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 mounting structure for mounting a case to a mounting surface via a support fitting component that is fixed to the mounting surface in a vertical direction. The case houses a burning device. On a back plate of the case, a lock-engagement fitting component is mounted. The lock-engagement fitting component has an upper plate portion and a lower plate portion. The upper plate portion is fixed to the back plate, and the lower plate portion is lock-engageable with the support fitting component from above and has a dimension longer than the support fitting component in the left-right direction. The lower plate portion is lock-engaged with the support fitting component from above to hang and support the case through the lock-engagement fitting component by the support fitting component.

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 heat exchanger includes a case, fins, and heat transfer tubes. Combustion exhaust gas passes downward in the case. The fins are disposed at a lower portion of the case and arranged in the first direction. Each of the fins includes a first end and a second end that is an opposite end from the first end in a second direction intersecting the first direction. Each of the fins includes through holes in which the heat transfer tubes are inserted. Each of the fins includes heat receiving portions arranged in the second direction and connecting portion connecting the heat receiving portions. The heat receiving portions include a first heat receiving portion disposed at the first end. The first heat receiving portion includes a first recessed portion recessed from an outer edge of an upper part of the first heat receiving portion.

Abstract: An object is to provide a water heater mounting structure for mounting a case to a mounting surface via a support fitting component that is fixed to the mounting surface in a vertical direction. The case houses a burning device. On a back plate of the case, a lock-engagement fitting component is mounted. The lock-engagement fitting component has an upper plate portion and a lower plate portion. The upper plate portion is fixed to the back plate, and the lower plate portion is lock-engageable with the support fitting component from thereabove and has a dimension longer than the support fitting component in the left-right direction. The lower plate portion is lock-engaged with the support fitting component from thereabove to hang and support the case through the lock-engagement fitting component by the support fitting component.

Abstract: A secondary heat exchanger includes a case and a first heat transfer tube portion. The case includes a box body and a first closing member. The box body is provided with a second opening on one side in a third direction. A first assembly in which the first heat transfer tube portion and the first closing member are assembled integrally is mounted to the box body so that a plurality of first heat transfer tubes are is inserted into the box body from the second opening and so that the second opening is closed by the first closing member.

Abstract: The premixing device includes a first and a second venturi having a pressure reducing portion for air, and a gas supply passage for supplying fuel gas to the venturis, and generates air-fuel mixture by mixing fuel gas with air flowing in the venturi by using a fan and supplies the air-fuel mixture to a burner. A first and a second nozzles for reducing pressure of fuel gas are disposed in the gas supply passage, and the first and the second nozzles are formed in the same nozzle shape as the pressure reducing portion of the first and the second venturis.

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 premixing device includes a first and a second venturi in which air flows by rotation of a centrifugal fan, first and second communication openings disposed in the venturis, respectively, for allowing fuel gas supplied from a gas supply passage to flow out, a flap valve capable of opening and closing the second venturi on a side downstream of the second communication opening, and an equalizing valve disposed in the gas supply passage on a side upstream of the first and the second communication openings. The gas supply passage, which connects between an outlet of the equalizing valve and the first and the second communication openings, diverges from the outlet of the equalizing valve to independently form a first gas passage and a first straight path, and a second gas passage and a second straight path for the venturis, respectively.

Abstract: A secondary heat exchanger includes a case and a first heat transfer tube portion. The case includes a box body and a first closing member. The box body is provided with a second opening on one side in a third direction. A first assembly in which the first heat transfer tube portion and the first closing member are assembled integrally is mounted to the box body so that a plurality of first heat transfer tubes are is inserted into the box body from the second opening and so that the second opening is closed by the first closing member.

Abstract: A water heater includes a plurality of stages of burners, a water supply pipe, a hot water outlet pipe, a heat exchanger, a passing water quantity control unit, a temperature detection unit, and an operation control unit. The operation control unit, upon confirmation that a predetermined start condition of a passing water restriction is satisfied at a start of a hot water supply, performs the output hot water temperature control by calculating a target flow rate that causes no switching or a minimum count of switching of the combustion stages of the burners and configuring the passing water quantity control unit to have the target flow rate. The operation control unit, upon confirmation that a predetermined release condition of the passing water restriction is satisfied, executes the passing water control in which the passing water quantity is returned to the predetermined water quantity by gradually releasing the passing water restriction.

Abstract: A fryer includes a controller that can perform a first cooking mode and second cooking mode. In the first cooking mode, an object to be cooked is cooked by controlling the pulse combustor with a prescribed first heat quantity when the cooking oil contained in the oil bath is in a prescribed first oil amount, and the object to be cooked is in a prescribed first rated amount. In the second cooking mode, an object to be cooked is cooked by controlling the pulse combustor with a prescribed second heat quantity larger than the first heat quantity when the cooking oil is a prescribed second oil amount larger than the first oil amount, and the object to be cooked is in a prescribed second rated amount larger than the first rated amount.

Abstract: A premixing device includes a first and a second venturi in which air flows by rotation of a centrifugal fan, first and second communication openings disposed in the venturis, respectively, for allowing fuel gas supplied from a gas supply passage to flow out, a flap valve capable of opening and closing the second venturi on a side downstream of the second communication opening, and an equalizing valve disposed in the gas supply passage on a side upstream of the first and the second communication openings. The gas supply passage, which connects between an outlet of the equalizing valve and the first and the second communication openings, diverges from the outlet of the equalizing valve to independently form a first gas passage and a first straight path, and a second gas passage and a second straight path for the venturis, respectively.

Abstract: The premixing device includes a first and a second venturis having a pressure reducing portion for air, and a gas supply passage for supplying fuel gas to the venturis, and generates air-fuel mixture by mixing fuel gas with air flowing in the venturis by using a fan and supplies the air-fuel mixture to a burner. A first and a second nozzles for reducing pressure of fuel gas are disposed in the gas supply passage, and the first and the second nozzles are formed in the same nozzle shape as the pressure reducing portion of the first and the second venturis.

Abstract: A water heater includes a burner, a heat exchanger, a passing water quantity control unit, a temperature detection unit, and an operation control unit. The operation control unit performs the output hot water temperature control by configuring the passing water quantity control unit to have a predetermined passing water quantity that is further restricted compared with a predetermined water quantity, and upon confirmation that a predetermined release condition of the passing water restriction is satisfied, executes the passing water control in which the passing water quantity is returned back to the predetermined water quantity by gradually releasing the passing water restriction, and the operation control unit, when a predetermined undershoot factor of the detected temperature is confirmed while the passing water quantity is returned back to the predetermined water quantity, temporarily stops the release of the restriction of the passing water quantity until the undershoot factor is resolved.

Abstract: A water heater includes a plurality of stages of burners, a water supply pipe, a hot water outlet pipe, a heat exchanger, a passing water quantity control unit, a temperature detection unit, and an operation control unit. The operation control unit, upon confirmation that a predetermined start condition of a passing water restriction is satisfied at a start of a hot water supply, performs the output hot water temperature control by calculating a target flow rate that causes no switching or a minimum count of switching of the combustion stages of the burners and configuring the passing water quantity control unit to have the target flow rate. The operation control unit, upon confirmation that a predetermined release condition of the passing water restriction is satisfied, executes the passing water control in which the passing water quantity is returned to the predetermined water quantity by gradually releasing the passing water restriction.

Abstract: A water heater includes a burner, a heat exchanger, a passing water quantity control unit, a temperature detection unit, and an operation control unit. The operation control unit performs the output hot water temperature control by configuring the passing water quantity control unit to have a predetermined passing water quantity that is further restricted compared with a predetermined water quantity, and upon confirmation that a predetermined release condition of the passing water restriction is satisfied, executes the passing water control in which the passing water quantity is returned back to the predetermined water quantity by gradually releasing the passing water restriction, and the operation control unit, when a predetermined undershoot factor of the detected temperature is confirmed while the passing water quantity is returned back to the predetermined water quantity, temporarily stops the release of the restriction of the passing water quantity until the undershoot factor is resolved.

Abstract: A water heater attachment method is a method for attaching a water heater body to a wall surface by using an attachment member provided at a rear end of an upper surface of the water heater body. The method includes a first step of inserting a tip of a rod member into a through hole formed in the attachment member, the rod member projecting forward from the wall surface, a second step of sliding the attachment member toward the wall surface along the rod member to shift the water heater body to an attachment position of the wall surface, and a third step of fastening the attachment member to the wall surface by a screw in a state where the attachment member is held by the rod member.