In the 1970s a new HVAC system was designed and developed in Japan-the ductless heat pump (DHP). Today, almost all residential HVAC systems in Asia and the majority of systems in Europe are ductless, while in the U.S. DHPs account for only one percent the residential HVAC market. Recently, inverter driven DHPs have been recognized as an effective way to reduce heating consumption in homes with electric resistance heat and DHP initiatives have started in the Pacific Northwest and Connecticut. Inverter technology allows DHPs to operate at continuous variable partial load conditions in order to maximize their efficiency. Despite their longevity in the worldwide market, there is a lack of real world performance data for DHPs, especially relative to their ability to work effectively and efficiently at cold ambient temperatures. While the programs in Connecticut and the Pacific Northwest have shown promising energy savings, there have been few studies published to date that involve direct measure of the operating efficiency of DHPs across a wide range of operating conditions and ambient temperatures. This paper presents the results of two winters of detailed data collection on a DHP installed in central Connecticut. The DHP was installed in a 550 square foot apartment heated with electric resistance baseboard. Throughout the two winters the apartment alternated between electric resistance baseboard, the DHP, and a combination of both for heating under ambient conditions ranging from-lOT to 75 T. The results will help to dispel the common myth that heat pumps are ineffective in cold climates. Additionally, the results of this study suggest DHPs may be good substitute for ground source heat pumps as they operate at similar efficiencies for much lower installed costs. This report evaluates DHPs on both a performance and economic level to show that DHPs have the capability to play a much larger role in the U.S. HVAC market.
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