II–2(2) About backup operation during maintenance work● What is backup operation?In the W MULTI series, multiple outdoor units are connected to the same refrigerant tube as shown in Figure 1.Therefore, even during maintenance work of an outdoor unit, the other outdoor unit not required in maintenancework can be used to keep the indoor operating conditions. This is called a backup operation.● Backup operation procedureTo perform backup operation, the outdoor unit for maintenance work (hereafter referred to as “target outdoorunit”) must be cut off from the system using the following procedure. Review content of the maintenance workand then select the most suitable method.Also, after the maintenance work is finished, always refer to [System recovery procedure] and then return thesystem to its normal state.[Backup operation procedure]To turn off power of target outdoor unit and then perform maintenance work (basic operation during inspectionof outdoor unit)<>This is the basic operation performed during inspection work. If this operation is not performed and the powerof the outdoor unit is turned off, this will cause system fault and prevent backup operation to be carried out,and serious malfunction will occur. If this happens, see [System recovery procedure] to recover the system, andthen once again use the following procedure to perform setup. Automatic backup operation will kick in.<>On the outdoor main board of the target outdoor unit,set the STOP switch (S001) to “STOP”. *1<>(After confirming that the engine of the target outdoorunit is stopped) close the valves of refrigerant gas tube,refrigerant gas liquid tube, and balance tube.<>On the outdoor main board of the target outdoor unit,set the STOP switch (S001) to “STOP”. Wait for threeminutes or more and then turn off the circuit breaker ofthe target outdoor unit. *2Start maintenance work.*1) Sometimes all outdoor units may stop. If there is operation input, outdoor units other than the target one willstart operation again after approximately five minutes. (For details on the settings, see the next item.)*2) Always carry out the following three tasks.c Check to make sure <> is finished. If the shutoff valve is opened, refrigerant will flow from theother outdoor unit to the target outdoor unit, causing serious malfunction.d After three minutes has elapsed from completion of <>, check to make sure the outdoor mainboard displays “ ” and then perform this operation. If you turn off the power immediatelyafter performing “STOP” setting, the entire system will stop. (Backup operation cannot be performed.) Ifthis happens, see [System recovery procedure], recover the system, and then start over again starting from<>.e There will not be any problem whether the circuit breaker of the outdoor unit in <> is ON or OFF.Select one of them according to the work required.
