Daikin VRV III-S RXYMQ36 48PVJU Service Manual page 225

CHECK 7
Check the Factors of Overheat Operation
Identify the defective points referring to the Fault Tree 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 Protection Control" for hot gas bypass control.
∗2:Refer to "Electronic Expansion Valve PI Control" for "subcooling electronic expansion valve control".
∗3:"Superheating temperature control" in cooling mode is conducted by indoor unit electronic expansion valve.
(Refer to "Electronic Expansion Valve Control")
∗4:Superheating temperature control in heating mode is conducted by outdoor unit electronic expansion valve (EVM).
(Refer to "Electronic Expansion Valve PI Control").
∗5:Judgement criteria of superheat operation:
N Suction gas superheating temperature: 18 degrees and over. O Discharge gas superheating temperature: 81 degrees and
over, except for immediately after starting and dropping control.
(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.)
216
Hot gas circuit clogging
Faulty hot
Defective solenoid
gas bypass
valve coil
control
Defective solenoid
valve body
(∗1)
Defective control PCB
Subcooling
motor
[In cooling mode only]
operated
valve failure
Faulty
subcooling
electronic
expansion valve Control
failure
control (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
electronic expansion
valve failure
Defective valve body
Defective thermistor for
indoor unit gas pipe
Faulty control
Defective thermistor for
indoor unit liquid pipe
Defective control PCB
Defective valve coil
Outdoor unit
electronic expansion
valve failure
Defective valve body
Defective low pressure
sensor
Defective thermistor for
Faulty control
suction pipe
Defective control PCB
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 subcooling
← Check if the connector is connected properly.
heat exchanger
outlet thermistor Check if the thermistor resistance property
is normal.
← Check if the pressure value given by the
Defective control
PCB
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 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 8
← 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.
SiUS34-907
CHECK 9 )
Troubleshooting