We of course have the obvious choice between, Self Contained and Central Battery (CBU) and both have their strengths and weakness. The larger projects historically, tended to favour CBU with small to mid sized projects tending to use Self Contained emergency.
Along came LED’s and the split between CBU and Self Contained emergency fittings has dramatically shifted, in the favour of Self Contained. I will attempt to explain why this has happened and also some of the advantages and risks in those changes.
In the past when most commercial office lighting used fluorescent fittings; emergency lighting tended to be a conversion of the standard luminaire, or powered off a static invertor.
The static invertor or CBU had the advantage in that you could power the lamp fully so you then had a higher emergency light output, but the downside was that each emergency luminaire had to be separately wired with fire proof cabling and somehow connected back to a change over relay and the remotely mounted battery assembly in its fireproofed and air-conditioned room. Costly to purchase, expensive to install and with a life of approximately 10 years.
The major advantage of CBU systems was battery replacement and generally you could argue that due to the exacting standards required to optimise the batteries that maintenance regimes were good. They are not without their share of problems and the first amongst them was a single point of failure and secondly, poor maintenance resulted in many systems failing after a few years of installation.
Its worth mentioning that you also have Uninterrupted Power Supplier (UPS) used in centralised Emergency lighting, but be very careful when looking at these systems as generally they are not designed for multiple discharges and a 3 hour durations calls for a sizeable battery.
If you are going to install a CBU, then always consult a specialist.
The conversion of the fluorescent luminaire involved the modification of the luminaire with the introduction of a separate invertor. This invertor was wired in circuit with the ballast and would monitor the mains and in the event of a power failure would bypass the ballast and drive the fluorescent lamp at a lower output, power would be provided by the local battery stick. You would often see a figure quoted known as the Ballast Lumen Factor (BLF)which would often be a very low value of the output of the lamp when in emergency mode.
Now its worth point out that sometimes less is more when it comes to emergency lighting and uniformity is critical. What you don’t want is pools of light and dark so that individuals within the space become disorientated; low even illumination is what you need.
The advantages of Self Contained are many as you install the conversions where you need them, have a tested and approved luminaire and don’t have all of the additional costs of Fire proof cabling. There is also redundancy built into the system so that in the event of a partial failure, you have lighting where and when you need it. Now the downsides of conversions are unfortunately also many. Not all fluorescent lamps where the same, cable length was critical between driver and invertor and temperature affected batteries and performance. Poor installation and poor maintenance again affected the overall efficiency of the scheme.
So those were some of the historical challenges; now with the advent of LED’s in lighting all of this changed. LED’s allowed manufacturers to created dedicated emergency luminaires such as the Ektor Ledfire range, where the self contained emergency luminaire has a light source that will last for the life of the installation and where the only consumable was the battery. With the right battery choice, operating life of a self contained emergency luminaire can be extended to around 7 years and possibly longer. This then provides an emergency lighting product that matches the performance of CBU with regard to service life and has none of the additional on costs.
As we now have dedicated point sources in LED’s, optics can be fitted to deliver both “Open Area and “Corridor” solutions to give spacings of between 12 to 15m. You are able to place the emergency luminaires where you need them and reduce the overall number of luminaires significantly. Luminaires no longer need converting and retesting as the dedicated emergency luminaries are specifically designed to do one task and that is be a safety system in the event of power failure.
If we now consider the testing of emergency lighting then Self Contained emergency has a huge advantage with the advent of DALI emergency invertor’s. DALI has defined test commands for emergency self contained modules that ensures standard function such as Function test or Duration test are specific commands. Status on the battery, light source and module itself can also be obtained through DALI so a detailed snapshot of the status of the system at anyone time can be obtained via a known and widely used protocol.
If we now consider best practise for testing emergency lighting, BS EN 62034:2006 Automatic test systems for battery powered emergency escape lighting which details the testing regimes and timing of these tests then DALI is really the only solution that meets the criteria outlined in BS EN 62034:2006.
Self Contained emergency dedicated luminaires provide information based on an international standard IEC 62386 Part 102 (DALI) and fully meet best practise through BS EN 62034:2006.
There will still be a market for CBU’s but battery sizing will reduce with the use of LED’s, the only negative is the lack of detailed testing on individual luminaires and the installation. As a result of the shift in the market towards LED’s we see a move towards dedicated discrete emergency lighting that can be designed to operate as a standalone solution or as part of a wider Lighting Management system such as zencontrol.
As we move into ever smarter buildings its critical the technology we use is equally as smart and that includes the emergency lighting. At Ektor we use protocols such as IEC 62386 DALI that provides a smart monitored emergency test and monitoring system which reports directly to the Ektor cloud. This can be wired or wireless and provides a seamless interface from a life safety system to the clients Dashboard.
We take a consistent approach to integration of technology and from a Smart sensor through to a Smart emergency module we always base our developments on open protocols.
We at Ektor have solution that suits all emergency applications and as the manufacturer of the Emergency lighting and controls system compatibility is always guaranteed.
Safety is a right, not an option so ensure you select the right emergency and controls partner.
Stewart Langdown FSLL