Panasonic U-72MF2U9 Service Manual page 70

3. Backup Operation
3. Backup Operation
CAUTION
(2) Adjusting the refrigerant for backup operation
During backup operation, all of the service valves on the failed unit are closed. However, if a check of the backup
operating conditions shows that the level of gas is low, recover the refrigerant from the failed outdoor unit.
If the level of gas is too high, collect refrigerant at the failed outdoor unit.
Recovering refrigerant
With the normal outdoor units operating, monitor the operating condition and open/close the suction tube
service valve on the failed outdoor unit where all the service valves were closed.
In this way, recover refrigerant from the failed outdoor unit in order to adjust the amount of refrigerant in the
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system. After adjusting the amount of refrigerant, close the suction tube valve at the failed outdoor unit.
Collecting refrigerant in the failed outdoor unit
Short-circuit the AP pin (CN24) on the control PCB of the failed outdoor unit where the service valves
are closed, then turn the power ON. Also disconnect the wiring between the outdoor units.
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With the normal outdoor units operating, monitor the operating condition and open/close the liquid tube
service valve on the failed outdoor unit where all the service valves were closed.
In this way, collect refrigerant in the failed outdoor unit in order to adjust the amount of refrigerant in the
system.
After adjusting the amount of refrigerant, turn OFF the power at the failed outdoor unit, release the short-
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circuit at the AP pin (CN24), and close the liquid tube valve at the failed outdoor unit.
* Refrigerant recovery is not affected by the power status of the failed outdoor unit. However, collecting
refrigerant in the failed outdoor unit is affected by whether the power at that outdoor unit can be turned
ON. If the power cannot be turned ON, use a refrigerant recovery device and recover the refrigerant into
a recovery cylinder in order to adjust the amount of refrigerant in the system.
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After recovery work is completed, wire the communication lines between indoor and outdoor
units again. If it not finished yet, an alarm is emitted immediately.
Outdoor Unit Repair Procedures
Outdoor Unit Repair Procedures
2 - 6
2WAY VRF SYSTEM
3WAY VRF SYSTEM