Safety Office

Section 11: Precautions in use of Electricity

The fundamental hazard is of electrocution. 25 volts can be fatal under certain circumstances. The voltage normally available at socket outlets and lighting points is 230 volts. Voltage on 3-phase equipment such as electric motors etc. is 415 volts. Electrical shock can be caused by bodily contact between two conductors or between a conductor and earth. Electrical shock and high frequency burns can be sustained from equipment such as oscilloscopes and T.V. apparatus. 

All precautions must be aimed at reducing the risk of contact with unprotected conductors of electricity at potentially hazardous voltages. The principle is to ensure that electrical equipment and wiring is safe by design, and remains safe throughout its use. 

All work with electricity must conform to the Electricity at Work Regulations 1989, which are based on this principle. The University’s Code of Practice for Electrical Safety provides guidance on implementing these Regulations and on safe working practices in general.

Part A PDF formatdeals with the safe use, maintenance, inspection and testing of commercial electrical equipment.

Part B PDF formatdeals with electrical equipment and test rigs designed and/or constructed within the University.

Part C PDF formatdeals with live working situations.

The introduction and Part A will be of universal application to Schools and Departments etc, whereas Parts B or C will be relevant to a very limited range of sections. 

11.1 General Precautions

Under no circumstances must electrical installations be interfered with. The fixed electrical installation of the buildings is the responsibility of the Chief Engineer within the Estate Office. The fixed installation includes wiring up to and including the socket outlet, or the isolator in the case of more permanently installed pieces of equipment. No one may work on the fixed installation without permission from the Chief Engineer. Schools and sections are responsible for wiring installations and equipment from the socket or isolator outwards. 

An inventory of electrical equipment is kept by Schools and Departments etc to enable necessary examinations and tests to be made. All equipment, including second hand equipment, which is new to the location, should be entered on the inventory and checked in accordance with the Code of Practice. Should equipment be mothballed and taken off the inspection and testing programme then it should be clearly labelled "Not to be used until inspected and/or tested" and disabled for use, for example by removal of the plug.

People using electrical equipment, as with all work equipment, should report any defects that they note so that remedial action may be taken. Defective equipment should be labelled as faulty and its associated plug removed if it is not repaired immediately. The range of checks which users should be able to carry out as a routine part of their work includes:

      • Damage (apart from light scuffing) to the insulating sheath around the cable
      • Damage to the plug
      • Joints in the cable other than by way of proprietary cable connectors
      • The ineffective securing of the outer insulation sheath of the cable where it enters the plug or the equipment, e.g. the coloured insulation of the internal cable cores was showing
      • Damage to the external casing of the equipment
      • Evidence of overheating, e.g. burn marks or discoloration to plugs, cables, or casings
      • Evidence of inappropriate use, e.g. it is wet or excessively contaminated with chemicals, oil or dirt etc.

Any loose connections, for example loose screws in plugs and switches, must be reported for remedial action to be taken.

11.2 Flexible Cables

Ensure that flexible cables are of the correct size for the load to be carried and sheathed with rubber or PVC to withstand mechanical damage. 

Flexible cables should be examined frequently to ensure that earth continuity is maintained and that no damage has occurred. Frayed or un-anchored cables or plugs must be reported immediately for remedial action to be taken. 

The use of flexible cables of excessive length is to be avoided. Extension cables should be used with great care and must not be joined except by the use of proper plugs and sockets. 

The use of multiple cables from one plug should be avoided. Approved 2, 3 or 4 way multiple sockets are available, but care should be taken not to exceed 3kW total load. Multiple socket boards are available with a mains neon indicator lamp, and consideration should be given to using an RCCD plug with such socket assemblies. Trailing cables can constitute a tripping hazard. Wherever practicable, there should be sufficient socket outlets to allow for the use of flexible cables of minimum length. Flexible cables must not be used for voltages above 240 or a loading greater than 3 kilowatts. 

Twin core cables, such as bell wire and twisted flex must not be used on 230 volts.  

11.3 Portable Appliances

These should be used with great care and particular attention paid to the condition of the flexible cable and its termination at the equipment and at the plug. It is recommended that low voltage or double insulated equipment should be used wherever possible and all new portable hand tools should be of this type. It is preferable that low voltage equipment should be of the cordless type, which does not need a transformer. If a 110 volt transformer is used it should be centre tapped to earth. It is a requirement of the Electricity at Work Regulations that all electrical equipment is maintained to avoid dangerous situations arising. Part A PDF formatof the Universities Code of Practice for Electrical Safety describes the arrangements for formal inspection, and testing where necessary, of portable electrical appliances. 

This applies equally to all privately owned mains-operated electrical equipment brought into the University. Such equipment must be approved by the School, Department or Hall and arrangements made for its regular testing. 

11.4 Fuses

The smallest fuse compatible forthe apparatus should be used in order to protect the equipment and flexible cable and to reduce the fire hazard. It is important that only proper cartridge fuses are used for replacement and in no case should any substitutes be employed. Before replacing a fuse, the reason for the fuse blowing should be ascertained and the cause remedied. Under no circumstances must an attempt be made to replace a fuse in a main fuse board.

11.5 Fire Hazard

The amount of electrical energy available from a socket outlet is more than sufficient to cause a fire if the equipment is misused or wrongly connected. It is recommended that plugs be removed from sockets when apparatus is not in use in order to reduce the hazard from live flexible cables. Use dry powder or Carbon Dioxide extinguishers only on electrical fires and isolate the source of supply if possible. 

Particular care should be taken when working near wet batteries during or shortly after charging. The hydrogen produced during charging could be ignited by an open flame or an electrical spark, for example a conductive tool short-circuiting across the terminals. Non-conductive or insulated tools should be used when working with wet batteries. 

If in doubt about any electrical apparatus advice can be obtained from the Senior Engineer within the Estate Office.  

11.6 Radiation Hazards from Certain High Voltage Electrical Equipment

In equipment incorporating electronic tubes operating at potentials above 5000 volts e.g. cathode ray tubes, electron microscopes, there is a risk that X-rays may be emitted. Work with such equipment may therefore be carried out only with the knowledge and approval of the Director of Health and Safety (see Section 13: Precautions with Sources of Ionising Radiation).


Safety Office

Pharmacy Building - Lower Ground Floor
University Park
University of Nottingham
Nottingham, NG7 2RD

Telephone: +44 (0)115 951 3401