Page 38 - Energize June 2021

TECHNICAL

separate feed to the EL. In the CBS system there is no internal battery
in the luminaire housing and power for the light is fed directly from
the CBS supply. The output of the CBS may be AC or DC. The CBS
may consist of a single unit for the whole building or a number of
distributed units throughout the building. The CBS is usually equipped
with separate outputs for maintained and non-maintained units.
CBS systems available on the market range from 500 W to
several kilowatt and can be paralleled to provide even greater
capacity. Autonomy periods are not limited by the physical size of
the luminaires but can be chosen to suit the building requirements.
Figure 4: Centralised battery emergency lighting system Autonomy of up to 8 h is offered on some systems and will depend
on the number of luminaires connected. Table 1 gives an example of
Centralised battery systems (CBS) the capacity of a commercially available CBS.
The CBS is a popular choice for large buildings. In the CBS, the The mains failure function is performed by the CBS, but
power for the emergency lights is provided from a single centralised local mains failure units may be required where zone feeding is
battery system. used. Additional mains fail detection units may be required where
CBS are today much more than just reserve power units but distributed control is implemented. The CBS will contain mains
include comprehensive automatic test and monitoring systems fail detection circuits to facilitate changeover from the main to
which provide an extensive range of system information, thereby standby power. Configuration will depend on whether emergency
enabling more effective maintenance of the system. lighting systems are maintained or non-maintained. Non-maintained
Centralised battery systems have the advantage of a single
large battery that can be easily accessed, monitored and managed, Autonomy Wattage No. of 10 W luminaires
as opposed to multiple single batteries that need to be tested and
1 h 1500 150
managed. The disadvantage of the central battery is that failure
3 h 500 50
will affect all circuits. For this reason it is general practice in large
buildings to provide centralised supplies on a zone area basis rather 8 h 300 30
than for the whole building. Using a centralised battery requires a Table 1: Autonomy provided by CBS (Schneider)

Figure 5: Distributed central battery systems Figure 6: Central battery system with distribution units

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