Cartridge Heaters

Cartridge heaters are precision-engineered heating elements designed to deliver reliable, high-density heat in confined spaces. At Under Control, our cartridge heaters range is built to meet the demanding needs of UK industrial, mould-tooling, and manufacturing applications. Whether you need a heater cartridge for a mould, a die, or platen, or you're repairing existing equipment, our cartridges are manufactured to tight tolerances, built for longevity and engineered for excellent thermal performance.

Our selection includes a variety of sizes, wattages and terminations - from compact 6.5 mm and 10 mm diameters to high-watt density options and NPT-threaded immersion designs. Each cartridge heater is made to be pushed directly into pre-drilled holes, minimising air gaps and improving thermal transfer. With fast UK dispatch and expert support, Under Control makes it easy to order the right heater cartridges for your process, reducing downtime and boosting efficiency.

Key Features & Benefits

High Watt Density Options - Delivers concentrated, powerful heating where you need it most.
Wide Range of Sizes - Available in multiple diameters (e.g., 6.5 mm, 10 mm, 12.5 mm, 16 mm) and imperial equivalents to suit a broad variety of applications.
Long Service Life - Constructed from high-grade stainless steel sheaths and NiCr conductor for durability and longevity.
Push-Fit Installation - Designed for easy insertion into drilled cavities, reducing installation complexity.
High Temperature Capability - Some cartridges are engineered to operate at temperatures up to 800 °C for extreme applications.
Customisable Leads and Zones - Options for fibreglass leads, thermocouples, segmented heating zones, and more.
Efficient Energy Use - Efficient heat transfer minimises lost energy and improves thermal responsiveness.

How These Products Work

Cartridge heaters operate on the principle of resistive (Joule) heating: electrical current flows through a resistance wire (typically NiCr), which heats up. This resistance wire is tightly packed with insulation material and enclosed in a stainless-steel sheath. The resulting heat is then transferred directly to the metal surface into which the heater is fitted, thanks to a snug, push-fit installation which minimises air gaps.

Depending on the design:

Standard cartridges produce uniform heat along their heated length.
High-density cartridges pack more wattage per unit volume, achieving higher temperatures.
Immersion (NPT-threaded) cartridges can be screwed into tanks or vessels to heat liquids or gases.
Optional thermocouples or integrated temperature sensors allow for precise temperature monitoring and control.

Because of their construction, heater cartridges provide very efficient, focused, and controllable heat in a compact form factor.

Ideal Use / Application

Cartridge heaters from Under Control are particularly suited for:

Heating dies, moulds and platens in injection-moulding, stamping or press machines.
Metalworking and tooling applications where precise, localized heating is required.
Industrial heating systems, such as heating blocks, jigs or assemblies.
Immersion heating, using NPT-threaded cartridges for liquids or gases in vessels and tanks.
High-temperature applications in lab equipment, test rigs or specialised manufacturing.

These heaters are ideal when you need a compact, reliable and high-performance heat source in tight or confined assemblies.

Important Considerations & Safety Notes

Correct Size is Critical: Always choose a cartridge heater that fits snugly into the drilled hole - too much air gap can cause overheating and eventual failure.
Voltage & Watt Density: Ensure the voltage and watt density are appropriate for your application. Incorrect specifications can significantly reduce heater life.
Moisture and Contaminants: Moisture ingress or dirty environments can reduce insulation integrity. Use sealed or moisture-resistant variants if your application demands it.
Mounting and Leads: Secure leads and avoid excess vibration or movement, which can stress the heater and degrade performance over time.
Thermal Cycling: Frequent, rapid heating/cooling cycles can stress the resistance wire. Choose the right watt density and consider integrated thermocouples to manage cycling.
Qualified Installation: Always have a qualified technician or engineer install or replace cartridge heaters, especially in critical industrial or high-power applications.

Customer Reviews

⭐⭐⭐⭐⭐

"Fantastic.

Used in a dimplex towel rail and about a tenth of the original cost."

⭐⭐⭐⭐⭐

"Heating cartridge

Have ordered these for many years now. excellent quality & great prompt service from Under Control."

Frequently Asked Questions (FAQs)

What are cartridge heaters used for?

Cartridge heaters (or heater cartridges) are used to apply precise, localized heat to metal components such as dies, molds, platens, tooling and industrial assemblies.

How do I choose the right cartridge heater?

You should match diameter, length, wattage, voltage, lead type, and any required features (e.g., thermocouples). It’s also important that the heater fits snugly to avoid overheating.

Can cartridge heaters be used to heat liquids?

Yes - via immersion (NPT-threaded) versions. But they must be designed for safe operation in liquids; standard push-fit cartridges are generally not optimal for fluid heating.

Why do cartridge heaters fail prematurely?

Common reasons include poor fit (air gaps), moisture ingress, incorrect watt density, temperature cycling, and mechanical stress.

Can I control the temperature of a cartridge heater?

Yes - many cartridges come with integrated thermocouples or can be paired with external temperature controllers to regulate heating and prevent overheating.

Ready to power your precision heating projects?
Explore our full range of cartridge heaters, or contact our specialists for help choosing the exact heater cartridge to meet your exact requirements.