Refrigeration – Automatic control – Refrigeration producer
Patent
1989-02-06
1990-08-21
Tanner, Harry B.
Refrigeration
Automatic control
Refrigeration producer
62155, 62278, F25D 2106
Patent
active
049495518
ABSTRACT:
The invention provides a refrigeration system employing hot compressed gas from the compressor to defrost the cooling coil or coils. In prior systems this is accomplished by diverting part of the hot compressed gas to flow through the cooling coil, while the remainder continues to flow through the condensing coil to avoid overload of the compressor. It is found that as the ambient temperature of the condenser coil decreases the compressor output pressure also decreases, decreasing the amount of hot gas available for defrost, so that the period required for adequate defrost also varies. It is therefore necessary either to adjust the length of the defrost period with this ambient temperature, or make the period sufficiently long to ensure defrost at all times, the latter resulting in inefficient operation. In accordance with the invention, during a defrost period, upon detection of a lower predetermined pressure at the condenser coil outlet, a valve at the compressor outlet is operated to bypass the condenser coil and deliver hot compressed refrigerant directly to the liquid collector (which may be the liquid line) through a check valve that prevents delivery of refrigerant to the condensor coil and return of refrigerant from the collector to the condenser coil. If the pressure detected reaches a higher predetermined value, indicating that the compressor is becoming overloaded, the valve returns to delivering the refrigerant to the condenser coil until the pressure drops again to the lower value.
REFERENCES:
patent: 3464226 (1969-09-01), Kramer
patent: 3905202 (1975-09-01), Taft et al.
patent: 4193781 (1980-03-01), Vogel et al.
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