Combustion apparatus and hot water apparatus provided with same

Abstract

This combustion apparatus C comprises: a non-electroconductive flame hole plate 4 having a flame hole distribution area 40A in which a plurality of flame holes 40 that are through-holes are provided in a distributed arrangement; a chamber 30 that is adjacent to the reverse-surface side of the flame hole plate 4, the chamber 30 guiding, to the flame hole plate 4, a gas mixture of air and a fuel gas that is hydrogen or a hydrogen-containing gas; a combustion area CA on the obverse-surface side of the flame hole plate 4; and a grounding electroconductive part 5 that is set to a ground potential, the grounding electroconductive part 5 overlapping and contacting the reverse surface of the flame hole distribution area 40A in the flame hole plate 4. This suitably prevents or suppresses invalid ignition of the fuel gas caused by electrostatic discharge in the flame hole plate 4.

Description

Technical Field

[0001] The present disclosure relates to a combustion device of a type equipped with a flame hole plate, and a water heater such as a hot water supply apparatus including the same.Related Art

[0002] As a combustion device, there is one of an all-primary air combustion type in which fuel gas is combusted using a flame hole plate provided with multiple flame holes. In such a combustion device, a mixed gas of fuel gas and air is supplied toward the flame hole plate from a chamber (mixing room) on a back surface side of the flame hole plate. The mixed gas passes through each flame hole, reaches an area (combustion area) on a front surface side of the flame hole plate, and combusts in this combustion area.

[0003] In the aforementioned combustion device, to achieve stable combustion of the fuel gas, it is important to manage a flow velocity of the mixed gas passing through each flame hole. For that purpose, it is important to manage dimensions of each flame hole. Accordingly, conventionally, there are flame hole plates made of ceramic (see Patent Documents 1 to 3). If the flame hole plate is made of ceramic, the dimensions of each flame hole are relatively easy to manage, and excellent heat resistance is achieved.

[0004] However, in the conventional technology, there are problems to be solved as follows.

[0005] In recent years, from the perspective of protecting the natural environment, policies to realize a low-carbon society are being promoted. As an example of such policies, in the technical field of combustion devices, using hydrogen as fuel gas is being considered. Compared to city gas (main component: methane (CH 4 )) and LP gas (main component: propane ((C 3 H 8 )) which are often used as fuel gas, hydrogen requires less energy for ignition and is likely to ignite.

[0006] On the other hand, if the flame hole plate is made of ceramic and is non-conductive (has low electrical conductivity), the flame hole plate is likely to be charged with static electricity. Hence, there is a risk that hydrogen may ignite in a place not originally intended for combustion due to electrostatic discharge occurring on the flame hole plate. When such ignition occurs on the back surface side of the flame hole plate, that is, inside the chamber on an upstream side in a flow direction of the mixed gas, there is a risk of causing device damage to the combustion device. Accordingly, it is desirable to appropriately avoid such occurrences.Prior Art DocumentsPatent Documents

[0007] Patent Document 1: Japanese Patent No. 2689190 Patent Document 2: Japanese Patent Laid-Open No. H1-178447 Patent Document 3: Japanese Patent No. 4034749 SUMMARY OF INVENTIONProblem to be Solved by the Invention

[0008] An object of the present disclosure is to provide a combustion device and a water heater including the same, in which, under the conditions that hydrogen or a hydrogen-containing gas is used as fuel gas, the occurrence of undue ignition of fuel gas due to electrostatic discharge from a flame hole plate can be appropriately prevented.Means for Solving the Problem

[0009] To solve the above-mentioned problems, the present disclosure employs the following technical means.

[0010] A combustion device provided according to a first aspect of the present disclosure is characterized by including: a flame hole plate which is non-conductive, including a flame hole distribution area where multiple flame holes of a through hole shape are provided in a dispersedly arranged state; a chamber, provided adjacent to a back surface side of the flame hole plate, and guiding a mixed gas of fuel gas as hydrogen or a hydrogen-containing gas and air to the flame hole plate; a combustion area, provided on a front surface side of the flame hole plate, and where the mixed gas passing through the flame hole plate from the chamber is made combustible; and a ground fault conductive part, set to ground potential, and overlapping in contact with a back surface of the flame hole distribution area of the flame hole plate.

[0011] Preferably, a vertical width and a horizontal width of the entire ground fault conductive part are larger than a vertical width and a horizontal width of the entire flame hole distribution area, and the ground fault conductive part is set in an arrangement covering the entire flame hole distribution area.

[0012] Preferably, the ground fault conductive part is in the shape of a mesh in which multiple linear parts made of metal intersect and are connected, and an area surrounded by the multiple linear parts is a ventilation opening allowing the mixed gas to pass therethrough.

[0013] Preferably, each of the linear parts of the ground fault conductive part is circular in cross-section, and an opening of the multiple flame holes are in an open state even at a position overlapping each of the linear parts.

[0014] Preferably, the ground fault conductive part includes a conductive film laminated on a back surface of the flame hole plate so as not to block the multiple flame holes.

[0015] Preferably, the combustion device according to the present disclosure further includes a burner case made of metal and having ground potential, the burner case forming the chamber on inside. The ground fault conductive part is electrically connected to the burner case.

[0016] Preferably, the combustion device according to the present disclosure further includes an attachment member made of metal and attaching the flame hole plate to the burner case. The attachment member includes a contact part that contacts the ground fault conductive part, thereby achieving electric conduction between the ground fault conductive part and the burner case via the attachment member.

[0017] Preferably, the combustion device according to the present disclosure further includes a sealing member surrounding a periphery of the flame hole plate and blocking an area between the flame hole plate and an inner peripheral wall of the chamber. The ground fault conductive part includes a protruding part protruding from the periphery of the flame hole plate and overlapping the sealing member. The contact part of the attachment member is in contact with the protruding part.

[0018] A water heater provided according to a second aspect of the present disclosure is a water heater characterized by including: a combustion device; and a heat exchanger, for recovering heat from combustion gas generated by the combustion device and for heating hot and cold water. As the combustion device, the combustion device provided according to the first aspect of the present disclosure may be used.

[0019] Preferably, the heat exchanger includes a can body made of metal and accommodating a heat transfer tube therein, and the can body is made of metal set to ground potential. The ground fault conductive part is electrically connected to the can body.

[0020] Other features and advantages of the present disclosure will become more apparent from the description of embodiments of the invention given below with reference to the accompanying drawings.BRIEF DESCRIPTION OF THE DRAWINGS

[0021] [FIG. 1] FIG. 1 is a perspective exploded view of a water heater according to the present disclosure. [FIG. 2] FIG. 2 is a cross-sectional view of main parts of the water heater illustrated in FIG. 1 in an assembled state. [FIG. 3] FIG. 3 is an enlarged cross-sectional view of main parts of FIG. 2. [FIG. 4] FIG. 4 is a perspective view illustrating an assembled state a flame hole plate and its accessories constituting a combustion device of the water heater illustrated in FIG. 1 and FIG. 2. [FIG. 5] FIG. 5 is a plan view of FIG. 4. [FIG. 6] FIG. 6 is a cross-sectional view taken along VI-VI of FIG. 5. [FIG. 7] FIG. 7 is an exploded cross-sectional view of FIG. 6. [FIG. 8] FIG. 8 is an exploded perspective view of FIG. 4. [FIG. 9] FIG. 9A is a plan view illustrating a combined structure of the flame hole plate and a ground fault conductive part illustrated in FIG. 4 to FIG. 8; FIG. 9B is a partially enlarged plan view of FIG. 9A. [FIG. 10] FIG. 10 is a cross-sectional view taken along X-X of FIG. 9B. [FIG. 11] FIG. 11A is a plan view of the flame hole plate illustrated in FIG. 9A to FIG. 10; FIG. 11B is a partially enlarged plan view of FIG. 11A. [FIG. 12] FIG. 12A is a plan view of the ground fault conductive part illustrated in FIG. 9A to FIG. 10; FIG. 12B is a cross-sectional view taken along XII-XII of FIG. 12A. [FIG. 13] FIG. 13 is an enlarged cross-sectional view of main parts illustrating another example of the present disclosure. [FIG. 14] FIG. 14A is a plan view of main parts illustrating another example of the present disclosure; FIG. 14B is a cross-sectional view taken along XIV-XIV of FIG. 14A. DESCRIPTION OF THE EMBODIMENTS

[0022] Preferred embodiments of the present disclosure will be specifically described below with reference to the drawings.

[0023] A water heater WH illustrated in FIG. 1 and FIG. 2 is configured as a hot water supply apparatus including a combustion device C and a heat exchanger HE, the combustion device C including a burner part B.

[0024] The heat exchanger HE is for recovering heat from combustion gas generated by the burner part B of the combustion device C and advancing downward, and for heating hot and cold water. As the heat exchanger HE, a conventionally known heat exchanger may be used. The heat exchanger HE includes a can body 8 of a substantially rectangular tubular shape in plan view, multiple body pipes 9A, and a heat transfer tube 9.

[0025] The multiple body pipes 9A are of a substantially horizontal U-shape in plan view, provided along an inner surface side of sidewalls 80a to 80c of the can body 8, and are connected in series via header flow paths 92a, 92b provided on a sidewall 80d of the can body 8. The heat transfer tube 9 is configured in which multiple straight tube bodies 90, which are joined to multiple fins 97 for heat recovery and extend in a horizontal direction, are connected in series via a bend tube 91 of a substantially U-shape outside the can body 8.

[0026] In the heat exchanger HE, hot and cold water is supplied to the uppermost body pipe 9A from a water intake port 98 thereof. This hot and cold water then flows through the body pipes 9A of multiple stages in an up-down direction via the header flow paths 92a, 92b and flows to the lower side, as illustrated by arrows N1 to N3 in FIG. 2. Next, the hot and cold water flows through the heat transfer tube 9 (multiple straight tube bodies 90 and bend tube 91) in the order as illustrated by arrows N4 to N7, and reaches a hot water outlet 99. During such a process, the hot and cold water is heated by the aforementioned combustion gas and is supplied from the hot water outlet 99 to a desired hot water supply destination.

[0027] The combustion device C includes, in addition to the burner part B, a fan 1 and a burner case 3. The fan 1 draws in external air from an intake port thereof and discharges the air from an discharge port. In this air circulation channel, hydrogen as fuel gas sent through a gas pipe (not illustrated) is introduced. Accordingly, a mixed gas (premixed gas) of hydrogen and air is generated. This mixed gas flows from an air supply opening 31 of the burner case 3 into a chamber 30 inside the burner case 3, and reaches the burner part B.

[0028] The burner part B is configured by combining a flame hole plate 4, a ground fault conductive part 5, a sealing member 6, and attachment members 7A, 7B respectively on upper and lower sides (also see FIG. 4 to FIG. 8).

[0029] The flame hole plate 4 is formed in the shape of a rectangular flat plate made of ceramic and being non-conductive (having low electrical conductivity). The flame hole plate 4 includes a flame hole distribution area 40A where multiple flame holes 40 which are through holes for passing the mixed gas are provided in a dispersedly arranged state. The multiple flame holes 40 are small-diameter circular through holes. For example, as illustrated in FIG. 11A and FIG. 11B, the multiple flame holes 40 are arranged side by side in a cross-hatching pattern (strictly speaking, a cross-hatching pattern in broken lines) in plan view.

[0030] As clearly indicated in FIG. 12A, the ground fault conductive part 5 is in the shape of a mesh in a cross-hatching pattern in plan view, in which multiple linear parts 50 made of metal intersect and are connected. An area of a diamond shape in plan view surrounded by the multiple linear parts 50 is a ventilation opening 51 for passing the mixed gas. It is also possible that the ground fault conductive part 5 is configured in which metal wires such as stainless steel wires are used as a member constituting the multiple linear parts 50 and are woven into a mesh shape. Each linear part 50 is preferably circular in cross-section, as illustrated in FIG. 12B. This facilitates a configuration in which the ground fault conductive part 5 does not block the flame hole 40, as will be described later.

[0031] As clearly indicated in FIG. 9A and FIG. 9B, the ground fault conductive part 5 overlaps an upper side of the flame hole plate 4 while in contact with a back surface (upper surface) of the flame hole plate 4. The ground fault conductive part 5 is of a size larger than an overall size of the flame hole distribution area 40A and the flame hole plate 4, and overlaps the flame hole plate 4 to cover the entire flame hole distribution area 40A. More specifically, a vertical width L1" and a horizontal width L2" of the flame hole distribution area 40A, a vertical width L1' and a horizontal width L2' of the flame hole plate 4, as well as a vertical width L1 and a horizontal width L2 of the ground fault conductive part 5, have the following relationships a and b: a: L 1 " < L 1 ′ < L 1 b: L 2 " < L 2 ′ < L 2

[0032] An outer peripheral edge being a portion of the ground fault conductive part 5 serves as a protruding part 52 protruding from a periphery of the flame hole plate 4 in plan view. As will be described later, the protruding part 52 overlaps a back surface of the sealing member 6 and contacts a contact part 74a of the attachment member 7A on the upper side. Accordingly, the ground fault conductive part 5 is set to ground potential.

[0033] The shape of the multiple linear parts 50 of the ground fault conductive part 5 and the arrangement of the multiple flame holes 40 of the flame hole plate 4 both exhibit a cross-hatching pattern in plan view. However, these linear parts 50 and flame holes 40 are different from each other in arrangement pitch and inclination angle so as not to overlap in an excessively large proportion.

[0034] As indicated by symbols Na and Nb in FIG. 10, portions are present where the linear part 50 overlaps the flame hole 40. In contrast, as mentioned above, since the linear part 50 is circular in cross-section, the linear part 50 does not block an opening of the flame hole 40 located below the linear part 50 into a fully closed state. The opening of the flame hole 40 is open even at a position overlapping the linear part 50, making it possible for the mixed gas to flow into the flame hole 40.

[0035] As clearly indicated in FIG. 7 and FIG. 8, the attachment member 7A on the upper side and the attachment member 7B on the lower side are conductive metal members, and are for holding the flame hole plate 4 and the ground fault conductive part 5 and attaching the same to the burner case 3. The attachment member 7B on the lower side is of a frame shape with an opening 70 of a rectangular shape provided in a central portion. A lower part of the flame hole plate 4 is fitted and held in the opening 70. A stopper protrusion 71 that prevents the flame hole plate 4 from falling is provided at a lower part of an inner peripheral surface of the opening 70.

[0036] The attachment member 7A on the upper side is a member for sandwiching the flame hole plate 4 and the ground fault conductive part 5 in combination with the attachment member 7B on the lower side. The attachment member 7A on the upper side includes: multiple flanges 72 of a rectangular frame shape; multiple upright walls 73 of a rectangular frame shape, standing upward from an inner peripheral edge of the flanges 72; and multiple protruding pieces 74, bent inward of the attachment member 7A from an upper end of the upright walls 73. The attachment member 7A on the upper side is assembled to the attachment member 7B on the lower side with the flange 72 overlapping an upper side of an outer peripheral edge of the attachment member 7B on the lower side. This assembly may be fixed using a fastening member such as a screw (not illustrated). A screw 68 to be described later can also be used.

[0037] As clearly indicated in FIG. 3 to FIG. 6, a portion near a tip of each of the multiple protruding pieces 74 of the attachment member 7A on the upper side is the contact part 74a that is in contact with an upper surface part of the ground fault conductive part 5. Preferably, the contact part 74a is set to overlap the protruding part 52 of the ground fault conductive part 5 while not overlapping the flame hole distribution area 40A of the flame hole plate 4. Accordingly, while the flame hole 40 is set so as not to be unduly blocked by each protruding piece 74, the ground fault conductive part 5 is electrically connected with the attachment member 7A on the upper side, which is useful for setting the ground fault conductive part 5 to ground potential, as will be described later.

[0038] The sealing member 6 is sandwiched between the attachment member 7A on the upper side and the attachment member 7B on the lower side. The sealing member 6 surrounds the periphery of the flame hole plate 4 and blocks an area between the flame hole plate 4 and an inner peripheral wall of the chamber 30. The sealing member 6 is non-conductive, but may alternatively be conductive. The protruding part 52 of the ground fault conductive part 5 protrudes from the periphery of the flame hole plate 4 and overlaps the back surface of the sealing member 6. The contact part 74a of the attachment member 7A on the upper side overlaps an upper side of the protruding part 52 in such a way as to be in contact with the protruding part 52.

[0039] As clearly indicated in FIG. 2 and FIG. 3, the attachment member 7A on the upper side and the attachment member 7B on the lower side constituting the burner part B are attached to a lower part of the burner case 3 using the screw 68. By this attachment, the burner part B is arranged to block a lower surface part of the chamber 30 in the burner case 3, and the chamber 30 is located on a back surface side (upper surface side) of the flame hole plate 4. The mixed gas supplied to the chamber 30 passes through the multiple flame holes 40 of the flame hole plate 4 and flows out to a front surface side (lower surface side) of the flame hole plate 4. This mixed gas is ignited using an ignition plug 69, and the mixed gas combusts in a combustion area CA on the lower surface side of the flame hole plate 4.

[0040] As mentioned above, the burner case 3 is made of metal and is set to ground potential. In contrast, the flange 72 of the attachment member 7A on the upper side is attached in a state that allows electrical conduction with the burner case 3. Accordingly, the ground fault conductive part 5 is also set to ground potential. In FIG. 3, a gasket 67 is interposed at a screw fastening point between the flange 72 and the burner case 3. The gasket 67 is a conductive gasket having heat resistance.

[0041] Next, effects of the combustion device C and the water heater WH including the combustion device C will be described.

[0042] In the case where a hot water supply operation is executed, the fan 1 is driven, and a mixed gas of air and hydrogen (fuel gas) is supplied to the chamber 30. As mentioned above, this mixed gas passes through each flame hole 40 of the flame hole plate 4 and combusts in the combustion area CA on the front surface side (lower surface side) of the flame hole plate 4. On the other hand, since the flame hole plate 4 is made of non-conductive ceramic, there is inherently a risk of the flame hole plate 4 being charged with static electricity. If the flame hole plate 4 is charged and an electrostatic discharge occurs on the back surface side of the flame hole plate 4, combined with the fact that the fuel gas in the mixed gas is hydrogen, which is easily ignitable, there is a risk of ignition of the mixed gas occurring in the chamber 30.

[0043] In contrast, in the present embodiment, the ground fault conductive part 5 having ground potential is provided in contact with the back surface side (upper surface side) of the flame hole plate 4, and electricity can be removed from the flame hole plate 4. In particular, since the size of the ground fault conductive part 5 is larger than the overall size of the flame hole distribution area 40A and the flame hole plate 4, the removal of electricity from each part of the flame hole plate 4 is relatively reliably ensured. Accordingly, the occurrence of electrostatic discharge in an area of the flame hole plate 4 facing the chamber 30 can be appropriately prevented or suppressed. As a result, device damage due to ignition of the mixed gas in the chamber 30 may be appropriately avoided.

[0044] Since the ground fault conductive part 5 is in the shape of a mesh that forms multiple ventilation openings 51, the ground fault conductive part has a high opening ratio, allowing the multiple linear parts 50 to avoid overlapping a large number of flame holes 40. As described with reference to FIG. 10, since the linear part 50 is circular in cross-section, even at a position where the flame hole 40 and the linear part 50 overlap each other, it is possible to keep the flame hole 40 in the open state. Accordingly, it can be prevented that the flame hole 40 is unduly blocked due to the presence of the ground fault conductive part 5, and the mixed gas can also be appropriately supplied to each of the multiple flame holes 40.

[0045] The attachment member 7A on the upper side is utilized as a means for electrically connecting the ground fault conductive part 5 to the burner case 3 and set the ground fault conductive part 5 to ground potential. Accordingly, there is no complexity such as separately attaching a dedicated component for setting ground potential to the ground fault conductive part 5. This configuration is rational, and it is also possible to appropriately simplify the configuration and reduce the manufacturing costs.

[0046] Furthermore, the ground fault conductive part 5 includes the protruding part 52 protruding from the periphery of the flame hole plate 4 and overlapping the sealing member 6. The contact part 74a of the attachment member 7A on the upper side overlaps the upper side of the protruding part 52. Accordingly, the protruding part 52 of the ground fault conductive part 5 is sandwiched and fixedly supported between the sealing member 6 and the attachment member 7A on the upper side. While a firm and stable attachment state of the ground fault conductive part 5 is achieved, the electrical connection of the contact part 74a to the ground fault conductive part 5 can be ensured. As mentioned above, since the contact part 74a of the attachment member 7A on the upper side is provided so as not to block the multiple flame holes 40 of the flame hole plate 4, it is possible to appropriately supply the mixed gas to each of the multiple flame holes 40.

[0047] FIG. 13, FIG. 14A and FIG. 14B illustrate another embodiment of the present disclosure. In these drawings, the same or similar elements to those of the aforementioned embodiment are designated by the same reference numerals, and repeated descriptions are omitted.

[0048] In a water heater WHa illustrated in FIG. 13, the attachment member 7A on the upper side and the attachment member 7B on the lower side are fastened to a flange 88 provided at an upper end of the can body 8 of the heat exchanger HE using screw members 66a and 66b. The can body 8 is made of metal and is set to ground potential. On the other hand, the attachment member 7A on the upper side is electrically connected to the can body 8 via the attachment member 7B on the lower side, thereby setting the ground fault conductive part 5 to ground potential as well. According to the present embodiment, the burner case 3 does not need to be made of metal and has ground potential.

[0049] In the embodiment illustrated in FIG. 14A and FIG. 14B, a ground fault conductive part 5A (portion in dotted pattern) is composed of a conductive film such as a metal coating film directly laminated on the back surface (upper surface) of the flame hole plate 4. The ground fault conductive part 5A is formed in, for example, a mesh shape such as a grid shape in plan view. Multiple flame holes 40 are provided in an arrangement avoiding the ground fault conductive part 5A. In the present embodiment, due to the presence of the ground fault conductive part 5A, an effect of preventing electrostatic discharge on the back surface side of the flame hole plate 4 can be achieved. The ground fault conductive part 5A can be made easy to manufacture, small in overall volume, and light in weight.

[0050] The present disclosure is not limited to the content of the above-described embodiments. The specific configuration of each part of the combustion device and the water heater including the same according to the present disclosure can be freely modified in design within the intended scope of the present disclosure.

[0051] In the above-described embodiments, the ground fault conductive part is configured in a mesh shape using a metal wire or the like, or is composed of a conductive film. However, the present disclosure is not limited thereto. The ground fault conductive part may have, for example, a configuration (so-called insert molding configuration) in which a portion of the ground fault conductive part formed separately from the flame hole plate is embedded in the flame hole plate. The ground fault conductive part may be in the shape of, for example, a porous plate, instead of a mesh. Furthermore, it is sufficient that the ground fault conductive part is a conductive part set to ground potential, and various means can be adopted as a specific means for setting ground potential. The size (vertical width and horizontal width) of the ground fault conductive part is preferably equal to or larger than the size of the flame hole distribution area, and more preferably equal to or larger than the size of the flame hole plate. However, the present disclosure is not limited thereto. For example, the ground fault conductive part can be of a size slightly smaller than that of the flame hole distribution area.

[0052] The flame hole plate is non-conductive (has low electrical conductivity), but is not limited to being made of ceramic. The specific shape, size, number, and arrangement of the multiple flame holes are also not limited. The fuel gas can be a hydrogen-containing gas instead of hydrogen.

[0053] The combustion device according to the present disclosure is not limited to one (reverse combustion type) in which the direction in which combustion air or combustion gas advances is downward, but can also be, for example, upward (forward combustion type). The combustion device according to the present disclosure does not need to be for hot water supply apparatuses, but can also be configured as a combustion device for, for example, hot air devices or incinerators, and its specific application is not limited. The water heater according to the present disclosure is not limited to a hot water supply apparatus for general hot water supply, bath water supply, heating water supply or the like, but broadly includes apparatuses that heat hot and cold water and generate hot water. The heat exchanger included in the water heater is not limited to one only capable of recovering sensible heat, but may be one capable of, for example, recovering both sensible heat and latent heat.

Claims

1. A combustion device comprising: a flame hole plate which is non-conductive, comprising a flame hole distribution area where a plurality of flame holes of a through hole shape are provided in a dispersedly arranged state; a chamber, provided adjacent to a back surface side of the flame hole plate, and guiding a mixed gas of fuel gas as hydrogen or a hydrogen-containing gas and air to the flame hole plate; a combustion area, provided on a front surface side of the flame hole plate, and where the mixed gas passing through the flame hole plate from the chamber is made combustible; and a ground fault conductive part, set to ground potential, and overlapping in contact with a back surface of the flame hole distribution area of the flame hole plate.

2. The combustion device according to claim 1, wherein a vertical width and a horizontal width of the entire ground fault conductive part are larger than a vertical width and a horizontal width of the entire flame hole distribution area, and the ground fault conductive part is set in an arrangement covering the entire flame hole distribution area.

3. The combustion device according to claim 1, wherein the ground fault conductive part is in shape of a mesh in which a plurality of linear parts made of metal intersect and are connected; and an area surrounded by the plurality of linear parts is a ventilation opening allowing the mixed gas to pass therethrough.

4. The combustion device according to claim 3, wherein each of the linear parts of the ground fault conductive part is circular in cross-section, and an opening of the plurality of flame holes are in an open state even at a position overlapping each of the linear parts.

5. The combustion device according to claim 1, wherein the ground fault conductive part comprises a conductive film laminated on a back surface of the flame hole plate so as not to block the plurality of flame holes.

6. The combustion device according to claim 1, further comprising: a burner case made of metal and having ground potential, forming the chamber on inside, wherein the ground fault conductive part is electrically connected to the burner case.

7. The combustion device according to claim 6, further comprising: an attachment member made of metal, attaching the flame hole plate to the burner case, wherein the attachment member comprises a contact part that contacts the ground fault conductive part, thereby achieving electric conduction between the ground fault conductive part and the burner case via the attachment member.

8. The combustion device according to claim 7, further comprising: a sealing member, surrounding a periphery of the flame hole plate, and blocking an area between the flame hole plate and an inner peripheral wall of the chamber, wherein the ground fault conductive part comprises a protruding part protruding from the periphery of the flame hole plate and overlapping the sealing member; and the contact part of the attachment member is in contact with the protruding part.

9. A water heater comprising: a combustion device; and a heat exchanger, for recovering heat from combustion gas generated by the combustion device and for heating hot and cold water, wherein the combustion device according to any one of claims 1 to 8 is used as the combustion device.

10. The water heater according to claim 9, wherein the heat exchanger comprises a can body made of metal and accommodating a heat transfer tube therein, and the can body is made of metal set to ground potential; and the ground fault conductive part is electrically connected to the can body.

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