233 Series Explosion-Proof Unit Heater

Heatrex 233 Series Explosion-Proof Unit Heater

Heatrex’s 233 Series EXP explosion-proof unit heater is designed with both safety and versatility in mind. Unique 233 Series features include:

  • Industry’s Lowest Ignition Temperature Code Rating : T3C, 320°F (160°C)
  • Dual Over temperature Protection: With both automatic and manual reset over temperature cutouts for additional safety.
  • Nontoxic Propylene Glycol Heat Transfer Fluid
  • Low 70 PSIG Relief Valve Setting: This assures that in an emergency, the initial escaping vapor temperature remains below the 320°F (160°C) ignition temperature.
  • Corrosive Resistant Options: Heatrex offers three constructions suitable for most applications. Standard construction for use in dry non-corrosive areas includes : Welded steel heat exchanger; powder-coated cabinet; epoxy-coated motor. A 316 stainless steel construction suitable for Wastewater Treatment Plants includes : 316 stainless steel heat exchanger, headers and tubes with aluminum fins; stainless steel cabinet; corrosive resistance hardware; epoxy-coated motor. Third construction is suitable for use in Chemical Plants where chlorides are present and includes : Heresite® coated heat exchanger, cabinet, fan blade; corrosion resistance hardware; epoxy-coated motor.

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Component Heaters for Skid-Mounted Process Heating Systems

The Challenge

  • A global skid-process system manufacturer that works in the power gen, oil & gas, nuclear, and industrial sectors was challenged to design skid-mounted processing equipment for a major energy company. The energy company needed a modular system that would increase the efficiency of their turbines for a series of oil & gas applications. The modular system needed to heat and circulate lubrication oil used to lubricate the turbines. The quality of the heater was of utmost importance, as maintaining the oil at a precise temperature in the holding reservoir is paramount in ensuring the system consistently ran effectively. The customer needed a solution that perfectly balanced durability, ease of maintenance, and customization to specs.

Component Heaters for Skid-Mounted Process Heating Systems

The Solution

  • Heatrex’s reputation for quality has earned it a place on many preferred supplier lists, including being a GE approved Supplier.  In addition to producing premium quality products, Heatrex was awarded the contract to manufacture 16 immersion heaters due to its competitive price and short lead times. The Heatrex engineering team designed a flanged immersion heater that was ready to “plug in” to the modular system upon arrival, not only making installation smoother, but guaranteeing ease of maintenance.

Component Heaters for Skid-Mounted Process Heating Systems

The Benefits

  • Heatrex’s customized immersion heaters enabled the process system manufacturer to successfully deliver the optimal skid mounted process system for its customer. The skid manufacturing company was so impressed with these immersion heaters, they recognized Heatrex, in an ISO audit (International Organization for Standardization), as a supplier with unprecedented customer focus that consistently meets the sourcing requirements on quality and price, upholds the highest standards of delivery quality, and demonstrates the highest levels of flexibility and responsiveness.


Heatrex played an integral role in delivering the necessary quality, and continues to work closely with the manufacturer to exceed the energy company’s high expectations.

Customer Testimonial

“We have been very happy with the Heatrex heating elements, especially on lead times and pricing. The competitors can’t compare on those aspects.”

Global Process System Manufacturer



240 Series Unit Heater 

The 240 Series unit heater is available in 50 standard models with ratings up to 50 KW and voltages of 208, 240, 277, and 480 single or three-phase. They are available with a wide variety of factory built-in or field-installed options.

Temperature Control: Single-stage or two-stage control with built-in or remote-mounted thermostats are available on all heaters.

Control Options: Available as factory built-in or fieldinstalled to meet job specifications. Custom KW’s: Custom KW’s are available up to 50 KW.

Discharge Direction: Heater can be mounted for horizontal or vertical discharge using an optional universal wall/ ceiling mounting bracket or with field-furnished threaded rods for ceiling mounting.

Color Options: The standard color is camel. Six optional colors are available: grey, yellow, red, white, blue or textured beige. Heaters may also be supplied with unpainted corrosion resistant galvanized steel.


  • Factories
  • Garages
  • Mechanical Rooms
  • Pump Houses
  • Service Areas in Air Handling Units
  • Shipping and Receiving Areas
  • Storage Areas
  • Warehouses
  • Workshops

Standard Construction Features


Heating Elements – Industrial grade, 0.475” diameter steel sheath with brazed copper plated steel fins and epoxy sealed ends. Draw-thru airflow design pulls air across the heating elements to ensure cool element operation and even air distribution resulting in long element life.

Housing – Heating elements and motor are enclosed in a heavy gage galvanized steel cabinet with a durable polyester powder coat finish.

Outlet Grille – Individually adjustable louvers are provided to direct airflow. A protective outlet fan guard is provided to prevent insertion of foreign objects.

Fan Motor – Permanently lubricated and thermally protected motor.

Built-in Controls – All units include an automatic reset thermal cutout that will de-energize the heater if an over-temperature condition occurs. A manual Standard Construction Features reset thermal cutout, in addition to an automatic reset thermal cutout, is standard on heaters 10 KW and above. A fan relay is provided to allow the elements to heat up before fan startup and purges the heater of residual heat after shutdown. A 24-volt transformer and disconnecting contactor are provided on most heaters. Single-phase heaters rated at 5 KW or less have line voltage controls; 24-volt control and contactor are available. Power fusing is standard on all heaters rated over 48 amps.

Mounting – Universal horizontal or vertical discharge. Optional diffusers are available for vertical discharge. An Anemostat diffuser can be used to provide draft free air movement at lower mounting heights. For higher mounting heights, radial diffuser with adjustable fins can be used to increase floor coverage or adjusted for a vertical down blast of air.

To view the different kinds of options, charts, and tables click here.

Screw plug heaters

Screw Plug Heaters

Screw plug heaters are a type of immersion heaters that can heat liquids and gases in a variety of applications.  They can be used to process water heating and freeze protection.  Heatrex offers many different screw plug heaters that can provide direct heating at an energy-efficient cost.

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