WATTCO Tubular Duct Heaters

Whether it’s an open coil duct heater, a tubular or a finned tubular duct heater, each duct heater serves the main purpose which remains the same – to heat up a large area in the most efficient and economical method. However, the type may vary based on their construction, advantages, disadvantages and functionality differences. Construction and Working of Duct Heaters Tubular duct heaters are electric heat transferring products whose construction is composed of various components that include a terminal housing, individual elements and controls. At the tubular center, it has a heating resistive wire made of chrome and nickel alloy. Magnetic contactors can be present to ensure full power cut-off when needed. The power wiring is also set to standard values to meet your industrial requirements. An airflow switch is present to provide proper air flow near the heating elements. An automatic switch is present called primary thermal switch which is used to stop the whole unit when the temperature limit is reached to maximum value. As soon as the value of temperature comes below the maximum limit, the switch is reset on its own. Similar switch is present which is operated manually. It is called secondary thermal cut-off. A disconnect switch is present to interrupt the electric power supply at the time of heater’s service and maintenance. There is another relay whose purpose is to make sure the fan is ready and energized before the heater. This relay is called fan interlock relay. The duct heater has bushings to bear the mechanical stress on device. These bushings are made of steatite ceramic due to its high value of dielectric strength and resistivity to mechanical and thermal shocks. The terminals of open coils are composed of steatite as well, while those of tubular duct heaters are not. This way these insulators give secure and safe electrical power transfer between elements and the control panel. A transformer is also present with a primary voltage rating of 120-600 volts. To protect the aluminum and copper wires, there is a protective covering in the form of a terminal block made of stainless steel. A ground connection is also present for extra safety. Types of Duct Heaters There are various types of duct heaters. Some of the commonly used duct heaters are named below. Tubular Duct Heaters Finned Tubular Duct Heaters Open Coil Duct Heaters Constructional Difference between Tubular Duct Heaters and Finned Tubular Duct Heaters The main difference are the fins that are present around tubular elements. Each fin wraps around the tubular element in order to maximize the surface area of a tubular element. The heat that is generated is then dissipated more quickly and, increases the life of the tubular element. Steel fins are normally used in cases where there is low moisture areas. They are also a good heat transfer source as oppose to stainless steel fins. Stainless steel fins have other advantages such as their rigidity in processes that have more vibrations. Dimensions The following dimensions are same for all tubular heaters Diameter of Tube (inches)– 0.260, 0.315, 0.375, 0.430, 0.475 The most commonly used are 0.315 inches and 0.430 inches. However, the extra dimension added in this type of tubular heater is that of fins. Typical Thickness of Fin (inches)– 0.020 Typical Number of Fins/ inch– 5 Typical Width of Fin (inches)– 0.375 Sizes: The following dimensions may be changed as per individual requirements. Total value of Square Inch/linear inch-8.30, 9.20, 10.10, 10.83, 11.60 Maximum length of Sheath (inches) – 240 Minimum length of Sheath (inches)– 11 Outer diameter of Fins (inches)– 1.01, 1.07, 1.13, 1.18, 1.23 Voltages Shown below are the maximum values of voltage for duct heaters. Maximum value of Voltage (volts)-120, 240, 300, 480, 600 Wattages Maximum value of wattages can be: Maximum value of Wattage (watts)-3600W, up to 2 MW Favorable Features of Tubular Duct Heaters The tubular duct heaters provide a great mechanical strength, preferable for harsh environments. They are not prone to moisture and dust that easily. These duct heaters are quite easy to mount. They are durable and require easy maintenance The presence of variety of termination styles makes this heater flexible in use. Specifications: Tubular Duct Heaters are rigid to withstand harsh environments They can be used as supplemental duct heaters to an existing system Typically used for outdoor applications or in environments that are too harsh for open coil elements Can be manufactured in Steel, Stainless Steel, Incoloy or Titanium materials Reinforced frame allows for minimum vibration and elevated temperatures Sturdy support brackets allow for easy replacement of elements when needed