Cartridge / ROD Heaters

Custom Cartridge Heaters

The Right Thermal Solution for You

Cartridge heaters are versatile and can be configured for optimized performance of a specific application. Many companies can make cartridge heaters. Nexthermal’s goal is to build your cartridge heater. The right cartridge heater, built specifically to your application 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 deliver the solution you need.

Common Applications of Cartridge Heaters

  • Packaging
  • Rubber Molding
  • Form Fill & Seal
  • Platen Heating
  • HVAC Compressors
  • Die Casting
  • Hot Melt Adhesives
  • 3D Printers
  • Mass Spectrometry
  • Food Manufacturing
  • Hot Melt Adhesive
  • Pellet Stove Igniter
  • Torpedo Heaters for Injection Molding
  • Heat Staking
  • Extrusion

Cartridge Heaters available at Nexthermal

High Watt Density Cartridge Heaters

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 performance and durability you need.

– vs –

Medium Watt Density Cartridge Heaters

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 watt density cartridge heaters. Medium watt heaters are every bit as durable as high watt density heaters with the additional advantage of fewer electrical connections on multi core (longer) heaters.

Though construction will differ between high watt density and medium 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 the 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
Cartridge with Exposed Winding

The image on the left has the windings exposed to showcase the distributed wattage.  The tighter windings are not limited to the end points; they can be applied anywhere on the heater to best suit your applications’ needs.  Nexthermal can help put the heat exactly where you need it.

Cartridge Heater Recommendation

Cartridge Heater Options

Nexthermal Cartridge Heater Options - Distributed Wattage
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.

Nexthermal Cartridge Heater Options - Moisture Resistance
Moisture Resistance

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

Nexthermal Cartridge Heater Options Anti-Seize Coating
Anti-Seize Coating

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

Nexthermal Cartridge Heater Options - Removal Aids
Removal Aids

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 Cartridge Heater Options - Right Angle Exit
Right-Angle Exit

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

Nexthermal Cartridge Heater Options - Right Angle Block
Right-Angle Block
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.
Nexthermal Cartridge Heater Options - Flanges and NPT Fittings
Flanges and NPT Fittings

For applications requiring a specific insertion depth, or that they 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 Cartridge Heater Options - Centerless Grind Tolerance
Centerless Grind Tolerance

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.

Leads, Potting Options, & Lead Protection

Specifications

Dimensional / Electrical

Length Tolerance
Premium Length Tolerance
Min. Heater Length
Max. Warranted Sheath Load
Standard Watt Tolerance
Premium Watt Tolerance
Std. High Volt Stability (Cold) ≤ 24 V
Std. High Volt Stability (Cold) > 24 V
Premium High Volt Stability (Cold) > 250 V
Insulation Resistance
Premium Insulation Resistance
Leakage Current
Max. Connection Volt (UL Rated)
Max. Connection Volt

High Watt Density

±1.5% (min. ±1 mm)
Upon Request
1", 25.4 mm*
160 Watts / in²
+5%, -10%
±5%, lower possible with specific designs
500 V AC @ 100 mA
1500 V AC @ 100 mA
Upon Request
≥ 5 M‎Ω @ 500 V DC
Upon Request
0.5 mA @ 253 V AC
600 V
600 V

Medium Watt Density

±1.5% (min. ±1 mm)
Upon Request
8", 203.22 mm**
65 Watts / in²
±10%
±5%
500 V AC @ 100 mA
1500 V AC @ 100 mA
Upon Request
≥ 5 M‎Ω @ 500 V DC
Upon Request
0.5 mA @ 253 V AC
600 V
600 V

1/8″ Heater

±3.0%
---
1.25", 31.75 mm
120 Watts / in²
+10%, -15%
+5%, -10%
Not Available
800 V AC @ 100 mA
Not Available
≥ 5 M‎Ω @ 500 V DC
Not Available
0.5 mA @ 253 V AC
N/A
250 V

*Shorter lengths may be possible depending on required wattage.
**Dependent on application requirements.

Length Tolerance
±1.5% (min. ±1 mm)
Premium Length Tolerance
Upon Request
Min. Heater Length
1″, 25.4 mm (Shorter lengths may be possible depending on required wattage.)
Max. Warranted Sheath Load
160 Watts / in²
Standard Watt Tolerance
+5%, -10%
Premium Watt Tolerance
±5%, lower possible with specific designs
Std. High Volt Stability (Cold) ≤ 24 V
500 V AC @ 100 mA
Std. High Volt Stability (Cold) > 24 V
1500 V AC @ 100 mA
Premium High Volt Stability (Cold) > 250 V
Upon Request
Insulation Resistance
≥ 5 M‎Ω @ 500 V DC
Premium Insulation Resistance
Upon Request
Leakage Current
0.5 mA @ 253 V AC
Max. Connection Volt (UL Rated)
250 V
Max Connection Volt
600 V

Length Tolerance
±1.5% (min. ±1 mm)
Premium Length Tolerance
Upon Request
Min. Heater Length
8″, 203.22 mm (Dependent on application requirements.)
Max. Warranted Sheath Load
65 Watts / in²
Standard Watt Tolerance
+10%
Premium Watt Tolerance
±5%
Std. High Volt Stability (Cold) ≤ 24 V
500 V AC @ 100 mA
Std. High Volt Stability (Cold) > 24 V
1500 V AC @ 100 mA
Premium High Volt Stability (Cold) > 250 V
Upon Request
Insulation Resistance
≥ 5 M‎Ω @ 500 V DC
Premium Insulation Resistance
Upon Request
Leakage Current
0.5 mA @ 253 V AC
Max. Connection Volt (UL Rated)
250 V
Max Connection Volt
600 V

Length Tolerance
±3.0%
Premium Length Tolerance

Min. Heater Length
1.25″, 31.75 mm*
Max. Warranted Sheath Load
120 Watts / in²
Standard Watt Tolerance
+10%, -15%
Premium Watt Tolerance
+5%, -10%
Std. High Volt Stability (Cold) ≤ 24 V
Not Available
Std. High Volt Stability (Cold) > 24 V
800 V AC @ 100 mA
Premium High Volt Stability (Cold) > 250 V
Not Available
Insulation Resistance
≥ 5 M‎Ω @ 500 V DC
Premium Insulation Resistance
Not Available
Leakage Current
0.5 mA @ 253 V AC
Max. Connection Volt (UL Rated)
N/A
Max Connection Volt
250 V

FAQ's

What are cartridge heaters used for?

The main use of cartridge heater is as Conduction heat. Whenever you are trying to heat from inside to outside, the best solution is an optimal designed cartridge heater as per the application requirements. Based on cycle time, process temperature, mass to be heated, the parts need to be heated – watt density is calculated on the surface of the heater. Accordingly, the watt density, application and the manufacturability Nexthermal would recommend High or Medium watt density cartridge heater with or without thermocouple.

What options are available on cartridge heaters?

The application and process temperature dictates the various options for a cartridge heater. Example for fast moving parts with flexing wires and moisture, Nexthermal would recommend a right-angle exit, stress relief tube and epoxy potting. For various other options please consult our cartridge heater option page.

What are some of the termination options offered on cartridge heaters?

The most common option is flexible lead wires internally connected inside the heater (we call this “swaged in”). Other options can include threaded post terminals or pins, which can have leads added. In all cases its can be single ended ot leads out each end (inline).

The flexible leads we offer are based on the application and can include UL rated fiberglass in 250C and 500C ratings, non-UL can be rated up to 650C. Teflon (PTFE or PFA) are also available as well and are well suited for high movement installations like packaging jaws. We also offer silicone wires for cases where the temperature allows and high flexibility is required.

The wires can be encased in armor cable or braided metal sleeve depending on the routing of the harness.

And lastly we should note that Nexthermal often includes customer specified connection plug to make it easy to install the heater into the customer application.

Can I have a specially designed cartridge heater?

Yes. Contact Nexthermal sales engineers to review your application and they can design a heater to fit your need.

Can cartridge heaters be used in liquids as immersion heaters?

YES. Nexthermal would need to know the type of liquid needs to be heated, amount and or flow rate, process temperature under others. As per the demand of the safety and requirements for specific market segments, Nexthermal will add all tests to qualify the heater for you as supplied to you.

Are cartridge heaters AC or DC?

Any electric heater is a resistive type of heater, polarity and frequency of the voltage supply does not affect the heater.

How do you test a cartridge heater?

Standard testing includes high voltage stability to protect the user from electrical shorts as well as resistance testing to verify the performance of the heater with respect to its rating.

How do you hook up a cartridge heater?

Ya plug it in, it will get hot. Well, that is the standard reply I give everyone. Some heaters have optional thermocouples – those you do not want to apply power to. The heat that will generate is impressive but unusable, and immediately damages the heater.

Always follow the marked voltage (or lower) on the heater when applying power. Heaters are typically regulated by a Solid State Relay (SSR) which switches the power to the heater from instructions by a temperature controller. A heater operated without a control system can exceed temperatures that are useful in the application as general rule of thumb is only about 20% of the rated wattage is needed to maintain set temperature once it reaches steady state.

How are cartridge heaters made?

Nexthermal manufactures cartridge heater with stainless steel 300 grade, the winding core and filled material is purified magnesium oxide with specific adder for high electrical values and CrNi 8020 resistance wire. The lead wires and options are as per application requirements. NEXTHERMAL IS THE ONLY US COMPANY, WHICH DOES CENTERLESS GRINDING OPERATION TO GIVE THE CARTRIDGE HEATER A PRECISE FIT, which ultimately BENEFIT THE CUSTOMER WITH OPTIMAL HEAT TRANSFER AND LONGER SERVICE LIFE.

How can you get the most efficient heat transfer and longest operational life out of a cartridge heater?

This is where a good partnership is developed between Customer and Nexthermal. Knowing exactly the application, length of the heater as well as the diameter of the heater – Nexthermal recommends a hole size which will be most effective for the application. With centerless grinding Nexthermal has then the flexibility to match the hole for optimal heat transfer and long service life. With 150+ years of engineering combined knowledge in Application with as required thermal simulation, Nexthermal is the best Thermal partner you have in the market.

How do you install a cartridge heater?

Depends on what the heater is designed to do. Some cartridge heaters are intended for use in open air installations. More commonly cartridge heaters are intended for use in a hole in the tool that is being heated. In those cases a good fitting condition is needed to properly conduct the heat energy from the heater into the tool and to maximize the heater life. A best condition case is to oversize the nominal hole with a +0.001″/-0″ final dimension, Nexthermal will undersize the heater for a H6/g7 class sliding fit. This fit becomes critical at higher operating temperatures or higher watt densities.

Sometimes it’s advantageous to use a heat transfer paste to facilitate the best conduction of heat from the heater to the tool, as well as aid removal for replacement. Nexthermal offers factory applied high temperature resistant coating methods to enhance the removal of the heater as well promote heat transfer in replacement to the messy hand applied pastes in the market.

How do you remove cartridge heater?

Disconnect the heater from the power supply or otherwise render the circuit safe.

After that, there is a series of steps. First you ask nicely by pulling it will dislodge it. Most often it will not, so don’t put a lot of effort into that.

Next comes a hammer and well sized bar. You want the bar to be close to the outer diameter of the heater as you want the force of the hammer to act against the outer wall of the tube. Do NOT use a punch as it will swage the heater into the tool by flaring the heater into the hole – make sure the end of the bar is flat. I encourage a light tapping to break the corrosion loose and allow slipping rather than large heavy hitting. Sometimes if the tool is a high enough thermal expansion heating the tool can be helpful. Insert the bar – flat end against the end cap of the heater – and tap the heater backwards to clear the hole.

If that does not work, the next step is a drill the heater out. Using a drill and masonry bit sized to remove the ceramic inside the heater sheath is helpful in making the final drill out easier. Once the inside is removed you can switch to a nominal sized metal drill suitable for stainless steel and drill out the casing. At this point it’s likely to break loose and can be removed. Try to do this without damaging the hole surface, otherwise reaming might be needed to clean up the inside of the hole.

What is the average lifespan of a cartridge heater?

This is a very complicated question. The best answer is to determine based on your application. If seems like a cop out, your right.

Fact is you can make a pretty good guess using the oxidation rates of the electrical components over time of exposure – if you know what the core temperature of the heater is (not the set temperature – the core is always hotter) allowing for the power on temperature (the delay between the heater having full power applied and the sensor reporting that its not needed). Then you have to account for the time off where the components are not heating and thus not subject to the oxidation. Add in in that the resistance wire is spalling off the layer of Chromium oxide each time and reforming as the wire heats and cools for each cycle and you can get a pretty good idea. Then find it to be all rubbish anyway ,as moisture, or process gas, or wire damage happens and its failed anyway.

In most cases heaters dont die from old age, they die from installation issues which are outside our control. We have found customers have varying expectations of heater life, some hours, some years. It’s in the proper design, installation and operation which can get us to meet the customer expectation for lifespan.

Should I use thermal paste with my heater?

Yes. Anything that promotes heat transfer reduces the core temperature of the heater and contributes to longer life and faster response. That being said however there are some pastes that you need to be mindful of.

Silicone based paste is great if you want a mess, and are low enough temperature.

Higher temperature pastes are available on the market, some are graphite or copper based mixed in grease. Keep in mind that the graphite is conductive and any that pushes out while inserting the heater can contaminate the heater or leads. As the application gets hot, the grease lowers viscosity and wicks into the heater and eventually shorts out the heater.

We recommend you consider our factory applied coating options. The heater is sized to fit with the coating to your hole size (extra can be scraped off during installation). The coating is not conductive and is hard enough to prevent damage during normal handling and installation. And you don’t end up with messy hands.

How to wire cartridge heater?

Cartridge heaters can have one wire, two wires, three wires or four wires. They can also include thermocouple wires as well. There is no way we can adequately explain each here, so if in doubt call Nexthermal and we can help with your particular heater.

In general be mindful that the heater rating must be observed. Applying voltage over the rating can destroy the heater. You can apply below the rated voltage i.e. 120V to wire two 240V heaters in series.

Any splices that are added to the leads must be the overlap style where the current does not go through the crimp alone. For best practices the wire should be crimped into a ferrule so the current is well distributed to all wire strands.

Thermocouple wires are a special alloy so if added to must use the correct thermocouple wire to extend. Do not use standard wire to extend these. If EMF noise is a issue with the feedback to the controller, braiding the wire together (about 1 turn/inch) will help. Be mindful if the thermocouple is a grounded style or not, the controller might not react correctly if flipped.

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