Daikin VRV III REYQ8PY1 Service Manual page 359

Troubleshooting (OP: Unified ON/OFF Controller)
[CHECK 3] Check the Factors of Overheat Operation
Identify the defective points referring to the failure factor analysis (FTA) as follows.
Faulty
discharge
pipe
temperature
control
Temperature
increase of
discharge
pipe
Compressor
overheat
[In cooling mode]
When indoor unit
electronic
expansion valve
becomes too
narrow (∗3)
Faulty
superheated
degree
control.
[In heading
mode]When
outdoor unit
electronic
expansion valve
becomes too
narrow (∗4)
Refrigerant gas
shortage
Large resistance
of piping
∗1: Refer to "Low pressure protective control" (P126) for hot gas bypass control.
∗2: Refer to P108 for subcooling electronic expansion valve control.
∗3: "Superheating temperature control" in cooling mode is conducted by indoor unit electronic expansion valve. (Refer to P141)
∗4: Superheating temperature control in heating mode is conducted by outdoor unit electronic expansion valve (EVM).
(Refer to P108).
∗5: Judgment criteria of superheat operation:
Suction gas superheating temperature: 10 degrees and over.
and over, except for immediately after starting and drooping control, etc..
(Use the above stated values as a guide. Depending on the other conditions, the unit may be normal despite the values
within the above scope.)
348
Hot gas circuit clogging
Faulty hot
Defective solenoid
gas bypass
valve coil
control
Defective solenoid
valve body
(∗1)
Defective control PC board
Subcooling
motor
[In cooling mode only]
operated
valve failure
Faulty
subcooling
motorized
Control
valve control
failure
(EV2)
(∗2)
4 way switch valve is in the
Faulty of 4 way
middle position.
switch valve
Leak from hot gas bypass
operation
valve
Superheat due to
shaft damage
Superheat due to
defective compressor
Defective valve coil
Indoor unit
motorized
valve failure
Defective valve body
Defective thermister for
indoor unit gas pipe
Faulty control
Defective thermister for
indoor unit liquid pipe
Defective control PC board
Defective valve coil
Outdoor unit
motorized
valve failure
Defective valve body
Defective low pressure
sensor
Defective thermister for
Faulty control
suction pipe
Defective control PC board
Irregular piping length
Bend/collapse
(Including moisture choke)
Stop valve is closed.
← Check if coil resistance and insulation
are normal.
← Check if coil resistance and
Defective valve coil
insulation are normal.
Defective valve
body
Defective low
← Check if the voltage property is
pressure sensor
normal.
Defective subcool
← Check if the connector is connected properly.
heat exchange
outlet thermister Check if the thermister resistance property
is normal.
Defective control
← Check if the pressure value given by the
PC board
service checker corresponding to actual
measurement value by the sensor.
← Check if the piping temperature connected
to the 4 way switch valve is normal.
← Check if coil resistance and insulation are
normal.
← Check if the connector is connected properly.
Check if the thermister resistance property is
normal.
← Check if the connector is connected properly.
Check if the thermister resistance property is
normal.
← Check if coil resistance and insulation are
normal.
← Check if the voltage property is normal.
← Check if the connector is connected properly.
Check if the thermister resistance property is normal.
← Check if the pressure value given by the
service checker corresponding to actual
measurement value by the sensor.
← Refer to [Check 7]
← Does the piping length fall in the permissible range?
← Corduet visual checks.
← Remove the moisture by vacuum break. (Refer to [Check 8])
← Check if the stop valve is open.
Discharge gas superheating temperature: 45 degrees
Si37-701
Troubleshooting