Electricity - Systems in buildings
What you need to do
The law says you must take precautions against the risk of death or injury from electricity during construction work.
Refurbishment work in buildings presents the greatest risk and must be planned, managed and monitored to ensure that workers are not exposed to risk from electricity.
Specific specialist electrical work should only be undertaken by those who are trained and competent to do so and by following strict procedures
The electrical equipment used must be safe, and properly maintained.
The key issues are:
What you need to know
About three workers are electrocuted each year during refurbishment work on commercial and domestic buildings. Further deaths occur in incidents involving overhead power lines and underground electric cables.
Incidents within buildings involve both qualified electricians and other trades people. They happen when people are working on or close to equipment that is either:
- assumed to be dead but is in fact live; or
- known to be live but adequate precautions are not taken.
There are many more incidents which damage equipment and thousands of 'near-misses', any of which could have had fatal results.
Remember: electricity can kill – unlike most other hazards you cannot see, feel, hear or smell electricity so there is no advance warning of danger.
Managing electrical risk during refurbishment work
A number of electrocutions involve workers who are not electricians but who are carrying other works, such as plumbers and joiners. These incidents could be reduced by:
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Understanding the system
Those responsible for planning and managing refurbishment work must understand the electrical system of the building in which the work takes place and liaise with the building occupier.
This will enable building work to be planned and managed so that the integrity of the electrical system is not compromised and the workforce remains safe.
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Working dead
Relevant parts of the electrical system should be isolated if the refurbishment work, eg labouring, joinery, or plumbing, is liable to disturb or damage the existing electrical system and expose people to electrical danger.
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Portable electrical equipment
Tools, plugs and cables designed for DIY and domestic use are not suitable for site conditions. You should use cordless tools or those that operate from a 110V centre tapped to earth (CTE) supply system so that the maximum voltage to earth does not exceed 55V.
Regularly inspect power tools and take them out of service if they are damaged. Tools should be serviced by qualified electricians. Do not do makeshift repairs.
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Residual current (trip) devices
Where mains voltage (230v) is used, the risk of injury is high if equipment, tools, or leads are damaged or there is a fault. 230v equipment should be visually checked for damage every shift, have a visual inspection every week and have a combined inspection and test before first use on a site and then every month - ideally records of these checks should be kept. An RCD is a device which detects some, but not all, faults in the electrical system and rapidly switches off the supply.
RCDs must be properly installed and enclosed; checked daily; treated with care; kept free of moisture and dirt; and protected against vibration and mechanical damage.
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Lighting systems
Protect cabling and bulbs against breakage. If a bulb breaks, the exposed filament may present a hazard. Have a system for checking bulbs regularly to maintain electrical safety and to keep the site well-lit.
Controlling risk to electricians
Electricians are not immune from electrical dangers. A number of the electrocutions on construction projects involve qualified electricians.
Safe working practices rely on clearly thought-out systems of work, carried through by competent and trained personnel who are self-disciplined and aware of their own limitations.
To plan and execute electrical work safely, there should be adequate information available about the electrical system and the work to be done.
Electrical contractors should not work 'live' if it can be avoided nor should they make systems live before they have finished their work and everything has been installed correctly.
Safe isolation procedures must be followed at all times.
Remember: electrical work should only be undertaken by those who are trained and competent to do so.