Circuit isolators

Preamble

This document explains what a "circuit-isolator" is and how they can be used with the Firepoint-2 fire alarm equipment.

What is a circuit isolator?

A circuit isolator is a small wall-mountable box that contains a set of input terminals and a set of output terminals.  When the fire alarm is operating normally the circuit isolator does more or less nothing.  However if a short-circuit occurs on the output side of the isolation module then the isolator will quickly disconnect that portion of the fire alarm circuit until the short circuit is removed.

The benefit of a circuit isolator is that a short circuit can be contained within a subsection of the fire alarm cabling and only the fire detectors that are on the same section of cable will stop operating; all the other fire detectors on the other cable sections will continue to operate normally.

How should circuit isolators be used?

The way to best use circuit isolators depends on the way the building is laid-out and how the cable has been run around the building.  The arrangement of the rooms and other spaces in the building will often determine how the fire zones should be arranged.  Also the position of corridors, stairwells, ductways, lift shafts and so on will probably determine the easiest way to run the cable.  Finally you will also need to refer to the building regulations, fire alarm standards or architects notes before making in final decision.

However, in general you will be aiming to divide the fire detectors and alarm sounders into groups of devices that share a section of cable.  That cable section will then be connected to a circuit isolator and the other side of the circuit isolator will be connected to a common cable that joins the control panel to all of the isolators.

Further information

Diagrams showing the connections and basic use of the circuit isolator are available on an Illustrated information sheet for the circuit isolator.  The sheet is in “PDF” format.