Element 6 Electrical Hazards and Control

The section of the NCC1 describes what hazards are posed by the presence of electricity on a construction site, the hazards posed by the use of electricity and associated equipment such as hand tools, extension cables, portable and fixed lighting, temporary supplies from mains or generators.

The use of electrical hand tools is considered a major hazard on construction sites, therefore there are guidelines on the inspection and record keeping for these tools or equipment.

Testing

• Every installation should be tested in accordance with BS 7671: Requirements for Electrical Installation, before use on site, at three-monthly intervals or shorter periods if necessary.
  
• The record of any testing and inspections should be made by a responsible person on the appropriate certificates.
  
• Testing and inspections must include:
  
  • a visual inspection
    
  • the continuity of final circuit conductors
    
  • the continuity of protective conductors
    
  • the earth electrode resistance
    
  • the insulation resistance
    
  • polarity
    
  • the earth fault loop impedance
    
  • the correct operation of residual current devices and fault voltage operated protective devices.
    

Suggested inspection and test frequencies for electrical equipment on construction sites

Equipment/application	Voltage	User check	Formal visual	Combined inspection and check
Battery operated power tools and torches	Less than 25 volt	No	No	No
25V Portable hand lamps	25 volt secondary winding from transformer	No	No	No
50V portable hand lamps	Secondary winding centre tapped to earth (25 volt)	No	No	Yearly
110V portable and hand held tools, extension leads, site lighting, movable wiring systems and switchgear	Secondary winding centre tapped to earth (50 volt)	Weekly	Monthly	Before first use and then 3 monthly
230V portable and hand held tools, extension leads and portable floodlighting	230 volt mains supply through 30mA RCD	Daily/every shift	Weekly	Before first use and then monthly
230V equipment such as lifts, hoists and fixed floodlighting	230 volt supply fuses or MCBs	Weekly	Monthly	Before first use and then 3 monthly
RCDs fixed **		Daily/every shift	Weekly	* Before first use and then 3 monthly
Equipment in site offices	230 volt office equipment	Monthly	6 monthly	Before first use and then yearly
* Note: RCDs need a different range of tests to other portable equipment, and equipment designed to carry out appropriate tests on RCDs need to be used. ** It is recommended that portable RCDs are tested monthly

Key points

• Electricity can be a killer - you cannot see it and may not know that an item of equipment is live – until you touch it.
  
• Buried cables and those inside partition walls or other 'hidden places' are just waiting for the unwary to accidentally damage the cable and cause themselves serious injury or even death.
  
• The electrical distribution systems found on site tend to operate in a harsh environment and must be treated with care and respect.
  
• No-one other than a qualified electrician must alter the site distribution system.
  
• Ideally, apart from mains-powered equipment in site offices, all other equipment such as electrical hand tools will run off a 110 volt supply.
  
• The safest electrically powered tools and equipment are those that run off batteries.
  

Causes of electric shock

• Contact between a live conductor and earth.
  
• Contact between phase and neutral conductors (as the body is likely to have less electrical resistance than any load).
  
• According to the Health and Safety Executive, the majority of electrical accidents happen because people are working on or close to equipment which is either, assumed to be dead but is, in fact, live
  
• known to be live, but workers have not received adequate training, lack adequate equipment or have not taken adequate precautions
  

Legislation covering the use of electricity on construction sites

• The Management of Health and Safety at Work Regulations 1999 (as amended)
  
• The Construction (Design and Management) Regulations 2007
  
• The Electricity at Work Regulations 1989
  
• The Provision and Use of Work Equipment Regulations 1998 (as amended)
  

Working near overhead power lines

The local electricity company must be consulted before any work starts and a safe system of work must be devised and implemented. Other suppliers may also need to be consulted, for example, Local Authorities, National Grid and other electricity companies.

Special attention should be paid to traffic movements and the erection of appropriate warning sign and barrier (goalposts) should be erected, this apply to the use of excavating machinery near overhead power lines.