Defrosting Control - Fujitsu AB12 Service Manual

5-9 DEFROSTING CONTROL

1. Defrosting start conditions
1) Defrosting start conditions
When the forced defrosting SW was operated, or all of the following conditions are satisfied, defrosting starts.
Operation mode is "Heating" and the integrated operating time in the state in which any of the compressors
is operating has reached 40 minutes or longer
When the operating time of any compressor is the specified time (A minutes) or longer. Where, A is defined as follows:
When the "all compressors stopped" state has continued for 20 minutes or longer before any compressor operates A=10
Other than the above A= 6
When the outlet temperature of each heat exchanger is -5 C or less
2) Integrated time
The time the operation mode is "Heating" and the time any compressor has operated are integrated. However, the integrated
value is cleared in the following cases:
Operation mode is switched to other than "Heating"
Defrosting has ended
Oil recovery operation is in progress and the heat exchange outlet temperature satisfies the defrosting end condition
2. Defrosting start restrictions
In the following cases, defrosting is not performed even if the previously mentioned defrosting start conditions are satisfied.
Oil recovery operation is in progress
Error that prohibits defrosting operating was generated
Error other than compressor 1, 2, or 3 error, suction thermistor error, oil sensor error, oil recovery error, or EEPROM
access error.
Following protection function has operated (Compressor OFF)
Compressor OFF by discharge temperature protector 1, 2, and 3 and high pressure protector, low voltage protector,
defrosting operation
3. Defrosting end condition
When any of the following conditions is satisfied, defrosting ends.
Outdoor unit operation mode was switched to other than "Heating"
20 minutes or longer have elapsed since defrosting stopped
Integration of compressor operation time after start of defrosting has exceeded 15 minutes
The following error was generated
Errors except compressor 1, 2, and 3 error suction thermistor error, oil sensor error, oil recovery error, or EEPROM
access error
Each heat exchanger outlet temperature has reached defrosting end heat exchanger temperature 10 C or higher.
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