Retrofitting Forced Air Combi Systems: A Cold Climate Field Assessment
- Univ. of Minnesota, St. Paul, MN (United States). NorthernSTAR Building America Partnership
This project analyzed combined condensing water heaters or boilers and hydronic air coils to provide high efficiency domestic hot water (DHW) and forced air space heating. Called 'combi' systems, they provided similar space and water heating performance less expensively than installing two condensing appliances. The system's installed costs were cheaper than installing a condensing furnace and either a condensing tankless or condensing storage water heater. However, combi costs must mature and be reduced before they are competitive with a condensing furnace and power vented water heater (energy factor of 0.60). Better insulation and tighter envelopes are reducing space heating loads for new and existing homes. For many homes, decreased space heating loads make it possible for both space and domestic water heating loads to be provided with a single heating plant. These systems can also eliminate safety issues associated with natural draft appliances through the use of one common sealed combustion vent. The combined space and water heating approach was not a new idea. Past systems have used non-condensing heating plants, which limited their usefulness in climates with high heating loads. Previous laboratory work (Schoenbauer et al. 2012a) showed that proper installation was necessary to achieve condensing with high efficiency appliances. Careful consideration was paid to proper system sizing and minimizing the water temperature returning from the air handling unit to facilitate condensing operation.
- Research Organization:
- National Renewable Energy Lab. (NREL), Golden, CO (United States)
- Sponsoring Organization:
- USDOE Office of Energy Efficiency and Renewable Energy (EERE), Energy Efficiency Office. Building Technologies Office
- DOE Contract Number:
- AC36-08GO28308
- OSTI ID:
- 1369136
- Report Number(s):
- NREL/SR-5500-61313; DOE/GO-102017-4378
- Country of Publication:
- United States
- Language:
- English
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Related Subjects
residential
residential buildings
NorthernSTAR
Building America
combi heating systems
forced air combi systems
hydronic air handlers
boiler based combi systems
tankless water heater based combi systems
storage water heater based combi systems
DHW performance
combi system summer efficiency
dual integrated appliances
direct vent burner