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6. OPERATION
The DF36 Electromechanical Frost Free refrigerator works under the vapor compression cycle R134-a. The vapor
is compressed in the alternate compressor, release heath in the condenser, is restricted into the capillary pipe and
absorbs heath in the flap tube evaporator, returning to the compressor as vapor through the suction line.
The cold air coming form the evaporator is forced by the motofan into the freezer and then conducted to the refrigerator
through the freezer and refrigerator top flow ducts. The temperature control in the refrigerator is done with the help of an
electromechanical thermostat located inside the top flow of this compartment which, in accordance to the temperature,
varies its diaphragm turning off or on the power for the compressor, timer, and evaporator motofan.
The temperature in the freezer compartment depends on the thermostat localized inside the refrigerator compartment
which will be controlling the temperature of that compartment. As the refrigeration need of the refrigerator compartment
is greater than the one of the freezer compartment, having the temperature control located in the refrigerator
compartment guarantees that the freezer will always be operating in an adequate temperature (below -18
º
C).
A greater refrigeration speed between the both compartments can be controlled through the mechanical damper
localized in the freezer’s top flow, which has three possible, adjust positions: maximum refrigerator, normal, and
maximum freezer.
6.1 Defrost
After cooling for some time, all the humidity introduced inside the product by the stored food, or by the opening of the
doors, will be retained in the evaporator and will gradually freeze. At that point, it will be necessary to remove this ice
in excess accumulated on the surface of the evaporator, through a defrost operation.
The product has a defrost resistance fixed to the evaporator and another resistance fixed to the defrost drain gutter,
localized in the refrigerator’s top flow, so as to prevent the freezing of the gutter thus facilitating the draining of the
water resulting from the defrost that comes from the evaporator. The evaporator and the gutter resistances’ are
connected in parallel.
During the defrost operation, the compressor, the motofan and the timer will remain turned off.
The resistances are turned on by the timer, with the monitoring of the defrosting end being done by the defrost
thermostat (bimetal). There is a thermal security fuse positioned in the up right side of the evaporator.
Note: The thermal fuse works in the case of a failure in one of the other circuits thus avoiding the defrost
resistance to heat too much. In case the thermal fuse is used it will be spoiled. Before replacing that
component, it’s mandatory that the problem that led to its use should have been identified and fully corrected.
The product must never be turned on without the thermal fuse being correctly installed.
6.1.1 Defrost Bimetal registering a temperature equal to or above +25°C ( ±3
º
C) when the refrigerator is turned on:
Accumulates 8 hours of compressor operation
Pause (10min)
(dripping with the resistances
already turned off)
Defrost (up to +25ºC in the
Bimetal)
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