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A Guide to Hochiki's Linear Heat Detection Cable Systems

Hochiki's Linear Heat Detection Cable Systems

Hochiki Goes to Great New Lengths for Fire Detection

The Linear Heat Detection Cable (LHDC) System from Hochiki is designed to provide early detection of fire and overheating in circumstances where other forms of detection would not be viable, either due to inability to sustain the environment requirements or through prohibitive costs.

Extensive single zonal lengths of the specially designed LHDC may be installed with the ability to trigger alarms for hot spots  occurring on very small sections of the overall cable and, providing the LHDC has not been subjected to excessive temperatures, the alarm condition can be reset at the zonal controller.

This is particularly useful when carrying out  annual maintenance utilising the proprietary one metre Test Oven.


Provides early detection of heat over extended distances

Our LHDC Products


LHDC Applications



Fire Safety in Cable Containment

A cable tray fire, however small can cause extensive interruption and damage to building structures, processes and subsequent consequential loss. Using Hochiki’s Linear Heat Detection Cable system the outbreak of fire may be detected before there is any damage to property or equipment.

Typically, cable tunnels, risers and flats use multi-level cable trays/ ladder racking for cable containment.




Fire Safety in Tunnels

Due to the increased air flow in tunnels, traditional smoke detectors can be prone to generating false alarms, as well as inaccuracy in fire location due to environmental contamination.

The combination of Hochiki’s LHDC and interfaces works effectively in this environment and provides accurate distance location within 1 metre.


Fire Safety in Car Parks

Increasingly Linear Heat Detection Cable is being recognised as the fire protection of choice for car parks. Its unique factors mean it is ideally suited for the harsh environmental conditions that are present.

Car parks are often prone to high air flows, this coupled with exhaust fumes that are generated can cause severe problems for conventional smoke detectors. Linear heat detection cable is not affected by these conditions. Similarly it is also unaffected by environments that are prone to damp and high humidity.



Fire Safety in Recycling Plants

In recent years, several recycling plants have had fires due to various  external events and equipment failures. These events and failures have caused combustible waste products to be ignited with  catastrophic results. Recognising this, Hochiki recommend a combination of specialist products for early detection of potential and actual fires in harsh environments. 

Fast, reliable detection can reduce damage to equipment and the high cost of repair or replacement, minimise down time and consequential loss and lessen the impact for potential pollution and the possible inhalation of toxic fumes.


Fire Safety in Food Processing

Food products being transported at high temperatures have the potential risk of fire and can cause disruption to the food handling process. This can be costly in loss of product, down time and damage to machinery.

A mechanical fault can cause a build up in heat which can be sufficient to ignite a part of the machinery.  A Grain Dryer for example, is one application where a build up of husk can ignite, causing a fire and loss of product.  Linear Heat Detection Cable (LHDC) is the obvious choice  to provide early detection of fire conditions and overheating.


Fire Safety for Conveyor Systems

Conveyor Systems in general have a fire risk due to external events and equipment failure. However the flammable nature of products including the ability of some types to self ignite introduces an exceptional hazard requiring special consideration.

Being a sealed ‘Cable/Wire’ the LHDC is not prone to the water and dust problems that cause conventional smoke/heat/beam detectors to be ineffective in the rigorous environment of a conveyor housing/enclosure.




 Hochiki’s LHDC Systems 





This module is designed to monitor a zonal length of Analogue Cable for both an elevated temperature (Fire) condition, and Fault Status (Open & Short Circuit).  It operates in conjunction with a single core coaxial cable and an end of line (EOL) terminator. The module provides early warning of hot spots and fire conditions on short sections of the overall zone length. Maximum Zone length for Analogue Linear Heat Detection Cable is 500m when connected to this module.

LDM-519-LP LHDC Monitor

LHDC Analogue Cable

LHDC Analogue is a coaxial cable constructed with a copper coated steel central conductor, an inner insulation (dielectric), a tinned copper braid layer and an overall protective sheath.

The primary mechanism of heat (fire) detection is that the resistance of the dielectric, monitored between the central conductor and braid layer, has a negative temperature coefficient (NTC).

LHDC Analogue Cable






This module is designed to monitor a length of Digital Linear Heat Detection Cable (LHDC) for both fire condition and fault status (open circuit).  The unit is designed such that it may be configured to
operate in a two wire mode that emulates the operation of
conventional heat detectors.  The unit may therefore be directly interfaced with fire control panels by connection to fire zone trigger circuits or addressable interfaces.

LDM-519-DDL LHDC Monitor


This module features the same functionality as the LDM-519-DDL above, but is also certified to be fully compatible with SIL 2 certified systems.

Digital LHDC may be employed in lengths up to 2Km when using the LDM-519-DIM module. Signalling of fire and fault status is generated by means of volt free contacts.  The module has been specifically designed in a DIN rail format to allow it to be used in a variety of discrete housings or integrated multi zone control panels.

LDM-519-DIM LHDC Digital Module

LHDC Digital Cable

Hochiki’s Digital Linear Heat Detection Cable is designed to provide early detection of Fire conditions and overheating in circumstances where other forms of detection would not be viable, either due to an inability to sustain the environment requirements or through prohibitive costs.

The primary mechanism of Digital LHDC is that the inner core
insulating polymer is specially formulated such that it plasticizes at a specific temperature.

LHDC Digital Cable

Infra-Red Transit Heat Sensors


Combustible materials such as coal being transported on conveyor systems have the potential to self-ignite. Early warning protection along a conveyor susceptible to conditions of excessive heat can avoid catastrophic fire damage and substantial consequential losses.

The 5000 Series includes a range of early warning infrared transit heat sensors designed to monitor and detect ‘hot spots’ and embers from materials such as coal, biomass or recycled waste being transported on conveyor systems.




EOL Units

End Of Line (EOL) junction boxes are designed to terminate either Analogue and Digital LHDC. The EOL unit provides fault monitoring on the cable. Analogue EOL units can monitor for both open and closed circuit faults, whereas Digital EOLs monitor for open circuit faults only.



The routing of LHDC needs to consider avoiding contact or close proximity with any local sources of heat e.g. light fixings, steam pipes etc.  To this end, the correct size and type of cable gland must be used on all junction boxes and the correct cable supports/brackets must be used in conjunction with silicone or neoprene protection.

Hochiki provides a selection of clips and brackets for the correct installtion of LHD cabling.


Learn More

We have a range of LHDC Application Notes, some of which have been used to compile this page.  You can download these for free, see the PDF icons below.

If you have any Linear Heat Detection Cable queries, drop us a line using the enquiry form below.

Download our free LHDC for Cable Containment Application NoteDownload our free LHDC for Tunnels Application NoteDownload our free LHDC for Car Parks Application NoteDownload our free LHDC for Recycling Plants Application NoteDownload our free LHDC for Food Processing Application NoteDownload our free LHDC for Conveyor Systems Application Note

For almost 100 years Hochiki has led the way in the design and manufacture of innovative life safety solutions. Its leading edge commercial and industrial fire detection and emergency lighting products have acquired global acceptance as the benchmark for high-integrity and long-term reliability.

With a global sales turnover exceeding £400m Hochiki is a wholly independent, multinational, publicly listed company with over 1,500 employees working across five manufacturing plants, 32 sales offices and 18 subsidiaries.

Its ongoing commitment to manufacturing innovation ensures customer satisfaction and its production facilities in Japan, the USA and Europe offer international continuity in quality, service and supply.

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Please Note: LHDC is a specialist product range, therefore if you are an existing customer and would like access to technical specifications and/ or product pricing, please use the below form to request this information from us.


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