Daikin VRV - WII Service Manual page 263

Troubleshooting (OP: Unified ON/OFF Controller)
[CHECK 2] Check for causes of drop in low pressure
Referring to the Fault Tree Analysis (FTA) shown below, identify the faulty points.
Faulty low
pressure
control
[In both cooling
and heating]
(∗2)
Abnormally low [In cooling]
low-pressure (Low
If the indoor unit
evaporating
electronic
temperature)
expansion valve
is excessively
throttled
(∗3)
Faulty electronic
expansion valve
control
[In heating]
If the outside unit
electronic
expansion valve
is excessively
throttled
(∗4)
Degradation in
evaporating
capacity
Less circulation
quantity of
refrigerant
∗1 : For details of the compressor capacity control while in cooling, refer to "Compressor Control" on page 65.
∗2 : The "low pressure protection control" includes low pressure drop control and hot gas bypass control. For
details, refer to page 71.
∗3 : In cooling, the indoor unit electronic expansion valve is used for "superheated degree control". (For details,
refer to page 89.)
∗4 : In heating, the outdoor unit electronic expansion valve (Y1E) is used for "superheated degree control of
outside unit heat exchanger". (For details, refer to page 67.)
250
[In cooling]
Faulty
(∗1)
compressor
capacity
control
Faulty low
pressure
protection control
Faulty indoor unit
electronic
expansion valve
Faulty
control
Faulty outside
unit electronic
expansion valve
Faulty
control
Low suction air
temperature of
indoor unit
[In cooling]
Faulty suction air thermistor of indoor unit
Decreased
fan airflow
rate
Low water temperature at the water heat exchanger inlet
Dirty water heat exchanger
[In heating]
High pipe
resistance
Inadequate refrigerant quantity
Moisture choke
Faulty low pressure sensor
Faulty control PCB
Faulty low pressure sensor
Faulty hot gas solenoid valve
Faulty control PCB
Faulty valve coil
Faulty valve body
Faulty gas pipe thermistor
of indoor unit
Faulty liquid pipe thermistor
of indoor unit
Faulty control PCB
Faulty valve coil
Faulty valve body
Faulty low pressure sensor
Faulty suction pipe thermistor
Faulty control PCB
Short circuit
Low ambient temperature
Faulty fan motor
Decreased
fan output
Faulty control PCB
(including capacity
setting)
High air
passage
Dirty filter
resistance
Obstacle
← Is the water temperature at the water heat
exchanger inlet not less than 50°F?
← Is the water heat exchanger clogged?
Abnormal piping length
Bent or Crush of pipe
Clogging of foreign particles
Stop valve closed
← Refer to [CHECK 6] on page 254.
← Eliminate moisture by vacuum break.
← Are the voltage characteristics normal?
← Does the pressure value of the Service
Checker match the reading of the pressure sensor?
← Are the voltage characteristics normal?
← Are the coil resistance and insulation normal?
← Does the pressure value of the Service
Checker match the reading of the pressure sensor?
← Are the coil resistance and insulation normal?
← Check for the thermistor resistance and connection.
← Check for the thermistor resistance and connection.
← Does the pressure value of the Service Checker
match the reading of the pressure sensor?
← Are the coil resistance and insulation normal?
← Are the voltage characteristics normal?
← Check for the thermistor resistance and connection.
← Is the suction air temperature not less than 57.2°F?
← Is the indoor temperature not more than 57.2°F?
← Is the connector properly connected?
Are the thermistor resistance characteristics normal?
← Can the fan motor be rotated with hands?
Are the motor coil resistance and
insulation normal?
← If a spare PC board is mounted, is the
capacity setting properly made?
← Is the air filter clogged?
← Is there any obstacle in the air passage?
← Is the piping length in the permissible range?
← Conduct visual checks for pipe conditions.
← Is there any temperature difference around
the filter or the branch pipe?
← Check to be sure the stop valve is open.
SiUS30-604
Troubleshooting