Confused about Emergency Lighting

What should I do??

What’s the right approach?

Am I making a mistake?

It’s all so confusing

I’m sure we have all used those expressions along with many similar over the years. What is blindingly obvious to one individual will be a sea of confusion to another. The reasons are many and varied and often it’s down to how well you explain a proposition.

Now I am aware of the irony of explaining something that is confusing by writing a long-winded blog about it; do bear with me though!

?I will use emergency lighting as an example of an area where there is a great deal of confusion and where perhaps that confusion is exploited to help market solutions that don’t necessarily meet the clients’ expectations.

There are some hard and fast rules that relate to emergency lighting design as well as testing of the same.

We define, open areas, corridors and high-risk areas and provide a framework for light levels and uniformity. We consider the location of the emergency lighting in open plan areas as well as corridors. We carefully consider the location of exit signage as well as final exit signage on the exterior of the building.

The person undertaking the emergency lighting design must be competent and trained accordingly. As the designer of that scheme, he or she has the responsibility to make sure there is adequate safety lighting in the event of a power failure/emergency. I would caveat that the design is often based on design drawings and may not reflect the as built installation, especially when furniture locations haven’t been agreed.

?The design should always be reviewed, and that responsibility lies with the building owner/occupier. Think of emergency lighting as a process that evolves over time and needs to be reviewed regularly.

?We have a design, and this is where the “confusion” really starts. What style of luminaire, should I go dedicated or opt for a conversion?

What battery choice should I make and for me the one that is so often abused, manual or auto test. I will state that currently we should not be undertaking manual testing as it is open to abuse and there is zero evidence to support any testing. Auto test on the other hand provides an audited trail of test and maintenance and removes any ambiguity; it’s safe or it is not!

?So, let's try and unpack these questions and starting with should I use a dedicated emergency luminaire or conversion. I will also add in my thoughts on central battery versus self-contained at this juncture as well.

?The dedicated self-contained emergency luminaire will generally always be more efficient than a conversion as it uses specialist lens to optimise the efficient of the LED. It’s dedicated to one role and can be placed in the appropriate location to maximise the efficiency of the scheme.

?You need to do the analysis, however if well designed and it suits the application then the number of emergency luminaires can be significantly less on a scheme based around a dedicated emergency luminaire placed in the optimum position.

Conversions work in a number of applications where the ceiling restricts the use of a separate emergency or where you have a long linear run of lighting, for example.

The converted luminaire needs to be independently tested and a technical file created for that product. The performance of the conversion scheme is limited by the location of the conversion as it must follow the uniform layout of the lighting as well as the optics of the conversion. Generally, mains luminaires are not optimised for emergency operation.

?Central battery is an area where you run an existing luminaire off a centralised battery, and you drive the standard luminaire via this dedicated feed. Dedicated fireproof wiring needs to be installed to the emergency luminaires which is both costly and difficult to install. There are advantages and disadvantages with the possibility of higher light levels and in certain buildings this is desired although we must always consider the scheme design and strange as it may seem too much light can be a negative if not properly considered within the design of the emergency lighting scheme.

?The other major advantage of centralised system is that the batteries offer a longer operating life than some chemistries and can be accessed from one location. This is now being challenged with the current battery technology for self-contained as I will explain later.

?Also, when considering central battery, the location of the battery storage and monitoring has to be carefully considered.

There is a great deal of innovation in this area and LV centralised systems using DC are available with smaller battery packs that can be mounted on each floor. Again, there are pros and cons to these systems as well.

?Confused about Batteries

Batteries: there are currently three battery choices for self-contained emergency lighting Nickel Cadmium (NiCd). Nickel Metal Hydride (NiMh) and Lithium Iron Phosphate (LiFePO4)

Each chemistry has its own unique featured with Ni Cd for example being banned for general use as it contains a group 1 carcinogen. Emergency lighting has an exemption to use Ni Cd, for how long is still up for debate.

Ni Mh also contains a toxic heavy metal in Nickel, however, is far safer than Ni Cd. The energy density of Ni Mh is far better than Ni Cd so the cells are generally smaller to deliver the same level of charge. There are some negative to Ni Mh and this generally relates to life cycles which can see batteries failing their first duration test due to multiple power cycles during construction. This is more of a failing of application rather than chemistry

There is various data out there on the Capacity density of difference battery chemistry and our own data provides an indication of how each technology compares.

Details as follows:

??????????????????????????????????Ni-Cd?????????????40-60 Wh/kg

???????????????????????????????????Ni-MH ????????????60-120 Wh/kg

???????????????????????????????????LiFePO4 ????????135 Wh/kg

?At zencontrol/ektor we standardise on lithium specifically LiFePO4 as this has several advantages over other battery chemistries.?There are of course some challenges, and this relates to the charging circuit and LiFePO4 batteries will have an onboard battery management that will directly communicate to the battery convertor and share data not only on the basic charge, but also over/ under charge, over current/ short circuit, Under/ over temperature charge/ discharge as well as cell imbalance.

It worth mentioning that regardless of the chemistry each emergency convertor and battery are a matched system, and you must always replace batteries with OEM parts approved by the manufacturer.

At zencontrol/ ektor we have a full audit process through our test systems that recognises battery changes and confirms if the replacements cells are compliant due to the on-board battery management circuit. Unfortunately, Ni Cd and Ni Mh have no such protection so replacing a battery for a generic one from a wholesaler may compromise the safety and performance of your emergency system. After all, one white stick of batteries looks very much like another.

LiFePO4 has additional features that allow us to manage the circuit and once the cells are fully charges allow us to turn off the charging and only top up as required. The net result is a greener emergency solution that will use less energy through life as well extending the life of the cells and we have solutions in the market that have a 10-year life that matches the performance achieved from central battery systems.

Lithium is ubiquitous, it’s in every device from your mobile phone, laptop, children’s toys to many of the smart devices in our homes.?LiFeP04 batteries have taken a considerable share of the energy-storage market due to its lower cost, longer life, non-toxicity, thermal stability, safety, and reasonable energy density.

Testing and monitoring emergency lighting.

?This is an area where standardisation has made a massive difference to the selection of emergency products.?This is also perhaps the one area where the greatest confusion exists.

Emergency lighting can be tested in three ways.

Manual test

A key switch is used to interrupt the unswitched mains and forces the emergency lighting into test. It’s a legacy approach where we have no record of the test other than the word of the individual undertaking the test. Unfortunately, people are unreliable and often dont test systems properly.?

Self-test

?The emergency luminaire will undertake a random monthly 30 second test and annual discharge test based on the onboard clock within the invertor that will start to count once mains is first connected. A bi colour LED is used to indicate a pass or fail so Green or Green Flashing is positive with Red solid or Red flashing as a failure. The flashing indicates the type of failure and can help the maintenance team to understand if it’s a battery or light source failure.

A big step up from manual testing you do have a means for identifying if the test has been undertaken and what the result was. A process needs to be put in place to ensure the building is inspected monthly and then annually. The downside is you cannot determine when the test will be undertaken so possible nuisance in some applications. Also, the record is once again manual and down to the individual to complete correctly

?Autotest

?Based on IEC 62034 Automatic test systems for battery powered emergency escape lighting the automatic test system performs regular function tests to confirm the emergency lighting is there and working and will undertake testing outside of the normal working days and record this information either on site or remotely if part of a larger estate.

The protocol of choice for emergency lighting is IEC 62386 Part 202 which is DALI-2 for emergency and outlines the testing sequence and range of responses you can obtain from the emergency invertor. As it’s based-on DALI -2 there is a certification program that confirms compliance and allows OEM’s and End Users the freedom to purchase compliant products from multiple vendors.

As DALI-2 provides a certification scheme and is aligned to the IEC standard then you have the assurance that future developments will be supported and always backwards compatible. Any proprietary solution is just that, unique to one manufacturer, so as such you have no guarantees that this solution will be available for the life of the project.

?Wireless

?Let us add to the confusion by adding wireless testing and monitoring of emergency lighting into the mix. Actually, I don’t think this is as confusing as it might first appear if we consider the lessons learnt from Auto test. DALI-2 is key and the certification of DALI-2 for emergency will be expanded into what is known as DALI+ or DALI Wireless.

?Currently IEC 62386 Part 104 supports DALI over Thread as the wireless method for end to end communication of DALI. The certification program has yet to be ratified, however the IEC standard is in place and is the basis for wireless communication.

?Thread is a low power wireless protocol that enables IPv6 packets to be transmitted over networks based on IEEE 802.15.4 wireless technology. Its ideally suited to lighting and has a self-healing mesh network that can scale to any size of project. As the networks grows so does the resilience of the mesh, simply put the more wireless devices the more reliable your mesh. Reliability is further enhanced by the acknowledgement of messages to confirm delivery.

?IEC 62386 Part 104 will also support other protocols and most notably Bluetooth will be the one we will be familiar with and want to know more about. The DALI Alliance has worked with Bluetooth SIG to create a Gateway that must support Part 341. Without going into great detail this is the only standardised way of connecting DALI to Bluetooth.

?As a protocol Bluetooth gives you the basic structure, however companies can interpret commands through dedicated profiles or rules that lock in hardware to their company profile. This level of modification is a concern as some Bluetooth devices can only connect to each other if they have the right profile, so interoperability isn’t assured. It’s worth mentioning that currently the Part 341 Bluetooth gateway doesn’t support emergency, although this will be addressed in time.

?Other protocols are available and as previously mentioned different flavours of Bluetooth can be sourced from different manufacturers and although they are heavily modified they will function appropriately for emergency lighting as the data requirements are limited. The only real negative is they are not fully aligned to a standard and as such are only viable so long as the manufacturer supports this version of the protocol.

?Going back to the original theme of confusion and how do we remove the veil of confusion then perhaps we need to try and break down questions into bite sized chunks.

?Look at each section based not only on performance, also consider long term support and availability of hardware and software from multiple vendors.

At a component level drivers and invertor’s need to be interchangeable. We need the freedom and ability to source hardware from whoever we choose in the market.

?Systems and the management of these system will always have an element of the proprietary as software tends to be unique to the application or company. What we must avoid are solutions that limit choice, proprietary solutions certainly achieve this.

?Organisations like the DALI Alliance represent the lighting industry and they work with IEC to deliver standards that support an open approach to lighting. Being part of that club maintains standards and gives us options.

?Question everything and always try and add a standard to the documentation so that there is no ambiguity. Compliance to a standard is measurable whereas the expression in accordance with can be open to interpretation.

?Third party testing as provided by organisations such as the DALI Alliance takes away potential Risk and provides a framework to support your project.

?Companies will continue to innovate with ever smarter solutions and as a building owner, OEM or contractor you can benefit from a more competitive market where hardware is interoperable, and the life of the scheme is underpinned by standards that support the long term life of the project.

?Also, as a small footnote in order to be sustainable and to embrace the circular economy then solutions based around open standards provide the necessary framework and assurance for upgrade through life as well as the continued support of a scheme that may have been installed for many years. We don’t have to throw away lighting if properly supported through its life and providing its supported by multiple vendors.

?

This has been a bit of a long winded blog and trying to condense its content is tricky. Emergency lighting is an important topic, and everyone will have a view and choosing the solution that’s right for you will ultimately depend on several factors not mentioned such as cost and currently availability.

Question the salesperson from the company providing the solution and if in doubt ask them to explain why they have gone down a certain pathway. It may be the right approach for your application, or it may be a way of locking you into a product that can only be sourced from one or a limited number of suppliers. With a commodity product such as lighting, choice is everything so if in doubt talk to several companies and don’t forget to talk to the relevant standards bodies.

?You don’t have to know everything so use a standard as a tool to support your proposal. It’s there as a way of validating products so you don’t have to!

“The more you explain it, the more I don’t understand it.”

– Mark Twain.

Author Stewart Langdown FSLL

Contact details

email [email protected]

mobile +44 (0)7774 821093

Company website www.zencontrol.com