Switchboards and Earthing
[ Last Updated 27 March 2006 ]
Switchboards
Q. What are the requirements for distribution switchboard neutral to earth linking for existing switchboards post January 2003?
A. Neutral to earth linking of existing distribution switchboards (see AS/NZS 3000 clause 1.4.38 for switchboard definition) installed prior to January 2003 may remain.
Q. What are the requirements for distribution switchboard neutral to earth linking for new switchboards post January 2003?
A. For installations using AS/NZS 3000 as a means of compliance, distribution switchboard neutral to earth linking is not permitted. Note that the main (MEN) switchboard MUST have a link.
Q. For distribution switchboards when should an existing neutral to earth link be removed?
A. Neutral to earth linking on distribution switchboards installed prior to January 2003 may remain. Removal of the earth link is to prevent neutral currents flowing in the submain earth conductor.
Earthing
Q. Does the connection of the main earth conductor to the earth bar still have to be to a stud or under two screws?
A. Yes. However, one screw may be used if the outside diameter of the screw is not less than 80% of the tunnel diameter or the conductor is clamped by a ferrule or plates in direct contact with the conductor. Refer to clause 2.9.3 of AS/NZS 3000.
Q. Are the earth electrodes in AS/NZS 3000 Section 5 able to be used in New Zealand?
A. No, regulation 86 details the type of earth electrodes to be used.
Q. When a ceiling light is replaced with a metal light in an existing domestic electrical installation, does that light have to be earthed?
A. Yes, if there is an earth present. If however, as is common in older installations where the lights were wired in two core, it is in a dry situation, the light is above door height and earthed metal is not in close proximity (2.5 m), then the answer is no. Another acceptable solution is to protect the circuit with an RCD.
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