EPC 30 - Verification

Question 1

Name the TWO main publications which specify the requirements for testing of domestic and non-domestic electrical installations in WA.

Answer 1

AS/NZS 3000 Wiring Rules and WA Electrical Requirements. (AS/NZS 3017).

Question 2

Who is responsible for testing a completed installation to ensure that it complies with all legislative requirements, and is safe to connect to the electrical supply?

Answer 2

The licensed electrical worker.

Question 3

List the SIX types of installation tests which must be completed before a single or three phase electrical installation can be regarded as safe to connect to the electrical supply.

Answer 3

a. Earth resistance.
b. Insulation resistance.
c. Polarity.
d. Correct circuit connections.
e. Verification of impedance
f. Operation of RCDs
AS/NZS 3000 Clause 8.3.3.

Question 4

Which Australian Standard contains specific guidelines and diagrams describing typical procedures for testing a completed MEN installation?

Answer 4

AS/NZS 3017 Electrical installations - Verification guidelines.

Question 5

Which Australian Standard relates to the requirements for installation and testing on Construction and Demolition Sites?

Answer 5

AS/NZS 3012.

Question 6

What is the maximum permissible resistance from the earthing electrode to the point where the main earthing conductor is connected to the main earthing terminal/connection or bar, in an MEN installation?

Answer 6

0.5 ohms

AS/NZS 3000 Clause 8.3.5.2 and 5.5.1.4.

Question 7

Why is it essential to disconnect the equipotential bonding conductor of a hot water system when checking the earthing conductor for continuity?

Answer 7

To avoid parallel connections through water pipes.

Question 8

What is the minimum permissible insulation resistance to earth in a single phase 230V installation which does not include an appliance with a sheathed heating element?

Answer 8

1 Mega Ohms.

AS/NZS 3000 Clause 8.3.6.3.

Question 9

What is the minimum permissible insulation resistance to earth in a single phase 230V installation which includes an appliance which incorporates a sheathed heating element?

Answer 9

0.01 Mega Ohms.
AS/NZS 3000 Clause 8.3.6.3.
See AS/NZS 3017 Clause 3.2.

Question 10

What additional action must be taken when measuring the insulation resistance to earth in circuits involving multiple switching such as two-way, three-way and master-on circuits?

Answer 10

All switches must be operated during the tests to ensure that all switch wires are tested.

Question 11

How must a single phase 10A socket outlet be polarised? (Give the Wiring Rules Clause
Number).

Answer 11

Earth active neutral in a clockwise direction. AS/NZS 3000 Clause 4.4.5.

Question 12

What fault would be indicated if a resistance of 0 ohms was obtained between the active and neutral tails in an installation without a supply connected?

Answer 12

There is a short circuit somewhere in the installation.

Question 13

What resistance would be expected when measuring the resistance of the heating element of a 230V, 4.8kW hot water system?

Answer 13

11.02 ohms;

4800/230 = 20.86A, then 230/20.86 = 11.02 ohms.

Question 14

Between which points in a typical domestic installation should the insulation resistance be measured? (Give the Wiring Rules Clause Number).

Answer 14

Between all live conductors and the earth Clause 8.3.6.1.

Question 15

At what voltage must the insulation resistance to earth be measured in a 400V three phase domestic installation?

Answer 15

500Vdc.

AS/NZS 3000 Clause 8.3.6.2.

Question 16

When testing insulation resistance to earth, should the circuit switches be on or off?

Answer 16

All switches must be on - otherwise the switch wires would not be included in the test.

Question 17

List the order in which electrical tests should be carried out in a typical new domestic
installation before the supply is connected.

Answer 17

1. Visual Inspection.
2. Resistance of main earth and circuit earth.
3. Insulation resistance of consumers’ mains and whole installation.
4. Polarity of mains. Polarity of switches, socket outlets, light switches.
5. Correct circuit connections. Active/neutral shorts.
6. Verification of earth fault loop impedance.
7. Operation of RCDs.

Question 18

Which Table in AS/NZS 3000 gives the maximum permissible values of total earth fault-loop impedance (Zs) in a 230V installation?

Answer 18

AS/NZS 3000 Table 8.1.

Question 19

Which Clause in AS/NZS 3000 gives a method of measuring fault-loop impedance with an instrument capable of measuring and indicating low values of impedance?

Answer 19

AS/NZS 3000 Clause 8.3.9.2.2.

Question 20

Which Clause in AS/NZS 3000 lists the mandatory (compulsory) tests which must be carried
out on electrical installations?

Answer 20

AS/NZS 3000 Clause 8.3.3.