EPC 17 - The MEN System of Earthing

Question 1

Under the multiple earthed neutral (MEN) system, the main earthing terminal/connection is required to be connected to the neutral bar or link. At what point on the neutral bar or link should the connection be made? (Give the Wiring Rules Clause Number).

Answer 1

At one extremity of the bar or link (usually the left). The main neutral should occupy the next adjacent terminal. AS/NZS 3000 Clause 2.10.5.4 Exception 1 and 2.

Question 2

What is an ‘MEN link’ or ‘MEN connection’, and where is it located? (Give the Wiring Rules
Clause Number).

Answer 2

A connection or link between the main earthing terminal/connection or bar, to the earthing terminal
on the neutral link. AS/NZS 3000 Clause 5.3.5. It is located on the main switchboard.

Question 3

What is the only permissible colour for the insulation on an MEN link? (Give the Wiring Rules
Clause Number).

Answer 3

Green/yellow.

AS/NZS 3000 Clause 5.3.5.3.

Question 4

What is the minimum permissible size of the MEN link if the consumer’s mains is not protected on the supply side by a short circuit protective device? (Give the Wiring Rules ClauseNumber).

Answer 4

The same size as the main neutral conductor.

Question 5

Is it permissible to install an MEN link at a distribution board in an outbuilding which is detached from the main building? (Give the Wiring Rules Clause Number).

Answer 5

Yes. AS/NZS 3000 Clause.5.5.3.1 (C)

Question 6

What potentially hazardous situation can arise if the MEN link is not connected correctly in an
MEN installation?

Answer 6

a. The resistance of the fault current path may be too high to allow the circuit protection device to operate correctly.
b. An unexpected voltage may occur at a device under fault conditions.

Question 7

An installation with an MEN earthing system develops a fault that results in a person receiving an electric shock from metal water pipes. What is the most likely cause?

Answer 7

An open circuit or high resistance in the main neutral conductor.

Question 8

Which clause in AS/NZS 3000 describes the parts of the earth fault loop in an installation?

Answer 8

1. PE (protective earth)
2. Main Earth Bar
3. MEN link
4. Main Neutral Bar
5. PEN (protective earth neutral)
6. Transformer Winding
7. Consumer Mains Active
8. Final SubCircuit Active
   Clause B4.4 and Figure B5. or 5.7.3 (a-d)