Issue 136 January - February 2020

efore electrical work was codified into law many years ago, the risks to public safety were managed through controls exerted by power utility monopolies and insurance companies. The insurance industry was well-practised at managing risk and placing a monetary value on each type of risk that had to be addressed for insurance cover to be provided. Insurance companies set wiring rules that electrical workers had to follow to get insurance cover and, without cover, no work could be done.

The electrical safety work methods that were initially established by insurance companies have long since been replaced by prescriptive controls set in legislation. However, in 2010, new Electricity (Safety) Regulations were issued that made it clear that risk management was still the driver of legislated controls. These prescriptive controls are created internationally and locally and brought into effect by regulation and cited standards.

An amendment to the Electricity Regulations in 2013 introduced a stepped approach to managing electrical safety risks that occur in prescribed electrical work (PEW) in different types of installations. Five levels are now applied to all electrical installation work and three of these are expressed in Regulation 6A: low-risk, general, and high-risk PEW.

The management of retentions under the Construction Contracts Act has been in place for over two years with mixed results. Former Master Electricians board member and director of Team Cabling, Dave Burt, is currently representing creditors in the liquidation of a building company. He comments on changes needed to improve the legislation.

In the March – April 2013 edition of the ElectroLink magazine exists an article titled, ‘What will the legacy of the Mainzeal collapse be for sub-contractors’. It’s an excellent article by Craig Black that succinctly details retentions for the uninitiated; and I will touch on some of its more poignant points later because they are just as relevant today.

Given the recent history of the time, it was a very fair question. I recall that period well. I was one of many that donated my retention monies to the Mainzeal pot of funds that is still being squabbled over today. The only thing I knew for sure was, as an unsecured creditor, my money was gone for all time. I must be quite a generous bloke because I have subsequently donated more to other main contractors in recent times.

During many years working in the petrochemical and dairy industries and running his own contracting and manufacturing business, electrical inspector Athol Gibson gained a lot of insight into the effects of stray voltages and power quality problems. Following the introduction of electric vehicles, he comments on alternatives to MEN to overcome safety and supply issues.

The New Zealand low voltage electrical system of supply and connection to earth is based on the European TN-C-S earthing design. It has been used in New Zealand for approximately 90 years. The transformer neutral is connected to an earth electrode. The installation neutral and earth bars are linked, with the earth bar connected to a separate earth electrode. It requires integrity of the earth electrode to maintain the neutral at earth potential. (See diagram A)

It has been successful as a system of supply. It is particularly suited to the rural scene where there are long runs of low voltage reticulated supply and only a few consumers from each transformer.