Panasonic U-8MF2E8 Service Manual page 66

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 amount of gas is low, recover the refrigerant from the failed outdoor
unit. If the amount of gas is too high, collect refrigerant at the failed outdoor unit.
Recovering refrigerant
With the normal outdoor units operating in cooling, monitor the operating condition and open/close the gas tube
service valve on the failed outdoor unit where all the service valves were closed. In this way, recover refriger-
ant from the failed outdoor unit in order to adjust the amount of refrigerant in the system.
After adjusting the amount of refrigerant, close the gas tube valve at the failed outdoor unit.
2
Collecting refrigerant in the failed outdoor unit
• Short-circuit the vacuum application 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.
• With the normal outdoor units operating, monitor the operating condition and open/close the liquid tube ser-
vice 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-
circuit at the vacuum application pin, 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.
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
2 - 6
3WAY SYSTEM