The LWF Blog

Fire Safety for Facilities Management Personnel – Emergency Escape Lighting – Part 167

September 12, 2022 11:28 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 166, LWF looked at design choices for emergency escape lighting installations. In part 167, we continue to discuss the types of emergency escape lighting system by considering Central Battery Systems.

While a self-contained luminaire is powered by its own battery, a central battery system involves the use of a single central battery and associated charger which is able to supply power to the ‘slave’ emergency lighting luminaires through a wiring system installed for purpose. This system is, in essence, a complete secondary lighting installation.

BS EN 1838:2013 provides details of conformity for the slave fittings. The design will require the batteries and control equipment to be housed within a metal ‘cubicle’ or, in the case of very large sites, a dedicated battery room.

Where the system is required to operate fluorescent fittings, a bulk inverter is necessary or an inverter must be fitted to every luminaire. When a bulk inverter is used, conventional 230 V luminaires can be used as slave fittings.

Uninterruptible power supply (UPS) systems are not always suitable for supplying emergency escape lighting. They are not always able to start fittings when mains failure has occurred due to the surge on start-up of large fluorescent loads. It may also be the case that individual distribution fuses under overload are blown. Particular care must be taken at the design stage of emergency lighting systems if a UPS system is to be used.

The costs of a central battery system can be prohibitive as full dedicated wiring must be provided between the central battery and the luminaires. Further expense can be anticipated because the wiring must be protected from fire to avoid loss of power to the luminaires. Either the wiring itself must be inherently fire-resistant – mineral-insulated copper-sheathed or other fire-resisting cable – or it must be protected from fire by fire-resisting construction. A metal or rigid PVC conduit would not be sufficient fire protection for non-fire-resisting cables.

Unless the protection provided to the system and wiring is suitable, the entire emergency escape lighting installation may be vulnerable to failure.

In part 168 of this series, LWF will continue to look at central battery emergency escape lighting systems. 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.