6.3 Safety Of Electrical  Equipment and Supplies.

Introduction

One of the most deadly and least understood hazards- potential cause for injury - is electricity. The hazards that arise with exposure to electricity are:

Definition

Electrical Equipment refers to a device that consists of an assembly of components powered by electricity either supplied via a socket outlet or a battery.

Electrical Installation is the electrical system installed in the University's premises that extends from the mains electricity supplier's switch board up to and including the outlet sockets. This system is the responsibility of the Property Services Department.   

 Electricity Regulations

The Electricity at Work Regulations impose specific requirements concerning safeguarding persons who may be dealing with electricity. Some of the duties set out in the Regulations are stringent, that is they are absolute, rather than "as far as is reasonably practicable". The regulations apply equally at all voltages. In general before working on any electrical equipment and system it should be effectively electrically isolated (dead /de-energised).

Property Services are responsible for the mains fed electrical supplies within the University up to and including the outlet sockets. Communication networks are the responsibility of the Computing Services. The owners of electrical equipment are responsible for their condition and use whether powered from the mains or batteries.

Competent Persons

Definition

A Competent Person is a person who has been approved by a Head of School or Department, on the basis of the individual's knowledge, experience and qualifications, to be competent to vet the safety of electrical equipment and/or to supervise others working with electrical equipment.

Any one working on electrical equipment, from the design, construction and repair to its testing and use, must have adequate knowledge, training and information to undertake their tasks safely. Persons who are not so qualified may work with electrical equipment provided suitable and sufficient supervision by a competent person is provided. The level of competence will depend on the nature of the work.

It is for the Area Safety Managers/Heads of Schools and Departments to approve whether a person is competent to carry out work with electrical equipment on the basis of assessment of the work and of the experience, knowledge and behaviour of the particular person. The individual should be approved in writing and the extent of the work that may be undertaken and supervised be specified.

If there is any doubt as to the competence of a person to undertake work on electrical equipment, then a Qualified Electrician, who has a formal qualification that is nationally recognised and who is compliant with the IEE Wiring Regulations and other relevant UK, EU and ISO standards on electrical systems, must be engaged.

Electrical Appliances

Earthed Equipment

Class 1 electrical equipment has a layer of insulation over the live conductors and exposed metal work is bonded to earth. The risk of electric shock is negligible with correctly earthed equipment and supply installation.

Care must be taken when using electrical equipment in high earth leakage areas such as wash up rooms.

Double Insulated Equipment

Class 2 equipment has all exposed metalwork separate from the conductors by two layers of insulation. There is no earth connection so that the integrity of the two layers of insulation are essential for electrical safety.

Residual Current Devices (RCD)

Residual Current Devices are designed to operate on alternating current (AC). They should in general prevent a person from receiving a lethal shock from fault current by restricting the current to 30 mA with a duration of 30 milliseconds. An RCD will give no protection from a live to neutral contact.

It is good practice to include a RCD as protection against failure of the primary earthing system.

Safety Extra Low Voltage System

A safety extra low voltage system is one in which the voltage does not exceed 50V AC between conductors in a circuit that is appropriately isolated from the supply mains and from earth by means such as a safe isolating transformer. The equivalent DC value is 120V DC ripple free.

Safety extra low voltage is advised for hand lamps and soldering irons, and other small hand held tools where there is a risk of electric shock.

Centre Tapped System

The centre tapped system has the mid-point of the reduced voltage (viz 110V or less) transformer earthed so the voltage to earth is about half the supply voltage.

The 110V CTE system is advised for electrically driven hand held portable tools. As most shocks occur between a live part and earth, the CTE will reduce the risk of shock.

Plugs

All plugs must be wired correctly and correctly fused. See Appendix 1 and 2. Plugs should be CE marked, or if older BSI kite marked.

Adaptors and Extension Sockets

Multipoint adaptors should be avoided. No more than one such adaptor may be used in any one mains outlet.

Extension sockets and adaptors must conform to British Standards.

Cables and Extension Cables

Power cables must be correctly fitted with plugs and sockets. The cable should be as short as possible and should be unreeled before use. Induction heating in a coiled cable can destroy the cable insulation and start a fire.

Care should also be taken to route cables safely to avoid creating a trip hazard.

Portable Equipment

Portable equipment refers to all electrical equipment that can be connected to an electrical supply system by a cable and plug. This means that a microwave oven that is wired into wall socket should be classed as portable equipment.

All portable electrical equipment needs to be tested for safety on a regular basis - the time interval depends of the equipment and its usage - by a person qualified to carry out the appropriate tests. A testing period of six months or less should be considered for hand held power tools, workshop equipment and equipment used out of doors. The frequency and the nature of the testing should be identified by a competent person.

An annual programme of testing of portable electrical equipment is provided by the University for its equipment. The tested electrical equipment should be identified with a label noting the date (month and year) of the last test. All electric tools and appliances tests should be recorded and readily available for inspection by safety personnel.

A visual inspection should be carried out by an operator every time before the equipment is used.

Electrical safety testing must be in accord with the latest edition of the IEE Wiring Regulations (17th Edition from July 2008)

Electrical Installation

The electrical installation needs to be designed, constructed, maintained, tested and modified by qualified persons in accordance with IEE Regulations and other relevant national standards.

 Purchase of Electrical Equipment

All equipment must be in compliance with the Electrical Equipment (Safety) Regulations, which requires electrical equipment to be safe and constructed in accordance with good engineering practice. Electrical equipment should be CE marked.

Design and Construction of Electrical Equipment

The design for equipment which uses electricity should be verified by a competent person before construction. The constructed equipment should be also verified by a competent person before being commissioned and used.

Users of Electrical Equipment

Heads of Schools and Department must ensure their staff and others who are users of the University's electrical equipment understand the requirements of this University guidance and code of practice. All electrical equipment that is not the property of the University should only be used following approval by a University competent person.

Faulty Electrical Equipment

If any electrical equipment or installation is suspected or recognised to be unsafe, it should be taken out of service directly.

In the case of electrical equipment, the item should be electrically isolated, labelled "Unsafe. Not for use" and either locked away or the plug removed until it is serviced by a competent electrician.

A suspected faulty electrical installation must be reported without delay to Property Services. A notice should be placed promptly to warn potential users of the electrical danger

Revised January 2008

Appendix 1 -  Electrical Safety Advice (1)

Appendix 2 - Electrical Safety Advice (2)