Daikin RXYQ96PYDN Service Manual page 475

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.
Temperature
increase of
discharge
pipe
∗1: Refer to "Low pressure protection control" (P66, 213) for hot gas bypass control.
∗2: Refer to P47, 195 for 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 outdoor unit electronic expansion valve (EVM).
(Refer to P47, 195).
∗5: Judgment criteria of superheat operation:
(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.)
460
Faulty hot
gas bypass
control
(∗1)
Faulty
[In cooling mode only]
discharge
pipe Faulty
temperature subcooling
control motorized
valve control
(EV2)
(∗2)
Faulty of 4 way
switch valve
operation
Superheat due to
shaft damage
Compressor
overheat
Superheat due to
defective compressor
Indoor unit
motorized
valve failure
[In cooling mode]
When indoor unit
electronic
expansion valve
becomes too
Faulty control
narrow (∗3)
Faulty
superheated
degree
control.
Outdoor unit
motorized
valve failure
[In heading
mode]When
outdoor unit
electronic
Faulty control
expansion valve
becomes too
narrow (∗4)
Refrigerant gas
shortage
Irregular piping length
Bend/collapse
Large resistance
(Including moisture choke)
of piping
Stop valve is closed.
Suction gas superheating temperature: 18 degrees and over.
and over, except for immediately after starting and drooping control, etc..
Hot gas circuit clogging
Defective solenoid
← Check if coil resistance and insulation
valve coil
are normal.
Defective solenoid
valve body
Defective control PC board
Defective valve coil
Subcooling
Defective valve
motor
body
operated
valve failure
Defective low
pressure sensor
Defective subcool
Control
heat exchange
failure
outlet thermister
Defective control
PC board
4 way switch valve is in the
middle position.
Leak from hot gas bypass
valve
Defective valve coil
Defective valve body
Defective thermister for
indoor unit gas pipe
Defective thermister for
indoor unit liquid pipe
Defective control PC board
Defective valve coil
Defective valve body
Defective low pressure
sensor
Defective thermister for
suction pipe
← Check if the pressure value given by the
Defective control PC board
← 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: 81 degrees
SiUS34-801A_b
← 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.
← 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.
service checker corresponding to actual
measurement value by the sensor.
← Refer to [Check 7]
Troubleshooting