The fume hood application regulates exhaust flow to a setpoint selected according to several selectable strategies. The strategies determine the required exhaust flow setpoint using sensors and indications from the fume hood user at the ODP.
Sash sensing
The application uses one or two sensors two indicate the position of a sash or sashes that move vertically. The modulating exhaust flow setpoint can be calculated directly from sash position or through face area calculations for a constant face velocity. Configurable minimum and maximum flow limits apply to either strategy.
Face velocity sensing
The application uses a velocity sensor, installed through the wall of the fume hood, to represent face velocity. A control loop modulates the exhaust flow setpoint to maintain the indicated velocity at the face velocity setpoint. Configurable minimum and maximum flow limits apply to either strategy.
Face velocity sensing may be combined with sash sensing.