Full Description

Space heating and cooling use represents about 40%-50% of total annual energy and is usually the highest end use in homes. Therefore, matters impacting space conditioning may have significant impact on home energy use. Correct refrigerant charge, preventative maintenance, and air distribution duct location, design, airtightness and insulation integrity can have significant impacts upon energy use. Inadequate duct design and installation can result in elevated total external static pressure, which can have significant impacts on performance. This research project was designed to investigate the cooling performance impacts of increased static pressure, which often results from poor design and installation practices. Two identical university lab homes sited next to each other were used with a metal duct system in one home and a flex duct system in the other. Each duct system had the same general layout within a vented attic. Space conditioning was provided by identical two-stage split-DX heat pumps having the same model numbers. The air handlers used electronically commutated motors that delivered design airflow across a wide range of static pressure. Energy use, temperatures and relative humidity and refrigerant line temperatures and pressure were monitored. An initial test 1 compared quality duct design, sizing, and installation meeting industry standards for each duct type. The metal duct system at 0.34 in WC (85 Pa) was used as a baseline of comparison to the flex duct at 0.44 in WC (110 Pa). Two additional tests were run with the flex system at higher static pressures. Test 2 operated the flex system at 1.00 in WC (249 Pa), which represented high compression and some poor radius turns. Test 3 operated the flex system at 0.82 in WC (204 Pa), which represented more typical installation practice. There were significant central fan energy impacts. Observed impacts of duct static pressure upon the ECM fan energy found flex duct energy increases of 33%, 148%, and 72% for tests 1, 2, and 3 respectively. This paper further discusses a comparison of the daily cooling energy impacts by condensing unit and air handler fan for typical summer days as well as an annual energy impact between the metal duct and 0.82 in WC (204 Pa) flex duct for three different locations in climate zone 1 and 2. Implications of over-compression of metal duct exterior FSK insulation wrap upon energy was also discussed.

Product Details

Published: 2022 Number of Pages: 9 Units of Measure: Dual File Size: 1 file , 1.7 MB Product Code(s): D-TO-22-C063 Note: This product is unavailable in Russia, Belarus