Heatrex 234 Series

234 Series Washdown/Corrosion Resistant Unit Heater

The Heatrex 234 Series unit heater is the perfect solution to the problem of heating people or equipment in non-hazardous environments where moisture and corrosion exist. Advantages include :

  • Built-in Controls :All necessary safety and temperature controls are included in a single package. Components and motor are factory-wired to a single terminal block for field wiring, eliminating the chance for field error and reducing installation costs.
  • Single Point Electrical Hook-up : Heater, fan motor and controls are all connected to the same branch circuit.
  • Corrosion Resistant : Stainless steel construction, epoxy-coated aluminum fan blade and nonmetallic NEMA 4X terminal enclosure resist corrosion found in sewage treatment plants, swimming pools, car washes, paper mills and marine installations.
  • Washable : This watertight construction can be hosed down without disconnecting the heater, which makes it ideal for coal handling areas, steel mills, foundries, ships, wood finishing plants, cement, sand, grain and food processing facilities.

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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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Impedance Heating

Product Overview: HX-881-Series, Impedance Heating System

An Impedance Heating System is a unique, safe and proven method for electric pipeline tracing and heating. The pipe actually becomes the heating element when low AC voltage is applied to it by a special, custom designed transformer.

Heatrex can provide single source responsibility for design, hardware and start-up assistance for an Impedance Heating System to heat gasses or fluids flowing through your pipeline. It can also be used over a wide range of temperatures to prevent freezing in cold weather, maintain fluidity of viscous materials, raise the temperature of heat sensitive materials or maintain gas temperatures up to 1600°F.

Benefits of Impedance Heating

  • Low Voltage Operation – All systems operate at less than 30 Volts, many at 10 Volts or below. Heatrex systems meet or exceed the requirements of the National Electrical Code (Article 427), assuring safe operation.
  • Uniform Heating – Because the entire pipe effectively acts as the heating element, heat is generated uniformly throughout its entire length and circumference without hot spots.
  • Simplicity – The impedance method takes the complexity out of pipeline heating. A few basic components comprise the entire heating system. Installation is simple; it can be installed without disturbing most of the existing thermal insulation.
  • Wide Temperature Range – Heatrex has pioneered the use of impedance heating for applications ranging from below freezing to 1600°F. It is often the only viable option for high temperature pipeline heating.
  • Close Control – Thermocouple sensors placed along the pipeline provide precise, uniform temperature control. Optional SCR controls give the ability to achieve control within ± 1°F.
  • Low Cost – Installation costs are kept to a minimum by the inherent simplicity of the system. Likewise, maintenance is virtually eliminated; many systems operate unattended. Energy costs are low because the required energy is concentrated in the pipe and efficiently heats the fluid or gas traveling through it.
  • No Burnouts – When the pipe becomes the heating element, burnouts and failures associated with electrical resistance tapes and cables are eliminated.

Advantages Over Conventional Methods

  • No External Fluids – Pipeline heating with steam or high temperature fluids introduces a high degree of complexity and a potential hazard. Impedance heating accomplishes the same result in a simple, straightforward manner.
  • No Leaky Jackets – With impedance heating, you won’t have leaky steam lines, cracked steam traps, pump failures or frozen return pipes.
  • No Hot Spots – Impedance heating eliminates the danger of overheating temperature-sensitive materials (asphalt, chocolate, heavy syrups) because hot spots associated with conventional pipe tracing are eliminated.
  • No Routine Maintenance – Routine maintenance is eliminated, along with the replacement parts and production shutdowns associated with such maintenance.

Talk to Heatrex representative here to get more information on Impedance Heating Solutions.


Heatrex, A One Stop Shop For all Your Heating Needs.

From its beginning in 1959, Heatrex has held the belief that good communication, employee education, attentive customer service and the attitude to excel are the primary ingredients in the manufacture of superior products. Heatrex commits its future to continually provide quality products and performance to its customers.

The engineering team at Heatrex utilizes the latest in CAD systems to provide a timely response to each customer’s needs. Schooled in the “Total Quality” philosophy, Heatrex engineers maintain, and strive to continually improve the design process. Proprietary software removes subjectivity from the design process, providing innovative solutions for design challenges. Drawing and specification control procedures insure that all internal departments, suppliers and subcontractors are continually updated, using the latest customer specifications.

Heatrex understands customer needs; that the accuracy and dependability of a product are crucial to its performance. Heatrex maintains an organization-wide effort to insure product conformance to rigid specifications. Each department carries its own responsibilities in the Continuous Improvement Process, in order to perpetually enhance the production sequence and insure product compliance. Manufacturing parameters are well defined and methodically monitored, assuring cost-effective production and product consistency. Quality is built-in rather than “hoped for” eliminating outdated modes of inspection.

Heatrex maintains quality throughout the manufacturing process starting with inspection of incoming materials from pre-approved suppliers to final inspections of finished products; each critical operation is carefully documented. All documentation travels with the customer order. Testing equipment is kept in compliance with defined specifications, and is independently audited to confirm accuracy, repeatability and reproducibility. First Article inspection is performed to confirm that all specifications have been met.

Final quality audits of product characteristics and in-process control procedures insure that all customer specifications and expectations have been met… resulting in total customer satisfaction.

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Watt Density

Watt Density & Sheath Selection

Watt Density

Watt density is one of the most critical factors affecting element life. Watt density, expressed in watts per square inch of heater surface area, determines the heater operating temperature for a given set of conditions. The sheath temperature of an electric heating element should be limited to provide a reasonable heater life and to avoid possible damage of the medium being heated. We can estimate the sheath temperature or select the appropriate watt density based on the charts and tables provided.

Watt density is calculated as follows:Watt Density = element wattage/3.14 x element diameter (inches) x heated length (inches)

An example is: An 8 kW flange heater has three 0.475” diameter elements with a “B” dimension of 47 inches and a 2 inch cold end. The watt density is: 0.475 x 3.14 x (47 in. – 2 in.) x 3 (# of elements) x 2 (u-bend) = 403 in2 8,000 Watts ÷ 403 in2 = 20 W/in2

Sheath Material

Also critically important, the sheath material must

be suitable for the corrosive conditions and the extreme temperatures of the application. Copper sheathed elements are typically used for low temperature applications such as heating water and some aqueous solutions. Steel is generally used with oil heating applications. Stainless steel and INCOLOY® are used when heating corrosive solutions or high-temperature gas/air. Table I and II list the maximum recommended operating temperatures for common sheath materials.

Watt Density and Sheath Material Selection

Selecting the proper watt density and the proper sheath material is critical to heater life and, if applicable, fluid integrity. If the watt density is too high, the fluid may carbonize, break down chemically, or the elements may burn out. If the watt density is too low the heater price will be high. The greatest heater life will come from the lowest watt density practical for the application.

In general, watt density is determined by three factors:

1) maximum outlet temperature

2) type of fluid heated and

3) fluid flow rate

Sheath material depends on the type of fluid and maximum temperature. If the sheath material selection is incorrect, it will corrode, destroying the element.

Heating Air and Other Gases

Charts A through C give maximum sheath temperatures for a range of watt densities and velocities. This data is based upon air at atmospheric pressure and a 75°F inlet air temperature. For higher inlet temperatures, the sheath temperature will increase accordingly. Contaminants in the air, while normally not affecting the sheath temperature, may require a more highly corrosion-resistant sheath and/or fin material. For heating compressed air and other gases, consult the factory or your local Heatrex representative for watt density and sheath recommendations.