An Introduction to True Modular Boiler Systems

Transcription

1 An Introduction to True Modular Boiler Systems By Floyd A. Burkel Jr., P.E.

2 TABLE OF CONTENTS I. Introduction... 3 II. Types of Boilers... 4 III. Stages of a Boiler operation... 8 IV. Oversizing V. Large Boilers vs. True Modular Boilers VI. Conventional Modular System vs. True Modular System VII. Design of a True Modular Boiler System VIII. Water Distribution Systems IX. Load Calculation Considerations X. Maintenance Benefits of a True Modular Boiler System XI. Energy Savings Documentation XII. Addendum Information to assist in Boiler design Copyright 2014 Floyd A. Burkel Page 2 of 43

3 I. INTRODUCTION The purpose of this course is to introduce you to the True Modular Boiler (TMB) design. The scope is confined to hydronic boilers for space, domestic hot water, water source heat pump, and heating systems. These boilers provide a temperature of 100 F for water source heat pumps, 140 F for potable domestic hot water, and 180 F for space heating. These systems are generally used for apartments, housing projects, condominiums, office building, commercial buildings, churches, schools and hospitals. Most hydronic systems in use today are of the conventional large two boiler design, or less frequently, the conventional modular boiler design. More than 80% of commercial boiler sales are for replacement projects in existing buildings. Most contractors replace the equipment with what s already there. The purpose of this course is to educate you about an alternative system that is far superior and more energy-efficient than these conventional systems. Armed with this knowledge, you will have the confidence to recommend replacing the conventional systems with a flexible and more economical one. That system is the True Modular Boiler (TMB) system design. It is similar to the conventional modular design, but with critical design differences that make it far superior. The TMB utilizes a simple design that uses multiple small modular boilers that are activated sequentially, with all other boilers isolated until needed. The efficiency of its design is most apparent during warmer months, when less than maximum load is needed. Comparisons of the TMB with conventional boiler systems will demonstrate that they are simple to design, require low maintenance, provide energy savings, and Copyright 2014 Floyd A. Burkel Page 3 of 43

4 are cost effective. Their design will provide energy savings of 35-50% over conventional hot water heating systems. The American Gas Association (AGA) gives a 80% combustion efficiency rating to boilers that can provide 75% thermal efficiency under steady-state firing with an average water temperature of 140 F. However, studies show that conventional boilers waste 40% of annual fuel consumption during the boiler s cycling and idling hours. This results in a service efficiency of 30 40%, rather than the expected 70 80%. This course covers the basics of how a TMB system works and the specific differences between it and other systems in use today. The benefits of using a TMB system, as well as the cost savings are discussed. II. TYPES OF BOILERS The different type of hydronic boilers are: Firetube, Watertube, and Cast Iron Sectional. In a Firetube boiler, hot gases of combustion flow through a series of tubes surrounded by water. Alternatively, in a Watertube boiler, water flows in the inside of the tubes and the hot gases from combustion flow around the outside of the tubes. Firetube boilers are more commonly available for low pressure steam or hot water applications, and are available in sizes ranging from 500,000 to 75,000,000 BTU input. They are generally made of steel. Copyright 2014 Floyd A. Burkel Page 4 of 43

5 Watertube boilers are primarily used in higher pressure steam applications and are used extensively for comfort heating applications. They typically range in size from 500,000 to more than 20,000,000 BTU input. They are generally made of copper and steel. Cast iron sectional boilers are another type of boiler commonly used in commercial space heating applications. These types of boilers don t use tubes. Instead, they re built up from cast iron sections that have water and combustion gas passages. The iron castings are bolted together, similar to an old steam radiator. The sections are sealed together by gaskets. They re available for producing steam or hot water, and are available in sizes ranging from 35,000 to 14,000,000 BTU input. Cast iron boilers had a great reputation for quality construction, efficient design and long life. But they were for hand firing gravity feed only. When mechanical firing of oil and gas came into prominence the design and material of boilers likewise changed. Greater combustion volume was required and instead of gradually building up the generation of heat as in hand firing, mechanical firing requires full firing rate within seconds. Cast iron, because of its inelastic characteristics, cannot take this tremendous change in temperature and thus is subject to cracking. Because of this, steel boilers were developed to meet the requirements of mechanical firing. Steel boilers can be designed with more compactness, higher fire boxes, greater furnace volume and more heating surface within a given cubic area. Another important factor is the faster transmission of heat through steel then through cast-iron. Copyright 2014 Floyd A. Burkel Page 5 of 43

6 Key elements of all boilers include the burner, combustion chamber, heat exchanger, exhaust stack, and controls. The combustion chamber, usually made of cast iron or steel, houses the burners and combustion process. Temperatures inside the combustion chamber can reach several hundred degrees very quickly. Heat exchangers may be made from cast iron, steel tube bundles, or, in the case of some smaller boilers, copper or copper-clad steel. The exhaust stack or flue is the piping that conveys the hot combustion gasses away from the boiler to the outside. Typically this piping is made of steel, but in the case of condensing boilers it needs to be constructed of stainless steel to handle the corrosive condensate. Another consideration is whether the exhaust stack will be under a positive or negative pressure. This can determine how the joints of the exhaust stack must be sealed. Boiler controls help produce hot water or steam in a regulated, efficient, and safe manner. Combustion and operating controls regulate the rate of fuel used to meet the demand. The main operating control monitors hot water temperature or steam pressure and sends a signal to control the firing rate, the rate at which fuel and air enters the burner. Common burner firing sequences include on/off, high/low/off and modulating. Boiler safety controls include high pressure and temperature, high and low gas/oil pressure, and high and low water level and flame safeguard controls. Below are some points for consideration when making a comparison between STEEL and CAST-IRON. Copyright 2014 Floyd A. Burkel Page 6 of 43

7 All plate steel is of uniform thickness and each sheet of steel plate is individually tested and stamped by mill inspectors for tensile strength. Boiler plate must pass a minimum test of 55,000 psi. Cast-iron boiler sections are designed and built for minimum thickness but shifting cores may cause water walls to be paper thin and hold on water test but will break out under pressure surge when in operation. Due to limit of design with cast iron it is difficult to obtain sufficient fire box volume or height above the mud ring for ideal mechanical firing of fuels except by extending the length of boiler. Every heating engineer will concur that an overly long firebox is not conducive to good firing characteristics. It is impossible to clean all of the heating services in a cast-iron boiler and a tough job to clean what is available. Whereas it is relatively simple to thoroughly clean the fire tubes of a steel boiler. In order to maintain efficient operation of any boiler the heating services must be kept clean and free of soot deposit. It is also quite easy to maintain clean water surfaces of steel boilers whereas the cleaning of the interior of the cast iron boiler is a major operation and only part of the surfaces cleaned because of the horizontal surfaces that are impossible to clean. This again cuts down on efficiency. Poor circulation of water within a cast iron boiler, due to limit design, has always been a problem. However, exceedingly fast circulation can be accomplished in steel boilers. This is true of steel vertical fire tube boilers. Copyright 2014 Floyd A. Burkel Page 7 of 43

8 Every steel boiler is individually inspected and hydrostatically tested. An insurance company is responsible for every boiler that is sold. A cast-iron boiler is designed and tested to ASME specifications but the testing and assembly does not take place under the supervision of an insurance inspector. It is impossible to permanently weld a cracked cast iron section, whereas, a leak in a steel can be permanently welded or tubes rolled with little difficulty. In conclusion, it is very difficult to guarantee operating efficiencies of cast iron boilers, but easy to attain and guarantee these efficiencies with steel boilers. III. STAGES OF A BOILER OPERATION The stages of a Boiler operation are: Firing, Cycling, Idling, Off-line FIRING: The burner mixes the fuel and oxygen together and, with the assistance of an ignition device, provides a platform for combustion. This combustion takes place in the combustion chamber, and the heat that it generates is transferred to the water through the heat exchanger. Controls regulate the ignition, burner firing rate, fuel supply, and water temperature. Fresh air power burner requires combustion air of one cubic foot per 1000 BTUH firing rate for theoretical perfect combustion. The burners are designed to purge the combustion gases out of the firing chamber volume, hence the larger the boiler input the larger the volume of the chamber requiring more air changes. Pre-purge Copyright 2014 Floyd A. Burkel Page 8 of 43

9 rate of a true modular boiler is approximately 30 seconds. For a large boiler it could be as great as 90 seconds or more. Most large single boilers will fire its burner approximately 30,000 times in a heating season whereas a true modular boiler system will fire 10,000 times in a heating season. CYCLING: A cycle of a boiler burner involves turn on, pre-purge, firing, post-purge, and shut off. IDLING: A large two or three boiler system generally operates with one lead boiler firing and maintaining water boiler temperature. A second boiler will be idling off-line but maintaining water temperature setting. The second boiler is designed to come online if the lead boiler fails, and in the case of a three boiler system, triggers the third boiler to come online in an idling mode. The true modular boiler system has no idling boilers. OFFLINE: As mentioned above, the TMB system has no idling boilers. Boilers are only fired as needed. The rest of the boilers are offline with no flow through. All boilers that are offline in a TMB system have NO LOSSES associated with them, unlike large boilers. Conventional modular systems can have substantial heat loss from the flue, the jacket, and the manifold and are often no more efficient than a single boiler because the modules are not isolated from each other. See Table 1: Comparison of Energy Loss on next page. Copyright 2014 Floyd A. Burkel Page 9 of 43

10 Copyright 2014 Floyd A. Burkel Page 10 of 43

11 IV. OVERSIZING The most important difference between conventional boiler systems and the TMB system concerns the problem of oversizing inherent in the conventional boiler design. There is no industry standard for calculating the energy effects of shortcycling; however, there is recognition of its importance among industry leaders. Preventing short-cycling should be the single most important energy efficiency requirement in both new and existing systems. Why is short-cycling so common today? There are several reasons. One is that we live in a world of partial loads, and those partial loads are smaller than ever before due to large internal heat gains within buildings and changes in building construction (i.e. better insulation and glazing, increased occupancy from property rationalization and increased IT equipment and the related heat increase). It is now common for some buildings to see mild day heating loads that are only 4 or 5 percent of the design heating load. Boiler short cycling is caused when the boiler minimum firing/ boiler capacity exceeds the current system load. For example, the boiler kw output is 100kW as a minimum value but the current system base load is at 50kW. This will cause the boiler to fire for very short periods, as the heat generated (100kW) cannot be used and the boiler will reach set point very quickly and cool down slowly. When your heating system does not require the boiler to fire, the heated water in the boiler's heat exchanger will begin to loose heat to the air around the boiler's casing and through the flue. This loss of heat is not related to any loss of heat in your building. Short cycling is simply the boiler firing up to re-heat the water in its own heat exchanger when that water has cooled down. Because this water heats Copyright 2014 Floyd A. Burkel Page 11 of 43

12 up quickly, the temperature that the thermostat is set to is also quickly achieved and when this happens the boiler is again shut down. The boiler can continue to fire, heating the water in the heat exchanger and shutting down for a prolonged period of time without actually producing any heat for your building. Boiler efficiency is the useful heat provided by the boiler divided by the energy input (useful heat plus losses) over the cycle duration. This efficiency decreases when short cycling occurs. This decrease in efficiency occurs, in part, because fixed losses are magnified under lightly loaded conditions. For example, if the radiation loss from the boiler enclosure is 1% of the total heat input at full-load, at half-load the losses increase to 2%, while at one-quarter load the loss is 4%. In addition to radiation losses, preand post-purge losses occur. Additional energy is lost through radiation and stack loss, as seen in the previous table. The more cycles you have the less energy efficient it will be. See the chart below which compares the typical cycling of a True Modular Boiler system with a conventional boiler system at varying outdoor temperatures. Each system has a total load of 1,200,000 BTUH input at 30% internal and external gains. Copyright 2014 Floyd A. Burkel Page 12 of 43

13 V. LARGE BOILERS VERSUS TRUE MODULAR BOILERS Most design loads of a building in use today, consist of 2 large boilers where each boiler represents 100% of the required load. One is the lead boiler and the second is a backup, or sometimes used for switching the lead boiler to balance the hours of operation. Some large boilers will not go into high fire until the water reaches 140 F. The larger the boiler design, the greater the danger of thermal shock. Most large boilers must operate on low fire until the boiler water reaches 140 F. Then it will go to hi fire. If the boiler goes directly to hi fire on start up, it will cause thermal shock. At 70 degree design temperature, a 2 large boiler system is only efficient at maximum outside temperature (0 F). As the temperature increases, the design becomes more and more oversized. This is because during 70% of the heating system, only 30% of the design load is needed. Most conventional systems for space heating have been designed with their capacity chosen to meet the most extreme load requirement (i.e. The coldest hour of the year). They will still operate at full capacity despite the need for less heat. No credit is taken for thermal contributions from lights, equipment, or people. Excess capacity is also added to bring a facility to required settings quickly after a night setback. This is the OVERSIZING PROBLEM discussed previously. Copyright 2014 Floyd A. Burkel Page 13 of 43

14 It is common to have boiler systems that are oversized for 99% of the annual heating hours, which wastes fuel and significantly increases building owner operating cost due to: 1. Building overheating 2. Boiler idling hours (loss from the flue, jacket, manifolding) 3. Excessive stops/ starts/ pre- /post-purges 4. Boiler pickup load 5. Short firing periods 6. Modulating burner inputs 7. Modulating water flow rates through the boiler 8. Excessive boiler or system temperatures 9. Pickup load of system water 10. Pickup load of cycling burner 11. These large boilers take up more room than modular boilers and the building needs to be designed to allow for replacement in the future because they cannot fit through standard door openings. Many times removable walls are constructed, otherwise, walls and windows would have to be demolished and rebuilt when replacing the large boilers. VI. CONVENTIONAL MODULAR SYSTEM VS TRUE MODULAR SYSTEMS Conventional modular systems do not prevent water flow through between the individual units; therefore, its efficiency is not much better than the large boiler design. Following is a side-by-side comparison of the systems in regard to service efficiency, controls, domestic hot water heating modules, and system installation. Copyright 2014 Floyd A. Burkel Page 14 of 43

15 Copyright 2014 Floyd A. Burkel Page 15 of 43

16 Copyright 2014 Floyd A. Burkel Page 16 of 43

17 VII. DESIGN OF A TRUE MODULAR BOILER SYSTEM The TMB system is a simple design that maintains consistent water volume where heat is required. Outdoor temperatures are monitored through a single sensor while water temperatures are monitored inside the loop. Boilers are activated sequentially, depending on the temperature conditions, with all other boilers remaining isolated; thus no heated water runs through them. When additional heat is needed, water is drawn from the loop into the next boiler in sequence. Boilers are added until the water temperature is sufficient to meet the requirement. The true modular boiler design must have primary/secondary pumping with flow control on each boiler to prevent flow-through of any boiler not calling for heat. The primary/secondary system works by having two piping loops, the primary loop, or building main loop and smaller secondary loops from each boiler, which supply heated water to the primary loop. The main header uses the primary pump while each secondary loop has its own smaller pump. When heat is called for by the system, the secondary loop will provide hot water from the boiler. This water goes directly into the primary loop where it mixes with the cooler return water from the main group of the building. Each secondary loop isolates each boiler from the header in the return water, thereby minimizing the effects of thermal shock. In a TMB system each module/boiler is completely isolated from the other. The system must have the correct controls (very important). It must have: (1) indoor/outdoor reset monitoring return water (2) lead boiler switching (3) ratio testing (from 1 2 )* Copyright 2014 Floyd A. Burkel Page 17 of 43

18 * If set at a 1/1 ratio, the return water temperature will raise a degree for every Fahrenheit degree drop in outside temperature.). When using computer control and monitoring software, it must have these control features. The TMB should be fabricated of boiler steel throughout according to the specifications of the American Society of mechanical engineers (ASME). All of the steel, welds and methods of fabrication are specified by code and regulation, as well as the installation procedure. True Modular Boilers provide a minimum 10-year warranty against thermal shock. You can allow for pickup load in your design, however, in a True Modular Boiler design it would be rare to have all the boilers fire. Therefore, if you add more design BTUH, the extra boiler(s) will just sit there as backup. The TMB systems available in today s market will lend itself to as many as 14 boilers or more on a single supply and return manifold, which allows it to satisfy large load requirements. Any single unit may be removed with no interruption to service. This capability guarantees standby protection against control, burner, and boiler failure. The optimum configuration on a 70 F design would be to use seven (7) modular boilers in lieu of one large boiler (one modular boiler per 10 of design). This will provide optimal efficiency. In considering cost, it has been my experience that the True Modular Boiler System will cost less than a conventional boiler system because it comes piped Copyright 2014 Floyd A. Burkel Page 18 of 43

19 with its own custom electrical harness, which can be quickly connected. Nothing is needed except pipe couplings. The time required to set each boiler is about two hours. They can be moved through standard doorways and transported through stairwells and elevators. These boilers may utilize either gas or oil or both in order to take advantage of the current market price. In addition, TMB systems require only minimal supervision. Once they are set, they will operate by their controls. Additional cost savings come from the fact that there is no need for an expensive service contract or consultant fees. Pay off time on these systems run from seven months to three years. They only require about 40% of the space needed for the large 2 boiler design. They do not require special supervision, and they are computer compatible. We find efficiencies of 83%. They also negate the need for hot water heaters because they have domestic hot water producing capabilities. Because of the small footprint of a TMB system, they can many times be installed without the removal of the existing large boilers. They can be placed where the hot water can be pumped into the existing main, and the large boilers can be valved off. If space is limited, they can be installed in two rows, back to back instead of a singular row (i.e. 2 rows of 3 boilers each, back to back vs. one row of side by side). The Benefits of a true modular boiler design are: A. Can go to Hi Fire immediately. B. Can handle thermal shock. Copyright 2014 Floyd A. Burkel Page 19 of 43

20 C. Minimizes condensate conditions. D. Fewer cycles in a season (approximately 1/10 of the large boilers). E. Primary/secondary pumping (Very Important). F. Automatic backup. G. Match the heating load of the building more accurately than a large boiler. H. No water flow through boilers not called upon for heat. I. Regardless of load design, it will only fire what is needed. J. Will sense indoor heat load from lights, people, or other internal gains K. Multiple applications - domestic hot F, water source heat 100 F and parameter heating to 180 F. L. Provides optimum efficiency and seasonal efficiency for the building. Some or most True Modular Boilers which are a packaged fire tube type can also provide Domestic Hot Water or Water source Heat pump using a copper finned coil inside the boiler water surrounding the fire tubes. These boilers are called a Combination True Modular Boiler. These boilers can be staged just like the space heating boilers, using a bronze circulating pump to maintain 120º Fahrenheit for domestic hot water which feeds by manifold to a Hot Water Storage Tank. A Water Source Heat Pump system uses the same copper finned coil as above, using another circulating pump to maintain 100 degrees Fahrenheit in a separate piping loop. Copyright 2014 Floyd A. Burkel Page 20 of 43

21 Copyright 2014 Floyd A. Burkel Page 21 of 43

22 A True Modular Boiler System Installation A Southern Indiana school of approximately 135,000 sq. ft. wanted to replace their existing boiler system. The old system consisted of two, 4 million BTUH hot water boilers to heat up to 180 F for heating the building. This equates to 29.6 BTUH /sq. ft. per boiler (4 million BTUH divided by 135,000 sq. ft.) for a total of 59.2 BTUH/sq. ft. capability for heating the building with a 70 delta T design. Most engineers design for a worse case scenario and these loads could be as much as 50% over design. Some schools around the Indiana and Kentucky area have been designed with heating loads as much as BTUH/square feet. This demonstrates the oversizing issue discussed earlier. The original plan was to replace the two old boilers with two new ones at the same BTUH input. Instead, I convinced them to install a True Modular Boiler System with primary secondary pumping. It consisted of six (6) boilers, each capable of 800,000 BTUH, for a total load of 4,800,000 BTUH which equates to 35.5 BTUH/square foot (4,800,000 BTUH divided by 135,000 sq. ft.). This is an acceptable design load for the application. This building is now a fair heating design at 35.5 BTUH/square foot. Data collected over a heating season after the new system was installed showed a gas energy savings of 53% over the old system. This new system used only the boilers needed to meet the condition at any given time. For example, a reading was taken when the outside temperature was 20 F. With the children inside, lights on, computers online, doors closed, only one 800,000 BTUH boiler was required to maintain the building at 72 F. Copyright 2014 Floyd A. Burkel Page 22 of 43

23 This boiler was operating at 160 F with the other five not called for. The other five boilers were showing a temperature of 72 F. With an outside temperature of 20 F, this equates to 6 BTUH/sq. ft. required. The water loop at that time was supplying 137 F, and returning at 134 F. This satisfied the building temperature setting at a load of 6 BTUH/ sq. ft., which represents 70 % of the heating design. Copyright 2014 Floyd A. Burkel Page 23 of 43

24 Photos Showing Example of Most Recent Modular Boiler System Installation at Clark Arms Housing, Louisville, KY (October 2014): Copyright 2014 Floyd A. Burkel Page 24 of 43

25 VIII. WATER DISTRIBUTION SYSTEMS In a True Modular Boiler water system it is important to use a primary/secondary pumping and piping system. The primary pumping system involves the sizing of the total GPM needed to satisfy the load of the building with the proper head (FT) pressure. The author uses a rule of thumb of 2 FT of head =1 PSIG. This allows for a little extra flow rate. The primary pumping system provides a hot water loop to the building s heating fixture and back, just like any hot water design for up to F temperature. The fixtures could be baseboard, heat exchangers, HVAC units, or radiators. The way heat is provided to the building is the same regardless of the system design (two large boilers vs. multiple modular boilers). The secondary pumping system is the most important part of the hot water system. This piping and pumping is between the primary main and each modular boiler with valving and flow control. The secondary pump is designed to pump the GPM according to each boiler BTUH input. Copyright 2014 Floyd A. Burkel Page 25 of 43

26 Copyright 2014 Floyd A. Burkel Page 26 of 43

27 Following are photos that show examples of real designs and actual installations of True Modular Boiler systems: Copyright 2014 Floyd A. Burkel Page 27 of 43

28 Copyright 2014 Floyd A. Burkel Page 28 of 43

29 Copyright 2014 Floyd A. Burkel Page 29 of 43

30 The flow control on the secondary piping is very important because it will not allow any primary water flow if it is not calling for heat. Therefore no water flows through any of the modular boilers that are powered down. Most large boilers allow water flow through their boilers by design. This causes energy inefficiencies. The secondary pumping through each modular boiler is controlled by a control panel so that it will be called for as needed according to the return water temperature and outside temperature. However each boiler is designed with a temperature control that delays secondary pumping until the boiler is up to 120 F temperature. This allows each modular boiler to pass through condensates conditions very quickly. This allows for longer boiler life in the case of a fire tube modular boiler design. The four things that reduce boiler life are: 1) Oxygen 2) Condensate 3) Thermal shock 4) Cycles of the boiler Therefore with a closed water loop True Modular Boiler system, the oxygen will be eliminated, condensate will be held to a minimum, the small modular boiler input can handle Hi fire (thermal shock), and the modular boilers cycle less. These items extend the life of a boiler. Copyright 2014 Floyd A. Burkel Page 30 of 43

31 IX. LOAD CALCULATION CONSIDERATIONS Estimating energy requirement and fuel consumption of boiler heating systems for short or long-term operation can be much more difficult than just calculating design heat loss or required heating system capacity. There are many ways to calculate heat loss. Degrees Day Method Bin Method Computer Program Simple Single Measure Method The sophistication of the calculation procedure can often be inferred from the number of temperate ambient conditions and/or time increments used. A simple, single measure procedure may use only one measure, such as Degree Days. Accuracy can be improved by using more information, such as the number of hours anticipated under certain operating conditions, these methods, of which the Bin method is best known, are referred to as simplified multiple measure methods. Factors involved in calculating a heat load for boilers are the efficiency of the boiler system throughout the partial load requirement, as well as the full load requirement. It is called utilization efficiency or seasonal efficiency. This depends on the operation of the equipment, the control arrangement and human habits. The location of the heating boilers and the chimney and the net effect of infiltration often are important in determining the utilization efficiency for heating. Efficiency can vary with the time of year because the average hold on the boiler system Copyright 2014 Floyd A. Burkel Page 31 of 43

32 varies. The closer you can match the heating load of the building at any given time or outside condition, the higher the utilization efficiency of the boiler system. Using a True Modular Boiler system can give this maximum utilization efficiency. Most computer heat load designs are sufficient for an accurate sizing of the boiler system. They take into account wind (infiltration), solar, building materials, architectural features, use, and climate conditions. Internal gains (lighting, piping) are also considered. The goal is to try to match the sizing of the boiler system with a heating load required at any given time of the heating season. Multiple-modular boilers would do a much better job than a large single boiler designed for maximum load. The author has studied actual True Modular Boiler installation and has determined that in most cases the building needs 30% of the load 70% of the heating season. X. MAINTENANCE BENEFITS OF A TRUE MODULAR BOILER SYSTEM 1. Most importantly, maintenance can be done anytime of the heating season due to back up boilers in a True Modular Boiler Water System. An individual boiler can be shut down and cleaned without shutting down the complete system. There is always back up boilers to maintain the water temperature in the system. 2. Easy to clean the fire side and water side of the small boilers. The fire side of a vertical fire tube boiler can easily be cleaned by removing the top of the boiler shell, removing the turbulators and using a wire brush and vacuum to remove Copyright 2014 Floyd A. Burkel Page 32 of 43

33 the residue in the firing chamber. Most closed loop hot water boilers do not need to be cleaned. 3. The PH only needs to be checked annually. There is not a lot to do since a closed water loop system has what they call dead water. The water has been cleaned of oxygen and has no properties to corrode the system. 4. Due to their compactness, it is easier to clean a smaller burner verses a large burner. 5. A copper coil for domestic hot water can be back flushed with cold water and most of the scale will come off. The copper coil can be cleaned with a chemical solution. 6. The inspections are very simple with the True Modular Boiler System they are inspected through the small ports on the boiler (1 ½ inches in diameter). Large boilers have large ports which must be removed for inspection which makes it a much longer process. 7. No fire brick to replace due to small combustion chambers. Most True Modular Boiler Systems are water jacketed which means minimum refractory in the combustion chamber, leading to long life. The fire brick and refractory require frequent replacement in large boilers. Copyright 2014 Floyd A. Burkel Page 33 of 43

34 XI. ENERGY SAVINGS DOCUMENTATION Copyright 2014 Floyd A. Burkel Page 34 of 43

35 XI. ENERGY SAVINGS DOCUMENTATION Copyright 2014 Floyd A. Burkel Page 35 of 43

36 XI. ENERGY SAVINGS DOCUMENTATION Copyright 2014 Floyd A. Burkel Page 36 of 43

37 XI. ENERGY SAVINGS DOCUMENTATION Project 4: Kentucky 1-1 Clarksdale Housing Complex Space Heating and Domestic Hot Water Combination Boilers Note: This was a renovation of 4 boiler rooms over a 4-year period, in which time the cost of gas increased by 157%, but substantial savings of 18% were still realized. Fuel Savings Evaluation Renovation Heat/DHW Y R Therms Consumption August Cost per Therm Total $ Cost Therm D/D Prior to Renovation 1 Gas 1,404,261 Oil 205,100 1,609,361 $.1800 $.7143 $252,767 $146,500 $399, Renovation of Boiler room #1 2 Gas 1,333,074 Oil 35,280 1,368,354 $.2426 $.7143 $323,404 $ 25,206 $348, Renovation of Boiler room #2 3 Gas 1,404,173 $.2990 $419, Renovation of Boiler room #3 4 Gas 959,388 $.3600 $345, Finished renovation of all Boiler rooms 5 Gas 867,857 $.4370 $379, After Renovation 6 Gas 704,943 $.4640 $327, RESULTS 56.2% Decrease in TOTAL Therms used 157% Increase in Gas Cost 18% Decrease TOTAL COST 51.32% Decrease in Therms Per DD Copyright 2014 Floyd A. Burkel Page 37 of 43

38 Copyright 2014 Floyd A. Burkel Page 38 of 43

39 XII. ADDENDUM INFORMATION TO ASSIST IN BOILER DESIGN Definition of Degree Day A degree day is defined as the difference between 65 F and the average of the high and low temperatures in a given day. The higher the number, the more fuel will be used in heating. Example: December 25 Chicago Midway Airport Thus, December 25 was a 36 day. Maximum temperature = 34 F Minimum temperature = 23 F Average = 29 F 2 65 F - 29 F = 36 F Although in general the degree day reading is accurate, other factors, such as excess of infiltration due to high winds or sun load, which affect the heating requirements of the building, are not taken into consideration by the degree day. In addition it should be remembered that the degree day number is not a true average, since only two readings in a 24-hour period are used. Copyright 2014 Floyd A. Burkel Page 39 of 43

40 XII. ADDENDUM INFORMATION TO ASSIST IN BOILER DESIGN Copyright 2014 Floyd A. Burkel Page 40 of 43

41 XII. ADDENDUM INFORMATION TO ASSIST IN BOILER DESIGN TABLE 1 HOT WATER DEMAND IN FIXTURE UNITS * In applications where principal use of showers is at end of shift, as in industrial plants, use conversion factor of 1.00 to obtain Design Water Flow Rate in GPM. For gyms, schools or field houses where load is on for minutes with a minute recovery period, treat it as a Periodic Peak Type Load. In Dormitories, Nursing homes and Hotels, showers may be included as part of the total load in conversion factor applied, as given in Table 2 Conversion factors for determining design water flow in GPM from total fixture units (check with capacity of hot water main to evaluate sustained peak load requirement). Copyright 2014 Floyd A. Burkel Page 41 of 43

42 TABLE #1 - Determines hot water flow rate in individual type fixtures for various types of buildings. XII. ADDENDUM INFORMATION TO ASSIST IN BOILER DESIGN TABLE 2 CONVERSION FACTORS FOR DETERMINING DESIGN WATER FLOW IN GPM FROM TOTAL FIXTURE UNITS For Domestic Hot Water Sustained Type Load in Buildings (i.e. Hospitals, Hotels, Office Buildings, etc.) Copyright 2014 Floyd A. Burkel Page 42 of 43

43 XII. ADDENDUM INFORMATION TO ASSIST IN BOILER DESIGN TABLE 3 MAXIMUM USAGE FACTORS TABLE #3 Diversity factor for converting gallon per minute flow for specific type of buildings. Copyright 2014 Floyd A. Burkel Page 43 of 43