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WorksheetsElectrical Fault Diagnosis and Rectification
Total questions: 10
Worksheet time: 8mins
what is the first step of safe isolation
Identify the circuit
Isolate the circuit
Seek permission to Isolate
Lock of the supply
A customer reports their main RCD is constantly tripping. The most likely fault would be;
A Faulty appliance
Rodent damage to cables
To many appliances plugged in
Human error during installation
the correct instrument to check a circuit is dead is:
earth fault loop impedance tester
low resistance ohms meter
approved voltage indicator
insulation resistance tester
To check the resistance of cable insulation you would use:
An approved voltage indicator
Multi-meter
Insulation resistance tester
Low resistance ohmmeter
A customer has nailed through a cable whilst pitting up a picture. the correct rectification would be.
Renew the leg of cable completely and test the circuit
Joint the cable where the nail has penetrated the cable, and test
Remove the nail and hope for the best
Leave the nail in the cable and plaster over it.
An existing 4 year old 3 phase motor has started to run slowly when on load, its extremely loud and the bearings are satisfactory. The possible fault could be
One of the phase winding's have become open circuit
Their is a short circuit between 2 phase windings
The supply to the motor has been isolated
The bearings are too tight
A MICC cable has been installed underground to feed a fish pond in a garden center. The cable has failed and is causing the fuse to blow. The possible fault could be
too much load on the pond
the outer sheath has became damaged and penetrated the inner cores
too much voltage drop at the pond
the cable has reached its lifespan and decided to give up
A fluorescent light fitting has failed to strike and is flickering, the possible faults could be:
the supply voltage has dropped a little
the starter could be faulty
a short circuit fault is present on the supply circuit
the tube could be faulty
An immersion heater is causing water to over heat, the possible fault causing this could be:
the heater is drawing too much current
the thermostat is stuck in the on position
the heater is drawing too much voltage
the thermostat is stuck in the off position
A 13 amps socket supplying a 3kw heater has burnt contacts; which is the correct statement below
the socket should be taped up and changed at the next convenient opportunity.
sockets shouldn't be used to supply 3kw heaters, this should be changed immediately to a 20amp double pole switch
the socket isnt badly damaged therefore should be left alone until a major fault occurs.
change the socket immediately.
