Superheat Operation Check - Daikin VRV RXYMQ-A Series Service Manual

SiME332106E
6.3

Superheat Operation Check

CHECK 3 Referring to the Fault Tree Analysis (FTA) shown below, probe the defective points
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:
( 2)
Defective
superheating
degree
control.
[In heating]
If the outdoor unit
electronic
expansion valve
excessively
throttled: ( 3)
Refrigerant
shortage
High pipe
resistance
Note(s)
1. Refer to "Low pressure protection control" for hot gas bypass control.
2. "Superheating temperature control" in cooling is conducted by indoor unit electronic
3. Superheating temperature control in heating is conducted by outdoor unit electronic
Part 6 Service Diagnosis
Hot gas circuit clogging
Defective hot
Defective solenoid
gas bypass
valve coil
control
Defective solenoid
valve body
( 1)
Defective main PCB
Defective
subcooling
[In cooling only]
electronic
expansion
Defective
valve
subcooling
electronic
expansion Defective
control
valve control
Four way valve is in the
Defective four
middle position.
way valve
Leak from hot gas bypass
operation
valve
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.
expansion valve.
expansion valve (main).
m
Are the coil resistance and insulation normal?
Defective valve coil
Defective valve
body
m
Defective low
pressure sensor
Defective subcooling
m
heat exchanger outlet
thermistor
Defective main
mAre the voltage characteristics normal?
PCB
m
Check if the piping temperature connected
to the four way valve is normal.
Defective valve coil
m
Are the coil resistance and insulation normal?
Defective valve body
Defective gas pipe
m
Is the connector properly connected?
thermistor of indoor unit
Are the thermistor resistance characteristics normal?
Defective thermistor for
m
Is the connector properly connected?
indoor unit liquid pipe
Are the thermistor resistance characteristics normal?
Defective main
PCB
m
Are the coil resistance and insulation normal?
Defective valve coil
Defective valve body
m
Is the pressure value checked with the Service
Defective low pressure
Checker corresponding to the measurement
sensor
value of the pressure sensor?
Defective suction pipe
m
Is the connector properly connected?
thermistor
Are the thermistor resistance characteristics normal?
Defective main
mAre the voltage characteristics normal?
PCB
m
Refer to CHECK 7 .
m
Does the piping length fall in the permissible range?
m
Conduct visual checks.
m
Eliminate moisture by vacuum operation. (Refer to CHECK 8 .)
m
Check if the stop valve is open.
m
Are the coil resistance and
insulation normal?
Is the pressure value checked with the
Service Checker corresponding to the
measurement value of the pressure sensor?
Is the connector properly connected?
Are the thermistor resistance characteristics
normal?
Check
273