LGM Products Ltd

Heat Sensing Cable Basics

What are heat sensing cables?

Heat sensing cables, as the name suggests, are very special cables designed to sense heat or sudden increases in temperature. They are designed to be used in fire alarm systems when conventional heat detectors are not suitable. There are two types of heat sensing cable: Analogue and Digital.

Where are heat sensing cables used?

There are many places where heat sensing cable can be used effectively. Here are some examples:

Power stations	Coal Conveyors Power cable tunnels Cable Trays
Vehicles	Engine bays of earth moving vehicles Heavy goods vehicles Military vehicles
Railways	Engine Locomotives Signal Cable Trays
Ships	Car ferry vehicle decks Engine rooms
Petro - Chem	Floating roof tanks

What is the difference between Analogue heat sensing cable and Digital heat sensing cable?

Analogue heat sensing cable senses significant changes in temperature. An electronic controller connected to the cable monitors the change in temperature. The controller can be adjusted for the length of cable being used and the approximate temperature at which an alarm is required. The alarm temperature is called the 'set point'. The set point is variable being much higher for when a short length of cable gets hot (high set point) and lower when the cable is much longer (lower set point), therefore the controlelr will raise an alarm when there is a particularly hot small section of cable at or above the set point. If a much longer length of cable is heated, the controller will raise an alarm when the cable reaches a temperature somewhat lower than the high set point. The variation in set point between long and short lengths of cable can be calculated from information in our product manual. Analogue heat sensing cable will reset itself after an alarm when the cable has cooled down unless it has been permanently damaged or destroyed by the heat.

Digial heat sensing cable provides an electrical closed contract when the cable reaches a pre-determine temperature. In other words nothing happens until the cable, or part of the cable, reaches a certain temperature, then at that temperature the cable acts like a closing switch on. For further information on the different temperature settings availble please go to the Fixed Temperature section of the Heat sensing cable menu. Digital cable cannot be re-used. Once it has gone into alarm it must be replaced.

Basic DOs and DON'Ts

-DO use analogue cable when it is important to detect a fire as soon as possible.

-DO use analogue cable when a fire is unlikely to give off smoke in its early stages e.g. overheating cables.

-DO use digital cable when a simple straightforward temperature alarm is required.

-DO use digital cable in high temperature environments.

-DO NOT use analogue cable if the normal ambient temperature is likely to be above 55 °C e.g. in engine bays of vehicles.

-DO NOT use analogue cable if sudden changes of temperature can be expected under normal working conditions.

-DO NOT use digital heat sensing cable when sophisticated and fault monitoring is required.

-DO NOT use digital cable when it is likely to be regularly 'flexed' or subjected to frequent bending in the normal course of work. This is because digital cable is much stiffer and less flexible than analogue cable.