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Technical focus

Emergency tips

Bernard Pratley, LIF’s technical manager, explains how the latest generations of fluorescent and LED lamps provide highly effective emergency lighting.

Emergency lighting and escape route illumination must make it easy for people evacuating a building to see clearly enough to safely and quickly make their way out, using the nearest and shortest designated exit paths. Most people unfamiliar with a building tend to leave it the same way that they entered it, often ignoring shorter escape routes that are not clearly marked. Compliance with BS EN 60598-2-22, the emergency lighting luminaires standard, and EN50172 (BS 5266 series), the emergency escape lighting application standards ensure that there will be sufficient illumination for people to see and be directed towards emergency exits, with exit or directional signs being in view at all points along the escape route. Today, nearly all emergency lighting applications are fulfilled using luminaires fitted with either fluorescent lamps or the latest generation of high quality white LEDs. Both types require their own particular considerations when being used in emergency lighting luminaires.

Fluorescent lamps: Manufacturers of fluorescent lamps have continuously developed ever more efficient lamps to reduce energy requirements whilst also minimising the amount of mercury to meet global environmental requirements. However, the reduction of mercury in a fluorescent lamp may affect the emergency lighting operation if the control gear is not designed to operate the low mercury fluorescent lamps - as might be the case with a lamp replacement situation. For example, the lamp may not strike, or if it does start, the slower increase in light output at switch-on may not meet the five seconds to 50 per cent and 60 seconds to 100 per cent output required by the product safety standard BSEN 60598-2-22. Additionally, insufficient power to the lamp could result in insufficient light output, and too low a lamp heat could shift the colour temperature to appear pink. The emergency period of operation may be reduced because of higher circuit watts demanded by the lamp. Moreover, lamps used for emergency lighting may have shorter service lives than those used for mains lighting. Care must be taken when replacing fluorescent lamps in emergency luminaires to ensure compatibility of the lamp with the control gear. The fluorescent lamp is an excellent solution for most emergency lighting applications, and simply requires high quality, fully compliant components and proper expertise from qualified suppliers to ensure that its implemented effectively. It is essential that emergency lighting luminaires are re-lamped in accordance with lamp


information supplied with the luminaire. Good quality fluorescent emergency luminaires offer the following benefits: • Very efficient and usually need to be dimmed in their emergency lighting mode – saving energy • High efficiency optical designs coupled with the greater flux enable wider spacing of luminaires • When correctly spaced, compliance with the applications standards of BS 5266 can be met with minimum power consumption • They have a proven performance record • They are economic.

LED lamps: Good quality white LED lamps are now suitable for both exit signs and emergency lighting. Because individual LEDs are almost a point light source, light control is simple, and well-designed LED emergency lighting luminaires, with their special optics, can use virtually all of the emitted light. Therefore, the high optical efficiency of LED luminaires provides the designed illumination for less initial flux (light) than would be needed from a conventional light source.

Good quality LED lamps bring many benefits:

• With the right optical design they can produce well-directed uniform light. • When correctly spaced, compliance with the applications standards of BS 5266 can be met with minimum power consumption • They provide the basis for a high-energy efficiency - up to 30 per cent better than good fluorescents because of the more directed light output. • Very long life (up to 60,000 hours at 70

per cent lumen depreciation) with good reliability. • They are nearly unbreakable. • They can provide significant cost savings over the life of the installation because of a mix of energy efficiency and reduced lamp replacement and maintenance costs • Unaffected by extremely low temperatures • They can be designed into buildings, structures and materials in ways that are impossible with conventional lighting, so provide great flexibility for designers. The advantages of LEDs have resulted in them being offered as a user replacement item in housings that replace T8 fluorescent lamps. These should not be used in mains luminaires that have dual use as emergency luminaires, unless they are checked to ensure they operate in the emergency condition and that their light output is adequate for the emergency duty.

Installation considerations for all lamp types in emergency lighting: Prior to installing emergency lighting and mains lighting modified for emergency lighting use, it is essential to leave batteries disconnected until the unswitched supply is no longer subject to frequent disconnection and/or switching. This will ensure that all emergency fittings don’t need to be re-lamped before commissioning. Seek advice about the suitability of lamps to operate with their equipment to ensure full compatibility.

Contact ICEL 020 8677 0718 www.a1ligh


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