EP0390326A2 - Gas heating unit and electrical control circuit therefor - Google Patents
Gas heating unit and electrical control circuit therefor Download PDFInfo
- Publication number
- EP0390326A2 EP0390326A2 EP90301869A EP90301869A EP0390326A2 EP 0390326 A2 EP0390326 A2 EP 0390326A2 EP 90301869 A EP90301869 A EP 90301869A EP 90301869 A EP90301869 A EP 90301869A EP 0390326 A2 EP0390326 A2 EP 0390326A2
- Authority
- EP
- European Patent Office
- Prior art keywords
- burner
- gas
- air
- accommodation unit
- combustion
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Withdrawn
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Classifications
-
- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F24—HEATING; RANGES; VENTILATING
- F24H—FLUID HEATERS, e.g. WATER OR AIR HEATERS, HAVING HEAT-GENERATING MEANS, e.g. HEAT PUMPS, IN GENERAL
- F24H9/00—Details
- F24H9/0005—Details for water heaters
- F24H9/001—Guiding means
- F24H9/0026—Guiding means in combustion gas channels
-
- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F24—HEATING; RANGES; VENTILATING
- F24H—FLUID HEATERS, e.g. WATER OR AIR HEATERS, HAVING HEAT-GENERATING MEANS, e.g. HEAT PUMPS, IN GENERAL
- F24H1/00—Water heaters, e.g. boilers, continuous-flow heaters or water-storage heaters
- F24H1/22—Water heaters other than continuous-flow or water-storage heaters, e.g. water heaters for central heating
- F24H1/34—Water heaters other than continuous-flow or water-storage heaters, e.g. water heaters for central heating with water chamber arranged adjacent to the combustion chamber or chambers, e.g. above or at side
-
- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F24—HEATING; RANGES; VENTILATING
- F24H—FLUID HEATERS, e.g. WATER OR AIR HEATERS, HAVING HEAT-GENERATING MEANS, e.g. HEAT PUMPS, IN GENERAL
- F24H3/00—Air heaters
- F24H3/006—Air heaters using fluid fuel
Definitions
- One invention relates to combustible gas heating systems, in which flue discharge takes place through the floor; it is especially useful in such heating systems for sealed accommodation units such as caravans.
- a related invention concerns an electrical control circuit for such a system.
- an object of the present invention is to provide an alternative combustible gas heating system suitable for caravan use which avoids this difficulty.
- a combustible gas heating system for an accommodation unit comprises a room sealed heating unit incorporating a combustion box which houses a gas burner and means for conveying combustible gas to the burner, an inlet duct for conveying air into the combustion box, and an outlet duct for conveying products of combustion and excess air from the combustion box for discharge through the floor of the accommodation unit, and a fan operative to produce a forced flow of air through the system from the inlet to the outlet duct.
- the fan may be located in either the inlet or outlet duct, as may be the more convenient.
- the inlet duct preferably also extends through the floor of the accommodation unit so that the system neither withdraws air from, nor discharges flue products into, the unit.
- the fan is electrically operated and is energised automatically when the burner is ignited.
- the heating unit may be a space heater or a water heater, and in some cases the terminal part of the outlet duct system may be common to two such heaters.
- each heater is associated with its own fan appropriately located so as to produce a forced flow of air through the duct system of the respective heater when the heater is in use.
- thermocouple for detecting whether the gas burner is alight
- a gas control valve arranged to admit gas to the burner only if a voltage level signal from the thermocouple is such as to indicate the burner is alight.
- the heater illustrated in Figures 1 and 2 comprises a combustion box/heat exchanger 4 mounted on a caravan floor 3, and accommodating a gas burner 10.
- All combustion air enters a swivelling elbow 1 at 2 and discharges into the combustion box/heat exchanger 4 via an air distribution grill 9, mixing with combustible gas from the gas burner 10 and being deflected by a baffle 15 having a central flue slot 14. Excess air with the gaseous combustion products passes through a flue opening 16 and then down through a flue discharge duct 7 to a vent 13 below the caravan floor 3. These gases are diluted by a by-pass air stream 8.
- the elbow 1 is positioned in use to avoid the caravan axle, which would lie just below the horizontal portion of the elbow 1.
- a heat shield 5 Around the heat exchanger 4 there is located a heat shield 5, the whole being surrounded by an outside casing 6 sealed to the floor by a plinth 17. The gas is controlled by a tap 11. The usual flame failure protection devices are fitted and ignition is by a stream spark generator (12v d.c.).
- the inlet duct constituted by the swivelling elbow 1, accommodates at its upper end an electric fan 12, which assists the expulsion of the combustion products from the combustion box by producing a forced flow of air through the box and to the atmosphere via the outlet duct 7, the fan being automatically energised when the burner is ignited by means of any convenient form of switch arrangement.
- an electric fan 12 which assists the expulsion of the combustion products from the combustion box by producing a forced flow of air through the box and to the atmosphere via the outlet duct 7, the fan being automatically energised when the burner is ignited by means of any convenient form of switch arrangement.
- the water heater illustrated in Figure 3 similarly comprises a combustion box/heat exchanger 4 mounted on the caravan floor as in the case of the previous embodiment, combustion air similarly entering the box through a swivelling elbow 1 having an inlet at 2.
- the air then passes through an air deflector grill 9 as well as through a by-pass exit 8 to dilute the flue gases.
- the air mixes with the combustion gases from the gas burner 10 through the heat exchanger 4 via a deflector flue collection hood 25 and then downwards through a flue duct 7 to exhaust through the caravan floor 3 at flue terminal 13.
- the heat exchanger is room sealed within an outer casing 6 fixed to the floor plinth 17.
- the gas burner 10 is controlled by a solenoid valve 11 in conjunction with a water flow inlet 18.
- the usual flame safety devices are employed, plus a high limit self re-setting thermostat and a safety cut-off thermostat. These are conveniently as shown in co-pending patent application No. 8803047 as g, k and l in Figure 1, except in this case the flame failure device is a flame rectification PCB and the pilot burner is eliminated in favour of a stream spark generator.
- the hot water flow is controlled by a pre-set micro-switched tap 19.
- An electric fan 12 is located within the flue duct 7 so as to draw air by suction through the combustion box heat exchanger 4 and to expel it through the outlet 13. In this case also the fan is energised automatically when the burner is ignited.
- the heaters may share a common outlet duct, and a fan may be located within this duct, although a separate fan may be located within the inlet duct to each of the two heaters, or within a respective outlet duct connecting the individual heaters to the common outlet duct.
- the space heater whose flue arrangement is shown in Figure 4 is otherwise similar to Figures 1 and 2.
- a fixed, generally rectangular section inlet flue box 41 which is flanged to fit into a larger gap in the caravan floor 3.
- the box 41 has a terminal 2 at the end of a cuboid downward projection 42 at one end of the box; the box 41 is fitted with the projection 42 at either end, so as to avoid the axle.
- the outlet flue 7 enters a similarly-flanged square box 43 having a terminal 13.
- control circuit supplies electric power from a source to the spark stream ignition and to the electric fan 12, and responds to a voltage level signal from a thermocouple adjacent the gas burner, and also to a fan proving switch S1 driven by air from the fan 12.
- the circuit ensures that the gas supply to the burner is interrupted if the air supply to the burner is restricted, whether due to electrical power failure or to flue blockage.
- An on/off switch S0 is manually operable, preferably by being associated with the spindle of the gas control tap. When closed, this supplies power to a relay K1 by way of the fan proving switch S1, which always returns to its Nc position in the absence of air flow from the fan. The relay then closes fan switch S2 to power the fan 12, and to latch on the relay, and moves switch S3 to its No position to cause a storage capacitor to charge through a diode D1.
- the air flow will activate the fan proving switch S1, moving it to its No position and thus powering a conventional gas ignition/flame detection system (not shown) via switch S2.
- the thermocouple heats up and generates sufficient e.m.f. (voltage) to hold open a gas valve located in the gas tap.
- thermocouple When the on/off switch 50 is opened, normally to switch off the appliance, the relay causes switches S2 and S3 to change state, turning off the fan 12 and discharging the capacitor through the thermocouple via a second diode D2.
- This current surge through the thermocouple causes the gas valve to close instantly, much more quickly than if it relied on the cooling of the thermocouple to cause its e.m.f. to drop below the threshold. This prevents any gas reaching the burner after the appliance has been switched off, or if there is an electrical power failure.
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- Engineering & Computer Science (AREA)
- Physics & Mathematics (AREA)
- Thermal Sciences (AREA)
- Chemical & Material Sciences (AREA)
- Combustion & Propulsion (AREA)
- Mechanical Engineering (AREA)
- General Engineering & Computer Science (AREA)
- Regulation And Control Of Combustion (AREA)
- Control Of Combustion (AREA)
Abstract
Description
- One invention relates to combustible gas heating systems, in which flue discharge takes place through the floor; it is especially useful in such heating systems for sealed accommodation units such as caravans. A related invention concerns an electrical control circuit for such a system.
- In conventional caravans space tends to be very limited, and the heating units have commonly been installed beneath or at the bottom of cupboards. However the presence of a flue pipe extending upwards within the cupboard from a combustion box housing the gas burner, in order to convey combustion products through the roof of the caravan, is inconvenient as it takes up valuable storage space within the cupboard.
- The use of a simple form of flue system arranged to direct the products of combustion through the floor of the caravan is already known. However, the heat input for these designs is restricted due to the problem of directing naturally rising hot products of combustion in the opposite direction and well below the gas burner level. Accordingly an object of the present invention is to provide an alternative combustible gas heating system suitable for caravan use which avoids this difficulty.
- According to the first invention, a combustible gas heating system for an accommodation unit comprises a room sealed heating unit incorporating a combustion box which houses a gas burner and means for conveying combustible gas to the burner, an inlet duct for conveying air into the combustion box, and an outlet duct for conveying products of combustion and excess air from the combustion box for discharge through the floor of the accommodation unit, and a fan operative to produce a forced flow of air through the system from the inlet to the outlet duct.
- The fan may be located in either the inlet or outlet duct, as may be the more convenient.
- The inlet duct preferably also extends through the floor of the accommodation unit so that the system neither withdraws air from, nor discharges flue products into, the unit. Conveniently the fan is electrically operated and is energised automatically when the burner is ignited.
- The heating unit may be a space heater or a water heater, and in some cases the terminal part of the outlet duct system may be common to two such heaters. Preferably each heater is associated with its own fan appropriately located so as to produce a forced flow of air through the duct system of the respective heater when the heater is in use.
- Conventional flame detection systems use a thermocouple for detecting whether the gas burner is alight, and a gas control valve arranged to admit gas to the burner only if a voltage level signal from the thermocouple is such as to indicate the burner is alight. Where such a system is used in a gas heater which relies for its operation on an electric fan associated with the flue, and/or on a spark stream electric ignition, it is important that the burner is shut off very soon after the electrical system is turned off or after it fails in a power cut. The problem is that there is an inherent delay while the thermocouple cools sufficiently to cause its output voltage level to cross the threshold recognised by the gas control valve. Accordingly, the purpose of the second invention is to find a simple way of overcoming this problem.
- According to the second invention, an electrical control circuit for a combustible gas heating system having a gas supply control valve for admitting the gas to a burner, an electrical ignition system for the burner, and a flame detection sensor for sending an electrical signal to the control valve to admit gas only when the burner is alight, comprises a switch for supplying power from a source to the ignition system, a storage capacitor arranged to charge from the power source through the switch, and means responsive to an interruption of power from the switch to connect the capacitor to the flame detection sensor to cause immediate cancellation of the electrical control signal whereby to cause the control valve to close.
- Three combustible gas heating systems for a caravan, embodying the first invention, and a control system embodying the second invention, will now be described by way of example with reference to the accompanying drawings, in which
- Figures 1 and 2 represent diagrammatically a sectional front view and a sectional side view of a space heater;
- Figure 3 represents a sectional front view of a water heater;
- Figure 4 is a sectional front view of the flue system of a space heater otherwise similar to Figure 1; and
- Figure 5 is a circuit diagram of part of an electrical control circuit for the heating system of the heaters of Figures 1 or 4.
- The heater illustrated in Figures 1 and 2 comprises a combustion box/
heat exchanger 4 mounted on acaravan floor 3, and accommodating agas burner 10. - All combustion air enters a swivelling elbow 1 at 2 and discharges into the combustion box/
heat exchanger 4 via anair distribution grill 9, mixing with combustible gas from thegas burner 10 and being deflected by abaffle 15 having acentral flue slot 14. Excess air with the gaseous combustion products passes through a flue opening 16 and then down through aflue discharge duct 7 to avent 13 below thecaravan floor 3. These gases are diluted by a by-pass air stream 8. - The elbow 1 is positioned in use to avoid the caravan axle, which would lie just below the horizontal portion of the elbow 1.
- Around the
heat exchanger 4 there is located aheat shield 5, the whole being surrounded by anoutside casing 6 sealed to the floor by aplinth 17. The gas is controlled by atap 11. The usual flame failure protection devices are fitted and ignition is by a stream spark generator (12v d.c.). - The inlet duct, constituted by the swivelling elbow 1, accommodates at its upper end an
electric fan 12, which assists the expulsion of the combustion products from the combustion box by producing a forced flow of air through the box and to the atmosphere via theoutlet duct 7, the fan being automatically energised when the burner is ignited by means of any convenient form of switch arrangement. One such arrangement is described below with reference to Figure 5. - The water heater illustrated in Figure 3 similarly comprises a combustion box/
heat exchanger 4 mounted on the caravan floor as in the case of the previous embodiment, combustion air similarly entering the box through a swivelling elbow 1 having an inlet at 2. The air then passes through anair deflector grill 9 as well as through a by-pass exit 8 to dilute the flue gases. The air mixes with the combustion gases from thegas burner 10 through theheat exchanger 4 via a deflector flue collection hood 25 and then downwards through aflue duct 7 to exhaust through thecaravan floor 3 atflue terminal 13. - The heat exchanger is room sealed within an
outer casing 6 fixed to thefloor plinth 17. - The
gas burner 10 is controlled by asolenoid valve 11 in conjunction with a water flow inlet 18. The usual flame safety devices are employed, plus a high limit self re-setting thermostat and a safety cut-off thermostat. These are conveniently as shown in co-pending patent application No. 8803047 as g, k and l in Figure 1, except in this case the flame failure device is a flame rectification PCB and the pilot burner is eliminated in favour of a stream spark generator. The hot water flow is controlled by apre-set micro-switched tap 19. - An
electric fan 12 is located within theflue duct 7 so as to draw air by suction through the combustionbox heat exchanger 4 and to expel it through theoutlet 13. In this case also the fan is energised automatically when the burner is ignited. - In each embodiment the forced flow of air through the system ensures that the presence of pockets of stagnant combustion products within the combustion box is effectively avoided.
- Where both a space heater and a water heater are located in close proximity to one another the heaters may share a common outlet duct, and a fan may be located within this duct, although a separate fan may be located within the inlet duct to each of the two heaters, or within a respective outlet duct connecting the individual heaters to the common outlet duct.
- The space heater whose flue arrangement is shown in Figure 4 is otherwise similar to Figures 1 and 2. In place of the swivelling elbow 1 is a fixed, generally rectangular section
inlet flue box 41 which is flanged to fit into a larger gap in thecaravan floor 3. Thebox 41 has aterminal 2 at the end of a cuboid downward projection 42 at one end of the box; thebox 41 is fitted with the projection 42 at either end, so as to avoid the axle. Theoutlet flue 7 enters a similarly-flangedsquare box 43 having aterminal 13. There is a three-pass baffling system within the combustion box/heat exchanger 4, and, as before, a by-pass flow ofair 8 dilutes and cools the outwardly-flowinggases 7. - With reference to Figure 5, the control circuit supplies electric power from a source to the spark stream ignition and to the
electric fan 12, and responds to a voltage level signal from a thermocouple adjacent the gas burner, and also to a fan proving switch S1 driven by air from thefan 12. The circuit ensures that the gas supply to the burner is interrupted if the air supply to the burner is restricted, whether due to electrical power failure or to flue blockage. - An on/off switch S0 is manually operable, preferably by being associated with the spindle of the gas control tap. When closed, this supplies power to a relay K1 by way of the fan proving switch S1, which always returns to its Nc position in the absence of air flow from the fan. The relay then closes fan switch S2 to power the
fan 12, and to latch on the relay, and moves switch S3 to its No position to cause a storage capacitor to charge through a diode D1. - Provided the fan functions and the flue is not blocked, the air flow will activate the fan proving switch S1, moving it to its No position and thus powering a conventional gas ignition/flame detection system (not shown) via switch S2. Once the burner is alight, the thermocouple heats up and generates sufficient e.m.f. (voltage) to hold open a gas valve located in the gas tap.
- When the on/off switch 50 is opened, normally to switch off the appliance, the relay causes switches S2 and S3 to change state, turning off the
fan 12 and discharging the capacitor through the thermocouple via a second diode D2. This current surge through the thermocouple causes the gas valve to close instantly, much more quickly than if it relied on the cooling of the thermocouple to cause its e.m.f. to drop below the threshold. This prevents any gas reaching the burner after the appliance has been switched off, or if there is an electrical power failure.
Claims (7)
Applications Claiming Priority (4)
Application Number | Priority Date | Filing Date | Title |
---|---|---|---|
GB8904013 | 1989-02-22 | ||
GB898904013A GB8904013D0 (en) | 1989-02-22 | 1989-02-22 | Flue systems |
GB8918916 | 1989-08-18 | ||
GB8918916A GB2232239B (en) | 1989-02-22 | 1989-08-18 | Gas heating unit of accommodation unit and electrical control circuit therefor |
Publications (2)
Publication Number | Publication Date |
---|---|
EP0390326A2 true EP0390326A2 (en) | 1990-10-03 |
EP0390326A3 EP0390326A3 (en) | 1990-12-05 |
Family
ID=26294994
Family Applications (1)
Application Number | Title | Priority Date | Filing Date |
---|---|---|---|
EP19900301869 Withdrawn EP0390326A3 (en) | 1989-02-22 | 1990-02-21 | Gas heating unit and electrical control circuit therefor |
Country Status (3)
Country | Link |
---|---|
EP (1) | EP0390326A3 (en) |
AU (1) | AU4990790A (en) |
CA (1) | CA2009379A1 (en) |
Cited By (1)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
CN110848971A (en) * | 2019-12-09 | 2020-02-28 | 湖南省农友农业装备股份有限公司 | Hot-blast stove |
Families Citing this family (3)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
US7826727B2 (en) | 2006-05-05 | 2010-11-02 | Twin-Star International, Inc. | Electric fireplace |
USD616977S1 (en) | 2008-12-03 | 2010-06-01 | Twin-Star International Inc. | Fireplace insert |
USD668748S1 (en) | 2009-07-07 | 2012-10-09 | Twin-Star International, Inc. | Electric fireplace |
Citations (6)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
DE2028382A1 (en) * | 1969-06-09 | 1971-04-08 | Gaz De France, Paris | Gas-heated device for generating a hot flow medium |
US3720858A (en) * | 1971-07-20 | 1973-03-13 | Columbia Gas Syst Service Corp | Relay timing system |
GB1338912A (en) * | 1970-08-18 | 1973-11-28 | Morley Co Ltd T B | Space heaters |
GB2165939A (en) * | 1984-10-23 | 1986-04-23 | Willey Robinson Ltd | Gas-fired heating appliance |
EP0191644A2 (en) * | 1985-02-14 | 1986-08-20 | A.O. Smith Corporation | Submersible chamber water heater |
JPS62293016A (en) * | 1986-06-11 | 1987-12-19 | Matsushita Electric Ind Co Ltd | Gas appliance with time limit device |
-
1990
- 1990-02-06 CA CA 2009379 patent/CA2009379A1/en not_active Abandoned
- 1990-02-19 AU AU49907/90A patent/AU4990790A/en not_active Abandoned
- 1990-02-21 EP EP19900301869 patent/EP0390326A3/en not_active Withdrawn
Patent Citations (6)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
DE2028382A1 (en) * | 1969-06-09 | 1971-04-08 | Gaz De France, Paris | Gas-heated device for generating a hot flow medium |
GB1338912A (en) * | 1970-08-18 | 1973-11-28 | Morley Co Ltd T B | Space heaters |
US3720858A (en) * | 1971-07-20 | 1973-03-13 | Columbia Gas Syst Service Corp | Relay timing system |
GB2165939A (en) * | 1984-10-23 | 1986-04-23 | Willey Robinson Ltd | Gas-fired heating appliance |
EP0191644A2 (en) * | 1985-02-14 | 1986-08-20 | A.O. Smith Corporation | Submersible chamber water heater |
JPS62293016A (en) * | 1986-06-11 | 1987-12-19 | Matsushita Electric Ind Co Ltd | Gas appliance with time limit device |
Non-Patent Citations (1)
Title |
---|
PATENT ABSTRACTS OF JAPAN, vol. 12, no. 183 (M-703)[3030], 28th May 1988; & JP,A,62 293 016 (MATSUSHITA ELECTRIC IND. CO., LTD) 19-12-1987 * |
Cited By (1)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
CN110848971A (en) * | 2019-12-09 | 2020-02-28 | 湖南省农友农业装备股份有限公司 | Hot-blast stove |
Also Published As
Publication number | Publication date |
---|---|
EP0390326A3 (en) | 1990-12-05 |
AU4990790A (en) | 1990-08-30 |
CA2009379A1 (en) | 1990-08-22 |
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