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ii)
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.
iii)
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.
b) 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 to step up the voltage, thus normal operation can be achieved.
c) 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 determined that temperature-sensing agent has leaked out, and it must be
replaced with a new thermostat.
d) Problems of motor and other electrical faults
i) Motor windings are damaged or there is a short circuited between turns
Analysis of Trouble
When motor windings are damaged or there the occurrence of a short circuit between
turns, the fuse will be blown repeatedly, and the blowout particularly occurs at that
instance where 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 particular phase is low, this means that there is no short circuit in the
windings and/or between turns, and that insulation layers are damaged or
deteriorated. Another instrument that can also be used in this inspection is a
