30 May 2005


For house heating applications heat-pumps have a lower primary energy demand than many other
heating technologies like oil boilers. In several European countries the heat-pumps have a good market
share in new buildings. But the big potential of the retrofit market in Europe was not accessible due to
some restrictions: The older heating systems require an outlet temperature of 65°C to 70°C. The heat
source for a retrofit HP should be ambient air. So the requirement is a high COP and a temperature lift
from –15°C ambient air to 65°C outlet temperature. And the HP should be interesting from an economical
point of view which excludes multistage HP and other solutions.
Together with Copeland the German heating system manufacturer Viessmann developed a HP with
an Economiser Cycle and hot gas injection in the compressor. The function of the cycle and measurement
results from field tests and laboratory will be presented. The results show an interesting behaviour of the
cycle for a COP and temperature optimisation.