Abstract A flow control device is provided for use with a fan to prevent pressure excursions in a furnace or any other hardware equipment to which the fan is connected. The control device is connected in parallel relation with respect to the fan so that a recirculating flow path is formed between an outlet of the fan and an inlet thereof. This recirculating flow path controls the pressure differential produced by the fan. The control device includes duct work and a controlled element, preferably, a damper. In a furnace system, an induced draft fan is connected in series with a furnace and the controlled device is normally in a closed position in parallel with the induced draft fan. Upon the occurrence of one or more predetermined fault conditions, the controlled device modulates open to provide a circulating path through the induced draft fan and rapidly controls the pressure differential between the inlet and outlet of the fan. Since this pressure differential is maintained within a desirable range, the induced draft fan does not create too great a suction against the inner walls of the furnace.
Apparatus for preventing an excessive loss of pressure of a gaseous fluid in a duct on the inlet side of a fan comprising: a furnace having an outlet through which a gaseous fluid is discharge; a fan having an inlet for receiving said gaseous fluid and an outlet for discharging said gaseous fluid; a duct for connecting said outlet of said furnace and said inlet of said fan and for providing a passageway for said gaseous fluid from said furnace to said fan; another duct for connecting said outlet of said fan to said duct for connecting said outlet of said furnace and said inlet of said fan and for providing a passageway for at least a portion of said gaseous fluid being discharged from said fan; a louvered damper capable of movement between a fully closed position and a fully opened position for controlling the amount of gaseous fluid flowing through said duct from said outlet of said fan to said duct for connecting said furnace to said inlet of said fan; and wherein said damper is responsive to the pressure in said furnace.
Claim 2
Dependent Claim
185 words
Apparatus for preventing an excessive loss of pressure of a gaseous fluid in a duct on the inlet side of a fan comprising: a furnace having an outlet through which a gaseous fluid is discharge; a fan having an inlet for receiving said gaseous fluid and an outlet for discharging said gaseous fluid; a duct for connecting said outlet of said furnace and said inlet of said fan and for providing a passageway for said gaseous fluid from said furnace to said fan; another duct for connecting said outlet of said fan to said duct for connecting said outlet of said furnace and said inlet of said fan and for providing a passageway for at least a portion of said gaseous fluid being discharged from said fan; a louvered damper capable of movement between a fully closed position and a fully opened position for controlling the amount of gaseous fluid flowing through said duct from said outlet of said fan to said duct for connecting said furnace to said inlet of said fan; and wherein said damper is responsive to the pressure in said furnace.
Claim 3
Dependent Claim
13 words
Apparatus as in claim 1 wherein: said fan is an induced draft fan.
Claim 4
Dependent Claim
14 words
Apparatus as in claim 1 wherein: said louvered damper has a plurality of vanes.
Claim 5
Dependent Claim
24 words
Apparatus as in claim 1 wherein: the cross-sectional area of said louvered damper is less than the cross-sectional area of any of said ducts.