AS 3000 New requirements for earthing of slabs (Vic)

Changes to AS/NZS 3000, better known as the Wiring Rules has introduced new requirements for the earthing of conductive steel reinforcement within a concrete floor or wall that forms part of a shower or bathroom.

The Standard requires that any conductive reinforcement within a concrete floor or wall forming part of a bathroom must be connected to the earthing system to avoid any potential differences that could occur between conductive plumbing pipes that are connected to or in contact with the earthing system and the bathroom floor or wall.

The wording in the provision of the Standard does not accurately reflect the correct intent of the Standard and HIA has been able to clarify the true objective.

The intent of the regulation is to incorporate the concrete slab or wall into the earthing system in the event of an incident that will place an electrical current through the slab.  As the slab will generally incorporate a membrane that will isolate it from the ground this will not facilitate earthing if the slab becomes ‘live’. Also in this case the residual current device (RCD) or safety switch may not be triggered and cut the circuit if the slab was not connected to the earthing system.

A provision for connection to the earthing system will need to be installed at the concrete slab preparation stage via a suitable metal rod or wire connected to the slab reinforcement and left protruding from the slab to provide connection to the earthing system.

The Standard notes that if the reinforcement is tied together with steel tie wire and has a continuos bond over the entire slab or wall then the earthing point may be installed at any point that is most convenient.

On advice sought by HIA, Energy Safe Victoria, Victoria’s electrical regulator, has advised the installation can be carried out by the person preparing the concrete slab and does not need to be a licensed electrical contractor; the material used to provide the earthing point must be a suitably protected metal that will not degrade and cause damage to the earthing point or concrete slab.

Members should be aware however that the person who provides the connection will be taking responsibility for that connection and it would be prudent to engage a licensed electrical contractor to carry out this work. The earthing connection could be provided to the reinforcement prior to installation to assist with the scheduling of the works.

Members should note that although the revised Standard was published November 2007 the electrical regulator is allowing a transitional period; therefore the regulator will commence implementing the new requirement fully from 1 July 2008 . Energy Safe Victoria have advised that for jobs that have commenced after the Standard was published ( 12 November 2007 ) and will not be completed by 1 July an exemption for any electrical work that does not comply with the new requirements can be applied for.

For advice on how to apply for an exemption see the HIA information sheet headed ‘Wiring Rules Changes – Pre 1 July Exemptions’.

For further information HIA members can contact HIA’s Building Services staff on 1300 650 620 or hia_technical@hia.com.au.

Ref No. Vic BCA 08-05

The above is intended to provide general information in summary form. The contents do not constitute specific advice and should not be relied upon as such. Formal specific advice should be sought by members with respect to particular matters before taking action. ABN 99 004 631 752