Cartridge / Rod Heaters


The Right Thermal Solution For You

Cartridge heaters are versatile and can be configured for optimized performance to a specific application. As an experienced cartridge heater manufacturer, our goal at Nexthermal is to build your custom cartridge heater specifically to the requirements of your application. Having the right cartridge heater is one of the most cost-effective process improvements you can make. We want to know more about your application, challenges, and goals. Combining your experience with Nexthermal’s thermal transfer expertise will provide you with the solutions you need.

Whether your needs involve cartridge immersion heater products, electric rod heater products, cartridge heater elements, or other custom cartridge heaters in the medium or high watt density range, we have you covered. Call us today at (269) 964-0271 or email to learn how we can serve your custom cartridge heater requirements.


High vs. Medium Watt Density

High Watt Density

Nexthermal High Watt Density Cartridge Heaters are fast responding and can be precisely profiled to help your equipment operate at peak performance levels. Nexthermal has developed industry-specific algorithms that calculate distribution profiles for plastics, rubber, packaging and other applications. Nexthermal High Watt Density Cartridge heaters core construction and available options deliver the performance and durability you need.

Both can be manufactured with an internal J or K Type thermocouple.

These are the cost-effective alternative for cartridge heaters greater than 8” long with watt densities below 65 watts per square inch. Medium watt density cartridge heaters have the resistance wire in the center of a ceramic core. Medium watt density heaters are swaged using the same method as our high density cartridge heaters. Medium watt heaters are every bit as durable as high watt density heater with the additional advantage of fewer electrical connections on multi core (longer) heaters. Though construction will differ between medium watt density and high watt density cartridge heaters, both are swaged heaters manufactured using advanced materials.

Both can be manufactured with an internal J or K Type thermocouple.

Distributed Wattage

Nexthermal can design a cartridge heating element using distributed wattage to correct the temperature curve, resulting in a more uniform heat profile. In the figure below, you can see how the increased wattage in the end zones creates a more uniform temperature curve.

Distributed Wattage

Performance Options

Distributed Wattage

Nexthermal has developed industry-specific winding profiles to improve thermal profiles for packaging, rubber, and injection molding. We have also successfully developed OEM-specific winding profiles to compensate for challenging heater placement.

For applications that require wash down, have high amounts of humidity in te ambient air, or have machining oil nearby, Nexthermal offers built-to-order options to deliver moisture resistance at your operating temperature.

Building a heater that lasts longer can make removal more difficult when a heater must be replaced. Removal labor often costs more tha nthe heater itself. Nexthermal's in-house anti-seize coating is a cost-effective option that can be added without impacting delivery.

Nexthermal offers knock-out tabs and other removal aids that allow you to quickly and confidently remove a heater when it is time to replace it. Knock out tabs are recommended when you are installing the heater in a through bore that's prone to oxidation.

Nexthermal has redesigned the right angle exit with flat sides making it possble to use a wrench to precisely position the lead exits and break oxidation bonds when removing a heater.

The right angle block has flat sides and substantial material to provide the strength needed for highly-corrosive environments (such as die casting) where the heater sheath can be bonded to the bore.

For applications requiring a specific insertion depth, or must be held in place, Nexthermal offers standard flanges for most diameters. We can also design special flanges for your application. NPT fittings can be added to your cartridge heater.

Nexthermal's standard tolerance of ±0.002" compares favorably to other cartridge heaters. If heat transfer is critical to your application, Nexthermal offers premium centerless grind tolerances that are ±0.0008"/ Designed to fit nominal cores.


Available Diameters





Ø Tolerance

Max. Size

Min. Size



















































1 & 1/4"





* Special Note for 1/8″ Heaters: Teflon Plug and Leads only. Thermocouples unavailable.




Ø Tolerance

Max. Size

Min. Size

6.2 mm

6.18 mm


6.14 mm

6.5 mm

6.48 mm


6.44 mm

7.0 mm

6.98 mm


6.94 mm

8.0 mm

7.98 mm


7.94 mm

9.0 mm

8.98 mm


8.94 mm

10.0 mm

9.98 mm


9.94 mm

11.0 mm

10.98 mm


10.94 mm

12.0 mm

11.98 mm


11.94 mm

12.5 mm

12.48 mm


12.44 mm

13.0 mm

12.98 mm


12.94 mm

14.0 mm

13.98 mm


13.94 mm

15.0 mm

14.98 mm


14.94 mm

16.0 mm

15.98 mm


15.94 mm

17.5 mm

17.48 mm


17.44 mm

18.0 mm

17.98 mm


17.94 mm

19.0 mm

18.98 mm


18.94 mm

20.0 mm

19.98 mm


19.94 mm

21.0 mm

20.98 mm


20.94 mm

22.0 mm

21.98 mm


21.94 mm

Available Sheath Material

Sheath Material

Temp. Rating

800 Incoloy



321 Stainless Steel



316L Stainless Steel



304 Stainless Steel






Frequently Asked Questions

What are cartridge heaters used for?

Cartridge heaters are primarily used for conduction heating, which means they transfer heat directly to an object from the inside out. They're ideal for applications where you need to heat a material or component from within.

To determine the right cartridge heater for your needs, factors like cycle time, desired temperature, the mass of the object being heated, and manufacturing constraints will help calculate the necessary watt density. Nexthermal can recommend the best high or medium watt density cartridge heater, with or without a thermocouple, based on your specific application.

Cartridge heaters offer a variety of options to suit specific applications and temperature requirements. For example, if your process involves fast-moving parts, flexing wires, and potential moisture, a right-angle exit, stress relief tube, and epoxy potting may be recommended. You can find a detailed list of available options on our cartridge heaters page.

Cartridge heaters offer several termination options to suit various applications:

Swaged-in Leads: The most common choice, where flexible lead wires are internally connected within the heater. We offer UL-rated fiberglass (250C and 500C ratings), non-UL options (up to 650C), and Teflon (PTFE or PFA) for high-movement installations like packaging jaws. Silicone wires are also available for lower-temperature applications where flexibility is key.
  • Threaded Post Terminals or Pins: Allow for the direct attachment of lead wires.
  • Single-ended or Inline: Heaters can have leads exiting from one end or both ends (inline).
  • Lead Protection: Wires can be protected with armor cable or braided metal sleeves, depending on their routing.
  • Customer-specified Connection Plugs: We often include these for easy installation into your specific application.

Yes, we can design a custom cartridge heater tailored to your specific needs. Contact our sales engineers to discuss your application requirements.

Yes, cartridge heaters can be designed for use as an immersion heater in liquids. To ensure the best performance and safety, please provide Nexthermal with the following details about your application:
  • Type of liquid: This determines the appropriate heater materials for compatibility.
  • Amount and/or flow rate: This helps calculate the necessary heater power.
  • Process temperature: The heater must be designed to reach and maintain your desired temperature.
  • Safety and market requirements: We'll incorporate any necessary tests and certifications to meet the standards of your industry.
With this information, we can design a custom cartridge heater solution specifically for your liquid heating needs.

Cartridge heaters are resistive heaters, which means they function on both AC and DC power. The polarity and frequency of the voltage don't affect their operation.

To ensure safety and performance, standard cartridge heater testing includes:
  • High-voltage stability test:This verifies the heater's insulation and prevents potential electrical shorts, protecting the user.
  • Resistance test: This confirms that the heater's resistance matches its specifications, ensuring it delivers the expected heating output.

Here's a general overview of the process:
  1. Important Safety Note: Before starting, always disconnect the power supply and ensure it cannot be accidentally turned back on.
  2. Match Voltage: Double-check that the cartridge heater's voltage rating matches your power supply.
  3. Connect Earth Conductor (if present): This is a crucial safety measure.
  4. Route Wires Safely: Ensure wires are laid away from any sharp edges, moving parts, or potential sources of liquids and oils.
  5. Choose Connection Method: Based on the temperature and environment, select a suitable connection method (e.g., wires, plug connector, bus bar).
Follow Manufacturer's Instructions: Always refer to the specific guidelines for your cartridge heater for details on watt density, construction, and any special installation requirements. If you don’t have one, reach out to your sales engineer.

Nexthermal constructs cartridge heaters using high-quality materials and a unique manufacturing process:
  • Materials: We use grade 300 grade stainless steel for the outer sheath, purified magnesium oxide with special additives for excellent insulation, and CrNi 8020 resistance wire. Lead wires and other options are customized based on the application.
  • Precision Manufacturing: Our unique centerless grinding technique ensures a precise fit for the cartridge heater. This benefits you by providing optimal heat transfer and extending the heater's lifespan.

The best way to ensure efficient heat transfer and long life from your cartridge heater is to partner with Nexthermal. Here's why:
  • Application Expertise: We'll analyze your exact application, including the heater's dimensions and the material you're heating, to recommend the optimal hole size for the best heat transfer.
  • Precision Manufacturing: Our centerless grinding process allows us to precisely match your hole size, maximizing heat transfer and extending the heater's operational life.
  • Engineering Experience: With over 80 years of combined experience and advanced thermal simulation capabilities, we'll design the most effective heating solution for your needs.

Installation methods depend on the heater's design:
  1. Open Air Installations: Some cartridge heaters are designed for open air use and may have specific mounting guidelines.
  2. Heated Tools: Most cartridge heaters are designed for insertion into precisely drilled holes within the tool being heated.
  3. Hole Sizing: Slightly oversize the hole (+0.001") and have Nexthermal undersize the heater for an H6/g7 class sliding fit. This ensures optimal heat transfer and heater longevity, especially at high temperatures or watt densities.
  4. Heat Transfer Paste: This can improve heat conduction and make heater removal easier.
  5. Factory-Applied Coating: Nexthermal offers this as a cleaner and more efficient alternative to traditional pastes, promoting both heat transfer and easy replacement.
  6. Important: Always follow the manufacturer's instructions for your specific cartridge heater.

Important Safety Note: Always disconnect the heater from the power source and ensure the circuit cannot be accidentally re-energized before attempting removal.

Gentle Attempt:
  • Try pulling the heater out. If it doesn't budge easily, proceed to the next step.
Light Tapping:
  • Use a flat-ended bar slightly smaller than the heater's diameter to avoid flaring.
  • Tap the heater lightly with a hammer to break any corrosion and loosen it.
  • If possible, heat the tool to increase its expansion and assist with removal.
Drilling (if tapping fails):
  • Use a masonry bit to drill out the ceramic core, making the sheath easier to remove.
  • Switch to a stainless steel bit and carefully drill out the outer sheath.
  • The heater should loosen and become removable.
  • Minimize damage to the hole; reaming might be necessary afterward.
Remember: If you're unsure or the heater remains stuck, consult a qualified technician to avoid damaging your equipment

The average cartridge heater lifespan depends heavily on several factors, making a simple answer impossible. Here's why:
  • Operating Conditions: Factors like core temperature, on/off cycles, and exposure to moisture or process gasses all play a major role in oxidation and degradation of heater components.
  • Unexpected Failures: Installation issues, accidental damage, and unforeseen events can shorten heater life, regardless of its theoretical capabilities.
  • Varying Expectations: Some applications require only hours of operation, while others demand years of service. Understanding your specific needs is key.
For the longest possible lifespan, the best approach is:
  • Partner with Nexthermal: Our engineers will analyze your application to recommend the optimal design.
  • Follow Best Practices: Proper installation and operation according to manufacturer guidelines are crucial.

Yes, thermal paste can significantly improve heat transfer, lower your heater's core temperature, and extend its lifespan. However, there are important considerations:

  • Avoid Messy and Conductive Options: Silicone-based pastes are messy and unsuitable for high-temperature applications. Some graphite or copper-based pastes can become conductive or run out when heated, potentially shorting out your heater.
  • Nexthermal's Superior Solution: We offer factory-applied thermal coatings that provide several advantages:
    • Custom sizing to perfectly fit the hole.
    • Non-conductive and durable for optimal heat transfer and safety.
    • Clean and easy installation – no messy hands!

Wiring Variations: Cartridge heaters can have different wiring configurations (one, two, three, or four wires, plus potential thermocouple wires). For specific guidance, consult Nexthermal or your heater's documentation.

Important Considerations:
  • Voltage: Never exceed the heater's rated voltage. You can sometimes operate below the rated voltage (e.g., wiring two 240V heaters in series for a 120V supply).
  • Splices: Use overlap splices where current doesn't solely pass through the crimp. For optimal current distribution, crimp the wire into a ferrule.
  • Thermocouple Wires: If extending thermocouple wires, use the correct matching thermocouple wire type. Do not use standard wire.
  • EMF Noise: If you experience EMF noise affecting the controller, braid the thermocouple wires (approximately 1 turn/inch).
  • Grounded Thermocouples: Ensure the controller is compatible with the grounded/ungrounded type of thermocouple you're using.
  • Need Help? If you have any questions about your specific cartridge heater wiring, please Contact Nexthermal for expert assistance.


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