feet of XPA pipe ºF ºC 20ºF (-7C) 40ºF (4C) 60ºF (15C) 70ºF (21C) 80ºF (27C) 100ºF (38C) 120ºF (49C) 140ºF (60C) 160ºF (71C) 180ºF (82C) 200ºF (93C) in mm m Approximate linear expansion / contraction of 100 feet of PEX Tubing ºF ºC 20ºF (-7C) 40ºF (4C) 660ºF (15C) 70ºF (21C) 80ºF (27C) 100ºF (38C) 120ºF (49C) 140ºF (60C) 160ºF (71C) 180ºF (82C) 200ºF (93C) in mm m

107 THE IPEX MANUAL OF MODERN HYDRONICS Less head loss than equivalent PEX tube The following table provides a head loss comparison between Kitec XPA Pipe and PEX Tubing. The larger I.D. of XPA is clearly evident in the following table. Detailed flow rate tables for various heating mediums and temperatures are included in the Appendices. Flow Rate GPM XPA Pipe Pressure Loss per 100 feet - psi PEX Tubing Pressure Loss per 100 feet - psi 3/8" 1/2" 5/8" 3/4" 1" 3/8" 1/2" 5/8" 3/4" 1" Flow Rate L / min XPA Pipe Pressure Loss per 100 meters - kpa PEX Tubing Pressure Loss per 100 meters - kpa 9mm 12mm 16mm 20mm 25mm 9mm 12mm 16mm 20mm 25mm

108 SECTION 10 RADIANT PIPE AND TUBING Larger inside diameters XPA pipe has larger inside diameters than the comparable nominal size PEX tubing. Nominal Size in 3/8 1/2 5/8 3/4 1 Rates of Thermal Conduction Due to its aluminum and plastic construction, XPA pipe has a greater rate of thermal conduction than does PEX tubing. The following chart defines values for both XPA and PEX. High pressure ratings IPEX XPA pipe provides 25% greater long term pressure rating than typical PEX tubing. XPA is rated for continual service of 200 psi at 73ºF and 125psi at 180ºF. PEX tubing is rated for continual service of 160 psi at 73ºF and 100psi at 180ºF. XPA also offers excellent resistance to quick burst conditions as shown in the following table. Quick Burst Pressures XPA Pipe Quick Burst 73ºF (23ºC) Quick Burst 180ºF (82ºC) mm Nominal Pipe Size in mm 3/8 9 1/2 12 5/8 16 3/ /8" (9mm) 1160 psi (8004kPa) 750 psi (5175kPa) XPA Pipe Actual I.D. in mm XPA Pipe BTU/h/ft/ºF W(m.ºC) ºF /2" (12mm) 1015 psi (7003kPa) 685 psi (4724kPa) ºC /8" (16mm) 1005 psi (6935kPa) 655 psi (4520kPa) PEX Tubing Actual I.D. in mm PEX Tubing BTU/h/ft/ºF W(m.ºC) ºF /4" (20mm) 825 psi (5693kPa) 550 psi (3795kPa) ºC " (25mm) 790 psi (5451kPa) 535 psi (3692kPa) Resistance to damage from freezing Good installation practice dictates protection against freezing for piping systems. However, in the event that freezing does occur, XPA pipe does provide a level of safety against pipe burst when installed in open free air conditions. Tests show that IPEX XPA pipe may take up to 5 freeze thaw cycles before failing. Compared to traditional metal pipes XPA provides you with more built in peace of mind. When encased in concrete however, the extreme forces of freezing water against cured concrete leave little chance for any pipe including XPA to survive. Care must always be taken to avoid freezing of hydronic piping installed in slabs. Flame Spread and Smoke Ratings XPA pipe has a Flame Spread Rating of 5 and a Smoke Development Rating of 5 as per third party testing to ULC-S This allows it to be used in high-rise construction as well as in return air plenums and vertical shafts. Check with the local authority having jurisdiction. PEX tubing also meets certain building code guidelines for use in combustible construction contact your IPEX representative for more details. Firestopping XPA Pipe XPA pipe has been tested and listed with various firestopping materials in accordance with CAN/ULC S115-M95, ASTM E81 and UL Approved and listed firestop materials are available from 3M (CP 25WB or Silicone 2000), PFP Partners (4800 DW) and Johns Manville (Firetemp Cl). In the event that XPA pipe must penetrate a fire rated wall, these firestop materials may be used to maintain the assembly rating. IPEX XPA pipe and firestop products must be installed in accordance with the individual product listing to ensure proper performance. Contact IPEX for detailed instructions. Electrical Properties Although XPA pipe contains an aluminum core, its joining systems are not designed to conduct stray current. In consideration of electrical grounding XPA pipe is considered to be a thermoplastic piping system and should never be used to ground. PEX tubing too should be treated as other thermoplastic piping systems are in that it must not be used to ground electrical systems. 113

109 THE IPEX MANUAL OF MODERN HYDRONICS XPA Pipe and Fitting Standards IPEX manufactures and carries third party certification on XPA pipe to the following standards: CAN / CSA B137.9 Standard for Crosslinked Polyethylene / Aluminum / Crosslinked Polyethylene Composite Pressure Pipe Systems ANSI/ASTM F1281 Standard Specification for Crosslinked Polyethylene / Aluminum / Crosslinked Polyethylene (PEX-AL-PEX) Pressure Pipe These standards include requirements for pipe sizes, dimensions, workmanship, quality control, burst and sustained pressure performance and more. ANSI / ASTM F1974 Standard Specifications for Metal Insert Fittings for Polyethylene / Aluminum / Polyethylene and Crosslinked Polyethylene / Aluminum / Crosslinked Polyethylene Composite Pressure Pipe This standard includes requirements for IPEX K1 compression style fittings and K2 crimp style fittings. The standard outlines acceptable fitting materials, dimensional requirements, short term burst and long term pressure ratings, etc. Mechanical and Building Code Compliance XPA pipe and fittings are recognized and included in the National Plumbing and Building Codes of Canada as well as in the National Hydronic Standard of Canada. In the United States XPA pipe and fittings are included in the Uniform Mechanical Code and the International Plumbing, Mechanical and Residential Codes. PPI TR-4 PPI Listing of Hydrostatic Design Bases and Maximum Recommended Hydrostatic Design Stresses for Thermoplastic Pipe Materials IPEX XPA pipe is listed with PPI for the following pressure and temperature ratings: 200psi at 73ºF 125psi at 180ºF PEX Tubing Standards IPEX offer CTS SDR-9 PEX tubing manufactured and third party certified to the following standards: CAN/CSA B137.5 Standard for Crosslinked Polyethylene Pressure Tubing Systems ASTM F876 Standard Specification for Crosslinked Polyethylene (PEX) Tubing ASTM F877 Standard Specification for Crosslinked Polyethylene (PEX) Plastic Hot and Cold Water Distribution Systems PPI TR-4 PPI Listing of Hydrostatic Design Bases and Maximum Recommended Hydrostatic Design Stresses for Thermoplastic Pipe Materials IPEX PEX tubing is listed with PPI for the following pressure and temperature ratings: 160psi at 73F 100psi at 180F ANSI / NSF 14 Plastics Piping System Components and Related Materials Product Certification Listing IPEX holds NSF certification on its PEX tubing for potable water applications and radiant floor heating in residential and commercial construction, including manufactured housing. Mechanical and Building Code Compliance PEX tubing is recognized and accepted in all model codes across North America including the National Plumbing Code of Canada, the National Hydronic Standard of Canada, the Uniform Mechanical Code, the International Plumbing, Mechanical and Residential Codes, and by BOCA and SBCCI. ANSI / NSF 14 Plastics Piping System Components and Related Materials Product Certification Listing IPEX holds NSF certification on its XPA pipe for potable water applications and radiant floor heating in residential and commercial construction, including manufactured housing. 114

110 SECTION 11 HYDRONIC SNOW AND ICE MELTING 11-1 Introduction: IPEX hydronic heating products can be used to provide snow and ice melting on all types of exterior areas including: Driveways Walkways Parking areas Steps Wheelchair access ramps Patios Decks Roofs On specialized commercial and industrial properties, hydronic snow melting has been used for the following applications: Car washes Hospital emergency entrances Toll booth areas Loading docks Helicopter landing pads Security gate areas Other areas that must be kept free of snow and ice 115

111 THE IPEX MANUAL OF MODERN HYDRONICS 11-2 The Benefits Hydronic snow and ice melting offers many benefits over traditional methods of snow removal. They include: The capability of providing fully automatic/unattended snow removal whenever required. The ability to remove snow without creating banks or piles that subsequently cause drifting, and often damage surrounding landscaping. The elimination of sanding. The elimination of salting and its potential damage to landscaping and the surrounding environment. Less pavement damage due to frost action, chemical deterioration due to salting, and physical damage from plowing. The latter is especially important when paving bricks/tiles are used. Cleaner interior floors because sand and salt are not tracked in Because all snow and ice is removed, the possibility of slips, falls or vehicular accidents is greatly reduced, especially on sloped pavements. This reduces liability, especially in public areas. Improved property appearance during winter. The ability to use almost any fuel or heat source to provide the energy required for melting System Classifications There are several possible approaches to designing a hydronic snow and ice melting system. They vary in both the rate of heat delivery to the surface being melted, and the type of controls used to initiate and terminate the melting operation. Over the last few decades the design of snow and ice melting systems has been somewhat loosely classified as follows: Class 1 systems: This class of system is generally accepted as sufficient for most residential walkway and driveway areas. The rate of heat delivery to the surface in generally in the range of 80 to 125 Btu/hr/square foot depending on location. Class 1 systems often allow a layer of snow to accumulate during a heavy snowfall, especially if the system is manually controlled and starts from cold. This snow layer is actually beneficial because it acts as an insulator between the heated pavement surface and the outside air reducing both evaporation and convective losses. Evaporation of the melt water requires much higher heat input. Class 2 systems: Generally accepted as sufficient for most retail and commercial paved areas that must be kept clear of accumulating snow during a heavy snow fall, although the pavement will often remain wet. The rate of heat delivery to the surface in typically in the range of 125 to 250 Btu/hr/square foot, depending on location. Class 3 systems: Used for high priority areas such as helicopter pads, toll plazas, sloped pavements in parking areas, pavements adjacent to hospital emergency rooms. Class 3 systems are designed with the ability to melt all snow as fast as it falls and quickly evaporate the melt water from the surface. They generally require heat delivery rates of 250 to as high as 450 Btu/hr/square foot. City Albuquerque, NM Amarillo, TX Boston, MA Buffalo Niagara Falls, NY Burlington, VT Caribou Limestone, ME Cheyenne, WY Chicago, IL Colorado Springs, CO Columbus, OH Detroit, MI Duluth, MN Falmouth, MA Great Falls, MT Hartford, CN Lincoln, NB Memphis, TN Minneapolis St. Paul, MN Mt. Home, ID New York, NY Ogden, UT Oklahoma City, OK Philadelphia, PA Pittsburgh, PA Portland, OR Rapid City, SD Reno, NV St. Louis, MO Salina, KS Sault Ste. Marie, MI Seattle Tacoma, WA Spokane, WA Washington, D.C. Design Output, Btu/hr/sqft Class I System Class II System Class III System (Permission to use data authorized by ASHRAE) 116

112 SECTION 11 HYDRONIC SNOW AND ICE MELTING The major distinction between these classes is in the rate of heat delivery to the area being melted. The following table gives suggested heat delivery rates for all three class of snow melting systems in several locations Tubing Installation Guidelines This section shows suggested construction details for installing Kitec tubing in various snow melting applications. These details have been carefully developed to ensure good performance of the system. In some cases, local design practices and code requirements may require them to be modified. Drainage considerations It is crucially important that all melted pavement areas be detailed for proper drainage of melt water. The heat delivery rates used with Class 1 and 2 systems assume that most of the melt water will be drained from the surface (as a liquid) rather than evaporated. The latter method of moisture removal requires considerably more heat input. Failure to provide proper drainage can allow melt water to accumulate at low points in the pavement, or where the melted pavement adjoins non-melted areas. When the system turns off, this standing water can quickly turn to dangerous ice. Pavements must be sloped to drains capable of routing the melt water to a drywell, storm sewer, or other discharge (check local codes) without it freezing in the process. Drainage piping should not run through the heated thermal mass because the cold water will rob heat from the system. Instead, drainage piping should be routed beneath the underside insulation where it is protected from freezing. Keep in mind that a shallow drainpipe running through unheated soil can quickly fill with ice and be very difficult to thaw. One method of ensuring the drainage system does not freeze is to install a dedicated drain heating circuit of Kitec tubing alongside the drainage trench, receptor and piping. Trench drain systems are often used at the lower elevations in melted pavements. If the pavement slopes toward a building, be sure the melt water can be collected before it can flow into the building. Likewise, be sure melt water running down a pavement toward a street will be collected by a drain before it contacts the unheated pavement. Figure 11-2 shows some examples of pavement drainage concepts. Be sure to discuss drainage provisions with those responsible for its installation as soon as possible in the planning stages of the system. overhead door sealant grate melted pavement trench drain at low point underside insulation to drywell melted pavement trench drain street pavement (unmelted) underside insulation to drywell Figure

113 THE IPEX MANUAL OF MODERN HYDRONICS Evaluating Sub-surface Conditions: When planning a snow melting system, the designer should always evaluate the soils under the area to be melted. Failure to address subsoil problems can lead to unanticipated conditions that will not only damage the pavement, but could also severely damage the tubing. If the local water table is within 3 feet of the surface, it has the potential to greatly increase downward heat loss from the melted pavement. Such situations require proper subsoil drainage to lower the water table. A properly detailed French drain constructed around the perimeter of the paved area is a typical solution. If bedrock is present under the area to be melted, it s imperative to slope or channel the rock surface so any water percolating down from the melted surface can be drained away. Otherwise, the bedrock may pond water under the melted pavement. It s also crucial to install a minimum of 1 inch of extruded polystyrene insulation to reduce heat conduction to the bedrock. Low percolation soils containing high amounts of clay or silt retain moisture in winter. When these (saturated) soils freeze, the expanding ice crystals create powerful forces that can easily crack and heave pavements upward. If such soils are present, the base layer of the pavement system should consist of 6 to 9 inches of #2 size crushed stone. The soil surface beneath the stone layer should be sloped so any water reaching the stone layer can be collected and drained away. The stone layer should also be tamped to form a flat surface for the insulation board installed above it. When pavements are to be placed over areas of disturbed or otherwise unstable soil, a geotextile fabric should be incorporated into this base layer. This very strong non-deteriorating fabric helps spread high loads over larger areas to prevent eventual depressions in the pavement. Such depressions could eventually damage embedded tubing. Remember no snow melting system can make up for poor pavement design. Be sure to involve knowledgeable professionals in the pavement planning process. Installation Procedure for Concrete Pavements Figure 11-3 shows the material assembly used for a typical snowmelting system in a concrete driveway or walkway. When the local soil has good drainage characteristics, the base layer generally consists of 6 to 9 inches of compacted gravel. Moisture that may eventually percolate down to this layer will pass through into the subsoil below. In some cases, a geotextile fabric will be incorporated into this base layer to further stabilize it. In cold climates or projects where the pavement will be held at an idling temperature near freezing, it is cost effective to install a layer of extruded polystyrene insulation over the compacted gravel base. This insulation greatly reduces downward heat loss from the pavement. It also shortens the response time of the system when melting is required, especially in cold climates where the system doesn t idle the slab. A thickness of 1 inch (R-5) is usually adequate. Be sure the rigid board insulation lies flat against the compacted gravel base at all locations so the pavement is fully supported when loaded. The compressive stress rating of the insulation should be selected to match loads that may be imposed on the pavement. A 25 psi rated insulation board is the minimum rating for pavements subject to light vehicular traffic. If heavier (truck) traffic is anticipated insulation with a compressive load rating of 40 to 60 psi should be considered. Insulation manufacturers can provide guidance on the proper compressive stress rating for a given pavement application. Welded wire fabric (WWF), or a grid of rebar is now installed over the insulation. Be sure to overlap all sheets of WWF by at least 6 and tie them together with wire twist ties. The Kitec tubing can now be secured to the steel reinforcing using wire twist ties spaced 48 to 60 inches apart. Tube spacing should never exceed 12 inches. Wider spacing can result in uneven melting patterns that may not completely clear the pavement of snow before the melting operation is shut off. Nine inch tube spacing is recommended in most cases. In areas with high snow fall rates, high average wind speeds or situations where a cold (non-idled) slab needs to be brought up to temperature quickly, 6 in. spacing should be used. Section 11-6 discusses tube spacing issues in more detail. Tubing circuits should be planned so as not to exceed the maximum lengths given in section The warmest portion of the circuit should generally be routed in the areas with the highest melting priority. For example, the tire track area of a typical driveway would usually have a higher melting priority than the edges of the driveway. Don t install tubing closer than 6 inches to the edge of the pavement. 118

114 SECTION 11 HYDRONIC SNOW AND ICE MELTING Figure 11-3 concrete paving pipe wire mesh insulation compacted base heavy duty extruded polystyrene SNOWMELT CONCRETE SLAB Figure 11-3A 119

115 THE IPEX MANUAL OF MODERN HYDRONICS Figure 11-4 shows a typical tubing layout for a residential driveway based on use of 5/8 Kitec pipe. It is highly recommend that the designer make an accurate tubing layout drawing for each project before installation begins. CAD generated tubing layouts allow the designer to check circuit lengths, determine the total amount of tubing needed and provide the installer with an easy to follow plan. Once installed, all tubing circuits should be pressure tested using compressed air at 75 psi for a minimum of 24 hours prior to placing the concrete. Be sure to cap all circuit ends until they are connected to the manifold to prevent construction dust and moisture from contaminating the system. The tubing and reinforcing steel should be supported or lifted during the pour so the top of the tubing is 1.5 to 2 inches below the finish surface of the slab. Tubing depth is more critical in a snow melting applications than in radiant floor heating. Leaving the tubing at the bottom of a typical 6 exterior slab significantly increases the response time of the system when melting is initiated. It also increases the required fluid temperature and downward heat loss. The tubing should be protected with sleeving wherever it crosses a full control joint location in the slab. The tubing depth should be sufficient to ensure that sawn control joints will not harm the tubing, no sleeving necessary. In locations where the tubing passes from the paved area through a foundation wall, the installation must be detailed to prevent damage to the tubing should the pavement shift up or down. Air entrained concrete with a minimal 28 day compressive stress rating of 4000 psi is often specified for exterior slabs. Figure

116 SESECTION 11 HYDRONIC SNOW AND ICE MELTING Installation Procedure for Asphalt Pavements Figure 11-5 shows the material assembly used for a typical snow melting system in asphalt paved driveways or walkways. The subgrade and insulation under an asphalt driveway or walkway is prepared the same as for a concrete pavement. A mat of welded wire fabric (WWF) is then laid out over the insulation. All sheets of the WWF Figure 11-5 asphalt paving compacted sand pipe wire mesh insulation compacted base heavy duty extruded polystyrene SNOWMELT ASPHALT PAVING Figure 11-5A 121

117 THE IPEX MANUAL OF MODERN HYDRONICS should be overlapped 6 inches at their edges and tied together with wire twist ties. The tubing is unrolled and secured to the WWF with wire twist ties spaced 48 to 60 inches apart. After pressure testing the circuits a 3 to 4 inch deep layer of sand or stone dust is placed over them. The sand/stone dust layer protects the tubing from the hot asphalt ( degrees F.). After the WWF and tubing have been placed, the sand/stone dust should be uniformly and thoroughly soaked with water to settle the particles around the tubing and provide a stable base for the asphalt. Kitec (PEX-AL-PEX) pipe is especially well suited to this application because its low coefficient of expansion minimizes dimensional changes of long tubing runs as the system cycles between warm and cold. When placed, asphalt paving can be as hot as 350 degrees F. It should never be placed directly on Kitec or PEX tubing. However, when the tubing is embedded in the layer of sand/stone dust as described, the hot asphalt can be placed without damaging to the tubing. Installation Procedure for Surfaces Covered with Paving Stones Pavements consisting of loosely laid (non-mortared) paving bricks or tiles are easily damaged by conventional methods of snow removal and therefor well suited to hydronic snow melting. Figure 11-6 shows the material assembly used for a typical snow melting system for an area finish with paving bricks or stone. Unlike concrete or asphalt, paving bricks allow water to seep down between individual units. This water cannot be allowed to accumulate under the pavers because subsequent freezing can cause the pavers to heave upward. In areas with low permeability soil, the base layer below the insulation should be detailed for efficient drainage. A 6 to 9 inch deep layer of #2 crushed stone placed over a slightly sloping grade allows vertical drainage of water. The crushed stone base layer must itself be drained to either a drywell or other suitable Figure

118 SECTION 11 HYDRONIC SNOW AND ICE MELTING paving bricks compacted sand pipe wire mesh insulation compacted base heavy-duty extruded polystyrene SNOWMELT PAVING STONES Figure 11-6A discharge area. The crushed stone layer should also be tamped flat before the rigid insulation is placed over it. Drainage detailing is still recommended since the rate of melt water (or rainwater) accumulation may at times exceed the rate at which water can weep downward between the pavers. Extruded polystyrene insulation is impermeable to water. To allow water drainage, nominal 1/2 gaps should be left between adjacent sheets of insulation. Alternatively, several sheets of rigid insulation can be stacked and drilled to form a grid of 1 inch diameter holes space 12 inches apart. In either case, the holes or slots must be covered with strips of water permeable filter fabric. This allows water to drain through without carrying the fine particles of sand or stone dust with it. Avoid creating drainage situations where flowing water could form channels through the sand/stone dust layer beneath the pavers. Such channels could lead to voids that may eventually cause some pavers to sink. A mat of welded wire fabric (WWF) is laid out over the insulation. All sheets of the WWF should be overlapped 6 inches at their edges and tied together with wire twist ties. The tubing is then unrolled and secured to the WWF with wire twist ties spaced 48 to 60 inches apart. After the tubing circuits have been pressure tested, the tubing and WWF should be covered with 3 to 4 inches of sand or stone dust. After the WWF and tubing have been layered the sand layer should be uniformly and thoroughly soaked with water to settle the sand or stone dust around the tubing and provide a stable base for the pavers Controlling Snow Melting Systems There are several ways to control snow-melting systems. They differ in their ability to detect when melting is required, as well as how they control the pavement temperature before, during and after melting operation. They also differ considerably in cost. The approach selected must be based on the expectation of the owner, the degree of unattended operation expected, the size of the area being melted and the class of system being designed. Regardless of the control method used, some fundamental issues must be understood before a snowmelt system can be properly designed: Antifreeze Issues Some snow melting systems use a dedicated boiler as their heat source. The boiler and distribution piping is usually filled with an antifreeze solution (typically a 30 to 50% mixture of propylene glycol and water). In other systems snow melting as one of several loads served by the same boiler(s). The boiler(s) and piping that s are not part of the snow melting system are filled with water. In this case, a heat exchanger must be installed to isolate the antifreeze solution in the snow melting distribution system from the remainder of the system. A stainless steel plate type heat exchanger is often used for such applications. The freezing point of the mixture is a function of the % and type of glycol used. The following table helps select the correct mixture based on the outdoor temperature. Glycol % 10% 20% 25% 30% 35% 40% 45% 50% 55% Propylene 27 F 19 F 15 F 8 F 0 F -3 F -15 F -28 F -40 F Ethylene 27 F 18 F 10 F 5 F -2 F -10 F -20 F -33 F -50 F When the system starts with a cold boiler it may be possible for very cold antifreeze returning from the exterior circuits to flow through the heat exchanger 123

119 THE IPEX MANUAL OF MODERN HYDRONICS before much heat is delivered from the boiler to the heat exchanger. This, combined with the fact that plate heat exchangers are very efficient and have little thermal mass, presents the possibility of freezing the water in the hot side of the exchanger before heat can be delivered from the boiler. To avoid this possibility, use a temperature control to sense that hot water is flowing through the heat exchanger before allowing the circulator in the snow melting distribution system from operating. Some snow melting system controllers may have this capability built into them. Boiler Issues Section 3 described the necessity of maintaining the inlet temperature to a conventional boiler high enough to prevent sustained flue gas condensation. This is of utmost important when a conventional boiler is used as the heat source for a snow-melting system. The system must use a control that measures the inlet temperature to the boiler and reduces the rate of heat transfer through the mixing device supplying to the snowmelt system, when necessary, to prevent sustained flue gas condensation. The mixing device Figure

120 SECTION 11 HYDRONIC SNOW AND ICE MELTING can be a 2-way, 3-way, or 4-way mixing valve or variable speed injection pump as discussed in section 3 and shown in figure Condensing boilers are well suited to the low operating temperatures of hydronic snow melting systems. In most cases there is no need to install a mixing device between a condensing boiler and the snow melt distribution system. If the condensing boiler is operated with the same antifreeze solution as the snow melt circuits, there is no need to install a heat exchanger. This minimizes the operating temperature of a condensing boiler and increases its efficiency. Idling Pavement Surfaces When the melting system starts from a cold temperature, it may take considerable time for the surface to reach melting temperature. To decrease this lag time, some snow melt controls can maintain the pavement at an idling temperature just above or below freezing. If the pavement temperature is idled just above freezing, it will generally be free of frost and black ice, and be an important advantage in terms of safety. Idling the pavement just below freezing reduces standby heat loss, but still allows for rapid warm-up to melting temperature. Most controls let the installer adjust the pavement idling temperature. Control systems with idling capability typically initiate the idling mode when the outside air temperature drops within a few degrees of freezing (35 to 40 degrees F.). Such air temperatures represent the possibility of frozen precipitation. Idling the system above these air temperatures is largely a waste of fuel. To idle the pavement, the controller must sense pavement temperature. Typically, a small thermistor sensor is located within a well in the slab. This well is usually made of capped copper tubing that s cast Figure

121 THE IPEX MANUAL OF MODERN HYDRONICS into the pavement. The position of the slab temperature sensor is crucial to the proper performance of the control system. The slab sensor is typically located 1 below the top of the pavement, and halfway between adjacent tube circuits. The open end of the well should lead to an accessible location so the sensor can be replaced if it ever fails. Be sure to follow the control manufacturers recommendations regarding installation of the pavement temperature sensor. Manual Melting Control Systems can be designed with manually operated start and stop controls. Typically the system begins supplying heat to cold pavement when a switch is moved to the on position. Heat flows to the pavement as long as the switch remains on. This approach is fine, provided someone pays close attention to the status of the snow on the pavement, and turns the system off as soon as melting is completed. If the attending person forgets the system is operating, it could run indefinitely (or until it runs out of fuel). The cost of unnecessary operation can be high, especially on larger systems. This possibility is the single biggest argument against a manual start / manual stop control system. The next logical refinement would be a control system with manual start and automatic shut off. The system is shut off after a set time has elapsed. The time is selected by the person turning on the system based on the amount of snow and previous experience with the system. Overriding conditions such as very cold air temperatures, or sustained air temperatures above freezing, may also be used to terminate operation. The goal is to turn the system off as soon as melting is complete and the pavement is in the process of drying. The latter is important to prevent the formation of dangerous black ice. Some manual start/automatic off snowmelt controllers also allow the pavement to be maintained at a set idling temperature. Automatic Melting Control More sophisticated snow melting controls are available that automatically detect frozen precipitation on the slab surface and initiate melting operation. They also terminate heat input when melting is complete. Most can also be configured to idle the pavement at a specific temperature when desired. Fully automatic snow melting controls require a snow detection sensor. Some sensors are mounted directly into the top surface of the pavement and can detect when frozen precipitation is present, as well as measure pavement temperature. Other types of sensors are mounted above the pavement. They provide an electrical contact closure whenever precipitation is occurring AND the outside air temperature is below a given temperature. Both types of sensors have a small heated cell at the top of their housing. Precipitation is detected by the electrical conductivity of the water on this cell. This, in combination with an air temperature just above freezing, provides the start-up criteria for the system. Control systems that monitor pavement temperature tend to reduce fuel usage by allowing the system to maintain the pavement surface just a few degrees above freezing. The cooler the pavement surface, the lower the heat losses. Many snow melting controls can also prevent or terminate melting if the outside air temperature rises above a preset value. In non-critical applications (class 1 systems), melting can also be prevented or terminated during very cold weather when heat loss would be excessive Circuit Design Information Selecting the proper tube size, spacing and flow rate is an important part of system design. The section gives technical guidelines and formulas that can be used to evaluate the trade-offs and help optimize the system. Flow requirements The flow rate required for a snow melting circuit to deliver a given amount of heat to the pavement can be determined using formula Formula 11-1 where: f = f = required flow rate (gpm) T = temperature drop on the loop(degf) q = rate of heat output required (Btu/hr) k = a constant based on the concentration of antifreeze used (see chart below) 100% water 30% Propylene glycol q k x T 40% Propylene glycol 50% Propylene glycol k=500 K=477 K=465 K=449 For example: the flow rate required to deliver 22,000 Btu/hr using a 40% solution of propylene glycol in a circuit operating with a 20 degree F. temperature drop is: 126

122 SECTION 11 HYDRONIC SNOW AND ICE MELTING The rate of heat delivery required for many snow melting applications is considerably higher than that required for a typical floor heating system. To deliver more heat without excessive temperature drop, the flow rate in the embedded circuits must be increased. The use of glycol-based antifreeze solution (instead of 100% water) reduces the heat carrying ability of the heat transfer fluid, and further increases the flow requirement. For example: the flow rate in a 250 foot long floor heating circuit, with tubing spaced 12" apart, delivering 25 Btu/hr/sqft with a 20 degree F. drop in water temperature is: q f = 500 x T This flow is easily handled by a 3/8" or 1/2" tube. However, the required flow rate in a 250 foot long circuit using tubing spaced 12" apart, delivering 150 Btu/hr/sqft with a temperature drop of 20 degrees F., and using a 50% solution of propylene glycol is: f = f = x 20 q 450 x T = 250 x x 20 = 2.36 gpm = 250 x x 20 = 0.63 gpm = 4.2 gpm This flow rate is well beyond proper range of application for a 1/2" tube. The common solution to the high flow requirement of snow melting systems is to use larger diameter tubing. 5/8 Kitec pipe is commonly used in snow melting applications, while 3/4" diameter Kitec pipe is sometimes used in larger systems. In some locations, such as steps, the bending limitations of 5/8 and 3/4" Kitec pipe does not allow it to be used. In these situations, use multiple shorter circuits of 1/2" pipe. The following table gives suggested maximum circuit lengths for various sizes of Kitec pipe used in snow melting applications. These lengths assume a 50% propylene glycol solution is carried by the tubing, and that the allowable head loss is equivalent to that of a 300 foot long circuit of 1/2" Kitec pipe used in a typical floor heating application. maximum circuit length Note the allowable length of 1/2" tubing circuit is approximately 50% that of 3/4" tubing. Likewise, the allowable length of a 5/8" Kitec tubing circuit is approximately 65% that of 3/4" tubing. Circuit Head Loss The head loss of the snow melting circuits along with the system flow requirements will determine the size of the system s circulator(s). It s important to select tube sizes and limit circuit lengths to prevent excessive head loss in snow melting circuits. Formula 11-2 can be used to estimate the head loss and resulting pressure drop in Kitec tubing carrying a 50% solution of propylene glycol and water at a mean temperature of 100 degrees F. This temperature was selected as representative of average conditions is a class 1 (residential) system. The head loss is about 12% higher than predicted by the formula when the mean fluid is at 80 degrees F., and about 15% lower when the fluid temperature is 140 degrees F. Formula 11-2 where: 1/2" Kitec 180 ft. 5/8" Kitec 250 ft. 3/4" Kitec 400 ft. H loss = c x L x f " Kitec 560 ft. H loss = head loss (feet of head) c = a constant based on tube size (see table below) L = circuit length (feet) f = flow rate (US gpm) 1.75 = an exponent of the flow rate c value 1/2" Kitec 5/8" Kitec 3/4" Kitec 1" Kitec

123 THE IPEX MANUAL OF MODERN HYDRONICS Circuit Temperature Drop Most snow melting systems are designed with circuit temperature drops of 20 to 30 degrees F. under steady state operation. However, during start-up of a cold pavement, the temperature drop can easily be 3 to 5 times greater than this. This is why it s so important to protect a conventional boiler as discussed in the previous section. As the slab gradually warms up, the temperature drop decreases towards its nominal design value. Temperature drops in excess of 30 degrees F. can result in uneven melting patterns on pavement surfaces. One novel approach to correcting this situation is to periodically reverse the flow through the tubing circuits. A motorized 4-way mixing valve that cycles from one end of its travel range to another based on signals from a time delay relay is one way to do this. This concept allows more even heat distribution to the pavement, and arguably could allow the system to use higher steady state temperature drops. The larger temperature drops would reduce flow rates and required pumping power. The concept is shown in figure Estimating Heat Output The exact heat output of a heated exterior pavement depends on many simultaneous conditions such as air temperature, wind speed, relative humidity, snow coverage, rate of snow fall, pavement drainage characteristic, tube diameter, tube spacing, R-value of underside insulation, soil temperature and thermal properties of the paving. Many of these conditions change from one melting cycle to the next. Some of these parameters may not be known or readily obtainable by the designer. Thus, it is very difficult to develop a highly precise engineering model of a given Figure

124 SECTION 11 HYDRONIC SNOW AND ICE MELTING snow melting installation. Formula 11-3 is an empirically derived relationship that can be used to approximate the heat output of a snowmelt slab using tubing spaced 12 inches apart, and covered with snow in the process of melting. where: Q = heat output (Btu/hr/sq. ft.) MFT = mean fluid temperature in the circuit (degree F.) For example: assume a tube circuit installed at 12 inch spacing is supplied with 120 degree F. fluid and operates with a 20 degree F. temperature drop. The mean fluid temperature in the circuit is 110 degrees F. When the slab is covered with a film of water (from the melting snow), its rate of heat output is approximately: Formula 11-3 Q = 2 x (MFT - 33) Q = 2 x (110-33) = 154 Btu/hr/sq.ft. Tube Spacing Factors Figure can be used to estimate the relative gain in heat output when tubes are spaced closer than 12 inches apart. Simply multiply the slab s heat output assuming 12 inch tube spacing by the multiplier to estimate its heat output, using the same mean fluid temperature, at closer tube spacing. For example: if the pavement s heat output using tubing spaced 12 inches apart averages 154 Btu/hr/sq. ft., its estimated average heat output using 6 inch tube spacing, and the same mean fluid temperature is 154 x 1.34 = 206 Btu/hr/sq. ft. The following tube spacings are suggested as a general guideline based on the system s class. Obviously closer tube spacing allow higher rates of heat delivery, albeit at a higher cost. Tube spaced more than 12 apart can lead to excessively uneven melting patterns, and is not recommended. Class 1 systems: 9-12 inches Class 2 systems: 6-9 inches Class 3 systems: 6 inches IPEX Radiant TM design software can be used for further studying the performance trade-offs of various tube spacing and fluid supply temperatures. Figure

125 SECTION 12 IPEX RADIANT TM DESIGN SOFTWARE The heating system is an integral part of building design and requires a specific and detailed design process. Heating engineers must analyze building location, function, occupancy and control requirements in order to select and design the proper system and specify the appropriate components. IPEX offers the state-of-the-art IPEX Radiant TM Design software program to assist designers in calculating a number of the key design features of hydronic radiant heating systems. IPEX Radiant TM greatly assists designers by performing the following tasks: Building heat loss calculations Floor output sizing to compensate for heat loss Floor piping details and specifications Control Panel and Manifold Selection Supply and Return Piping Design Temperature Control Selection Suited to the Project Project Material List and Report Generation Project calculations are summarized in reports of varying details depending on your needs. Summary reports provide overall project design information while detailed reports present every aspect of your calculations. IPEX Radiant comes complete with a WarmRite Floor component data base and prices. It lets you add non IPEX components to your own data base of heating items regularly specified and it creates customer and project data bases to assist in managing on-going designs and for future follow-up. All of these features are compiled inside an interactive, user friendly software that gives designers the flexibility to create and specify the best possible hydronic radiant heating system. 131

126 THE IPEX MANUAL OF MODERN HYDRONICS IPEX Radiant TM Design Software System Requirements The program is offered on CD-ROM and must be loaded onto the hard drive of your computer. Minimum operating system requirements are as follows: Processor Pentium 133 or greater Hard Disk Space 50 MB RAM 32 MB minimum; 64 MB or greater recommended Video Adapter VGA Operating System Windows 95, Windows 98, Window NT4 (SP5) or Windows 2000 Insert the disk and loading starts automatically. If the Auto Run does not start choose Start / Run, type D:SETUP then choose OK. The setup wizard will install the software onto your hard drive. Follow the screen prompts during this process. When the installation is finished an icon will appear on your desktop, giving you access to IPEX Radiant at the click of your mouse. The IPEX Radiant TM Design Software is supported with a Help Wizard and full program tutorial. To obtain your personal copy of the IPEX Radiant TM Design Software, please copy, complete and fax through the required form on the following page. 132

127 SECTION 12 IPEX RADIANT DESIGN SOFTWARE REQUEST FORM IPEX RADIANT TM DESIGN SOFTWARE AND/OR MANUAL OF MODERN HYDRONICS Fax this completed form to to request your copy of the IPEX Radiant TM Design Software and/or IPEX Manual of Modern Hydronics. Manual of Modern Hydronics IPEX Radiant TM Design Software Name Title Company Dept. Address or copy Business Card City Province/State Postal Code/Zip Phone Fax Indicate if registrant is an Authorized WarmRite installer. Company classification Architect/Designer Contractor Inspector Distributor Engineer Government Home Builder OEM - Products manufactured: Other SIC or industry sector: 133

128 APPENDIX A HYDRONIC SCHEMATIC SYMBOLS back flow preventer floating air vent swing check valve air separator flow check valve 3 way mixing valve spring loaded check valve D diverting 3 way valve isolating valve T thermostatic 3 way valve gate valve M motorized 3 way valve globe valve 4 way mixing valve T thermostatic valve M motorized 4 way valve M motorized valve P pressure gauge A1

129 APPENDIX A HYDRONIC SCHEMATIC SYMBOLS pressure reducing valve T temperature gauge pressure balancing bypass valve T/P thermo-pressure gauge pressure relief valve circulator drain valve circulator with isolating flanges manual air vent expansion tank A2

130 APPENDIX A HYDRONIC SCHEMATIC SYMBOLS heat exchanger radiator base board fan coil P supply B boiler radiant floor piping return hot out WH water heater m manifold set cold in hot out indirect WH cold in indirect water heater A3

131 APPENDIX A HYDRONIC SCHEMATIC SYMBOLS supply manifold return manifold balancing, flow indicator manifold with balancing valves plain manifold manifold with actuator valves manifold with isolating valves A4

132 APPENDIX A ELECTRICAL SYMBOLS thermostat sensor valve actuator (power head) electrical heating element valve actuator (power head) with end switch transformer MIXING CONTROL controller single switch combination snow/ice sensor T temperature sensitive switch A5

133 APPENDIX A CONTROL PANEL SCHEMATIC SYMBOLS injection mixing control panel manifold station with circulator recirculating zone control panel manifold station recirculating zone control panel with expansion tank snowmelt / industrial control panel control panel with heat exchanger injection mixing secondary control panel floor warming control panel isolation module multi zone manifold station A6

134 APPENDIX B HEAD LOSS CALCULATIONS FOR XPA PIPE AND PEX TUBING The following Appendix provides head loss information for XPA pipe and PEX tubing over a range of flow rates and liquid temperatures. Tables have been developed for 100% water as well as for a range of glycol/water mixtures typically used in hydronic systems. For operating conditions not covered by the following tables contact IPEX for further information. IPEX follows ASHRAE principles for head loss calculation. In particular, the Friction Factor formula used is a function of the Reynold s Number - see below. friction factor f = 64 / Re# if Re# < 3,000 f = / Re#^0.25 if 3,000 < Re# < 10,000 Reynolds # Re# = v d D / u v = velocity d = inside diameter D = density u = viscosity 3/8" XPA Pipe / 10% Glycol / 80 Deg F (27 Deg C) f = / Re#^0.237 if Re# > 10,000 velocity (ft/sec) v = y / A y = flowrate A = cross section area head loss (m) H = f (L/D) (v^2 / 2g) v = velocity L = length D = diameter f = friction factor g = 9.81 Diameter Flowrate Density Viscosity Reynolds Friction Loss / 100ft Velocity Flowrate Loss /100m Head Loss Velocity inch GPM kg/m Pa s Number Factor PSI ft/s L / min kpa m m / s B1

135 APPENDIX B HEAD LOSS - 3/8" XPA PIPE 100% Water 3/8" XPA Pipe / 100% Water / 80 Deg F (27 Deg C) 3/8" XPA Pipe / 100% Water / 140 Deg F (60 Deg C) /8" XPA Pipe / 100% Water / 100 Deg F (38 Deg C) /8" XPA Pipe / 100% Water / 120 Deg F (49 Deg C) /8" XPA Pipe / 100% Water / 160 Deg F (71 Deg C) /8" XPA Pipe / 100% Water / 180 Deg F (82 Deg C) B2

136 APPENDIX B HEAD LOSS - 1/2" XPA PIPE 100% Water 1/2" XPA Pipe / 100% Water / 80 Deg F (27 Deg C) 1/2" XPA Pipe / 100% Water / 140 Deg F (60 Deg C) /2" XPA Pipe / 100% Water / 100 Deg F (38 Deg C) /2" XPA Pipe / 100% Water / 120 Deg F (49 Deg C) /2" XPA Pipe / 100% Water / 160 Deg F (71 Deg C) /2" XPA Pipe / 100% Water / 180 Deg F (82 Deg C) B3

137 APPENDIX B HEAD LOSS - 5/8" XPA PIPE 100% Water 5/8" XPA Pipe / 100% Water / 80 Deg F (27 Deg C) 5/8" XPA Pipe / 100% Water / 140 Deg F (60 Deg C) /8" XPA Pipe / 100% Water / 100 Deg F (38 Deg C) /8" XPA Pipe / 100% Water / 120 Deg F (49 Deg C) /8" XPA Pipe / 100% Water / 160 Deg F (71 Deg C) /8" XPA Pipe / 100% Water / 180 Deg F (82 Deg C) B4

138 APPENDIX B HEAD LOSS - 3/4" XPA PIPE 100% Water 3/4" XPA Pipe / 100% Water / 80 Deg F (27 Deg C) 3/4" XPA Pipe / 100% Water / 140 Deg F (60 Deg C) /4" XPA Pipe / 100% Water / 100 Deg F (38 Deg C) /4" XPA Pipe / 100% Water / 120 Deg F (49 Deg C) /4" XPA Pipe / 100% Water / 160 Deg F (71 Deg C) /4" XPA Pipe / 100% Water / 180 Deg F (82 Deg C) B5

139 APPENDIX B HEAD LOSS - 3/4" XPA SUPPLY PIPE 100% Water 3/4" XPA Pipe / 100% Water / 80 Deg F (27 Deg C) 3/4" XPA Pipe / 100% Water / 140 Deg F (60 Deg C) /4" XPA Pipe / 100% Water / 100 Deg F (38 Deg C) /4" XPA Pipe / 100% Water / 120 Deg F (49 Deg C) /4" XPA Pipe / 100% Water / 160 Deg F (71 Deg C) /4" XPA Pipe / 100% Water / 180 Deg F (82 Deg C) B6

140 1" XPA Pipe / 100% Water / 80 Deg F (27 Deg C) APPENDIX B HEAD LOSS - 1" XPA PIPE 100% Water 1" XPA Pipe / 100% Water / 140 Deg F (60 Deg C) " XPA Pipe / 100% Water / 100 Deg F (38 Deg C) " XPA Pipe / 100% Water / 120 Deg F (49 Deg C) " XPA Pipe / 100% Water / 160 Deg F (71 Deg C) " XPA Pipe / 100% Water / 180 Deg F (82 Deg C) B7

141 APPENDIX B HEAD LOSS - 1" XPA SUPPLY PIPE 100% Water 1" XPA Pipe / 100% Water / 80 Deg F (27 Deg C) 1" XPA Pipe / 100% Water / 140 Deg F (60 Deg C) " XPA Pipe / 100% Water / 100 Deg F (38 Deg C) " XPA Pipe / 100% Water / 120 Deg F (49 Deg C) " XPA Pipe / 100% Water / 160 Deg F (71 Deg C) " XPA Pipe / 100% Water / 180 Deg F (82 Deg C) B8

142 APPENDIX B HEAD LOSS - 3/8" PEX TUBING 100% Water 3/8" PEX Tubing / 100% Water / 80 Deg F (27 Deg C) 3/8" PEX Tubing / 100% Water / 140 Deg F (60 Deg C) /8" PEX Tubing / 100% Water / 100 Deg F (38 Deg C) /8" PEX Tubing / 100% Water / 120 Deg F (49 Deg C) /8" PEX Tubing / 100% Water / 160 Deg F (71 Deg C) /8" PEX Tubing / 100% Water / 180 Deg F (82 Deg C) B9

143 APPENDIX B HEAD LOSS - 1/2" PEX TUBING 100% Water 1/2" PEX Tubing / 100% Water / 80 Deg F (27 Deg C) 1/2" PEX Tubing / 100% Water / 140 Deg F (60 Deg C) /2" PEX Tubing / 100% Water / 100 Deg F (38 Deg C) /2" PEX Tubing / 100% Water / 120 Deg F (49 Deg C) /2" PEX Tubing / 100% Water / 160 Deg F (71 Deg C) /2" PEX Tubing / 100% Water / 180 Deg F (82 Deg C) B10

144 APPENDIX B HEAD LOSS - 5/8" PEX TUBING 100% Water 5/8" PEX Tubing / 100% Water / 80 Deg F (27 Deg C) 5/8" PEX Tubing / 100% Water / 140 Deg F (60 Deg C) /8" PEX Tubing / 100% Water / 100 Deg F (38 Deg C) /8" PEX Tubing / 100% Water / 120 Deg F (49 Deg C) /8" PEX Tubing / 100% Water / 160 Deg F (71 Deg C) /8" PEX Tubing / 100% Water / 180 Deg F (82 Deg C) B11

145 APPENDIX B HEAD LOSS - 3/4" PEX TUBING 100% Water 3/4" PEX Tubing / 100% Water / 80 Deg F (27 Deg C) 3/4" PEX Tubing / 100% Water / 140 Deg F (60 Deg C) /4" PEX Tubing / 100% Water / 100 Deg F (38 Deg C) /4" PEX Tubing / 100% Water / 120 Deg F (49 Deg C) /4" PEX Tubing / 100% Water / 160 Deg F (71 Deg C) /4" PEX Tubing / 100% Water / 180 Deg F (82 Deg C) B12

146 APPENDIX B HEAD LOSS - 1" PEX TUBING 100% Water 1" PEX Tubing / 100% Water / 80 Deg F (27 Deg C) 1" PEX Tubing / 100% Water / 140 Deg F (60 Deg C) " PEX Tubing / 100% Water / 100 Deg F (38 Deg C) " PEX Tubing / 100% Water / 120 Deg F (49 Deg C) " PEX Tubing / 100% Water / 160 Deg F (71 Deg C) " PEX Tubing / 100% Water / 180 Deg F (82 Deg C) B13

147 APPENDIX B HEAD LOSS - 1" PEX SUPPLY TUBING 100% Water 1" PEX Tubing / 100% Water / 80 Deg F (27 Deg C) 1" PEX Tubing / 100% Water / 140 Deg F (60 Deg C) " PEX Tubing / 100% Water / 100 Deg F (38 Deg C) " PEX Tubing / 100% Water / 120 Deg F (49 Deg C) " PEX Tubing / 100% Water / 160 Deg F (71 Deg C) " PEX Tubing / 100% Water / 180 Deg F (82 Deg C) B14

148 APPENDIX B HEAD LOSS - 1/2" XPA PIPE 30% Glycol 1/2" XPA Pipe / 30% Glycol / 80 Deg F (27 Deg C) 1/2" XPA Pipe / 30% Glycol / 140 Deg F (60 Deg C) /2" XPA Pipe / 30% Glycol / 100 Deg F (38 Deg C) /2" XPA Pipe / 30% Glycol / 120 Deg F (49 Deg C) /2" XPA Pipe / 30% Glycol / 160 Deg F (71 Deg C) /2" XPA Pipe / 30% Glycol / 180 Deg F (82 Deg C) B15

149 APPENDIX B HEAD LOSS - 1/2" XPA PIPE 50% Glycol 1/2" XPA Pipe / 50% Glycol / 80 Deg F (27 Deg C) 1/2" XPA Pipe / 50% Glycol / 140 Deg F (60 Deg C) /2" XPA Pipe / 50% Glycol / 100 Deg F (38 Deg C) /2" XPA Pipe / 50% Glycol / 120 Deg F (49 Deg C) /2" XPA Pipe / 50% Glycol / 160 Deg F (71 Deg C) /2" XPA Pipe / 50% Glycol / 180 Deg F (82 Deg C) B16

150 APPENDIX B HEAD LOSS - 5/8" XPA PIPE 30% Glycol 5/8" XPA Pipe / 30% Glycol / 80 Deg F (27 Deg C) 5/8" XPA Pipe / 30% Glycol / 140 Deg F (60 Deg C) /8" XPA Pipe / 30% Glycol / 100 Deg F (38 Deg C) /8" XPA Pipe / 30% Glycol / 120 Deg F (49 Deg C) /8" XPA Pipe / 30% Glycol / 160 Deg F (71 Deg C) /8" XPA Pipe / 30% Glycol / 180 Deg F (82 Deg C) B17

151 APPENDIX B HEAD LOSS - 5/8" XPA PIPE 50% Glycol 5/8" XPA Pipe / 50% Glycol / 80 Deg F (27 Deg C) 5/8" XPA Pipe / 50% Glycol / 140 Deg F (60 Deg C) /8" XPA Pipe / 50% Glycol / 100 Deg F (38 Deg C) /8" XPA Pipe / 50% Glycol / 120 Deg F (49 Deg C) /8" XPA Pipe / 50% Glycol / 160 Deg F (71 Deg C) /8" XPA Pipe / 50% Glycol / 180 Deg F (82 Deg C) B18

152 APPENDIX B HEAD LOSS - 3/4" XPA PIPE 30% Glycol 3/4" XPA Pipe / 30% Glycol / 80 Deg F (27 Deg C) 3/4" XPA Pipe / 30% Glycol / 140 Deg F (60 Deg C) /4" XPA Pipe / 30% Glycol / 100 Deg F (38 Deg C) /4" XPA Pipe / 30% Glycol / 120 Deg F (49 Deg C) /4" XPA Pipe / 30% Glycol / 160 Deg F (71 Deg C) /4" XPA Pipe / 30% Glycol / 180 Deg F (82 Deg C) B19

153 APPENDIX B HEAD LOSS - 3/4" XPA PIPE 50% Glycol 3/4" XPA Pipe / 50% Glycol / 80 Deg F (27 Deg C) 3/4" XPA Pipe / 50% Glycol / 140 Deg F (60 Deg C) /4" XPA Pipe / 50% Glycol / 100 Deg F (38 Deg C) /4" XPA Pipe / 50% Glycol / 120 Deg F (49 Deg C) /4" XPA Pipe / 50% Glycol / 160 Deg F (71 Deg C) /4" XPA Pipe / 50% Glycol / 180 Deg F (82 Deg C) B20

154 APPENDIX B HEAD LOSS - 1/2" PEX TUBING 30% Glycol 1/2" PEX Tubing / 30% Glycol / 80 Deg F (27 Deg C) 1/2" PEX Tubing / 30% Glycol / 140 Deg F (60 Deg C) /2" PEX Tubing / 30% Glycol / 100 Deg F (38 Deg C) /2" PEX Tubing / 30% Glycol / 120 Deg F (49 Deg C) /2" PEX Tubing / 30% Glycol / 160 Deg F (71 Deg C) /2" PEX Tubing / 30% Glycol / 180 Deg F (82 Deg C) B21

155 APPENDIX B HEAD LOSS - 1/2" PEX TUBING 50% Glycol 1/2" PEX Tubing / 50% Glycol / 80 Deg F (27 Deg C) 1/2" PEX Tubing / 50% Glycol / 140 Deg F (60 Deg C) /2" PEX Tubing / 50% Glycol / 100 Deg F (38 Deg C) /2" PEX Tubing / 50% Glycol / 120 Deg F (49 Deg C) /2" PEX Tubing / 50% Glycol / 160 Deg F (71 Deg C) /2" PEX Tubing / 50% Glycol / 180 Deg F (82 Deg C) B22

156 APPENDIX B HEAD LOSS - 5/8" PEX TUBING 30% Glycol 5/8" PEX Tubing / 30% Glycol / 80 Deg F (27 Deg C) 5/8" PEX Tubing / 30% Glycol / 140 Deg F (60 Deg C) /8" PEX Tubing / 30% Glycol / 100 Deg F (38 Deg C) /8" PEX Tubing / 30% Glycol / 120 Deg F (49 Deg C) /8" PEX Tubing / 30% Glycol / 160 Deg F (71 Deg C) /8" PEX Tubing / 30% Glycol / 180 Deg F (82 Deg C) B23

157 APPENDIX B HEAD LOSS - 5/8" PEX TUBING 50% Glycol 5/8" PEX Tubing / 50% Glycol / 80 Deg F (27 Deg C) 5/8" PEX Tubing / 50% Glycol / 140 Deg F (60 Deg C) /8" PEX Tubing / 50% Glycol / 100 Deg F (38 Deg C) /8" PEX Tubing / 50% Glycol / 120 Deg F (49 Deg C) /8" PEX Tubing / 50% Glycol / 160 Deg F (71 Deg C) /8" PEX Tubing / 50% Glycol / 180 Deg F (82 Deg C) B24

158 APPENDIX B HEAD LOSS - 3/4" PEX TUBING 30% Glycol 3/4" PEX Tubing / 30% Glycol / 80 Deg F (27 Deg C) 3/4" PEX Tubing / 30% Glycol / 140 Deg F (60 Deg C) /4" PEX Tubing / 30% Glycol / 100 Deg F (38 Deg C) /4" PEX Tubing / 30% Glycol / 120 Deg F (49 Deg C) /4" PEX Tubing / 30% Glycol / 160 Deg F (71 Deg C) /4" PEX Tubing / 30% Glycol / 180 Deg F (82 Deg C) B25

159 APPENDIX B HEAD LOSS - 3/4" PEX TUBING 50% Glycol 3/4" PEX Tubing / 50% Glycol / 80 Deg F (27 Deg C) 3/4" PEX Tubing / 50% Glycol / 140 Deg F (60 Deg C) /4" PEX Tubing / 50% Glycol / 100 Deg F (38 Deg C) /4" PEX Tubing / 50% Glycol / 120 Deg F (49 Deg C) /4" PEX Tubing / 50% Glycol / 160 Deg F (71 Deg C) /4" PEX Tubing / 50% Glycol / 180 Deg F (82 Deg C) B26

160 ABOUT IPEX IPEX, a leading supplier of hydronic radiant heating solutions, offers an innovative and comprehensive range of heating products throughout the North American marketplace. These products form the WarmRite Floor IPEX Radiant System and include Kitec XPA pipe, PEX tubing, pre-assembled control panels, fittings, accessories and heating controls. With state-of-the-art manufacturing facilities and distributions centers located across North America, IPEX delivers heating solutions for a broad range of markets and applications including: Primary residential heating Supplemental floor warming systems Residential snow and ice melt systems driveways, entrances Industrial heating for factories and warehouses Commercial heating systems stores, offices Institutional heating for schools, hospitals, senior s complexes Industrial snow and ice melt systems parking ramps, loading docks, sidewalks Established more than 50 years ago, IPEX s leading position in the industry is largely due to the IPEX mission to provide its customers with the highest quality products, service and support and to make continuous improvement a core objective of its business. Our marketing strategy in both Canada and the United States is to supply complete systems of pipe, fittings, accessories and all the components required for your heating project. We provide our customers with all the materials they need to ensure the integrity and high performance of their entire system all designed, manufactured and backed by one company. IPEX publishes technical design manuals, state-of-the-art IPEX Radiant design software, product catalogues and supporting literature. We host comprehensive training and education programs tailored to the needs of our distributor, installer, builder and design partners. For more information contact the IPEX office nearest you.