What is a duct heater and what is its main purpose?

Duct heaters are a type of heating device. They are primarily used to heat air in ducts and are available in three different sizes: low, medium, and high. Their common structural feature is the use of steel plates to support the heating tubes to reduce vibration when the fan is stopped. Both types also feature an over-temperature control device in the junction box. The low-temperature model can be installed directly in the duct, while the medium- and high-temperature models differ in their structure, featuring a 100mm thick insulation material sandwiched between the duct wall and the heater junction box. This reduces heat dissipation from the duct and the temperature within the wiring compartment.

Duct heater applications:

They are used for industrial ducts, room heating, large factory workshop heating, drying rooms, and for circulating duct air to provide a warm air temperature for heating purposes.

The main structure of the duct heater is a framed wall panel construction with an over-temperature protection device. If the heating temperature exceeds 120°C, an insulation or heat dissipation zone should be provided between the junction box and the heater, and the heater element should be equipped with a finned heat dissipation structure. Low- and medium-temperature duct electric heaters do not require insulation or radiators; heat dissipates naturally from the surface of the heater element. The electronic control and fan must be linked. Start the fan first, then the heater. The time difference must be at least 2 minutes.

Control-wise, a linkage is installed between the fan and heater to ensure the heater starts only after the fan is running. The fan must be turned off for at least 2 minutes after the fan stops to prevent overheating and damage.