Fisher FSK-124HF Technical & Service Manual page 22

3.3 Defrost
3.3.1 The defrosting of FSK-124-184-244HF is processed by indoor control board.
3.3.1.1 Defrosting Conditions
3.3.1.1.1 Low temperature defrosting condition:
Accumulated operating time when temperature of outdoor heat exchanger coil T3 is below -2°C reaches
up to over 40 minutes.
3.3.1.1.2 High temperature defrosting condition:
Under high temperature protection of evaporator, the time when outdoor fan is shut down but compressor
is not has been accumulated for up to 90 minutes. It is considered that defrosting is performed when
either 3.3.1.1 or 3.3.1.2 is met.
3.3.1.2 Defrosting Action
Four-way valve and outdoor fan are shut down. Indoor fan operates according to anti-cold air function.
Compressor keeps on continuously.
3.3.1.3 Ending Of Defrosting Condition
It is considered that defrosting condition is ended when any of the conditions is met:
3.3.1.3.1 Operating current of compressor reaches 1.5Ie.
3.3.1.3.2 Time of defrosting reaches 10 minutes.
3.3.1.3.3 Temperature of outdoor coil T3 is up to 20°C.
3.3.1.4 Ending Action of Defrost
3.3.1.4.1 Outdoor fan and four-way valve are open.
3.3.1.4.2 Compressor keeps on continuously.
3.3.1.4.3 Indoor fan acts according to anti-cold air function.
3.3.1.4.4 Defrosting/pre-heating lamp continues to be on until indoor fan starts up.
3.3.2 The defrosting of FSK-364-484HF is processed by outdoor control board.
3.3.2.1 Defrosting Conditions(any of the following conditions is meet)
3.3.2.1.1 Under indoor pipe high temperature protection in heating mode, accumulated operating time is up to 90
minutes.(if outdoor fan is off and compressor are cut down, time again.)
3.3.2.1.2 When T4≥－8℃,1min, process the normal defrost mode: compressor operates continue 40 minute, the
accumulated time up to 40 minutes when pipe temperature sensor T3≤-2℃(if compressor is off, time again);
when defrosting ends, check T4 again.
3.3.2.2 Defrosting Action
When defrosting, the outdoor four-way valve is power off, defrosting valve is power on, outdoor fan is off,
compressor operate continue, indoor fan operates according to anti-cold air condition in heating mode. If indoor
fan is to be off, cut down the electric auxiliary heater and after 15 seconds cut down indoor fan.
3.3.2.3 Ending Action of Defrost(any of the following conditions is met)
3.3.2.3.1 Time of defrosting reaches 10 minutes.
3.3.2.3.2 Temperature of outdoor coil T3 is up to 20°C
3.3.2.4 Ending Action of Defrost
Operate in normal heating mode. After defrost stops, indoor fan starts to operate according to anti-cold air
condition.
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