2007-11-19
Emergency lighting is mandatory in many public buildings and workplaces, but there are many different types of emergency light.
The key groups of emergency lights are related to the fitting type and light source type;
- Maintained or Non-maintained
- Emergency converted fittings (local battery supply) or Central battery supplied fittings
- Fluorescent lamp, Halogen lamp or LED light.
Maintained fittings are those that may also be used for general lighting when not in emergency mode – i.e. they can be switched on and off with normal fittings. These are commonly found in offices were a percentage of the ceiling luminaires will have one lamp that is also used as an emergency lamp.
Non-maintained fittings are those that only come on when there is a mains failure – they are not used in everyday illumination and so they are not switched with the other fittings. A typical example of application of this type is in bars and restaurants where the general lighting is more aesthetic and so not suited to being used in an emergency mode. The emergency fittings are additional units placed strategically around the building and are normally not noticed by customers.
Emergency converted fittings are found commonly in the UK, whereas on mainland Europe central battery supplies are more common. This is possibly on the grounds of installation cost and simplicity. The emergency converted fitting has a small battery pack and ‘inverter’ unit in addition to the normal fitting. The battery pack and inverter will usually operate just one of the lamps in a multi-lamp fitting and will isolate the other lamps and control gear in the fitting when in emergency more. This type of fitting will always need a permanent live supply (in addition to a switched live if it is a maintained fitting). Upon loss of supply on the permanent live feed, the inverter will automatically change over to the battery pack and the single lamp.
The central battery supply utilises a large battery pack (and inverter) located remotely in the building to power all of the emergency fittings in an area. One virtue of this arrangement is that the battery pack is capable of supplying enough voltage to the normal control gear in the fitting, so no changeover unit or local battery is required in the fitting and the lamps are operated within normal parameters – maintaining expected lamp life. Additional cable feeds are required from the battery supply to the emergency fittings.
Fluorescent lamps are the most common form of emergency light source – their high efficiency makes them ideal for giving maximum light output and illumination time from a restricted battery supply. However, if the lamps are not operated within normal running parameters in emergency mode (cathode heating and lamp current) then the average life of the lamp can be severely reduced. This is a common occurrence with emergency converted fittings with a small local battery as the available power supply capacity is restricted. Typically the lamp ends will blacken rapidly during emergency operation as the lamp cathodes are eroded. OSRAM have recognised this issue and provide two special lamps which perform better in this application – T5 8W EL and T5 6W EL with more robust cathodes.
Halogen spot lamp fittings are also found where a separate emergency fitting is desired without affecting the general lighting fittings. This is common in factories and large, high roofed retail premises. Here the lamps are not adversely affected by supply limitations.
The most recent form of emergency light source is the LED. Luminous outputs from the most recent high-flux products are now sufficient for their consideration as emergency light sources. They have the benefit that their small proportions can be easily accommodated within luminaires without adversely affecting aesthetics, and they are more efficient than filament light sources, while not being adversely affected by limited power supply from batteries. They also offer incredibly long life so offer a possible ‘fit and forget’ solution. OSRAM have many suitable LED products for this use, DRAGONeye and DRAGONpuck being two that are particularly popular.
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Related contacts
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OSRAM Limited
OSRAM House
Waterside Drive
Langley
Berkshire SL3 6EZ
Tel: 01744 812221
fax: 01744 831900 |
Email OSRAM
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Source: OSRAM |
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