Daikin Indoor Concealed Ceiling Unit FBQ125D2VEB

Warning: This procedure requires trained personnel with PPE!

Is the problem related to the thermistors?

If the problem is not related to the thermistors, report the issue to the maintenance team and stop the procedure

Disconnect the thermistor from the PCB

Check if the measured values correspond with the values in the table

Sign off on the thermistor check

Warning: Do not touch the charged area (high voltage) for 10 minutes after turning the power supply off.

If you must touch such an area, make sure that the power supply voltage of power transistor is 50 V or less.

Disconnect the connector of the outdoor unit fan motor.

Before measuring the continuity, disconnect the connection between compressor and power transistor.

Power supply voltage of power transistor is 50 V or less?

Connection between compressor and power transistor disconnected?

Is the resistance the same as each phase?

Caution: Removing electrical components

Remove the cover screws before removing an electrical component

Replace the grease on the heat sink with new grease

Remove fixation screw A (2 screws)

Lift and pull the cover in the direction of the arrow

Pull the refrigerant pipe forward

Remove fixation screw B (4 screws)

Caution: Do not touch the hatched area

As criteria for judging whether refrigerant is excessively charged or not, refer to the following operating conditions.

<Diagnosis of excessive refrigerant charging>

(1) Because high pressure rises due to excessive charging, overload control is carried out and capacity tends to run short.

(2) Considering pressure load, compressor discharge pipe temperature is low.

(3) Subcooled degree of condensate liquid becomes large. Therefore, temperature of blown air passing through subcooled part decreases in heating operation.

*3 This measured temperature is used to calculate the equivalent saturation pressure of the refrigerant.

Diagnosis of inadequate refrigerant in cooling operation

Suction superheat degree increases due to refrigerant shortage

Decreased evaporator capacity caused by refrigerant shortage

Compressor frequency decreases despite a large difference between temperature set by the remote controller and indoor suction temperature

If refrigerant shortage worsens, the electronic expansion valve remains fully open and suction superheat degree further increases

Diagnosis of inadequate refrigerant in heating operation

Suction superheat degree increases due to refrigerant shortage

Compressor frequency decreases because suction superheat degree is controlled to prevent oil to the outdoor heat exchanger from being retained

Evaporator capacity and compressor frequency decrease despite a large difference between temperature set by the remote controller and indoor suction temperature