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Residential Space and Water Heating: The Combined Approach - Schoenbauer
This document discusses research into combining residential space and water heating using a distributed integrated air (DIA) system. It describes how tighter homes require sealed combustion, which has led to installing less efficient water heaters for safety. The research aims to design DIA systems in a lab to provide optimal performance and installation guidelines. Lab testing analyzed idle losses, efficiencies, and full system tests of different DIA designs. Field studies of 300 homes are monitoring installed costs, savings, and system efficiencies to better understand the real-world potential of the DIA approach. Preliminary results suggest gas savings of 20-25% and electricity reductions of 40-75% compared to typical existing equipment.
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Residential Space and Water Heating: The Combined Approach - Schoenbauer
- 1. Residential Space andWater Heating: The Combined Approach Ben Schoenbauer, Research Engineer, Center for Energy and Environment May 22, 2012
- 2. How this projectcame 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 high efficiency water heaters − Forced to use safety budget to install 60% direct vent tanks with very little energy savings − SRC replaces furnaces in 47% of the homes they weatherize and water heaters in 48% − SRC got a Sustainable Energy Resources for Consumers (SERC) grant to look at using a DIA
- 3. Storage water heaterbased system DHW Loads Hot Space Heating Air Cold In from Mains Supply to AH Storage Water Hydronic Heater Air Return from AH Handler Page 3 Open Loop
- 4. Tankless water heaterbased system Hot Space DHW Loads Heating Air Cold In from Mains Supply to AH Hydronic TWH Air Return from AH Handler Page 4 Electric Gas Electric
- 5. Combi boiler basedsystem DHW Loads Hot Space Heating Air Cold In from Mains DHW Loop HE Supply to AH Space loop Hydronic Air Handler Return from AH Combi Boiler Primary Loop Secondary Loop Page 5 Closed Loop
- 6. Installation and Sizing PROBLEM + Some contractor’s had little experience + System schematics often developed on site + Little or no sizing information provided + System components came from several manufacturers + Manufacturer’s settings may not lead to best performance + Decided to design and optimize systems in a laboratory + Could then provide contractors with more detail installation guidelines Page 6
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- 8. Lab work + Idle losses + Steady state efficiency + Air handler capacity testing + Full system tests Page 8
- 9. + Lab Testing Idle Losses Setpoint = 140 F $1/therm $0.12/kWh Page 9
- 10. Boiler 1 –Combi boiler with 12 gal DHW tank Page 10
- 11. + Lab Tests – Idle Testing TANK 2 Page 11
- 12. Steady-State Space HeatingEfficiency Tset=130F and Flow rate=4.0GPM Page 12 Going from 90% to 80% increase heating bills about $150/year in MN
- 13. Air Handler PerformanceMapping + Minimum supply air temperature (110 F) for comfort dictates minimum flow rate + Maximum return water temperature (105 F) dictates maximum flow rate + Coil capacity is bounded by these flow rates Page 13
- 14. Air Handler PerformanceMapping Page 14 At CFM=1100, Supply Water =140F, Return Air = 70F
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- 16. Air Handler PerformanceMapping 52,500 – 57,000 kBtu/hr 45,500 – 54,000 kBtu/hr Page 16
- 17. Field Implementation andMonitoring + 300 installs in Minnesota before December 2012 + Utility bill analysis on all 300 sites + Detailed pre/post monitoring on 20 sites Page 17
- 18. Field Study: ExpectedResults + Better understanding of installed costs for different systems after contractors have become familiar + System design specifications and quality control requirements + Installed efficiencies of DIA systems and savings potential Page 18
- 19. Existing Equipment Hot Space Runtime Heating Air Cold In from Mains Conditioned DHW Loads Space Air Temp Ambient T ND Tank Water Single Heater Stage Furnace Outdoor Gas Electric Gas Page 19
- 20. DIA Installation Hot Space Water Temp Heating Air Cold In from Mains Water Flow DHW Loads Air Temp Conditioned Space Air Flow Ambient T Consumption Supply to AH Water Hydronic Heater Air Return from AH Handler Outdoor Electric Gas Electric Page 20
- 21. COMBI EXISTING Page 21
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- 25. Minneapolis Ave OutdoorTemp when Space Heating = 33 °F Minneapolis Design Outdoor Temp for Space Heating = 18 °F Page 25
- 26. Represents about a250 therm/yr savings or about 25% of the gas heating (space + dhw) bill and 75% electricity use for space + dhw use DHW about 1% of total output Page 26
- 27. Represents about a120 therm/yr savings or about 20% of the gas heating (space + dhw) bill and 40% electricity use for space + dhw use Very low hot water use only 5 gpd on ave. Page 27
- 28. Represents about a20 therm/yr increase or about 3% of the gas heating (space + dhw) bill PRELIMINARY: Comparison electricity use reduction for space + and 20% dhw use to a 93% AFUE Furnace DHW about 1% of total output Page 28
- 29. 250 kBtu/day ~10kbtu/hr space and 20 gpd at 70DT Page 29 700 kBtu/day ~ 28kbtu/hr space and 50 gpd at 70DT
- 30. Days with NoSpace Heating 0 20 40 60 80 100 120 140 160 Page 30
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- 32. Questions? Ben Schoenbauer bschoenbauer@mncee.org Page 32