Commonly used in shops, hotels, entrance halls and reception areas, and in workshops and warehouses, door heaters prevent exterior cold air from entering a large space every time the door is opened, and prevent the loss of heated air in the same way.
When a door is opened into a sealed building, a vacuum is created that encourages the movement of air. Installing a door heater disrupts this process and prevents the exchange of air from inside to outside. Door heaters can be gas-fired – using a gas flame to create heat, they can use boilers and steam as a heat source, or use an electric element to create heat. An air propeller, or fan, will be needed to force air across the door opening and to create enough resistance to prevent interior-exterior flow of air. Therefore, doorway dimensions need to be taken into consideration when determining size and capacity of door heaters to ensure adequate coverage.
Larger door openings such as warehouses or garages may require more than one heater, and these can be placed side by side to fully cover the open space. Door heaters are ceiling or wall mounted but for optimal performance and results should be placed as closely as possible to the top of the door.
Typically a switch is installed on the doorway, or connected to the opening mechanism of the door, that turns the door heater on each time the doors are opening and closing as this is when the barrier is required to prevent heat loss. The continual operating of the door heater would result in high energy expenditure and the potential for overheating within the space itself, therefore a trigger switch or sensor is a necessary part of the mechanism.
In door heaters, there are options for adjustable levels of heat and airflow. Some units can be run without the heating elements on, and therefore are able to be further used in summer months. In warmer weather, the purpose of a maintaining the interior temperature of a space to avoid extra energy loss is similar – to prevent the loss of the air temperature within the building (in this case cooled air) and to prevent the entry of the outside air. Another use for door heaters is for the general heating of a space when a high level of space heater is required. Some models of door heaters are adjustable and the heated air flow can be directed into a room rather than across the opening.