Defrost Operation Control - Fujitsu AUXG36KRLB Service Manual

6. Defrost operation control

Tn: Outdoor unit heat exchanger temperature
Ta: Outdoor temperature
Tn10: Temperature at 10 minutes after compressor start
Tnb: Temperature before 5 minutes
Triggering condition
•
The defrost operation starts when outdoor unit heat exchanger temperature sensor detects the
temperature lower than the values shown below.
– 1st time defrosting after starting operation
Compressor integrating
operation time
Condition
– 2nd time and after
Compressor integrating
operation time
Condition
– Integrating defrost (Constant monitoring)
Compressor integrating
operation time
Condition
*: If the compressor continuous operation time is less than 10 minutes, the number of the com-
pressor off is counted. If any defrost operated, the compressor off count is cleared.
Release condition
•
The defrost operation is released when either one of the conditions below is satisfied.
Outdoor unit heat exchanger temperature
(after 1 minute or later since compressor start)
Compressor operation time
Less than 17 min.
Does not operate
Less than 35 min.
Does not operate
More than 240 min. (For
long continuous
operation)
Tn ≤ -3°C
- (04-22) -
17 to 57 min.
Tn ≤ -9°C and Tn-Ta ≥ 5
deg
More than 35 min.
Tn-Tn10 < -5 deg (Tn ≤ -10°C)
Tn-Tnb < -2 deg (Tn ≤ -10°C)
Tn ≤ -25°C (Ta ≥ -20°C)
Tn ≤ Ta-7°C or Tn ≤ -25°C (Ta < -20°C)
More than 215 min. (For
long continuous
operation
Tn ≤ -5°C
More than 57 min.
Tn ≤ -5°C
Less than 10 min.* (For
intermittent operation)
Count of the compressor
off: 40 times
12°C or more
15 minutes
6. Defrost operation control