08 January 2007

Air-to-Air Heat Pumps Evaluated for Nordic Circumstances

Twelve variable-speed capacity controlled air-to-air heat pumps have been evaluated by laboratory measurements
and the results have been compared to similar investigations made in 2001 (variable-speed capacity control)
and 1991 (single-speed compressors). The heat pumps were evaluated in terms of effi ciency, performance
of defrost system and ability to operate in a cold climate. The results show that heat pumps have become more
effi cient since 1991 and 2001. On average, the coeffi cient of performance (COP) has increased by 7-24 % since
1991. The defrost systems have also improved, although there are still systems that in practice operate under
simple time control, and thus perform unnecessarily many defrost cycles, which reduces performance and probably
also equipment life.