18 May 2017
The recent advancement of variable capacity technologies has led to the introduction of cold climate air source heat pumps (CCASHP) capable of efficiently meeting space heating loads at low ambient temperatures. Widespread adoption in Canada is still hindered however due to a lack of detailed and reliable performance data to accurately assess the benefits of CCASHPs. This paper presents the results and observations of the detailed performance tests conducted on centrally ducted and ductless CCASHP systems with the goal of addressing barriers and identifying potential improvements.
Performance tests revealed that while the systems were able to efficiently heat at low ambient temperatures, the manufacturer performance curves were difficult to interpret and not entirely suitable to assess the benefit of these system types. The efficient modulation to meet varying space heating loads does result in improved seasonal efficiencies over single stage systems. Further energy savings can be achieved by improving or modifying the defrost control strategies. In ducted systems, avoiding the use of the auxiliary heating system during defrost can result in 40% energy savings per defrost cycle. In ductless systems, the system operates at full power immediately following the defrost cycle, which can be of concern for utility companies as increased adoption could result in more strain on the local grid.