A linear heat detection cable protects long, narrow or harsh areas with one continuous sensor. Instead of many point detectors, the cable itself senses heat along its whole length. If any section reaches a set temperature, the system raises an alarm.
This makes the cable a strong choice where smoke detectors struggle. Also, dust, moisture, cold, corrosion and strong airflow often cause problems for point detectors. A robust cable simply ignores them. In this guide, we explain how it works, compare the main cable types and show where it fits best.
How does a linear heat detection cable work?
The system has two main parts. First, a sensor cable runs through the protected area. Second, a controller or interface module monitors the cable and signals the fire alarm panel.
The cable holds two conductors. A heat-sensitive polymer separates them, or the cable measures a change in resistance. When heat reaches the rated level, the cable reacts. The controller sees this change and reports a fire or a fault. Because the whole cable acts as the sensor, heat anywhere along its length triggers the alarm.
Digital and analogue linear heat detection cable types
Two cable families are common. Also, digital cables work like a long switch. Analogue cables measure temperature continuously. The table below shows the main differences.
| Feature | Digital (switch type) | Analogue (temperature sensing) |
|---|---|---|
| Principle | The insulation softens at a fixed temperature and the conductors touch | The resistance changes steadily with temperature |
| Alarm level | One fixed temperature | Adjustable thresholds, often with a pre-alarm |
| After an alarm | The damaged section usually needs replacing | The cable can often reset after it cools |
| Fire position | Zone level on most systems | Often reported as a distance along the cable |
| Typical use | Simple, cost-effective protection | Demanding or critical routes |
Always check the data sheet of the cable you plan to use. Ratings and features differ between products.
Where does a linear heat detection cable work best?
The cable fits any route where heat is the most reliable sign of fire. Common examples include:
- Conveyor belts in ports, mines and logistics centres, where friction can start a fire.
- Cable trays and cable tunnels, where a cable fault can spread fire quickly.
- Road and rail tunnels, where airflow and fumes confuse smoke detectors.
- Cold stores and freezers, where low temperatures affect other detectors.
- Car parks, silos and dusty process plants, where dirt blocks sensing chambers.
These applications appear often in manufacturing and industrial sites and in infrastructure and transport projects.
Design points for a linear heat detection cable
Good design keeps the system reliable for years. Keep these points in mind:
- Pick the right temperature rating. It must sit comfortably above the highest normal temperature in the area.
- Route the cable close to the heat source. Use the clips and spacing that the manufacturer recommends.
- Protect the cable from damage. Mechanical impact and chemicals can shorten its life.
- Respect the maximum zone length. Each controller supports a limited cable length.
- Follow the standards. EN 54-14 guides system design, and EN 54-22 covers resettable line-type heat detectors. Local codes may add rules.
Finally, test the system after installation and again during every service visit.
Benefits and limits of heat sensing cable
Benefits
- Works in dust, moisture, cold and corrosive air.
- Replaces many point detectors with one cable.
- Has no moving parts, so maintenance is simple.
- Covers routes that are hard to reach with other detectors.
Limits
- It senses heat, not smoke, so it reacts later to smouldering fires.
- The heat has to reach the cable, so routing matters.
- It does not replace smoke detection in large open ceilings.
For very early warning in clean, high-value rooms, aspirating smoke detection is a better fit. Many projects combine both technologies.
Key takeaways
- A linear heat detection cable senses heat along its whole length.
- Digital cables act like a switch, while analogue cables measure temperature.
- It works well in dust, moisture, cold and corrosive air.
- It senses heat only, so combine it with smoke detection where early warning matters.
Frequently asked questions
Is a heat sensing cable the same as a smoke detector?
No. The cable senses temperature along its length, while a smoke detector senses particles in the air. Heat detection reacts later to a smouldering fire but ignores dust and steam.
How long can a sensor cable be?
The maximum length depends on the cable type and the controller. Some zones cover a few hundred metres, and larger systems link several zones. Always check the data sheet.
Can the cable work outdoors or in hazardous areas?
Many cables suit outdoor and harsh locations. In explosive atmospheres you need the correct certified interface equipment, so always confirm the certification first.
Kidde Global Solutions supplies AlarmLine cable for industrial, transport and infrastructure projects. Also, read more on our linear heat systems page. You can also learn the basics of heat detectors on Wikipedia.