Linear Heat Detection
Typical Detecting Temperature | 68 °C[1] (building) | 180 °C (plant) |
---|---|---|
Maximum Length | 3000m[1][2] | |
Linear Heat Detection (LHD) (also known as Linear Detection Wire or Linear Heat Detection Cable or Linear Heat) is a very commonly used method of fire detection. It can detect a fire anywhere along the length of the cable, and can be of lengths in excess of a kilometer.
Applications can range from building fire alarm systems to mobile plant machinery.
Operation
Linear Heat Detection (LHD) cable is essentially a two-core cable terminated by an end-of-line resistor (resistance varies with application). The two cores are separated by a polymer plastic, that is designed to melt at a specific temperature (commonly 68 °C for building applications[1]), and without which causes the two cores to short. This can be seen as a change in resistance in the wire.
There are a limited states the LHD cable can be in:
- Open-circuit - Effectively an infinite resistance
- Normal Operating Condition - Apparent resistance will be the same as the end-of-line resistor
- Fire Detection - Resistance of the Linear Heat Cable to the short circuit
See also
1515
References
- 1 2 3 "Linear Heat Detection cable information" (PDF). Retrieved 26 April 2014.
- ↑ "Safe Fire Detection, LHD Information". Safe Fire Detection. Retrieved 26 April 2014.