Fuel burner control system with hot surface ignition

Claim 2

In a fuel burner control system including a burner, valve means controlling the flow of fuel to the burner, and an electrical resistance igniter connected across a power source for igniting fuel at the burner, the improvement comprising: control means for effecting energizing of the igniter in a first burner cycle so as to cause said igniter to attain ignition temperature, for effecting reduction of said energizing in subsequent successive burner cycles in which ignition is successful until a burner cycle occurs in which ignition is not successful, and for subsequently effecting an increase of said energizing so as to cause said igniter to be heated to a desired value of said ignition temperature.

Claim 3

An improved method for controlling energizing of an electrical resistance igniter in a fuel burner control system, comprising the steps of: energizing the igniter in a first burner cycle at a level of energizing adequate to cause said igniter to be heated to a temperature sufficiently high to ignite the fuel; reducing said level of energizing in subsequent successive burner cycles in which ignition occurs until an unsuccessful burner cycle occurs in which ignition does not occur; and subsequently increasing said reduced level of energizing so as to establish a level of energizing which will cause said igniter to be heated to a desired temperature value effective to ignite said fuel.

Claim 4

An improved method for controlling energizing of an electrical resistance igniter in a fuel burner control system, comprising the steps of: energizing the igniter in a first burner cycle at a level of energizing adequate to cause said igniter to be heated to a temperature sufficiently high to ignite the fuel; reducing said level of energizing in subsequent successive burner cycles in which ignition occurs until an unsuccessful burner cycle occurs in which ignition does not occur; and subsequently increasing said reduced level of energizing so as to establish a level of energizing which will cause said igniter to be heated to a desired temperature value effective to ignite said fuel.

Claim 5

In a fuel burner control system, a burner; valve means controlling the flow of fuel to said burner; an electrical resistance igniter for igniting fuel at said burner; switching means connecting said igniter across an alternating current power source; circuit means for controlling conduction of said switching means; circuit means for sensing voltage applied to said igniter; and a microcomputer connected to said circuit means for controlling conduction of said switching means and to said circuit means for sensing voltage applied to said igniter, said microcomputer including program means for establishing a warm-up time period, for effecting conduction of said switching means and thereby effecting energizing of said igniter during said warm-up time period so as to cause said igniter to attain ignition temperature, and for determining the length of said warm-up time period in response to voltage values sensed by said circuit means for sensing voltage applied to said igniter and in response to a learning routine, said learning routine being effective to cause said igniter, after successive ignition attempts, to be heated to a desired value of said ignition temperature, said learning routine including an offset function, said offset function including a count in a counter in said microcomputer, said count having an initial value when power is initially applied to effect initialization of said microcomputer, said count being decremented upon the occurrence of each of said successive ignition attempts after said initialization which result in ignition, and said count being subsequently incremented upon the occurrence of a first ignition attempt which does not result in ignition.

Claim 6

In a fuel burner control system, a burner; valve means controlling the flow of fuel to said burner; an electrical resistance igniter for igniting fuel at said burner; switching means connecting said igniter across an alternating current power source; circuit means for controlling conduction of said switching means; circuit means for sensing voltage applied to said igniter; and a microcomputer connected to said circuit means for controlling conduction of said switching means and to said circuit means for sensing voltage applied to said igniter, said microcomputer including program means for establishing a warm-up time period, for effecting conduction of said switching means and thereby effecting energizing of said igniter during said warm-up time period so as to cause said igniter to attain ignition temperature, and for determining the length of said warm-up time period in response to voltage values sensed by said circuit means for sensing voltage applied to said igniter and in response to a learning routine, said learning routine being effective to cause said igniter, after successive ignition attempts, to be heated to a desired value of said ignition temperature, said learning routine including an offset function, said offset function including a count in a counter in said microcomputer, said count having an initial value when power is initially applied to effect initialization of said microcomputer, said count being decremented upon the occurrence of each of said successive ignition attempts after said initialization which result in ignition, and said count being subsequently incremented upon the occurrence of a first ignition attempt which does not result in ignition.

Claim 7

The control system claimed in claim 3 wherein, after said count has been subsequently incremented upon said occurrence of a first ignition attempt which does not result in ignition, said count is prevented from decrementing for a predetermined number of ignition attempts.

Claim 8

In a fuel burner control system, a burner; valve means controlling the flow of fuel to said burner; an electrical resistance igniter for igniting fuel at said burner; switching means connecting said igniter across an alternating current power source; circuit means for controlling conduction of said switching means; circuit means for sensing voltage applied to said igniter; and a microcomputer connected to said circuit means for controlling conduction of said switching means and to said circuit means for sensing voltage applied to said igniter, said microcomputer including program means for establishing a warm-up time period, for effecting conduction of said switching means and thereby effecting energizing of said igniter during said warm-up time period so as to cause said igniter to attain ignition temperature, and for determining the length of said warm-up time period in response to voltage values sensed by said circuit means for sensing voltage applied to said igniter and in response to a learning routine, said learning routine being effective to cause said igniter, after successive ignition attempts, to be heated to a desired value of said ignition temperature, said switching means comprising two triacs, one of said triacs being connected to one side of said igniter and the other of said triacs being connected to the opposite side of said igniter, said microcomputer including program means for effecting alternate conduction of said triacs during a time period when said igniter is de-energized and being responsive, during said alternate conduction, to a value of voltage sensed by said circuit means for sensing voltage applied to said igniter, so that said program means is effective for determining whether said triacs are half-waving or are shorted.

Claim 9

In a fuel burner control system, a burner; valve means controlling the flow of fuel to said burner; an electrical resistance igniter for igniting fuel at said burner; switching means connecting said igniter across an alternating current power source; circuit means for controlling conduction of said switching means; circuit means for sensing voltage applied to said igniter; and a microcomputer connected to said circuit means for controlling conduction of said switching means and to said circuit means for sensing voltage applied to said igniter, said microcomputer including program means for establishing a warm-up time period, for effecting conduction of said switching means and thereby effecting energizing of said igniter during said warm-up time period so as to cause said igniter to attain ignition temperature, and for determining the length of said warm-up time period in response to voltage values sensed by said circuit means for sensing voltage applied to said igniter and in response to a learning routine, said learning routine being effective to cause said igniter, after successive ignition attempts, to be heated to a desired value of said ignition temperature, said switching means comprising two triacs, one of said triacs being connected to one side of said igniter and the other of said triacs being connected to the opposite side of said igniter, said microcomputer including program means for effecting alternate conduction of said triacs during a time period when said igniter is de-energized and being responsive, during said alternate conduction, to a value of voltage sensed by said circuit means for sensing voltage applied to said igniter, so that said program means is effective for determining whether said triacs are half-waving or are shorted.

Claim 10

In a fuel burner control system, a burner; valve means controlling the flow of fuel to said burner; an electrical resistance igniter for igniting fuel at said burner; switching means connecting said igniter across an alternating current power source; circuit means for controlling conduction of said switching means; circuit means for sensing voltage applied to said igniter; and a microcomputer connected to said circuit means for controlling conduction of said switching means and to said circuit means for sensing voltage applied to said igniter, said microcomputer including program means for establishing a warm-up time period, for effecting conduction of said switching means and thereby effecting energizing of said igniter during said warm-up time period so as to cause said igniter to attain ignition temperature, and for determining the length of said warm-up time period in response to voltage values sensed by said circuit means for sensing voltage applied to said igniter and in response to a learning routine, said learning routine being effective to cause said igniter, after successive ignition attempts, to be heated to a desired value of said ignition temperature, said switching means comprising two triacs, one of said triacs being connected to one side of said igniter and the other of said triacs being connected to the opposite side of said igniter, said microcomputer including program means for effecting simultaneous conduction of said triacs during a time period when said igniter is energized and being responsive, during at least a portion of the time when said simultaneous conduction is occurring, to a value of voltage sensed by said circuit means for sensing voltage applied to said igniter, so that said program means is effective for determining whether said triacs are half-waving or are shorted.

Claim 11

In a fuel burner control system, a burner; valve means controlling the flow of fuel to said burner; an electrical resistance igniter for igniting fuel at said burner; switching means connecting said igniter across an alternating current power source; circuit means for controlling conduction of said switching means; circuit means for sensing voltage applied to said igniter; and a microcomputer connected to said circuit means for controlling conduction of said switching means and to said circuit means for sensing voltage applied to said igniter, said microcomputer including program means for establishing a warm-up time period, for effecting conduction of said switching means and thereby effecting energizing of said igniter during said warm-up time period so as to cause said igniter to attain ignition temperature, and for determining the length of said warm-up time period in response to voltage values sensed by said circuit means for sensing voltage applied to said igniter and in response to a learning routine, said learning routine being effective to cause said igniter, after successive ignition attempts, to be heated to a desired value of said ignition temperature, said switching means comprising two triacs, one of said triacs being connected to one side of said igniter and the other of said triacs being connected to the opposite side of said igniter, said microcomputer including program means for effecting simultaneous conduction of said triacs during a time period when said igniter is energized and being responsive, during at least a portion of the time when said simultaneous conduction is occurring, to a value of voltage sensed by said circuit means for sensing voltage applied to said igniter, so that said program means is effective for determining whether said triacs are half-waving or are shorted.

Claim 12

The control system claimed in claim 6 wherein said program means for determining whether said triacs are half-waving or are shorted is concurrently effective for determining whether said igniter is open or not connected to said power source.

Claim 13

In a fuel burner control system, a burner; valve means controlling the flow of fuel to said burner; an electrical resistance igniter for igniting fuel at said burner; switching means connecting said igniter across an alternating current power source; circuit means for controlling conduction of said switching means; circuit means for sensing voltage applied to said igniter; and a microcomputer connected to said circuit means for controlling conduction of said switching means and to said circuit means for sensing voltage applied to said igniter, said microcomputer including program means for establishing a warm-up time period, for effecting conduction of said switching means and thereby effecting energizing of said igniter during said warm-up time period so as to cause said igniter to attain ignition temperature, and for determining the length of said warm-up time period in response to voltage values sensed by said circuit means for sensing voltage applied to said igniter and in response to a learning routine, said learning routine being effective to cause said igniter, after successive ignition attempts, to be heated to a desired value of said ignition temperature, said valve means being electrically operated, said control system further including two sets of series-connected normally-open relay contacts connecting said valve means across said power source, two relay coils for controlling said two sets of relay contacts, and relay contact checking circuit means connected between said microcomputer and said two sets of relay contacts, said microcomputer including program means for effecting alternate closing of said two sets of relay contacts, and being responsive to said relay contact checking circuit means during said alternate closing for determining whether one or both of said two sets of relay contacts are closed when they should be open.

Claim 14

In a fuel burner control system, a burner; valve means controlling the flow of fuel to said burner; an electrical resistance igniter for igniting fuel at said burner; switching means connecting said igniter across an alternating current power source; circuit means for controlling conduction of said switching means; circuit means for sensing voltage applied to said igniter; and a microcomputer connected to said circuit means for controlling conduction of said switching means and to said circuit means for sensing voltage applied to said igniter, said microcomputer including program means for establishing a warm-up time period, for effecting conduction of said switching means and thereby effecting energizing of said igniter during said warm-up time period so as to cause said igniter to attain ignition temperature, and for determining the length of said warm-up time period in response to voltage values sensed by said circuit means for sensing voltage applied to said igniter and in response to a learning routine, said learning routine being effective to cause said igniter, after successive ignition attempts, to be heated to a desired value of said ignition temperature, said valve means being electrically operated, said control system further including two sets of series-connected normally-open relay contacts connecting said valve means across said power source, two relay coils for controlling said two sets of relay contacts, and relay contact checking circuit means connected between said microcomputer and said two sets of relay contacts, said microcomputer including program means for effecting alternate closing of said two sets of relay contacts, and being responsive to said relay contact checking circuit means during said alternate closing for determining whether one or both of said two sets of relay contacts are closed when they should be open.

Claim 15

The control system claimed in claim 8 wherein said microcomputer includes program means for effecting simultaneous closing of said two sets of relay contacts and being responsive to said relay contact checking circuit means during said simultaneous closing for determining whether one or both of said two sets of relay contacts are open when they should be closed and for determining whether said relay contact checking circuit means is functioning properly.

Claim 16

The control system claimed in claim 9 wherein said microcomputer includes program means for effecting energizing of at least one of said relay coils at a frequency considerably higher than the frequency of said power source upon initiation of said simultaneous closing and for subsequently reducing said frequency to a lower value.

Claim 17

In a fuel burner control system, a burner; valve means controlling the flow of fuel to said burner; an electrical resistance igniter for igniting said fuel at said burner; a pair of solid-state switches connecting said igniter across an alternating current power source; voltage sensing circuit means connected across said igniter; means for effecting simultaneous conduction of each of said solid-state switches to enable energizing of said igniter and for effecting alternating conduction of each of said solid-state switches during a time period when said igniter is to be de-energized; and means responsive to said voltage sensing circuit means for determining proper functioning of said pair of solid-state switches.

Claim 18

In a fuel burner control system, a burner; valve means controlling the flow of fuel to said burner; an electrical resistance igniter for igniting said fuel at said burner; a pair of solid-state switches connecting said igniter across an alternating current power source; voltage sensing circuit means connected across said igniter; means for effecting simultaneous conduction of each of said solid-state switches to enable energizing of said igniter and for effecting alternating conduction of each of said solid-state switches during a time period when said igniter is to be de-energized; and means responsive to said voltage sensing circuit means for determining proper functioning of said pair of solid-state switches.

Claim 19

The control system claimed in claim 11 wherein said pair of solid-state switches comprises two triacs.

Claim 20

The control system claimed in claim 12 wherein one of said triacs connects one side of said igniter to one side of said alternating current power source, and the other of said triacs connects the opposite side of said igniter to the other side of said alternating current power source.

Claim 21

The control system claimed in claim 11 further including means responsive to said voltage sensing circuit means for determining whether said igniter is open or not connected.

Claim 22

The control system claimed in claim 11 wherein said voltage sensing circuit means is effective to provide a characteristic representative of voltage value across said igniter.

Claim 23

The control system claimed in claim 11 wherein said voltage sensing circuit means is effective, during at least a portion of the time when said simultanous conduction is occurring, to provide signals representative of the times at which the voltage across said igniter increases beyond a predetermined value and decreases beyond said predetermined value, and further including means responsive to said signals for determining the value of said voltage across said igniter.