Defrosting - Electrolux FROST REFRIGERATORS with ERF2021 electronic Service Manual

7.3. Defrosting

All the humidity in the compartment accumulates on the evaporator, which is the coldest part of the
compartment; periodically, about every 14 hours with normal door opening (up to 72 hours if the doors never
open!), it is then necessary to defrost the ice on the battery.
The defrosting starts after the compressor cut-out or if the compressor is on after 2,5 hours max.
The electronic board disconnects the circuit which powers the compressor (2) after 2 minutes the fan (24), waits
3 minutes then it powers the circuit of the defrosting heater (9) for a minimum time of about 20 minutes.
The heat generated by the defrosting heater does not affect the freezer compartment temperature or the food
packages temperature, because the thermal energy is consumed in the defrosting process of the evaporator ice.
When the defrosting switch cuts-out and, anyway after 20 minutes, the electronic board switches the compressor
on (2) with a 5 minute delay.
After 3 minute delay, when the air is already cold, the fan switches on too (24).
If for any reason, the defrosting cut-out switch (27) does not switch on and the battery temperature rises up to 40
°C, the defrosting heater (9) will be switched off by the safety thermal switch (26).
If 1 hour after the starting of the defrosting, the thermal switches did not cut out, the electronic board switches
the defrosting heater off and continues its operation.
The arrows in the picture indicate the current path.
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