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Failure Diagnosis
Failure Diagnosis at the time of Discharge Gas Temperature Anomaly
When the discharge gas temperature goes up abnormally, compressor is stopped for protecting the compression
components of the compressor and discharge gas temperature anomaly alarm is generated at the same time.
In such a case, check the problem position and apply appropriate actions in the sequence shown below.
Checking the refrigeration cycle operation condition
□ (1) Isn't the refrigerant quantity insufficient ?
Refer to the "Adjusting Refrigerant Quantity of Refrigeration
Unit" in the "Adjustment during Operation."
□ (2) Isn't the suction gas temperature exceeding the limit (18°C)?
□ (3) Isn't the low pressure at 0.00MPa or below?
Compressor Operation Status Check
□ (1) Is the operation sound normal? (Metallic sound is higher when
abnormal)
□ (2) Is the operation current value normal?
□ (3) Is the cooling effect sufficient?
□ (4) Are any other anomalies detected?
Control Component Check
□ (1) Mounted condition of the discharge gas temperature sensor
Sensor body and connector on the control PCB
□ (2) Mounted condition of the electronic expansion valve (MOV7)
Valve coil and connector on the control PCB
Electronic expansion valve (MOV7) Operation Check
(1) Align the rotary switch (knob) with "Discharge (吐出)" and check
the discharge gas temperature of the compressor.
(2) Turn ON the DIP switch SW13-5 and set the rotary switch (knob)
to "Pressure (圧力)", and press the ▼/▲ buttons to make the
electronic expansion valve opening to 450 steps.
DIP switch SW13
(3) Set the rotary switch (knob) back to "Operation (運転)".
(4) Turn OFF the DIP switch SW13-5 and set the rotary switch (knob)
to "Discharge (吐出)", and check if the compressor discharge gas
temperature gradually goes down.
(5) Turn ON the DIP switch SW13-5 and set the rotary switch (knob)
to "Pressure (圧力), and press the ▼ ▲ buttons to make the
digital display indicate "7.oFF", and then align the rotary switch
(knob) back to "Operation (運転)".
This operation returns the electronic expansion valve (MOV7) to
automatic control.
Caution
Before checking the electronic expansion valve operation, if the valve
has been operating with a full opening (480 steps), discharge gas
temperature does not change. Wait for some time and then check.
If the electronic expansion valve is fully open, then refrigerant pipe
clogging is the possible cause.
All normal
<Digital display example>
Electronic expansion valve opening (E.g.: 450step)
Electrical box
Flash chamber
Electronic expansion
valve for liquid return
(MOV7)
Back of refrigeration unit
44
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