| 摘要 |
A control and method for defrosting the outdoor heat exchanger of an air source heat pump. A defrost cycle is initiated when ice and frost have accumulated on the outdoor heat exchanger sufficiently such that, as a function of the indoor temperature of a comfort zone, the maximum permissible heat transfer degradation at which the efficiency and reliability of the temperature conditioning system are optimized, has occurred. Heat transfer degradation is determined from the outdoor ambient air temperature and the temperature of either the outdoor heat exchanger, or the compressor suction line. If the temperature of the outdoor heat exchanger or the suction line is less than a predetermined value, a deferred defrost cycle is initiated wherein the defrost cycle starts after a fixed time interval has elapsed. The defrost cycle is terminated when the relative temperatures of the outdoor heat exchanger and the outdoor ambient air indicate that sufficient frost is melted from the heat exchanger to insure adequate time between successive defrost cycles for optimizing the efficiency and reliability of the system, or after a predetermined time interval has elapsed, whichever condition occurs first.
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