Electrical safety on residential construction sites

What it is

Electrical safety on a residential construction site covers everything from the temporary builder's supply at the boundary through to the cordless drill being charged in the site shed. The standard that runs the construction phase is AS/NZS 3012 Electrical installations - Construction and demolition sites. The WHS Regulations through Part 4.7 set the legal duty for managing electrical risks, and the model Code of Practice "Managing electrical risks in the workplace" is the practical reference.

Residential builders carry duties even where the actual wiring work is done by a licensed electrical contractor. The PCBU controlling the site is responsible for the safe use of electricity by everyone on it.

The four classes of electrical work on a residential site

Permanent installation work

The fixed wiring of the home itself. Must be done by a licensed electrical contractor in every state and territory. Inspected and tested before energisation. Connected to the network by the distributor.

Temporary builder's supply

The temporary switchboard and supply used during the build. AS/NZS 3012 sets out the requirements. All final sub-circuits must be protected by a 30 mA residual current device (RCD). Inspection and testing is done by a licensed electrical worker before energisation and at intervals not exceeding six months on site.

Construction wiring and leads

Extension leads, portable RCDs, switchboards and temporary lighting on the site. AS/NZS 3012 requires RCD protection and regular inspection. Leads need visual checks before every use.

Plug-in electrical equipment

Powered hand tools, site lights, kettles in the shed. These must be inspected and tested at intervals set by AS/NZS 3012. On construction sites the standard interval is at least every three months.

RCD protection

Every final sub-circuit on a construction site has to be protected by an RCD with a maximum rated residual current of 30 mA that operates in all live conductors. This applies to the temporary switchboard and any portable distribution board.

The PCBU has to make sure RCDs are present and operating. The simple checks expected before each shift:

• Portable RCD push button test
• Switchboard fixed RCD test at intervals set by the standard
• Visual check that the RCD is correctly connected and not bypassed
• Replacement of any RCD that fails to trip on test

Inspection and testing intervals

AS/NZS 3012 sets the on-site intervals. For a residential construction site the practical schedule is:

• Construction wiring, switchboards and transportable structures: inspected and tested before energisation by a licensed electrical worker, then re-inspected at intervals not exceeding six months
• Plug and socket connected equipment used on site: at least every three months
• Portable RCDs: monthly push button test plus the longer interval test by a licensed person

Records of each test are kept with the equipment and made available to a WHS inspector on request. A test tag with the next test date is the normal evidence.

Working near overhead and underground services

A residential site often has live services running through it.

Overhead lines

The PCBU has to maintain no-go zones around overhead powerlines. The exclusion distances depend on the line voltage and the state. SafeWork NSW and WorkSafe Victoria both publish look-up tables. Scaffold, cranes, tipper trays and EWPs are the common contact risks.

Underground services

Before You Dig Australia plans must be obtained and the location of cables verified on site by potholing or non-destructive digging. Striking a live cable triggers an electrical incident notification under the WHS Regulations.

Who can do what

Licensing for electrical work is state based and strict. Only a licensed electrician can do fixed wiring, switchboard work or connection of electrical equipment by other than a plug. A builder cannot install a hardwired hot water unit or split system head unit. A handyman cannot replace a power point. The penalty regimes are state-run and serious.

Where residential builders get caught

Three patterns:

• Running power tools off a domestic power point in a partially energised house without an RCD in the circuit. AS/NZS 3012 RCD requirements apply to the construction phase regardless of the building's own wiring.
• Failing to keep test and tag records. The duty is on the PCBU using the equipment, not the test and tag contractor.
• Daisy-chaining leads and powerboards across a site. AS/NZS 3012 specifically restricts this and the practice is the leading cause of electrical incidents on AU construction sites.

Electrical incidents that involve a serious injury, fatality or dangerous incident must be notified to the WHS regulator immediately under Part 3 of the WHS Act.