Si12-411A Control Specification
Function and Control 97
3.10 Defrost Control
Outline Heat Pump Only
Defrosting is carried out by the cooling cycle (reverse cycle). The defrosting time or outdoor
heat exchanger temperature must be more than its fixed value when finishing.
Detail Conditions for Starting Defrost
The starting conditions must be made with the outdoor air temperature and heat exchanger
temperature. Under the conditions that the system is in heating operation, 6 minutes after the
compressor is started and more than 47 minutes of accumulated time pass since the start of the
operation or ending the defrosting.
Conditions for Canceling Defrost
The target heat exchanger temperature as the canceling condition is selected in the range of
4°C<Te<12°C according to the air temperature as the following formula.
The target heat exchanger temperature=–(45/65)×(ambient temperature)+14
The defrost operation surely operates in 120 seconds after the start. (A→B)
After then the defrost operation stops at the following conditions.
1. When the heat exchanger temperature reaches the target heat exchanger temperature.
(B→C)
2. When 650 seconds have passed after the start even if the heat exchanger temperature does
not reaches the target heat exchanger temperature. (C)
A B C
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