3.5.1 -  Introduction

The Regulations are intended to prevent both fires and burns which arise from electrical causes. Equipment must be selected and installed with the prevention of fire and burns fully considered. Section 421, added in the 1994 amendments, require that persons, equipment and materials adjacent to electrical equipment must be protected from fire, burns and effects limiting the safe functioning of equipment. Three categories of thermal hazard are associated with an electrical installation.

1. - ignition arising directly from the installation,
2. - the spread of fire along cable runs or through trunking where proper fire stops have not been provided, and
3. - burns from electrical equipment.

The heat from direct sunlight will add significantly to the temperature of cables, and 20°C must be added to the ambient temperature when derating a cable subject to direct sunlight, unless it is permanently shaded in a way which does not reduce ventilation. Account must also be taken of the effect of the ultra-violet content of sunlight on the sheath and insulation of some types of cable.

Some types of electrical equipment are intended to become hot in normal service, and special attention is needed in these cases. For example, electric surface heating systems must comply fully with all three parts of BS 6351. Part 1 concerns the manufacture and design of the equipment itself, Part 2 with the design of the system in which it is used, and Part 3 its installation, maintenance and testing.