Backup Operation (Emergency Operation); Note For Backup Operation - Carrier MMY-MAP0724FT9UL Service Manual

10. BACKUP 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.
One of the compressors in the same unit fails (see Note 1)
All the compressors in the same unit fail
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
Note 1: 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.
Example
Prohibited
Note 2: It is prohibited to combine compressor backup operation and outdoor unit backup operation.
Note 3: With a two-outdoor unit system containing an MMY-MAP120
do not preform outdoor unit backup operation to back up the MMY-MAP120
It could lead to compressor failure due to the abnormal operation.
Contents of fault
Backed-up compressor Backed-up compressor
Backed-up compressor
Example
Prohibited
Example
Prohibited
Method of backup operation
Compressor backup (see Note 1)
Outdoor unit backup or cooling-
season outdoor unit backup (see
Notes 2 and 3)
Example
Prohibited
Backed-up outdoor unit
Faulty
Backed-up outdoor unit
Faulty
MMY-MAP072∗
MMY-MAP120∗
(MMY-MAP096∗)
– 207 –
Two backed-up compressors
∗ ∗
(or MAP096 ) and an MMY-MAP072
∗
(or MAP096
Setting procedure
Go to 11-2.
Go to 11-3
∗
,
∗
).