Low-Voltage Detection Or Over-Voltage Detection - Daikin FTKM-U Series Service Manual

Troubleshooting
4.7

Low-voltage Detection or Over-voltage Detection

U2
Error Code
Method of Error
 Indoor Unit
Detection The zero-cross detection of the power supply is evaluated by the indoor unit PCB.
 Outdoor Unit
Low-voltage detection:
An abnormal voltage drop is detected by the DC voltage detection circuit.
Over-voltage detection:
An abnormal voltage rise is detected by the over-voltage detection circuit.
Error Decision
 Indoor Unit
Conditions There is no zero-cross detection in approximately 10 seconds.
 Outdoor Unit
Low-voltage detection:
Over-voltage detection:
Supposed  Power supply voltage out of specification
Causes  Defective DC voltage detection circuit
 Defective over-voltage detection circuit
 Defective PAM control part
 Disconnection of compressor harness
 Short circuit inside the fan motor winding
 Noise
 Momentary drop of voltage
 Momentary power failure
 Defective outdoor unit PCB
 Defective indoor unit PCB
64
 The voltage detected by the DC voltage detection circuit is below 150 ~ 200 V (12/18
class) or 180 ~ 196 V (24 class)
 The compressor stops if the error occurs, and restarts automatically after 3-minute
standby.
 An over-voltage signal is fed from the over-voltage detection circuit to the microcomputer
(over 458 ~ 500 V, depending on the model).
 The compressor stops if the error occurs, and restarts automatically after 3-minute
standby.
SiMX042215E
Part 6 Service Diagnosis