Electrical installations on construction and demolition sites must comply with:
- AS/NZS 3000 Electrical Installations (known as the Wiring Rules)
- AS/NZS 3012 Electrical installations – Construction and demolition sites.
The following information explains basic requirements for residual current devices (RCDs) on construction and demolition sites according to AS/NZS 3012.
How RCDs work
RCDs (also known as safety switches) are electrical safety devices designed to immediately switch off the supply of electricity when electricity leaking to earth is detected at harmful levels.
RCDs work by continuously comparing the current flow in both the active (supply) and the neutral (return) conductors. If this current flow becomes unbalanced — where the supply may be leaking to earth and is therefore not returning to the source — a properly installed and maintained RCD will quickly disconnect the electrical supply.
RCDs will not trigger off electricity supply if a person contacts both active and neutral conductors while handling faulty plugs or electrical equipment and electricity flow through the person’s body, unless there is also a current flow to earth (which usually occurs though normal body contact with the ground or earthed metal parts)
RCDs don’t provide protection for all circumstances. They won’t protect against overcurrent (overload) or all short-circuit conditions.
Therefore workplaces must ensure they have safe systems of work for using electrical equipment: for example, inspecting and testing equipment, not working in or around water, and implementing processes that prevent damage to equipment.
How to use an RCD
All appliances, luminaires and other electrical equipment must be supplied from a circuit protected by an RCD. The RCD may be installed on a switchboard, incorporated in a socket outlet, or incorporated into a portable socket-outlet assembly (power board), such as an orange ‘RCD box’.
Existing installations should be inspected by a competent person to verify the existence of an RCD, which should then be tested. If the installation does not incorporate a fixed RCD, a portable RCD protected socket-outlet assembly or similar must be used.
RCDs must have a rated tripping current no greater than 30mA.
Testing and inspecting RCDs
Portable RCDs: Portable RCD protected socket outlet assembly
- These should be successfully operated by means of their in-built test facility (push-button) after connecting to a socket and before connecting equipment or at least once every day.
- A test for operating time must be done every 3 months.
- After inspecting and testing, portable equipment should be fitted with a durable, non-reusable, non-metallic tag. This tag should state the name of person/company who performed the test, and the test or re-test date.
Fixed RCDs: Switchboard or socket outlet
- These should be successfully operated by means of their in-built test facility (push-button) every month.
- A test for operating time must be done every 12 months.
- Equipment with fixed RCDs (such as construction switchboards) must be retested and inspected if relocated.
- Records of test and inspections must be kept and available for review.
If a fixed RCD in a switchboard trips, you must investigate to determine the cause of the trip before you reset the RCD.
You must develop a process for investigating and resetting RCDs: for example, who has the authority on site to investigate the trip and reset the RCD.
You can prevent any unauthorised resetting of a fixed RCD in a switchboard by having a lockable cover over the RCD or having a documented process that is communicated to all workers on site, with clear signage over the RCD stating who is authorised to reset the RCD.
WorkSafe Tasmania resources
SAI Global (external link) for the Australian Standards referred to here.