Site Temporary

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Electrical Contractors starting work on a site

Site requirements must have a site-specific induction informing persons of the particular risks associated with the site and the arrangements made to control those risks. The detail provided will be determined by the risks involved.

On a typical construction site for the construction of a blocks of flats, the facilities and equipment requiring a temporary electrical supply include:

Three-phase

• 400 Volts
  Tower crane
  Batching plant
  

Single-phase

• 230 Volts
• Welfare facilities
• Personnel security gate
• Exterior floodlighting
• Reduced Low Voltage (RLV) 110 V

Socket-outlets and site lighting

• 50 V

Portable hand lamps

• 25 V

Portable hand lamps for use in confined or damp situations.

Where an RCD protects a tower crane supply, it will need to have appropriate trip current and time-delay settings to avoid unwanted tripping and to achieve selectivity (discrimination) between RCDs.

As an alternative to a temporary electrical supply from an electricity supplier, or to supplement the supply, portable generator(s) may be used. The manufacturer’s instructions must be followed.

All units for the distribution of electricity are to comply with BS 4363 Specification for distribution assemblies for RLV supplies on construction and building sites. Socket-outlets to BS EN 60309-2 are designed to prevent plugs designed for one voltage being connected to socket-outlets of another voltage. This is achieved by different positions of the keyway in the plug and socket-outlet.

Plugs, socket-outlets and cable couplers are colour- coded to identify the rated voltage (Table 1).

Cables

Cables should be installed in ducts below ground level, typically 0.5 metres. A record of the location should be recorded using maps or plans showing route and depth. Alternatively, a suitably protected overhead cable can be run at a suitable height.

All distribution cables which carry 400 V or 230 V on a construction site must have a metal sheath or armour which is effectively earthed.

Lighting

In order that work can continue effectively and safely in periods of insufficient natural light, suitable internal and external artificial lighting must be installed. The Clean Neighbourhoods and Environment Act allows Local Authorities to undertake action when external light emitted from premises is prejudicial to health or is a nuisance.

Testing and Inspection

Table 3 of IET Guidance Note 3 Inspection and Testing, recommends that construction site installations should be inspected and tested every 3 months.
Portable tools used by contractors must be tested and proof of testing retained before they will be allowed on site. IET Code of Practice for In-service Inspection and Testing of Electrical Equipment, Table 7.1 provides guidance for formal inspections to be carried out and recorded at monthly intervals and combined inspection and testing every 3 months.

Construction sites are one of the more challenging environments to the safe use of electricity, as work is carried out in all weathers. Damp and wet conditions and sites which are constantly changing as work progresses can increase the risk of electric shock. Consequently, diligence and observation of relevant requirements are all the more necessary.