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10Backup Operation
(Emergency Operation)
This product offers backup modes of operation to tide over certain emergency situations. If a fault occurs in one of
the compressors, it is possible to operate the system on an emergency basis by operating only the remaining
compressor(s), (compressor backup operation).
If one of the outdoor units fails in a combined outdoor unit system, the system can be operated on an emergency
basis by keeping only the remaining outdoor unit(s), (outdoor unit backup operation).
Perform backup operation setting in accordance with the procedure described below.
10-1.Note for backup operation
The method of backup operation differs according to the contents of fault as shown in the table below.
Note 1: If the compressor has failed due to a fault in its motor coil (e.g. a layer short-circuit), do not preform
compressor backup operation because of severe oil degradation. It could damage other outdoor units.
Note 2: Keep the number of backed-up outdoor units under compressor backup operation to one in the system
(single refrigerant line). For a three-compressor model, the backing up of two faulty compressors is
prohibited.
Note 3: It is prohibited to combine compressor backup operation and outdoor unit backup operation.
Note 4: With a two-outdoor unit system containing an MMY-
MAP0964HT6UL and a MMY-MAP0724HT6UL, do not
preform outdoor unit backup operation to back up the
MMY-MAP0964HT6UL.
It could lead to compressor failure due to the abnormal
operation.
Contents of fault Method of backup operation Setting procedure
One of the compressors in the same unit fails (see Note 1) Compressor backup (see Note 2) Go to 10-2.
All the compressors in the same unit fail Outdoor unit backup or cooling-
season outdoor unit backup (see
Notes 1, 3, 4)
Go to 10-3. or 10-4.
A fault occurs in a compressor motor coil (e.g. a layer short-circuit)
A fault occurs in a refrigerating cycle part, fan or related part, or electrical part
A fault occurs in a temperature sensor or pressure sensor
Prohibited
Prohibited
Example
Example
Backed-up compressor
Backed-up compressor
Two backed-up compressors
Faulty
Faulty
Faulty
Faulty
Backed-up compressor
Backed-up outdoor unit
Prohibited
Example
Faulty
Faulty
Backed-up outdoor unit
Faulty
Prohibited
Example
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