How to wire a conventional fire alarm system?

Fire alarm installation in the UK is regulated by the British standards BS5839­1. This standard explains how a fire alarm system should be designed and installed in the UK. In order for you to work with fire alarm systems, you should have the right electrical qualifications, experience and you should also be a competent fire alarm installer.

The below article explains how a conventional fire alarm panel is wired. In a conventional fire alarm system, parallel circuits are used with detectors to identify fire and control it, the buildings is subdivided into different zones and a dedicated circuit will cover each zone. In most cases three core fire rated 1.5mm cable is used for each circuits and for the optimal use of the cable most manufacturers advise to use screened cable.

A fire rated cable will be run from the panel connecting live, neutral and earth to detector live, neutral and earth. This process will continue till the last detector of that circuit and an end of line resistor or capacitor will be used to close the circuit.

An earth fault loop impedance should be tested at the furthest point of each circuit. Every detector will have loop in and loop out and detector fault is monitored via circuit. In order to monitor the detector fault, the connection between two terminals in a detector is done via diode. An end of line resistor or capacitor is installed at the end of the line to monitor the circuit.

Apart from detector circuit you will have other circuits such as sounder circuit, output circuit, auxiliary input, auxiliary output, fault input, fault output and etc. Enhance cable should be used for main and any output circuit. Main isolator switch should be used to isolate the main power to the panel and it should be only operated by authorised personals.