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a damper. By this means, a controlled portion of the air coming from the freezer reaches the refrigerator. Some older models have no air circulation between their freezer and refrigerator sections. Instead, they use an independent cooling system (for example: an evaporator coil with a defrost heater and a circulating fan in the freezer and a cold-plate or open-coil evaporator in the refrigerator.
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Freezers with automatic defrosting and combined refrigerator/freezer units which also apply self defrosting to their freezer compartment are called "frost free". The latter usually feature an air connection between the two compartments with the air passage to the refrigerator compartment regulated by
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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. This system is primarily used in commercial applications such as ice-cream
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A defrost thermostat opens the heater circuit when the evaporator temperature rises above a preset temperature, 40°F (5°C) or more, thereby preventing excessive heating of the freezer compartment. The defrost timer is such that either the compressor or the defrost heater is on, but not both at the
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to 600W, is often mounted just below the evaporator in top and bottom-freezer models. It can also be located below and in the middle of the evaporator in side-by-side models. It may be protected from short circuits by means of fusible links. In older refrigerators, the timer runs continuously. In
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to defrost their evaporators, a pan to collect and evaporate water from the frost that melts from the cold plate and/or evaporator coil, a timer which turns off the compressor and turns on the defrost element usually from once to 4 times a day for periods usually ranging from 15 to 30 minutes, a
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Defrosting may not be completed by the time the defrost timer cycles back to normal operation (especially in hot, humid conditions with frequent door openings), leaving ice/frost on the evaporator coils. This condition can lead to "icing" which will interfere with the operation of the
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that has formed on it. The resulting water drains through a duct at the back of the unit. 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.
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Instead of the traditional cooling elements being embedded in the freezer liner, auto-defrost elements are behind or beneath the liner. This allows them to be heated for short periods of time to dispose of frost, without heating the contents of the freezer.
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referred to their semi-automatic models as "Cycla-Matic," Kelvinator often named these models as "Cyclic
Defrost" ). These refrigerators usually have a pan underneath where water from the melted frost in the refrigerator section evaporates.
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defrost limiter thermostat that turns off the heating element before the temperature rises too much while the timer is still in its defrost phase. Some models also feature a drain heater to prevent ice from blocking the drain.
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Some newer refrigerator/freezer models have a computer that monitors how many times each door is opened and uses this data to control defrost scheduling thereby reducing power use.
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newer designs, the timer only runs while the compressor runs, so the longer the refrigerator door is closed, the less time the heater will run for and the more energy is saved.
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any ice or frost that may form on frozen items in the freezer compartment. While defrosting, this fan is stopped to prevent heated-up air from reaching the food compartment.
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Other early types of refrigerators also use hot gas defrost instead of electric heaters. These reverse the evaporator and condenser sides for the defrost cycle.
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The temperature of the freezer contents rises during the defrosting cycles, especially if there is a light load in the freezer. This can cause "
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Increased electrical and mechanical complexity compared to a basic upright freezer or chest freezer, making it more prone to component failure.
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While this technique was originally applied to the refrigerator compartment, it was later used for freezer compartment as well.
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The system can be more expensive to run when usage is high and if the fan continues or starts to run when the door is opened.
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The defrost mechanism in a refrigerator heats the cooling element (evaporator coil) for a short period of time and melts the
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A combined refrigerator/freezer which applies self-defrosting to the refrigerator compartment only is usually called "
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No need to manually defrost the frost buildup, therefore power consumption will not increase with time.
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In laboratories, self-defrosting freezers must not be used to store certain delicate reagents such as
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Smells are limited, especially in total frost-free appliances because the air always circulates.
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of the reagents. Self-defrosting freezers should never be used to store flammable chemicals.
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A thermal cutout safety device is required to prevent overheating of the heating element.
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Estimates of
Refrigerator Loads in Public Housing Based on Metered Consumption Data
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frost free" or semi-automatic defrost (some brands call these "Auto
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On hot, humid days condensation will sometimes form around the refrigerator doors.
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457:"How to Replace your Fridge's Defrost Heater | Refrigerator Repair"
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The defrost heater, having a typical power rating of 350
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A defrost timer taken out of a household refrigerator
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16:Frost suppression in refrigerators or freezers
432:"How does a frost-free refrigerator work?"
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109:Learn how and when to remove this message
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419:References
254:Advantages
229:Frigidaire
212:displays.
150:frost free
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202:sublimate
164:Mechanism
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