Retrofitting Combined Space and Water Heating Systems: Laboratory Tests

Stacey Rothgeb, Stacey Rothgeb (NREL Technical Monitor)

Research output: NRELSubcontract Report


Better insulated and tighter homes can often use a single heating plant for both space and domestic water heating. These systems, called dual integrated appliances (DIA) or combination systems, can operate at high efficiency and eliminate combustion safety issues associated by using a condensing, sealed combustion heating plant. Funds were received to install 400 DIAs in Minnesota low-incomehomes. The NorthernSTAR DIA laboratory was created to identify proper system components, designs, operating parameters, and installation procedures to assure high efficiency of field installed systems. Tests verified that heating loads up to 57,000 Btu/hr can be achieved with acceptable return water temperatures and supply air temperatures.
Original languageAmerican English
Number of pages51
StatePublished - 2012

Bibliographical note

Work performed by NorthernSTAR Building America Partnership, St. Paul, Minnesota

NREL Publication Number

  • NREL/SR-5500-55482

Other Report Number

  • DOE/GO-102012-3694


  • boilers
  • Building America
  • combination system
  • condensing
  • integrated systems
  • laboratory tests
  • residential
  • residential buildings
  • sealed combustion
  • water heaters


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