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 switchboards on construction and demolition sites according to AS/NZS 3012.
Switchboards should be:
- robustly constructed
- securely attached to a pole, post, wall, floor or other structure unless of a stable, freestanding design
- able to withstand any external forces that may be exerted on the board; for example, from flexible cords/extension leads.
Switchboards must be protected from any damage from the work being done.
Enclosing the switchboard
The switchboard enclosure should have a minimum degree of protection of IP23 (protected from touch by fingers and objects greater than 12 millimetres and protected from water spray less than 60 degrees from vertical).
Live parts should be effectively protected at all times against contact by a person.
Any openings to live parts should be covered with escutcheon plates or similar.
Where the switchboard is provided with socket-outlets, make sure there is a way of preventing strain when you anchor external flexible cables and cords. For example, use an insulated or covered tie bar.
Switchboard enclosures are to be:
- provided with door locking facilities
- fitted with a means of retention in the open position and when closed
- allow the safe entry of flexible cables and cords.
Penetrations in switchboard enclosures for the safe entry of flexible cables and cords should be:
- adequately sized to allow the entry of multiple cables and cords
- insulated to prevent damage to cable/cord sheaths.
While switchboards should be readily accessible with clear and unrestricted access maintained in front of the door, they should be kept closed except when access is required.
Distribution boards should be located on each level of multi-level buildings, in a way that eliminates the need for flexible cords or cables to be run between levels.
This requirement does not apply to work in lift shafts, stairwells, service shafts, formwork, external staging or sub-mains of construction wiring or a single domestic residence Class 1, 2, 10. In these instances a lead can be run up or down one level from a switchboard, as long as they are mechanically protected at transition points between levels.
The number of boards on each level will depend on the size and layout of the building.
Boards should be positioned to ensure the maximum length of any flexible cords does not exceed the lengths set out in Table 1 of AS 3012. For example:
- a 10 amp flexible cord with 1.5 mm conductor area can run to 35 metres
- a 10 amp flexible cord with a 2.5 mm conductor area can run to 60 metres.
Switchboards must be fitted with one isolating switch, which shall interrupt and isolate all supply from the board including all sub-circuits and sub-mains.
Isolating switches must have a means of isolation to prevent electrical equipment from being inadvertently re-energised. This may be achieved by:
- fitting a padlock, or
- locating it in a lockable space or enclosure.
If you have more than one switchboard on the worksite, you must be able to distinguish between them by clearly marking with numbers, letters or both; for example, Temp Board 1.
The source of the supply to the board should be legibly and permanently marked on the board; for example ‘Fed from main switchboard in control room’ or ‘Fed from temp Board 1–Site office’.
The external surface should have a clearly visible and legible sign stating ‘Keep closed—Run all leads through bottom’.
A danger sign with an additional message indicating the presence of live parts within should be clearly displayed on the enclosure. Where access to live parts is required, an electric shock risk sign should be displayed anywhere additional attention is required; for example, when removing covers.
Isolation switches shall be marked:
- ‘Main Switch’ for the main switch for site supply
- ‘Distribution Board Isolating Switch’ for switches on distribution/temporary boards
- ‘Isolating Switch After Hours Supply – Do Not Switch Off’ for circuits supplying electrical equipment operating out of normal hours.
Letters used for marking should not be less than 6 mm high, and should be in a contrasting colour to the background material.
Prior to initial use, switchboards should be inspected and tested by a qualified person in accordance with AS/NZS 3000.
If a board is relocated on site, it must be re-inspected and re-tested.
Residual current devices (RCDs) on switchboards are classified as fixed RCDs under AS/NZS 3012 (section 3.5). This mandates a monthly test of their in-built test facility (push-button) and an operating time test every 12 months by a competent person. However Worksafe Tasmania recommends a more frequent test period due to the nature and environment of construction and demolition sites.
Construction wiring associated with switchboards shall be visually inspected by a qualified person to verify the integrity of the installation every 6 months.
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.