water heater

Abstract

To provide a water heater which allows easy maintenance of a freeze prevention heater installed in the vicinity of a connection with a water inlet of a water supply pipe even if the water heater is of so-called slim type.SOLUTION: A water inlet 9 connected with an external water pipe is arranged at a position that is on the inner side in left-right direction with respect to a pump 46 on a bottom plate 6 of a housing 2, and a water supply pipe 40 is connected to the inside of the box body 2 of the water inlet 9. Also, a freeze prevention heater 81 for preventing freezing of the water supply pipe 40 is attached with an attachment screw 82 at a position which is in the vicinity of a connection of the water supply pipe 40 and which is concealed by the pump 46 when viewed from a side. A right-side face part 83 is formed by bending upward a side edge of the bottom plate 6 on the side on which the pump 46 is installed, and a maintenance opening 84 is formed in the right-side face part 83. Then, when moving the pump 46 from the installation position, the freeze prevention heater 81 and a screw head of the attachment screw 82 are exposed in the maintenance opening 84 when viewed from a right side of the box body 2.SELECTED DRAWING: Figure 9

Description

[Technical Field]

[0001] The present invention relates to a water heater having an antifreeze heater installed near the water inlet of a water supply pipe to prevent the water supply pipe from freezing. [Background technology]

[0002] Conventionally, components such as a connection part for connecting an external water pipe to a water supply pipe, a connection part for connecting a hot water tap to a hot water outlet pipe, and a connection part for connecting an external gas pipe to an internal gas pipe are provided at the bottom of a water heater. In order to enable maintenance around these connections, the side panels and top panel that make up the water heater housing are configured to be removable (for example, see Patent Document 1). [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Laid-Open No. 2002-310512 Summary of the Invention [Problem to be solved by the invention]

[0004] However, depending on the location of various pipes, some parts cannot be accessed simply by removing the side panels of the housing. For example, if an anti-freeze heater installed at a water supply pipe connection cannot be accessed simply by removing the side panels of the housing, extensive work is required, such as turning off the external water pipe and then disconnecting the water inlet from the water supply pipe inside the housing, making maintenance work such as replacing the anti-freeze heater extremely cumbersome. In particular, in so-called slim-type water heaters, where various components and parts are installed so that they overlap one another, the components and parts tend to be concentrated in the lower part of the water heater, making the above-mentioned problems even more pronounced.

[0005] Therefore, the present invention has been made in consideration of the above problems, and aims to provide a water heater that makes it easy to perform maintenance work on the anti-freeze heater installed near the connection point to the water inlet of the water supply pipe, even if it is a so-called slim type water heater. [Means for solving the problem]

[0006] In order to achieve the above-mentioned object, the present invention provides a water heater comprising a combustion chamber equipped with a burner within a housing, a controller for controlling the operation of the burner, and a pump for circulating hot and cold water between the housing and an external bath, wherein the controller is installed at the front lower part of the housing and the pump is installed at the rear lower part of the housing, while a water inlet to which an external water pipe is connected is provided at a position on the bottom plate of the housing that is inward in the left-right direction from the pump, a water supply pipe is connected to the inside of the housing at the water inlet, and an anti-freeze heater for preventing the water supply pipe from freezing is attached with mounting screws near the connection point of the water supply pipe and in a position hidden by the pump when viewed from the side, and further, the side edge of the bottom plate on the side where the pump is installed is bent upward, and an opening is opened in the bent part, and when the pump is moved from its installed position, the mounting screw is exposed in the opening when viewed from the side. [Effects of the Invention]

[0007] According to the present invention, a controller is installed on the lower front side of the housing, and a pump is installed on the lower rear side of the housing. A water inlet, to which an external water pipe is connected, is provided on the bottom plate of the housing, laterally inward of the pump, and a water supply pipe is connected to the water inlet inside the housing. Furthermore, an anti-freeze heater for preventing the water supply pipe from freezing is attached with a mounting screw near the connection point of the water supply pipe and in a position hidden by the pump when viewed from the side. Additionally, the side edge of the bottom plate on the side where the pump is installed is bent upward, and an opening is formed in the bent portion. When the pump is moved from its installed position, the mounting screw is exposed in the opening when viewed from the side. Therefore, even though this is a so-called slim-type water heater in which the controller is installed on the lower front side of the housing and the pump is installed on the lower rear side of the housing, the mounting screw of the anti-freeze heater installed near the connection point of the water supply pipe to the water inlet can be exposed in the opening simply by moving the pump from its installed position. In other words, maintenance work such as removing and replacing the anti-freeze heater can be performed without requiring major work such as turning off the external water pipe and then disconnecting the water inlet from the water supply pipe, making the work involved in maintaining the anti-freeze heater simpler than before. [Brief explanation of the drawings]

[0008] [Figure 1] FIG. 2 is an explanatory diagram showing the water heater from the front side. [Figure 2] FIG. 2 is an explanatory diagram showing the water heater from the front side with the front cover removed. [Figure 3] FIG. 2 is an explanatory diagram showing a cross section 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. 10 is an explanatory diagram of the lower rear part of the housing viewed from the right side with the side panels and back panel removed. [Figure 8] 8 is an explanatory diagram of the housing in the state of FIG. 7, viewed from the lower right. [Figure 9] 8 is an explanatory diagram of the lower rear part of the housing as seen from the right side with the pump removed from the state shown in FIG. 7.

[0023] FIG. [Figure 10] 10 is an explanatory diagram of the housing from the bottom right in the state shown in FIG. 9 with the bottom plate further removed. DETAILED DESCRIPTION OF THE INVENTION

[0009] DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A water heater according to an embodiment of the present invention will be described in detail below with reference to the drawings. (Explanation of the overall structure of the water heater) FIG. 1 is an explanatory diagram showing the water heater 1 from the front side. FIG. 2 is an explanatory diagram showing the water heater 1 from the front side with the front cover 4 removed. FIG. 3 is an explanatory diagram showing a cross section taken along line AA in FIG. 1. FIG. 4 is a perspective view of the interior of the housing 2 from the rear left, with the front cover 4, the left and right side panels 7A and 7B of the box body 3, the back panel 8, and the resin sheet 50 omitted. FIG. 5 is a perspective view of the interior of the housing 2 from the rear right, with the front cover 4, the left and right side panels 7A and 7B of the box body 3, the back panel 8, and the resin sheet 50 omitted. FIG. 6 is a perspective view of the interior of the housing 2 from the front right, with the front cover 4, the left and right side panels 7A and 7B of the box body 3, the back panel 8, and the resin sheet 50 omitted. FIG. 7 is an explanatory diagram of the lower rear portion of the housing 2 from the right side, with the side panels 7A and 7B and the back panel 8 removed. FIG. 8 is an explanatory diagram of the housing 2 in the state shown in FIG. 7, with the housing 2 in the lower right position. Fig. 9 is an explanatory diagram of the lower rear part of the housing 2 as seen from the right side with the pump 46 removed from the state of Fig. 7. Fig. 10 is an explanatory diagram of the housing 2 as seen from the lower right side with the bottom plate 6 further removed from the state of Fig. 9.

[0010] 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.

[0011] The box body 3 comprises a top plate 5, a bottom plate 6, left and right side plates 7A and 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 for connection to an external bathtub, and a bath supply port 12. 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 55, 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.

[0012] 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. The lower casing 17 houses multiple burner units 20, 20.... Each burner unit 20 is composed of multiple flat burners 21 extending in the front-rear direction, arranged side by side in the left-right direction. The number of burners 21 varies for each burner unit 20. As shown in FIG. 4, a combustion fan 22 is connected to the underside of the lower casing 17. The combustion fan 22 rotates around an axis extending in the front-rear direction by a fan motor 23 mounted on the rear side. The combustion fan 22 supplies combustion air to the burner units 20. A gas distribution unit 25 is mounted on the front side of the lower casing 17. The gas distribution unit 25 is equipped with multiple solenoid valves, and the burner unit 20 to be combusted can be switched 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.

[0013] 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 paths, are installed side by side within a single inner casing 18 and heated by a common burner unit 20.

[0014] The upper casing 19 houses a hot water secondary heat exchanger 32. The hot water secondary heat exchanger 32 houses 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 at the front and rear of the left side surface of the upper casing 19, so that the inlet ends and outlet ends communicate with each other. The upper casing 19 and the middle casing 18 communicate with each other at their rear ends. The upper casing 19 is supported in a downwardly tilted position, and is provided with flat drain pans 36 on the front and rear sides at its front. An exhaust port 37 is connected to the front side of the drain pan 36 and faces forward.

[0015] 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.

[0016] 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.

[0017] 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.

[0018] A resin sheet 50 is wound around the combustion chamber 16. As shown in Figures 2 and 3, 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.

[0019] A continuous conductive pattern 51, which meanders back and forth in the width direction and extends longitudinally, is printed on the resin sheet 50 over the entire length in the longitudinal direction. Both ends of the conductive pattern 51 are electrically connected to an electrical circuit board 66 (described later) to form an overheat prevention device. When abnormal overheating of the lower casing 17 or the middle casing 18 causes cracks or holes, 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 electrical circuit board 66 detects the change in resistance value and stops the supply of fuel gas, thereby extinguishing the burner unit 20.

[0020] A neutralizer 55 is disposed in front of the combustion chamber 16. The neutralizer 55 is a rectangular box when viewed from the front, and is filled with a neutralizing agent (not shown). Drain discharge pipes 56, 56 are connected to the front bottom surface of the upper casing 19 and the drain receiver 36 on the upper surface of the neutralizer 55. A drain pipe 57 is connected to the drain outlet 14 on the lower surface of the neutralizer 55.

[0021] 3, the upper part of the neutralizer 55 is fixed to bracket fittings 58 fixed downward from the middle casing 18 and the upper casing 19 via mounting fittings 59 that are L-shaped in side view. The lower part of the neutralizer 55 is fixed to a fixing bar 60 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 controller 65 is disposed below the neutralizer 55. The controller 65 includes an electrical board 66, a storage case 67, and a cover 68.

[0022] (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 65 drives 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 65 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.

[0023] As a result, the water supplied from the water supply pipe 40 exchanges heat with the combustion exhaust gas from the burner unit 20 as it flows through the heat absorption pipe 33 of the hot water secondary heat exchanger 32, recovering latent heat. The drain generated at this time is collected in the neutralizer 55 via the drain discharge pipe 56, neutralized with a neutralizing agent, and then discharged from the drain pipe 57 to the outside of the appliance. 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.

[0024] The electrical board 66 of the controller 65 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 the 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 electrical board 66 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 operation of the combustion fan 22. When the hot water tap is closed, the electrical board 66 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 drives the combustion fan 22 for a predetermined time (post-purge).

[0025] On the other hand, when the automatic switch on the hot water remote control or bath remote control is pressed, the electrical board 66 opens the drop water solenoid valve provided in the drop pipe 47 to pass water through the hot water primary heat exchanger 27 and the hot water secondary heat exchanger 32, igniting 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 provided in the drop pipe 47 reaches the set water volume, the electrical board 66 closes the drop water solenoid valve to stop the water flow and extinguishes the burner unit 20. Next, the electrical board 66 activates the pump 46 to circulate hot water between the bath heat exchanger 28 and the bathtub. At this time, the electrical board 66 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 heat exchange 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 electrical board 66 stops the combustion of the burner unit 20 and stops the pump 46.

[0026] (Explanation of anti-freeze heater maintenance structure) The water inlet 9 is located in the rearmost center in the left-right direction on the bottom plate 6 that constitutes the housing 2. The gas inlet 13 is located forward of the water inlet 9 on the bottom plate 6, and the drain outlet 14 is located further forward of the gas inlet 13, with the gas inlet 13 and drain outlet 14 positioned approximately in the center of the bottom plate 6 in the front-to-back direction. In addition, the hot water outlet 10 is located to the left of the gas inlet 13, while the bath return outlet 11 is located to the right of the gas inlet 13 and the bath supply outlet 12 is located to the right of the drain outlet 14. The reason these various outlets are located from the center to the back of the bottom plate 6 in this way is because the controller 65 is installed on the front of the bottom plate 6.

[0027] An external water pipe (not shown) is connected to the water inlet 9 outside the housing 2, while a water supply pipe 40 is connected inside the housing 2. An antifreeze heater 81 for preventing the water supply pipe 40 from freezing is attached to the connection portion of the water supply pipe 40 (above the water inlet 9), and a mounting screw 82 for attaching the antifreeze heater 81 is screwed in with the screw head facing to the right.

[0028] Furthermore, the pump 46 is installed on the right rear corner of the bottom plate 6, to the right of the anti-freeze heater 81 and the mounting screw 82. Therefore, the anti-freeze heater 81 and the mounting screw 82 are hidden behind the pump 46 when viewed from the right side, as shown in Figure 7. Furthermore, the combustion fan 22 and the fan motor 23 are installed above the anti-freeze heater 81 and the mounting screw 82.

[0029] In addition, a right side surface portion 83 is bent upward at the right edge of the bottom plate 6, and a maintenance opening 84 shaped like a long hole extending in the front-to-rear direction is provided at the rear of the right side surface portion 83. When the pump 46 is removed from its installed position by, for example, removing it or shifting it rearward and upward by a predetermined amount (for example, by shifting it rearward by approximately 3 mm and upward by approximately 7 mm), the anti-freeze heater 81 and the heads of the mounting screws 82 become exposed within the maintenance opening 84 when viewed from the right side of the housing 2, as shown in FIG. 9. When the right side surface portion 83 and the maintenance opening 84 are attached to the right side surface 7B during assembly of the housing 2, the right side surface portion 83 and the maintenance opening 84 are covered from the right side by the side surface 7B.

[0030] To explain maintenance of the anti-freeze heater 81 installed in the position described above, first remove the side panel 7B to expose the right side surface 83 and the maintenance opening 84. Next, move the pump 46, for example, by shifting it from its installed position, to expose the anti-freeze heater 81 and the heads of the mounting screws 82 within the maintenance opening 84. Finally, insert a tool through the maintenance opening 84 to remove the mounting screws 82 and remove the anti-freeze heater 81. This allows maintenance of the anti-freeze heater 81, such as replacing the anti-freeze heater 81. In other words, maintenance of the anti-freeze heater 81 does not require the complicated steps of stopping the flow of water through the water pipe or disconnecting the water inlet 9 from the water supply pipe 40. Furthermore, it does not require the complicated steps of removing the controller 65 or the combustion fan 22.

[0031] (Effects of the invention relating to the maintenance structure for antifreeze heaters) In the water heater 1 having the above-described configuration, the combustion chamber 16 is installed behind the neutralizer 55 within the housing 2, the controller 65 is installed at the lower front side of the housing 2, and the pump 46 and combustion fan 22 are installed at the lower rear side of the housing 2, resulting in a so-called slim water heater 1. In this water heater 1, a water inlet 9 to which an external water pipe is connected is provided in a position on the bottom plate 6 of the housing 2 that is laterally inward of the pump 46, and a water supply pipe 40 is connected to the water inlet 9 inside the housing 2. Furthermore, an anti-freeze heater 81 for preventing the water supply pipe 40 from freezing is attached with a mounting screw 82 near the connection point of the water supply pipe 40 and in a position hidden by the pump 46 when viewed from the side. In addition, the side edge of the bottom plate 6 on the side where the pump 46 is installed is bent upward to form a right side surface 83, and a maintenance opening 84 is opened in the right side surface 83. When the pump 46 is moved from its installed position, the anti-freeze heater 81 and the heads of the mounting screws 82 are exposed within the maintenance opening 84 when viewed from the right side of the housing 2. Therefore, even though the water heater 1 is a so-called slim type, for the anti-freeze heater 81 installed near the connection portion to the water inlet 9 of the water supply pipe 40, the mounting screws 82 of the anti-freeze heater 81 can be exposed within the maintenance opening 84 simply by moving the pump 46 from its installed position. In other words, the anti-freeze heater 81 can be removed for maintenance without requiring major work such as turning off the external water pipe and then disconnecting the water inlet 9 from the water supply pipe 40, which simplifies the work involved in maintaining the anti-freeze heater 81 compared to conventional methods.

[0032] The water heater of the present invention is not limited to the above-described embodiment, and the overall configuration of the water heater as well as the configuration related to the maintenance structure of the anti-freeze heater can be modified as needed.

[0033] For example, in the above embodiment, the pump is installed on the rear right corner of the housing, but the pump may also be installed on the rear left corner of the housing. In this case, the anti-freeze heater can be attached with mounting screws in a position hidden by the pump when viewed from the left, and the left edge of the bottom plate can be folded upward and an opening can be provided in the folded part to expose the mounting screws. Furthermore, the installation locations of outlets other than the water inlet (hot water outlet, bath return outlet, bath supply outlet) are not limited to those in the above embodiment, and the design can be changed as appropriate to determine which part of the bottom plate they are installed on. Furthermore, in the above embodiment, the right side surface and the maintenance opening are covered by the side panel when the side panel is attached, but it is also possible to configure the right side surface and the maintenance opening to remain exposed after the side panel is attached, and ultimately when the housing is assembled. [Explanation of symbols]

[0034] 1··Water heater, 2··Housing, 6··Bottom plate, 9··Water inlet, 16··Combustion chamber, 20··Burner unit, 40··Water supply pipe, 46··Pump, 65··Controller, 81··Anti-freeze heater, 82··Mounting screws, 83··Right side, 84··Maintenance opening.

Claims

[Claim 1] A water heater comprising a combustion chamber equipped with a burner, a controller for controlling the operation of the burner, and a pump for circulating hot water between the combustion chamber and an external bath, The controller is installed on the front side of the lower part of the housing, and the pump is installed on the rear side of the lower part of the housing, A water inlet to which an external water pipe is connected is provided at a location on the bottom plate of the housing that is laterally inward of the pump, and a water supply pipe is connected to the water inlet on the inside of the housing; an antifreeze heater for preventing the water supply pipe from freezing is attached with a mounting screw near the connection portion of the water supply pipe and at a position hidden by the pump when viewed from the side; Furthermore, the side edge of the bottom plate on which the pump is installed is bent upward, and an opening is opened in the bent portion, When the pump is moved from its installed position, the mounting screws are exposed in the opening when viewed from the side.

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