Protection Function - Fujitsu AB12 Service Manual

5-12 PROTECTION FUNCTIONS
1. Central discharge temperature protection
1) When the discharge temperature of any compressor reaches 110 C or higher, solenoid valve 1 (SV1)
is turned on and bypass is performed. SV1 is turned off and central discharge temperature protection
operation is ended by any of the following conditions:
(1) Discharge temperature of all compressors reaches 95 C or lower
(2) Oil recovery operation starts
2) When solenoid valve 1 (SV1) is on and the outdoor fan speed is "5", solenoid valve 2 (SV2) is simultaneously
turned on and bypass is performed. SV2 is turned off by any of the following conditions:
(1) Outdoor fan speed is set to other than "5"
(2) Oil recovery operation starts
(3) Discharge temperature of all compressors reaches 95 C or lower.
2. Discharge temperature protection
When the discharge temperature of any compressor reaches 130 C or higher, the corresponding compressor
stops. Compressor stop is reset and discharge temperature protection operation is ended by any of the following
conditions:
(1) Discharge temperature of all compressors reaches 95 C or lower.
(2) Oil recovery operation starts
However, during oil recovery operation, discharge temperature protection is not performed.
3. High-pressure protection
1) When the high-pressure SW (HP) is turned off except during oil recovery operation or defrosting,
solenoid 1 (SV1) and solenoid 2 (SV2) are turned on and bypass is performed. SV1 and SV2 are turned
off by any of the following conditions:
(1) High-pressure pressure SW turned on
(2) Oil recovery control starts
(3) Defrosting control starts
2) When 1 minute has elapsed after SV1 and SV2 were turned on and the discharge pressure sensor (PH)
detected value is 3.34MPa or greater, compressors 1, 2, and 3 are stopped. SV1 and SV2 ON and
compressors 1, 2, and 3 stop are reset and high-pressure protection operation is ended by any of the
following conditions:
(1) High-pressure SW (HP) turned on
(2) Oil recovery control starts
(3) Defrosting control starts
4. Heating overload protection
When the operating mode is " Heating " and the high-pressure SW (HP) was turned off except during oil recovery or
defrosting in the "Heat mode", the outdoor fan is stopped. Outdoor fan stop is reset and heat overload protection operation
is ended by any of the following conditions:
(1) High-pressure SW (HP) turned on
(2) Oil recovery control starts
(3) Defrosting control starts
(4) Mode is switched to other than "Heat"
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