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Title: Retrofitting Forced Air Combi Systems: A Cold Climate Field Assessment

Abstract

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 efficiencymore » appliances. Careful consideration was paid to proper system sizing and minimizing the water temperature returning from the air handling unit to facilitate condensing operation.« less

Authors:
 [1];  [1];  [1];  [1]
  1. Univ. of Minnesota, St. Paul, MN (United States). NorthernSTAR Building America Partnership
Publication Date:
Research Org.:
National Renewable Energy Lab. (NREL), Golden, CO (United States)
Sponsoring Org.:
USDOE Office of Energy Efficiency and Renewable Energy (EERE), Building Technologies Office (EE-5B)
OSTI Identifier:
1369136
Report Number(s):
NREL/SR-5500-61313; DOE/GO-102017-4378
DOE Contract Number:  
AC36-08GO28308
Resource Type:
Technical Report
Country of Publication:
United States
Language:
English
Subject:
32 ENERGY CONSERVATION, CONSUMPTION, AND UTILIZATION; 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

Citation Formats

Schoenbauer, Ben, Bohac, Dave, McAlpine, Jake, and Hewett, Martha. Retrofitting Forced Air Combi Systems: A Cold Climate Field Assessment. United States: N. p., 2017. Web. doi:10.2172/1369136.
Schoenbauer, Ben, Bohac, Dave, McAlpine, Jake, & Hewett, Martha. Retrofitting Forced Air Combi Systems: A Cold Climate Field Assessment. United States. doi:10.2172/1369136.
Schoenbauer, Ben, Bohac, Dave, McAlpine, Jake, and Hewett, Martha. Fri . "Retrofitting Forced Air Combi Systems: A Cold Climate Field Assessment". United States. doi:10.2172/1369136. https://www.osti.gov/servlets/purl/1369136.
@article{osti_1369136,
title = {Retrofitting Forced Air Combi Systems: A Cold Climate Field Assessment},
author = {Schoenbauer, Ben and Bohac, Dave and McAlpine, Jake and Hewett, Martha},
abstractNote = {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.},
doi = {10.2172/1369136},
journal = {},
number = ,
volume = ,
place = {United States},
year = {Fri Jun 23 00:00:00 EDT 2017},
month = {Fri Jun 23 00:00:00 EDT 2017}
}

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