Defrost control method and apparatus
First Claim
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1. Apparatus for use with a refrigeration system wherein refrigerant circulates through a heat exchanger comprising:
- a. control means for monitoring compressor run time by counting cycles of an AC line voltage when the compressor is running including a programmable controller having an input that can be coupled to a thermostat for monitoring a heating or cooling demand signal and having a defrost output for outputting a defrost signal after a programmable period of compressor run time as indicated by the number of AC line cycles counted during the presence of the demand signal at said input; and
b. defrost means coupled to the programmable controller for defrosting the heat exchanger in response to receipt of a defrost signal.
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Abstract
A defrost controller for a refrigeration system. The system includes a circuit having a programmable controller which monitors compressor demand from a thermostat and uses alternating current cycles of a line voltage to control on and off cycles for a defrost mode of the refrigeration system. An anti-short cycle feature is optionally included to inhibit compressor operation for a predetermined interval each time the compressor is disabled.
99 Citations
11 Claims
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1. Apparatus for use with a refrigeration system wherein refrigerant circulates through a heat exchanger comprising:
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a. control means for monitoring compressor run time by counting cycles of an AC line voltage when the compressor is running including a programmable controller having an input that can be coupled to a thermostat for monitoring a heating or cooling demand signal and having a defrost output for outputting a defrost signal after a programmable period of compressor run time as indicated by the number of AC line cycles counted during the presence of the demand signal at said input; and b. defrost means coupled to the programmable controller for defrosting the heat exchanger in response to receipt of a defrost signal. - View Dependent Claims (2, 3, 4)
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5. A refrigeration system control unit for governing defrosting of a system heat exchanger in response to sensed conditions;
- said control unit comprising a programmable controller having a first input for monitoring heating or cooling demands of a region, a second input for monitoring cycles of an alternating current power source and an output for initiating defrost of the heat exchanger, said programmable controller programmed to periodically check a status of the first and second inputs, update a count at the cycle rate of the second input during heating or cooling demand periods as indicated by the first input; and
initiate a defrost of the heat exchanger after a predetermined heating or cooling demand period based upon the value of said count.
- said control unit comprising a programmable controller having a first input for monitoring heating or cooling demands of a region, a second input for monitoring cycles of an alternating current power source and an output for initiating defrost of the heat exchanger, said programmable controller programmed to periodically check a status of the first and second inputs, update a count at the cycle rate of the second input during heating or cooling demand periods as indicated by the first input; and
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6. In a refrigeration system, a method for governing defrosting of a system heat exchanger;
- said method comprising the steps of sensing an alternating current signal that passes through a thermostat switch to activate a compressor motor during heating or cooling demand periods, subsequent to sensing a presence of the alternating current signal, counting cycles of an alternating current power source during the heating or cooling demand periods; and
initiating a defrost of the heat exchanger after a predetermined cumulative heating or cooling demand period based upon a comparison between a count of said cycles and a defrost count corresponding to the cumulative heating or cooling demand period. - View Dependent Claims (7, 8, 9, 10, 11)
- said method comprising the steps of sensing an alternating current signal that passes through a thermostat switch to activate a compressor motor during heating or cooling demand periods, subsequent to sensing a presence of the alternating current signal, counting cycles of an alternating current power source during the heating or cooling demand periods; and
Specification