The LWF Blog

Fire Safety Engineering for Design – Fire Detection & Alarm Systems – Part 148

September 4, 2023 1:51 pm

LWF’s Fire Safety Engineering blog series is written for Architects, building designers and others in the construction industry to highlight and promote discussion on all topics around fire engineering. In part 147, LWF considered the formal recommendations for zoning of fire alarm systems as per BS 5839-1. In part 148, we look at the necessary recommendations for fire alarm system designed for buildings outside British Standards.

In circumstances where a fire alarm system is being designed for a building outside British Standards recommendations, the system should be zoned to satisfy the following:

  • Minimise search areas within a zone by limiting their geographic area
  • Any fire zone that passes through features such as staircases should be individual zones
  • High risk areas should be individually zoned
  • The layout and numbering of zones should be approached in logical sequence

Each device in an addressable or analogue addressable fire alarm system has a numerical address code and devices are wired in a loop arrangement. Guidance on the number of devices that can be accommodated on a loop can be obtained from the manufacturer, as well as the length of one loop. A loop can cover several detection zones.

Short-circuit isolators are placed between zones within the loop, so that a fault in one zone doesn’t affect devices in another. In the case of addressable systems, devices can be assigned at the control panel into separate zones.

With addressable or analogue addressable systems, the detector or manual call point can be shown by the use of an alphanumeric display, however, it is important that the zone in which the detector or manual call point has operated is also displayed. This is typically indicated by an LED light.

A zonal identification diagram or chart should be mounted by the control panel. BS 5839-1 requires that a plan of the building is displayed and so the use of a mimic diagram provides a suitable means for zone identification, fulfilling both requirements. While the BS 5839-1 stipulation wouldn’t be a requirement in a building’s fire alarm system not covered by British Standards, it remains good practice to fulfil this stipulation.

In part 149 of LWF’s series on fire engineering, we will discuss manual call points, which are often referred to as break-glass units. In the meantime, if you have any questions about this blog, or wish to discuss your own project with one of our fire engineers, please contact us.

Lawrence Webster Forrest has been working with their clients since 1986 to produce innovative and exciting building projects. If you would like further information on how LWF and fire strategies could assist you, please contact the LWF office on 0800 410 1130.

While care has been taken to ensure that information contained in LWF’s publications is true and correct at the time of publication, changes in circumstances after the time of publication may impact on the accuracy of this information.

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