Maintenance Service and Trouble Shooting
b) Check the compressor accessories, including its thermal protector and relay. In
case the thermal protector is damaged, the compressor cannot be powered on. If the
relay is out of order, the motor will not run and hum sound can be heard from it after the
compressor is turned on, in that case, shut it down immediately, otherwise, the motor
windings will be burned out in case this condition lasts longer.
c) Check the relay contacts and plugs to see if they are perfect and work reliably. Poor
contact may cause the motor not running or humming.
2) Check the circuit voltage to see whether it is normal.
Analysis of trouble
If the circuit voltage is obviously lower than its rated value, it will be difficult to start the
motor, and a hum sound can be heard from it.
Remedy
Measure the voltage with a voltmeter; if it is really too low, give directions to the user for
buying a stabilizer so as to step up the voltage, thus normal operation can be achieved.
3) Check the thermal relay to see whether its contacts are closed.
Analysis of Trouble
The contacts of thermal relay sometimes may be open due to the leakage of
temperature sensing agent from the temperature sensor.
Remedy
Remove the relay cover to check up its contacts, if they are open, this means that the
original setting is not properly set or temperature sensing agent has leaked out of the
temperature sensor. Try to turn the adjusting stem of this value in the direction of the
lower temperature graduation, and then check the contacts to see whether they are
closed. If they are still not closed, dismantle the temperature sensing disc and then
immerse it into warm water to see whether the contacts actuate, if not, it can be
preliminarily determine that temperature sensing agent has leaked out, and it must be
replaced with a new thermostat.
4) Motor troubles and other electric faults
a) Motor windings have been burned or short-circuited between turns
Analysis of Trouble
When motor windings have been burned or short-circuited between turns, the fuse will
be blown repeatedly, and the blowout occurs particularly at the instant when you close
the knife switch.
Remedy
Check the terminals and the outer casing to see whether they are short-circuited, and
measure the resistance of each phase with an avometer. If short circuit occurs or the
resistance of a certain phase is low, this means that short circuit does exist in the
windings and/or between turns, and insulation layers have been burned or deteriorated.
A megameter can be used in this inspection, too. I f the insulation resistance
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