Tubular Heaters Power Ratings

What Do Tubular Heaters Power Ratings Mean?

Tubular heaters are resistant heaters encased in round tubes often shaped for specific applications.  The tube’s materials and casing protect the electric resistive heating elements inside the heater from damage and direct contact with fluids or other materials.  

The tubular element conducts heat effectively from the resistive elements to the air or other material surrounding the tubular casing.

This effective transfer of heat without air contacting the surface of the resistive wire allows the heating element to operate at a fixed power output without burning the resistive elements; as a result, no oxidation takes place, and the voltage and current are isolated the surface of the casing.

Tubular Electric Resistant Heat Output.

The output of a tubular heater is calculated by determining the power or energy per unit of time. First, you calculate the rate at which voltage and current are converted into heat inside the tubular casing.  This formula is true of all resistive circuits, with the power being measured in units of watts (W).

P (power) = W (watts) W = I(current in amps) x V (voltage in volts)

A tubular heater that produces 500 W = 4.17 Amps x 120 Volts

Power can also be calculated by multiplying the (I²) current squared x resistance (Ohm Ω)

(I²) 4.17²  x  (Ω) 28.7539 = 500W

Tubular heaters are rated by Power Output. Their power output sells resistant heaters output for specific voltage and internal resistance of the device.   The manufacturer measures the resistance of the heating element and then calculates the voltage required for particular power output.  Since voltages tend to be standard in heating applications at 120 and 240 volts is current.

With a little more algebra, you know that voltage equals resistance time curr So t.  V = IR solving for is V/R = I or current.  

In the previous example, the resistance was measured to be 28.7539 (Ω) Ohms.  The current then is 120 V / 28.7539 = 4.17 amps or current.  V x I = W - 120 V x 4.17 A = 500 watts.

See the electrical heating portal, energy, and power category for more information on energy calculations.

How many watts do I need?

It depends on what material you are heating.  Every material has a different heat transfer coefficient.  DBA USA tubular heater is designed the maintain a constant temperature in an industrial electrical or process enclosure.  Air is the typical media for heat transfer from a tubular heater in an enclosure.

The transfer of heat can be by the natural convection of forced air. However, forced air will move heat away from the tubular heater faster than natural convection.  The tubular heater controls its heat output by a resistive thermostat mounted to the unit.  

This resistive control doesn’t measure the heat of the air in the enclosure. Instead, it controls the heat of the tubular heat exchanger by controlling the resistance of the circuit and current. 

No need for a thermal dynamics engineer

DBK USA engineers have experience in sizing tubular heater elements based on a wide range of enclosures and applications.  Based on the size and composition of the enclosure, environmental conditions, internal components, and available voltages, they will help select the correct size tubular heater for your application.

Refer to our blog article for more specific information on heat transfer coefficients and transferring heat from a PTC heating element.  The same formulas apply to tubular heaters.

How are Tubular heaters made?

The tubular heating elements can be formed into virtually any shape. However, due to their high temperatures and watt densities, the sheath materials need to be durable and have a long life.

Outside sheath temperatures can reach 170 degrees Fahrenheit, although some go as high as 1,600 degrees F.  The tubular heaters are made for immersion and air heating applications.  Electrical enclosure applications may only come in contact with air, but other industrial applications may include heating liquids.  

Due to the corrosive nature of some liquids, the outer sheath can be stainless steel.

Magnesium oxide is used as an insulator around the internal heating elements to transfer heat and provide a voltage barrier between the electric filament and the outside sheath.  The insulating fibers are used in furnaces and other vessel linings due to their unique properties.

Connections to the tubular heaters

Tubular heaters have a terminal pin at both ends of the sheath for attaching 16 AWG power wiring.  This can be accomplished with an HPN power cord.

Applications

• Outside electrical control enclosures
• Foodservice equipment
• Paint curing equipment
• Steam tables
• Sterilizers and autoclaves
• Textile and chemical dryers
• Epoxy curing
• Hopper and silo heaters
• Stretch wrapping machines

DBK USA tubular heater for enclosure heating

The tubular heater has an adjustable integrated adjustable thermostat intended to provide thermal and humidity control within enclosures.  The required enclosure temperature can be easily set by adjusting the knob on the thermostat control.

Models have power output ranges from 100 to 500 W for both 120 and 240 volts.  Operating temperature ranges from 0 degrees F to 194 degrees F.

All models are of identical size and construction with an aluminized steel frame for durability and isolating the heating sheath from human touch.

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