Performance and Optimization ofResidential Condensing CombinationSpace and Water Heating SystemsBen Schoenbauer, Center fo...
Sponsors and Partners NorthernSTAR - A DOE Building America Research Team Sustainable Energy Resources for Consumers Gra...
Overview Background: Project and Equipment System Design Field Results: Efficiency, Savings, Comfort Cost What’s next
How this project came about− Weatherization is able to seal homes tighter and tighter− Leads to combustion safety issues− ...
What is a Dual Integrated Appliance?A. A mechanical system that uses one heating plant (natural gasburner) to provide both...
Page 10PROBLEM+ Some contractor’s had little experience+ System schematics often developed on site+ Little or no sizing in...
Page 11 Full report at:http://apps1.eere.energy.gov/buildings/publications/pdfs/building_america/labtests_combi_spacewh.pdf
Page 12Steady-state heating plant efficiency
Page 13Air handler performance+ Hydronic coil transfers heatfrom water to air+ Goals:+ Return water <105 °F+ Delivered air...
Page 14Tset =140 °F CFM =1500GPM = 5100°F60,000 Btu/hr120°FPoor install(for a 40,000 Btu/hr design load)
Page 15Tset =140 °F CFM =900GPM = 2.5112°F45,000 Btu/hr105°FBetter install(for a 40,000 Btu/hr design load)
Page 16Tset =125 °F CFM =900GPM = 2.5106°F43,000 Btu/hr90°FBest install(for a 40,000 Btu/hr design load)
Page 17Tset =120 -140 °FCFM =800 -1000GPM =2 - 3100 - 115°F20 – 50 kBtu/hr80 - 105°FIdeal future install(for a 40,000 Btu/...
Field Implementation and Monitoringo 250 installs in Minnesota• Lessons learned from implementation• Detailed pre/post mon...
Page 19Minneapolis+ Heating Degree Days: 7565+ Heating Design Temp: -13.4 FProject Averages+ Space Heating Design Conditio...
Page 20VentingInstallationB-VentDirect
Page 21+ Condensation ManagementInstallation:
Page 22Mixing ValveInstallation:
Page 23+ Locations and equipment size may change+ Tankless water heaters and combi boilers areoften wall mounted+ Location...
Page 24Increasing the water heater set pointInstallation: Equipment Set Up
Page 25Adjusting the water flow rate through the air handlerInstallation: Equipment Set Up
Page 26Adjusting the air flow rate through the air handlerInstallation: Equipment Set UpMost Common Methods:• Dip switches...
Field Monitoring Insturmentation
Page 28Existing EquipmentDHW LoadsCold In from MainsHot SpaceHeating AirRuntimeAir TempAmbient TGasND TankWaterHeaterElect...
Page 29DIA InstallationDHW LoadsCold In from MainsSupply to AHReturn from AHHydronicAirHandlerHot SpaceHeating AirWater Te...
Page 30EXISTINGCOMBI
Page 31
Efficiency
Page 33Installed Monthly Efficiencies
Page 34+ Lab TestingWhy the low efficiencies in the summer?Setpoint = 140 F$1/therm$0.12/kWhr
Page 35+ Lab Tests – Idle TestingTANK 2
Page 36+ Lab Tests – Idle TestingTWH 2 – Storage Tankless Hybrid
Page 37TWH 1
Page 38• DHW accounted for between 2% and 34% ofthe total heating load. (13% on average)Variance in Daily Water Usage
Page 39Annual Efficiencies25,000 btu/hr design heating loadand 40 gpd of hot waterDashed lines represent possibleinstalled...
Savings Potential
Page 411028 – possible 70% eff furn1031 – Condensing Furn1037 – Combi boiler annual eff 81%
Page 42Power Consumption+ During Space Heating+ Existing Systems: 550 W+ Combi System: 475 W+ During Continuous Fan Operat...
Occupant Comfort
Page 44+ Non-condensing furnaces: 130 - 140 ° F+ Condensing furnaces: 115 – 130 ° F+ Space heating heat pumps: 77 – 115 ° ...
Page 45Delivered Water Temperature – Storage Water Heater
Page 46Delivered Water Temperature – Tankless Water Heater
Page 47Delivered Water Temperature – Hybrid Water Heater
Costs, Savings, and Payback
Page 49Cost Comparisons
Page 50Note:• Typical loads were 25,000 Btu/hr design day space heating loads and 40 GPD hot water.• Base Case: $725 per y...
Page 51Savings and PaybacksNote: Combi systems were cheaper to install thata condensing water heater and condensingfurnace
Page 52+ System Controls: Work to be completed in 2013+ What cycle lengths are necessary to prevent short cycling foreffic...
Page 53Questions?Ben Schoenbauerbschoenbauer@mncee.orgMore information available at:www.mncee.org/dia
Performance and Optimization of Residential Condensing Combi Systems
Performance and Optimization of Residential Condensing Combi Systems
Performance and Optimization of Residential Condensing Combi Systems
Performance and Optimization of Residential Condensing Combi Systems
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Performance and Optimization of Residential Condensing Combi Systems

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Homeowners with natural gas water heaters have difficulty justifying the expense of a more efficient condensing heater. Combination space and domestic hot water systems bundle together the two loads, which saves energy and makes them more cost-effective. These systems also help eliminate combustion safety concerns.

Historically, mechanical contractors have custom engineered and pieced together combi systems in the field, paying little attention to efficiency and optimization. But condensing heating plants will only reach their energy saving potential when all components are designed and installed correctly.

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Performance and Optimization of Residential Condensing Combi Systems

  1. 1. Performance and Optimization ofResidential Condensing CombinationSpace and Water Heating SystemsBen Schoenbauer, Center for Energy and EnvironmentApril 23, 2013
  2. 2. Sponsors and Partners NorthernSTAR - A DOE Building America Research Team Sustainable Energy Resources for Consumers Grants Center for Energy and Environment Sustainable Resources Center University of Minnesota The Energy Conservatory
  3. 3. Overview Background: Project and Equipment System Design Field Results: Efficiency, Savings, Comfort Cost What’s next
  4. 4. How this project came about− Weatherization is able to seal homes tighter and tighter− Leads to combustion safety issues− Requires sealed combustion− Requirements on Savings vs installed cost rule out highefficiency water heaters− Forced to use safety budget to install 60% direct vent tanks withvery little energy savings− SRC got a SERC grant to look at using a DIA
  5. 5. What is a Dual Integrated Appliance?A. A mechanical system that uses one heating plant (natural gasburner) to provide both space heating and hot waterB. Space heating side can be either hydronic or forced airC. Systems can use a closed or open heating loopThis project will look at natural gas forced air DIA systems. Boilerbased systems will be closed loop and water heater systemshave an open loop.
  6. 6. Page 10PROBLEM+ Some contractor’s had little experience+ System schematics often developed on site+ Little or no sizing information provided+ System components came from severalmanufacturers+ Manufacturer’s settings typically do not lead to bestperformance+ Decided to design and optimize systems in alaboratory+ Could then provide contractors with more detailinstallation guidelinesInstallation and Sizing
  7. 7. Page 11 Full report at:http://apps1.eere.energy.gov/buildings/publications/pdfs/building_america/labtests_combi_spacewh.pdf
  8. 8. Page 12Steady-state heating plant efficiency
  9. 9. Page 13Air handler performance+ Hydronic coil transfers heatfrom water to air+ Goals:+ Return water <105 °F+ Delivered air >110 °F+ Goals must be balanced withcapacity needs+ Installation parameter chartswere developed for each airhandler
  10. 10. Page 14Tset =140 °F CFM =1500GPM = 5100°F60,000 Btu/hr120°FPoor install(for a 40,000 Btu/hr design load)
  11. 11. Page 15Tset =140 °F CFM =900GPM = 2.5112°F45,000 Btu/hr105°FBetter install(for a 40,000 Btu/hr design load)
  12. 12. Page 16Tset =125 °F CFM =900GPM = 2.5106°F43,000 Btu/hr90°FBest install(for a 40,000 Btu/hr design load)
  13. 13. Page 17Tset =120 -140 °FCFM =800 -1000GPM =2 - 3100 - 115°F20 – 50 kBtu/hr80 - 105°FIdeal future install(for a 40,000 Btu/hr design load)
  14. 14. Field Implementation and Monitoringo 250 installs in Minnesota• Lessons learned from implementation• Detailed pre/post monitoring on 20 sites
  15. 15. Page 19Minneapolis+ Heating Degree Days: 7565+ Heating Design Temp: -13.4 FProject Averages+ Space Heating Design Condition: 25,000 btu/hr+ DHW Daily Usage: 41 gallons/day (830 Btu/hr)+ Combined Gas Consumption (AFUE~80 and EF~58):900 therms/yearTypical Installation+ Unfinished basements or mechanical rooms in finished basementsHouse Characteristics
  16. 16. Page 20VentingInstallationB-VentDirect
  17. 17. Page 21+ Condensation ManagementInstallation:
  18. 18. Page 22Mixing ValveInstallation:
  19. 19. Page 23+ Locations and equipment size may change+ Tankless water heaters and combi boilers areoften wall mounted+ Location of the large gas line may change+ Additional power linesInstallation:
  20. 20. Page 24Increasing the water heater set pointInstallation: Equipment Set Up
  21. 21. Page 25Adjusting the water flow rate through the air handlerInstallation: Equipment Set Up
  22. 22. Page 26Adjusting the air flow rate through the air handlerInstallation: Equipment Set UpMost Common Methods:• Dip switches• Switching wires for variousspeeds
  23. 23. Field Monitoring Insturmentation
  24. 24. Page 28Existing EquipmentDHW LoadsCold In from MainsHot SpaceHeating AirRuntimeAir TempAmbient TGasND TankWaterHeaterElectric GasSingleStageFurnaceConditionedSpace
  25. 25. Page 29DIA InstallationDHW LoadsCold In from MainsSupply to AHReturn from AHHydronicAirHandlerHot SpaceHeating AirWater TempWater FlowConsumptionAir TempAir FlowElectricAmbient TElectric GasWaterHeaterConditionedSpace
  26. 26. Page 30EXISTINGCOMBI
  27. 27. Page 31
  28. 28. Efficiency
  29. 29. Page 33Installed Monthly Efficiencies
  30. 30. Page 34+ Lab TestingWhy the low efficiencies in the summer?Setpoint = 140 F$1/therm$0.12/kWhr
  31. 31. Page 35+ Lab Tests – Idle TestingTANK 2
  32. 32. Page 36+ Lab Tests – Idle TestingTWH 2 – Storage Tankless Hybrid
  33. 33. Page 37TWH 1
  34. 34. Page 38• DHW accounted for between 2% and 34% ofthe total heating load. (13% on average)Variance in Daily Water Usage
  35. 35. Page 39Annual Efficiencies25,000 btu/hr design heating loadand 40 gpd of hot waterDashed lines represent possibleinstalled efficiency
  36. 36. Savings Potential
  37. 37. Page 411028 – possible 70% eff furn1031 – Condensing Furn1037 – Combi boiler annual eff 81%
  38. 38. Page 42Power Consumption+ During Space Heating+ Existing Systems: 550 W+ Combi System: 475 W+ During Continuous Fan Operation:+ Existing Systems: 425 W+ Combi Systems: 50 W
  39. 39. Occupant Comfort
  40. 40. Page 44+ Non-condensing furnaces: 130 - 140 ° F+ Condensing furnaces: 115 – 130 ° F+ Space heating heat pumps: 77 – 115 ° F+ Combis this project :110 – 115 ° F+ Could improve efficiency 3-5% allowing 105 °F air temps.Supply Air Summary
  41. 41. Page 45Delivered Water Temperature – Storage Water Heater
  42. 42. Page 46Delivered Water Temperature – Tankless Water Heater
  43. 43. Page 47Delivered Water Temperature – Hybrid Water Heater
  44. 44. Costs, Savings, and Payback
  45. 45. Page 49Cost Comparisons
  46. 46. Page 50Note:• Typical loads were 25,000 Btu/hr design day space heating loads and 40 GPD hot water.• Base Case: $725 per year gas bill (915 therms)Savings and paybacks
  47. 47. Page 51Savings and PaybacksNote: Combi systems were cheaper to install thata condensing water heater and condensingfurnace
  48. 48. Page 52+ System Controls: Work to be completed in 2013+ What cycle lengths are necessary to prevent short cycling forefficiency? Room temperature?+ How will fan and pump modulation improve efficiency andcomfort?+ How much can temperature set backs (outdoor resets) improveperformance?+ How will system performance change if we remove the airtemperature restrictions?+ Other Equipment Needs+ Improvements to air and water temperature delays+ DHW priorities impact on comfort+ Other Program Needs+ Method for verifying savings for rebate programs+ Consistent rating system for combi systems+ Impacts on costWhat else do we need to know?
  49. 49. Page 53Questions?Ben Schoenbauerbschoenbauer@mncee.orgMore information available at:www.mncee.org/dia
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