Demand defrost control method and apparatus.

摘要

A demand defrost controller (30) for a heat pump (10). The controller (30) compares the temperature of an outdoor heat exchange coil (14) with an enable temperature. A timer is activated when the coil temperature is less than the enable temperature. When the timer senses the compressor (20) has a run for a predetermined time the controller (30) checks outdoor and coil temperatures to determine if a defrost cycle of the heat pump (10) should be conducted. A defrost cycle is achieved by reversing refrigerant flow in the heat pump system for a predetermined period or until the outdoor heat exchange coil (14) has been heated to a termination temperature.