Explain the purpose of a check valve. Explain the cool/heat/defrost cycle of a three-way valve refrigeration system. Explain the cool/heat/defrost cycle of a solenoid control refrigeration system. Explain the cool/heat/defrost cycle of a four-way reversing valve refrigeration system.
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Explain the operation of the three-way valve in the cooling cycle Explain the operation of the three-way valve in the heating cycle Explain the purpose of the pilot solenoid
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Refrigerant control valves are used to control the refrigerant units mode of operation from cool to heat/defrost mode by directing the flow of superheated refrigerant When the three-way valve is in the cool cycle, it directs the flow of refrigerant into the condenser
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Auto-defrost, automatic defrost or self-defrosting is a technique which regularly defrosts the evaporator in a refrigerator or freezer. Appliances using this technique are often called frost free, frostless or no-frost.
https://en.wikipedia.org/wiki/Auto-defrost
Describe the purpose of refrigerant cycle control devices. Explain the operation of the three-way valve in the cooling cycle. Explain the operation of the three-way valve in the heating cycle. Explain the purpose of the pilot solenoid. Describe the purpose of the condenser pressure bypass valve
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Defrosting may not be completed by the time the defrost timer cycles back into normal operation (esp. In Hot, humid conditions with frequent door openings), leaving ice/frost on the evaporator coils. This condition can lead to icing up which will interfere with the operation of the refrigerator.
https://en.wikipedia.org/wiki/Auto-defrost
Alternatively, some systems use the hot gas in the condenser to defrost the evaporator. This is done by means of a circuit that is cross-linked by a three-way valve. The hot gas quickly heats up the evaporator and defrosts it.
https://en.wikipedia.org/wiki/Auto-defrost
Defrosting is controlled by an electric or electronic timer: For every 6, 8, 10, 12 or 24 hours of compressor operation it turns on a defrost heater for 15 minutes to half an hour. The defrost heater, having a typical power rating of 350 W to 600 W, is mounted just below the evaporator in top- and bottom-freezer models and below and sometimes also in the middle of the evaporator in side-by-side models.
https://en.wikipedia.org/wiki/Auto-defrost
Refrigerant control valves are used to control the refrigerant units mode of operation from cool to heat/defrost mode by directing the flow of superheated refrigerant. When the three-way valve is in the cool cycle, it directs the flow of refrigerant into the condenser.
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The four-way valve system requires two TXV valves due to the changing of the normal condenser to an evaporator during heat/defrost cycle. The flow of the refrigerant in the defrost cycle is identical to that of the unit’s heating cycle, regardless of manufacturer.
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defrost cycle operation
The operation of defrost cycle is identical to that of the unit’s heating cycle and regardless of manufacturer.