Patent Publication Number: US-2023139779-A1

Title: Combustion device

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
     This application claims priority to Japanese Patent Application No. 2021-179367, filed on Nov. 2, 2021, the entire contents of which are incorporated herein by reference. 
     TECHNICAL FIELD 
     The disclosure herein relates to combustion devices. 
     BACKGROUND 
     Japanese Patent Application No. 2018-84379 describes a combustion device including a casing having a bottom plate, a combustion unit housed in the casing, and a fan housed in the casing and configured to take in air inside the casing and supply the air to the combustion unit. The bottom plate is provided with a flat portion and a recess recessed downward from the flat portion. The recess is provided with a drainage hole. The drainage hole is located below an upper surface of the flat portion. 
     SUMMARY 
     In combustion devices including a fan configured to take in air inside a casing, such as the one described in Japanese Patent Application No. 2018-84379, rainwater, etc. may be suctioned into the casing through the drainage hole due to a negative pressure generated by the fan. In this instance, the rainwater, etc. suctioned through the drainage hole may spatter and adhere to components in the casing. The disclosure herein provides a technology that suppresses rainwater, etc. suctioned through a drainage hole from adhering to components in a casing in a combustion device comprising a fan configured to take in air inside the casing. 
     A combustion device disclosed herein may comprise a casing comprising a bottom plate, a combustion unit housed in the casing, and a fan housed in the casing and configured to take in air inside the casing and supply the air to the combustion unit. The bottom plate may be provided with a flat portion and a recess recessed downward from the flat portion. The recess may be provided with a drainage hole and an eave arranged above the drainage hole. The drainage hole may be located below an upper surface of the flat portion. The eave may be at least partially located below the upper surface of the flat portion. 
     Since the drainage hole is provided in the bottom plate of the casing, most of components in the casing are typically located above the drainage hole. Thus, when rainwater, etc. suctioned through the drainage hole spatters upward, the rainwater, etc. may adhere to the components in the casing. According to the configuration above, the eave is arranged above the drainage hole. Thus, even when the rainwater, etc. is suctioned into the casing through the drainage hole, the eave suppresses the rainwater, etc. from spattering upward from the drainage hole. The configuration above can thus suppress the rainwater, etc. suctioned through the drainage hole from adhering to the components in the casing in the combustion device comprising the fan configured to take in air inside the casing. Locating the entirety of such an eave above the upper surface of the flat portion requires a size of the casing to be increased in order to avoid interference of the eave with the components in the casing. According to the configuration above, the eave is at least partially located below the upper surface of the flat portion, and thus the size of the casing can be reduced as compared with a configuration in which the entirety of the eave is located above the upper surface of the flat portion. 
     In one or more embodiments, the drainage hole and the eave may be formed by cutting a part of the recess and bending the part inward. In the disclosure herein, “inside/inward” means the inside of the casing/toward the inside of the casing, and “outside/outward” means the outside of the casing/toward the outside of the casing. 
     For example, if the drainage hole and the eave are formed separately in the casing, this may result in an increase in manufacturing cost of the casing. According to the configuration above, the drainage hole and the eave can be formed simultaneously by cutting a part of the bottom plate of the casing and bending the part. The configuration above can reduce the manufacturing cost of the casing including the drainage hole and the eave. 
     In one or more embodiments, the drainage hole and the eave may be formed by cutting a part of the recess and performing inward drawing to the part. 
     According to the configuration above, the drainage hole and the eave can be formed simultaneously by cutting a part of the bottom plate of the casing and performing drawing to the part, and thus manufacturing cost of the casing including the drainage hole and the eave can be reduced. Further, according to the configuration above, an inflow direction of air through the drainage hole is rectified to a direction along the bottom plate by the eave formed as above. According to the configuration above, rainwater, etc. suctioned into the casing through the drainage hole is likely to be guided in the direction along the bottom plate, and thus upward spattering of the rainwater, etc. from the drainage hole can be suppressed more effectively. 
     In one or more embodiments, the recess may comprise a first plate inclined with respect to the flat portion. The drainage hole may be defined in the first plate. 
     According to the configuration above, rainwater, etc. is suctioned into the casing through the drainage hole in a direction inclined with respect to an up-direction. Thus, upward spattering of the rainwater, etc. from the drainage hole can be suppressed more effectively. The configuration above can more effectively suppress the rainwater, etc. suctioned through the drainage hole from adhering to the components in the casing in the combustion device comprising the fan configured to take in air inside the casing. 
     In one or more embodiments, the eave may be connected to an upper portion of a peripheral edge of the drainage hole. 
     According to the configuration above, when rainwater, etc. is suctioned into the casing through the drainage hole, the eave can more suitably suppress upward spattering of the rainwater, etc. from the drainage hole. The configuration above can thus more effectively suppress the rainwater, etc. suctioned through the drainage hole from adhering to the components in the casing in the combustion device comprising the fan configured to take in air inside the casing. 
     In one or more embodiments, the recess may further comprise a second plate that is inclined with respect to the flat portion and arranged to face the first plate in a direction along the flat portion. 
     According to the configuration above, when rainwater, etc. is suctioned into the casing through the drainage hole, upward spattering of the rainwater, etc. from the drainage hole can be suppressed by the eave and also spattering of the rainwater, etc. in the direction along the flat portion can be suppressed by the second plate. The configuration above can thus more effectively suppress the rainwater, etc. suctioned through the drainage hole from adhering to the components in the casing in the combustion device comprising the fan configured to take in air inside the casing. 
    
    
     
       BRIEF DESCRIPTION OF DRAWINGS 
         FIG.  1    is a perspective view of the entire water heater  2  according to an embodiment, as viewed from the upper front left side. 
         FIG.  2    is a perspective view of the entire water heater  2  according to the embodiment, as viewed from the lower rear right side. 
         FIG.  3    is a diagram illustrating components housed in a casing  10  of the water heater  2  according to the embodiment. 
         FIG.  4    is a perspective view of a bottom plate  20  constituting the casing  10  of the water heater  2  according to the embodiment, as viewed from the upper front left side. 
         FIG.  5    is a perspective view of a first recess  240   a  provided in the bottom plate  20  constituting the casing  10  of the water heater  2  according to the embodiment, as viewed from the upper rear left side. 
         FIG.  6    is a diagram illustrating the first recess  240   a  provided in the bottom plate  20  constituting the casing  10  of the water heater  2  according to the embodiment, as viewed from below. 
         FIG.  7    is a cross-sectional view of the first recess  240   a  provided in the bottom plate  20  constituting the casing  10  of the water heater  2  according to the embodiment, taken along a line D-D in  FIG.  6   . 
         FIG.  8    is a perspective view of a drainage hole  282   a  and an eave  284   a  provided in a first plate  242   a  of a first recess  240   a  of a water heater  2  according to a variant, as viewed from the upper front left side. 
     
    
    
     DETAILED DESCRIPTION 
     Embodiments 
     A water heater  2  according to an embodiment illustrated in  FIG.  1    is placed outdoors for use. The water heater  2  comprises a casing  10 . The casing  10  comprises a front plate  12 , a rear plate  14  (see  FIG.  2   ), a right plate  16  (see  FIG.  2   ), a left plate  18 , a bottom plate  20  (see  FIG.  2   ), and a top plate  22 . The right plate  16 , the left plate  18 , and the top plate  22  are integral with each other. An exhaust outlet  122  for discharging exhaust gas generated in a combustion unit  50 , which will be described later, is provided in an upper portion of the front plate  12 . An air inlet  124  for taking outside air into the casing  10  is provided in a lower portion of the front plate  12 . 
     As illustrated in  FIG.  2   , the rear plate  14  and the bottom plate  20  are integrated with each other. Attached to the bottom plate  20  are a water supply connecting port  70  for connection of a water supply means for water supply to the water heater  2 , a hot water supply connecting port  72  for connection of a hot water supply means for hot water supply from the water heater  2 , and a gas supply connecting port  74  for connection of a gas supply means for fuel gas supply to the water heater  2 . 
     As illustrated in  FIG.  3   , the casing  10  houses a controller  30 , a fan  40 , the combustion unit  50 , an exhaust duct  60 , a water supply pipe WP 1 , a hot water supply pipe WP 2 , and a gas supply pipe GP. 
     The controller  30  is attached to the left plate  18  in a lower portion of the casing  10 . The controller  30  controls operations of the fan  40 , the combustion unit  50 , and other components of the water heater  2 . 
     The fan  40  is located in a central portion of the casing  10 . The fan  40  includes an air intake (not illustrated) that is open inside the casing  10 . The fan  40  is connected to the combustion unit  50 . While the fan  40  is in operation, air inside the casing  10  is taken into the air intake of the fan  40  and supplied to the combustion unit  50 . 
     The combustion unit  50  is located above the fan  40 . The combustion unit  50  comprises a gas burner  52  and a heat exchanger  54 . In the combustion unit  50 , the heat exchanger  54  is located above the gas burner  52 . The gas burner  52  is connected to the gas supply connecting port  74  via the gas supply pipe GP. The gas burner  52  combusts fuel gas supplied through the gas supply pipe GP by using the air supplied from the fan  40 , thereby generating combustion gas. The heat exchanger  54  heats water flowing through a water pipe (not illustrated) in the heat exchanger  54  by the combustion gas generated by the combustion in the gas burner  52 . One end of the water pipe in the heat exchanger  54  is connected to the water supply connecting port  70  via the water supply pipe WP 1 . The other end of the water pipe in the heat exchanger  54  is connected to the hot water supply connecting port  72  via the hot water supply pipe WP 2 . Thus, water supplied to the water heater  2  is heated by the heat exchanger  54  and is then supplied as hot water. 
     The exhaust duct  60  is located above the combustion unit  50 . The exhaust duct  60  is connected to the exhaust outlet  122  of the front plate  12  (see  FIG.  1   ) and discharges the combustion gas generated in the combustion unit  50 . That is, the combustion gas in the gas burner  52  passes the heat exchanger  54  and is discharged to the outside from the exhaust duct  60 . 
     Configuration of Bottom Plate  20   
     As illustrated in  FIG.  4   , the bottom plate  20  comprises a flat portion  202 , a first projection  210 , a second projection  220 , a third projection  230 , a first recess  240   a , and a second recess  240   b . The flat portion  202  has a plate shape expanding in an up-down direction and a right-left direction. The first projection  210 , the second projection  220 , and the third projection  230  project upward from the flat portion  202 . The first projection  210  includes a first mounting hole  212  for attachment of the hot water supply connecting port  72 . The second projection  220  includes a second mounting hole  222  for attachment of the water supply connecting port  70 . The third projection  230  includes a third mounting hole  232  for attachment of the gas supply connecting port  74 . The hot water supply connecting port  72  is attached such that it seals an interspace between the hot water supply connecting port  72  and the first mounting hole  212 . The water supply connecting port  70  is attached such that it seals an interspace between the water supply connecting port  70  and the second mounting hole  222 . The gas supply connecting port  74  is attached such that it seals an interspace between the gas supply connecting port  74  and the third mounting hole  232 . Thus, rainwater, etc. is prevented from entering the inside of the casing  10  through the first mounting hole  212 , the second mounting hole  222 , and the third mounting hole  232 . 
     The first recess  240   a  is provided in a front left portion of the bottom plate  20 . The second recess  240   b  is provided in a front right portion of the bottom plate  20 . The first recess  240   a  and the second recess  240   b  are recessed downward with respect to the flat portion  202 . Thus, rainwater, etc. that entered the casing  10  is guided to the first recess  240   a  and/or the second recess  240   b . In the present embodiment, the first recess  240   a  and the second recess  240   b  have mirror symmetry shapes. Thus, it should be understood that the following description on the first recess  240   a  can be applied to the second recess  240   b.    
     As illustrated in  FIG.  5   , the first recess  240   a  comprises a first plate  242   a , a second plate  244   a , a first connecting portion  246   a , a second connecting portion  248   a , and a third connecting portion  250   a . The first plate  242   a  is located in a rear portion of the first recess  240   a . The second plate  244   a  is located in a front portion of the first recess  240   a . The first plate  242   a  and the second plate  244   a  are arranged to face each other in a front-rear direction. The first connecting portion  246   a  smoothly connects a lower end of the first plate  242   a  to a lower end of the second plate  244   a . The second connecting portion  248   a  smoothly connects a right end of the first plate  242   a  to a right end of the second plate  244   a . The third connecting portion  250   a  smoothly connects a left end of the first plate  242   a  to a left end of the second plate  244   a . A drainage hole  262   a  and an eave  264   a  are provided at the first plate  242   a . The drainage hole  262   a  and the eave  264   a  are formed by cutting a part of the first plate  242   a  and bending the part inward (which may be termed “cut-bend process” hereinafter). An extruded tap hole  266   a  is provided in the second plate  244   a.    
     As illustrated in  FIG.  6   , the bottom plate  20  and the front plate  12  are coupled to each other with a screw member  400   a . The screw member  400   a  couples the bottom plate  20  to the front plate  12  by being screwed in the extruded tap hole  266   a  (see  FIG.  5   ) from the outside. The centers of the drainage hole  262   a  and the eave  264   a  in the right-left direction are offset leftward with respect to the centers of the extruded tap hole  266   a  and the screw member  400   a  in the right-left direction. A folding line L 2  on the first plate  242   a  in the cut-bend process is along the right-left direction. The cut-bend process is performed such that a part of the first plate  242   a  that is located forward of the folding line L 2  is cut and bent. The drainage hole  262   a  has a trapezoidal shape that is symmetrical in the right-left direction. A width of the drainage hole  262   a  in the right-left direction is decreased forward. In the present embodiment, a length of the folding line L 2  in the right-left direction is 6 mm. A width w 1  of a front portion of the drainage hole  262   a  in the right-left direction is 4 mm. 
     As illustrated in  FIG.  7   , the first plate  242   a  is inclined downward and forward with respect to the flat portion  202 , substantially at a constant inclination angle. The inclination angle of the first plate  242   a  with respect to the flat portion  202  is in a range from 30 degrees to 45 degrees. The second plate  244   a  is inclined downward and rearward with respect to the flat portion  202 , substantially at a constant inclination angle. The inclination angle of the second plate  244   a  with respect to the flat portion  202  is in a range from 60 degrees to 70 degrees. The first connecting portion  246   a  is curved such that a central portion of the first connecting portion  246   a  is below an end portion thereof. 
     The entirety of the drainage hole  262   a  and the entirety of the eave  264   a  are located below an upper surface of the flat portion  202 . The drainage hole  262   a  extends downward and forward from a base end portion  302   a  of the eave  264   a . That is, the base end portion  302   a  of the eave  264   a  is connected to an upper rear portion of a peripheral edge of the drainage hole  262   a . A bending angle of the base end portion  302   a  with respect to the first plate  242   a  at the folding line L 2  is in a range from 20 degrees to 60 degrees. The eave  264   a  is curved such that parts of the eave  264   a  that are closer to a distal end portion  304   a  have smaller inclination angles with respect to the first plate  242   a . The distal end portion  304   a  of the eave  264   a  extends forward beyond a lower front portion of the peripheral edge of the drainage hole  262   a . In the present embodiment, a width w 2  of the drainage hole  262   a  in the inclination direction of the first plate  242   a  is 10 mm. The maximum depth d of the first recess  240   a  in the up-down direction is 10 mm. 
     In the water heater  2  according to the present embodiment, rainwater, etc. may be suctioned into the inside through the drainage hole  262   a  due to a negative pressure generated by the fan  40  in the casing  10 . In this instance, although the rainwater, etc. flows in fast through the drainage hole  262   a  due to the negative pressure, the upward momentum of the rainwater, etc. is reduced by the eave  264   a  expanding in the front-rear direction and the right-left direction above the drainage hole  262   a . Further, since the base end portion  302   a  of the eave  264   a  is sufficiently bent with respect to the first plate  242   a , the eave  264   a  does not prevent the rainwater, etc. from flowing out through the drainage hole  262   a . As above, the eave  264   a  suppresses upward spattering of rainwater, etc. suctioned through the drainage hole  262   a , while maintaining the drainage performance of the drainage hole  262   a.    
     The screw member  400   a  couples the front plate  12  to the bottom plate  20  by being screwed in the extruded tap hole  266   a  with the screw member  400   a  inserted in a hole (not illustrated) provided in the front plate  12 . In the state where the screw member  400   a  is screwed in the extruded tap hole  266   a , a tip  402   a  of the screw member  400   a  is located below the upper surface of the flat portion  202 . 
     With such a screw member  400   a , if the tip  402   a  of the screw member  400   a  is located above the upper surface of the flat portion  202 , an increased size of the casing  10  is required to avoid interference of the screw member  400   a  with the components in the casing  10 . In the present embodiment, the tip  402   a  of the screw member  400   a  is located below the upper surface of the flat portion  202 . Thus, the size of the casing  10  is reduced as compared with a configuration in which the tip  402   a  is located above the upper surface of the flat portion  202 . 
     Variants 
     In the embodiment above, the water heater  2 , which heats water supplied from an external and supplies the resulting hot water, is described as an example of combustion device. In another embodiment, the combustion device may be another combustion device other than the water heater  2 . For example, the combustion device may be a heating device that heats and circulates heating water, or the like. For example, the heating water may be antifreeze liquid. 
     In the embodiment above, the fan  40  is located in the central portion of the casing  10 . Unlike this, the fan  40  may not be located in the central portion of the casing  10 . For example, the fan  40  may be located in an upper portion or the lower portion of the casing  10 . 
     In the embodiment above, the fan  40  is connected to the combustion unit  50 , and air inside the casing  10  is taken into the air intake of the fan  40  and supplied to the combustion unit  50  while the fan  40  is in operation. In another embodiment, the fan  40  may be located between the combustion unit  50  and the exhaust duct  60  and connected to each of the combustion unit  50  and the exhaust duct  60 . In this instance, the combustion unit  50  may include an air intake. In this instance, while the fan  40  is in operation, the air inside the casing  10  may be taken into the air intake of the combustion unit  50  and the combustion gas from the combustion unit  50  may flow through the fan  40  and the exhaust duct  60  and be discharged from the exhaust outlet  122  of the front plate  12  to the outside of the water heater  2 . 
     In the embodiment above, the first recess  240   a  is provided in a front portion of the bottom plate  20 , the first recess  240   a  includes the extruded tap hole  266   a , and the front plate  12  is coupled to the first recess  240   a  of the bottom plate  20  by the screw member  400   a  being screwed in the extruded tap hole  266   a . Unlike this, the first recess  240   a  may not be provided in the front portion of the bottom plate  20 . For example, the first recess  240   a  may be provided in a rear portion of the bottom plate  20 . The first recess  240   a  may not include the extruded tap hole  266   a . In this instance, the front plate  12  may be coupled to a portion of the bottom plate  20  other than the first recess  240   a.    
     In the embodiment above, regarding the first plate  242   a , the entirety of the eave  264   a  is located below the upper surface of the flat portion  202 . In another embodiment, a part of the eave  264   a  may be located above the upper surface of the flat portion  202  and the remaining part of the eave  264   a  may be located below the upper surface of the flat portion  202 . 
     In the embodiment above, the drainage hole  262   a  and the eave  264   a  are provided at the first plate  242   a . In another embodiment, the drainage hole  262   a  and the eave  264   a  may be provided at the second plate  244   a . In yet another embodiment, the first recess  240   a  may comprise a flat portion connecting the lower end of the first plate  242   a  to the lower end of the second plate  244   a  instead of the first connecting portion  246   a , and the drainage hole  262   a  and the eave  264   a  may be provided at the flat portion of the first recess  240   a.    
     In the embodiment above, the folding line L 2  of the cut-bend process is along the right-left direction and the cut-bend process is performed such that the portion located forward of the folding line L 2  is cut and bent. Unlike this, the folding line L 2  of the cut-bend process may not be along the right-left direction and the cut-bend process may not be performed such that the portion located forward of the folding line L 2  is cut and bent. For example, the folding line L 2  of the cut-bend process may be along the front-rear direction and the cut-bend process may be performed such that a portion located leftward of the folding line L 2  is cut and bent. 
     In the embodiment above, the drainage hole  262   a  and the eave  264   a  are formed by performing the cut-bend process to the first plate  242   a . In another embodiment, the drainage hole  262   a  and the eave  264   a  may be formed separately. For example, the drainage hole  262   a  may be formed by performing punching to the first plate  242   a , and the eave  264   a , which was formed as a separate component, may be welded to the peripheral edge of the drainage hole  262   a.    
     In yet another embodiment, as illustrated in  FIG.  8   , a drainage hole  282   a  and an eave  284   a  may be provided at the first plate  242   a  instead of the drainage hole  262   a  and the eave  264   a . The drainage hole  282   a  and the eave  284   a  may be formed by cutting a part of the first plate  242   a  and performing inward drawing to the part (which may be termed “cut-drawing process” hereinafter). The eave  284   a  has a shape formed by drawing. An opening S 2  is defined by a portion of a peripheral edge of the drainage hole  282   a  that is not connected to a base end portion  322   a  of the eave  284   a  and a distal end portion  324   a  of the eave  284   a . The opening S 2  is open in a direction along the first plate  242   a . Thus, an inflow direction of air through the drainage hole  282   a  is rectified to the direction along the first plate  242   a  by the eave  284   a . Accordingly, even when rainwater, etc. is suctioned to the inside through the drainage hole  282   a  due to the negative pressure generated by the fan  40  in the casing  10 , the rainwater, etc. is guided downward along the first plate  242   a , and thus upward spattering of the rainwater, etc. from the drainage hole  282   a  can be suppressed. 
     Corresponding Relationships 
     As described, in one or more embodiments, the water heater  2  (an example of combustion device) comprises the casing  10  comprising the bottom plate  20 , the combustion unit  50  housed in the casing  10 , and the fan  40  housed in the casing  10  and configured to take in air inside the casing  10  and supply the air to the combustion unit  50 . The bottom plate  20  is provided with the flat portion  202  and the first recess  240   a  recessed downward from the flat portion  202 . The first recess  240   a  is provided with the drainage hole  262   a  (or the drainage hole  282   a ) and the eave  264   a  (or the eave  284   a ) arranged above the drainage hole  262   a  (or the drainage hole  282   a ). The drainage hole  262   a  (or the drainage hole  282   a ) is located below the upper surface of the flat portion  202 . The eave  264   a  (or the eave  284   a ) is at least partially located below the upper surface of the flat portion  202 . 
     Since the drainage hole  262   a  (or the drainage hole  282   a ) is typically provided in the bottom plate  20  of the casing  10 , most of components in the casing  10 , such as the controller  30 , the fan  40 , the combustion unit  50 , the exhaust duct  60 , the water supply pipe WP 1 , the hot water supply pipe WP 2 , and the gas supply pipe GP, are located above the drainage hole  262   a  (or the drainage hole  282   a ). According to the configuration above, the eave  264   a  (or the eave  284   a ) is arranged above the drainage hole  262   a  (or the drainage hole  282   a ). Thus, even when rainwater, etc. is suctioned into the casing  10  through the drainage hole  262   a  (or the drainage hole  282   a ), the eave  264   a  (or the eave  284   a ) suppresses the rainwater, etc. from spattering upward from the drainage hole  262   a  (or the drainage hole  282   a ). The configuration above can suppress the rainwater, etc. suctioned through the drainage hole  262   a  (or the drainage hole  282   a ) from adhering to the components in the casing  10  in the water heater  2  comprising the fan  40  configured to take in air inside the casing  10 . For the arrangement of such an eave  264   a  (or the eave  284   a ), locating the entirety of the eave  264   a  (or the eave  284   a ) above the upper surface of the flat portion  202  requires an increased size of the casing  10  to avoid interference of the eave  264   a  (or the eave  284   a ) with the components in the casing  10 . According to the configuration above, the eave  264   a  (or the eave  284   a ) is at least partially located below the upper surface of the flat portion  202 , and thus the size of the casing  10  can be reduced as compared with a configuration in which the entirety of the eave  264   a  (or the eave  284   a ) is located above the upper surface of the flat portion  202 . 
     In one or more embodiments, the drainage hole  262   a  and the eave  264   a  are formed by cutting a part of the first recess  240   a  and bending the part inward (i.e., by the cut-bend process). 
     For example, if the drainage hole  262   a  and the eave  264   a  are formed separately in the casing  10 , this may result in an increase in manufacturing cost of the casing  10 . According to the configuration above, the drainage hole  262   a  and the eave  264   a  can be formed simultaneously by performing the cut-bend process to the bottom plate  20  of the casing  10 . The configuration above can reduce the manufacturing cost of the casing  10  including the drainage hole  262   a  and the eave  264   a . 
     In one or more embodiments, the drainage hole  282   a  and the eave  284   a  are formed by cutting a part of the first recess  240   a  and performing inward drawing to the part (i.e., by the cut-drawing process). 
     According to the configuration above, the drainage hole  282   a  and the eave  284   a  can be formed simultaneously by performing the cut-drawing process to the bottom plate  20  of the casing  10 , and thus the configuration can reduce the manufacturing cost of the casing  10  including the drainage hole  282   a  and the eave  284   a . Further, according to the configuration above, the inflow direction of air through the drainage hole  282   a  is rectified to the direction along the first plate  242   a  (an example of bottom plate) by the eave  284   a  formed by the cut-drawing process. According to the configuration above, rainwater, etc. suctioned into the casing  10  through the drainage hole  282   a  is likely to be guided in the direction along the first plate  242   a , and thus upward spattering of the rainwater, etc. from the drainage hole  282   a  can be suppressed more effectively. The configuration above can thus more effectively suppress the rainwater, etc. suctioned through the drainage hole  282   a  from adhering to the components within the casing  10  in the water heater  2  comprising the fan  40  configured to take in air inside the casing  10 . 
     In one or more embodiments, the first recess  240   a  comprises the first plate  242   a  inclined with respect to the flat portion  202 . The drainage hole  262   a  (or the drainage hole  282   a ) is provided in the first plate  242   a . 
     According to the configuration above, rainwater, etc. is suctioned into the casing  10  through the drainage hole  262   a  (or the drainage hole  282   a ) in a direction inclined with respect to an up-direction. Thus, upward spattering of the rainwater, etc. from the drainage hole  262   a  (or the drainage hole  282   a ) can be suppressed more effectively. The configuration above can thus more effectively suppress the rainwater, etc. suctioned through the drainage hole  262   a  (or the drainage hole  282   a ) from adhering to the components in the casing  10  in the water heater  2  comprising the fan  40  configured to take in air inside the casing  10 . 
     In one or more embodiments, the eave  264   a  (or the eave  284   a ) is connected to the upper portion of the peripheral edge of the drainage hole  262   a  (or the drainage hole  282   a ). 
     According to the configuration above, when rainwater, etc. is suctioned into the casing  10  through the drainage hole  262   a  (or the drainage hole  282   a ), the eave  264   a  (or the eave  284   a ) can more effectively suppress upward spattering of the rainwater, etc. from the drainage hole  262   a  (or the drainage hole  282   a ). The configuration above can thus more effectively suppress the rainwater, etc. suctioned through the drainage hole  262   a  (or the drainage hole  282   a ) from adhering to the components in the casing  10  in the water heater  2  comprising the fan  40  configured to take in air inside the casing  10 . 
     In one or more embodiments, the first recess  240   a  further comprises the second plate  244   a  that is inclined with respect to the flat portion  202  and arranged to face the first plate  242   a  in the direction along the flat portion  202 . 
     According to the configuration above, when rainwater, etc. is suctioned into the casing  10  through the drainage hole  262   a  (or the drainage hole  282   a ), upward spattering of the rainwater, etc. from the drainage hole  262   a  (or the drainage hole  282   a ) can be suppressed by the eave  264   a  (or the eave  284   a ) and also spattering of the rainwater, etc. in the direction along the flat portion  202  can be suppressed by the second plate  244   a . The configuration above can more effectively suppress the rainwater, etc. suctioned through the drainage hole  262   a  (or the drainage hole  282   a ) from adhering to the components within the casing  10  in the water heater  2  comprising the fan  40  configured to take in air inside the casing  10 . 
     Specific examples of the present invention have been described in detail, however, these are mere exemplary indications and thus do not limit the scope of the claims. The art described in the claims includes modifications and variations of the specific examples presented above. Technical features described in the description and the drawings may technically be useful alone or in various combinations, and are not limited to the combinations as originally claimed. Further, the art described in the description and the drawings may concurrently achieve a plurality of aims, and technical significance thereof resides in achieving any one of such aims.