skip to main content

Title: Combined Space and Water Heating: Next Steps to Improved Performance

A combined space- and water-heating (combi) system uses a high-efficiency direct-vent burner that eliminates safety issues associated with natural draft appliances. Past research with these systems shows that using condensing water heaters or boilers with hydronic air handling units can provide both space and water heating with efficiencies of 90% or higher. Improved controls have the potential to reduce complexity and improve upon the measured performance. This project demonstrates that controls can significantly benefit these first-generation systems. Laboratory tests and daily load/performance models showed that the set point temperature reset control produced a 2.1%-4.3% (20-40 therms/year) savings for storage and hybrid water heater combi systems operated in moderate-load homes.
 [1] ;  [1] ;  [1]
  1. NorthernSTAR Building America Partnership, Minneapolis, MN (United States)
Publication Date:
OSTI Identifier:
Report Number(s):
NREL/SR-5500-63459; DOE/GO-102016-4600
DOE Contract Number:
Resource Type:
Technical Report
Research Org:
NorthernSTAR Building America Partnership, Minneapolis, MN (United States)
Sponsoring Org:
USDOE Office of Energy Efficiency and Renewable Energy (EERE), Building Technologies Office (EE-5B)
Country of Publication:
United States
32 ENERGY CONSERVATION, CONSUMPTION, AND UTILIZATION; residential; Residential Buildings; NorthernSTAR; Building America; HVAC; space heating; water heating; condensing; low load homes