Experimental study on low temperature start-up performance of air-source cold and hot water heat pump systems

Studies the start-up performance of an air-source cold and hot water heat pump system using variable frequency compressor at low ambient temperature. The results show that there is a vacuum phenomenon during the restarting of the heat pump unit when the heat pump unit stops at low ambient temperature for a long time, which results in the start-up failure of the system because of low voltage protection, and the heat pump unit can be successfully restarted at low ambient temperature by controlling the initial frequency of the compressor and the initial opening of the throttle element.