To: Health and Safety Enforcing Authorities
For the attention of: Local Authority Health and Safety Enforcement Managers, Health and Safety Regulators and others
This Local Authority Circular (LAC) provides technical guidance to enforcement officers and others on health and safety issues associated with electrical safety
1 This circular gives guidance for enforcement officers on joints and repairs in electric cables. Ever since electricity cables were first used the problem has arisen of how to joint them together. In order to achieve the degree of insulation, tensile and crushing strengths, conductivity and accessibility required in practice the traditional solution has been some form of junction box. The junction box typically incorporates: a method of securing the cable conductors (usually by soldering, screw-clamps or compressed ferrules); a method of insulation, which may be air, oil, bitumen or insulation applied in the form of tapes; and a method of enclosure and protection applicable to the environment.
2. The Electricity at Work Regulations 1989 require in Regulation 10, that every joint and connection shall be mechanically and electrically suitable for use. In this respect the joint or connection should be of proper construction as regards conductivity, insulation, mechanical strength and protection.
3. British Standard BS7671 (also known as the IEE Wiring Regulations – 17th Edition) gives the requirements for electrical installations; the requirements for joints and terminations are contained in Section 526. The performance of mechanical and compression joints is the subject of BS EN 61238 (or BS 4579 for old joints); the tensile strength of such joints is specified as a percentage of that of the cables which are being joined.
4. The following terms used in the circular reflect the general usage in industry although in conversation some interchangeability of terms does arise.
5. Underground cables are joined by ferrules (sweated or crimped) and the outer protection enclosure or box is usually filled with a plastic or bituminous compound. Such joints are often used above-ground for non-flexible cables and provided they are adequately protected and supported, are quite satisfactory. Modern versions of these joints use themo-shrink sleeving as the insulating and/or sheathing material but the principle remains the same.
6. Other cables in fixed wiring installations are generally joined by making them off in some form of enclosed junction box which, in many cases, does not incorporate any method of securing the cable against strain.
7. Home-made joints in flexible cables are not usually satisfactory because:
8. In most cases the quality of a joint can only be assessed by dismantling, a process that usually destroys it.
9. Some proprietary joints and cable connectors are much more acceptable; these incorporate terminals or compression fittings suitable for stranded conductors, cable clamps of a design similar to those used for plugs, and sleeving to reduce the flexing of the cable where it enters the connector. Where these features are present and the cables are properly terminated it would be difficult to show that the joint does not meet the requirements of Regulation 10 in respect of conductivity, insulation and mechanical strength. The adequacy of the mechanical protection afforded by the enclosure depends on the environment in which it is issued. Heat-shrinkable or pre-stretched sleeving may be adequate in some cases but other circumstances may demand additional protection.
10. Regulation 10 refers to the prevention of danger, additionally enforcement officers will need to consider the requirements of Regulation 4(1) of the Electricity at Work Regulations – all systems shall at all times be of such construction as to prevent, so far as is reasonably practicable, danger. E.g. An uninsulated joint or connector at less than 50 volts will not under normal circumstances present a shock risk although if completely unprotected it may come into contact with another conductor and cause a short circuit leading to burns or fire.
11. In non-flexible fixed wiring, joints which are clearly properly protected or enclosed in polymeric sleeving will not normally require action on the part of enforcement officers. Joints in fixed wiring which are finished with adhesive plastic tape may be satisfactory but it is unlikely that this can be determined with certainty unless the joint is dismantled.
12. A taped joint in which the tape is becoming loose or which shows other signs of distress should be viewed with suspicion and the occupier should be advised to replace it. "Home made" joints are not usually satisfactory (see para 7) and it is suggested that enforcement officers recommend the use of proprietary joints.
13. A flexible cable having a proprietary cable connector would generally be satisfactory provided the cable is properly made off and that the mechanical protection afforded by the enclosure is suitable for the environment.
14. In most cases occupiers should be advised to replace jointed flexible cables by a longer length of sound cable or to use properly designed cable couplers to join adjacent sections.
15. Before taking enforcement action in relation to apparently defective cable joints Enforcement Officers should seek advice from an HSE Electrical Specialist through their Enforcement Liaison Officer (ELO).