Abstract: An electrical interlock ties a heat recover ventilator to circulation air blower operation of an associated forced-air furnace or air conditioning system. This ensure that the blower circulates supply and return air within the building or dwelling. An interlock relay has its coil energized by the heat recovery ventilator, and a normally open contact tied to the control of a blower of the forced-air system. The furnace or air conditioner and the ventilator are operated by separate controls located within the building's comfort space. When the ventilator is operated, the circulation blower runs continuously, but thermostat actuate of the furnace or air conditioner above will not operate the ventilator.

Abstract: In an outdoor unit of a heat pump having a variable speed compressor, the fan speed is controlled in response to both the speed of the compressor and the temperature of the outdoor refrigerant such that the operating efficiency of the fan and its driving motor can be optimized over a full range of compressor operating speeds.