Daikin VRV-WIII RWEYQ72PTJU Service Manual page 251

SiUS30-1301
CHECK 3
Check the Factors of Overheat Operation
Identify the defective points referring to the defective factor analysis (FTA) as follows.
Defective
discharge
pipe
temperature
control
Temperature
increase of
discharge
pipe
Compressor
overheat
[In cooling mode]
If the indoor unit
electronic
expansion valve
is excessively
throttled. (3)
Defective
superheated
degree
control.
Refrigerant
shortage
Large resistance
of piping
1: Refer to "Low pressure protection control" for hot gas bypass control.
Note:
2: Refer to "Subcooling electronic expansion valve control".
3: "Superheating temperature control" in cooling mode is conducted by indoor unit electronic expansion valve.
4: Superheating temperature control in heating mode is conducted by condensing unit electronic expansion valve
5: Judgement criteria of superheat operation:
Service Diagnosis
Defective hot
gas bypass
control
(1)
[In cooling mode only]
Defective
subcooling
electronic
expansion valve
control
(2)
Defective of
four way valve
operation
Superheat due to
shaft damage
Superheat due to
defective compressor
Indoor unit
electronic expansion
valve failure
Defective control
Condensing unit
electronic expansion
valve failure
[In heading
mode] If the
condensing unit
electronic
Defective control
expansion valve
is excessively
throttled. (4)
Irregular piping length
Bend/collapse
(Including moisture choke)
Stop valve is closed.
(EVM).
(1) Suction gas superheating temperature: 10 degrees and over. (2) Discharge gas superheating temperature: 45
degrees 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.)
Troubleshooting by Indication on the Remote Controller
Hot gas circuit clogging
Defective solenoid
 Check if coil resistance and insulation
valve coil
are normal.
Defective solenoid
valve body
Defective control PCB
Defective valve coil
Subcooling
electronic
Defective valve
expansion
body
valve failure
Defective low
pressure sensor
Defective subcooling
Control
heat exchanger outlet
failure
thermistor
Defective control
PCB
Four way valve is in the
middle position.
Leak from hot gas bypass
valve
Defective valve coil
Defective valve body
Defective thermistor for
indoor unit gas pipe
Defective thermistor for
indoor unit liquid pipe
Defective control PCB
Defective valve coil
Defective valve body
Defective low pressure
sensor
Defective thermistor for
suction pipe
Defective control PCB
 Does the piping length fall in the permissible range?
 Conduct visual checks.
 Remove the moisture by vacuum break. (Refer to
 Check if the stop valve is open.
 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 thermistor resistance property is
normal.
 Check if the pressure value given by the
service checker corresponding to actual
measurement value by the sensor.
 Check if the piping temperature connected
to the four way valve is normal.
 Check if coil resistance and insulation are
normal.
 Check if the connector is connected properly.
Check if the thermistor resistance property is
normal.
 Check if the connector is connected properly.
Check if the thermistor 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 thermistor 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
)
CHECK 8
243