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Author: Philip Payne Admin | Date: 24th Feb 2021

To support Electrical Consultants designing an emergency lighting installation; here we explain the difference between self-contained and central battery systems.

In a situation when the standard lighting has failed, emergency lighting illuminates the escape routes through a building, to enable people to move safely to the exits.

Emergency luminaires also ensure that essential safety items such as first-aid points, fire-alarms and fire-fighting equipment can be located.

Emergency lighting systems must be designed and installed to meet the requirements of British Standard 5266 Code of Practice. You can find out more about BS 5266 here.

What is the best option?
Fundamentally it all comes down to the layout and the size of the building(s) and the use of the space you’ll be working with.

Both self-contained and central battery systems have their advantages and disadvantages, depending on your project.

Let’s unpack each of them.

Self-contained emergency luminaires

Because self-contained emergency luminaires include their own batteries and operate independently, they provide the simplest and the quickest installation option.

The cost of installation can be relatively cheap because there is no need for any special, fire-rated cabling. In addition, as each luminaire is independent of the others, no special sub-circuit monitoring is needed. This also delivers greater system integrity and if any product fails in service the rest of the installation is not affected.

They are also easy to extend and alter if required, offering full flexibility. This is a further reason to see them as a cost-effective solution, for all sizes of projects.

If a wireless monitoring system is used this will offer a fully addressable installation without any additional design input, additional cabling for key switches or installation time as it would be exactly the same as a standard self-contained design and installation except the individual products would have the wireless feature reporting to a control panel. This avoids ongoing local maintenance checks and makes it easier for the building owner to meet their legal requirements and achieve full compliance.

Batteries within each product will require periodic replacement but this would usually be only every five or so years depending on the installation conditions. If luminaires are selected that are guaranteed for five years including the batteries so giving peace of mind over a product of lesser quality where batteries may not be so reliable. Battery replacement is a simple task but planning and thought must be given to product location and access to allow these tasks to be undertaken, especially if located at high level.

Self-contained emergency luminaires can also be affected by local environmental conditions. These will of course vary, depending on the system and the location, but the batteries may be affected by especially high or low temperatures. Selecting the correct products will assist in mitigating problems in extreme conditions also selecting whether a product is maintained or non-maintained will assist in keeping the internal batteries within their specified operating temperature range.

Self-contained system advantages

  • Generally considered to be cheaper and faster to install
  • Power from a local power supply only is required
  • Standard cabling is used
  • Because each luminaire is independent, system integrity is improved
  • Installation can easily be extended with additional luminaires
  • The user is set free from special sub-circuit monitoring (reducing expenditure on specialist equipment)

Self-contained system (wireless monitoring) advantages in addition to the above

  • Centralised web-based access avoids local isolation and observation of the luminaire each month and every 12 months (to comply with legislation)
  • A wireless centralised web-based system requires no communication cabling (once again, reducing costs).

Self-contained system disadvantages

  • Environmental conditions may vary across a system and the batteries may be affected by higher or lower temperatures.
  • Potential lower light levels compared with central battery
  • Batteries will require periodic replacement.

Central battery systems

Central battery systems can be connected directly to suitably designed mains luminaires without modifications and they also operate at full light output under both ‘mains healthy’ and ‘mains failed’ conditions..

Sub-circuit monitors control the central battery power supply to each emergency circuit/product so activation occurs if the mains power fails locally.

Another advantage can be battery life. In a central system, battery life is maximised (usually lasting at least ten years).

When battery replacement is eventually required, this is usually a quick and simple operation that avoids the disruption which can be caused by having to access and change batteries in numerous fittings.

Be warned; you must visually check your central battery systems once a day, as this is the heart for the emergency lighting. It is vital that this works if any mains failure occurs (this can by the way, be very costly for the building owners to maintain).

Central battery system advantages

  • Routine testing can be easier with (only one location to consider compared to a wired self-contained).
  • The life of the battery is between five and fifteen years, depending on the type of battery.
  • Luminaires are environmentally stable in a protected environment and can operate at relatively high or low temperatures, with little effect on the battery.

Central battery system disadvantages

  • Daily checks are required.
  • Usually requires a larger capital equipment cost.
  • Fixed wiring points make future alterations/extensions more complicated and costly.
  • Higher cost for installation and wiring is due to the requirement for fire-resistant cable to each luminaire.
  • Can include poor system integrity (failure of the battery or wiring circuit at any point could result in failure in a larger part of the system).
  • Requires a central ‘Battery Room’ to house batteries and charging circuits.
  • May require an additional ventilation system.
  • Mains failure in one specific area of a building may not trigger the emergency lighting in that area without extensive sub-circuit monitoring.

Our recommendations

To put it succinctly, Phillip Payne recommends self-contained emergency luminaire systems for most, if not all projects.

This is because, with the advancements of LED and wireless technology you’ll benefit from most of the advantages of the self-contained and central battery systems, but with very little drawbacks.

That is however a very straightforward assessment and it is critically important that you take into account other factors such as the complexity and layout of the building(s) you are working with, the capacity within the building management team for monitoring and maintenance, the site environmental conditions, and more.

Access expertise

If you are unsure, then Philip Payne is here to help and guide you.
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