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SiENBE28-901
Troubleshooting
Air Cooled Refrigeration Condensing Unit
131
[Check 2] Check for Causes of Drop in Low Pressure
Referring to the Fault Tree Analysis (FTA) shown below, identify faulty points.
Low pressure
is too low.
(Evaporating
temp. is low)
[In cooling]
If the indoor unit
electronic expansion
valve is excessively
throttled:
(See
∗
3)
←
Are the voltage characteristics normal?
Faulty low
pressure
control
(
∗
1)
(
∗
2)
Faulty
compressor
capacity
control
Faulty low
pressure
protection
control
Faulty indoor
unit electronic
expansion valve
Faulty
control
Faulty
electronic
expansion
valve control
[In defrosting]
If the outdoor unit
electronic expansion
valve is excessively
throttled:
(See
∗
4)
Faulty outdoor unit
electronic
expansion valve
Faulty
control
Suction air
temperature
of the indoor
unit too low
Faulty indoor unit suction air thermistor
Suction air
temperature of
the evaporator
too low
High piping
resistance
Low
refrigerant
circulation
rate
Degradation in
evaporating
capacity
Refrigerant shortage
Moisture choke
Dirty evaporator
Drop in
fan air
volume
Faulty low pressure sensor
Faulty outdoor unit main PCB
Faulty low pressure sensor
Faulty outdoor unit main PCB
Faulty valve coil
Faulty valve body
Faulty indoor unit
gas pipe thermistor
Faulty indoor unit
liquid pipe thermistor
Faulty outdoor unit main PCB
Faulty valve coil
Faulty valve body
Faulty low pressure sensor
Faulty suction pipe thermistor
Faulty outdoor unit main PCB
Short circuit
Low ambient temp.
Abnormal piping length
Bended or crushed pipe
Clogged piping due to
foreign matters
Stop valve closed
Drop in
fan
output
High air
duct
resistance
Faulty fan motor
Dirty filter
Faulty outdoor unit main PCB
(including capacity setting)
Obstacles
←
Is the pressure value on the Service Checker
matched to the measurement of sensor?
←
Are the voltage characteristics normal?
←
Is the pressure value on the Service Checker
matched to the measurement of sensor?
←
Is the coil resistance and the insulation normal?
←
Check for thermistor resistance
and connector connection.
←
Check for thermistor resistance
and connector connection.
←
Is the pressure value on the Service Checker
matched to the measurement of sensor?
←
Is the coil resistance and the insulation normal?
←
Are the voltage characteristics normal?
←
Check for thermistor resistance
and connector connection.
←
Does the suction air temps. fall in the "continuous
operation range of inside temperature"?
←
Does the inside temps. fall in the
"continuous operation range"?
←
Is the connector properly connected?
Are the thermistor resistance characteristics
normal?
←
Does the piping length fall in the permissible
range?
←
Visual check
←
Check for any temp. difference before and after
filter or branch piping.
←
Check to be sure that the stop valve is open.
←
See [Check 6].
←
Remove moisture by vacuum drying.
←
Does the heat exchanger get clogged?
←
Can the fan motor be rotated by hand?
Is the resistance and insulation of motor coil normal?
←
Is the capacity setting of spare PCB
correct, if used?
←
Does the air filter get clogged?
←
Is there any obstacle in the air duct?
∗
1. For the compressor capacity control in cooling, refer to information in "Compressor Control".
∗
2. "Low pressure protection control" includes low pressure drooping control.
∗
3. The indoor unit electronic expansion valve exerts "superheated degree control" in cooling.
∗
4. The outdoor unit electronic expansion valve (EV1) exerts "superheated degree control of outdoor unit heat exchanger" in defrosting.