Daikin VRV-WIII RWEYQ72PTJU Service Manual page 250

Troubleshooting by Indication on the 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 2.)
Abnormally low
[In cooling]
low-pressure (Low
If the indoor unit
evaporating
temperature)
electronic
expansion valve is
excessively
throttled: (See 3.)
Defective electronic
expansion valve
control
[In heating]
If the condensing
unit electronic
expansion valve
excessively
throttled:
(See 4.)
Low suction
air
temperature
of the
evaporator
Less
circulation
quantity of
refrigerant
Degradation
incondensing
capacity
1: For details of the compressor capacity control while in cooling, refer to Compressor PI Control.
Note:
2: The "low pressure protection control" includes low pressure protection control and hot gas
3: In cooling, the indoor unit electronic expansion valve is used for superheated degree control.
4: In heating, the condensing unit electronic expansion valve (EVM) is used for superheated
242
[In cooling]
(See 1.)
Defective
compressor
capacity
control
Defective low
pressure
protection control
Defective indoor
unit electronic
expansion valve
Defective
control
Defective condensing
unit electronic
expansion valve
Defective
control
[In cooling]
Low suction air
temperature of
indoor unit
Defective suction air thermistor of indoor unit
Low suction air temperature of condensing
Defective outdoor air temperature thermistor of conddensing unit
[In heating]
High pipe
resistance
Inadequate refrigerant quantity
Moisture choke
Dirty evaporator
Decreased
fan airflow
rate
bypass control.
degree control of condensing unit heat exchanger.
 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 control PCB
 Are the electrical characteristics normal?
Defective low pressure sensor
 Are the coil resistance and insulation normal?
Defective hot gas solenoid valve
 Is the pressure value checked with the Service Checker
Defective control PCB
 Are the coil resistance and insulation normal?
Defective valve coil
Defective valve body
 Check for the thermistor resistance and
Defective gas pipe
thermistor of indoor unit
 Check for the thermistor resistance and
Defective liquid pipe
thermistor of indoor unit
 Is the pressure value checked with the Service Checker
Defective control PCB
 Are the coil resistance and insulation normal?
Defective valve coil
Defective valve body
 Are the electrical characteristics normal?
Defective low pressure sensor
 Check for the thermistor resistance and
Defective suction pipe thermistor
Defective control PCB
 Is the suction air temperature not less than 57.2°F?
Short circuit
 Is the indoor air temperature not more than 57.2°F?
Low outdoor air temperature
 Is the connector properly connected?
 Is the condensing air temperature more than -4°F?
unit
 Is the connector properly connected?  Is the connector properly connected?
 Does the piping length fall in the permissible range?
Abnormal piping length
 Conduct visual checks for pipe conditions.
Bent or crashed pipe
 Is there any temperature difference caused
Clogging of foreign particles
 Check to be sure the stop valve is open.
Stop valve closed
 Refer to
CHECK 7
 Eliminate moisture by vacuum operation.
 Is the heat exchanger clogged?
Defective fan motor
Decreased
fan output
Defective control PCB
(Including capacity setting)
High air
passage
Dirty filter
resistance
Obstacle
corresponding to the measurement of the pressure sensor? corresponding to the measurement of the pressure sensor?
corresponding to the measurement of the pressure sensor?
connection.
connection.
corresponding to the measurement of the pressure sensor?
connection.
Are the thermistor resistance characteristics normal?
Are the thermistor resistance characteristics normal? Are the thermistor resistance characteristics normal?
before and after the filter or branch pipe?
 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?
SiUS30-1301
Service Diagnosis