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SiUS341615E
Check
Service Diagnosis
292
4.2
Low Pressure Check
Referring to the Fault Tree Analysis (FTA) shown below, probe the defective points.
Note:
∗
1. For details of compressor capacity control while in cooling.
∗
2. The “low pressure protection control” includes low pressure protection control and hot gas
bypass control.
∗
3. In cooling, the indoor unit electronic expansion valve is used for “superheated degree control”.
CHECK 2
Abnormally drooping
low pressure
(Low evaporating
temperature)
In cooling
(
∗
1)
Defective
low pressure
control
Defective
compressor
capacity
control
Defective low pressure
sensor
Defective outdoor
unit main PCB
Defective
low pressure
protection
control
Defective low pressure
sensor
Defective hot gas
solenoid valve
Defective outdoor
unit main PCB
In both cooling
and heating
(
∗
2)
In cooling
If the indoor unit
electronic
expansion valve is
throttled too much:
(
∗
3)
Defective indoor
unit electronic
expansion valve
Defective valve coil
Defective valve body
Defective
control
Defective gas pipe
thermistor of indoor unit
Defective liquid pipe
thermistor of indoor unit
Defective outdoor
unit main PCB
In cooling
Low suction air
temperature of
the evaporator
Low suction air
temperature of
indoor unit
Short circuit
Low room temperature
Defective suction air thermistor of indoor unit
High pipe
resistance
Abnormal piping length
Bent or crashed pipe
Clogging of foreign materials
Stop valve closed
Less
circulation
quantity of
refrigerant
Degradation
in condensing
capacity
Refrigerant shortage
Moisture choke
Dirty
evaporator
Decreased
airflow rate
Decreased
fan output
Defective fan motor
←
Can the fan motor be rotated with hands?
Are the motor coil resistance and insulation normal?
←
If a spare PCB is mounted, is the
capacity setting properly made?
←
Is the air filter clogged?
←
Is there any obstacle in the airflow passage?
Defective outdoor unit main
PCB (Including capacity setting)
High
airflow
passage
resistance
Dirty filter
Obstacle
Defective electronic
expansion valve
control
←
Are the electrical characteristics normal?
←
Is the pressure value checked with the Service Checker
corresponding to the measurement value of the pressure sensor?
←
Are the electrical 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?
←
Are the coil resistance and insulation normal?
←
Check for the thermistor resistance and connection.
←
Check for the thermistor resistance and connection.
←
Is the pressure value checked with the Service Checker
corresponding to the measurement value of the pressure sensor?
←
Is the suction air temperature more than 14˚C (57.2˚F)?
←
Is the room temperature less than 14˚C (57.2˚F)?
←
Is the connector properly connected?
Are the thermistor resistance characteristics normal?
←
Does the piping length fall in the permissible range?
←
Conduct visual checks for pipe conditions.
←
Is there any temperature difference caused before
and after the filter or branch pipe?
←
Refer to
←
Eliminate moisture by vacuum operation.
←
Is the heat exchanger clogged?
CHECK 7
Содержание RXYQ-TA Series
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Страница 336: ...Revision History Month Year Version Revised contents 02 2017 SiUS341615E First edition...