All internal public spaces and places of work require emergency lighting to ensure that buildings can be safely evacuated in the event of power failure.
Such systems require regular testing and failure to correctly maintain an emergency lighting system can result in substantial penalties and even criminal liabilities should injuries occur during an incident where the lighting was not operational through negligence. There are numerous emergency lighting systems offering varying degrees of complexity, cost and ongoing maintenance, this article explores the most commonly available systems, their benefits and disadvantages.
It is important to begin by outlining the testing requirements for emergency lighting in order to fully understand the maintenance aspects of such systems and why the lighting industry has developed more advanced solutions to resolve these challenges:
- BS 5266 is the emergency lighting standard which also dictates the testing requirements.
- All emergency lighting should be subjected to a monthly functional test, this is to demonstrate that the luminaire operates correctly in emergency mode should the power supply fail.
- All emergency lighting should be subjected to an annual duration test, this is to demonstrate that the battery is capable of operating for a period of three hours. Please note that the three hour duration is not a legal requirement, emergency lighting needs only provide one hour of duration to be legally compliant in most applications, however in the event that there is a brief power cut a three hour battery duration allows the building to be reoccupied immediately knowing that the batteries still contain sufficient charge for another evacuation should a second power cut occur. If all emergency lighting provided a duration of only one hour any power cut would mean that the building could not be reoccupied for a period of twenty four hours whilst the batteries recharge. In addition, some installations legally require a three hour duration, for example buildings such as hotels or other types of accommodation which cannot easily be evacuated immediately must offer a three hour duration of emergency lighting rather than one hour to comply. For this reason all emergency lighting in the UK is supplied and tested for three hours of emergency duration.
- When emergency testing is undertaken a log book should be completed with the date and outcome of the test as well as any defects that need to be rectified, this log book may be requested by the fire officer during inspections and failure to provide complete and up to date records can result in substantial penalties. Any emergency lighting failures found during testing should be rectified promptly.
Standard Emergency
Standard emergency is the most commonly used and lowest cost of all the common emergency lighting systems on the market. The emergency test is undertaken manually by disconnecting the permanent live supply to the luminaire. Installations which operate a standard emergency lighting system often have key switches installed, these are dedicated switches to instigate the emergency lighting test and require a specialist key to operate them preventing unqualified personnel accidentally initiating the emergency lighting.
Inspection of the emergency luminaires then has to be undertaken by walking the site and ensuring all luminaires are operating in emergency mode and recording the start and end of the test to time the duration. The log book to record test results also has to be completed.
Advantages
- Standard emergency is the lowest cost of all the emergency lighting systems.
- The wiring is simple and does not require additional DALI wiring to carry any data.
Disadvantages
- Testing luminaires is labour intensive, the lower up front cost of the emergency luminaires can often be quickly offset by the additional costs of carrying out functional and duration testing.
- It may not be feasible to test and inspect a very high quantity of luminaires and accurately record the outcome making standard emergency systems impractical for large installations.
Selftest Emergency
Selftest is the next step up from standard emergency and automates some aspects of emergency testing. Each luminaire individually undertakes its own emergency testing and signals the results of the tests via the indicator, the small LED in the front of the luminaire that is lit green in normal operation to indicate that battery is charging correctly. Upon failure of an emergency test this indicator will signal the failure by changing to red, or may flash red at differing speeds to indicate the nature of the fault.
Advantages
- Selftest eliminates the need to manually instigate tests and note the duration each luminaire operates in emergency mode, substantially reducing the labour cost of emergency testing.
- With each luminaire independently carrying out the annual duration test at randomised times the luminaires will not all be simultaneously discharged meaning buildings can be safely occupied regardless of emergency testing. Standard emergency luminaires are typically key switched tested at the same time so after the annual discharge test a 24 hour period should be left before reoccupying the building to allow the batteries to recharge.
Disadvantages
- There is still a duty to check the indicators in emergency luminaires each month and record the outcome. Whilst this is substantially quicker than having to manually instigate and time the duration of the emergency function, there is still a labour cost associated with selftest emergency lighting.
- Selftest luminaires are generally more costly than standard emergency.
- There is no industry standard for the operation of the indicator LED when an emergency test has failed, for example different manufacturers of emergency control gear might flash in different frequencies to indicate various failure modes. If manufacturers are mixed on an installation these differing signals could cause confusion.
- As emergency test times are randomised they may not be suitable for some applications where it is unacceptable for luminaires to change to emergency mode when the space is in use, typical examples are healthcare, educational spaces and retail front of house areas.
DALI Autotest Emergency
DALI is an internationally recognised protocol used to control both mains and emergency lighting. DALI allows every luminaire to be allocated a unique address allowing it to report its position and status to a central computer. DALI Emergency luminaires will undertake automatic emergency testing and report their status to a central computer, given that the luminaire is also addressed this allows you to view the status of every device centrally and see any failures including their location, simplifying repair. DALI emergency therefore removes any need to manually test and inspect emergency luminaires substantially reducing the maintenance cost of such systems. Automatic notifications can usually be generated to notify maintenance teams as soon as a failure is identified.
Advantages
- Eliminates the need to manually test or visually inspect luminaires.
- Centrally records all test results removing the need to complete a log book of tests.
- Identifies the luminaires by type and location allowing quick and simple repair.
Disadvantages
- Amongst the most costly of all the emergency systems.
- Requires additional wiring to carry the data between the luminaire and the central computer.
- Requires additional infrastructure such as routers.
- Requires commissioning to set the location of each emergency luminaire.
Wireless Emergency
Wireless emergency systems offer similar benefits to a DALI installation with automated testing of luminaires and centralised reporting of the results, but have the benefit of transmitting the data wirelessly, negating the need for the data cabling that is required with a traditional DALI system. Wireless systems therefore offer substantial maintenance savings over manual emergency testing, but are simpler to install than DALI and are ideally suited to retrofit applications where there is no data cabling currently installed. Many wireless systems report directly to a cloud based database accessible through a web portal making them ideally suited to multi-site installations which need to be monitored from a head office.
There are a wide range of wireless emergency test systems on the market, these systems are generally proprietary and there is no widely adopted international standard for wireless lighting controls as there is with DALI, although it is likely that this will be implemented in the future. These systems offer a wide range of differing functions and benefits, so the advantages and disadvantages listed are generalised for the majority of systems and it is important to check with each supplier exactly what functions their particular system will support.
Advantages
- Eliminates the need to manually test or visually inspect luminaires.
- Centrally records all test results removing the need to complete a log book of tests.
- Identifies the luminaires by type and location allowing quick and simple repair.
- Eliminates the need for data cabling across the site.
Disadvantages
- Wireless systems are generally high cost.
- Some external infrastructure is still required, typically these might be wireless routers placed around the building with internet access, and some systems may need additional peripheral devices.
- It is important to understand the infrastructure and layout of your building to ensure that wireless communication will be reliable.
Proprietary Emergency Systems
A number of manufacturers produce their own proprietary emergency systems offering similar benefits to DALI Emergency, enabling automated testing and centralised reporting of the results. It is not practical to explore such systems in this article given the range of products available and the unique features of each, however although such systems may offer additional benefits over traditional DALI systems, if there is a desire that future expansions must be compatible they must also utilise the same components limiting purchasing options. On the contrary DALI gives access to a wide selection of luminaires and components given its standardisation across the lighting industry. Whilst there are benefits and downsides to both choices, it is important to understand which is most suitable for you and the project you are undertaking before opting for any particular system.
Central Battery Emergency
Because of the complexity of central battery systems we have produced a dedicated article in this knowledge hub titled “Central Battery Systems”, please see this for further details.
