Superheat Operation Check - Daikin REYQ-XA Service Manual

SiUS371901E
4.3

Superheat Operation Check

CHECK 3
Referring to the Fault Tree Analysis (FTA) shown below, probe the defective points.
Temperature
increase of
discharge
pipe
∗1: Refer to Low pressure protection control for hot gas bypass control.
Notes:
∗2: Superheating temperature control in cooling is conducted by indoor unit electronic expansion valve.
∗3: Superheating temperature control in heating is conducted by outdoor unit electronic expansion
∗4: Judgment criteria of superheat operation:
Service Diagnosis
Defective hot
gas bypass
control
(∗1)
Defective
[In cooling only]
discharge
pipe Defective
temperature injection
control electronic
expansion
valve control
Defective four
way valve
operation
Superheat due to
shaft damage
Compressor
overheat
Superheat due to
defective compressor
Defective indoor
unit electronic
expansion valve
[In cooling]
If the indoor unit
electronic
expansion valve is
throttled too much:
Defective
(∗2)
control
Defective
superheating
degree
control.
Defective
outdoor unit
electronic
expansion valve
[In heating]
If the outdoor unit
electronic
Defective
expansion valve
control
excessively
throttled: (∗3)
Refrigerant
shortage
Abnormal piping length
Bent or crashed pipe
High pipe
(Including moisture choke)
resistance
Stop valve closed.
valve (main).
(1) Suction gas superheating degree: 10°C (18°F) and over. (2) Discharge gas superheating
degree: 45°C (81°F) and over, except immediately after compressor starts up or is running under
dropping control.
(Use the above values as a guide. Depending on the other conditions, the unit may be normal
despite the values within the above range.)
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
injection
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
← Check if the piping temperature connected
middle position.
Leak from hot gas bypass
valve
← Are the coil resistance and insulation normal?
Defective valve coil
Defective valve body
Defective thermistor for
← Is the connector properly connected?
indoor unit gas pipe
Defective thermistor for
← Is the connector properly connected?
indoor unit liquid pipe
Defective indoor
unit control PCB
← Are the coil resistance and insulation normal?
Defective valve coil
Defective valve body
← Is the pressure value checked with the Service
Defective low pressure
sensor
Defective suction pipe
← Is the connector properly connected?
thermistor
Defective outdoor
←
unit main PCB
← Refer to
← 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?
← 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?
←
Are the voltage characteristics normal?
to the four way valve is normal.
Are the thermistor resistance characteristics normal?
Are the thermistor resistance characteristics normal?
Checker corresponding to the measurement
value of the pressure sensor?
Are the thermistor resistance characteristics normal?
Are the voltage characteristics normal?
CHECK 7 .
CHECK 8
Check
.)
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