Compressor Preheating; Defrost Operation Control - Fujitsu AB Series A18LATN Service Instruction

5-17. COMPRESSOR PREHEATING

When the outdoor heat exchanger temperature is lower than 5°C and the heating operation
has been stopped for 30 minutes, power is applied to the compressor and the compressor is heated.
(By heating the compressor, warm air is quickly discharged when operation is started.)
When operation was started, and when the outdoor temperature rises to 7°C or greater,
preheating is ended.

5-18. DEFROST OPERATION CONTROL

1. CONDITION OF STARTING THE DEFROST OPERATION
The defrost operation starts when the outdoor heat exchanger temperature sensor detects
the temperature lower than the values shown in Table 12.
(Table 12 : Condition of starting Defrost Operation)
1st time defrosting after starting operation
Compressor contiguous
operation time
Compressor integrating
operation time
Operation
temperature
Defrosting after 2nd time upon starting operation
Compressor contiguous
operation time
Compressor integrating
operation time
Operation
temperature
2. CONDITION OF THE DEFROST OPERATION COMPLETION
Defrost operation is released when the conditions become as shown in Table 13.
(Table 13 : Defrost Release Condition)
Outdoor heat exchanger temperature sensor value is higher than +10°C or
Compressor operation time has passed 15 minutes.
Below 10 min.
Less than 17 min.
Does not operate
Below 10 min.
Less than 35 min. 35 min. to 4 hours
Does not operate
Release Condition
05-18
Above 10 min.
17 to 62 min.
62 min. to 4 hours
- 9°C - 5°C
Above 10 min.
After 4 hours
- 6°C - 3°C
After 4 hours
- 3°C