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ELECTRICAL ASPECTS
When proceeding with electrical fault finding ensure that you
have complied with all the safety requirements. Do not work
inside a live distribution board, do not earth yourself. You must
always follow the correct lock out procedures.
• Check if there is power on all phases at the incoming mains,
large distribution boards usually have a voltmeter and
selection switch, but if not, you will have to confirm utilising
test instruments.
• Check that phase rotation is correct (if the plant is rotating
in the wrong direction). This happens more often than one
would think. On an air-conditioning system, equipment runs
but does not work.
• Check whether a circuit breaker has tripped, or a fuse has
blown. If this is the case find the fault before resetting.
• The fault may be with a motor, perform a motor test and
look for signs of overheating.
The cause of
a fault could
be electrical or
mechanical.
60
By referring to the wiring diagram trace the motor starter
interlocks and control circuit. It may be ‘open circuit’ at the
lock-out stop, time switch, overload, remote stop/start or other
control interlock such as fire protection. Note: If the power has
been off for some time, the compressor crankcase heater may
RACA Journal I May 2020
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