Air duct electric heaters are mainly used for heating air in ducts, available in three types: low temperature, medium temperature, and high temperature. Their common structural feature is the use of steel plates to support the electric heating tubes to minimize vibration, with over-temperature control devices installed in all junction boxes.

The duct electric heater is equipped with not only over-temperature protection but also a linkage device between the fan and heater to ensure the electric heater starts after the fan. A differential pressure device is added before and after the heater to prevent fan failure. The pressure of the gas heated by the duct heater should generally not exceed 0.3 Kg/cm2; for pressures above this, please choose a circulating electric heater. The low-temperature type heater does not exceed 160℃ for gas heating temperature; the medium-temperature type does not exceed 260℃; and the high-temperature type does not exceed 500℃. The duct electric heater is used in industrial ducts, air conditioning ducts, and various industries to heat air through air passage, increasing the temperature of the output air. It is usually inserted into the transverse opening of the duct. It is divided into low, medium, and high temperatures according to the working temperature of the duct; and into low, medium, and high air velocities according to the air velocity inside the duct.