Daikin VRV II-Q RQYQ8-48PY1B Service Manual page 190

Troubleshooting by Remote Controller
CHECK 2
Check for causes of drop in low pressure
Referring to the Fault Tree Analysis (FTA) shown below, probe the defective points.
Defective low
pressure
control
[In both cooling
and heating]
∗
(See
Abnormally low
[In cooling]
low-pressure (Low
If the indoor unit
evaporating
temperature)
electronic
expansion valve is
excessively
throttled: (See
Defective electronic
expansion valve
control
[In heating]
If the outside unit
electronic
expansion valve
excessively
throttled:
∗
(See 4.)
[In cooling]
Low suction
air
temperature
of the
evaporator
[In heating]
Less
circulation
quantity of
refrigerant
Degradation
in condensing
capacity
∗
1: For details of the compressor capacity control while in cooling, refer to "Compressor PI Control".
∗
2: The "low pressure protection control" includes low pressure protection control and hot gas bypass control.
∗
3: In cooling, the indoor unit electronic expansion valve is used for "superheated degree control".
∗
4: In heating, the outside unit electronic expansion valve (EVM) is used for "superheated degree control of
outside unit heat exchanger".
180
[In cooling]
∗
(See 1.)
Defective
compressor
capacity
control
Defective low
pressure
protection control
2.)
Defective indoor
unit electronic
expansion valve
∗
3.)
Defective
control
Defective outside
unit electronic
expansion valve
Defective
control
Low suction air
temperature of
indoor unit
Defective suction air thermistor of indoor unit
Low suction air temperature of outside unit
Defective outdoor air temperature thermistor of outside unit
High pipe
resistance
Inadequate refrigerant quantity
Moisture choke
Dirty evaporator
Decreased
fan airflow
rate
←
Are the electrical characteristics normal?
Defective low pressure sensor
← ←
Is the pressure value checked with the Service Checker Is the pressure value checked with the Service Checker
Defective service monitor PCB
corresponding to the measurement of the pressure sensor? corresponding to the measurement of the pressure sensor?
Defective low pressure sensor ←
Are the electrical characteristics normal?
←
Are the coil resistance and insulation normal?
Defective hot gas solenoid valve
←
Is the pressure value checked with the Service Checker
Defective service monitor PCB
corresponding to the measurement of the pressure sensor?
←
Are the coil resistance and insulation normal?
Defective valve coil
Defective valve body
←
Check for the thermistor resistance and
Defective gas pipe
connection.
thermistor of indoor unit
←
Check for the thermistor resistance and
Defective liquid pipe
connection.
thermistor of indoor unit
←
Is the pressure value checked with the Service Checker
Defective service monitor PCB
corresponding to the measurement of the pressure sensor?
←
Are the coil resistance and insulation normal?
Defective valve coil
Defective valve body
←
Are the electrical characteristics normal?
Defective low pressure sensor
Defective suction pipe thermistor ←
Check for the thermistor resistance and
connection.
Defective service monitor PCB
←
Is the suction air temperature not less than 14°C?
Short circuit
←
Is the indoor temperature not more than 14°C?
Low outdoor air temperature
←
Is the connector properly connected?
Are the thermistor resistance characteristics normal?
←
Is the outdoor air temperature more than -20°C?
← ←
Is the connector properly connected? Is the connector properly connected?
Are the thermistor resistance characteristics normal? Are the thermistor resistance characteristics normal?
←
Abnormal piping length Does the piping length fall in the permissible range?
←
Conduct visual checks for pipe conditions.
Bent or crashed pipe
←
Is there any temperature difference caused
Clogging of foreign particles
before and after the filter or branch pipe?
←
Check to be sure the stop valve is open.
Stop valve closed
←
Eliminate moisture by vacuum operation.
←
Is the heat exchanger clogged?
Defective fan motor
Decreased
fan output
Defective service monitor PCB
(Including capacity setting)
High air
passage
Dirty filter
resistance
Obstacle
SiBE341027
←
Can the fan motor be rotated with hands?
Are the motor coil resistance and insulation normal?
←
If a spare PCB is mounted, is the
capacity setting properly made?
←
Is the air filter clogged?
←
Is there any obstacle in the air passage?
Service Diagnosis