Hot water apparatus

Abstract

A hot water apparatus includes a burner, a sensible heat recovery heat exchanger, and an ignition plug. The sensible heat recovery heat exchanger includes a case. The ignition plug includes an insulator portion and two electrodes. The insulator portion includes a base end portion and a tip end portion. The tip end portion includes a tip end surface and a groove portion. The tip end surface is arranged opposite to the base end portion. The groove portion is recessed from the tip end surface toward the base end portion. The groove portion is arranged between the two electrodes and provided across top and bottom ends of the tip end portion. The groove portion has a lateral width decreasing from the top end toward the bottom end of the tip end portion.

What is claimed is: 
     
         1 . A hot water apparatus comprising:
 a burner which generates a combustion gas for heating;   a heat exchanger which is provided below the burner and heats water and/or hot water with the combustion gas; and   an ignition plug which ignites the burner,   the heat exchanger including a case having a wall surface serving as a partition between inside and outside,   the ignition plug including an insulator portion attached to the wall surface of the case and two electrodes extending from the inside to the outside of the case through respective insulator portions and arranged at a distance from each other in a lateral direction,   the insulator portion including a base end portion attached to the wall surface of the case and a tip end portion protruding from the base end portion toward a side opposite to the wall surface,   the tip end portion having a tip end surface arranged opposite to the base end portion and a groove portion recessed from the tip end surface toward the base end portion,   the groove portion being arranged between the two electrodes and provided across top and bottom ends of the tip end portion, and   the groove portion having a lateral width decreasing from the top end toward the bottom end of the tip end portion.   
     
     
         2 . The hot water apparatus according to  claim 1 , wherein
 the groove portion has a width increasing from the base end portion toward the tip end surface.   
     
     
         3 . The hot water apparatus according to  claim 1 , wherein
 the tip end portion includes a first end portion arranged on a first side of the groove portion and a second end portion arranged on a second side of the groove portion,   the first end portion has a down grade decreasing in height on a side away from the second end portion, and   the second end portion has a down grade decreasing in height on a side away from the first end portion.   
     
     
         4 . The hot water apparatus according to  claim 1 , wherein
 the groove portion includes an inclined wall portion provided at the top end of the tip end portion, and   the inclined wall portion has a down grade decreasing in height two-dimensionally from the top end toward the bottom end of the tip end portion.   
     
     
         5 . The hot water apparatus according to  claim 4 , wherein
 the inclined wall portion is provided to surround the electrode in a circumferential direction of the electrode and to define a tangent of a virtual circle where the electrode is located in a center.   
     
     
         6 . The hot water apparatus according to  claim 1 , wherein
 the groove portion includes an inclined wall portion provided at the top end of the tip end portion, and   the inclined wall portion has a down grade decreasing in height in a curved manner from the top end toward the bottom end of the tip end portion.   
     
     
         7 . The hot water apparatus according to  claim 1 , wherein
 the tip end portion includes two cylindrical portions,   the two electrodes are inserted in the two cylindrical portions, respectively, in an axial direction of the cylindrical portion, and   the groove portion is arranged between the two cylindrical portions.   
     
     
         8 . The hot water apparatus according to  claim 7 , wherein
 the tip end portion includes a connection wall arranged between the two cylindrical portions,   each of the two cylindrical portions protrudes from the base end portion relative to the connection wall toward a side away from the wall surface, and   a top end of the connection wall has a down grade decreasing in height from the base end portion toward the side away from the wall surface.   
     
     
         9 . The hot water apparatus according to  claim 1 , wherein
 the tip end portion protrudes from the base end portion toward the inside of the case, and   the groove portion is arranged in the inside of the case.   
     
     
         10 . The hot water apparatus according to  claim 1 , wherein
 the tip end portion protrudes from the base end portion toward the outside of the case, and   the groove portion is arranged outside the case.   
     
     
         11 . The hot water apparatus according to  claim 1 , wherein
 the tip end portion protrudes from the base end portion toward both of the inside and the outside of the case,   the groove portion is arranged in both of the inside and the outside of the case, and   the groove portion arranged in the inside of the case is greater in depth than the groove portion arranged outside the case.