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Existing wiring dangers at construction and demolition sites

Workers have received serious electric shocks on sites where existing wiring has been damaged during construction or demolition activities. In several of these instances the wiring was either not identified or not correctly isolated from the electricity supply before the work was carried out.

Any wiring located where construction or demolition work is planned must be considered to be energised until proven otherwise by inspection and testing. The wiring must be identified and the risk of mechanical damage from the construction activities assessed. If it's determined that there is a risk of mechanical damage, the wiring must be suitably protected.

In some situations electrical circuits controlled by photoelectric (PE) cells or timers have not been isolated correctly, resulting in electric shocks. PE cells or timers are typically used to energise lighting circuits as natural light fades.

When the PE cell or timer is off, it does not supply electricity to the circuit. Without adequate isolation, these circuits can become energised at different times, creating a significant electrical risk during construction and demolition work. When testing whether existing wiring is isolated, an electrical contractor should also determine whether there are any circuits controlled via PE cells or timers and isolate them at the same time.

More information

For further information refer to AS/NZS 3012 Electrical installations – Construction and demolition sites (in particular clause Permanent wiring located where construction or demolition work may be carried out).

Electrical Safety Office
1300 362 128

Last updated
24 August 2016

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