Patent ID: 6141978
Filing Date: 2000-11-07
Classification: F25B,F25D,Y02B,Y10S

Abstract:
In an apparatus for use in a heat pump system of the type including a compressor, an outdoor unit having an outdoor coil and an outdoor fan, an indoor unit having an indoor coil and an indoor fan, and a liquid line and a vapor line for connecting said indoor and outdoor coils and said compressor in a closed fluidic path, said heat pump system being adapted to operate in any of a cooling mode, a heating mode and a defrosting mode, in combination:(a.) a defrost condition detecting device, connected to the outdoor coil, for detecting the occurrence of a frost forming condition at the outdoor coil;(b.) a control circuit for controlling the operation of said outdoor unit, said control circuit including:(i) pressure limiting circuitry, responsive to one of the pressure and temperature of the refrigerant fluid in said vapor line, for limiting the pressure within said vapor line to a predetermined safe pressure; and(ii) defrost control circuitry, responsive to said defrost condition detecting device, for causing the heat pump system to initiate a defrost cycle when said frost forming condition has existed for more than a predetermined time; and(c.) a defrost inhibiting device for preventing said defrost control circuitry from initiating a defrost cycle when the defrost condition detecting device indicates the occurrence of a frost forming condition merely because of the pressure limiting activity of said pressure limiting circuitry.