The LWF Blog

Fire Safety for Facilities Management Personnel – Fire Prevention – Part 98

May 17, 2021 10:36 am

Lawrence Webster Forrest (LWF) is a specialist fire engineering and fire risk management consultancy whose aim is to give information on best practice in fire safety for facilities management personnel through this blog series. In part 97, LWF considered the reasons electrical fires can start and discussed the Wiring Regulations. In part 98, we will continue to discuss electrical fires and residual current devices.

Electrical switchgear and distribution boards can be a potential source of ignition, if combustible materials are within reach. It is important, therefore, that this potential source of fire is mitigated and combustibles kept clear. Where a small enclosure is used to house electrical distribution equipment, it should be noted that it was designed purely for that purpose and should not be used for the storage of any other product, and critically, not any materials that could be combustible.

Where large cupboards are used for storage, but also house electrical distribution equipment, a clear space of 500 mm (half a metre) as minimum must be allowed, but a distance of around a metre is a better choice for fire safety purposes. Highly flammable liquids, flammable gases or aerosols should never be kept in the same area as electrical distribution equipment.

 

Residual Current Devices

It is common for there to be a leakage of very small currents between the cable conductors and earth that cannot be prevented by fuses and miniature circuit breakers. Minor cable damage or the early stages of cable insulation failure can be the cause. These small currents can result in local overheating and a fire.

Circuit protection will only be tripped when sufficient current is drawn to cause adequate overcurrent, but the small current leakage could already have resulted in a fire before this occurs.

It is possible to protect against small earth current leakage by the use of a residual current device (RCD). The device is designed to compare the current in the neutral and live conductors of a single-phase circuit and ensure they are the same. Any difference indicates a leakage to earth. At a pre set value, the RCD isolates the supply automatically.

It is common to see RCD used when the power points are intended to supply outdoor electrical appliances, but they are also used regularly to protect against electric shock and fire.

In part 99 of this series, LWF will continue to discuss the use of RCD to prevent fire before considering temporary electrical installations. In the meantime, if you have any queries about your own facilities or wish to discuss this blog series, please contact LWF on freephone 0800 410 1130.

Lawrence Webster Forrest is a fire engineering consultancy based in Surrey with over 25 years’ experience, which provides a wide range of consultancy services to professionals involved in the design, development and construction and operation of buildings.

While care has been taken to ensure that information contained in LWF’s publications is true and correct at the time of publication, changes in circumstances after the time of publication may impact on the accuracy of this information.