Daikin RTSQ20PY1 Service Manual page 351

SiBE31-801_C
CHECK 3
Check the Factors of Overheat Operation
Referring to the Fault Tree Analysis (FTA) shown below, probe the faulty points.
Faulty
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)
Faulty
superheated
degree
control.
[In heading
mode] If the
outdoor unit
electronic
expansion valve
is excessively
throttled. (∗4)
Refrigerant gas
shortage
Large resistance
of piping
∗1: Refer to "Low pressure protection control" (P.100) for hot gas bypass control.
∗2: Refer to P.94 for subcooling electronic expansion valve control.
∗3: "Superheating temperature control" in cooling mode is conducted by indoor unit electronic expansion valve.(Refer to P.127)
∗4: Superheating temperature control in heating mode is conducted by outdoor unit electronic expansion valve (EVM).
(Refer to P.94).
∗5: Judgement criteria of superheat operation:
(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
Hot gas circuit clogging
Faulty hot
Defective solenoid
gas bypass
valve coil
control
Defective solenoid
valve body
(∗1)
Defective control PCB
Subcooling
electronic
[In cooling mode only]
expansion
valve failure
Faulty
subcooling
electronic
expansion valve Control
failure
control (EVT)
(∗2)
Four way valve is in the
Faulty of four
middle position.
way 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.
Troubleshooting (Heat Reclaim Ventilation)
← Check if coil resistance and insulation
are normal.
Defective valve coil
← Check if coil resistance and
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
Check if the thermistor resistance
thermistor
property is normal.
Defective control
← Check if the pressure value given by the
PCB
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 12
← 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 13
340