Abstract: A water heater connectable to an external air supply and exhaust pipe includes a housing that houses a combustion device, a connecting portion, a first air supply and exhaust pipe, and a second air supply and exhaust pipe. The connecting portion includes an outer cylinder and an inner cylinder projecting upward from an upper surface of the housing. The first air supply and exhaust pipe and the second air supply and exhaust pipe are selectively connectable to the connecting portion. The first air supply and exhaust pipe is connectable to the connecting portion by interpolating a first air supply pipe into the outer cylinder and interpolating a first exhaust pipe into the inner cylinder, and the second air supply and exhaust pipe is connectable to the connecting portion by externally fitting a second air supply pipe onto the outer cylinder and interpolating a second exhaust pipe into the inner cylinder.

Abstract: A water heater includes a primary heat exchanger, a secondary heat exchanger disposed above the primary heat exchanger, a flow path member, and a flow restriction member. The secondary heat exchanger includes a case and heat transfer pipes arranged in the case. The case includes a wall having a gas inlet through which combustion exhaust gas discharged from the primary heat exchanger is introduced into the case. The flow path member connects the primary heat exchanger and the secondary heat exchanger and is disposed adjacent to the gas inlet and is configured to introduce the combustion exhaust gas discharged from the primary heat exchanger into the secondary heat exchanger through the gas inlet. The flow restriction member is disposed on the wall of the case to suppress upward flowing of the combustion exhaust gas that is introduced into the case through the gas inlet.

Abstract: A gas distribution unit includes a main flow passage and a plurality of distribution flow passages that branch from the main flow passage and supplies a fuel gas to each of groups of a plurality of nozzles. A main body includes a main depressed portion that forms the main flow passage, a plurality of depressed portions that form the respective distribution flow passages, and fuel gas inlets provided at upstream ends of the respective depressed portions and communicated with the main depressed portion. Among the inlets, the inlet of the depressed portion corresponding to the group including the largest number of the nozzles is formed to have a diameter larger than diameters of the inlets of the other depressed portions, and the inlet having the large diameter is formed to have a thickness in a center axis direction smaller than thicknesses of the inlets of the other depressed portions.

Abstract: A combustion device includes a solenoid valve configured to open and close an inflow port and an additional solenoid valve configured to open and close a communication port selectively mountable at an upstream end of a distribution flow passage with a small number of nozzles. When the additional solenoid valve is mounted, a state of supplying a fuel gas to only a distribution flow passage with a large number of the nozzles by opening the solenoid valve and closing the additional solenoid valve and a state of supplying the fuel gas to two distribution flow passages by opening the solenoid valve and opening the additional solenoid valve are mutually switchable. When the additional solenoid valve is not mounted, a state of supplying the fuel gas to the two distribution flow passages by opening the solenoid valve and a state of not supplying the fuel gas are mutually switchable.

Abstract: The case of the water heater is composed of a box body having a rectangular shape in front view with a front face opened and a front cover having a shallower bottom and assembled on the front face of the box body. While rear side bent parts bent inward are each formed at front ends of left and right side plates of the box body, the front side bent parts bent inward are each formed at rear ends of left and right front side plates of the front cover and are abutted on the rear side bent parts in a state of being assembled to the box body. The inner bent parts folded backward are formed at inner end parts of the front side bent parts and are positioned on inner extension lines of the rear side bent parts in an assembled state.

Abstract: A water heater connectable to an external air supply and exhaust pipe includes a housing that houses a combustion device, a connecting portion, a first air supply and exhaust pipe, and a second air supply and exhaust pipe. The connecting portion includes an outer cylinder and an inner cylinder projecting upward from an upper surface of the housing. The first air supply and exhaust pipe and the second air supply and exhaust pipe are selectively connectable to the connecting portion. The first air supply and exhaust pipe is connectable to the connecting portion by interpolating a first air supply pipe into the outer cylinder and interpolating a first exhaust pipe into the inner cylinder, and the second air supply and exhaust pipe is connectable to the connecting portion by externally fitting a second air supply pipe onto the outer cylinder and interpolating a second exhaust pipe into the inner cylinder.

Abstract: A water heater includes a primary heat exchanger, a secondary heat exchanger disposed above the primary heat exchanger, a flow path member, and a flow restriction member. The secondary heat exchanger includes a case and heat transfer pipes arranged in the case. The case includes a wall having a gas inlet through which combustion exhaust gas discharged from the primary heat exchanger is introduced into the case. The flow path member connects the primary heat exchanger and the secondary heat exchanger and is disposed adjacent to the gas inlet and is configured to introduce the combustion exhaust gas discharged from the primary heat exchanger into the secondary heat exchanger through the gas inlet. The flow restriction member is disposed on the wall of the case to suppress upward flowing of the combustion exhaust gas that is introduced into the case through the gas inlet.

Abstract: The case of the water heater is composed of a box body having a rectangular shape in front view with a front face opened and a front cover having a shallower bottom and assembled on the front face of the box body. While rear side bent parts bent inward are each formed at front ends of left and right side plates of the box body, the front side bent parts bent inward are each formed at rear ends of left and right front side plates of the front cover and are abutted on the rear side bent parts in a state of being assembled to the box body. The inner bent parts folded backward are formed at inner end parts of the front side bent parts and are positioned on inner extension lines of the rear side bent parts in an assembled state.