What Are Duct Heaters?

electric inline duct heater

Duct heaters are the part of your HVAC that preheats the air before it is being distributed to the rooms of your property. The most common type is the electrical duct heaters. They create heat while passing an electric current through resistance (coils). The air passing through absorbs the heat out of the coils and it is then pushed through the ductwork into your rooms. Inline electric duct heaters can be used for space, supplementary, and primary heating applications.

Besides the heating coils, the electrical duct heaters have a couple of additional features. They can be programmed to heat the air only in specific times of the day, or after temperatures drop below a pre-setted value. The optimal temperature could be kept by automatically switching the heaters on and off, in compliance with readings from climate control systems. This makes inline electric heaters highly energy efficient.

These devices also have a set of switches meant for safety features. The first switch automatically switches off the heater after the maximum temperature is reached. The second is a manual switch with which the heaters could be turned off in case of malfunction in the automatic system. Simpler models have a set of stages. Every stage uses more energy to generate more heat. Those stages are usually three.

There are a couple of different types of duct heaters on the market:

  • Round duct heaters electric;
  • Rectangular;
  • Industrial duct heaters;
  • Standard & Custom duct heaters;
  • Explosion-proof heaters – designed for hazardous areas.


These devices may be installed in office buildings, schools, manufacturing facilities, power plants and many more. Duct heaters are relatively easy to install and replace. Mounting can be done with airflow in either direction using a standard spigot connection to spiral ducting. Electric in-line duct heaters should always be installed with the safety cut outs at the top of the unit.

*Pay close attention when choosing a replacement for a duct heater. These devices are designed according to dimensions, watts and current, so it is important to have the same model or at least one with the same stats.

Purpose of Duct Heaters

Duct heaters are a great way to keep rooms or even separate areas with different temperatures. They are easy to install and maintain. That fact, combined with their energy efficiency, is the reason why those devices find many applications. Regular maintenance is highly important. Whenever you have a heating element, you should check its condition often. At least before every winter season for domestic properties.


  • Primary heating;
  • Secondary heating;
  • Space heating;
  • Reheating;
  • Multi-zone and VAV heating.

There is a duct heater that is more or less suitable for each of those applications. In order to choose the right one, you might need some professional help. Whether you are choosing a heater for your new system or just need a spare for a malfunctioning one, our professionals can assist you at 01455 616444. Browse the duct heaters category on our website and if any questions arise don’t hesitate to give us a call.