Oral Questions - Set 3 Flashcards
General questions (36 cards)
How would you test the earth continuity of a socket outlet situated 10 metres from the switchboard?
Use a running lead, measure it’s resistance and deduct this value from the earth continuity resistance.
How would you correctly test the value of a circuit for earth continuity?
Ensure the ohm scale was correctly zeroed.
If you had just added a socket outlet to an existing circuit would you test the resistance of the protective earth conductor of the circuit?
Yes
What is the maximum resistance of a 2.5mm2 protective earth conductor for a final sub-circuit protected by a 16A type “C” circuit breaker?
0.6Ω, AS/NZS3000:2018 Table 8.2
Why is it necessary to disconnect the equipotential bond when testing the continuity of the protective earth conductor of a hot water heater?
To avoid the parallel path between the protective earth conductor and the hot water system and the equipotential bond conductor.
Why do protective earth conductors require a low earth continuity reading?
To permit the flow of sufficient current to operate the circuit protective device.
Can you check the insulation resistance of a circuit with an ohmmeter?
No
If this were a live circuit would you test it with an insulation resistance tester on the MΩ range?
No
If you installed an extra socket outlet to a circuit would you test the insulation resistance of the circuit?
Yes
What voltage is required to conduct an insulation resistance test?
500V (+ 20%, - 10%)
What would you do if you discovered a 20kΩ insulation resistance reading to earth in the stove circuit of an installation?
Disconnect the stove from the fixed wiring and test the circuit again. If the reading was then 1MΩ or above the circuit would be allowable.
Why is it necessary to conduct the insulation resistance test twice when a two-way lighting circuit is installed?
Both switch wires (rock-overs, strappers) in the two-way circuit must be tested.
Why is it necessary to disconnect the MEN link when conducting an insulation resistance test?
To allow the insulation resistance test to be conducted between the neutral and earth conductors
How would you treat the load when testing the insulation resistance between the active and neutral of a final sub-circuit?
Disconnect the load from the circuit.
How would you treat control devices when conducting an insulation resistance test?
Place all control devices in a CLOSED position.
How would you treat circuit protective devices when conducting an insulation resistance test?
All protective devices must be placed in a close position.
Why can’t you use an ohmmeter to test insulation resistance?
The integrity of the insulation must be stressed by applying a direct current at 500V.
Is it necessary to test the insulation resistance of the consumer’s mains?
Yes
How would you treat the main switch when testing an installation?
If mains supply is connected to the building it must be placed in an open position, tag and lock-out main switch.
What would happen if the active and neutral conductors of an MEN installation where transposed at the consumer’s mains?
The earthing system would become live.
What would occur if the control device was connected in the neutral conductor of a final sub-circuit?
The equipment controlled by the device would appear dead but remain live.
How would you test for crossed neutrals?
With all neutrals connected to the link bar remove the neutral of the circuit you are testing and test to verify no continuity between the neutral link and the neutral in question.
Why is it necessary to disconnect the neutrals from each final sub-circuit when testing for correct circuit connections?
To ensure there are no crossed neutrals
How would you treat the resistance of the load when testing a final sub-circuit for correct circuit connections?
Disconnect the load and test for infinity ohms.
Calculate resistance of the load and test for the expected value.
