Air handling unit including control system that prevents outside air from entering the unit through an exhaust air damper

A control system for controlling air flow through an air handling unit over a plurality of control states, said control system comprising:

• a supply fan, said supply fan providing supply air within the air handling unit;
• a return fan, said return fan providing return air within the air handling unit;
• an exhaust air damper, said exhaust air damper being positionable to control the amount of the return air that is emitted from the air handling unit;
• a recirculation air damper, said recirculation air damper being positionable to control the amount of the return air that is recirculated in the air handling unit;
• an outside air damper, said outside air damper being positionable to allow outside air into the air handling unit;
• and
• a controller means for controlling the position of the exhaust air damper and the recirculation air damper relative to each other to control the amount of outside air emitted into the air handling unit through the outside air damper, and for controlling the outside air damper to be in a substantially completely open position for all of the plurality of control states so as to prevent outside air from entering the air handling unit through the exhaust air damper.

A control system for controlling air flow through an air handling unit over a plurality of control states, said control system comprising:

• a supply fan, said supply fan providing supply air within the air handling unit;
• a return fan, said return fan providing return air withing the air handling unit;
• an exhaust air damper, said exhaust air damper being positionable to control the amount of the return air that is emitted from the air handling unit;
• a recirculation air damper, said outside recirculation air damper being positionable to control the amount of the return air that is to be recirculated in the air handling unit;
• an outside air damper, said outside air damper being positionable to allow outside air into the air handling unit;
• and
• a controller including a plurality of feedback control devices, wherein as first feedback control device controls the supply fan, a second feedback control device controls the return fan, and a third feedback control device controls the position of the exhaust air damper and the recirculation air damper relative to each other, and wherein the controller maintains the outside air damper in a substantially completely open position through all of the plurality of control states.