Fume hood energy controller

Claim 1

In a system for controlling the operation of a fume hood wherein the fume hood includes a first high volume fan disposed in a first duct to draw air through the hood and a sash slideably mounted in the hood the improvement which comprises; (a) a second duct to bypass the high volume fan; (b) a second continuously operating low volume fan secured within the bypass duct; (c) a damper disposed in the first duct upstream of the first fan; (d) means to sense the pressure within the first duct and to provide an alarm output if the pressure violates a pre-established level which violation corresponds to an alarm condition; (e) means to sense the position of the sash in a first closed position; (f) means to sense the position of the sash in a second open position; (g) means to actuate the damper between an open position when the sash is in its open position, and to actuate the damper to a closed position when the sash is its closed position; (h) status alarms; and (i) means in communication with the first fan, the means to sense the pressure and the means to sense the position of the sash and the status alarms to i. actuate the status alarms when a pressure alarm is sensed and the first fan is operating; ii. to actuate the first fan to a non-operating mode when the position of the sash in the first position is sensed; and iii. to actuate the first fan to an operating mode when the sash moves from its closed to its open position; and iv. to actuate the status alarm when the position of the sash exceeds the second position.