Faults in the electrical wiring systems of properties account for the majority of building fires and in some cases fatal electric shock accidents. Electrical installations are the cause of around a thousand accidents every year and thirty of these are fatal. Around 25% of all electrical injury accidents are caused by portable electrical equipment and faulty electrical leads cause around 2,000 fires each year.
Property owners are responsible for the overall safety of the electrical installations at their properties (eg fixed wiring). There is a need to manage the risks associated with both the fixed wiring and the use of portable appliances.
Fixed wiring should be subject to inspection and testing by a competent person at least every five years and more frequently if the conditions are extreme (e.g. if the wiring is subject to extremes of heat and humidity or the risk of physical damage is great). The two most common faults associated with fixed wiring are:
Insulation failure – Electrical insulation protects the wire of cables and can fail for a variety of reasons:
· Modern wiring is insulated with durable PVC but older rubber cables can become brittle with age and lead to insulationbreakdown resulting in short circuits and, in turn, fires
· Short circuits faults can result in fires caused by the sparks and heat generated under fault conditions
· Insulation breakdown can also result in metal surfaces, which if not adequately earthed, becoming “live” which presents the potential for a fatal electric shock
· In addition, damage can 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 occurs when installations are overloaded (e.g. the use of multi-adaptors or multi-socket extension leads). These can be used safely to connect several low power items but they do facilitate overloading
· If too many appliances are connected to an electrical circuit, excessive heat will be generated in the copper conductors. Excessive heat can lead to a breakdown of the insulation and a short circuit.
· Portable appliances, together with extension cables, present a much greater risk of electric shock than of fire.
· They should be subject to routine inspection e.g. daily checks by the user and less frequent inspection and testing by a competent person
· The extent of inspection and testing required will depend upon the equipment and its use
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 tradesman or contractor.
The electrical installation must be installed in accordance with the Institution of Engineering and Technology (IET) Wiring Regulations 17th edition, now known as BS 7671:2008.
The IET Wiring Regulations establish the accepted safe parameters for designers, installers and testers of electrical installations.
The IET Wiring Regulations have the status of a Code of Practice and, whilst being non-statutory, may be used in a court of law as evidence of the standard to be achieved.
These will include:
· Wear and tear
· Excessive loading
· External influences (changes in building/occupancy)
· Suitability (e.g. of protective devices)
Periodic Electrical Tests
These will include:
· Verification of effectiveness of earthing system
· 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 five year period or after any additions are made to the system and that 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
· Simple visual inspections should take place more frequently