The LWF Blog

Fire Safety for Facilities Management Personnel – Fire Detection & Fire Alarms – Part 197

April 17, 2023 11:23 am

Lawrence Webster Forrest (LWF) is a specialist fire engineering and fire risk management consultancy whose aim is to give information on best practice in fire safety for facilities management personnel through this blog series. In part 196, LWF discussed voice alarm systems. In part 197, we begin to look at the wiring of a fire alarm system.

It is important that the wiring to alarm sounders, any kind of detector and all call points must be monitored by the control equipment. If an open circuit or short circuit is detected a fault warning is generated and action can be taken. While it is important to have this facility in order to repair any faulty wiring, the cable type and protection should be such that it is not susceptible to mechanical damage to minimise the potential for the system not working as intended.

Fire damage to cables would disrupt the fire alarm circuits, resulting in failure. It is essential that this is avoided and so all fire alarm circuits, including the mains power supply circuit serving the control equipment, should be wired in fire-resisting cables. A good standard is a mineral-insulated copper sheathed cable or proprietary ‘soft skin’ fire-resisting cables.

BS 5839-1 Fire detection and fire alarm systems for buildings – Code of practice for design, installation, commissioning and maintenance of systems in non-domestic premises classifies two levels of performance of fire-resisting cables – standard and enhanced. The performance levels reference testing detailed in BS 8434-1 and -2.

BS 5839-1 recommends cables of enhanced fire resistance only for unsprinklered buildings with the following characteristics:

• They are greater than 30 metres in height, or
• Where an evacuation may have four or more phases, or
• Where the evacuation of areas remote from the fire might be unnecessary (e.g. in healthcare buildings or certain large industrial sites).

It also acknowledges the potential need for cables of enhanced fire resistance where indicated in certain fire engineering solutions.

In part 198 of this series, LWF will begin to look at radio-linked fire alarm systems, i.e. a fire alarm system where the components are linked by radio rather than requiring wiring. In the meantime, if you have any queries about your own facilities or wish to discuss this blog series, please contact LWF on freephone 0800 410 1130.

 

Lawrence Webster Forrest is a fire engineering consultancy based in Surrey with over 35 years’ experience, which provides a wide range of consultancy services to professionals involved in the design, development and construction and operation of buildings.

 

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.