Linesense Digital Linear Heat Detection (LHD) cable is a simple and reliable product providing continuous uninterrupted detection along its length.

black pdf icon


The sensing cable is formed from a pair of twisted steel conductors each with temperature sensitive insulation and then an overall outer sleeve. When the temperature sensitive insulation reaches it’s predetermined alarm temperature the two conductors short together providing the digital alarm signal.

The cable can be connected to any unit capable of monitoring a switched or digital alarm signal, i.e. Conventional fire panel, addressable switch monitor unit or PLC. The fire detection capability can be enhanced when the LHD is used in conjunction with the Digital Location Interface (DLI).

LHD cable is classified as a “simple device” and so with the use of suitable Intrinsically Safe (IS) barriers to limit the energy to a safe level, it can be used in hazardous areas.

The LHD cable can be cut to length as required and with it’s ease of installation and low maintenance it provides a cost effective solution where project expenditure requires to be kept at a minimum.

Having a fixed alarm temperature, the operation of the digital LHD is unaffected by changes in the ambient temperature. The Linesense Linear Heat Detection cable has a wide range of Alarm temperatures 68ºC to 240ºC

Simple switch / digital alarm operation Conveyors/bearing protection
Continuous uninterrupted sensing along the total length of the element Escalators, moving walkways
Fixed alarm temperature. Unaffected by changes in ambient temperature Cable tunnel / tray protection
Compatible with switch monitoring units and conventional alarm panels Road and rail tunnels
Suitable for use in Hazardous areas using safety barriers Road and rail motor compartments
wide range of alarm temperatures 68ºC to 240ºC (155ºF to 464ºF) Electrical switchgear & transformers
Simple maintenance-free installation Refrigerated rooms and cold stores
Small diameter and bend radius Building fascia's, exteriors under eaves
FM Approved Motor and pump overheat detection
  Dirty and dusty environments


Digital linear heat detection cable provides continuous uninterrupted detection along its entire length, this permits a spacing of 10.6m between runs on a flat ceiling. The cable should run the full length of the room to ensure coverage into the corners. Under pitched roofs an extra 1%, per degree of roof angle applies for LHD within 150mm of the apex.

Linear heat detectors should be installed no closer than 25mm and no further than 150mm from the ceiling. Maximum zone size should not exceed 2000 square meters.

Values according to BS5839 Part 1, other codes and regulations may differ.

lhd area diagram

Alarm temperature : 68°C (155ºF) Nominal
Max amb temperature : 45°C (113ºF)
Min operating temperature -40°C (-40ºF)
Min installation temperature -15°C (5ºF)
Pt No. 51100-068  
Alarm temperature : 85°C (185ºF) Nominal
Max amb temperature : 45°C (113ºF)
Min operating temperature -40°C (-40ºF)
Min installation temperature -15°C (5ºF)
Pt No. 51100-085  
Alarm temperature : 105°C (221ºF) Nominal
Max amb temperature : 70°C (158ºF)
Min operating temperature -30°C (-22ºF)
Min installation temperature -0°C (32ºF)
Pt No. 51100-105  
Alarm temperature : 180°C (356ºF) Nominal
Max amb temperature : 105°C (221ºF)
Min operating temperature -40°C (-40ºF)
Min installation temperature -0°C (32ºF)
Pt No. 51100-176  
Alarm temperature : 240°C (464ºF) Nominal
Max amb temperature : 200°C (392ºF)
Min operating temperature -50°C (-58ºF)
Min installation temperature -20°C (-4ºF)
Pt No. 51100-240  

See individual datasheets for further details.