WO2019224128A1

WO2019224128A1 - Heating apparatus comprising combustible gas burner

Info

Publication number: WO2019224128A1
Application number: PCT/EP2019/062869
Authority: WO
Inventors: Michele Benvenuto; Michele Ciscato
Original assignee: Sit S.P.A.
Priority date: 2018-05-21
Filing date: 2019-05-17
Publication date: 2019-11-28
Also published as: US20210199289A1; CA3100129A1; MX2020012434A; IT201800005549A1; AR115407A1

Abstract

A combustible gas heating apparatus is described, in particular an apparatus for heating water, comprising: - a main burner (2) arranged in a combustion chamber (3) of the apparatus, - a pilot burner (4) suitable for generating a pilot flame for igniting the main burner (2), - a valve group (5) comprising a main valve (6) arranged on a main duct (7) for supplying the combustible gas to the main burner, and a pilot valve (8) arranged on said main duct (7), upstream of the main valve, for supplying gas to the pilot burner (4), a pilot duct (9) branching off from a portion (7a) of the main duct (7) between the pilot and main valves in order to feed the gas to the pilot burner, - a system for controlling the supply of gas to the main and pilot burners, including an electronic control unit (10) that is operatively associated with the main and pilot valves, - a thermal safety device (12) which can be activated in the presence of inflammable vapours in the vicinity of the apparatus and is designed to safely extinguish the main burner (2) when a predetermined temperature threshold in the combustion chamber (3) has been exceeded, - the pilot burner (4) being intended as a continuous pilot burner having a permanent flame, - the pilot valve (8) and the main valve (6) being electrically-operated valves, - an auxiliary buffer battery (18) being intended to power the electronic control unit if there is a temporary absence of a mains power supply, such that at least the pilot valve (8) is powered and operated, by means of said control unit (10), in order to ensure that the pilot flame in the pilot burner (4) is maintained during the temporary absence of a mains power supply.

Description

Heating apparatus comprising combustible gas burner

Technical field

The present invention relates to a heating apparatus comprising a combustible gas burner.

Technological background

The invention is applicable in particular, although not exclusively, to the technical field of water heating apparatuses, that is sanitary water heaters or heaters for water circulating in plants for heating environments.

More specifically, combustible gas apparatuses in which the invention is used typically comprise a pilot burner for generating a pilot flame, and a main burner for generating a main flame, in which combustion is initiated in the main burner by means of the pilot flame.

A first type of apparatuses of this kind provides the use of a continuous pilot burner, that is having a permanent flame, in which the pilot flame remains ignited from the moment the apparatus is switched on, provided it is not switched off.

Apparatuses of this type are generally not connected to the mains. In these apparatuses, a magnetic safety group is associated with the pilot valve that comprises a thermocouple (or thermopile) and as a system connected thereto having a manual cocking feature, and at least one main valve having a mechanical or electrical operator (preferably powered by the energy produced by the thermopile) for directly or indirectly (servo-assisted system) commanding a gas circuit to a main burner. A thermostat that compares the temperature of the water set by the user with the actual temperature detected by the sensor manages the ignition of the main burner on the basis of the amount of heat required.

In compliance with specific applicable regulations, thermal safety devices also need to be used in these apparatuses, which devices are designed to intervene when inflammable vapours are present in the vicinity of the heating apparatus. In this type of apparatuses, the thermal safety devices, also known in the field by the abbreviation TCO ("Thermal Cut Off"), are designed as mechanical devices. These are similar to thermal interrupters, which are suitable for monitoring the temperature inside the combustion chamber. The ignition of inflammable vapours inside the combustion chamber causes the temperature in said chamber to rise, thereby causing the TCO device to intervene when a predetermined threshold temperature is exceeded. The TCO device can be a "single-use" TCO (for example by using a thermally fusible element) or a resettable TCO.

In continuous pilot heating apparatuses, the known types of such TCO safety devices can work in series with the flow of air that enables the combustion such that, by intercepting said flow of air by means of appropriate interception components that are activated by the TCO device, the main burner and the pilot burner are in fact extinguished. Alternatively, these devices can work in series with the thermocouple, thereby causing the pilot flame and consequently also the main burner to be extinguished (intercepting the passage of gas).

Continuous pilot heating apparatuses equipped with the TCO safety devices mentioned above are advantageous in that these TCO devices are robust and inexpensive. Furthermore, if a small amount of inflammable vapours is present, said vapours are burnt by said pilot flame, which is always ignited even during the standby periods of the apparatus, thereby reducing the risk of explosion. In contrast, that is with a larger amount of vapours, the TCO safety devices intervene.

Such apparatuses are not affected by the drawbacks connected with the mains either, since they are not connected thereto and the fact that the pilot flame is always ignited guarantees ease of ignition.

In contrast, this type of continuous pilot apparatuses are marked by manual ignition of the pilot burner which is impractical and not easy for the user to use (requiring the user to press the button on the cocking group for a certain amount of time, simultaneously actuating the igniter, and then to release the button as soon as the thermocouple activated by the flame has energised the magnetic group of the pilot valve).

Another limitation of such apparatuses is connected to the fact that, during the periods of rest (standby) of the main burner, the pilot flame dissipates all the energy it produces. The thermoelectric generator (thermocouple/thermopile) is likewise subjected to ageing and loss of performance, thereby generating less current over time than what is needed to activate the magnetic group.

A second type of such heating apparatuses provides the use of an intermittent pilot burner, that is in which the pilot flame is only ignited after heat has been requested, this causing the ignition of the main burner. These apparatuses typically need to be connected to the mains and are provided with a circuit board that forms the electronic control unit of the pilot valve and of the main valve, said valves therefore both being designed as electrically operated valves (electric valves).

The intermittent pilot burner is provided with an igniter electrode and a sensor for electronically controlling the flame (for example a flame ionisation sensor) as well as a thermostat for igniting and extinguishing the pilot burner and the main burner.

In order to fulfil the function of protection against the ignition of inflammable vapours, electronic sensors, also known in the field by the abbreviation "FVI" (Flammable Vapor Sensor) are normally used in this second type of apparatuses. These electronic sensors are positioned outside the combustion chamber and are provided with an electrical resistance that is dependent on the concentration of inflammable vapours. The circuit board is designed to monitor the value of the resistance of the sensor in order to prevent the apparatus from switching on if a high concentration of inflammable vapours is detected.

This type of apparatus has the advantage of providing automatic ignition and is also more energy efficient since the pilot only remains ignited for the time required to ignite the main burner and until the main burner has been ignited, but, if the main burner is extinguished (standby), the pilot burner is also extinguished. It is also advantageous on account of having automatic reignition if the pilot flame is accidentally extinguished (for example in the event of a gust of wind, a temporary absence of gas, etc.).

In contrast, since these apparatuses require a mains power supply, they cannot function in the event of a blackout (thereby not guaranteeing that the user has hot water for the entire duration of the black-out). Furthermore, the FVI electronic sensors are expensive and not very robust insofar as they suffer from the so-called phenomenon of "nuisance shut off" or "false positives", meaning they also intervene in the absence of inflammable vapours because they are sensitive to contaminants. Another limitation is that the inflammable vapours are not burnt by the pilot flame, which in fact only remains ignited for the time required to ignite the main burner, and is then extinguished.

There may also be external conditions (for example low temperatures, contaminants and moisture on the ignition electrode or the detection of a flame, etc) that make ignition difficult.

Description of the invention

One main principle that forms the basis of the present invention is that of providing a heating apparatus, which comprises a combustible gas burner and the structure and function of which are designed to overcome the limitations indicated above with reference to the known solutions.

These and other objects that will clearly appear in the following are achieved by the invention by means of a heating apparatus comprising a combustible gas burner, which is formed in accordance with the attached claims.

Brief description of the drawings

Additional features and advantages of the invention will become clearer from the following detailed description of a preferred embodiment thereof, which is illustrated by way of non-limiting example, with reference to the only attached figure, which is a schematic view of the main parts of a heating apparatus formed in accordance with the invention.

Preferred embodiments of the invention

With reference to the cited figure, 1 denotes an example of a heating apparatus as a whole, comprising a gas burner, which is only depicted schematically and is formed in accordance with the present invention.

Said apparatus can be designed as a sanitary water heater or a heater for water intended to be circulated in a plant for heating environments.

The apparatus 1 comprises a main burner 2 arranged in a combustion chamber 3, on which burner a main flame is generated, a pilot burner 4, which is suitable for generating a pilot flame in order to ignite the main burner 2, and a valve group 5.

The valve group 5 comprises a main valve 6, which is arranged on a main duct 7 of the valve group, for supplying the combustible gas to the main burner 2, and a pilot valve 8, which is arranged on the duct 7 upstream of the main valve, for supplying the gas to the pilot burner. 9 denotes a pilot duct, which branches off from a portion 7a of the main duct 7 that is situated between the pilot valve 8 and the main valve 6 and is suitable for feeding the gas to the pilot burner 4.

The main valve 6 and the pilot valve 8 are suitably formed as electrically operated valves, that is electric valves provided with respective actuators that are active on the corresponding shutters of the valves, which actuators are energised by supply signals that are carried through respective electrical supply circuits 6a, 8a. In the figure, circuits 6a, 8a and other electrical connection paths to and from the circuit board are depicted by a dot-dashed line.

The supply signals originate from an electronic control unit 10, which is formed as a circuit board and is operatively associated with said valves in order to enable the passage of gas through the corresponding valve seats. Said control unit is part of a control system of the apparatus, which is designed to control the supply of gas to the pilot and main burners.

The control unit 10 is supplied with power by means of a connection to the mains, marked as 11, which is suitable for supplying an alternating voltage having a preset frequency, for example.

12 denotes a thermal safety device as a whole, which can be activated when inflammable vapours are present in the vicinity of the apparatus, said device being designed to activate the safe switch-off of the main burner 2 and the pilot burner 4 when a predetermined threshold temperature is exceeded in the combustion chamber.

In one embodiment, the thermal safety device 12 comprises an interception component 13 that is intended for selectively intercepting the flow of air entering the combustion chamber 3 and is suitable for igniting the flame of the main burner. The interception component 13 acts on an opening 13a, through which the flow of air enters the combustion chamber, and can be activated, for example, by the fusion of a fusible element (not shown) that acts as means for stopping the operating stroke of the interception component, said component being subjected to resilient preload, for example.

If the threshold temperature mentioned above is exceeded, the stop means fuses, thereby enabling the closing stroke of the interception component.

13b denotes a duct for evacuating fumes from the combustion chamber, which, in order for efficient heat exchange, is designed to extend inside a tank 13c for water intended to be heated by means of the heating apparatus.

13d marks a temperature sensor (arranged in the tank for detecting the temperature of the water) of an electronic water thermostat, which sensor is operatively associated with the control unit 10 and is designed to compare the temperature of the water set by the user with the actual temperature detected by the sensor. In one embodiment, the thermal safety device 12 can comprise a mechanical thermostat, marked as 14 in the figure, which is arranged in a suitable position in the combustion chamber and is operatively connected to the control unit 10. The thermostat 14 can change state if the temperature in the combustion chamber exceeds the preset threshold temperature, and the control unit is designed to identify that the thermostat 14 has changed state, intervening with a command to safely extinguish the main burner as a result. For ease of representation, both the embodiments of the thermal safety device 12, that is comprising the interception component 13 and the thermostat 14, respectively, are shown in the diagram in the attached figure, these, however, being considered to be alternative solutions to one another, and are therefore individually applied to the apparatus in alternative ways.

The apparatus 1 likewise comprises a device for damping down flames, denoted by 15 and represented only schematically in the figure, which is intended for blocking the propagation of the flame outside the apparatus. In one embodiment, the device 15 comprises a fireproof grid comprising holes that runs around the outside of the combustion chamber. The mesh arrangement of said grid is intended to prevent flames from escaping into the environment when inflammable vapours that are burnt by the flames of the burners of the apparatus are present.

16 marks a flame-detection electrode, which is arranged near to the pilot flame and is operatively connected to the control unit 10.

17 marks a discharge electrode/flame ignition electrode, which is also arranged near to the pilot burner and is operatively connected to the control unit. In one embodiment, the functionalities of the electrodes 16 and 17 can be integrated in a single electrode.

In accordance with one aspect of the invention, the pilot burner 4 is suitably designed as a continuous pilot burner, that is having a permanent flame, and, in a preferred embodiment, the pilot valve 8 is designed to be supplied with power by means of the control unit 10, from an auxiliary buffer battery 18, which can order the corresponding actuator of the pilot valve to open said pilot valve so as to ensure that the flame of the pilot burner is maintained in the event of a mains blackout, that is in the temporary absence of a power supply from the mains to the pilot valve.

In other words, the buffer battery 18 is intended for supplying power to the control unit 10 in the temporary absence of a mains power supply, such that the control unit in turn orders the pilot valve to open/close during the temporary absence of a mains power supply.

In one embodiment of the invention, the buffer battery 18 is designed to also supply power to the main valve 6, in addition to the pilot valve, by means of the control unit so as to ensure the functionality of the apparatus during a temporary absence of a mains power supply.

With particular reference to the electronic unit 10 for controlling the apparatus, said unit is operatively associated with an ON button, denoted by 19, by means of which the unit is activated, thereby initiating the procedure of igniting the pilot burner, and an OFF button, denoted by 20, by means of which the user can interrupt the supply of power to the control unit 10, consequently commanding the pilot and main valves to close. 21 marks a dial for regulating the temperature, which is only depicted schematically and by means of which the user can select the desired temperature. The dial for regulating the temperature can alternatively function by means of two or more buttons for selecting the temperature and by a series of LEDs or by an LCD screen.

During operation, the ignition procedure is therefore easy for the user to activate. In fact, starting from a non-operative state of the apparatus, by pressing the ON button, the user activates the circuit board of the control unit and initiates the ignition process.

Said process provides that the pilot valve 8 (which enables the passage of gas through the pilot burner 4) is opened and provides ignition discharge by means of the igniter electrode 17. Once the pilot flame has been ignited, the control unit 10 is notified that the pilot flame has been ignited by means of the flame sensor 16 (electrode for detecting the flame, which operates by detecting the ionisation current for example).

The pilot burner 4 can be ignited following a prolonged OFF period (the user completely turns off the application by means of the OFF button), or following the loss of the pilot flame during operation (for example the loss of the flame caused by gusts of wind, by a temporary absence of gas, by a blackout, or following the intervention of the thermal safety device).

In the event of prolonged OFF periods, the user needs to be present in order to switch on the control board 10 by means of the ON button. It is essential for the user to be present, since otherwise, after long periods of inactivity in which the application is switched off, inflammable vapours may have accumulated that the thermal safety device 12 would not be able to detect. The user therefore oversees whether or not inflammable vapours are present. The circuit board of the control unit 10 keeps the pilot flame ignited even when no heat is requested (this being the continuous pilot burner).

This characteristic allows for the thermal safety device 12 to function correctly, which, as a mechanical thermal safety device, only functions if at least the pilot burner 4 remains ignited (so as to burn the inflammable vapours that may have accumulated and by the thermal safety device 12 intervening if the predetermined threshold temperature is exceeded).

In the event that the mains lacks electric current, for example as a result of a temporary blackout, advantage is taken of the buffer battery 18 that maintains the supply of power to the pilot valve (and possibly the main valve) by means of the circuit board. In the absence of a buffer battery, the circuit board of the control unit would be deenergised and therefore the valves 6 and 8 would close and the pilot and main flames would be extinguished; in the event of an accumulation of inflammable vapours during the period in which there is no electric current, the function of the thermal safety device 12 would not be performed because this device cannot operate when the pilot burner is extinguished. As a result, the subsequent ignition in order to restore the electric current in the mains would result in dangerous situations.

Furthermore, without the provision of the buffer battery 18, the user would have to switch the apparatus back on by hand in the event of a power failure.

The situation in which the pilot flame is extinguished as a result of brief periods of no gas, due to gusts of wind or similar events, are managed by the circuit board as normal re-ignitions when there is mains voltage.

In the case of repeated failed ignitions, said board is moved into a "lockout" state. In these situations, although the function of safe turning off in the presence of inflammable vapours is not activated because there is not a flame, no dangerous conditions arise since the spark of the igniter can ignite the inflammable vapours that may be present, and also a reduced amount of time between the first failed ignition attempt and "lockout" state is selected, for example less than a few minutes, preferably less than three minutes. It should be noted that reignition following a "lockout" state requires the presence of the user (ON button).

It should be noted that the pilot flame in the apparatus according to the invention is not used to heat any thermoelectric generators and has the sole function of igniting the main burner. Therefore, the pilot burner can be designed to generate a smaller amount of energy. Therefore, less energy will be dissipated during the rest ("standby") periods where the pilot burner remains ignited anyway.

If a thermal safety device 12 intervenes (arranged in series with the flow of air that enters the combustion chamber), the circuit board of the control unit does not "directly" notice a possible intervention by the device 12. Therefore, the system is moved to a "lockout" state since it is no longer able to switch on. Instead, in the event that a thermal safety device comprising a mechanical thermostat 14 intervenes, the circuit board of the control unit is intended for receiving the signal relating to the state of the thermostat and can respond depending on the logic implemented (for example activating the switch-off of both burners).

The invention therefore meets the predefined objects, thus achieving the advantages mentioned above with respect to the known solutions.

The advantages achieved by means of the apparatus formed according to the invention include the fact that the use of a continuous pilot burner ensures that inflammable vapours that may be present near the apparatus are burnt by the pilot flame during the standby periods, thus reducing the risk of explosion and also allowing for the use of thermal safety devices that are inexpensive and have an adequate degree of robustness and reliability. Due to the provision of a buffer battery that is operatively connected at least to the control unit (and the pilot and main valves are also commanded to open/close by means of the control unit as a result), the apparatus is not affected by the problems associated with temporary blackouts of the mains, thereby preventing the user from being left without hot water during the temporary absence of a supply of power from the mains and having to switch the apparatus back on by hand.

Furthermore, the provision of electrically operated main and pilot valves makes the ignition process more "user friendly" for the user, and also allows for automatic reignition if the pilot burner has been accidentally extinguished. Furthermore, the combination of the features mentioned above in the apparatus according to the invention means that a thermoelectric generator (thermocouple/thermopile), which is known to be subjected to ageing and loss of performance, does not need to be used.

Claims

1. Combustible gas heating apparatus, in particular an apparatus for heating water, comprising :

a main burner (2) arranged in a combustion chamber (3) of the apparatus,

a pilot burner (4) suitable for generating a pilot flame for igniting the main burner (2),

a valve group (5) comprising a main valve (6) arranged on a main duct (7) for supplying the combustible gas to the main burner (2), and a pilot valve (8) arranged on said main duct (7), upstream of said main valve (6), for supplying gas to the pilot burner (4), a pilot duct (9) branching off from a portion (7a) of the main duct (7) between said pilot and main valves (8, 6) in order to feed the gas to the pilot burner (4),

a system for controlling the supply of gas to said burners, including an electronic control unit (10) that is operatively associated with said main and pilot valves (6, 8),

a thermal safety device (12) which can be activated in the presence of inflammable vapours in the vicinity of the apparatus and is designed to safely extinguish the main burner (2) when a predetermined temperature threshold in the combustion chamber (3) has been exceeded,

said pilot burner (4) being intended as a continuous pilot burner having a permanent flame,

the pilot valve (8) and the main valve (6) being electrically-operated valves,

- an auxiliary buffer battery (18) being intended to power said electronic control unit (10) if there is a temporary absence of a mains power supply, such that at least said pilot valve (8) is powered and operated, by means of said control unit (10), in order to ensure that the pilot flame in the pilot burner (4) is maintained during the absence of a mains power supply.

2. Heating apparatus according to claim 1, wherein said control unit (10) is designed to supply power to, and also operate, the main valve (6) during a temporary absence of a mains power supply, after the control unit (10) has been supplied with power by said auxiliary buffer battery (18).

3. Heating apparatus according to either claim 1 or claim 2, wherein said thermal safety device (12) comprises an interception element (13) designed to selectively intercept the flow of air that is suitable for igniting the flame in the main burner (2) if the temperature detected in the combustion chamber (3) exceeds the predetermined temperature threshold, thus safely extinguishing the main burner (2).

4. Heating apparatus according to claim 1, wherein said thermal safety device (12) comprises a mechanical thermostat (14) that can change state if the temperature in the combustion chamber (3) exceeds the predetermined temperature threshold, said control unit (10) being designed to recognise when said mechanical thermostat (14) has changed state in order to intervene in the form of a command to safely extinguish the main burner (2).

5. Heating apparatus according to one or more of the preceding claims, wherein said control unit (10) is supplied with power from the mains supply and is designed to send electric command signals to the pilot and main valves (8, 6) in order to open/close the passage of gas through said valves.

6. Heating apparatus according to one or more of the preceding claims, wherein said control unit (10) is operatively associated with a first ON button (10), by means of which said unit (10) is activated, determining the start of the procedure for igniting the pilot burner (4), an OFF button (20), by means of which the user can interrupt the power supply to the control unit (10) and subsequently command the pilot and main valves to close, and a dial (21) for regulating the temperature, by means of which the user can set the desired temperature and subsequently ignite the main burner (2) or not.

7. Heating apparatus according to one or more of the preceding claims, comprising a device (15) for damping down the flame, which comprises a fireproof grid.

8. Heating apparatus according to one or more of the preceding claims, comprising a water tank (13c) intended to be heated by said apparatus, and a water temperature sensor (13d) in an electronic water thermostat, which is designed to compare the water temperature set by the user with the actual temperature detected by the sensor (13d).