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Electrical Installation Guide

 

 

Safety of Electricial Installations - Guide for Residential Property Owners

 

Faults in the electrical wiring systems of properties account for the majority of fires and in some cases fatal electric shock accidents.  Every year approximately 25 people are killed by electricity at work. In addition to these fatalities, 1000 major injury accidents are also reported. (Source HSE 2006).

 

Around 25% of all electrical injury accidents are caused by portable electrical equipment (PEE).  Faulty electrical leads cause around 2000 fires each year.

 

Property owners are responsible for the overall safety of the electrical installation. i.e.

fixed wiring.

 

Main causes of electrical faults

 

The two most common faults are:

 

          Insulation failure

 

The electrical insulation which covers and protects the copper conductors of cables can fail for a variety of reasons. Modern wiring is insulated with durable PVC but older installations used rubber, which can become brittle with age.  This can lead to insulation breakdown resulting in short circuits. Short circuit faults can result in fires caused by the sparks and heat generated under fault conditions. Insulation breakdown could also result in metal surfaces, which are not adequately earthed, becoming "live" presenting the potential for a fatal electric shock. Damage can also be caused by vermin such as mice or rats who like to chew the insulation which when exposed can result in the faults identified above.

 

          Overheating

 

Overheating occurs when installations are overloaded, a classic example being the use of multi-adaptors or multi-socket extension leads. These are not inherently dangerous as they can be used quite safely to connect several low power items such as the home hifi, but they do facilitate overloading. If too many appliances are connected to an electrical circuit, excessive heat will be generated in the copper conductors which can lead to a breakdown of the insulation and a short circuit.

 

Work carried out by unqualified installers or tenants can also lead to the faults as described.

 

Installation, Inspection, Testing and

Maintenance

 

It is important to remember that installation, inspection, testing and maintenance of new or altered electrical systems should only be carried out by a competent qualified electrical tradesmen or contractor.

 

The electrical installation must be installed in accordance with the Institution of Engineering and Technology (IET) Wiring Regulations 18th edition now known as BS 7671:2019.

 

The IET Wiring Regulations establish the accepted safety parameters for designers, installers and testers of electrical installations. 

 

The IET Wiring Regulations have the status of a Code of Practice and whilst being nonstatutory, may be used in a court of law as evidence of the standard to be achieved.

 

It is recommended that electrical installations are tested at least once in every 5 year period or after any additions are made to the system.  Simple, visual inspections should take place more frequently.

 

 

Visual Inspection of the system will include:

 

          Safety

          Wear and Tear

          Corrosion

          Damage

          Excessive loading

          Age

          External influences (changes in building/occupancy)

          Suitability (e.g.of protective devices).

 

            

      Periodic electrical tests will include:

 

          Verification of effectiveness of earthing system

          Polarity

          Earth fault loop impedance

          Insulation resistance

          Operation of devices for isolation and switching

          Operation of residual current devices, over-current circuit breakers and fuses.

 

       A certificate showing details of the installation and the results of the tests should be issued.

 

Key Action Points

 

        Ensure that electrical installations, and any additions to existing systems, are only carried out by a competent person or contractor.  

 

        Ensure that the electrical installation is tested at least once in every 5 year period,

and a test certificate is issued

 

        Ensure that all electrical accessories (switches, sockets, pendants etc.) are of good quality.(Relevant BS or EN Standards)

 

        Respond quickly to all reported faults. Delay could result in property damage caused by fire or personal injury or death caused by electric shock.

 

 

Reference Documents:

 

Memorandum of Guidance on the Electricity at

Work Regulations 1989. HSE HSR25

 

BS 7671:2019 – Requirements for Electrical

Installations (IET Wiring Regulations 18th

Edition)

IET Guidance Note 3 to the 18th Edition

Wiring Regulations

Electrical Safety and You - HSE Free Leaflet INDG231(L).

 

 

HSE Electricity topic page:

www.hse.gov.uk/electricity/index.htm

 

Article supplied by Norwich Union insurance Ltd. for use by NAPIT members only

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© Electricity for Home and Garden. Stephen Martin is member of the National Association of Professional Inspectors and Testers