P2. Assment And Field Testing Of Ventilation Recovery Heat Pumps > Outcomes

• The HPHR system did not provide positive cost savings for most building type/climate combinations investigated. The heat pump heat recovery (HPHR) system functioned properly during the field and laboratory testing. However, heating requirements are relatively low for California climates and therefore overall savings are dictated by cooling season performance. The cooling COP of the HPHR system must be high enough to overcome:
  • additional cycling losses from the primary air conditioner compressor,
    
  • additional fan power associated with the exhaust and/or ventilation fan,
    
  • additional cooling requirements due to a higher latent removal and
    
  • a lower operating COP for the primary air conditioner compressor because of a colder mixed air temperature.

• The HPHR system is an alternative to an economizer and so economizer savings are also lost when using this system. There are not sufficient hours of ambient temperatures above the breakeven points to yield overall positive savings with the HPHR system compared to a base case system with an economizer for the prototypical buildings in California climates.

Based on the technical outcome of this project, it is unlikely that heat pump heat recovery systems will be specified for California commercial buildings.