FURNACE CONTROL USING INDUCED DRAFT BLOWER AND EXHAUST GAS DIFFERENTIAL PRESSURE SENSING

摘要

FURNACE CONTROL USINGINDUCED DRAFT BLOWER AND EXHAUST GASDIFFERENTIAL PRESSURE SENSINGAbstract of the DisclosureA heating system of the type having a combustionchamber with a fuel burner, an inlet for combustion airand an exhaust stack is improved by adding a variable-speed induced draft blower, a flow-restricting stackorifice and a fuel valve sensitive to the exhaust gas flowrate through the stack orifice. The fuel valve turns onat a first predetermined exhaust gas flow rate and turnsoff at a second predetermined exhaust gas flow rate, whichis lower than the first predetermined rate. The fuelvalve also supplies fuel at a rate proportional to theexhaust gas flow rate. Sensing of the differentialpressure across the stack orifice is used to determine theexhaust gas flow rate.