Freeze-Up Protection Control - Daikin CTX Series Service Manual

DAMA-SM-21-003
4.3

Freeze-up Protection Control

A5
Error Code
Method of Error
During cooling operation, the freeze-up protection control (operation halt) is activated according
to the temperature detected by the indoor heat exchanger thermistor.
Detection
High pressure control (heat pump model only).
During heating operations, the temperature detected by the indoor heat exchanger.
Thermistor is used for the high pressure control (stop, outdoor fan stop, etc.).
Error Decision
During cooling operation, the indoor heat exchange temperature is below 0°C (32°F).
High pressure control
Conditions
During heating operations, the temperature detected by the indoor heat exchanger thermistor is
above 61°C (141.8°F).
 Indoor Short-circuited air
Supposed
 Clogged air filter of the indoor unit
Causes
 Dust accumulation on the indoor heat exchanger
 Defective indoor heat exchanger thermistor
 Defective indoor unit PCB
Troubleshooting
Reference
Check No.01 Refer to P.85
Note
When replacing the defective thermistor(s), replace the thermistor as ASSY.
Service Diagnosis
Be sure to turn off the power switch before connecting or disconnecting
connectors, or parts may be damaged.
Caution
Check the air passage.
Is there any short circuit?
NO
Check the air filter.
Dirty?
NO
Check the dust accumulation on
the indoor heat exchanger.
Dirty?
NO
Check No. 01
Check the indoor heat exchanger
thermistor.
As
described in the
thermistor characteristic
chart?
YES
YES
YES
YES
NO
Troubleshooting
Provide sufficient air passage.
Clean the air filter.
Clean the indoor heat
exchanger.
Replace the indoor heat
exchanger thermistor.
Replace the indoor unit PCB
(control PCB).
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