Mains polarity verification testing

We’ve added two new how-to infographics to the Electrical Workers Toolbox(external link) that demonstrate safety verification polarity tests with the use of an independent earth probe.

The Multiple Earth Neutral (MEN) system we have in New Zealand is only safe if the polarities of both the supply system and the installation are correct and the connections of the neutral conductor are reliable.

The wiring rules AS/NZS 3000.2007 list the compulsory electrical tests required to be carried out on an installation, one of which is polarity testing on mains and submains.

Transposed conductors in the consumer mains or a disconnected main neutral to an electrical installation can create significant risks of shock or electrocution, and property damage through overheating and fire.

Polarity testing is absolutely critical and therefore must be independently verified by the installer, inspector, and person making a connection to an electricity supply.

The underlying principle of mains polarity testing is to carry out all the necessary tests and checks that will ensure the phase and neutral conductors are not transposed, and that the neutral is continuous and earthed.

Never liven mains to carry out live polarity testing unless correct polarity has first been proven. Failure to do so can create an immediate and serious risk of electrocution, shock, or fire should the mains conductors be transposed. The safety verification polarity test is only to be carried out after correct polarity was previously established. 

These tests and other practical guidance have been provided to assist electrical practitioners to achieve safe, compliant and competent electrical work, and to promote continued improvements in those areas.

Guidance on mains polarity testing is provided in standard AS/NZS 3017:2007 Electrical Installations – Verification Guidelines. This standard is freely available to all licensed practitioners through a RealMe login from the EWRB homepage.