Electrical Fault Finding 6

To ensure any test instrument is fit for purpose, it should be

• Calibrated every month

• Tested every 6 months

• Replaced every 12 months

• Checked every time it is used

Answer explanation

To ensure any test instrument is fit for purpose, it should be checked every time it is used, not just periodically calibrated, tested, or replaced.

The instrument used to determine the ability of a protective device to function after a fault is

• An approved continuity tester

• A PFC tester

• An insulation resistance tester

• An EFLI tester

Answer explanation

Fuses can be checked with Continuity tester.

A 30mA RCD is tested and suspected of being faulty. When a current of 5 times IΔn is used to test it, the device should operate within

• 15 ms

• 30 ms

• 40 ms

• 300 ms

Answer explanation

When testing a 30mA RCD suspected of being faulty, it should operate within 40 ms when a current of 5 times IΔn is used, making the correct answer choice 40 ms.

A fault has been reported on a piece of equipment. To assist with fault location, why is it worthwhile checking previous maintenance records?

• They will explain how the equipment works

• They may include up to date circuit diagrams

• They will identify how often the equipment is maintained

• They may identify a similar fault or gradual deterioration.

Answer explanation

Checking previous maintenance records may identify a similar fault or gradual deterioration, aiding in fault location.

For fault diagnosis, collection and analysis of data may involve

• Contacting the council

• Contacting the Health and Safety Executive

• Talking to users

• Contacting building control

Answer explanation

For fault diagnosis, talking to users is essential as they can provide valuable information about the issue and its history, aiding in the collection and analysis of data.

Which dangerous gas is emitted from lead acid cells?

• Helium

• Nitrogen

• Oxygen

• Hydrogen

Answer explanation

Hydrogen is the dangerous gas emitted from lead acid cells.

When carrying out insulation resistance testing, to prevent damage to equipment the tester must ensure that

• All incandescent bulbs must be removed

• All electronic equipment is disconnected

• All motor isolators are turned off

• All heating elements are turned off

Answer explanation

When carrying out insulation resistance testing, to prevent damage to equipment the tester must ensure that all electronic equipment is disconnected.

When working with fibre optic cables, a special precaution that must be taken is it

• Never get them wet

• Ensure total cleanliness of joints

• Avoid touching the outer sheath of the fibre strands

• Avoid exposure to sunlight

Answer explanation

Ensure total cleanliness of joints

Which of these is a suitable test procedure to prove the operation of an RCD, when using an RCD tester?

• Test between the line conductor of the protected circuit, and the associated CPC. The load should be disconnected during the test.

• Test between the live conductor and the circuit protective conductor. The main switch should be off

• Test between the line and neural conductors connected together, and earth at the consumer unit. The load should be disconnected during the test.

• Test between live conductors. The test should be carried out with the main switch off, all fuses in place or MCB's turned on and any lamps removed.

Answer explanation

Test between the line conductor of the protected circuit, and the associated CPC. The load should be disconnected during the test.

Twin and earth, PVC cables are restricted to maximum operating temperatures of

• 80°C

• 50°C

• 70°C

• 60°C

Answer explanation

Twin and earth, PVC cables are restricted to a maximum operating temperature of 70°C.