Service Manual

SiUS281811E Check
Part 6 Service Diagnosis 261
5. Check
5.1 High Pressure Check
CHECK 1 Referring to the Fault Tree Analysis (FTA) shown below, probe the defective points.
1: In cooling, it is normal if the outdoor unit electronic expansion valve is fully open.
2: In heating, the indoor unit electronic expansion valve is used for subcooling degree control.
Short circuit
Rise in high
pressure
Local
pressure
rise
High pipe
resistance
Stop valve closed
Bent or crushed pipe
Clogging of foreign
materials
[In cooling]
If the outdoor unit electronic
expansion valve is throttled:
(*1.)
Defective outdoor
unit electronic
expansion valve
Defective indoor
unit electronic
expansion valve
Defective valve coil
Defective valve body
A temperature difference in
excess of 10°C (18°F) between
the inlet and the outlet is
deemed to be abnormal.
Defective
control
Defective high pressure sensor
Defective main
PCB
Defective
high pressure
control
Defective valve coil
Defective valve body
[In heating]
If the indoor unit electronic
expansion valve excessively
throttled:
(*2.)
Defective
control
Defective high pressure sensor
Defective indoor unit
liquid pipe thermistor
Defective main
PCB
[In cooling]
High suction
air
temperature
of the
condenser
[In heating]
High suction air
temperature of
outdoor unit
Short circuit
High outdoor air
temperature
High suction
air temperature
of indoor unit
High room
temperature
Defective suction air thermistor of indoor unit
High suction air temperature of outdoor unit
Defective outdoor air temperature thermistor of outdoor unit
Degradation
in condensing
capacity
Dirty condenser
Mixing of non-condensable gas
Decreased
airflow rate
Decreased
fan
output
Defective fan
motor
Defective main
PCB (Including
capacity setting)
High
airflow
passage
resistance
Dirty filter
Obstacle
Excessive refrigerant charging
Improper model selection
[In heating]
←
Check to be sure the stop valve is open.
←Conduct visual checks for pipe conditions.
←Is there any temperature difference caused before
and after the filter or branch pipe?
←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?
←Are the voltage characteristics normal?
←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?
←Is the room temperature more than 27°C (80.6°F)?
←Is the connector properly connected?
Are the thermistor resistance characteristics normal?
←Is the outdoor air temperature more than 16°CWB
(60.8°FWB)?
←Is the connector properly connected?
Are the thermistor resistance characteristics normal?
←Is the heat exchanger clogged? (In cooling)
←Is air or else mixed in the refrigerant system?
←Can the fan motor be rotated with hands?
Are the motor coil resistance and
insulation normal?
←If a spare PCB is installed, is the capacity
setting properly made?
←Is the air filter clogged?
←Is there any obstacle in the airflow passage?
←Refer to CHECK 6 .
←Is the indoor unit too small compared to
the large-sized outdoor unit?
←Is the suction air temperature more than 43°C
(109°F)?
←Is the outdoor air temperature more than 43°C
(109°F)?
←Is the suction air temperature more than 27°C
(80.6°F)?