Page 39 - Energize June 2021

TECHNICAL

emergency lights will require circuitry to activate the lamp upon Standby lighting
supply failure. Non-maintained units will require separate feeds Stand-by lighting is a non-mandatory part of emergency lighting
from the maintained units or means of signalling mains failure to that is provided to enable normal activities to continue substantially
the luminaire. A CBS system may require fireproof cabling whereas unchanged. Stand-by lighting is usually used where a standby
self-contained uses normal cabling. Cabling requirements can generator provides power to the building, and may involve all of
be reduced by the use of distributed control. Control units, that the normal lighting units, or a reduced number of normal lighting
may incorporate mains fail detectors, are placed in a zone to feed units. Stand-by lighting is typically seen today in supermarkets and
power to both maintained and non-maintained emergency lights shopping malls, where a limited number of lights are kept on during
from the same feed, from the CBS. load shedding.
Some emergency lighting standards have introduced the
Testing and maintenance concept of “Emergency Safety Lighting” (ESL) or “Stay Put
Any of the components in an emergency lighting system can Lighting” in response to the increasing application of emergency
fail and regular testing is required to ensure operation of the lighting to assist the safety of occupants who may stay in a
luminaire. All emergency lighting systems must be tested monthly. building during a failure of the grid power supply and ensure
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The period of simulated failure should be sufficient for the purpose business continuity. This situation is particularly relevant to load
of this test while minimising damage to the system components. shedding. In buildings where there is adequate natural lighting and
During this period, all luminaires and signs shall be checked to no other reason to evacuate, ESL can be applied effectively to
ensure that they are present, clean and functioning correctly. allow continuation of activities under load shedding. ESL should
An endurance test for the full duration of the emergency help occupants continue normal operations in the event of failure
lights must be carried out once a year. The emergency lights of the supply to normal lighting.
must still be working at the end of this test. The result must be The ESL may use separate lighting fixtures or may make use
recorded and, if failures are detected, these must be remedied of normal lighting fixtures combined with control circuits that limit
as soon as possible. Any batteries that do not last the required the number of lights that are switched on during load shedding.
period should be changed immediately. Life expectancy will vary Addressable lighting units connected to a lighting control unit or
depending on the make of the battery; with some makes it is four building management system can be used effectively to provide ESL,
years, some five years. When the life expectancy date expires as the number of lights on in an area can be set by the control unit
the batteries should be changed. It is a good idea that when a and varied as necessary.
battery is changed the date of installation is written on the battery This is particularly applicable in situations where the building is
for future reference. equipped with standby generators and UPS systems intended to keep
essential loads running, but which could not cope with the full lighting
Automatic test systems load of the building.
Manual testing and record keeping of emergency lighting is time- Lighting levels under ESL may be lower than the required levels,
consuming and is often neglected. There are numerous automatic but should still enable safe use of office or other equipment. In “high
test systems (ATS) available on the market that can be operated risk task areas” the illuminance value should not be less than 10% of
separately or integrated into building management systems. ATS the average of the normal lighting at the location of the risk. In some
make it possible to test at short intervals and can keep records of applications, such as hospital operating theatres, 100% of normal
such things as duration, battery capacity, etc. lighting levels may still be required.
These systems have built-in processors that enable self- If there is an ESL solution, the emergency action plan should
diagnosis, reporting and record keeping. This feature drastically make it clear how long occupants can stay and how the end of the
reduces maintenance costs because no manual emergency ESL period will be indicated. The plan should also make clear what
lighting tests are required. These units are programmed to happens at the end of the emergency duration and how occupants
continuously monitor the state of the emergency lighting system will be directed to safe exits. A maintenance plan also needs to be
and carry out the required function and duration tests. The fitting established, even if ELS is self-testing. Standby lighting is not a
will report, by a flashing code or buzzer, the nature of the fault substitute for emergency lighting, as the standby power supply could
which alerts the technician to replace the lamp or the battery. fail while grid power is absent. n

Addressable systems References
Addressable emergency lighting systems are available that can 1. Department of Labour: “Occupational health and safety ACT”.
be incorporated into a lighting control system (LCS) or building 2. S Marais: “South African Emergency Lighting Guide”, Cosine
management system. The system can perform all the required developments, 2011.
operating tests on lighting units, and produce reports on the 3. Thomas & Betts: “Emergency lighting guide”, www-public.tnb.com/
results of the tests. Tests could be carried out automatically 4. R MacPartland: “Emergency safety lighting - revisions to BS
at predetermined times, or under manual control. The control 5266”, www.thenbs.com/
unit can provide information in graphic form on the state of the 5. SABS: “SANS 10114-2:2020 Interior lighting, Part 2: Emergency
system, the configuration of the luminaires, the possibility of lighting”.
connecting the luminaires to the control unit, the operating state
and the autonomy period of each lighting unit. Send your comments to rogerl@nowmedia.co.za

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