Abstract: A fan control system has a fan duct, a fan mounted in the duct, an electronic commutator (EC) motor for driving the fan, and a control system hub for controlling the EC motor. A pressure differential sensing system is mounted in association with duct and feeding a pressure differential signal to the control system hub. An input device mounted on the control system hub for scaling an output signal from a low percent extreme to a high percent extreme and sends that output signal to the EC motor. Wherein the control system hub speeds, slows or switches OFF the EC motor according to the pressure differential signal except that the input device sets a speed limit ceiling on the EC motor.

Abstract: Exhaust apparatus for exhausting “dirty” exhaust gases accept a core flow of such exhaust gases and combine that with an annularly-surrounding “rooftop” flow of ambient air for diluting the exhaust gases as well as expelling the diluted flow in a forcibly expelled plume in order to ensure that the “effective” expulsion distance of the expelled diluted flow is at least the physical length of the exhaust apparatus plus the gains gotten from efflux velocity and flowrate.

Abstract: An exhaust fan has an annular exhaust duct, a fan wheel, and a drive motor inside the core of the exhaust duct, and not inside the annular passage for the exhaust fluid. The exhaust duct has a tubular window frame extending between the inner and outer walls of the exhaust duct and creating service windows for a worker to reach in an de-couple the driver motor from both a bracket for its mount and also from the fan wheel. Temporary locking mechanisms actuated from reaching through the service windows removably hold the fan wheel to the exhaust duct while the drive motor is de-coupled and removed. The exhaust fan further includes self-centering mechanical connections between the drive motor and fan wheel so that the fan wheel does not have to be removed to be re-balanced.

Abstract: A mixed flow fan wheel has a convex hub, an axially-spaced away concave annular shroud, and a plurality of angularly distributed blades extending between and interconnecting the hub and shroud, all which cooperatively define a plurality of inter-blade flow channels. Each has a pressure surface and spaced suction surface extending not only between spaced inlet and discharge edges but also, crosswise thereto, spaced hub-side and shroud-side edges. Each discharge edge is convex relative a center of geometry of the blade therefor. Each inter-blade flow channel originates in a generally rectangular shape between flanking inlet edges and terminates in another generally rectangular shape between flanking discharge edges, with a procession of gradations of generally rectangular shapes forming a progressive transition therebetween. Moreover, each inter-blade flow channel twists or corkscrews from inlet thereof to the discharge.

Abstract: Exhaust apparatus for exhausting “dirty” exhaust gases accept a core flow of such exhaust gases and combine that with an annularly-surrounding “rooftop” flow of ambient air for diluting the exhaust gases as well as expelling the diluted flow in a forcibly expelled plume in order to ensure that the “effective” expulsion distance of the expelled diluted flow is at least the physical length of the exhaust apparatus plus the gains gotten from efflux velocity and flowrate.

Abstract: Roof curb structures include side shells made by cutting a series of transversely aligned V-shaped notches and straight slots along top and bottom edges of a continuous length of sheet metal strip material at spaced apart intervals corresponding to the length of each side of the side shells to be formed therefrom. Then the strip material is cut to length corresponding to the length of one, two or four sides of the side shells and the top and bottom edges are roll formed in opposite directions to form oppositely extending top and bottom flanges.