Product and Technical Seminar April 16, 2013 FCX Oil fired Condensing Boiler

Transcription

1 Product and Technical Seminar April 16, 2013 FCX Oil fired Condensing Boiler Introduction Geminox France s leading manufacturer of steel boilers, part of Bosch Thermotechnik. Lucky Distributing Exclusive importer of the Geminox FCX Oil-Fired Condensing Boiler Quintessence Corporation Fairbanks Master Dealer Seminar Organization 1. Introduction 2. The FCX and DHW Tanks - Features and Benefits 3. Break, Coffee, Donuts, Hands on examine the features discussed 4. Condensing Technology how it works and why it is the most efficient choice 5. New Construction, Retrofits, Testimonials, Warranty and Support 6. Break About every hour - Pizza for lunch 7. Venting/Stacks 8. Hydronics - Return Water, Tempering, Pumping, Heat Emitters, Injection Pumping, Baseboard, Handling the Condensate, Controls, Maintenance 9. Optimization 10. Website Tour, Hands on The FCX Boiler - Features and Benefits Most efficient oil-fired boiler sold in the US Small footprint, attractive, very quiet Two sizes 76 Kbtu and 104 Kbtu (same physical size) Riello Burners the most reliable name in the industry High-pressure pump In-line oil heater Dual air adjustment coarse and fine Blocked vent safety Built-in features: Expansion tank Mixing valve Grundfos pump Plug and play to your manifolds. Two temperature circuits Mixed for low temperature radiant High temperature that does not contaminate the cooler return water with the hot return water The advantage of a separate secondary condenser Stack: Less expensive, easily worked plastic, many options Additional standard safeties not required for residential boilers High water temperature safety 1

2 High stack temperature safety SPDT switches on above switches for add on alarms Built for radiant heat but works well for baseboard Close technical support Comprehensive instruction manual Efficiency & fuel savings Savings you can expect replacing a convential boiler 30% to over 50% DHW Tanks Sizes available 25, 40, 50, & 80 gallon Thermometer Aquastat Special connection for hot recirculation Built for low temperature boilers Recovery rates & sizing Sizing Works on water Break, Coffee, Donuts, Hands on examine the features Condensing Technology How is heat recovered? What is condensing? Why is it more efficient? Lower Temperatures Precautions/special materials Conventional Boilers a few facts Conclusions New Construction Radiant Homes a no-brainer Retrofits Options & Limitations Considerations Is the boiler big enough? Can you extract adequate heat from the boiler at lower temperatures? Auxiliary heat sources Old construction Radiant Can you use lower temperatures than now used Factors affecting the need for High water temperatures Poor insulation Bad Windows Air Leaks Few heat emitters Location Hills or Holes Brookhaven National Labs baseboard study A case for baseboard 2

3 My Home Warranty and Support 10 Years for Heat Exchangers and DHW Tanks 2 years on other parts Standard Riello warranty Comprehensive installation manual Close technical support to the designer, installer, and serviceman Fairbanks Initial setup and tuning included Testimonials Proof positive boiler comparisons Venting / Stacks Concentric Options Side wall - Up and out Side wall - Straight out Condensate drain tees Single Wall Options Vertical best choice Horizontal caution recommended Back drafting Even in sealed boiler rooms Manufactured condensate tee Single wall balanced - Direct connection to boiler Combustion Air During construction Consider a Filter Dirty filters Back drafting Hydronics - Unique to Condensing Return Temperatures The key to greater efficiency Return water temperatures must be below 115 F, the threshold where condensing begins Brookhaven Laboratory study has confirmed this 100 F or less out and 75 to 80 F return works best 130 F out and 110 F provides some condensing FCX counter flow Do NOT temper the return water Immune to boiler shock No tempering circuits/valves No recirculation pumps No 4-way mixing etc. No Injection recirculation loops The 2nd most important event in condensing boilers Pumping The more the better??? old school Variable Frequency Drive (VFD) the best way 3

4 T, P, Mixing Pumps Slow, nearly continuous pumping at lower temperatures The pumping can have a great effect on efficiency Heat Emitters High Mass the best for condensing Lowest temperatures needed Staple Up don t do it, requires water 30 F greater Radiant Panels pricey, but probably can use lower temperatures Baseboard Super Baseboard Unit heaters and other low mass The key is lower return water temperature Return water temperatures - Ways to drop them Preheat domestic Unit heaters Heat HRV incoming air On dual systems put baseboard through a radiant section Plastic stack robber Remember LOW return water temperatures are the key, not high supply water temperatures. Injection Pumping Diagram - do not Diagram - do Handling the Condensate Neutralization and Disposal Neutralization Traps - how to do it Is it necessary? Disposal Down the drain Pump it away Cold drains ph of common household substances Actual Measurements Lifewater system Covered in the new Geminox manual Controls Cold start vs. Hot start Reset controls and suitability Temperature Mixing DHW Boiler protection Causes for sustained condensing in primary Large structure / lots of high mass emitters Too much throughput 4

5 Maintenance Cleaning and Inspection Once a year or every 1000 gallons Non-condensing mode and sooting Primary condensing What to check for Secondary condensing (washing the tubes Concentric air tee - need for inspection Plugged condensate drains Back drafting Tuning a condensing boiler Slides with charts CO2, O2, CO Levels Excess Air New Chart Smoke Enhancing Optimizing the Condensing Boiler White paper Website Tour Informational and Technical Website End of Presentation Tour of CCHRC Facility if time permits??? Visual Aids / Publications / Handouts / Notes Binder inclusions Course Outline FCX Literature Price Sheet FCX Manual Riello Manual Centrotherm Catalog Parts & Pieces FCX 22, FCX 30, and BS 50 DHW Tank Concentric and single wall venting Condensate Tee Heat Wise Burner 2363 Filter 5

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7 Geminox France s Leading Manufacturer of Steel Boilers Part of Bosch Thermotechnik Lucky Distributing Exclusive importer of the Geminox FCX Oil-Fired Condensing Boiler John Jansen President & CEO Bill McConaughy Sales Alaska / Canada Quintessence Corporation Fairbanks Master Dealer Jim Romersberger President Special Technical Representative

8 Seminar Organization 1. Introduction 2. The FCX and DHW Tanks - Features and Benefits 3. Break, Coffee, Donuts, Hands on examine the features discussed 4. Condensing Technology how it works and why it is the most efficient choice 5. New Construction, Retrofits, Testimonials, Warranty and Support 6. Break About every hour, Pizza for lunch 7. Venting/Stacks 8. Hydronics - Return Water, Tempering, Pumping, Heat Emitters, Injection Pumping, Baseboard, Handling the Condensate, Controls, Maintenance 9. Optimization 10. Website Tour, Hands on

9 92-97% Efficient The Most Efficient Oil-Fired Boiler

10 The FCX Boiler Features and Benefits - 1 Small footprint, attractive, very quiet Two sizes 76 Kbtu and 104 Kbtu Output Riello Burners the most reliable name in the Industry High pressure pump In-line oil heater Dual air adjustments coarse & fine Blocked vent safety

11 The FCX Boiler Features and Benefits -2 Built-in features: Expansion tank Mixing valve Grundfos pump Plug and play to your manifolds. Two Temperature circuits Mixed for low temperature radiant High temperature that does not contaminate the cooler return water with the hot return water. The advantage of a separate secondary condenser

12 The FCX Boiler Features and Benefits - 3 Stack: Less expensive, easily worked plastic, many options Additional standard safeties not required for residential boilers High water temperature safety High stack temperature safety SPDT switches on above safeties for add on alarms Built for radiant heat, but can work with baseboard Close technical support to the designer, installer, and servicer Comprehensive Installation Manual

13 The FCX Boiler Features and Benefits - 4 Efficiency & Fuel Savings Savings you can expect replacing a convential boiler 30% to over 50%

14 Sizes Available 25, 40, 50, & 80 Gallon Thermometer Aquastat 100% 316 L Stainless Steel Special connection for hot recirculation Built for low temperature boilers Comparison of recovery rates & Sizing Works on water DWH Tanks

15 CONDENSING BOILER TECHNOLOGY Principles involved, and why it offers the most efficient solution in residential and commercial heating. James Romersberger Quintessence Corporation

16 Condensing Technology How Heat is Recovered? There are Two Processes by which heat is recovered from the burning of fuel. Reduction of the burn temperature (sensible heat). Oil burns at about 4000 F, the stack temperature normally is about 350 F. Further reduction leads to the 2 nd Process. Recovering of the latent heat of vaporization (latent from the Greek root word meaning hidden). This is the condensing part.

17 Condensing Technology What is Condensing? The products of combustion consist primarily of CO2 and Water Vapor. Condensing refers to the cooling of the stack gasses to the point where the water vapor condenses into liquid. It does not refer to the water circulating in the boiler.

18 Condensing Technology How does Condensing Make for Greater Efficiency? When water changes state from a gas to a liquid (goes from a gas at 212 to liquid at 212 ), it gives off heat that is absorbed by the water in the boiler. Think of it as just the opposite of adding heat to make water boil. This process recovers the latent (hidden) heat of vaporization, takes place in the condenser, and is added back into the Boiler water. The net result is greater efficiency.

19 Condensing Technology Added benefits Lower Temperatures Condensing boilers are defined by: Lower Stack Temperatures (80 to 175 ) Lower water supply temperatures (100 to 120 ) Lower water return temperatures (75 to 100 ) Non-condensing conventional boilers have stack temperatures of 300 to 450 F, and return water temperatures of about 130 F in order not to condense. Any heat up the stack is LOST

20 Condensing Technology Why is Condensing Bad for Conventional Boilers? It s the nature of the condensate, it is slightly acidic. Measured values around Fairbanks are about ph 4. The stack can be destroyed in year or less, creating a fire hazard. Note that the stainless steel in Metalbestos types of stacks will also fail, because not all stainless steels are created equal. Life expectancy of the boiler will be greatly reduced. Conventional boilers are not designed to condense.

21 Condensing Technology Conventional Boilers a few FACTS Fact Any conventional boiler can be made 5% to 10% more efficient by making it condense. But if this is done, the acidic condensate will destroy them. Fact Conventional boilers are designed to run hotter in order not to condense. Efficiency is secondary Fact The primary purpose of the very expensive insulated stove pipe is designed to hold the heat in so the flue gases won t condense. Fact The hotter the boiler, the less efficient it runs, and Any heat up the stack is LOST

22 Condensing Technology Conclusions Lower temperatures mean greater efficiency Every degree you lower the stack temperature increases both the sensible heat recovery (from lower stack temperatures) and the latent heat recovery (from the condensing effect). Lowered temperatures are directly translated to $$$ saved. THE BOTTOM LINE Any heat up the stack is LOST

23 New Construction A No Brainer

24 Considerations: Retrofits Options & Limitations Is the boiler big enough? Can you extract adequate heat from the boiler at lower temperatures? Auxiliary heat sources Old construction radiant it will generally work if high mass, not with staple-up Can you use lower water temperatures

25 Factors Affecting the Need for High Water Temperatures Factors: Poor insulation Bad Windows Air Leaks Few heat emitters Location Hills or Holes

26 Hydronic Baseboard Thermal Distribution System with Outdoor Reset Control to Enable the Use of a Condensing Boiler Dr. Thomas A. Butcher October, 2004 Brookhaven

27 A Case For Baseboard My Home: 3,000 sf heated, 2,000 shop and basement built into a hill, with residual heat only 2x8 walls with blown-in fiberglass, and triple pane windows, 1000 ft elevation 108 ft baseboard, no radiant, no unit heaters, pumping 120 to 130 F water All return water goes through a DHW heat exchanger gets 10 F temperature 35 ft x 4 inch plastic stack serves as stack robber, 80 to 120 F exit flue temperature, depending on burn cycle Bacharach measurements: at boiler 91.5%, at top of 3 rd floor exit 96% 53 gallon Burnham DHW indirect heater on Zone no priority never out of hot water House Heat Recovery adequate, no setback used

28 Warranty & Support 10 Years for Heat Exchangers and DHW Tanks 2 years on other parts Standard Riello warranty Comprehensive installation manual Close technical support to the designer, installer, and serviceman Fairbanks Initial setup and tuning included

29 Testimonials Proof Positive Boiler Comparisons

30 Venting / Stacks Concentric Options - Balanced Side Wall - up and out Side Wall - straight out Vertical Condensate drain tees Single Wall Options Vertical best choice Horizontal caution recommended Manufactured condensate tee Single Wall balanced Direct to boiler

31 During construction Consider an Air filter Clogged air filter Venting / Stacks Combustion Air Known Problems Back drafting and negative pressures - Even in sealed boiler rooms

32 Hydronics Unique to Condensing **** Return Temperatures***** The key to greater efficiency Return water temperatures must be below 115 F, the threshold where condensing begins Brookhaven Laboratory study has confirmed this 100 F or less out and 75 to 80 F return works best 130 F out and 110 F provides some condensing The single most important event in condensing boilers

33 Counter Flow Heat Exchanger Counter Flow Heat Exchanger Hot Return Cool Return Hot Supply Mixed Supply 1. Combustion gasses rise thru the Primary and continue down through the Condenser and then to the flue. 2. Water flows counter to the direction of the gasses and enters the bottom of the condenser. 3. The flue gas is cooled enough to condense, and this adds the latent heat of vaporization into the water.

34 Hydronics Unique to Condensing Do NOT Temper the Return Water Immune to boiler shock No tempering circuits/valves No recirculation pumps No 4-way mixing etc. No Injection recirculation loops The 2nd most important event in condensing boilers

35 Hydronics Unique to Condensing Pumping The more the better??? old school Variable Frequency Drive (VFD) the best way T, P, Mixing Pumps Slow, nearly continuous pumping at lower temperatures The pumping can have a great effect on efficiency

36 Hydronics Unique to Condensing Heat Emitters High Mass the best for condensing Lowest temperatures needed Staple Up don t do it, requires water 30 F greater water temperature Radiant Panels pricey, but can use lower water temperatures Baseboard and Super Baseboard Unit Heaters and other low mass The Key is lower water return temperatures

37 Emitter evolution There are several ways to design modern hydronic distribution systems around the low water temperatures that enhance the performance of renewable energy heat sources. Let s start with the heat emitters. That term refers to any device intended to remove heat from water flowing through it and release that heat into the room where it is located. Click to enlarge Figure 2. Photo courtesy of Smith s Environmental Products Many building owners in heating-dominated climates are used to the look of fin-tube baseboard. While most don t relish it as a visual enhancement of the room, they understand its purpose and accept it as a necessary part of the building. The latest development in low temperature fin-tube baseboard is shown in Figure 2 with a product called Heating Edge that is currently made in the UK, but available in North America. From the outside it looks very similar to other fin-tube baseboard, but what s under the hood is very different. Heating Edge baseboard has much larger fins than traditional baseboard. The fin area is about three times larger, almost filling the entire space within the enclosure. It also has two ¾-in. copper tubes running through those fins. The tubes can be piped either for parallel flow or in series. In the latter case, the hottest water flows down the upper tube, makes a U-turn at the end and flows back along the lower tube. Assuming an average water temperature of 110ºF, this baseboard releases about 290 Btu/hr./ft., when the two pipes are configured for parallel flow and the total flow rate through the element is 1 gpm (0.5 gpm through each tube). This increases to about 345 Btu/hr./ft., with a total flow rate of 4 gpm (e.g. 2 gpm per tube). If the two tubes are configured for series flow (hot along top and return along bottom), the output at 1-gpm flow rate drops about 10%. Consider a 12-ft. by 16-ft. room in a well-insulated home with a maximum heating load of 15 Btu/hr./ft.2 The room s maximum heating load is thus 2,880 Btu/hr. This could be handled by a 10-ft. length of Heating Edge baseboard operating at an average water temperature of 110ºF and 1-gpm flow rate. To produce equivalent output, a 10-ft. length of conventional residential baseboard would require an average water temperature of about 150ºF. The latter temperature would dramatically lower the efficiency of solar thermal collectors. Reprinted from Oct 2012 PME Exert from Article By John Siegenthaler P.E. October 1, 2012

38 07/03/2002 Plateless In Radiantville John Siegenthaler, P.E. A one-size-fits-all approach to radiant tubing installation can land you in hot water. John Siegenthaler P.E. Plateless In Radiantville John Siegenthaler, P.E. By John Siegenthaler P.E. A one-size-fits-all approach to radiant tubing installation can land you in hot water. I m writing this column at the end of what has been a long and at times discouraging week. All told, I ve received three what went wrong with this system calls. All involved plateless staple-up radiant floor installations in which tubing was stapled directly to the underside of a wooden floor deck. In the first case, the 1/2-inch PEX tubing that was stapled to the underside of the plywood subfloor was migrating. The installer told me that some tubing runs had moved about 2 feet since being stapled in place. The system was also making objectionable ticking sounds each time the zone thermostat called for heat. Ticking sounds due to expansion/contraction movement of the tubing are an all too familiar complaint in such systems, especially when reset control is either not used, or is not properly adjusted. However, the migration of the tubing was a new one for me. The only thing that came to mind was that the staples were installed at an angle, and thus allowed a ratcheting effect to occur in which the tube moved past the staple while expanding, but was prevented from returning when it cooled. Needless to say, the owner of this system was not happy. The installer was trying to resolve the issue as amicably as possible. We discussed several possibilities for remedying the situation. Unfortunately, the tubing was already closed in behind a drywall ceiling. It was too late to consider what I m sure would have made a major difference in performance heat transfer plates. That option gone, we moved on to implementation of reset control with the proper settings that would allow almost continuous circulation through the system. The less on/off cycling, the less piping movement, and, hence, the less ticking. Incidentally, upon inspecting the job, a representative of the tubing manufacturer found that the staples used were not the staples sold by his company (even though they were obtained from another tubing manufacturer for exactly the same purpose with the same type of tubing). The use of nonbrand-x staples was hence cited as the cause of the problem. Two days later I got a call from another very reputable radiant installer who was retained to perform triage on another plateless staple-up installation. In this one, the tubing was stapled to the underside of the subfloor about every 3 to 5 feet. The heat transfer plates were omitted because the original installer considered them too expensive and unnecessary. Mind you this system was installed in a house that probably cost about $500,000. Again, the problem wasn t discovered until the tubing was rendered inaccessible by a drywall ceiling. Minimal amounts of underside insulation were used, and adding more was now next to impossible. I have every confidence the radiant doctor will do his best with what he has to work with, but thermal miracles are hard to come by. In the end, the original installer may be convinced that heat transfer plates and proper underside insulation really are less expensive than defense attorneys. Three Strikes The last call came from a company just getting started with radiant floor heating. The plateless staple-up was installed under bedroom floors covered with carpet and pad. One inch of foil-faced foam insulation board was pressed up against the underside of the tubing. The space below this insulation was a partially heated basement. The water temperature to the floor circuits was regulated by an injection mixing system, and reached 148 degrees F at -10 degrees F outdoor design. Guess what the complaint was? You got it inadequate heat output in the carpeted rooms. The owner was dissatisfied and withholding the remaining payment for the system. This is the hard way to Copyright 2002, Plumbing & Mechanical. Reprinted with permission. All rights reserved. Obtain additional permission by typing into any browser window. icopyright Clearance License

39 Page 2 be initiated into the radiant heating business. I ve long held reservations about universal use of plateless staple-up radiant installations. In my opinion, they re a possibility only in situations where the required upward heat flux is less than 15 Btu/hr/sq. ft. They may be suitable for rooms having mostly interior walls, floors, and ceilings, but not a ski chalet with 25-foot ceilings, and a gable full of glass. In addition to complaints of inadequate heat output, some plateless staple-up systems have caused serious thermal degradation of finish floors. The problems have included cracked ceramic tiles, color striping of vinyl flooring, carpet, and warped hardwood floors. Most of these problems are the consequence of poor heat diffusion from the stapled tubing to the other flooring materials. I call this situation thermal constipation. The heat is there in the tubing; it just has a very difficult time flowing outward and upward through the remainder of the flooring sandwich. The contact area between the stapled-up tubing and the subfloor is often a tiny percentage of the overall surface area of the tubing. The situation only gets worse when the tubing is filled with water and operated at high temperatures. It s not long before the tubing looks like wires drooping between utility poles. This severely limits conduction heat flow. Convection and radiation are the only remaining vehicles to move the heat, and neither has good geometry with which to do so. Oversimplified It seems that too many installers have the notion that the plateless staple-up method is all they need to know about installing radiant tubing. Many assume that cranking up the water temperature is the solution for areas having higher heat loss. Some will even tell you not to waste too much money on underside insulation because everyone knows that heat rises. Where do these installers get the idea that plateless staple-up is a one- size-fits-all approach to radiant? Certainly part of the problem is that they don t know (or at least respect) the fact that conduction heat transfer requires ample contact area between the tubing and the other materials in the floor. There s nothing magical about PEX, PEX-AL-PEX, EPDM, or copper tubing that allows any of them to sidestep basic physics. If plateless staple-up is such a versatile installation method, why wasn t it used with copper tubing during the radiant boom of the 1940s and 1950s? Why wasn t it around when PEX tubing made its initial appearance in the North American market in the early 1980s? Why isn t it currently used in Europe? Do I dare suggest that some installers are simply too and I ll be gentle disinterested to inform themselves about where plateless staple-up works, and where it doesn t? The same question applies to some wholesalers, and Web-based distributors of radiant heating hardware. I think it s time for everyone involved in the sale of tubing for floor heating applications, from manufacturers on down, to reassess their criteria on where plateless staple-up installations are appropriate. It s time for installers to know when tubing suppliers will and won t stand behind this type of installation. Sure, plateless systems cost less than plated systems. Likewise, three lengths of flex duct dangling from bailing twine cost less than a properly designed and installed forced air distribution system. Roll roofing costs less than 30-year warranted shingles. A light bulb screwed into a porcelain base costs less than a chandelier. Isn t it odd that most buildings in which plateless staple-up radiant heating systems are installed don t use roll roofing, or light bulbs screwed into porcelain bases? No Excuses Required Radiant newbies often feel that because the competition is willing to roll the dice with a questionable plateless installation, they should also temporarily forget about thermodynamics to get the job. Further pressure for such a decision often comes from a thrifty but technically uninformed owner who flashes a lower price quotation when the cost of doing it right is presented. What s the point of installing a $20,000 system that stands a better than average chance of generating complaints or even litigation, rather than a $23,000 system that generates higher profits and referrals? The radiant industry is about selling comfort, quality, and efficiency. Those who choose to do otherwise should move on before scarring the market for those who want to do it right. Those who will prosper in the radiant heating industry are those who take the time to learn about and respect the basic heat transfer principles involved in each type of installation. Professionals who know what it takes to do the job right, and are prepared to politely walk away when circumstances require otherwise. Footnote: By the time you read this, the results of an ASHRAE research project in which several types of radiant floor constructions (including plateless staple-up) were tested under controlled laboratory conditions should be released. Initial interpretation of the results indicate a substantial increase in floor heat output when plates are used in staple-up installations. If you install staple-up radiant systems, I urge you to review the findings of this report and incorporate them into your design and installation decisions. Copyright 2002, Plumbing & Mechanical. Reprinted with permission. All rights reserved. Obtain additional permission by typing into any browser window. icopyright Clearance License

40 Hydronics Unique to Condensing Return Water Temperatures Ways to drop them: Preheat domestic Unit heaters Heat HRV incoming air On dual systems put baseboard through a radiant section Plastic stack robber Remember LOW return water temperatures are the key, not high supply water temperatures.

41 Hydronics Unique to Condensing Considerations for Injection Pumping

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44 Neutralization and Disposal Neutralization Traps - how to do it Is it necessary? Disposal Handling the Condensate Down the drain Pump it away Cold drains

45 Flue gas condensate Typical household sewage Oil Gas Acidic ph-value Basic Battery acid Gastric acid Lemon juice Handling the Condensate ph VALUES OF VARIOUS FLUIDS Condensate the NON-Issue Vinegar Rain water ASHRAY Presentation by Jim Cooke Mechanical Solutions NW, Nov 2005 Clean rain water Distilled water (neutral) Tap water Lake water Ammonia

46 Handling the Condensate Actual Measurements after several months indicate a ph level of 7.0 Neutral. Unless required by code this is not really necessary. Covered in the Geminox Manual.

47 Cold start vs. Hot start Reset controls and suitability Temperature Mixing DHW Boiler protection Controls Causes for sustained condensing in primary Large structure / lots of high mass emitters Too much throughput

48 Maintenance Cleaning and Inspection Once a year or every 1000 gallons Non-condensing mode and sooting Primary condensing What to check for Secondary condensing (washing the tubes) Concentric air tee - need for inspection Plugged condensate drains Back drafting

49 Maintenance Tuning a Condensing Boiler Slides with charts CO2, O2, CO Levels Excess Air Smoke

50 WATER VAPOR DEW POINT o F o C Natural Gas (95% CH 4 ) CO 2 % of flue gas influences dew point temperature Dew point water vapor Higher CO 2 =Higher Dew point =More Condensation Lower CO 2 =Lower Dew point =Less Condensation CO 2 in Vol %

51 Maintenance Tuning a Condensing Boiler

52 Enhancing and Optimization Of Condensing Boilers By James Romersberger 7/16/12

53 Enhancing and Optimization Of Condensing Boilers By James Romersberger 7/16/12 Introduction Condensing boilers have been in use in the US for some time now, and the principles regarding their operation are generally known. However, there is little practical information to draw on in actually applying these principles to piping systems. And I have found no detailed information which attempt to optimize these systems. What I have seen in the use of radiant technology in general is the replacement of baseboard systems with radiant floors with no attention to radiant system design (installers have by and large just put the pipes in the floor and continued as usual). With regard to using condensing boilers I have seen the same (just stick in a condensing boiler where no attention is given to optimizing the design). Aside from the fact that residential and light commercial systems are rarely ever designed, it is a fact that if you properly design a system for a conventional boiler, but replace it with a condensing boiler, and all things being equal, the condensing boiler will out perform the conventional boiler. The reason is that the condensing boiler s heat transfer is more efficient even if it is not running in condensing mode. It is designed for maximum extraction of heat rather maintaining a minimum stack temperature to prevent condensing. This paper is intended to open up a discussion on the optimization of condensing boilers, and how they can be more effectively used in all applications whether new construction or higher temperature systems normally found in retrofits. It is not intended to provide solutions to any particular situation, but to open up the field of options. It is also intended to promote awareness of the underlining principles of condensing boilers. It does assume a general knowledge of how condensing boilers work. For a good refresher on condensing visit Factors Affecting Efficiency of Condensing Boilers The Key Factor Everyone remembers the cliché regarding the three most important principles/rules of real estate are: Location, Location, and Location. Well, the main principle of condensing in any furnace or boiler can likewise be summed up as: Reduce flue gas temperature. In boilers the main ingredient that affects this is Return Water Temperature to the Condenser, although recovery of heat directly from the stack can also be significant. Notice that I didn t say Return Water Temperature to the Boiler but to the Condenser. These can be two different things. Page 1 of 5

54 Practices to Avoid There are many sound installation practices that are acceptable for conventional boilers, but violate this principle and will drastically reduce the efficiency of a condensing boiler. Most of these involve tempering the return water. Here are some examples that produce undesirable results: 4- way mixing valves, recirculation pumps, recirculation injection loops, pressure by-pass valves, and anything that tempers the return water should not be used. Over pumping and using too high of a mix also reduces the T and raises the return temperature. Imbalanced pumping between injection pumps and supply pumps will also raise return temperatures, producing high temperatures when not needed. In a conventional boiler this last is not particularly an issue, but when using a condensing boiler, it is critical. Reduced Return Temperatures Remember, the controlling factor is reduced return water, not supply temperatures. But lower supply temperatures generally translate to lower return temperatures. So if higher supply temperatures are needed we need to further increase the T in order to more effectively utilize the efficiencies that come with condensing. More on Temperatures I see publications use the phase when running in condensing mode. First of all what does this mean? It means that if you cannot get the flue gases below a certain temperature, the boiler will not condense. The next section discusses this. However, most of these publications refer to new construction, so why have a system that runs in non-condensing mode at all. There are times when this may occur but it can be minimized and sometimes we are working with existing systems that require elevated temperatures. The point is systems should be designed for the lowest water temperatures possible. While a 10-degree difference may does not affect the efficiency of a conventional boiler, it certainly does with condensing boilers. Fuel The operating characteristics of a system are also influenced by the fuel used. The reason is that different fuels have different properties that affect condensing. The major two are Natural Gas (gas) and Fuel Oil (oil). Gas condenses at higher temperatures than oil. This means it is easier to make the flue gasses condense. Under ideal conditions, gas will condense at about 131 F, while oil stack gasses must be reduced to about 115 F. The reason is gas (CH4) has more hydrogen in it than oil, and thus more water, and thus a higher dew point. But even though gas is more forgiving of higher temperatures, higher efficiencies can be obtained the more the stack temperature is reduced. Boiler Design and Configuration. The type of condensing boiler also influences the operating characteristics of a system. There are two basic configurations used today. They are single heat exchanger/condenser vs. a primary heat exchanger and a secondary condenser. The single heat exchangers are made from stainless steel. Although expensive to make, there are advantages. One is that they can run at very low temperatures that promote great condensing, and in the case of gas, they can modulate the BTU output thereby producing the amount of heat needed at the temperature needed. The trade off with single heat exchangers is that there is one supply and one return. So although two supply Page 2 of 5

55 temperatures are easily managed, all return water is mixed thereby raising the total return temperature (the cool return is contaminated with the hot return) and this results in decreasing efficiency. There is no way to operate at maximum efficiency when supplying water in both modes simultaneously. The primary/secondary types are ideally suited for multiple temperature returns. High temperature water returns to the primary, and low temperature water to the secondary condenser. However, if the primary is cast as opposed to welded steel the boiler shock issue needs to be accounted for. So the key factor to remember here is that in these systems not all of the return water needs to be used for cooling the condenser. They can operate in condensing and noncondensing mode simultaneously. Keep this in mind we look at some optimizing techniques. Enhancing and Optimization The following discussion pertains to the efficiencies of all systems that use condensing boilers but can drastically increase the efficiency of higher temperature systems such as retrofits, pushing the efficiencies into the 96% to 97% area. As optimizing a condensing system consists of reducing flue gas temperatures primarily by reducing return water temperatures, we ll look at some options. Some of these will seem simple and obvious, but are certainly not discussed in the mainstream hydronic media. In general here are some techniques. Each one has the goal of reducing temperatures some where in the system: Add more heat emitters (lowers supply temperature needed) Preheating domestic water with the return Preheating HRV air Unit heaters in series Series plumbing - Baseboard feeding slab or baseboard feeding a cold area such as a garage Reduced mixed output temperatures result in reduced returns Reduced pumping speeds (increases T) Add an after-condenser to a single heat exchanger system Add another after-condenser for DHW well water Add a stack robber (condensing in the stack is as effective as condensing in a condenser if the heat is recovered). Open stacks (not walled in) or vented chases allow for heat recovery. Partial Reductions Note that it is not necessary to reduce the temperature of entire volume of return water to make a system effective. For example, if there is a total return of 4 gpm and you add a device to get a further 10 degree temperature drop for all the water, wouldn t it be better to drop 2 gpm by 20 degrees and put this reduced volume of lower temperature through the condenser? The following are a couple of examples of how the use diversion valves for split returns and series pumping. Page 3 of 5

56 Simple Two Temperature Systems When looking at a combined high and low temperature system such as a radiant floor and a DHW tank, the solution is simple, put the cool return in the condenser and the hot return in the primary. So let s look at a few other systems. Complex Systems One option if you have a combined slab and baseboard is to use a 3-way zone valve to divert the baseboard return to the condenser when the slab is not on. This will allow for more heat recovery and some condensing when only the baseboard is on. Remember that the condenser is a heat exchanger and increases efficiency even if it cannot reduce the temperature of the flue gas far enough to condense. Even when running hot a condensing boiler can have a burn efficiency of 90 to 91%. Another method would be to feed the slab from the return of the baseboard. A 3-way zone valve could be used here for flexibility. A 3-way diversion valve could also be incorporated to provide flexibility in volume control. A thermostatically controlled bypass valve could have application in the ability to modulate volumes based on temperature. Even though many baseboards or radiant wall panels are rated at 180 degrees, don t size for these temperatures. I know from my own experience that good baseboard works quite well at the 120 to 130 range. Further thoughts on baseboard: First of all, high temperature water may not be needed year round. See Brookhaven labs study on mixed circuits with set back control for baseboard. ( So a mixed circuit will work at least for a good percentage of the year, (the lower the supply, the easier it is to get a lower return with the same T. So next let s look at a unique application. DHW Systems In a system whose primary purpose is to produce DHW the runs most of the time when water is being used, and there is nearly continuous incoming fresh water. Consider re-plumbing the condenser from the boiler return water and routing fresh water from the source through the condenser. Well water in Alaska is just above freezing so the condensing effect would be in the 97% to 98% region. Notes on Efficiency Testing Electronic Testers a Grain of Salt These devices measure directly stack temperature along with O2 and CO. Based on the fuel type, it calculates CO2, excess air, and efficiency. The devices that do add the efficiency from condensing based on these and an algorithm that that uses stack temperature and fuel type. This is basically a guess because stack temperature does not create condensing, only lowering the return water in the condenser cause condensing. This results in lower stack temperatures. So this means that a 150 degree or for that matter, a 200 degree stack temperature could either be or not be condensing, depending on the return water temperature in the condenser. In fact, on the first stage of condensing, the overall flue gas temperatures do not have to be lowered at all. The Page 4 of 5

57 key here is that when the water part of the flue gas condenses, it does not change temperature while giving up the latent heat of vaporization. This happens when the water goes from the vapor state at 212 F to the liquid state at 212 F (no change in temperature). The tuning device has no way of measuring this. This is why the condensing boilers easily attain an efficiency of 93%+ in radiant applications. Comparisons Brookhaven National Labs have done testing comparing efficiencies of various boilers. In reading these, what has struck me is that they do not make apples to apples comparisons. For example, a conventional boiler must run at temperatures high enough to prevent condensing in either the boiler of the flue. So in order to level the playing field and make for uniform testing, the tests are geared to the lowest common denominator, which is that which a conventional boiler can operate. So the effect is that, optimization for a condensing boiler is not taken into consideration, simply because conventional boilers are not capable of the optimization under any circumstances. So even though enhancement controls for set-back, purging, cold starting, etc. apply to all boilers, the conventional boiler has reached maximum efficiency with these. However, the condensing system out of the box (even with controls) can still be improved on. This is because there is no physical reason why flue gas temperatures cannot be lowered more (its already condensing in the plastic stack). Consider that in the preceding example of preheating well water there is no reason stack temperatures cannot be lowered considerably below room temperatures. This is why the efficiency ratings for conventional boilers max out at about 87%. The rated efficiencies for the condensing boiler are just the starting point. The Bottom Line So design your system to take advantage of using low temperature water, and maximizing the T. Use the best heat emitters for the application you are working on. Use the best DHW indirect tanks designed for low boiler temperatures. Use the latest in technology in P or T Variable Frequency Drive (VFD) pumps. Page 5 of 5