GB2185609A

GB2185609A - Gas-fired heating appliance

Info

Publication number: GB2185609A
Application number: GB08700804A
Authority: GB
Inventors: Arthur Chesworth; Anthony Halewood
Original assignee: Robinson Willey Ltd
Current assignee: Robinson Willey Ltd
Priority date: 1986-01-18
Filing date: 1987-01-15
Publication date: 1987-07-22
Also published as: GB8601200D0; GB8700804D0; GB2185609B

Abstract

A burner bar 11 having an injector 14 provides flames 12. A flame-failure device 17 cuts off the gas supply when it detects the absence of a flame. If the oxygen supply is inadequate, then the flames tend to lift off the bar as shown at 20, at the end distant from the flame-failure device. A flame lift-off device 22 detects the flame lift-off and shuts off a combustion air fan 16. This drastically reduces the air supply, causing lift-off all along the bar and causing flame-failure device to close the gas valve. Thus a single gas valve is used to cut off gas supply when either absence of flame or the beginning of flame lift-off is detected. <IMAGE>

Description

SPECIFICATION Gas-fired heating appliance This invention relates to a gas-fired heating appliance of the kind incorporating a flame-failure device.

The invention provides a gas-fired heating appliance incorporating a flame-failure device which shuts down the appliance when a burner is ex tinguished,the appliance including aflamelift-off sensor located adjacent to the burner at or near the position at which the flame lift-off starts, and control means operating when a flame lift-off is sensed to stop a flow of combustion air.

The stopping of the combustion air leads to increased flame lift-offand the flames being extinguished, so that the flame-failure device operates to shut down the appliance. Thus the flame-failure device is given a dual purpose.

The stopping of the combustion airflow is preferably carried out by interrupting the operation of a combustion fan.

The burner may comprise a burner bar, having a gas injector and the flame-failure device at one end and the flame lift-off sensor at the other end. It has beenfoundthatflame lift-offstarts in a barburnerat the end distant from the injector. However, in other kinds of burnersimple observation will serveto det- erminethe position at which flame lift-off starts.

A specific embodiment ofthe invention is shown in the accompanying diagrammatic drawing of part of a gas-fired heating appliance, e.g. a fire or a boiler.

The appliance has a burner bar (11) having ports (notshown) through which a gas/air mixture is supplied to burn along a line at (12). Gas is supplied in pipe (13) to injector (14), while air is supplied to chamber(15) by a combustion fan (16). Athermo- electricflame-failure device comprises athermocouple (17) energizing directly or indirectly a solenoid (18). A gas valve (19) in pipe (13) is mounted to move with an armature (20) sliding in the solenoid.

Manually operable push button (21) can be used to open the valve (19) and slide the armature into the solenoid. If the thermocouple senses a high tem perature the consequent energization of solenoid (18) is sufficient to hold the valve open after it has been manually opened, but not enough to open the valve from the closed position unaided. The thermocouple (17) is located at a position where it will be heated by a flame, which may be a pilotlightorthe main burner array. If the flame is extinguished the solenoid energization ceases, the valve closes and the gas supply cut off. Such flame-failure devices are well known and are readily commercially available for fitting into gas boilers, water heaters, fires or cookers.

Normally with a burner bartheflames (12) sit close to the bar. If the oxygen supply is inadequate then the flames iift up from the bar, as shown at (20), the flames seeking more oxygen. An inadequate oxygen supply may be due to a number of different causes, including blockage or restriction of the exhaust pipe so that the through flow is restricted, failure or reduced output of the combustion fan (16), restriction of the inlet airopeningsforthe combustion fan, and vitiation (exhaustion) of the air in the room being supplied to the combustion fan.When a long ex- haust pipe (i.e. one metre or more) is used, the danger of restriction is increased, and it is accordingly more desirable than usual to provide safety means for cutting offthe gas when oxygen starvation is detected. Itisfound byobservationthatwhen aburner bar is subject two an increasingly inadequate air supply, the flames at the right hand end of the burner, shown at (20), lift off before those at the left hand end, as seen in the drawing, ie.e. the flames furthestfrom the injector (14) first show the effect of oxygen starvation. When a flame is burning with inadequate oxygen it produces poisonous carbon monoxide in its exhaust.If the exhaust pipe is not clearing the exhaust products properly, then there may be exhaust spillage into the room, which is unacceptable.

As shown in the drawing, a flame lift-off detecting device comprises a flame sensing probe (22) located at the right hand end ofthe burner bar (i.e. at the end furthestfrom the injector) and at the base of aflame when it is burning correctly close to the bar. An electrical control device (23) operates when the flame is burning correctly close to the burner ports to maintain a switch device (24) closed.

Switch (24) is connected in an electricalsupplyline (25) to motor (26) which drives the combustion fan (16). When flame (20) lifts, probe (22) senses electro nicallythattheflame is not present. The control device (23) then opens switch (24), thus cutting off the supply to motor (26) and stopping the fan (16). The air supply to all burners is thus stopped, all the flames lift and go out. Thermocouple (17) then senses that there is no flame, solenoid (18) falls out, gasvalve (19) closes andthe heating appliance is thus closed down.

For starting purposes switch (24) may be held closed by push button (27) until the flame has es tablished itself. Push button (27) may be the same or ganged with push button (21).

Thustheflame-failurevalve(19) is caused to operateto shut the appliance down on the occurrence offlame lift-off, so serving a dual purpose. In effect, when probe (22) senses any reduction in airflow, it operates to reduce the airflow still further to the point where the flame4ailure device operates. Because flame lift-off starts to occur at the opposite end of the burnerto that where the normal flame failure device thermocouple is situated the gas would not otherwise be shut off before the CO : CO2 ratio had exceeded the ratio permitted by the relevant British Standard.

The flame lift-off device is of the known kind working on the flame rectification principle. When aflame is present a small current is produced which is amplified to operate a switch.

1. A gas-fired heating appliance incoprorating a flame-failure device which operates to shut down the appliance when a burner flame is extinguished,the appliance including a flame lift-off sensor located to sense lifting ofthe burnerflame and means four

**WARNING** end of DESC field may overlap start of CLMS **.

Claims

**WARNING** start of CLMS field may overlap end of DESC **. SPECIFICATION Gas-fired heating appliance This invention relates to a gas-fired heating appliance of the kind incorporating a flame-failure device. The invention provides a gas-fired heating appliance incorporating a flame-failure device which shuts down the appliance when a burner is ex tinguished,the appliance including aflamelift-off sensor located adjacent to the burner at or near the position at which the flame lift-off starts, and control means operating when a flame lift-off is sensed to stop a flow of combustion air. The stopping of the combustion air leads to increased flame lift-offand the flames being extinguished, so that the flame-failure device operates to shut down the appliance. Thus the flame-failure device is given a dual purpose. The stopping of the combustion airflow is preferably carried out by interrupting the operation of a combustion fan. The burner may comprise a burner bar, having a gas injector and the flame-failure device at one end and the flame lift-off sensor at the other end. It has beenfoundthatflame lift-offstarts in a barburnerat the end distant from the injector. However, in other kinds of burnersimple observation will serveto det- erminethe position at which flame lift-off starts. A specific embodiment ofthe invention is shown in the accompanying diagrammatic drawing of part of a gas-fired heating appliance, e.g. a fire or a boiler. The appliance has a burner bar (11) having ports (notshown) through which a gas/air mixture is supplied to burn along a line at (12). Gas is supplied in pipe (13) to injector (14), while air is supplied to chamber(15) by a combustion fan (16). Athermo- electricflame-failure device comprises athermocouple (17) energizing directly or indirectly a solenoid (18). A gas valve (19) in pipe (13) is mounted to move with an armature (20) sliding in the solenoid. Manually operable push button (21) can be used to open the valve (19) and slide the armature into the solenoid. If the thermocouple senses a high tem perature the consequent energization of solenoid (18) is sufficient to hold the valve open after it has been manually opened, but not enough to open the valve from the closed position unaided. The thermocouple (17) is located at a position where it will be heated by a flame, which may be a pilotlightorthe main burner array. If the flame is extinguished the solenoid energization ceases, the valve closes and the gas supply cut off. Such flame-failure devices are well known and are readily commercially available for fitting into gas boilers, water heaters, fires or cookers. Normally with a burner bartheflames (12) sit close to the bar. If the oxygen supply is inadequate then the flames iift up from the bar, as shown at (20), the flames seeking more oxygen. An inadequate oxygen supply may be due to a number of different causes, including blockage or restriction of the exhaust pipe so that the through flow is restricted, failure or reduced output of the combustion fan (16), restriction of the inlet airopeningsforthe combustion fan, and vitiation (exhaustion) of the air in the room being supplied to the combustion fan.When a long ex- haust pipe (i.e. one metre or more) is used, the danger of restriction is increased, and it is accordingly more desirable than usual to provide safety means for cutting offthe gas when oxygen starvation is detected. Itisfound byobservationthatwhen aburner bar is subject two an increasingly inadequate air supply, the flames at the right hand end of the burner, shown at (20), lift off before those at the left hand end, as seen in the drawing, ie.e. the flames furthestfrom the injector (14) first show the effect of oxygen starvation. When a flame is burning with inadequate oxygen it produces poisonous carbon monoxide in its exhaust.If the exhaust pipe is not clearing the exhaust products properly, then there may be exhaust spillage into the room, which is unacceptable. As shown in the drawing, a flame lift-off detecting device comprises a flame sensing probe (22) located at the right hand end ofthe burner bar (i.e. at the end furthestfrom the injector) and at the base of aflame when it is burning correctly close to the bar. An electrical control device (23) operates when the flame is burning correctly close to the burner ports to maintain a switch device (24) closed. Switch (24) is connected in an electricalsupplyline (25) to motor (26) which drives the combustion fan (16). When flame (20) lifts, probe (22) senses electro nicallythattheflame is not present. The control device (23) then opens switch (24), thus cutting off the supply to motor (26) and stopping the fan (16). The air supply to all burners is thus stopped, all the flames lift and go out. Thermocouple (17) then senses that there is no flame, solenoid (18) falls out, gasvalve (19) closes andthe heating appliance is thus closed down. For starting purposes switch (24) may be held closed by push button (27) until the flame has es tablished itself. Push button (27) may be the same or ganged with push button (21). Thustheflame-failurevalve(19) is caused to operateto shut the appliance down on the occurrence offlame lift-off, so serving a dual purpose. In effect, when probe (22) senses any reduction in airflow, it operates to reduce the airflow still further to the point where the flame4ailure device operates. Because flame lift-off starts to occur at the opposite end of the burnerto that where the normal flame failure device thermocouple is situated the gas would not otherwise be shut off before the CO : CO2 ratio had exceeded the ratio permitted by the relevant British Standard. The flame lift-off device is of the known kind working on the flame rectification principle. When aflame is present a small current is produced which is amplified to operate a switch. CLAIMS

1. A gas-fired heating appliance incoprorating a flame-failure device which operates to shut down the appliance when a burner flame is extinguished,the appliance including a flame lift-off sensor located to sense lifting ofthe burnerflame and means four stopping a flow of combustion air when the sensor detects flame lift-off.

2. Aheating appliance as claimed in claim 1, wherein said flame lift-off sensor is located adjacent to the burner at or nearthe position atwhich flame lift-off starts.

3. A heating appliance as claimed in claim 2, wherein said burner is a burner bar having a gas injector at one end and the flame lift-off sensor atthe other end.

4. A heating appliance as claimed in any of claims 1 to 3, having a combustion air fan for supplying combustion air to the burner, said means for stopping the flow of combustion air operating to interruptthe operation of the combustion air fan.

5. A heating appliance as claimed in claim 4, wherein said stopping means comprises an electrical switch means operated by the flame lift-off sensorto interrupt an electrical power supply driving said combustion air fan.

6. Aheating appliance as claimed in claim 3 or any claim appendantthereto, wherein said flame failure device is located adjacent said one end ofthe burner bar.

7. A heating appliance as claimed in any of claims 1 to 6, wherein said flame failure device is a thermo-electric device.

8. A heating appliance as claimed in any of claims 1 to7,wherein said flame lift-off device oper- ates on the flame rectification principle.

9. A gas-fired heating appliance substantially as described hereinbefore with reference to the accompanying drawings.