Flow control system

• US 5,819,721 A
• Filed: 12/18/1996
• Issued: 10/13/1998
• Est. Priority Date: 01/26/1995
• Status: Expired due to Term

• Current Assignee: Honeywell International Inc.
• Original Assignee: Tridelta Industries, Inc. (Honeywell International Inc.)
• Inventors: Mizerak, Dennis S., Carr, Larry L.
• Primary Examiner(s): Dority, Carroll B.
• Application Number:
  US08/768,952
• Time in Patent Office: 664 Days
• Field of Search: 73/722, 73/716, 126/116 A, 126/110 R, 431/20
• US Class Current: 126/116.00A
• CPC Class Codes: F23N 1/022 using electronic means
• CPC Class Codes: F23N 2005/181 using detectors sensitive to rate of flow of air
• CPC Class Codes: F23N 2005/182 Air flow switch
• CPC Class Codes: F23N 2225/02 filling height in burners
• CPC Class Codes: F23N 2225/04 pressure
• CPC Class Codes: F23N 2227/02 Starting or ignition cycles
• CPC Class Codes: F23N 2227/04 Prepurge
• CPC Class Codes: F23N 2227/22 Pilot burners
• CPC Class Codes: F23N 2233/04 with variable speed
• CPC Class Codes: F23N 2233/10 forcing air through heat exchangers
• CPC Class Codes: F23N 2235/16 variable flow or proportional valves
• CPC Class Codes: F23N 2235/18 Groups of two or more valves
• CPC Class Codes: F23N 2237/02 two or more burners
• CPC Class Codes: F24H 15/20 characterised by control inputs
• CPC Class Codes: F24H 15/35 Control of the speed of fans
• CPC Class Codes: F24H 15/36 of burners
• CPC Class Codes: F24H 15/414 using electronic processing, e.g. computer-based
• CPC Class Codes: F24H 9/2085 using fluid fuel

Abstract

A control system for regulating a flow rate of a heat transfer fluid in a heat transfer system, the heat transfer system having a heat transfer fluid flow path, flow control device for creating flow along the path, a fuel source for providing a combustible fuel to the path, an air source for providing combustion air to the path, and an assembly for combusting the fuel and air, the control system comprising a sensor for sensing a measured flow value at the air source, a controller for storing an optimum flow value at the air source and for storing a range of operating control values for the flow control device, the operating control values corresponding to the optimum flow value, a system for calculating a deviation between the measured flow value and the optimum flow value, and a system for varying the operation of the flow control means in accordance with the deviation.

Claims

1. A heating apparatus including:

a combustion air inlet;

a burner assembly for receiving a flow of combustion air and for burning a mixture of combustion air and combustible fluid to produce a combusted fluid air mixture;

a heat exchanger defining a path for a flow of combusted fluid air mixture therethrough;

a variable motor-driven fan for creating a flow of the combustion air through said burner assembly and for providing a flow of the combusted fluid air mixture along said path through said heat exchanger;

a pressure sensing system for determining a difference in pressure between two positions along said path and for providing a series of pulses having a frequency related to said difference in pressure;

a microprocessor control system comprising;

means for converting the series of pulses into an indication of the difference in pressure,

means for storing at least one predetermined pressure differential value,

means for determining a deviation between the indication of difference in pressure and the at least one predetermined pressure differential value, and

means operatively connected to said motor-driven fan for adjusting the difference in pressure between the two positions along said heat exchanger in accordance with said deviation.

2. A heating apparatus as defined in claim 1, wherein said motor-driven means for creating a flow of the combustion air is driven by a SR motor.

3. A heating apparatus as defined in claim 1, wherein said means for adjusting controls the motor-driven means to adjust the flow of the combustion air, flow of combustible fluid air mixture and flow of combustion byproducts.

4. A controller for regulating a combusted fluid flow rate in a combustion system having a heat exchanger, a variable speed inducer motor, a variable gas flow regulator, said controller comprising:

means for storing a gas pressure differential value and a corresponding air pressure differential value, for a plurality of heat demand values;

a first sensor for sensing a first measured pressure differential across the heat exchanger and for providing series of pulses having a frequency related to the first measured pressure differential;

means for determining a time to count a predetermined number of said series of pulses and for converting said time into an indication of the first measured pressure differential;

a second sensor for sensing a second measured pressure differential across the variable gas flow regulator and for providing a second signal output that is related thereto;

calculation means for calculating a first deviation between the indication of first measured pressure differential and the stored air pressure differential value and a second deviation between the second signal output and the stored gas pressure differential value; and

means for changing the combustion flow rate in accordance with said first and second deviations.

5. A controller as defined in claim 4, wherein said means for changing the combustion flow rate changes the speed of the variable speed inducer motor.

6. A controller as defined in claim 4, wherein said means for changing the combustion flow rate changes the flow of fluid through said fluid flow regulator.