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Troubleshooting
SiBE811001EB
287
CONVENI-PACK
Check for Causes of Dropping Low Pressure (Refrigeration)
Referring to the Fault Tree Analysis (FTA) shown below, probe the defective points.
CHECK 2-2
←
Eliminate moisture by vacuum operation.
Defective suction air thermistor in the showcase
Inadequate refrigerant quantity
Moisture choke
Defective fan motor
Defective defrost
Dirty evaporator
Defective defrost heater
Dirty filter
Obstacle
Clogging of foreign particles
Stop valve closed
Bent or crashed pipe
Abnormal piping length
Defective control PCB
Defective control PCB
Defective valve coil
Defective valve body
Is the solenoid valve for R-410A?
Defective low pressure sensor
Defective control PCB
Short circuit
No air curtain is formed
Low outdoor air temperature
Defective low pressure sensor
Defective low pressure sensor
[In cooling]
Defective fan motor
Defective static superheated degree setup
Improper electronic expansion valve selection
Defective equalizing tube fitting
Defective valve body
Abnormally
low low-
pressure (Low
evaporating
temperature)
Defective
low pressure
control
←
Are the electrical characteristics
normal?
←
Is the pressure value checked with
the Service Checker
corresponding to the measurement
of the pressure sensor?
←
Are the electrical characteristics
normal?
←
Is the size of electronic expansion
valve appropriate?
←
Is the temperature difference
between the inlet and outlet of the
evaporator appropriate?
←
Are the coil resistance and
insulation normal?
←
Are the electrical characteristics
normal?
←
Discuss with the showcase
manufacturer
←
Does the piping length fall in the
permissible range?
←
Conduct visual checks for pipe
conditions.
←
Check to be sure the stop valve is
open.
←
Can the fan motor be
rotated with hands?
Are the motor coil resistance
and insulation normal?
←
Is the air filter clogged?
←
Is there any obstacle in the
air passage?
←
Is the defrost setup correct?
Is the orientation of the solenoid valve correct?
←
Is the heat exchanger clogged?
←
Is there any temperature
difference caused before and
after the filter or branch pipe?
←
Is the connector properly
connected?
Are the thermistor resistance
characteristics normal?
←
Is the pressure value checked with the
Service Checker corresponding to the
measurement of the pressure sensor?
[In cooling] Over
superheated
degree and low
capacity of the
electronic
expansion valve
in the showcase.
(See *3.)
Defective thermosensing
tube fitting position
Disengaged
thermosensing tube
[In cooling]
(See
∗
1.)
[For refrigeration]
(
∗
2.)
Defective
electronic
expansion
valve
control
Low suction air
temperature of
the evaporator
Less
circulation
quantity of
refrigerant
Degradation
in condensing
capacity
High air
passage
resistance
Decreased
fan airflow
rate
Decreased
fan output
Low suction air
temperature of
showcase
Defective
control
Defective
outdoor unit
electronic
expansion valve
Defective
control
Defective indoor
unit electronic
expansion valve
Defective low
pressure
protection control
Defective
compressor
capacity
control
High pipe
resistance
∗
1: For details of the compressor capacity control while in cooling, refer to “Compressor PI Control”.
∗
2: The “low pressure protection control” is used low pressure droop control.
∗
3: The expansion valve of the showcase is a mechanical expansion valve.