Furnace control using induced draft blower and exhaust gas differential pressure sensing
AssigneeHoneywell Inc.
InventorLorne W. Nelson
Life of this patent
Estimating the term…
Abstract
A heating system of the type having a combustion chamber with a fuel burner, an inlet for combustion air and an exhaust stack is improved by adding a variable-speed induced draft blower, a flow-restricting stack orifice and a fuel valve sensitive to the exhaust gas flow rate through the stack orifice. The fuel valve turns on at a first predetermined exhaust gas flow rate and turns off at a second predetermined exhaust gas flow rate, which is lower than the first predetermined rate. The fuel valve also supplies fuel at a rate proportional to the exhaust gas flow rate. Sensing of the differential pressure across the stack orifice is used to determine the exhaust gas flow rate.
Claims13
In a heating system of the type having a combustion chamber with a fuel burner, an inlet for combustion air, and an exhaust stack for exhaust gas, the improvement comprising:
- a blower connected to the exhaust stack for inducing exhaust gas flow through the exhaust stack and for drawing combustion air into the combustion chamber;
- means for variably controlling the flow of exhaust gas such that flow of exhaust gas through the exhaust stack and of combustion air into the combustion chamber are simultaneously regulated;
- means adapted to be mounted in the exhaust stack for forming a flow restriction in the exhaust stack on one side of the blower, said flow restriction, in cooperation with said blower, causing a pressure differential between the exhaust gas pressures on either side of the flow restriction;
- first fuel supply control means having an "on" state and an "off" state and being adapted to control the supply of fuel to the burner responsive to a control signal representative of the exhaust gas pressure differential across the flow restriction, whereby said first control means is turned "on" when the pressure differential exceeds a first, predetermined value and is turned "off" when the pressure differential falls below a second, predetermined value, which is less than said first predetermined value;
- second fuel supply control means adapted to variably control the supply of fuel to the burner responsive to the state of the first fuel supply control means and to a control signal representative of the exhaust gas pressure differential across the flow restriction, whereby the supply of fuel is regulated to a rate proportional to the magnitude of the pressure differential during the period when said first control means is "on";
- and
- means for sensing the exhaust gas pressure differential across the flow restriction and for communicating said sensed pressure differential as a control signal to the first and second fuel supply control means.
Dependencies are inferred from the claim text.