Page 36 - Energize June 2021

TECHNICAL

Emergency and standby

lighting systems

by Mike Rycroft, Now Media

Emergency lighting is a legal requirement for all buildings and any place of assembly, while load shedding,
with its two hours, or longer, duration, has made standby lighting a de-facto requirement to ensure
business continuity. The availability of low energy high-intensity LED products has made the provision of
emergency and standby lighting simpler, less costly and more reliable.

mergency lighting is primarily intended to provide safe
evacuation routes in the case of emergencies and must work
Eproperly under all emergency conditions. Standby lighting is
meant to provide illumination which enables people to remain in a
building under non-emergency conditions, such as load shedding.
The introduction of load shedding, and the forecast that it will
continue far into the future means that power interruption is a
predictable and widespread common occurrence. This introduces a
new requirement for emergency lighting, and means that emergency
lighting will be used more often. Standby or emergency safety
lighting is adequate to allow occupants to stay in an area of the
Figure 1: Types of emergency lighting 4
building during a power failure, but may not be enough for all
functional tasks to be continued
points, stairwells, and at any place where there is inadequate
Statutory requirements natural lighting. This, however, does not restrict the placement of
OHSA Act emergency lighting in other areas if this improves building safety or
The occupational health and safety Act requires that “with a view is required for any other reason, such as areas where activities take
to the emergency evacuation of indoor workplaces without natural place which require safe shut down or disconnection of equipment
lighting or in which persons habitually work at night, every employer before evacuation, to ensure that unattended activation does not
shall, in such workplaces, provide emergency sources of lighting occur when the power is restored. Examples would include kitchens
which are such that, when activated, an illuminance of not less than and workshops where machinery is operated.
0,3 lux is obtained at floor level to enable employees to evacuate
such workplaces.” 1 Activation
Emergency lighting must be capable of being activated within 15
Compliance seconds of the failure of the normal lighting systems. Emergency
Emergency lighting systems must comply with SANS 10114-2:2020 lighting should be activated not only on complete failure of normal
“Interior lighting Part 2: Emergency lighting”. power but also in the case of a localised failure if such a failure
would present a hazard, for example, if a single sub-circuit on a
Types of emergency light stairway or in a high-risk work zone were to fail.
Emergency lighting, even under worst conditions, must provide
enough light for a sufficient time for the evacuation of people from Technology
the premises. Under other conditions some premises provide There are two key classes of emergency lighting: maintained and
standby power for essential plant only. Load shedding guarantees a non-maintained. Maintained emergency lighting stays on constantly
disconnection period of at least two hours, but often for as long as at all times and remains lit for the minimum emergency duration after
2,5 hours. Problems arising from the restoration of power sometimes a mains failure. It is used in places of assembly such as theatres,
cause longer delays; load shedding times of four hours exceeds the cinemas, entertainment halls, shopping centres and similar venues.
maximum emergency lighting operational time of three hours. it allows the public to familiarise themselves with emergency routes
The placement of emergency lighting is described in SANS and has the advantage that the failure of an emergency lighting lamp
10114-2:2020. Generally, emergency lighting is required at exit can be spotted immediately.

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