Manufacturing method of water heater and water heater

Abstract

To reduce the time needed for drying of a secondary heat exchanger.SOLUTION: A manufacturing method of a water heater is a manufacturing method of a water heater including a primary heat exchanger and a secondary heat exchanger. The manufacturing method includes: an assembly step in which the primary heat exchanger and the secondary heat exchanger are assembled; a test step in which a test run of the water heater is conducted; and a dry step in which a heat transfer pipe of the secondary heat exchanger is dried after the test step. The manufacturing method further includes an application step in which a surface acting agent is applied to the heat transfer pipe of the secondary heat exchanger before the assembly step.SELECTED DRAWING: Figure 7

Description

[Technical Field]

[0001] The present disclosure relates to a method for manufacturing a water heater and a water heater. [Background technology]

[0002] Conventionally, a water heater equipped with a secondary heat exchanger is known, such as the water heater described in JP 2023-19517 A (Patent Document 1 below). In the manufacturing process of such a water heater, a final inspection is carried out after the product is completely assembled. In this final inspection, the performance of the water heater is confirmed by actually using the water heater. However, when the water heater is used, drainage is generated in the secondary heat exchanger. This drainage can wet the packaging material used to package the water heater or corrode the water heater, so after the final inspection, a drying process is carried out to dry the secondary heat exchanger. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Publication No. 2023-19517 Summary of the Invention [Problem to be solved by the invention]

[0004] The drying process of the secondary heat exchanger as described above can take time. [Means for solving the problem]

[0005] The method for manufacturing a water heater disclosed herein is a method for manufacturing a water heater equipped with a primary heat exchanger and a secondary heat exchanger, and includes an assembly process for assembling the primary heat exchanger and the secondary heat exchanger, a testing process for performing a trial run of the water heater, and a drying process for drying the heat transfer tubes of the secondary heat exchanger after the testing process, and further includes an application process for applying a surfactant to the heat transfer tubes of the secondary heat exchanger before the assembly process.

[0006] The water heater of the present disclosure is a water heater including a primary heat exchanger and a secondary heat exchanger, and a surfactant is applied to the heat transfer tubes of the secondary heat exchanger. [Effects of the Invention]

[0007] According to the present disclosure, the time required to dry the secondary heat exchanger can be reduced. [Brief explanation of the drawings]

[0008] [Figure 1] FIG. 1 is a front view of a water heater according to an embodiment. [Figure 2] FIG. 2 is an explanatory diagram conceptually illustrating the configuration of the water heater. [Figure 3] FIG. 3 is a cross-sectional view taken along the line AA in FIG. [Figure 4] FIG. 4 is an enlarged perspective view showing the internal structure of the water heater. [Figure 5] FIG. 5 is a perspective view of the secondary heat exchanger. [Figure 6] FIG. 6 is a plan view of the heat transfer tube of the secondary heat exchanger. [Figure 7] FIG. 7 is a flowchart showing a method for manufacturing a water heater. [Figure 8] FIG. 8 is a flowchart showing a method for manufacturing a water heater that is different from the method shown in FIG. DETAILED DESCRIPTION OF THE INVENTION

[0009] [Description of the embodiments of the present disclosure] First, embodiments of the present disclosure will be listed and described.

[0010] (1) The method for manufacturing a water heater disclosed herein is a method for manufacturing a water heater having a primary heat exchanger and a secondary heat exchanger, and includes an assembly process for assembling the primary heat exchanger and the secondary heat exchanger, a testing process for test-running the water heater, and a drying process for drying the heat transfer tubes of the secondary heat exchanger after the testing process, and further includes an application process for applying a surfactant to the heat transfer tubes of the secondary heat exchanger before the assembly process.

[0011] According to this method of manufacturing a water heater, the surfactant applied to the heat transfer tubes of the secondary heat exchanger reduces the surface tension of the drain adhering to the heat transfer tubes of the secondary heat exchanger during the testing process, making it easier for the drain to drip from the heat transfer tubes of the secondary heat exchanger. This reduces the time required to dry the heat transfer tubes of the secondary heat exchanger.

[0012] (2) The manufacturing method of the water heater disclosed herein is a manufacturing method of a water heater having a primary heat exchanger and a secondary heat exchanger, and includes an assembly process of assembling the primary heat exchanger and the secondary heat exchanger, a testing process of performing a trial run of the water heater, and a drying process of drying the heat transfer tubes of the secondary heat exchanger after the testing process, wherein the secondary heat exchanger has a housing that houses the heat transfer tubes and is provided with an exhaust port, and the heat transfer tubes are connected to a supply pipe that supplies water into the secondary heat exchanger near the exhaust port, and the manufacturing method of the water heater further includes, after the assembly process, an application process of applying a surfactant to the heat transfer tubes of the secondary heat exchanger through the exhaust port of the secondary heat exchanger.

[0013] According to this method for manufacturing a water heater, the surface tension of the drain adhering to the heat transfer tube of the secondary heat exchanger is reduced by applying a surfactant to the heat transfer tube of the secondary heat exchanger during the testing process, making it easier for the drain to drip from the heat transfer tube of the secondary heat exchanger. This reduces the time required to dry the heat transfer tube of the secondary heat exchanger. In addition, since the heat transfer tube is connected to the supply pipe near the exhaust port, the portion of the heat transfer tube located near the exhaust port is particularly low temperature and prone to condensate generation. Therefore, by applying a surfactant to the heat transfer tube from the exhaust port to the portion near the exhaust port, condensate can be effectively dripped from the heat transfer tube.

[0014] (3) In the method for manufacturing a water heater described in (2), the application step is preferably carried out during the testing step or the drying step.

[0015] According to this method for manufacturing a water heater, the coating process can be performed during the testing process or the drying process, thereby reducing the working time for the coating process.

[0016] (4) In the method for manufacturing a water heater according to (1) or (2), it is preferable that the water heater is vibrated in the drying step.

[0017] According to this method for manufacturing a water heater, vibration of the water heater makes it easier for drainage to drip from the heat transfer tube, thereby further shortening the time required for the drying process.

[0018] (5) The water heater of the present disclosure is a water heater including a primary heat exchanger and a secondary heat exchanger, and a surfactant is applied to the heat transfer tube of the secondary heat exchanger.

[0019] In such a water heater, the surfactant applied to the heat transfer tubes of the secondary heat exchanger reduces the surface tension of the drain adhering to the heat transfer tubes of the secondary heat exchanger when the water heater is in use, making it easier for the drain to drip from the heat transfer tubes of the secondary heat exchanger.

[0020] [Details of the embodiments of the present disclosure] Embodiments of the present disclosure will be described with reference to Figures 1 to 8. The present disclosure is not limited to these examples, but is defined by the scope of the claims, and is intended to include all modifications within the meaning and scope of the claims.

[0021] [Overall structure of the water heater] The water heater 1 of this embodiment is a latent heat recovery type water heater. As shown in Figures 1 to 3, the water heater 1 is configured to include a primary heat exchanger 100, a secondary heat exchanger 200, a burner device 300, and an exhaust hood 400.

[0022] The primary heat exchanger 100 includes two heat exchangers: a hot water supply primary heat exchanger 110 and a bath primary heat exchanger 120 .

[0023] The secondary heat exchanger 200 is disposed above the primary heat exchanger 100. The secondary heat exchanger 200 includes two heat exchangers: a hot water supply secondary heat exchanger 210 connected to the upstream side of the hot water supply primary heat exchanger 110, and a bath secondary heat exchanger 220 connected to the upstream side of the bath primary heat exchanger 120.

[0024] The burner device 300 is connected to the lower part of the primary heat exchanger 100. The burner device 300 comprises two burner groups, a hot water supply burner group 310 and a bathtub burner group 320, and a burner case 330. The hot water supply burner group 310 generates combustion exhaust gas to be sent to the hot water supply primary heat exchanger 110 and the hot water supply secondary heat exchanger 210. The bathtub burner group 320 generates combustion exhaust gas to be sent to the bathtub primary heat exchanger 120 and the bathtub secondary heat exchanger 220.

[0025] The exhaust hood 400 has a lower end connected to the primary heat exchanger 100 and an upper end connected to the secondary heat exchanger 200. The lower end of the exhaust hood 400 opens downward and communicates with the space inside the primary heat exchanger 100. The upper end of the exhaust hood 400 opens forward and communicates with the space inside the secondary heat exchanger 200.

[0026] The water heater 1 circulates the combustion exhaust gas generated by each burner group 310, 320 of the burner device 300 through the primary heat exchanger 100 above the burner device 300. In the primary heat exchanger 100, heat is exchanged between the combustion exhaust gas and the water flowing through the hot water supply primary heat exchanger 110 and the bath primary heat exchanger 120. The water heater 1 functions to recover sensible heat from the combustion exhaust gas using the primary heat exchanger 100.

[0027] In the water heater 1, the combustion exhaust gas from the burner device 300 is guided from the primary heat exchanger 100 through the exhaust hood 400 to the secondary heat exchanger 200. The combustion exhaust gas that has passed through the primary heat exchanger 100 passes through the exhaust hood 400 and enters the secondary heat exchanger 200 from the rear. In other words, the secondary heat exchanger 200 is disposed downstream of the primary heat exchanger 100 in the path of the combustion exhaust gas. The secondary heat exchanger 200 exchanges heat between the water flowing through the hot water supply secondary heat exchanger 210 and the bath secondary heat exchanger 220 and the combustion exhaust gas. The water heater 1 functions to recover the latent heat of the combustion exhaust gas using the secondary heat exchanger 200.

[0028] [Water heater circuit configuration] As shown in FIG. 2, the water heater 1 is configured to include two circuits: a hot water supply circuit 10 and a bath circuit 20.

[0029] 1 and 2, in the hot water supply circuit 10, water flows into a water inlet pipe 12 (an example of a supply pipe) from a water inlet 11 connected to a water supply source such as a water supply, passes through a hot water supply secondary heat exchanger 210 and a hot water supply primary heat exchanger 110 in this order, and is heated by heat exchange with the combustion exhaust gas from a hot water supply burner group 310. The water then flows through a hot water outlet pipe 13 and flows out from a hot water outlet 14.

[0030] The bath circuit 20 is a circuit that circulates and heats the hot water in the bathtub B. The bath circuit 20 uses a circulation pump P to draw the hot water in the bathtub B into a return pipe 22 (an example of a supply pipe) from a hot water inlet 21 that is connected to an opening in the bathtub B, and passes the water through the bath secondary heat exchanger 220 and then the bath primary heat exchanger 120, reheating the hot water by exchanging heat with the combustion exhaust from the bath burner group 320. The hot water, now at a higher temperature, is then discharged into the bathtub B from the hot water outlet 24 via the supply pipe 23.

[0031] 1 and 2, the water heater 1 includes a drain hose 31 and a neutralizer 32. The upstream side of the drain hose 31 is connected to a drain outlet 251 (see FIG. 3) of the secondary heat exchanger 200, and the downstream side is connected to the neutralizer 32. The drain generated by the recovery of latent heat in the secondary heat exchanger 200 is discharged to the outside of the secondary heat exchanger 200 via the drain outlet 251 and sent to the neutralizer 32 through the drain hose 31.

[0032] As shown in FIG. 1, the water heater 1 includes a controller 33 as a control device. The controller 33 is configured, for example, as a known microcomputer or the like, and is configured to acquire signals from various sensors provided in the water heater 1 and to control various actuators provided in the water heater 1. For example, when the water flow sensor (not shown) detects the flow of water in the water inlet pipe 12, the water heater 1 operates the hot water supply burner group 310 to generate hot water. As another example, when the water flow sensor (not shown) detects the flow of water in the return pipe 22, the water heater 1 operates the bath burner group 320 to reheat the bath.

[0033] [Primary heat exchanger] Next, the configuration of the primary heat exchanger 100 will be described. The primary heat exchanger 100 is a sensible heat recovery heat exchanger. As shown in Figures 1, 3, and 4, the primary heat exchanger 100 is configured to include a water heater body 130 and heat transfer tubes 111 and 121. The heat transfer tubes 111 and 121 are disposed within the water heater body 130 and include a plurality of straight pipe sections extending in the front-to-rear direction, and a plurality of bent connecting sections that connect adjacent straight pipe sections. The water heater body 130 and the heat transfer tubes 111 and 121 can be made of, for example, copper, which has excellent thermal conductivity.

[0034] The can body 130 has a generally rectangular shape in a plan view that is long in the left-right direction, and is formed into a cylindrical shape that is perforated vertically. As shown in Fig. 3, the can body 130 has its interior divided into left and right sections by a partition 131. The primary heat exchanger 100 is divided by the partition 131 into a hot water supply primary heat exchanger 110 on the right side of the partition 131 and a bath primary heat exchanger 120 on the left side of the partition 131 (see Fig. 2).

[0035] The straight pipe sections of the heat transfer tubes 111, 121 are straight pipes with a circular cross section. As shown in FIG. 3, each straight pipe section of the heat transfer tubes 111, 121 is arranged to extend forward and backward, with both ends penetrating the front and rear surfaces of the water heater body 130. Each straight pipe section is fixed to the penetrating portion of the water heater body 130 by brazing or the like. The straight pipe sections are arranged side by side in the left-right direction. As shown in FIGS. 1 and 4, the heat transfer tubes 111, 121 are arranged on the outside of the water heater body 130 and include connecting sections that connect the front ends or rear ends of two adjacent straight pipe sections. As a result, the multiple straight pipe sections are connected in a serpentine shape. In other words, each of the heat transfer tubes 111, 121 forms a single serpentine pipe. The heat transfer tube 111 is included in the hot water supply primary heat exchanger 110. The heat transfer tube 121 is included in the bath primary heat exchanger 120.

[0036] As shown in Fig. 4, one end of the heat transfer pipe 111 (more specifically, the rear right end) is connected to one end of the hot water relay pipe 15. The other end of the hot water relay pipe 15 is connected to an outlet of the hot water secondary heat exchanger 210, which will be described later. As shown in Fig. 1, the hot water outlet pipe 13 is connected to the other end of the heat transfer pipe 111 (more specifically, the front end near the partition 131). That is, in the hot water primary heat exchanger 110, water that flows in from the rear right side of the boiler body 130 meanders and flows in a direction approaching the partition 131, and flows out to the front side.

[0037] As shown in Figure 1, one end of the heat transfer pipe 121 (more specifically, the end near and forward of the partition 131) is connected to one end of the bath relay pipe 40. The other end of the bath relay pipe 40 is connected to the outlet of the bath secondary heat exchanger 220, which will be described later. As shown in Figure 4, the other end of the heat transfer pipe 121 (more specifically, the end at the rear left) is connected to the outflow pipe 23. That is, in the bath primary heat exchanger 120, water that flows in from the front side near the partition 131 meanders and flows away from the partition 131, and then flows out to the rear side.

[0038] [Secondary heat exchanger] Next, the configuration of the secondary heat exchanger 200 will be described. The secondary heat exchanger 200 is a latent heat recovery type heat exchanger. As shown in Fig. 3, the secondary heat exchanger 200 is disposed above the primary heat exchanger 100. The secondary heat exchanger 200 and the primary heat exchanger 100 are connected by an exhaust hood 400 (described later) for introducing the combustion exhaust gas that has passed through the primary heat exchanger 100 into the secondary heat exchanger 200.

[0039] As shown in Fig. 5, the secondary heat exchanger 200 is configured to include a housing 230 and heat transfer tubes 211 and 221. As shown in Fig. 6, the heat transfer tube 211 includes a plurality of straight pipe sections 211A extending in the left-right direction and a plurality of connecting sections 211B having a bent shape and connecting adjacent straight pipe sections 211A. The heat transfer tube 221 is configured in substantially the same manner as the heat transfer tube 211. The housing 230 and the heat transfer tubes 211 and 221 can be made of stainless steel, which has excellent corrosion resistance.

[0040] As shown in Fig. 5, a partition 231 is provided inside the housing 230 to divide the internal space of the housing 230 into left and right sections. The hot water supply secondary heat exchanger 210 and the bath secondary heat exchanger 220 are arranged side by side in the left-right direction within the housing 230, via this partition 231. The secondary heat exchanger 200 is divided by the partition 231 into the hot water supply secondary heat exchanger 210 on the right side of the partition 231 and the bath secondary heat exchanger 220 on the left side of the partition 231.

[0041] The housing 230 includes a box portion 232 that is open at the top and has a bottom, and a lid portion 233 that closes the top opening of the box portion 232. The box portion 232 has a shape that is long in the left-right direction. The housing 230 is provided with an annular packing interposed between the box portion 232 and the lid portion 233. The packing prevents gas from passing between the box portion 232 and the lid portion 233.

[0042] As shown in FIG. 3, an inlet 245 penetrating in the front-rear direction is provided on the rear surface of the box portion 232. The inlet 245 is an opening for introducing combustion exhaust gas into the interior of the housing 230. Two inlet ports 245 are provided; the one on the right introduces combustion exhaust gas into the hot water supply secondary heat exchanger 210 and the one on the left introduces combustion exhaust gas into the bath secondary heat exchanger 220. As shown in FIG. 5, an outlet 246 (an example of an exhaust port) penetrating in the front surface of the box portion 232 is provided. The outlet 246 is an opening for discharging combustion exhaust gas from inside the housing 230. That is, in the secondary heat exchanger 200, the combustion exhaust gas flows through the housing 230 from rear to front. As shown in FIG. 3, an exhaust hood 400 is attached by screws around the inlet 245 on the rear surface of the box portion 232. An exhaust pipe 500 is attached by screws around the outlet 246 on the front surface of the box portion 232.

[0043] As shown in Fig. 5, the housing 230 is formed with a drain outlet 251 that penetrates the bottom surface of the box portion 232 in the vertical direction. The drain outlet 251 is provided at a position corresponding to the partition portion 231. As shown in Fig. 3, the drain outlet 251 is connected to a drain hose 31. Drainage generated by the recovery of latent heat is discharged from the drain outlet 251 via the drain hose 31. The bottom surface of the box portion 232 is inclined downward as it approaches the front.

[0044] As shown in Fig. 5, a hot water supply inlet portion 268 and a hot water supply outlet portion 273 are provided on the right surface of the box portion 232. The hot water supply inlet portion 268 is arranged in the front part of the right surface of the box portion 232. The hot water supply outlet portion 273 is arranged in the rear part of the right surface of the box portion 232. As shown in Figs. 1 and 4, the hot water supply inlet portion 268 is connected to the downstream side of the water inlet pipe 12. The hot water supply outlet portion 273 is connected to the piping on the inlet side of the hot water supply primary heat exchanger 110 (specifically, the upstream end of the hot water supply relay pipe 15).

[0045] As shown in FIG. 5 , the hot water supply secondary heat exchanger 210 is configured to include a plurality of heat transfer tubes 211. The heat transfer tubes 211 extend in a serpentine manner along a predetermined planar direction. The plurality of heat transfer tubes 211 are stacked vertically and housed in the housing 230. The heat transfer tubes 211 have one end and the other end that open in the same direction (rightward). One end (front side) of each heat transfer tube 211 communicates with a hot water supply inlet 268 via a first header 265. The other end (rear side) of each heat transfer tube 211 communicates with a hot water supply outlet 273 via a second header 270. In the hot water supply secondary heat exchanger 210, water is passed through the heat transfer tubes 211 in parallel to perform heat exchange. Specifically, the temperature of the passing water increases from one end of the heat transfer tube 211 to the other end due to heat exchange with the combustion exhaust gas. In other words, the temperature of the front portion of the heat transfer tube 211 is lower than that of the rear portion of the heat transfer tube 211 .

[0046] Similar to the right side of the box section 232, a bath inlet section 269 and a bath outlet section 274 are also provided on the left side of the box section 232. The bath inlet section 269 is located at the front of the left side of the box section 232. The bath outlet section 274 is located at the rear of the left side of the box section 232. As shown in FIG. 1, the bath inlet section 269 is connected to the downstream side of the return pipe 22. The bath outlet section 274 is connected to the inlet side piping of the bath primary heat exchanger 120 (specifically, the upstream end of the bath relay pipe 40).

[0047] As shown in FIG. 5, the bath secondary heat exchanger 220 is configured with multiple heat transfer tubes 221, similar to the hot water supply secondary heat exchanger 210. The heat transfer tubes 221 have one end and the other end that open in the same direction (left). One end (front side) of each heat transfer tube 221 is connected to the bath inlet 269. The other end (rear side) of each heat transfer tube 221 is connected to the bath outlet 274. In the bath secondary heat exchanger 220, water is passed through each heat transfer tube 221 in parallel to perform heat exchange. In detail, the temperature of the passing water increases from one end of the heat transfer tube 221 to the other end due to heat exchange with the combustion exhaust gas. In other words, the temperature of the front portion of the heat transfer tube 221 is lower than that of the rear portion of the heat transfer tube 221.

[0048] In this embodiment, a surfactant is applied to the outer surfaces of the heat transfer tubes 211, 221 of the secondary heat exchanger 200. The surfactant reduces the surface tension of drainage adhering to the outer surfaces of the heat transfer tubes 211, 221 during operation of the water heater 1, making it easier for the drainage to drip from the heat transfer tubes 211, 221 of the secondary heat exchanger 200. The process of applying the surfactant to the outer surfaces of the heat transfer tubes 211, 221 will be described in detail below.

[0049] [Burner device] The burner device 300 burns combustion gas to generate combustion exhaust. As shown in FIG. 3, the burner device 300 includes a burner case 330, a hot water supply burner group 310 (see FIG. 2), and a bath burner group 320 (see FIG. 2). The burner case 330 is provided below the can body 130 of the primary heat exchanger 100. The burner case 330 has a generally rectangular shape in plan view that is elongated in the left-right direction and is open at the top end. The burner case 330 has a square cylindrical shape similar to the can body 130. The interior of the burner case 330 is divided into left and right spaces by a partition 331. The partition 331 provided in the burner case 330 is connected to the lower end of the partition 131 of the primary heat exchanger 100. As a result, the left and right spaces within the burner case 330 are partitioned in a manner that they are connected to the left and right spaces within the can body 130 of the primary heat exchanger 100, respectively.

[0050] As shown in Figure 2, the hot water supply burner group 310 is arranged on the right side of the burner device 300 (the space on the right side separated by the partition 331 in the burner case 330), and the bath burner group 320 is arranged on the left side of the burner device 300 (the space on the left side separated by the partition 331 in the burner case 330). As a result, the hot water supply burner group 310 is arranged below the hot water supply primary heat exchanger 110 and supplies combustion exhaust to the hot water supply circuit 10. The bath burner group 320 is arranged below the bath primary heat exchanger 120 and supplies combustion exhaust to the bath circuit 20.

[0051] An ignition plug 311 and a flame rod 312 are arranged in the space above the hot water supply burner group 310. Similarly, an ignition plug 321 and a flame rod 322 are arranged above the bath burner group 320. Wiring (not shown) is connected to the rear ends of the ignition plugs 311, 321 and the flame rods 312, 322, respectively.

[0052] [Exhaust hood] As shown in Figure 3, the exhaust hood 400 is disposed between the primary heat exchanger 100 and the secondary heat exchanger 200. The exhaust hood 400 connects the upper end opening of the can body 130 of the primary heat exchanger 100 with the inlet 245 at the rear of the housing 230 of the secondary heat exchanger 200, forming a passage for the combustion exhaust. The interior of the exhaust hood 400 is divided into left and right sections by a partition 401. The partition 401 connects the upper end of the partition 131 of the primary heat exchanger 100 with the rear end of the partition 231 of the secondary heat exchanger 200, forming spaces corresponding to the hot water supply circuit 10 and the bath circuit 20, respectively.

[0053] As shown in FIG. 4, the exhaust hood 400 is configured to have an exhaust hood main body 410 and an exhaust hood rear portion 420.

[0054] The exhaust hood body 410 is formed to bulge upward in the front-to-rear direction, gradually increasing in height from the front end toward the rear. The rear end of the exhaust hood body 410 opens rearward, and a plate-shaped mounting portion 411 is provided around the periphery of this opening. The exhaust hood rear portion 420 is formed in the shape of a square dish that bulges rearward. The lower portion of the exhaust hood rear portion 420 is attached to the mounting portion 411 of the exhaust hood body 410 so as to close the rear opening of the exhaust hood body 410.

[0055] The exhaust hood rear part 420 is fixed to the rear surface of the housing 230 by screws. An annular packing is provided between the rear surface of the housing 230 and the exhaust hood rear part 420. The packing prevents gas from passing between the rear surface of the housing 230 and the exhaust hood rear part 420.

[0056] [Exhaust stack] As shown in Fig. 1, exhaust pipe 500 is fixed to the front of housing 230 and is formed in the shape of a substantially rectangular cylinder that protrudes substantially horizontally forward. This exhaust pipe 500 protrudes to the front of the outer box (not shown) through a through-hole provided in the front panel of the outer box that covers the outside of water heater 1. As shown in Fig. 3, exhaust pipe 500 communicates with outlet 246 of housing 230. The combustion exhaust gas from which latent heat has been recovered in secondary heat exchanger 200 is discharged to the outside of water heater 1 through exhaust pipe 500.

[0057] [Water heater manufacturing method] The configuration of water heater 1 of this embodiment has been described above, and next, a method for manufacturing water heater 1 will be described. The method for manufacturing water heater 1 of this embodiment includes an assembly process for assembling primary heat exchanger 100 and secondary heat exchanger 200, a testing process for performing a trial run of water heater 1, and, after the testing process, a drying process for drying heat transfer tubes 211, 221 of secondary heat exchanger 200, and an application process for applying a surfactant to heat transfer tubes 211, 221 of secondary heat exchanger 200. Below, a first method for manufacturing water heater 1 and a second method for manufacturing water heater 1 will be exemplified as methods for manufacturing water heater 1 of this embodiment.

[0058] [First water heater manufacturing method] 7, the manufacturing method of the first water heater 1 includes a manufacturing process S10 for each component constituting the water heater 1, an assembly process S20 for assembling the components, a testing process S30, and a drying process S40. S10 includes a manufacturing process for primary heat exchanger 100, a manufacturing process for secondary heat exchanger 200, and a manufacturing process for other components. In the manufacturing method of the first water heater 1, the application process is performed before the assembly process S20.

[0059] The application step may be included in the manufacturing process of the secondary heat exchanger 200. In the manufacturing process of the secondary heat exchanger 200, the box portion 232, the lid portion 233, the heat transfer tubes 211, 221, the partition portion 231, the first header 265, the second header 270, etc. are first formed, and these components are sequentially assembled. The application step may be performed in the manufacturing process of the secondary heat exchanger 200, for example, before the heat transfer tubes 211, 221 are housed in the housing 230. In the application step, for example, a surfactant may be applied to the outer surfaces of the heat transfer tubes 211, 221 using a dropper or the like. As another method, the surfactant may be applied to the outer surfaces of the heat transfer tubes 211, 221 by, for example, immersing the heat transfer tubes 211, 221 in a water tank containing an aqueous solution of the surfactant.

[0060] In the assembling step S20, the various components are assembled by, for example, screwing, brazing, etc. The assembling step S20 includes a step of assembling the primary heat exchanger 100 and the secondary heat exchanger 200 together.

[0061] In the test process S30, a trial run of the water heater 1 is performed. Specifically, in the trial run of the water heater 1, combustion gas is burned in the burner device 300 and the combustion exhaust is supplied to the primary heat exchanger 100 and the secondary heat exchanger 200, and heat exchange is actually performed between the combustion exhaust and water passing through the primary heat exchanger 100 and the secondary heat exchanger 200, thereby confirming the hot water supply function of the water heater 1. Due to the trial run of the water heater 1, drain is generated in the secondary heat exchanger 200. In the test process S30, the drain hose 31 is not connected to the neutralizer 32, and is discharged outside the water heater 1.

[0062] In the testing process S30, in addition to the test operation of the water heater 1 described above, the operation and function of each installed component of the water heater 1 may be confirmed. Furthermore, the testing process S30 may be included in the final inspection before the water heater 1 is shipped.

[0063] In the drying step S40, secondary heat exchanger 200 is dried. This prevents drainage remaining in secondary heat exchanger 200 from wetting the packaging material of water heater 1 or corroding water heater 1. According to the present embodiment, since a surfactant is applied to heat transfer tubes 211, 221 of secondary heat exchanger 200, drainage is more easily discharged from secondary heat exchanger 200, and the time required for drying step S40 can be shortened.

[0064] Furthermore, in the drying step S40, vibration may be applied to the water heater 1. By applying vibration to the water heater 1, the drainage is more likely to drip from the heat transfer tubes 211, 221. Therefore, the time required for the drying step S40 can be further shortened.

[0065] In the drying step S40, hot water may be run through heat transfer pipes 211, 221 of secondary heat exchanger 200 to warm secondary heat exchanger 200. At this time, in order to prevent the generation of additional drainage, water heater 1 is not in combustion mode, and hot water prepared in advance is circulated through heat transfer pipes 211, 221. By warming secondary heat exchanger 200 in this manner, the time required for the drying step S40 can be further shortened.

[0066] In the drying step S40, air may be sent into the housing 230 of the secondary heat exchanger 200 by the fan of the water heater 1. This makes it possible to further shorten the time required for the drying step S40.

[0067] In the drying step S40, water heater 1 may be tilted to promote the discharge of drainage from secondary heat exchanger 200. This can further reduce the time required for the drying step S40.

[0068] [Second water heater manufacturing method] As shown in Figure 8, the second method of manufacturing water heater 1 includes a manufacturing process S110 for each component constituting water heater 1, an assembly process S20 for assembling each component, a testing process S130, and a drying process S40. S110 includes a manufacturing process for primary heat exchanger 100, a manufacturing process for secondary heat exchanger 200, and a manufacturing process for other components, but does not include a coating process. The assembly process S20 and the drying process S40 are each the same as those in the manufacturing method for first water heater 1. In the second method of manufacturing water heater 1, the coating process is performed after the assembly process S20.

[0069] When the application step is performed after the assembly step S20, the surfactant is applied to the heat transfer tubes 211, 221 of the secondary heat exchanger 200 from the front opening of the exhaust stack 500 through the outlet 246 of the secondary heat exchanger 200. The surfactant can be applied to the heat transfer tubes 211, 221 using, for example, a dropper. As described above, the front sides of the heat transfer tubes 211, 221 of the secondary heat exchanger 200 are connected to the water inlet pipe 12 and the return pipe 22, and therefore the front portions are particularly cold, making it easy for condensate to adhere to them. Meanwhile, the front portions of the heat transfer tubes 211, 221 are located near the outlet 246 provided on the front surface of the housing 230, and are therefore positioned such that the surfactant can be easily applied from the outlet 246, as described above. As a result, by applying the surfactant to the front portions of the heat transfer tubes 211, 221, which are particularly prone to condensate adhesion, condensate can be effectively dripped from the heat transfer tubes 211, 221.

[0070] 8, the application step may be included in the test step S130. That is, the surfactant may be applied to the heat transfer tubes 211, 221 while the water heater 1 is undergoing a test run. This allows the working time for the application step to be reduced.

[0071] [Effects of the embodiment] As described above, the manufacturing method of the first embodiment of the water heater 1 is a manufacturing method of a water heater 1 equipped with a primary heat exchanger 100 and a secondary heat exchanger 200, and includes an assembly process S20 of assembling the primary heat exchanger 100 and the secondary heat exchanger 200, a testing process S30 of performing a trial run of the water heater 1, and a drying process S40 of drying the heat transfer tubes 211, 221 of the secondary heat exchanger 200 after the testing process S30, and further includes an application process of applying a surfactant to the heat transfer tubes 211, 221 of the secondary heat exchanger 200 before the assembly process S20.

[0072] According to this manufacturing method for water heater 1, the surfactant applied to heat transfer tubes 211, 221 of secondary heat exchanger 200 reduces the surface tension of the drainage adhering to heat transfer tubes 211, 221 of secondary heat exchanger 200 in testing step S30, making it easier for the drainage to drip from heat transfer tubes 211, 221 of secondary heat exchanger 200. Therefore, the time required to dry heat transfer tubes 211, 221 of secondary heat exchanger 200 can be shortened.

[0073] Further, the second manufacturing method of the water heater 1 of this embodiment is a manufacturing method of the water heater 1 including the primary heat exchanger 100 and the secondary heat exchanger 200, and includes an assembly process S20 of assembling the primary heat exchanger 100 and the secondary heat exchanger 200, a test process S130 of performing a test run of the water heater 1, and a drying process S40 of drying the heat transfer tubes 211, 221 of the secondary heat exchanger 200 after the test process S130. The secondary heat exchanger 200 is a heat transfer The water heater 1 is provided with a housing 230 that houses pipes 211, 221 and has an exhaust port (outlet 246), and the heat transfer pipes 211, 221 are connected to supply pipes (inlet pipe 12 and return pipe 22) that supply water into the secondary heat exchanger 200 near the exhaust port, and the manufacturing method for the water heater 1 further includes, after the assembly process S20, an application process of applying a surfactant to the heat transfer pipes 211, 221 of the secondary heat exchanger 200 through the exhaust port of the secondary heat exchanger 200.

[0074] According to this manufacturing method for water heater 1, by applying a surfactant to heat transfer tubes 211, 221 of secondary heat exchanger 200, the surface tension of the drainage adhering to heat transfer tubes 211, 221 of secondary heat exchanger 200 is reduced in testing step S130, making it easier for the drainage to drip from heat transfer tubes 211, 221 of secondary heat exchanger 200. Therefore, the time required to dry heat transfer tubes 211, 221 of secondary heat exchanger 200 can be shortened. Furthermore, since the heat transfer tubes 211, 221 are connected to the supply pipe near the exhaust port, the portions of the heat transfer tubes 211, 221 that are located near the exhaust port are particularly cold and prone to generating drainage. For this reason, by applying a surfactant to the heat transfer tubes 211, 221 from the exhaust port to the vicinity of the exhaust port, drainage can be effectively caused to drip from the heat transfer tubes 211, 221.

[0075] In the second method for manufacturing water heater 1 of the present embodiment, the application step is preferably performed during the testing step S130.

[0076] According to this manufacturing method for the water heater 1, the application step is performed during the testing step S130, so that the working time for the application step can be reduced.

[0077] In the first method for manufacturing water heater 1 or the second method for manufacturing water heater 1 of the present embodiment, it is preferable to vibrate water heater 1 in drying step S40.

[0078] According to this method for manufacturing water heater 1, vibration is applied to water heater 1, which makes it easier for drainage to drip from heat transfer tubes 211, 221. Therefore, the time required for drying step S40 can be further shortened.

[0079] The water heater 1 of this embodiment is a water heater 1 including a primary heat exchanger 100 and a secondary heat exchanger 200, and heat transfer pipes 211, 221 of the secondary heat exchanger 200 are coated with a surfactant.

[0080] In such a water heater 1, the surfactant applied to the heat transfer tubes 211, 221 of the secondary heat exchanger 200 reduces the surface tension of the drain adhering to the heat transfer tubes 211, 221 of the secondary heat exchanger 200 when the water heater 1 is in use, making it easier for the drain to drip from the heat transfer tubes 211, 221 of the secondary heat exchanger 200.

[0081] <Other embodiments> (1) The method for applying the surfactant to the heat transfer tubes of the secondary heat exchanger may be different from that in the above embodiment, and may be modified as appropriate within the scope that allows the object of the present disclosure to be achieved.

[0082] (2) The application process of the present disclosure may be performed after the manufacturing process of the secondary heat exchanger is completed and before the assembly process. For example, after the secondary heat exchanger is completed, the surfactant may be applied to the heat transfer tube of the secondary heat exchanger through the exhaust port of the housing.

[0083] (3) The coating process of the present disclosure may be performed during the drying process after the assembly process. By performing the coating process during the drying process, the working time for the coating process can be reduced.

[0084] (4) In the above embodiment, the water heater 1 includes the hot water supply circuit 10 and the bath circuit 20. However, the circuit configuration of the water heater of the present disclosure may be different from this. For example, the water heater may not include a bath circuit. Also, the water heater may include a heating circuit. [Explanation of symbols]

[0085] 1: Water heater 10: Hot water supply circuit, 11: Water inlet, 12: Water inlet pipe (supply pipe), 13: Hot water outlet pipe, 14: Hot water outlet, 15: Hot water supply relay pipe, 20: Bath circuit, 21: Hot water inlet, 22: Return pipe (supply pipe), 23: Delivery pipe, 24: Hot water outlet, 31: Drain hose, 32: Neutralizer, 33: Controller, 40: Bath relay pipe 100: Primary heat exchanger, 110: Primary heat exchanger for hot water supply, 111: Heat transfer tube, 120: Primary heat exchanger for bath, 121: Heat transfer tube, 130: Boiler body, 131: Partition 200: Secondary heat exchanger, 210: Secondary heat exchanger for hot water supply, 211: Heat transfer pipe, 211A: Straight pipe section, 211B: Connection section, 220: Secondary heat exchanger for bath, 221: Heat transfer pipe, 230: Housing, 231: Partition section, 232: Box section, 233: Lid section, 245: Inlet, 246: Outlet (exhaust port), 251: Drain outlet, 265: First header, 268: Inlet section for hot water supply, 269: Inlet section for bath, 270: Second header, 273: Outlet section for hot water supply, 274: Outlet section for bath 300: Burner device, 310: Hot water supply burner group, 311: Spark plug, 312: Flame rod, 320: Bath burner group, 321: Spark plug, 322: Flame rod, 330: Burner case, 331: Partition 400: Exhaust hood, 401: Partition, 410: Exhaust hood body, 411: Mounting part, 420: Exhaust hood rear part 500: Exhaust stack B: Bathtub, P: Circulation pump

Claims

1. A method for manufacturing a water heater having a primary heat exchanger and a secondary heat exchanger, an assembling step of assembling the primary heat exchanger and the secondary heat exchanger; A test process for performing a test run of the water heater; a drying step of drying the heat transfer tube of the secondary heat exchanger after the testing step, The method for manufacturing a water heater further includes, before the assembling step, a coating step of applying a surfactant to the heat transfer tube of the secondary heat exchanger.

2. A method for manufacturing a water heater having a primary heat exchanger and a secondary heat exchanger, an assembling step of assembling the primary heat exchanger and the secondary heat exchanger; A test process for performing a test run of the water heater; a drying step of drying the heat transfer tube of the secondary heat exchanger after the testing step, the secondary heat exchanger includes a housing that houses the heat transfer tube and is provided with an exhaust port; the heat transfer tube is connected to a supply pipe that supplies water into the secondary heat exchanger near the exhaust port; The method for manufacturing a water heater further includes, after the assembly step, an application step of applying a surfactant to the heat transfer tube of the secondary heat exchanger through an exhaust port of the secondary heat exchanger.

3. The method for manufacturing a water heater according to claim 2 , wherein the coating step is performed during the testing step or the drying step.

4. The method for manufacturing a water heater according to claim 1 or 2, wherein the drying step includes vibrating the water heater.

5. A water heater comprising a primary heat exchanger and a secondary heat exchanger, The water heater, wherein a surfactant is applied to the heat transfer tube of the secondary heat exchanger.

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