With sponsorship from the US Department of Energy, a research project has designed, fabricated, and tested improvements to an air conditioner’s outdoor unit fan system. The primary objective was to improve condenser fan performance while reducing motor power. We also examined potential changes to the condenser’s exhaust configuration to enhance air-moving efficiency performance. A secondary objective was to provide sound reductions, as less noisy AC equipment is important to consumers.

Within conducted tests, an improved high-efficiency fan design and advanced exhaust diffuser section reduced fan motor power requirements by approximately 49 W (26%) while providing superior airflow. When mated with a brushless DC motor, the same configuration can reduce fan power use by just over 100 W (55%). The overall increase to total system efficiency (EER and COP) is approximately 2% to 4% depending on configuration. The reduced fan unit power could be very desirable for utilities concerned with peak demand, since the change provides reliable load reductions on peak.

The changes in exhaust configuration are also important in that they allow for slower fan speeds to obtain equivalent flow. When coupled with a developed vortex shedding control strip and an asymmetrical fan design, the exhaust showed reductions to fan sound levels of 1 to 2 dB according to ARI Standard 270-1995.