Mixing box

Abstract

An improved induction mixing box and a method for operating it are disclosed. The mixing box is a double induction box in which secondary air is induced to flow into the box by induction nozzles, a fan, or both, for mixture with primary air and delivery thereof through an outlet end of the box to a room or zone of a building to be continued. Primary air flows into the box, at a controlled rate, through the induction nozzles and induces secondary air to flow into the box through a first opening for mixture with the primary air and delivery therewith through the outlet end of the box. The mixing box further comprises a fan for inducing a flow of air through a second opening for delivery through the outlet end of the box. According to the improvement, the box further comprises a closed second passage for the flow of air from the second opening to the suction side of the fan, a control for selectively activating the fan and a heat transfer device positioned in the closed second passage. According to the method for operating the improved mixing box, the flow of primary air through the inlet is varied, as a function of load, between a maximum rate and a minimum rate, as the load varies between a maximum and a minimum, and the fan is energized whenever the flow of primary air and induced air is inadequate to provide adequate circulation.