HVACR: How A Refrigerator/Freezer Defrost Timer Works/Defrost Timer Troubleshooting/Sequence Of Operation(How To Check A Defrost Timer For A Refrigerator/Freezer) SUPCO PSA140100 DEFROST TIMER

Commercial refrigeration systems are essential to the preservation of vast amounts of food products, and/or pharmaceutical materials in research settings. Refrigeration failures, therefore, are costly in terms of lost product and business.

For that reason alone, every component must function precisely as designed. That includes defrost controls. Defrost controls prevent the build up of frost or ice from refrigeration system equipment and supporting component parts.

The heat output that makes the defrosting possible is provided by either an electric or hot gas defrost system. Defrosts can be programmed to occur automatically, or they can be performed manually. Key parameters to any defrost event are of course time, temperature, and/or pressure set points. The setpoints control the defrost initiation start time and termination end time. As the defrost heats the coil to remove ice, fans are on hold until the termination set point has been met.

There are two types of defrost timers used in modern refrigerators constant, or continuous run timers, and accumulative timers. Constant or continuous run defrost timers run continuously as long as the refrigerator is plugged in. Accumulative defrost timers run only when the compressor is running. Accumulative defrost timers are also known as demand defrost.

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