As a non-recirculating air door is put into operation, air is brought into the unit through the intake, enters the fan housing, and is accelerated by the fan. This fast moving air goes into a plenum, which allows for an even distribution of air along the full length of the discharge nozzle. Aerofoil shaped vanes in the nozzle create a uniform air stream with a minimum of turbulence.
The air discharged through the nozzle creates a jet stream to the floor. Approximately 80% of the air returns to the intake side of the air door, and 20% goes in the opposite direction.
For efficient air door performance, the angle of the discharge nozzle must be set correctly. An air door nozzle should be adjustable to aim inward or outward up to 20° from the opening.
Non-recirculating air doors can be mounted horizontally above the door or vertically on one or both sides of the door, depending on the space available and the height, width, and physical characteristics of the opening. Horizontal mounting above the door minimizes the chances of damaging the air door. Protective measures should be taken if the air door is mounted vertically.
There are four basic categories of non-circulating air doors to meet various needs:
The proper size, power rating, and features needed for a particular air door application should be selected according to the following considerations.