Air-to-water heat pumps (AWHPs) are a flexible type of air source heat pump (ASHP) system with several advantages over forced-air ASHP systems. For example, distribution is more efficient when moving water instead of air and the very low distribution temperatures of modern hydronic systems, particularly radiant floors, may further improve the heat pump cycle’s efficiency. The applications of AWHPs are also diverse. Water distribution systems can incorporate a variety of heating and cooling equipment simultaneously, including radiant emitters, central hydronic air handlers, mini-split-style individual room cassettes, domestic hot water systems, and thermal storage systems. However, with this flexibility comes complexity, which may be compounded in cold climate applications that already require more advanced compressors and controls to achieve efficient operation. In this case study, three AWHP systems of varied complexity were installed in single-family homes with radiant floor heating located in the state of Minnesota (U.S.), climate zone 6. AWHP systems are new to this market and the lack of published field performance data remains a technical gap for the technology’s acceptance. Through continuous power, flow, and temperature monitoring, we assessed each system’s operational behavior and calculated system performance efficiencies. Our examination of the select systems’ operations highlighted the challenge in optimizing the control of AWHP systems. While coefficient of performances (COPs) above 3 were observed, unaligned control logic between the outdoor compressor unit, indoor distribution unit, and thermostat can quickly reduce the COP by 50% or more, even during mild temperatures. Suppressed seasonal efficiency does not necessarily correlate to less occupant comfort, but suboptimal control settings, equipment failures, or imperfect installations are sources of comfort complaints. Delivering reliable comfort and efficiency gains will be vital to leverage the remarkable flexibility AWHP systems may offer.
| File Size : | 1
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, 4.3 MB |
| Note : | This product is unavailable in Russia, Belarus |
| Number of Pages : | 9 |
| Product Code(s) : | D-CCC23-13 |
| Published : | 2023 |
| Units of Measure : | Dual |
