Industrial Duct Heaters


Duct air heaters feature a heavy-gauge mounting flange, Incoloy® tubular heater elements for long life and durability, and high tensile strength support frames to ensure proper air heater performance. They can be installed vertically or horizontally into ducting to heat flowing air as it passes over tubular elements.

Durex Industries manufactures standard and custom-designed electric duct heaters that are well suited for the needs of many heavy-duty industrial and process applications. We construct high tensile strength cages to support heater elements in larger, higher temperature units to ensure proper air heater performance.

Considerations When Applying Duct Air Heaters

Depending on your application, there are a variety of things to consider with inline duct heaters. Before buying an electric duct heater, consider:

Industrial Duct air Heaters from Durex Industries

The optimal sheath material and maximum allowable watt densities are used to minimize size, weight, and footprint. Replaceable heating element designs, as well as modular "bank" type designs, are available.

Medium temperature air heaters are for more economical, lower temperature applications to 750°F (400°C). High-temperature air heaters are designed for elevated process temperature applications to 1200°F (650°C).

In addition to our variety of standard designed duct air heaters, we also manufacture custom designed and fabricated industrial air heaters to fit various duct sizes and mounting flange requirements. In addition to Incoloy elements, stainless steel elements can be provided upon request.

We also offer custom:

Design Features:

  • Incoloy® sheathed heater elements for long life, corrosion-resistant performance
  • Recompacted element bends remove voids to ensure insulation integrity
  • Stainless steel element spacers & supports to ensure spacing and prevent sagging
  • Thermally insulated terminal enclosure keeps wiring cool & reduces heat losses
  • Integral sensors available allowing process and over-temperature monitoring
  • c-UL recognized elements to 600VAC available assuring safe & reliable performance

Contact Durex Industries Today for Duct air Heaters

Durex Industries provides a variety of standard designed duct air heaters with carbon steel mounting flanges, stainless steel support rods, element support spaces, and insulation collar. We also offer many customizable options to better fit your application needs.

Duct air heater specifications & options

Construction Options

Process Sensors - thermocouple or RTD sensor probe is inserted into a thermowell in the heater to measure duct air outlet temperature. Type J and Type K thermocouples and Pt 100 Ω DIN Curve RTD sensors are the most common used. Standard sensor lead length is 72” (1825mm). Specify sensor type and lead length when ordering.

High Limit Sensors - A thermocouple or RTD sensor probe is fed through the mounting flange and clamped directly to a heater element. This allows for early detection of element over temperature conditions that may shorten heater life. An alternative is to insert the high limit sensor into a thermowell that is clamped or welded to the heater element sheath. This facilitates easy sensor replacement, but at the expense of a slower sensor response time. Standard lead length is 72” (1825mm). When ordering, specify sensor type, sensor mounting style and lead length.

Custom Voltage and Power Rating - A large variety of standard high-temperature and medium temperature duct air heater designs are available. However, custom volts, watts and watt density designs are available upon request.

Duct Configuration and Plate Flanges - In addition to the standard duct heater designs, Durex will custom design and fabricate purpose-built duct heaters to fit virtually any duct size and mounting flange requirements. Standard mounting flanges are carbon steel, however, 304 stainless steel and 316 stainless steel are readily available alternatives. Support rods, element support spacers and insulation collar are all of stainless steel construction standard.

Replaceable Heater Elements - Durex standard design duct air heaters use seal-welded heater elements. Optional replaceable heater elements can be specified with retaining clips or gas-tight compression fittings. Retaining clips keep elements in place and allow easy replacement in minimal pressure applications. Compression fittings offer field replacement, while still providing a gas-tight seal. Contact Durex for assistance in specifying replaceable elements.

Seal Options

Silicone Conformal Coating – On standard heaters, this seal provides general moisture / contamination protection to 220°F (105°C). However, it is porous and will allow moisture penetration over time. Not recommended for storage or use in high humidity environments.

Silicone RTV – Offers improved moisture and contamination protection to 400°F (200°C). However, it is also porous and will allow moisture ingress over time.

Epoxy Seal – Offers the best moisture and contamination protection of these seal choices. Rated for 450°F (230°C), this seal has low porosity and is recommended for higher temperature applications, high moisture environments and where long term storage is foreseen.

----SPST-DPST-Thermostats.jpgThermostats - Single pole (SPST) and double pole (DPST) available. Optional knob & bezel. Single pole, single throw (SPST) thermostat



Part numbers are for thermostats only. Please contact Durex Industries if knobs and bezels are required.


Part Number Description Maximum Voltage Maximum Amperage Bulb Length Bulb Diameter Capillary Length
CNTR-TSTAT-CAP-0-100-01 0-100°F SPST 240V 20 A 3.3" .24" 36"
CNTR-TSTAT-CAP-85-230-1 85-230°F SPST 240V 20 A 3.3" .24" 36"
CNTR-TSTAT-CAP-120-570-1 120-570°F SPST 240V 20 A 3.5" .20" 36"
CNTR-TSTAT-CAP-0-100-03 0-100°F DPST 480V 10 A / pole at 480V

30 A / pole at 240V
4.5" .375" 84"
CNTR-TSTAT-CAP-060-250-04 60-250°F DPST 480V 4.5" .375" 60"
CNTR-TSTAT-CAP-100-550-01 100-550°F DPST 480V 4.5" .375" 60"

How to Order

  • Quantity
  • Electrical Rating - Voltage, phase, wattage
  • Duct Size - Provide interior duct height and width dimensions
  • Duct Heater Configuration - High temp or medium temp duct heater design
  • Flange Size and Material - Provide information or advise if Durex to provide
  • Element Diameter and Quantity - If known or indicate Durex should provide
  • Element Watt Density - 20, 23, 30 W/in2 or indicate if Durex should provide
  • Dimensional Information - Refer to high temp or medium temp for required dimensions.
  • Seal Type - Silicone conformal coating (standard), RTV or epoxy.
  • Electrical Enclosure - NEMA 1(standard) or NEMA 4 (moisture resistant)
  • Sensing & Control - None (standard), process sensor type or/and high limit sensor type
  • Other Custom Specifications - Specify as required

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High Temperature Heater Design Features:

  • 5 to 300 kW Ratings at up to 480V
  • 1200°F (650°C) Max. Outlet Temperature
  • Up to 20 W/in² Rating
  • Insulated Stand-Off Housing for Cool Wiring Temperatures

View Standard Designs



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Medium Temperature Heater Design Features:

  • 5 to 60 kW Ratings at up to 480V
  • 750°F (400°C) Max. Outlet Temperature
  • Up to 15 W/in² Rating
  • Enclosure-Side Insulation for Cool Wiring Temperatures

View Standard Designs




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Typical Duct Air Heater Applications

Duct heaters are robust heaters that are designed with heavy-duty construction, making them perfect for industrial and process requirements. They are resistant to dirt, vibration, and contamination. In addition to this, commercial electric duct heaters provide high-powered air heating in a small footprint.

They are typically used in forced air ducts to heat the airflow for processing applications, and they can also be found in:

  • Industrial Drying & Curing
  • Heat Treating
  • Reheating & Dehumidifying
  • Autoclaves
  • Convection furnaces
  • Core & Refractories Drying
  • Load Banks

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Process Heater Brochure PROC-BROC-0912 - 7MB


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