Cartridge Heater

Cartridge heater often considered as component heater has a heating coil wounded on a ceramic core and are cylindrical-shaped, heavy-duty Joule heating element. Electricity flows through coil when two or three-phase voltage is applied. The electricity heats the coil and, subsequently, the cartridge sheath. The watt density (in Watt/inch²) depends on the number of spirals or turns per inch. The sheath comes in contact with the surface being heated. Insulation in the cartridge heater ensures that the heating wire never comes in contact with the sheath and protects the sheath from melting in case of any mishap. The leads that come out of the heater terminal have metal conduit, or silicon sleeves to protect from high temperature. Lead wires are often fiberglass or silicon rubber.

These heaters provide a suitable, reliable and competent method of applying concentrated heat to solid metal components to high temperatures, particularly where compact, insert type heating is desirable. Swaged construction provides minimal air gaps, which lead to high efficiency and improved heat transfer.  Distinguished for long trouble free service, cartridge heaters have precise dimensions and tolerances. Heating elements are kept close to the material being heated for maximum heat transfer, minimum core temperature, and faster heating. Use of stainless steel sheaths provides non oxidizing surfaces. The surface watts density and operating temperature of a cartridge is dependent on hole clearance. The larger the hole clearance the lower the recommended watt density. For temperature sensing, a thermocouple should be positioned in the heater but its life is reduced by slow “ON/OFF” cycling of power controllers. So PID auto tuning controllers with solid state relay or thyristor output are suggested.



Sheath Material  Stainless steel, INCOLOY
Watt Density Up to 400 W/in2
Design temperatures Up to 760°C (1400° F).
Voltage Up to 480V AC
Length Up to 72 inches
Leads Stranded/ Swaged in/ Pin leads/ Crimped on/ Customized
Controls Thermocouple/ RTD
Sheath Length tolerance ±3% (standard), special tolerance available on request
Wattage length +5%, -10%
Resistance tolerance +10%, -5%

Note- For custom design requirements please contact sales@marathonheat.com

Download Catalogue



Nominal diameter Minimum diameter Maximum diameter Std. Lead wire gauge Max amps with std. Lead wire Max lead wire gauge Maximum amps Maximum volts
1/8” 3.022 3.14 24 3.6 24 3.6 240
1/4″ 6.19 6.32 24 6 22 9 300
6 mm 5.82 5.97 24 6 22 9 300
6.5 mm 6.35 6.47 24 6 22 9 300
5/16” 7.77 7.89 24 6 22 9 300
8 mm 7.84 7.97 24 6 22 9 480
3/8“ 9.37 9.49 22 9 18 15 480
10 mm 9.86 11.96 22 9 18 15 480
12 mm 11.83 12.48 22 9 18 15 480
12.5 mm 12.34 12.67 22 9 18 15 480
1/2″ 12.55 12.97 22 9 18 15 480
13 mm 12.85 13.46 22 9 18 15 480
17/32” 13.33 15.84 22 9 18 15 480
14 mm 13.84 13.97 18 15 14 26 480
5/8” 15.72 15.84 18 15 14 26 480
16 mm 15.84 15.97 18 15 14 26 480
17 mm 16.84 16.96 18 15 14 26 480
11/16” 17.32 17.44 18 15 14 26 480
19 mm 18.84 18.97 18 15 14 26 480
3/4” 18.89 19.02 18 15 14 26 480
25 mm 24.84 24.96 18 15 14 26 480
1” 25.24 25.37 18 15 14 26 480



Maximum Operating Temperatures

Maximum Watt Density

          °F           °C         As mentioned above         W/cm2
   INCOLOY 1400 760 400 62
 Stainless Steel 1000 538 400 62


Lead wire options:

Wire Type Temperature Rating Maximum Recommended Temperature Comments
Ultralead 250°C 450°C Excellent, durable wire, good for high-temperature application
Teflon 250°C 450°C Good dielectric strength
Silicon Rubber 250°C 450°C Good moisture resistance
Braided Silicon rubber 250°C 450°C Inexpensive wire, good for non-abrasive applications.
MGT 250°C 450°C Superior high-temperature resistance
SJO cord 94°C 90°C Rubber Jacket, resistance to oil and moisture. For use on 3/8” diameter and larger.

Thermocouple: Cartridge heaters can also accommodate internal thermocouple which helps in controlling temperature of heater more accurately. Thermocouples can be of type “J” or type “K”, grounded or ungrounded, and can be attached at the disc end or middle of the heater. Thermocouple lead wire is 24 gauge unless specified, thermocouple leads are of the same length.

Termination Options:

     1. Swaged in Leads

  • Swaged in Leads are ideal for application where there is excessive movement or leads are required to bent sharply upon exiting the heater.
  • In heaters under 3” long, leads wire goes directly into the core whereas in heaters over 3” long, leads are connected to power pins in unheated section.
  • Also remember, if the leads are required to be inserted completely into the hole, they are exposed to the block temperature ( maximum temperature for standard leads is 550°C ).
  • Unless otherwise specified, all heaters will be supplied with Swaged in Leads.

     2. Right angle Leads

  • Right angle leads are ideal for application with tight spaces.
  • Leads are covered with a silicon impregnated fiberglass sleeve where they exit the heater.

     3. Distributed wattage                     

  • Distributed wattage hotrods( with a higher watt density on the ends rather than the rest of the heater) can be used to compensate for end losses in blocks.
  • Distributed wattage hotrods are available in all diameters.

     4. Right angle stainless steel conduit

  • They offers the same advantages as swaged in stainless steel conduit but allows use in tight spaces.


End Seal options:

     1. Teflon Seal

  • Teflon seal is used where an effective sealing is required against moisture and oil contamination.
  • Teflon lead wire is used in conjunction with Teflon seal to provide an effective barrier.

     2. Epoxy Seal

  • Epoxy potting forms a good moisture seal with more mechanical strength than a silicon rubber seal.
  • Regular Epoxy is rated at 350°F (177°C) and epoxy lite is rated at 600°F (316°C).

     3. Silicon Rubber Seal

  • High temperature silicon rubber seal in conjunction with silicon rubber lead wires provides an effective moisture seal up to 400°F (200°C).
  • It is the most impervious seal of all the other moisture seals.

     4. Cement

  • Provides protection against some thicker liquids and dust, however it is not waterproof.
  • It is also somewhat brittle and subject to cracking in high impact or high vibration application.
  • Used for temperatures up to 2600°F (1425°C).


Sheath Material

Molds, Metal dies, Patens, hot plates, sealing tools, fluid heating, aerospace, semiconductor industry, screen exchangers, plastic extruders Stainless Steel, INCOLOY
Food service and medical equipment, Deionized water Stainless Steel
General applications INCOLOY
Highly corrosive applications Titanium
  • Able to reach and transfer heat wherever required, without losing much energy during the transmission.
  • Minimized energy loss and enhanced effectiveness of the heating process.
  • Distributed Wattage.
  • Higher Watt Densities and Operating Temperatures.
  • Temperature sensing capabilities built into the heater can increase its utility and lifespan, by helping to control temperatures and prevent overheating.