The LWF Blog
Fire Engineering Design and Risk Assessment – Fire Alarm Control Equipment – Part 24November 11, 2016 10:50 am
In our fire safety and risk assessment blog series for architects and building planners, we have been looking most recently at fire alarm control equipment including sounders, sound levels, voice alarms and how these should be used in differing environments. In this blog, we will look at how a fire alarm control system can be used to activate other safety measures and later, how important appropriate cabling can be.
Although, in the past, it was usual for fire alarm systems to simply detect fire, indicate the area and sound an alarm so that the occupants of the building could evacuate in a timely manner, it is increasingly common that the control and indicating equipment is used to undertake other tasks which can be automated, in case of fire.
Lifts which are not for use in a fire situation can be automatically disabled, public address announcements can be made, smoke and fire doors can be closed to avoid the spread of fire and plant and machinery can be shut down as is safe and appropriate.
In a large building, it may be that there are several fire alarm panels in different areas, as this can avoid having excessive cabling installed to connect all manual call points, alarm sounders and detectors back to one central control point. Where this is the case, the panel will need to communicate with the other panels in order to send signals. In addition, communications can be sent from the control point to other building management systems, radio-paging systems or off-site monitoring stations.
These days, most fire alarm control systems work with the ability to communicate with computer systems so that information can be displayed on the PC screen and the events catalogued so that they can be accessed or printed off.
Cabling for fire alarm systems can be divided into two different types – the cable which must continue to function even if a fire situation is ongoing, and cable which can be allowed to fail, having first done its duty.
For instance, cabling which serves the power supply and provides links to alarm sounders and remote communication centres should be fire-resistant up to half an hour, while cables to smoke or heat detectors and failsafe cables to auxiliary devices such as door release devices can be allowed to cease operation after they have served their purpose.
Suitable cables for resisting fire include mineral-insulated copper-sheathed cable, commonly abbreviated to MICC, which complies with BS 6207, in addition to soft skin types complying with BS 7629. Other types of cabling can be used and the standards are laid out in BS 5839:1, section 26.
The installation of such cables is covered by BS 7671 and includes information on segregation of cables from other systems. There are recommendations too, relating to electrical interference, laid out in BS EN 50081 and BS EN 50082.
In our next blog, we will give an overview of radio-based systems and power supplies. 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 for over 25 years to produce innovative and exciting building projects. If you would like further information on how LWF and fire strategies could assist you, please contact Peter Gyere on 020 8668 8663.