Type (power supply) of Emergency Lighting
一．Self-Contained – Single Point
Advantages:
*The installation is faster and cheaper
*Standard wiring material may be used
*Failure of mains supply due to cable burn-through will automatically trigger the affected emergency luminaire to come on Low maintenance costs – periodic test and general cleaning, only, required
*Low hardware equipment costs – no requirement for extended wiring, special ventilation etc
*The integrity of the system is greater because each luminaire is independent of the others
*System can easily be extended with additional luminaires
*No special sub-circuit monitoring requirements
Disadvantages:
*The environmental conditions will vary throughout the system and batteries may be adversely affected by a relatively high or low ambient temperature
*Battery life is limited to between 2 and 4 years, dependent upon the application
*Testing requires isolation and observation of luminaires on an individual basis
In general, the decision to use either a central battery or a self-contained system is likely to be cost-determined. If an installation has longevity and low maintenance as priorities, then the higher initial cost of a central battery system may be acceptable for a large project. Typically, luminaire and installation costs are a major consideration, particularly on smaller jobs, and it is this criterion which makes the self-contained luminaire the most popular choice.
二．Central Battery Source
Advantages:
*Maintenance and routine testing is easier, with only one location to consider
*The life of a battery is between 5 and 25 years, dependent upon type
*Environmentally stable in a protected environment; the slave luminaire can operate at relatively high or low ambient temperatures
*Large batteries are cheaper per unit of power and luminaires are usually less expensive
Disadvantages:
*High capital equipment costs
*The cost of the installation and system wiring is high because fire resisting cable is required to each slave luminaire
*Poor system integrity – failure of battery or wiring circuit can disable a large part of the system
*A requirement for ‘battery room’ to house cells and charger circuits, etc; ventilation of acid gases may also be needed
*Localised mains failure may not trigger operation of emergency lighting in that area
*Voltage drop on the luminaire wired furthest from the central battery could become a problem
