An Overview of Fire Alarm Systems
Fire alarm systems are essential for the adequate detection and warning of a fire situation within commercial and residential premises. The detection, visual and audible requirements of a fire alarm system are dependent on the layout and use of the building. It is due to the diversity of these applications that fire alarm panels and related accessories have been developed to meet these varying needs.
Who specifies the system required?
According to the Regulatory Reform (Fire Safety) Order 2006, businesses and organisations must have a fire risk assessment carried out by a competent person. The competent person can be someone from within the organisation, or, many choose to nominate a third party Fire Risk Assessor; ensuring they are fully qualified and have read and understand the current legislation. The fire risk assessment is to be completed on-site and a report of the recommendations is to be documented.
Types of Fire Alarm Panel
There are three main types of fire alarm panel available. The information below briefly describes each panel and the differences between the three: Most advanced fire alarm panel available "Cause and effect" feature - offers greater flexibility for detection, activation and audible and visual warning Ideal for more complex or high risk applications Devices are connected using a "loop" system - multiple loops panels available Typically supports up to 126 devices per loop - detectors, call points, sounders and beacons Each device is given an individual "address" Identifies the exact device that has been activated - saves time for the "appointed person" and the fire services in the event of an emergency Typical applications: hospitals, hotels, large office premises, shopping centres
Wiring Diagrams
The panel is the "hub" of the fire alarm system. This is where the system can be programmed according to the users' requirements, monitors device operation, indicates if there is a problem and identifies where the fire alarm system has been activated
Conventional (Four Wire)
Sounders and beacons are installed on a separate circuit to the detectors and manual call points
Two Wire
Detectors, manual call points, beacons and sounders can be installed on the same pair of supply wires - no need for separate sounder circuits
Addressable
Detectors, manual call points, beacons and sounders are connected using a loop system - the loop can be split into zones
Zones
At the planning stage, a premise may be divided into different sections, allowing the fire alarm system to become more manageable. These divided sections are called zones. Zones are particularly important for conventional fire alarm systems, as this enables the panel to identify where the system has been activated.
Loop
Addressable fire alarm panels have one or more loops used to connect devices to the panel. The single wire connection leaves and returns to the panel in a complete loop.
Detectors
Available in smoke, heat, carbon monoxide (CO) and multi-sensor configurations acting as the sensors for the fire alarm system. Detectors do not have built in sounders and they require a base in order to be recognised by the fire alarm panel
Manual Call Points
Typically located within the exit routes of the building. The device allows the fire alarm system to be activated manually, should a fire be identified before a fire detector has been triggered
Beacons
Provides visual indication that the fire alarm system has been activated. Beacons are not required for all areas of the premise; however they enable compliance with the Disability Discrimination Act.
Sounders
Provides audible warning that the fire alarm system has been activated. These are available as standalone devices or built into the detector base. These can be installed in areas where a detector may not be required.
Repeater Panels
Multiple repeater panels can be installed as part of the fire alarm system. These allow the indicators and functions of the main fire alarm panel to be accessed from different areas of the premise
Relays
Relays allow connection to external devices.
Isolator
Isolators are required at intervals on the fire alarm system. In the event of a short circuit, isolators ensure that only the section between the isolators will be affected. When the short circuit is removed, the isolators will automatically restore power to the system.
Cause and Effect
Related to addressable fire alarm systems, cause and effect refers to the programming of a fire alarm system, where the output or result of an input activation can be changed according to the requirements of the application e.g. double-knock.
Double-Knock
The fire alarm system is programmed to identify and only go into full alarm mode when two devices from different zones or the same zone are activated.
Phased Evacuation
A fire alarm panel can be configured to activate sounders in different parts of a building to alarm in a staged (or phased) sequence. The sounders in rooms where a fire is detected are set to alarm first..