Superheat Operation Check - Daikin RXYQ-TA Series Service Manual

Check
4.3

Superheat Operation Check

CHECK 3
Identify the defective points referring to the failure factor analysis (FTA) as follows.
Defective
discharge
pipe
temperature
control
Temperature
increase of
discharge
pipe
Compressor
overheat
In cooling
If the indoor unit
electronic
expansion valve is
throttled too much:
(∗3)
Defective
superheated
degree
control.
In heading
If the outdoor unit
electronic
expansion valve
excessively
throttled: (∗4)
Refrigerant
shortage
High pipe
resistance
∗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 is conducted by indoor unit electronic expansion
∗4. Superheating temperature control in heating is conducted by outdoor unit electronic expansion
293
Defective hot
gas bypass
control
(∗1)
In cooling only
Defective
subcooling
electronic
expansion
valve control
(∗2)
Defective four
way valve
operation
Superheat due to
shaft damage
Superheat due to
defective compressor
Defective indoor
unit electronic
expansion valve
Defective
control
Defective
outdoor unit
electronic
expansion valve
Defective
control
Abnormal piping length
Bent or crashed pipe
(Including moisture choke)
Stop valve closed.
valve.
valve (main).
Hot gas circuit clogging
Defective solenoid
← Are the coil resistance and insulation normal?
valve coil
Defective solenoid
valve body
Defective outdoor unit
main PCB
Defective valve coil
Defective
subcooling
Defective valve
electronic
body
expansion
valve Defective low
pressure sensor
Defective subcooling
Defective
heat exchanger outlet
control
thermistor
Defective outdoor
unit main PCB
Four way valve is in the
middle position.
Leak from hot gas bypass
valve
Defective valve coil
Defective valve body
Defective gas pipe
thermistor of indoor unit
Defective thermistor for
indoor unit liquid pipe
Defective outdoor unit
main PCB
Defective valve coil
Defective valve body
Defective low pressure
sensor
Defective suction pipe
thermistor
Defective outdoor unit
main PCB
← Does the piping length fall in the permissible range?
← Conduct visual checks.
← Eliminate moisture by vacuum operation. (Refer to
← Check if the stop valve is open.
← Are the coil resistance and
insulation normal?
← Are the electric characteristics normal?
← Is the connector properly connected?
Are the thermistor resistance characteristics
normal?
← Is the pressure value checked with the
Service Checker corresponding to the
measurement value of the pressure sensor?
← Check if the piping temperature connected
to the four way valve is normal.
← Are the coil resistance and insulation normal?
← Is the connector properly connected?
Are the thermistor resistance characteristics normal?
← Is the connector properly connected?
Are the thermistor resistance characteristics normal?
← Are the coil resistance and insulation normal?
← Are the electric characteristics normal?
← Is the connector properly connected?
Are the thermistor resistance characteristics normal?
← Is the pressure value checked with the Service
Checker corresponding to the measurement
value of the pressure sensor?
← Refer to
CHECK 7
SiUS341615E
CHECK 8 )
Service Diagnosis