Fire Safety Product Selection is Critical
With the introduction of the Regulatory Reform (Fire Safety) Order and changes to the British Standards, there is now a requirement for both companies and personnel working within the fire industry, to be not only competent but be able to prove this competence. Keeping up with legislation and building regulation changes, as well as new technological advances is a job in itself and could mean the most appropriate product is not always installed. Here Gary Walker, Newlec Fire and Security category manager takes a look at the changes within the sector and the product choices available:
During the past two years fire alarm systems have been going through a period of significant change, but there are generally three types of system:
- conventional;
- Bi–wire; and
- addressable.
Conventional
For sounder circuit continuity monitoring to function effectively, sounder circuits must be wired in a single radial circuit…
Conventional two wire systems use end of line monitoring or active end of line modules with separate sounder circuits, and in commercial buildings the established conventional system revolves around dividing the building into a number of zones, where the detectors and call points within each zone are then wired on dedicated circuits.
In the event of a detector callpoint being activated the panel is able to determine which circuit contains the triggered device and thereby identify which zone the fire is coming from. In addition to the detection circuits there is also a need for separate circuits for alarm annunciation, as devices such as sounders and beacons need to signal the existence of a fire to the building’s users.
For sounder circuit continuity monitoring to function effectively, sounder circuits must be wired in a single radial circuit — spurs and tees are not permitted. Every conventional fire panel will have two or more sounder circuits, (depending on the panel manufacturer this could have two or four). Normally however, there will be less sounder circuits than detection circuits, so it will be necessary to provide audio coverage for more than one zone, therefore increasing the complexity and cost of the installation by forcing the sounder wiring to follow a different route to the detector wiring.
Start of pageBi–wire
Bi–wire or two–wire (as it’s also known) fire alarm systems allow detection devices and sounders to be wired on the same two core cable.
Through advancing technology the way forward involves a new method, which is appealing to installers as it enables a much quicker installation time. Based on conventional technology it incorporates additional functionality to enable both the detectors and the sounders for each zone to be wired on a single common circuit. Bi–wire or two–wire (as it’s also known) fire alarm systems allow detection devices and sounders to be wired on the same two core cable.
Even though the panel continually powers the sounders, the additional control functionality within each one enables them to be activated only in the event of a fire alarm condition. By combining the detection and alarm annunciation wiring into a single circuit, both time and cabling can be greatly reduced. Although adding Bi–wire technology to the detectors and sounders slightly increases equipment costs, this is normally more than offset by savings in installation, resulting in a reduced total cost.
When it comes to smoke detectors these are also seeing a period of transition thanks to the enforcement of new EU regulations. Ionisation smoke detectors contain small ionisation air molecules that have a high sensitivity to fires that produce small smoke particles. Despite them having been the favoured option for a number of years, these are now being phased out and will have disappeared completely by 2009. This change to the optical only system is to comply with The Restriction of Hazardous Substances (RoHS) and WEEE regulations, as the ionisation models contain small levels of radiation material and so are more difficult to dispose of safely and makes recycling impossible.
Photoelectric smoke detectors are activated when light from a pulsating light source is reflected off the smoke particles onto a light sensor, triggering the alarm. These smoke detectors are particularly well suited to detecting slow–burning, smouldering fires that produce smoke with large particles and have been taking over from the ionisation models for some time.
In addition to these, self check detection devices are new to the market and work like ordinary conventional detectors, but incorporate additional circuitry to constantly monitor their own status and raise an alarm, both locally and at the fire panel in the event of a fault. Self check detectors represent a major innovation, greatly enhancing the integrity of conventional fire alarm systems. With traditional systems, the monitoring element is within the control panel, this checks that all detectors are in place and the wiring is intact, they do not however verify that the detectors are actually working. The new self check range of detectors constantly monitor themselves and raise an alarm in the event of failure.
Start of pageAddressable
…addressable analogue systems offer point identification. This reduces search time, detection devices, sounders, repeater fire alarms panels…
For a more advanced option, which incorporates similar technology to the Bi–wire method, addressable analogue systems offer point identification. This reduces search time, detection devices, sounders, repeater fire alarms panels, and an array of modules all connected on two wires in a loop configuration giving optimum integrity. With these systems you can generally connect up to 125 devices per loop, however dependant on the panel manufacturer some systems can exceed this number. Most addressable systems can also be networked, in some cases this can be advantageous in reducing cabling and system integrity.
The technology within fire safety products continues to advance, offering the contractor even more choice in how to install the best products with the minimum installation time, and lessen the potential for false alarms or problems. When installing any fire safety product the key factor has to be quality and in an emergency such as a fire, their integrity is tested to the full, which is why all products must be manufactured in an ISO 9001 facility and tested and certified to BSEN54 parts 2 and 4. Finally, it is essential to understand the variety of products available, so the most appropriate is used and that all components are fully compatible with each other.
Start of page
Newey & Eyre and Neweys Online are brands of Rexel UK Limited, a
