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Fault Handling
Picture of real electronic expansion valve
B. Working principle of electronic expansion valve
The control principle of electronic expansion valve: The motor rotor uses permanent magnet. The rotor rotates based on the attracting or re
pelling effect generated by the magnetic pole of rotor and the magnetic pole of stator winding.
The coil (pulse motor) is controlled by control panel. The control command is sent from the main board and a pulse voltage is applied on the
motor stator winding which drives the rotor to operate. If a command with reverse signal sequence is sent, the motor will rotate reversely. In
this way, the pulse signal controls the up and down movement of valve rod, the opening of valve needle and the flow by adjusting the forward
and reverse rotation of the motor. The maximum and minimum opening of the valve is controlled by corresponding position limiting mechanism.
C. Common faults of electronic expansion valve
Common faults:
(1)
.
The coil lead is broken or the connector is loose.
(2)
.
The coil is not properly fit.
(3)
.
The coil is partly damaged, with abnormal resistance which causes invalid adjustment.
(4)
.
The main board of the air condition system is faulty, with output error.
(5)
.
The electronic expansion valve body is jammed by foreign objects which affect normal rotation.
(6)
.
There is leakage in the pipeline or body of electronic expansion valve.
(7)
.
Part of the rotor is jammed due to impact on electronic expansion valve body.
Connect to main
board interface
Electronic expansion
valve coil
Electronic expansion
valve body
Copper pipe interface
E. Compressor wear:
Compressor wear is usually caused by poor lubrication or solid foreign objects. Usually, we can identify compressor wear based on the status
of compressor oil. Normally, the compressor oil should be yellowish clear liquid. If the oil turns into reddish liquid, it means the compressor is
slightly worn but the operation is not affected. If the oil turns into black thick liquid with sediment, it means the compressor is seriously worn
and the oil is carbonized. In this case, user should replace the compressor, drain the oil and clean the system before refilling.
Long-term heavy duty operation can also cause the compressor wear due to high compression ratio.
2.Electronic expansion valve
The electronic expansion valve will adjust the flow of refrigerant based on system load to ensure the normal operation.
A. Basic structure of electronic expansion valve
The electronic expansion valve consists two parts: coil and valve body, as shown below:
c. The fan of the outdoor unit does not rotate or rotates at low speed due to reduced capacitance, or blocked air duct, or dirty heat exchanger
during heating can all cause incomplete evaporation of refrigerant and leads to liquid hammer;
d. Refrigerant migration: Insufficient warm up of heating belt under low temperature environment which causes refrigerant migrating into
gas-liquid separator and compressor and leads to liquid hammer;
e. Unsuitable superheat or too big valve opening can also cause liquid hammer.
