water heater

Abstract

To enable a drain discharge pipe and a neutralizer to be connected to an exhaust top that receives drain generated in a secondary heat exchanger without any trouble even when a water heater employs a single-heat-exchanger and two-water-channel type in which a space in a housing is narrow, and to suppress cost increase while maintaining durability of the drain discharge pipe.SOLUTION: In a combustion chamber inside a housing, an upper casing 19 that houses a hot water supply secondary heat exchanger 32 is provided so as to protrude further forward than a middle casing 18; an outlet 66 and an exhaust top 36 are provided at a front surface of the upper casing 19; a rear surface of the exhaust top 36 has a two-stage drawing shape in which a deep drawn part 61 provided on an upper side and protruding rearward, and a shallow drawn part 62 provided in communication with the lower side of the deep drawn part 61 and shallower in a front-back direction than the deep drawn part 61 are formed; the front surface of the upper casing 19 is connected to the deep drawn part 61; and a drain discharge port 67 is formed in the shallow drawn part 62.SELECTED DRAWING: Figure 9

Description

[Technical Field]

[0001] The present disclosure relates to a latent heat recovery water heater equipped with a primary heat exchanger and a secondary heat exchanger. [Background technology]

[0002] A water heater includes a combustion chamber housing a burner and a heat exchanger, as well as a controller for controlling the burner and other components. A latent heat recovery water heater, which incorporates two heat exchangers, is also known: a primary heat exchanger that primarily recovers sensible heat from the burner's combustion exhaust and a secondary heat exchanger that primarily recovers latent heat from the combustion exhaust that has passed through the primary heat exchanger. In this latent heat recovery water heater, as disclosed in Patent Document 1, an exhaust top with an exhaust pipe attached to the front side is provided in front of the secondary heat exchanger to discharge condensate generated in the secondary heat exchanger, and the condensate generated in the secondary heat exchanger flows into the exhaust top. The exhaust top is formed by welding front and rear drawn sheet metal parts, and the lower front part is connected to a neutralizer located to the side of the combustion chamber via a condensate discharge pipe. The condensate that flows from the exhaust top into the neutralizer via the condensate discharge pipe is neutralized in the neutralizer and then discharged to the outside of the housing.

[0003] On the other hand, there are water heaters of the one-can, two-channel type, in which a heat transfer pipe on the hot water supply side that forms one water flow path and a heat transfer pipe on the bath side that forms the other water flow path are installed side by side within the same space of a single combustion chamber, and penetrate through a common fin (for example, Patent Document 2). In the case of this one-can, two-channel type, the width of the combustion chamber is reduced compared to a two-can, two-channel type, in which two combustion chambers are installed side by side and separate heat exchangers are provided for the hot water supply side and the bath side, so there is an advantage that the housing can be slimmed down and installation can be space-saving. However, in such a one-tank, two-channel water heater, the space inside the housing is narrow, so it may not be possible to connect the drain discharge pipe to the front of the exhaust top as in Patent Document 1. Therefore, Patent Document 3 discloses an invention that uses a three-pronged connecting member (drain discharge pipe) made of a flexible material such as rubber to easily connect the secondary heat exchanger and the exhaust section (exhaust top) to a neutralization device (neutralizer) even in a narrow space. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Patent No. 5133393 [Patent Document 2] Patent No. 6970964 (Figure 2) [Patent Document 3] Patent No. 6507840 Summary of the Invention [Problem to be solved by the invention]

[0005] However, the connecting member in Patent Document 3 is limited to flexible materials such as rubber, and therefore there is a risk that durability will decrease with age. Furthermore, since connection ports are formed in three directions, the shape of the connection member becomes complicated, which leads to an increase in manufacturing costs.

[0006] Therefore, the present disclosure aims to provide a water heater that allows a drain discharge pipe and a neutralizer to be connected without any problems to the exhaust top that receives the drain generated in the secondary heat exchanger, even in a one-tank, two-channel type where the space inside the housing is narrow, while maintaining the durability of the drain discharge pipe and suppressing cost increases. [Means for solving the problem]

[0007] In order to achieve the above object, the present disclosure provides a combustion chamber in which a burner is disposed within a housing, and two primary heat exchangers which are arranged in the same space above the burner as the combustion chamber, through which the burner's combustion exhaust passes, and to which different water passages are connected, a secondary heat exchanger connected to the upstream side of at least one of the water passages is disposed above the primary heat exchanger in the combustion chamber; A water heater in which an outlet for combustion exhaust gas that has passed through the secondary heat exchanger is provided in a housing portion of the secondary heat exchanger in the combustion chamber, an exhaust top that receives drainage generated in the secondary heat exchanger is provided at the outlet, and a neutralizer is connected to a drainage outlet provided in the exhaust top via a drainage discharge pipe, The secondary heat exchanger housing portion is provided so as to protrude forward from the housing portions of the two primary heat exchangers, and an outlet and an exhaust top are provided on the front surface of the housing portion of the secondary heat exchanger, The rear surface of the exhaust top has a two-stage drawn shape, with a deep drawn section on the upper side that protrudes rearward, and a shallow drawn section that is connected to the lower side of the deep drawn section and is shallower in front and behind the deep drawn section.The front surface of the secondary heat exchanger storage section is connected to the deep drawn section, and a drain outlet is formed in the shallow drawn section. Another aspect of the present disclosure is characterized in that, in the above configuration, a drain reservoir is formed inside the shallow drawn portion. Another aspect of the present disclosure is characterized in that, in the above configuration, the drain outlet is located at either the left or right lower corner of the shallow drawn portion, and the lower end of the shallow drawn portion slopes downward in the left-right direction toward the drain outlet. [Effects of the Invention]

[0008] According to the present disclosure, even in a one-boiler, two-channel type where the space inside the housing is narrow, the drain discharge pipe and neutralizer can be connected without any problems to the exhaust top that receives the drain generated in the secondary heat exchanger. In particular, the shallow drawn portion ensures a relatively large space behind the exhaust top, which reduces restrictions on the material and shape of the drain discharge pipe, thereby maintaining the durability of the drain discharge pipe and preventing increases in costs. According to another aspect of the present disclosure, in addition to the above-mentioned effects, a drain reservoir is formed inside the shallow drawn portion, so that even a small amount of drain can be discharged to the neutralizer. Also, the risk of drain scattering due to exhaust pressure is reduced. According to another aspect of the present disclosure, in addition to the above effects, the drain outlet is located at either the left or right lower corner of the shallow drawn portion, and the lower end of the shallow drawn portion slopes downward in the left-right direction toward the drain outlet, so that the drain running along the inner surface of the shallow drawn portion can be efficiently guided to the drain outlet. [Brief explanation of the drawings]

[0009] [Figure 1] FIG. [Figure 2] FIG. 2 is a front view of the water heater with the front cover removed. [Figure 3] FIG. 2 is a cross-sectional view taken along line AA in FIG. [Figure 4] This is an oblique view of the inside of the housing as seen from the left rear, with the front cover, the left and right side panels of the box body, the back panel, and the resin sheet omitted. [Figure 5] This is an oblique view of the inside of the housing as seen from the right rear, with the front cover, the left and right side panels of the box body, the back panel, and the resin sheet omitted. [Figure 6] This is an oblique view of the inside of the housing as seen from the front right, with the front cover, the left and right side panels of the box body, the back panel, and the resin sheet omitted. [Figure 7] FIG. 3 is an enlarged cross-sectional view taken along the line BB in FIG. 2. [Figure 8] FIG. 3 is an enlarged cross-sectional view taken along the line CC in FIG. 2. [Figure 9] FIG. 2 is an exploded perspective view of the exhaust top from the front. [Figure 10] FIG. 2 is an exploded perspective view of the exhaust top from the rear. DETAILED DESCRIPTION OF THE INVENTION

[0010] Hereinafter, embodiments of the present disclosure will be described with reference to the drawings. (Explanation of the overall structure of the water heater) Fig. 1 is a front view showing an example of a water heater, Fig. 2 is a front view with a front cover removed, and Fig. 3 is a cross-sectional view taken along line AA in Fig. 1. The water heater 1 has a vertically long box-shaped housing 2. The housing 2 comprises a box body 3 and a front cover 4. The box body 3 is open at the front and has a deep bottom at the front and rear. The front cover 4 is screwed to the box body 3 from the front to close the front. A cylindrical exhaust port 37, which is provided on the front side of the upper casing 19 described below, penetrates the top of the front cover 4. The box body 3 comprises a top plate 5, a bottom plate 6, left and right side plates 7A, 7B, and a back plate 8. The bottom plate 6 is provided with a water inlet 9 for connection to an external water pipe, a hot water outlet 10 for connection to an external hot water tap, a bath return port 11 and a bath supply port 12 for connection to an external bathtub. The center of the bottom plate 6 is provided with a gas inlet 13 for connection to an external gas pipe, and a drain port 14 for connection to a neutralizer 80, which will be described later. Mounting plates 15, 15 are provided above and below the back plate 8 for installation on a wall or the like.

[0011] A combustion chamber 16 is provided at the back side of the box body 3. The combustion chamber 16 includes a lower casing 17, a middle casing 18, and an upper casing 19 that are connected in the vertical direction. A plurality of burner units 20, 20... are housed in the lower casing 17. Each burner unit 20 is composed of a plurality of flat burners 21 extending in the front-rear direction and arranged side by side in the left-right direction. The number of burners 21 varies from one burner unit 20 to another. As shown in Figure 4, a combustion fan 22 is connected to the underside of the lower casing 17. The combustion fan 22 is rotated around an axis extending in the front-to-rear direction by a fan motor 23 provided on the rear side. The combustion fan 22 supplies combustion air to the burner unit 20. A gas distribution unit 25 is provided on the front side of the lower casing 17. The gas distribution unit 25 is equipped with a plurality of solenoid valves, and can switch the burner unit 20 to be combusted by opening and closing each solenoid valve. A gas pipe 26 equipped with a main valve and a proportional valve is connected to the upstream end of the burner unit 20. The gas pipe 26 is connected to the gas inlet 13.

[0012] The inner casing 18 houses a hot water supply primary heat exchanger 27 and a bath heat exchanger 28. The hot water supply primary heat exchanger 27 has a plurality of fins 29, 29... arranged at a predetermined interval in the left-right direction, and a hot water supply side heat transfer pipe 30 that penetrates each fin 29 in a serpentine manner in two rows, upper and lower. The bath heat exchanger 28 has each fin 29 and a bath side heat transfer pipe 31 that penetrates each fin 29 in a serpentine manner between the upper and lower rows of hot water supply side heat transfer pipes 30. In other words, the water heater 1 is a one-tank, two-channel type in which the hot water supply primary heat exchanger 27 and the bath heat exchanger 28, which have different water flow paths (hot water circuit and bath circuit), are installed side by side within a single inner casing 18 and heated by a common burner unit 20.

[0013] The upper casing 19 accommodates a hot water secondary heat exchanger 32. The hot water secondary heat exchanger 32 accommodates a plurality of heat absorption pipes 33, 33... formed in a serpentine shape. As shown in Fig. 4, both ends of each heat absorption pipe 33 are connected to an inlet header 34 and an outlet header 35 provided on the left side surface of the upper casing 19 at the front and rear, and the inlet ends and the outlet ends are connected to each other. The upper casing 19 and the intermediate casing 18 are connected at their rear ends. The upper casing 19 is supported in a position inclined downwards at the front and protrudes further forward than the intermediate casing 18. An exhaust top 36 that is flat from front to back is attached to the front side of the upper casing 19. An exhaust port 37 is connected to the front side of the exhaust top 36 and faces forward. Details of the exhaust top 36 will be described later. A water supply pipe 40 is connected to the water inlet 9. The water supply pipe 40 is routed upward on the left side of the combustion chamber 16 and connected to the inlet header 34 of the upper casing 19. A relay pipe 41 is connected to the outlet header 35. As shown in Fig. 5 , the relay pipe 41 runs from the left side of the combustion chamber 16, passes behind the intermediate casing 18, and wraps around to the right side of the intermediate casing 18. The relay pipe 41 is then routed forward on the right side of the intermediate casing 18 and connected to the upstream end of the lower section of the hot water supply side heat transfer pipe 30 of the hot water supply primary heat exchanger 27.

[0014] A hot water outlet pipe 42 is connected to the downstream end of the upper section of the hot water supply side heat transfer pipe 30. As shown in Fig. 6, the hot water outlet pipe 42 wraps around from the right side of the inner casing 18 to the front of the inner casing 18, crosses the front of the inner casing 18, and moves to the left side of the inner casing 18. Then, as shown in Fig. 4, the hot water outlet pipe 42 bends downward at the front left of the inner casing 18, is routed downward in a straight line, and is then connected to the tap water outlet 10. A straight section 43 of the hot water outlet pipe 42 is connected to the water supply pipe 40 via a bypass pipe 44. A bath return pipe 45 is connected to the bath return port 11. As shown in Figures 4 to 6, the bath return pipe 45 is routed upward along the right side of the combustion chamber 16 via a pump 46. The bath return pipe 45 then crosses the front of the inner casing 18, wraps around to the left side of the inner casing 18, and is connected to the upstream end of the bath-side heat transfer pipe 31 of the bath heat exchanger 28. The bath return pipe 45 is connected to the hot water outlet pipe 42 via a drop pipe 47. A bath supply pipe 48 is connected to the bath supply port 12. The bath supply pipe 48 is routed upward along the right side of the combustion chamber 16, and then connected to the downstream end of the bath-side heat transfer pipe 31 on the right side of the middle casing 18.

[0015] A resin sheet 50 is wound around the combustion chamber 16. As shown in Figures 1, 2 and 7, the resin sheet 50 is a strip-shaped body wound around the combustion chamber 16, spanning the lower casing 17 and the middle casing 18. The resin sheet 50 is wound around the outside of each pipe along the inner surfaces of the left and right side plates 7A, 7B and the back plate 8, so that it is not in contact with the combustion chamber 16. A continuous conductive pattern 51, which meanders back and forth in the width direction and extends in the longitudinal direction, is printed on the resin sheet 50 over the entire longitudinal length. Both ends of the conductive pattern 51 are electrically connected to a controller 90 (described later) to form an overheat prevention device. When abnormal overheating of the lower casing 17 or the middle casing 18 causes cracks, holes, or the like, resulting in the emission of combustion exhaust gas, the resin sheet 50 melts and the conductive pattern 51 breaks, causing the resistance value to suddenly increase or become infinite. The controller 90, upon detecting the change in resistance value, stops the supply of fuel gas and extinguishes the burner unit 20.

[0016] (Explanation of exhaust top) As shown in Figures 8 to 10, the exhaust top 36 is made up of a front plate 55, a rear plate 56, and a pair of seals 57, 57. The front plate 55 is a press-formed metal plate that has a horizontally long rectangular shape when viewed from the front, and has a folded portion 58 formed on its outer periphery toward the rear. The front plate 55 is formed with a circular connection port 59 that protrudes forward. The exhaust port 37 is attached to the connection port 59. The rear plate 56 is a metal plate that is press-formed into a horizontally elongated rectangular shape in front view, the same shape as the front plate 55. However, the rear plate 56 is provided with a drawn portion 60 that protrudes rearward. This drawn portion 60 has a two-stage drawn shape consisting of a deep drawn portion 61 and a shallow drawn portion 62. The deep drawn portion 61 is formed on the upper side of the rear plate 56 in a horizontally elongated rectangular shape when viewed from the front. However, the lower surface of the deep drawn portion 61 forms a downwardly inclined surface 63 that slopes downward as it extends forward. The rear surface of the deep drawn portion 61 forms a rearward inclined surface 64 that protrudes rearward as it extends downward. A communication port 65 is formed in the rearward inclined surface 64. A combustion exhaust outlet 66 is formed in the front surface of the upper casing 19 corresponding to the communication port 65.

[0017] The shallow drawn portion 62 is formed in communication with the underside of the deep drawn portion 61. The lower end of the shallow drawn portion 62 slopes downward toward the left. A drain outlet 67 is formed in the lower left corner of the rear surface of the shallow drawn portion 62. Therefore, a flat drain reservoir 68 that communicates with the deep drawn portion 61 and the drain outlet 67 is formed in the shallow drawn portion 62 between the front plate 55 and the rear plate 56. The sealing materials 57, 57 are strip-shaped and bent into a U-shape and an inverted U-shape to fit the upper and lower outer shapes of the front plate 55 and the rear plate 56. The exhaust top 36 is assembled by screwing the front plate 55 and the rear plate 56 together with the sealing materials 57, 57 sandwiched inside the folded portion 58 of the front plate 55. The exhaust top 36 is assembled to the upper casing 19 by screwing the rear surface of the deep-drawn portion 61 to the front surface of the upper casing 19. In this state, the communication port 65 of the rear inclined surface 64 and the outlet 66 of the upper casing 19 face each other and communicate with each other.

[0018] A first drain discharge pipe 70 is connected to the drain discharge port 67. The first drain discharge pipe 70 has a curved pipe section 71 and a straight pipe section 72. The upper end of the curved pipe section 71 is connected to the drain discharge port 67 and pulled rearward, then curves downward and opens at its lower end to the right. The straight pipe section 72 is connected to the lower end of the curved pipe section 71 and extends linearly to the right, and is connected to a neutralizer 80 (described below). In this way, the exhaust top 36 is attached to the front surface of the upper casing 19, which protrudes forward more than the intermediate casing 18, and the shallow drawn portion 62 is formed in the rear plate 56. This ensures a space between the exhaust top 36 and the intermediate casing 18 in the front-to-rear direction, allowing the first drain discharge pipe 70 to be connected to the rear plate 56 of the exhaust top 36 without any problems. A deep bottom portion 73 is formed on the front lower surface of the upper casing 19, which slopes downward toward the front, and is lowest at the center from left to right. The upper end of a second drain discharge pipe 74 is connected to the deep bottom portion 73. The second drain discharge pipe 74 extends downward and has its lower end connected to the straight pipe portion 72 of the first drain discharge pipe 70. Here, a T-pipe 75 is used at the connection point between the straight pipe portion 72 and the second drain discharge pipe 74, and the connection is made with a quick fastener 76.

[0019] A neutralizer 80 is disposed below the exhaust top 36 and in front of the combustion chamber 16. The neutralizer 80 is a rectangular box-shaped body when viewed from the front, and is filled with a neutralizing agent (not shown). A drain inlet 81 protrudes upward from the right side of the top surface of the neutralizer 80. As shown in FIGS. 2, 8, and 9, a short cylindrical connection port 81a protrudes from the left side of the drain inlet 81. The straight pipe section 72 of the first drain discharge pipe 70 is fitted over and connected to the connection port 81a. By connecting the straight pipe section 72 of the first drain discharge pipe 70 sideways in this manner, a downward biasing force from the curved pipe section 71 is applied to the straight pipe section 72, and the straight pipe section 72 is positioned above the neutralizer 80 without any back-and-forth rattle. As shown in Figures 3 and 8, the upper part of the neutralizer 80 is fixed to bracket fittings 83 fixed downward from the middle casing 18 and the upper casing 19 via mounting fittings 84 that are L-shaped in side view. The lower part of the neutralizer 80 is fixed to a fixing bar 85 that is fixed to the lower casing 17 on the front side of the gas distribution unit 25 and extends in the left-right direction. A drain pipe 82 (Figures 2, 5, and 6) that connects to the drain outlet 14 of the bottom plate 6 is connected to the underside of the neutralizer 80. A controller 90 is disposed below the neutralizer 80. The controller 90 is configured by housing an electrical board 92 of the same shape in a storage case 91 that is horizontally elongated in front view, and is installed at the frontmost side on the bottom plate 6.

[0020] (Explanation of water heater operation) In the water heater 1, normal hot water supply is performed as follows. When the hot water tap on the external pipe connected to the hot water outlet 10 is opened to allow water to flow into the appliance and this water flow is detected by a hot water supply volume sensor installed in the water supply pipe 40, the controller 90 rotates the combustion fan 22 for a predetermined time to discharge (pre-purge) the combustion exhaust gas accumulated in the combustion chamber 16. Thereafter, the controller 90 opens the main valve of the gas pipe 26 and the solenoid valve of the gas distribution unit 25, opens the proportional valve to a predetermined opening, supplies gas to the burner unit 20, and activates the igniter to ignite the burner unit 20. As a result, the water supplied from the water supply pipe 40 exchanges heat with the combustion exhaust gas from the burner unit 20 while flowing through the heat absorption pipe 33 of the hot water supply secondary heat exchanger 32, thereby recovering latent heat. The hot water that has passed through the hot water secondary heat exchanger 32 then flows to the hot water primary heat exchanger 32 via the relay pipe 41, and as it flows through the hot water side heat transfer pipe 30, it exchanges heat with the combustion exhaust gas from the burner unit 20 to recover sensible heat. The hot water heated in this way passes through the hot water outlet pipe 42 and external piping and is discharged from the hot water tap.

[0021] The controller 90 monitors the outlet temperature, which is the temperature of the hot water discharged immediately after the hot water primary heat exchanger 27, using an outlet temperature thermistor installed in the hot water outlet pipe 42, and drives a distribution valve installed in the bypass pipe 44 to control the flow rate (bypass rate) to the bypass pipe 44 so that the outlet temperature is maintained within a temperature range that can prevent the generation of drainage or overheating in the hot water primary heat exchanger 27. In addition, the controller 90 monitors the outlet hot water temperature using an outlet hot water temperature thermistor installed in the outlet hot water pipe 42, and controls the opening and closing of each solenoid valve in the gas distribution unit 25 and adjusts the opening of the proportional valve so that the outlet hot water temperature becomes the set temperature specified by the external hot water remote control or bath remote control, and also continuously changes the amount of air by controlling the rotation speed of the combustion fan 22. When the hot water tap is closed, the controller 90 confirms that the signal from the hot water volume sensor has stopped, closes the main valve and the solenoid valve of the gas distribution unit 25 to extinguish the burner unit 20, and rotates the combustion fan 22 for a predetermined time (post-purge).

[0022] On the other hand, when the automatic switch on the hot water supply remote control or bath remote control is pressed, the controller 90 opens the drop water solenoid valve installed in the drop pipe 47 to pass water through the hot water primary heat exchanger 27 and the hot water secondary heat exchanger 32, and starts combustion in the burner unit 20. Hot water from the hot water outlet pipe 42 is supplied to the external bathtub through the drop pipe 47 and the bath return pipe 45. When the water volume detected by the bath water volume sensor installed in the drop pipe 47 reaches the set water volume, the controller 90 closes the drop water solenoid valve to stop the water flow and extinguishes the burner unit 20. Next, the controller 90 activates the pump 46 to circulate hot water between the bath heat exchanger 28 and the bathtub. At this time, the controller 90 monitors the temperature of the circulating hot water using thermistors installed in the bath return pipe 45 and bath supply pipe 48, and if it detects a drop from the set temperature, it ignites the burner unit 20 and supplies combustion air using the combustion fan 22, just as when supplying hot water. Therefore, the bath circulating water circulating between the bath heat exchanger 28 and the bathtub is heated to the set temperature by exchanging heat with the combustion exhaust gas from the burner unit 20 as it flows through the bath-side heat transfer pipe 31. When the set temperature is reached, the controller 90 stops the combustion of the burner unit 20 and stops the pump 46.

[0023] The combustion exhaust gas that passes through the hot water supply secondary heat exchanger 32 in the upper casing 19 passes through the exhaust top 36 from the outlet 66 and is discharged to the outside from the exhaust port 37. When drain is generated in this flow of the combustion exhaust gas, some of the drain flows from the deep drawn portion 61 to the shallow drawn portion 62 of the exhaust top 36 and is collected in the drain storage portion 68. The downwardly sloping lower end of the shallow drawn portion 62 leads to the drain discharge port 67 and is discharged to the neutralizer 80 via the first drain discharge pipe 70. The other part of the drain is collected in the deep bottom portion 73 of the upper casing 19 and is discharged to the neutralizer 80 via the second drain discharge pipe 74 and the straight pipe portion 72 of the first drain discharge pipe 70. The drain neutralized in the neutralizer 80 is discharged to the outside of the appliance via the drain pipe 82. Here, the drain reservoir 68 is lower than the lower end of the exhaust port 37 and is located downward in the horizontal direction passing through the center of the exhaust port 37, so the influence of the exhaust pressure is reduced. Furthermore, since the drain reservoir 68 has a short dimension in the front-rear direction, the surface area of ​​the drain stored therein that is exposed to exhaust pressure can be small, making it less susceptible to the effects of exhaust pressure. Furthermore, since the volume of the drain reservoir 68 is small, even a small amount of the stored drain easily flows into the first drain discharge pipe 70. Therefore, the exhaust pressure of the combustion exhaust gas makes it difficult for the drain to fly out from the exhaust port 37 to the outside.

[0024] (Effect of disclosure regarding drain discharge pipes) The water heater 1 of the above type has, within the casing 2, a combustion chamber 16 in which a burner 21 is arranged, and a water heater primary heat exchanger 27 and a bath heat exchanger 28 (an example of two primary heat exchangers) which are arranged above the burner 21 in the same space as the combustion chamber 16, through which the combustion exhaust from the burner 21 passes and to which a water heater circuit and a bath circuit (an example of different water flow paths) are connected, and above the water heater primary heat exchanger 27 and the bath heat exchanger 28 within the combustion chamber 16, a water heater secondary heat exchanger 32 (an example of a secondary heat exchanger) which is connected upstream of the water flow path on the water heater side is arranged. In addition, an outlet 66 for the combustion exhaust gas that has passed through the hot water secondary heat exchanger 32 is provided in the upper casing 19 (an example of a storage section for a secondary heat exchanger) in the combustion chamber 16, and an exhaust top 36 is provided at the outlet 66 to receive the drain generated in the hot water secondary heat exchanger 32, and a neutralizer 80 is connected to a drain discharge port 67 provided in the exhaust top 36 via a first drain discharge pipe 70 (an example of a drain discharge pipe). The upper casing 19 is provided so as to protrude forward from the middle casing 18 (an example of a housing for two primary heat exchangers), and an outlet 66 and an exhaust top 36 are provided on the front surface of the upper casing 19, and a drain outlet 67 is formed on the rear surface of the exhaust top 36. The neutralizer 80 is disposed in front of the hot water supply primary heat exchanger 27 and below the hot water supply secondary heat exchanger 32, and has a connection port 81a for the first drain discharge pipe 70 formed horizontally at the top. The first drain discharge pipe 70 is disposed behind the exhaust top 36, and has a curved pipe portion 71 that is connected to the drain discharge port 67 and drawn out rearward, and then bent downward, and a straight pipe portion 72 that is bent sideways from the lower end of the curved pipe portion 71 above the neutralizer 80 and extends in the left-right direction, and the straight pipe portion 72 is connected to a connection port 81 a of the neutralizer 80, The upper end of a second drain discharge pipe 74 (an example of a second drain discharge pipe) is connected to the underside of the upper casing 19 of the hot water secondary heat exchanger 32, and the lower end of the second drain discharge pipe 74 is connected to the straight pipe section 72 of the first drain discharge pipe 70.

[0025] According to this configuration, the straight pipe portion 72 extending in the left-right direction of the first drain discharge pipe 70 is connected to the neutralizer 80, so that even when the assembly in which the first drain discharge pipe 70 is connected to the neutralizer 80 is formed, there are fewer protruding portions except for the curved pipe portion 71. This reduces the risk that the first drain discharge pipe 70 will get in the way during transportation or storage, or will be deformed by hitting something. Furthermore, because the first drain discharge pipe 70 has a curved pipe portion 71, the elasticity of the curved pipe portion 71 can be used to easily connect the curved pipe portion 71 to the drain discharge port 67 and the straight pipe portion 72 to the connection port 81a of the neutralizer 80. Therefore, the first drain discharge pipe 70 can be connected easily and in a short time. In other words, the work of connecting the hot water supply secondary heat exchanger 32 and the exhaust top 36 to the neutralizer 80 using the first drain discharge pipe 70 can be performed without any problems, making it possible to maintain productivity. The lower end of the second drain discharge pipe 74 is inclined downward in a direction away from the connection port 81a and is connected to the T-shaped pipe 75 that forms part of the straight pipe section 72, so that any positional relationship error can be absorbed by the curved pipe section 71 and the lower end of the second drain discharge pipe 74. This makes it easy to connect the straight pipe section 72 to the second drain discharge pipe 74 and to the connection port 81a of the neutralizer 80.

[0026] In the disclosure relating to the drain discharge pipe, the drain discharge port and the first drain discharge pipe may be attached in the left-right reversed manner compared to the above embodiment. The connection port of the neutralizer is not limited to a structure in which a straight pipe section is fitted onto the outside of the short cylindrical protrusion. For example, the connection port may be an opening into which a straight pipe section is inserted for connection. The slope of the lower end of the second drain discharge pipe may be curved rather than straight. The second drain discharge pipe may be connected to the straight pipe section without using a T-pipe. In the disclosure relating to the drain discharge pipe, the rear plate of the exhaust top does not have to have the above-mentioned two-stage tapered shape.

[0027] (Effect of disclosure regarding the two-stage throttle shape of the exhaust top) The water heater 1 of the above type has, within the casing 2, a combustion chamber 16 in which a burner 21 is arranged, and a water heater primary heat exchanger 27 and a bath heat exchanger 28 (an example of two primary heat exchangers) which are arranged above the burner 21 in the same space as the combustion chamber 16, through which the combustion exhaust from the burner 21 passes and to which a water heater circuit and a bath circuit (an example of different water flow paths) are connected, and above the water heater primary heat exchanger 27 and the bath heat exchanger 28 within the combustion chamber 16, a water heater secondary heat exchanger 32 (an example of a secondary heat exchanger) which is connected upstream of the water flow path on the water heater side is arranged. In addition, an outlet 66 for the combustion exhaust gas that has passed through the hot water secondary heat exchanger 32 is provided in the upper casing 19 (an example of a storage section for a secondary heat exchanger) in the combustion chamber 16, and an exhaust top 36 is provided at the outlet 66 to receive the drain generated in the hot water secondary heat exchanger 32, and a neutralizer 80 is connected to a drain discharge port 67 provided in the exhaust top 36 via a first drain discharge pipe 70 (an example of a drain discharge pipe). The upper casing 19 is arranged to protrude further forward than the middle casing 18 (an example of a housing section for two primary heat exchangers), and an outlet 66 and an exhaust top 36 are provided on the front surface of the upper casing 19. The rear surface of the exhaust top 36 has a two-stage drawn shape formed with a deep drawn section 61 provided on the upper side and protruding rearward, and a shallow drawn section 62 provided below the deep drawn section 61 and shallower in front and behind than the deep drawn section 61. The front surface of the upper casing 19 is connected to the deep drawn section 61, and a drain discharge outlet 67 is formed in the shallow drawn section 62. With this configuration, even in the case of a one-tank, two-channel type where the space inside the housing 2 is narrow, the first drain discharge pipe 70 and the neutralizer 80 can be connected without any problems to the exhaust top 36 that receives the drain generated in the hot water secondary heat exchanger 32. Furthermore, because the shallow drawn portion 62 ensures a relatively large space behind the exhaust top 36, there are fewer restrictions on the material and shape of the first and second drain discharge pipes 70, 74. This makes it possible to maintain the durability of the first and second drain discharge pipes 70, 74 and prevent costs from increasing.

[0028] Since a drain reservoir 68 is formed inside the shallow drawn portion 62, even a small amount of drain can be discharged to the neutralizer 80. In addition, the risk of drain scattering due to exhaust pressure is reduced. The drain outlet 67 is disposed in the lower left corner of the shallow drawn portion 62, and the lower end of the shallow drawn portion 62 is inclined downward in the left-right direction toward the drain outlet 67. Therefore, the drain running along the inner surface of the shallow drawn portion 62 can be efficiently guided to the drain discharge port 67.

[0029] In the disclosure relating to the two-stage drawn shape of the exhaust top, the drain outlet is not limited to being located in the lower left corner, but may be located in the lower right corner or in the lower center in the left-right direction. The lower end of the deep drawn portion may also be inclined downward to the right depending on the location of the drain outlet, or may be inclined downward from both ends in the left-right direction toward the center. The lower end of the deep drawn portion may also be flat without being inclined. The depth and rear view shape of the deep drawn portion and the shallow drawn portion are not limited to the above-described forms and can be changed as appropriate. For example, the rear surface of the deep drawn portion does not need to be an inclined surface if the upper casing is not downwardly inclined.

[0030] In common with each disclosure, the exhaust port of the exhaust top is not limited to being circular when viewed from the front, but may be elliptical when viewed from the front, or the like. In the above embodiment, a primary heat exchanger and a secondary heat exchanger are provided only on the hot water supply side, but a secondary heat exchanger may also be provided on the bath side. The water flow path is not limited to a hot water supply circuit and a bath circuit, but may also be a hot water supply circuit and a heating circuit. Each disclosure is also applicable to hot water heaters dedicated to heating or bath use. [Explanation of symbols]

[0031] 1··Water heater, 2··Case, 3··Box body, 4··Front cover, 16··Combustion chamber, 17··Lower casing, 18··Middle casing, 19··Upper casing, 20··Burner unit, 21··Burner, 22··Combustion fan, 26··Gas piping, 27··Water heater primary heat exchanger, 28··Bath heat exchanger, 29··Fin, 32··Water heater secondary heat exchanger, 36··Exhaust top, 37··Exhaust port, 40··Water supply pipe, 41··Relay pipe, 42··Water outlet pipe, 45··Bath Return pipe, 48··Bath supply pipe, 50··Resin sheet, 55··Front plate, 56··Back plate, 57··Sealing material, 60··Drawn section, 61··Deep drawn section, 62··Shallow drawn section, 65··Communication port, 66··Outlet, 67··Drain discharge port, 68··Drain storage section, 70··First drain discharge pipe, 71··Bent pipe section, 72··Straight pipe section, 74··Second drain discharge pipe, 75··T-pipe, 80··Neutralizer, 81a··Connection port, 82··Distribution pipe, 90··Controller, 92··Electrical board.

Claims

1. A combustion chamber in which a burner is disposed and two primary heat exchangers, which are arranged in the same space as the combustion chamber above the burner and through which combustion exhaust from the burner passes and to which different water passages are connected, are arranged within the housing; a secondary heat exchanger connected to an upstream side of at least one of the water passages is disposed above the primary heat exchanger in the combustion chamber; A water heater in which an outlet for combustion exhaust gas that has passed through the secondary heat exchanger is provided in a housing portion of the secondary heat exchanger in the combustion chamber, an exhaust top that receives drain generated in the secondary heat exchanger is provided at the outlet, and a neutralizer is connected to a drain discharge port provided in the exhaust top via a drain discharge pipe, The housing portion for the secondary heat exchanger is provided to protrude forward from the housing portions for the two primary heat exchangers, and the outlet and the exhaust top are provided on a front surface of the housing portion for the secondary heat exchanger, The rear surface of the exhaust top has a two-stage drawn shape, with a deep drawn section on the upper side that protrudes rearward, and a shallow drawn section that is connected to the lower side of the deep drawn section and is shallower in front and behind than the deep drawn section, and the front surface of the secondary heat exchanger storage section is connected to the deep drawn section, and the drain outlet is formed in the shallow drawn section.

2. The water heater according to claim 1, wherein a drain reservoir is formed inside the shallow drawn portion.

3. The water heater according to claim 1 or 2, characterized in that the drain outlet is located at either the left or right lower corner of the shallow drawn portion, and the lower end of the shallow drawn portion slopes downward in the left-right direction toward the drain outlet.

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