JP4114123B2

JP4114123B2 - Water heater

Info

Publication number: JP4114123B2
Application number: JP32758299A
Authority: JP
Inventors: 誠濱田; 和俊松田; 恒男船引; 雅典東内
Original assignee: Noritz Corp
Current assignee: Noritz Corp
Priority date: 1999-11-18
Filing date: 1999-11-18
Publication date: 2008-07-09
Anticipated expiration: 2019-11-18
Also published as: JP2001141303A

Description

【０００１】
【発明の属する技術分野】
本発明はガス、石油、電気を燃料とする給湯器に関するものである。
【０００２】
【従来の技術】
従来、熱交換器を迂回して通水管にバイパス管を設けると共にバイパス管に水量調節弁を設け、しかも通水管の上流に水量センサを設けた給湯器は知られている。
【０００３】
【発明が解決しようとする課題】
ところが、上記従来の給湯器では、冬季に凍結等により熱交換器内の湯水が凍結して凝固した場合、バイパス側を通過する水があれば、この水流による流水量を水量センサが検知し、器具燃焼に必要な最低作動水量以上を検出すると、バーナに点火し、熱交換器に水が流れていないにもかかわらず燃焼を開始してしまい、空だきに近い状態になるという問題があった。
これを防止するためには、最低作動水量の検出時にバイパス管の水量調節弁を一旦全閉にしてから最低作動水量の検出を行なう方法が考えられる。
しかし、この方法では水量調節弁の構造によっては、バイパス弁からの漏れ量が多く、この漏れ量のみで最低作動水量をクリアしてバーナに点火してしまい、これまた空だき状態となる問題を有していた。
【０００４】
本発明は上記問題に鑑み、バイパス弁からの漏れ量が多い場合でも上記空だきになることを防止した給湯器の提供を課題とする。
【０００５】
【課題を解決するための手段】
上記課題を解決するために、本発明の給湯器は、バーナによって加熱される熱交換器と、該熱交換器を迂回して通水管に設けたバイパス管と、該バイパス管よりも上流側の通水管に設けた水量センサと、熱交換器の下流側の通水管に設けた温度センサと、バイパス管に設けたバイパス水量調節弁と、外気温検出センサにより器具の凍結温度を検出した場合に前記バイパス水量調節弁を全閉にするものであって、前記水量センサが最低作動水量以上を検出した場合に器具の必要燃焼量よりも少ない燃焼量で燃焼させる制限燃焼制御手段を設けたことを第１の特徴としている。
この第１の特徴によれば、熱交換器内の水が凍結によって凝固したとしてもバイパス水量調節弁を全閉にすることで、給湯カランを開いても水量センサは流量を検出しないので、バーナに点火することはなく安全である。しかも、バイパス水量調節弁の全閉時になんらかの故障原因により弁自体に漏れが生じ、バイパス管に水流が生じて水量センサが最低作動水量以上を検出したとしても、この検出時にはバーナの燃焼量を通常の燃焼量よりも少ない燃焼量で燃焼させるように制限しているので、熱交換器が一気に加熱されることはなくなり、徐々に熱交換器内部の水管が温められて、内部の氷が解け出すこととなり、その後の水温の測定検出を正確に行なえる利点を有する。
【０００６】
また本発明の給湯器は、バーナによって加熱される熱交換器と、該熱交換器を迂回して通水管に設けたバイパス管と、該バイパス管よりも上流側の通水管に設けた水量センサと、熱交換器の下流側の通水管に設けた温度センサと、バイパス管に設けたバイパス水量調節弁と、外気温検出センサにより器具の凍結温度を検出した場合に前記バイパス水量調節弁を全閉にするものであって、前記水量センサが最低作動水量以上を検出した場合に器具の必要燃焼量よりも少ない燃焼量で燃焼させる制限燃焼制御手段を設けるとともに出湯温度の上昇を検出して燃焼制御に移行するか否か判定する判定手段を設けたことを第２の特徴としている。
上記第２の特徴によれば、凍結の可能性があるときには、バーナを小さな燃焼量で燃焼させるとともに熱交換器から出湯する湯温の上昇度合いを検出することで、上記第１の特徴に加えて、熱交換器が凍結して詰まっている場合は熱交換器に水流が生じないので熱交換器の下流側の温度は上昇せず、また熱交換器が詰まっていない場合には出湯温度は徐々に上昇し、この温度上昇度合いを測定検出することで、熱交換器詰まりを安全に検出することができる。
また本発明の給湯器は、バーナによって加熱される熱交換器と、該熱交換器を迂回して通水管に設けたバイパス管と、該バイパス管よりも上流側の通水管に設けた水量センサと、熱交換器の下流側の通水管に設けた温度センサと、バイパス管に設けたバイパス水量調節弁と、外気温検出センサにより器具の凍結温度を検出した場合に前記バイパス水量調節弁を全閉にするものであって、前記水量センサが最低作動水量以上を検出した場合に器具の必要燃焼量よりも少ない燃焼量で燃焼させる制限燃焼制御手段を設けるとともに出湯温度の上昇を検出して燃焼制御に移行するか否か判定する判定手段を設け、一定以上の温度上昇があれば燃焼制御に移行し温度上昇が一定未満であれば燃焼を停止する制御手段を設けたことを第３の特徴としている。
この第３の特徴によれば、出湯温度の上昇が一定以上であれば燃焼制御に移行し一定未満であれば燃焼を停止するようにしたことで、安全かつ確実に器具の空たきを防止することができる。
さらに本発明は、バーナによって加熱される熱交換器と、該熱交換器を迂回して通水管に設けたバイパス管と、該バイパス管よりも上流側の通水管に設けた水量センサと、熱交換器の下流側の通水管に設けた温度センサと、バイパス管に設けたバイパス水量調節弁と、外気温検出センサにより器具の凍結温度を検出した場合に前記バイパス水量調節弁を全閉にし、前記水量センサが最低作動水量以上を検出した場合に燃焼制御に移行するものであって、最低作動水量以上を検出後一定時間以内にバイパス水量調節弁の最大漏れ量以上の流量を検出すれば燃焼制御に移行する移行制御手段を設けたことを第４の特徴としている。
この第４の特徴によれば、熱交換器に確実に水が流れている場合にのみ比例制御等の燃焼制御に移行するので、熱交換器が空たき状態となることなく、器具を安全に使用することができる。
また本発明は、バーナによって加熱される熱交換器と、該熱交換器を迂回して通水管に設けたバイパス管と、該バイパス管よりも上流側の通水管に設けた水量センサと、熱交換器の下流側の通水管に設けた温度センサおよび過流出を防止する過流出防止弁と、バイパス管に設けたバイパス水量調節弁と、外気温検出センサにより器具の凍結温度を検出した場合に前記バイパス水量調節弁を全閉にし、前記水量センサが最低作動水量以上を検出した場合に燃焼制御に移行するものであって、最低作動水量以上を検出後一定時間後に最低作動水量以上で一定流量未満の流量を検出すれば、前記過流出防止弁の開度を前記最低作動水量と一定流量との間の所定流量に制限する制限手段を設けたことを第５の特徴としている。
この第５の特徴によれば、同じ燃焼量に対する出湯温度の上昇が大きくなり、その後の温度検出において検出精度の向上を図ることができる。
【０００７】
【発明の実施の形態】
以下、本発明の実施の形態について図面を参照しながら説明する。図１は本発明の一実施形態を示す給湯器の全体構成図である。図２は本発明の一実施形態を示すフローチャートである。図３は本発明の他の実施形態を示すフローチャートである。
【０００８】
図１において、１は給湯器であり、その内部にはフインに水管を貫通させた熱交換器２、加熱用のガスバーナ３、燃焼空気送風用の送風ファン４、各種の制御を行うための本体コントローラ５を備えている。６は給湯器1を遠隔操作すると共に給湯温度・時刻等の操作情報を画面に表示する表示部７を有するリモコンであり、報知用のブザー８等を内蔵してある。
【０００９】
９は熱交換器２に至る入水管、１０は熱交換器２から後述する浴室カランに至る出湯管である。入水管９および出湯管１０からなり熱交換器２に接続する通水管１１にはその上流側から水管内の通水量を検出する水量センサ１２および入水温度を検出する水温センサ１３を設けている。出湯管１０には熱交換器２により加熱された湯温を検出する感温部材としてのサーミスタ等からなる温度センサ１４を設けてある。この温度センサ１４は湯水を混合させた後の湯温を検出するものであってもよい。
【００１０】
１５はガスバーナ３に至るガス管であり、このガス管１５にはガス通路を開閉するガス電磁弁１６、ガス供給量を制御するガス比例弁１７等を設けてある。そしてバーナの近傍にはイグナイター等の点火電極１８を設けてある。本体コントローラ５とリモコン６とは通信用インターフェースを介して接続され、温度センサ１４、水量センサ１２の他各種センサからの検出信号に基づいて給湯器本体の状態を判定するともに、リモコン６からの制御信号に基づいて給湯器本体の各部（例えばガス電磁弁、ガス比例弁等）の動作を制御するものである。１９は通水管に設けた通水量を調節する過流出防止弁であり、サーボモータによって駆動され通水量を調節するものである。さらに熱交換器２を迂回して通水管にはバイパス管２０を設け、このバイパス管２０にはバイパス管の通水量を調節するためのバイパス水量調節弁２１を設けてある。
【００１１】
２２は給湯器の出湯管１０を延長して設けられ浴槽に至る風呂給湯管でありその末端には浴室カラン２３を設けている。２４は風呂給湯管２２から分岐して設けた一般給湯管であり、その末端には台所カラン２５等を設けてある。給湯器の出湯能力によっては、台所の他洗面所、トイレ等にも給湯カランを設けても良い。
【００１２】
そして、給湯器１の本体コントローラ５には、温度センサ１４、水温センサ１３、水量センサ１２、送風ファン４、点火電極１８、ガス比例弁１７およびガス電磁弁１６、水量調節弁１９等を接続してある。また、本体コントローラ５には前記水量センサ１２が最低作動水量以上を検出した場合に器具の必要燃焼量よりも少ない燃焼量で燃焼させる制限燃焼制御手段の他、各種の制御手段を設けてある。この制御手段としては、例えば温度センサ１４のよる出湯温度の上昇を検出して燃焼制御に移行するか否かを判定する判定手段である。ここで燃焼制御とはバーナに点火した後設定温度等の設定操作に基づいて比例弁によるバーナへの本格的なガス供給量の調節制御を意味するものである。また、この判定手段により一定以上の温度上昇があれば燃焼制御に移行し、温度上昇が一定未満であれば燃焼を停止する制御手段を設けてある。この本体コントローラ５はマイクロコンピュータから構成してある。また、本体コントローラ５には、水量センサにより通水管に流れる水が最低作動水量以上であることを検出後一定時間以内にバイパス水量調節弁の最大漏れ量以上の流量を検出すれば燃焼制御に移行する移行手段を設けても良い。さらに、水量センサが最低作動水量以上を検出後、一定時間後に最低作動水量以上で一定流量未満の流量を検出すれば、過流出防止弁１９の開度を前記最低作動水量と一定流量との間の所定流量に制限する制限手段を設けても良い。
【００１３】
そして、リモコン６には運転スイッチ、液晶表示部材・蛍光管表示部材・タッチパネル等の表示画面からなる表示部７、該表示部７を裏面から照らし画面を見やすくするためのバックライト、出湯温度を調節するための湯温設定器２６、浴槽２１への落し込み総流量を設定する流量設定器２７およびブザー８等を設けてある。なお、２８は器具の凍結温度を検出して作動する外気温検出センサであり、凍結温度を検知したのち一定時間経過するとバイパス管２０に設けたバイパス水量調節弁２１を全閉にするように制御する。
【００１４】
次に、本発明の作動を図２のフローチャートに基づいて説明する。
冬季において、外気温が低下して器具が凍結しているときには、外気温検出センサ２８が作動し（ステップＳ１）本体コントローラ５を介して、バイパス管に設けたバイパス水量調節弁２１を全閉にする（ステップＳ２）。一般には凍結防止ヒータが作動して熱交換器は保護されるのであるが、凍結防止ヒータが故障している状態では凍結が起こりうる。この状態で給湯カラン２５等を開くと、通常では通水が開始されるが、熱交換器およびバイパス管の双方が凍結している場合には通水されず、水量センサ１２も作動せず、従って器具は点火しないので問題はない。
【００１５】
ところが、まれに、熱交換器２は凍結して詰まっているがバイパス管２０はいまだ凍結していない場合であってしかもバイパス水量調節弁２１が故障によって全閉とはならずに開いていたときにはバイパス管２０を経て流れが生じる。このため、水量センサがバーナ点火に必要な最低作動水量以上を検出すると（ステップＳ３でイエスの場合）、次のステップに移り、一定時間（３秒間）以内にバイパス水量調節弁２１の最大漏れ量である１秒間に７リットル以上の流量があるか否かを検出するようにしてある（ステップＳ４）。この水量センサによる検出の結果、７リットル以上の流量があればバイパス管のほかに熱交換器にも通水があることを意味するので、熱交換器２は完全には詰まっていないことになる。そこでこの場合には通常の燃焼量で以後の燃焼制御を行なわせる。
【００１６】
ところが、ステップＳ４において一定時間以内に７リットル／１秒未満の流量しかない場合には、このまま通常の燃焼量で制御すると熱交換器が一気に加熱されて危険である。そこで、この場合には器具の通常の必要燃焼量よりも少ない燃焼量で燃焼させる制限燃焼制御手段により、少量燃焼させることとしている（ステップＳ５）。この燃焼量は通常加熱量の１０分の１程度で良い。これにより熱交換器の急激な加熱による空たき状態となるのを防止することができる。
【００１７】
そして、少量燃焼から一定時間（１０秒間程度）経過後（ステップＳ６でイエスの場合）、温度センサ１４により出湯温度の上昇を検出して（ステップＳ７）、例えば入水温度よりも７℃上昇すれば熱交換器２の詰まりは解消したものと判断されるので、燃焼制御に移行するようにし（ステップＳ８）、そうでない場合（ステップＳ７でノーの場合）には燃焼そのものを停止して安全側に動作させるようにしてある（ステップＳ９）。もちろん、外気温が高い場合（ステップＳ１でノーの場合）には、給湯カランを開いて、水量センサが最低作動水量以上を検出すれば、燃焼制御に移行することには変わりはないものである。
【００１８】
次に、本発明の他の実施形態について図３のフローチャートについて説明する。図２と同じ番号を付けてあるフローは同じ動きであることを示している。
【００１９】
冬季において、外気温が低下して器具が凍結しているときには、外気温検出センサ２８が作動し（ステップＳ１）本体コントローラ５を介して、バイパス管に設けたバイパス水量調節弁２１を全閉にする（ステップＳ２）。
熱交換器２は凍結して詰まっているがバイパス管２０はいまだ凍結していない場合であってしかもバイパス水量調節弁２１が故障によって全閉とはならずに開いていたときにはバイパス管２０を経て流れが生じる。このため、水量センサがバーナ点火に必要な最低作動水量以上を検出すると（ステップＳ３でイエスの場合）、次のステップに移り、一定時間（３秒間）以内にバイパス水量調節弁２１の最大漏れ量である１秒間に７リットル以上の流量があるか否かを検出する（ステップＳ４）。この水量センサによる検出の結果、７リットル以上の流量があればバイパス管のほかに熱交換器にも通水があることを意味するので、熱交換器２は完全には詰まっていないことになる。そこでこの場合には通常の燃焼量で以後の燃焼制御を行なわせる。
ところが、ステップＳ４において一定時間以内に７リットル／１秒未満の流量しかない場合には、このまま通常の燃焼量で制御すると熱交換器が一気に加熱されて危険である。
【００２０】
そこで、この場合には本体コントローラ５により過流出防止弁１９の開度を最低作動水量と一定流量（７リットル／秒）との間の所定流量に制限するようにしてある（ステップＳ１０）。ここで所定流量とは、例えば４リットル／秒程度の流量であることが望ましい。これにより、同じ必要燃焼量に対する出湯温度上昇が大きく見込めるため、温度検出の精度を向上させることができる。またバイパス水量調節弁からの漏れ量にかかわらず一定の流量となるため温度上昇も安定することとなる。そして、この制御に加えて、器具の通常の必要燃焼量よりも少ない燃焼量で燃焼させる制限燃焼制御手段により、少量燃焼させることとしている（ステップＳ５）。この燃焼量は通常加熱量の１０分の１程度で良い。これにより熱交換器の急激な加熱による空たき状態となるのを防止することができる。
【００２１】
そして、少量燃焼から一定時間（１０秒間程度）経過後（ステップＳ６でイエスの場合）、温度センサ１４により出湯温度の上昇を検出して（ステップＳ７）、例えば入水温度よりも７℃上昇すれば熱交換器２の詰まりは解消したものと判断されるので、燃焼制御に移行するようにし（ステップＳ８）、そうでない場合（ステップＳ７でノーの場合）には燃焼そのものを停止して安全側に動作させるようにしてある（ステップＳ９）。もちろん、外気温が高い場合（ステップＳ１でノーの場合）には、給湯カランを開いて、水量センサが最低作動水量以上を検出すれば、燃焼制御に移行することには変わりはないものである。
【００２２】
なお、上述した実施形態は本発明の好適な実施形態を示すものであって、本発明はこれに限定されることなく、その範囲内で各種設計変更可能である。例えば、上記実施形態においては、熱交換器の出口に設けた温度センサにより湯温を検出しているが、この例に限られずバイパスミキシング後の出湯温度を検出するようにしても良い。
加えて、本実施形態では、温度上昇を検出できない場合には燃焼を停止したままにしているが、一定時間後スタートから再度フローを繰り返すようにしても良い。
さらに、出湯温度の上昇を検出して燃焼制御に移行するか否かを判定するようにしているが、この出湯温度の上昇を検出中に熱交換器の出口温度が一定の高温度（例えば９０℃）を検出した場合にも、熱交換器が詰まっていると判定するようにしても良い。
また同様に上記実施形態では、給湯器本体とリモコンとが有線接続された場合を図示したが、もちろんこれらの間を無線方式で連携させることも可能である。また、ガスを燃料とする給湯器について説明したが石油を燃料とするものであっても良いことはもちろんである。
【００２３】
【発明の効果】
本発明は以上の構成、作用からなり、請求項１に記載の給湯器によれば、バーナによって加熱される熱交換器と、該熱交換器を迂回して通水管に設けたバイパス管と、該バイパス管よりも上流側の通水管に設けた水量センサと、熱交換器の下流側の通水管に設けた温度センサと、バイパス管に設けたバイパス水量調節弁と、外気温検出センサにより器具の凍結温度を検出した場合に前記バイパス水量調節弁を全閉にするものであって、前記水量センサが最低作動水量以上を検出した場合に器具の必要燃焼量よりも少ない燃焼量で燃焼させる制限燃焼制御手段を設けたので、熱交換器内の水が凍結によって凝固したとしてもバイパス水量調節弁を全閉にすることで、給湯カランを開いても水量センサは流量を検出しないので、バーナに点火することはなく安全である。しかも、バイパス水量調節弁の全閉時になんらかの故障原因により弁自体に漏れが生じ、バイパス管に水流が生じて水量センサが最低作動水量以上を検出したとしても、この検出時にはバーナの燃焼量を通常の燃焼量よりも少ない燃焼量で燃焼させるように制限しているので、熱交換器が一気に加熱されることはなくなり、徐々に熱交換器内部の水管が温められて、内部の氷が解け出すこととなり、その後の水温の測定検出を正確に行なえる利点を有する。
また、請求項２に記載の給湯器によれば、バーナによって加熱される熱交換器と、該熱交換器を迂回して通水管に設けたバイパス管と、該バイパス管よりも上流側の通水管に設けた水量センサと、熱交換器の下流側の通水管に設けた温度センサと、バイパス管に設けたバイパス水量調節弁と、外気温検出センサにより器具の凍結温度を検出した場合に前記バイパス水量調節弁を全閉にするものであって、前記水量センサが最低作動水量以上を検出した場合に器具の必要燃焼量よりも少ない燃焼量で燃焼させる制限燃焼制御手段を設けるとともに出湯温度の上昇を検出して燃焼制御に移行するか否か判定する判定手段を設けたので、凍結の可能性があるときには、バーナを小さな燃焼量で燃焼させるとともに熱交換器から出湯する湯温の上昇度合いを検出することで、上記第１の特徴に加えて、熱交換器が凍結して詰まっている場合は熱交換器に水流が生じないので熱交換器の下流側の温度は上昇せず、また熱交換器が詰まっていない場合には出湯温度は徐々に上昇し、この温度上昇度合いを測定検出することで、熱交換器詰まりを安全に検出することができる。
また本発明の給湯器は、バーナによって加熱される熱交換器と、該熱交換器を迂回して通水管に設けたバイパス管と、該バイパス管よりも上流側の通水管に設けた水量センサと、熱交換器の下流側の通水管に設けた温度センサと、バイパス管に設けたバイパス水量調節弁と、外気温検出センサにより器具の凍結温度を検出した場合に前記バイパス水量調節弁を全閉にするものであって、前記水量センサが最低作動水量以上を検出した場合に器具の必要燃焼量よりも少ない燃焼量で燃焼させる制限燃焼制御手段を設けるとともに出湯温度の上昇を検出して燃焼制御に移行するか否か判定する判定手段を設け、一定以上の温度上昇があれば燃焼制御に移行し温度上昇が一定未満であれば燃焼を停止する制御手段を設けたので、出湯温度の上昇が一定以上であれば燃焼制御に移行し一定未満であれば燃焼を停止するようにしたことで、安全かつ確実に器具の空たきを防止することができる。
さらに本発明は、バーナによって加熱される熱交換器と、該熱交換器を迂回して通水管に設けたバイパス管と、該バイパス管よりも上流側の通水管に設けた水量センサと、熱交換器の下流側の通水管に設けた温度センサと、バイパス管に設けたバイパス水量調節弁と、外気温検出センサにより器具の凍結温度を検出した場合に前記バイパス水量調節弁を全閉にし、前記水量センサが最低作動水量以上を検出した場合に燃焼制御に移行するものであって、最低作動水量以上を検出後一定時間以内にバイパス水量調節弁の最大漏れ量以上の流量を検出すれば燃焼制御に移行する移行制御手段を設けたので、熱交換器に確実に水が流れている場合にのみ比例制御等の燃焼制御に移行するので、熱交換器が空たき状態となることなく、器具を安全に使用することができる。
また本発明は、バーナによって加熱される熱交換器と、該熱交換器を迂回して通水管に設けたバイパス管と、該バイパス管よりも上流側の通水管に設けた水量センサと、熱交換器の下流側の通水管に設けた温度センサおよび過流出を防止する過流出防止弁と、バイパス管に設けたバイパス水量調節弁と、外気温検出センサにより器具の凍結温度を検出した場合に前記バイパス水量調節弁を全閉にし、前記水量センサが最低作動水量以上を検出した場合に燃焼制御に移行するものであって、最低作動水量以上を検出後一定時間後に最低作動水量以上で一定流量未満の流量を検出すれば、前記過流出防止弁の開度を前記最低作動水量と一定流量との間の所定流量に制限する制限手段を設けので、同じ燃焼量に対する出湯温度の上昇が大きくなり、その後の温度検出において検出精度の向上を図ることができる。
【図面の簡単な説明】
【図１】本発明を適用した給湯器の全体構成図である。
【図２】本発明の一実施形態を示すフローチャートである。
【図３】本発明の他の実施形態を示すフローチャートである。
【符号の説明】
１給湯器
２熱交換器
３バーナ
５本体コントローラ
１１通水管
１２水量センサ
１４温度センサ
１９過流出防止弁
２０バイパス管
２１バイパス水量調節弁
２８外気温検出センサ[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a water heater using gas, oil, and electricity as fuel.
[0002]
[Prior art]
2. Description of the Related Art Conventionally, there is known a water heater that bypasses a heat exchanger and is provided with a bypass pipe in the water pipe and a water amount adjusting valve in the bypass pipe, and further provided with a water amount sensor upstream of the water pipe.
[0003]
[Problems to be solved by the invention]
However, in the above-described conventional water heater, when the hot water in the heat exchanger freezes and solidifies due to freezing or the like in winter, if there is water passing through the bypass side, the water volume sensor detects the amount of water flowing by this water flow, When detecting more than the minimum amount of working water required for instrument combustion, there was a problem that the burner was ignited and combustion started even though water did not flow through the heat exchanger, and it became almost empty. .
In order to prevent this, it is conceivable to detect the minimum working water amount after the water amount adjusting valve of the bypass pipe is once fully closed when the minimum working water amount is detected.
However, in this method, depending on the structure of the water amount control valve, there is a large amount of leakage from the bypass valve, and this leakage amount alone clears the minimum working water amount and ignites the burner, which also causes a problem of emptying. Had.
[0004]
In view of the above problems, an object of the present invention is to provide a water heater that prevents the above-mentioned emptying even when the amount of leakage from the bypass valve is large.
[0005]
[Means for Solving the Problems]
In order to solve the above-described problems, a water heater of the present invention includes a heat exchanger heated by a burner, a bypass pipe that bypasses the heat exchanger and is provided in a water pipe, and an upstream side of the bypass pipe. When the freezing temperature of the appliance is detected by the water amount sensor provided in the water pipe, the temperature sensor provided in the water pipe downstream of the heat exchanger, the bypass water amount control valve provided in the bypass pipe, and the outside air temperature detection sensor The bypass water amount adjustment valve is fully closed, and when the water amount sensor detects a minimum working water amount or more, a limited combustion control means is provided for burning with a combustion amount smaller than the required combustion amount of the appliance. This is the first feature.
According to this first feature, even if the water in the heat exchanger has solidified due to freezing, the water volume sensor does not detect the flow rate even when the hot water supply curl is opened by fully closing the bypass water volume control valve. It is safe without igniting. Moreover, even when the bypass water amount adjustment valve is fully closed, the valve itself leaks due to some cause of failure, and even if a water flow occurs in the bypass pipe and the water amount sensor detects the minimum operating water amount, The heat exchanger is not heated at a stretch, and the water pipe inside the heat exchanger is gradually warmed and the internal ice melts. Thus, there is an advantage that the subsequent measurement and detection of the water temperature can be performed accurately.
[0006]
Further, the water heater of the present invention includes a heat exchanger heated by a burner, a bypass pipe provided in the water pipe bypassing the heat exchanger, and a water amount sensor provided in the water pipe upstream of the bypass pipe. And a temperature sensor provided in the water flow pipe on the downstream side of the heat exchanger, a bypass water amount adjustment valve provided in the bypass pipe, and the bypass water amount adjustment valve when the freezing temperature of the appliance is detected by the outside air temperature detection sensor. When the water amount sensor detects a minimum working water amount or more, it is provided with a limited combustion control means for combusting with a combustion amount smaller than the required combustion amount of the appliance, and detecting a rise in the tapping temperature and combusting A second feature is that a determination means for determining whether or not to shift to control is provided.
According to the second feature, when there is a possibility of freezing, in addition to the first feature, the burner is burned with a small amount of combustion and the rise in the temperature of the hot water discharged from the heat exchanger is detected. If the heat exchanger is frozen and clogged, there will be no water flow in the heat exchanger, so the temperature on the downstream side of the heat exchanger will not rise, and if the heat exchanger is not clogged, the tapping temperature will be By gradually increasing and measuring and detecting this degree of temperature rise, it is possible to safely detect clogging of the heat exchanger.
Further, the water heater of the present invention includes a heat exchanger heated by a burner, a bypass pipe provided in the water pipe bypassing the heat exchanger, and a water amount sensor provided in the water pipe upstream of the bypass pipe. And a temperature sensor provided in the water flow pipe on the downstream side of the heat exchanger, a bypass water amount adjustment valve provided in the bypass pipe, and the bypass water amount adjustment valve when the freezing temperature of the appliance is detected by the outside air temperature detection sensor. When the water amount sensor detects a minimum working water amount or more, it is provided with a limited combustion control means for combusting with a combustion amount smaller than the required combustion amount of the appliance, and detecting a rise in the tapping temperature and combusting A third feature is that a determination means for determining whether or not to shift to control is provided, a control means is provided to shift to combustion control if the temperature rises above a certain level, and to stop combustion if the temperature rise is less than a certain level. Toi .
According to the third feature, if the rise in the tapping temperature is above a certain level, the process shifts to combustion control, and if it is below a certain level, the combustion is stopped, thereby preventing the emptying of the instrument safely and reliably. be able to.
Furthermore, the present invention includes a heat exchanger heated by a burner, a bypass pipe that is provided in the water pipe so as to bypass the heat exchanger, a water amount sensor that is provided in the water pipe on the upstream side of the bypass pipe, When the temperature sensor provided in the water flow pipe on the downstream side of the exchanger, the bypass water amount adjustment valve provided in the bypass pipe, and the freezing temperature of the appliance is detected by the outside air temperature detection sensor, the bypass water amount adjustment valve is fully closed, When the water amount sensor detects a minimum working water amount or more, it shifts to combustion control, and if a flow rate that exceeds the maximum leakage amount of the bypass water amount control valve is detected within a certain time after detecting the minimum working water amount or more, combustion is performed. A fourth feature is that a transition control means for shifting to control is provided.
According to the fourth feature, since the shift to the combustion control such as the proportional control is performed only when the water is surely flowing in the heat exchanger, the appliance can be safely operated without the heat exchanger becoming empty. Can be used.
The present invention also includes a heat exchanger that is heated by a burner, a bypass pipe that bypasses the heat exchanger and is provided in the water pipe, a water amount sensor that is provided in the water pipe upstream of the bypass pipe, When the freezing temperature of the appliance is detected by the temperature sensor provided in the water flow pipe on the downstream side of the exchanger, the overflow prevention valve that prevents overflow, the bypass water amount adjustment valve provided in the bypass pipe, and the outside air temperature detection sensor The bypass water amount control valve is fully closed, and the control is shifted to the combustion control when the water amount sensor detects a minimum working water amount or more, and after a certain time after detecting the minimum working water amount or more, a constant flow rate over the minimum working water amount. A fifth feature is that a limiting means is provided for limiting the opening degree of the overflow prevention valve to a predetermined flow rate between the minimum working water amount and a constant flow rate when a flow rate of less than 10 is detected.
According to the fifth feature, the rise of the hot water temperature with respect to the same combustion amount is increased, and the detection accuracy can be improved in the subsequent temperature detection.
[0007]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, embodiments of the present invention will be described with reference to the drawings. FIG. 1 is an overall configuration diagram of a water heater showing an embodiment of the present invention. FIG. 2 is a flowchart showing an embodiment of the present invention. FIG. 3 is a flowchart showing another embodiment of the present invention.
[0008]
In FIG. 1, reference numeral 1 denotes a water heater, in which a heat exchanger 2 in which a water pipe passes through a fin, a gas burner 3 for heating, a blower fan 4 for blowing combustion air, and a main body for performing various controls A controller 5 is provided. Reference numeral 6 denotes a remote controller having a display unit 7 for remotely operating the water heater 1 and displaying operation information such as a hot water temperature and time on a screen, and has a buzzer 8 for notification built therein.
[0009]
Reference numeral 9 denotes a water inlet pipe that leads to the heat exchanger 2, and 10 denotes a hot water outlet pipe that leads from the heat exchanger 2 to a bathroom calan described later. A water pipe 11 comprising a water inlet pipe 9 and a hot water outlet pipe 10 and connected to the heat exchanger 2 is provided with a water amount sensor 12 for detecting the amount of water passing through the water pipe from its upstream side and a water temperature sensor 13 for detecting the incoming water temperature. The hot water outlet pipe 10 is provided with a temperature sensor 14 made up of a thermistor or the like as a temperature sensitive member for detecting the temperature of hot water heated by the heat exchanger 2. This temperature sensor 14 may detect the hot water temperature after mixing hot water and water.
[0010]
A gas pipe 15 extends to the gas burner 3. The gas pipe 15 is provided with a gas electromagnetic valve 16 for opening and closing the gas passage, a gas proportional valve 17 for controlling the gas supply amount, and the like. An ignition electrode 18 such as an igniter is provided in the vicinity of the burner. The main body controller 5 and the remote controller 6 are connected via a communication interface, and the state of the water heater main body is determined based on detection signals from various sensors other than the temperature sensor 14 and the water amount sensor 12, and the control from the remote controller 6 is performed. Based on the signal, the operation of each part (for example, a gas solenoid valve, a gas proportional valve, etc.) of the water heater main body is controlled. An overflow prevention valve 19 for adjusting the water flow rate provided in the water flow tube is driven by a servo motor to adjust the water flow rate. Further, a bypass pipe 20 is provided in the water pipe bypassing the heat exchanger 2, and a bypass water amount adjusting valve 21 for adjusting the water flow quantity of the bypass pipe is provided in the bypass pipe 20.
[0011]
Reference numeral 22 denotes a bath hot water supply pipe that extends from the hot water supply pipe 10 of the water heater and reaches the bathtub, and a bathroom currant 23 is provided at the end thereof. Reference numeral 24 denotes a general hot water supply pipe that is branched from the bath hot water supply pipe 22, and a kitchen currant 25 is provided at the end thereof. Depending on the hot water supply capacity of the water heater, a hot water supply curan may be provided in the restroom, toilet, etc. of the kitchen.
[0012]
A temperature sensor 14, a water temperature sensor 13, a water amount sensor 12, a blower fan 4, an ignition electrode 18, a gas proportional valve 17 and a gas electromagnetic valve 16, a water amount adjustment valve 19, and the like are connected to the main body controller 5 of the water heater 1. It is. The main body controller 5 is provided with various control means in addition to the limited combustion control means for burning with a combustion amount smaller than the required combustion amount of the appliance when the water amount sensor 12 detects a minimum working water amount or more. As this control means, for example, it is a judgment means for detecting whether or not the hot water temperature rise by the temperature sensor 14 is detected to shift to the combustion control. Here, the combustion control means a full control of the gas supply amount to the burner by a proportional valve based on a setting operation such as a set temperature after the burner is ignited. Further, there is provided control means for shifting to combustion control if the temperature rises above a certain level by this judging means, and stopping combustion if the temperature rise is less than a constant. The main body controller 5 is composed of a microcomputer. Further, the main body controller 5 shifts to combustion control if it detects a flow rate exceeding the maximum leakage amount of the bypass water amount adjustment valve within a certain time after detecting that the water flowing through the water pipe is more than the minimum working water amount by the water amount sensor. There may be provided a transition means. Furthermore, if the water amount sensor detects a flow rate that is greater than or equal to the minimum working water amount and detects a flow rate that is greater than or equal to the minimum working water amount and less than a certain flow rate after a certain time, the opening degree of the overflow prevention valve 19 is set between the minimum working water amount and the constant flow rate. Limiting means for limiting to a predetermined flow rate may be provided.
[0013]
The remote control 6 has a display unit 7 comprising a display screen such as an operation switch, a liquid crystal display member, a fluorescent tube display member, a touch panel, etc., a backlight for illuminating the display unit 7 from the back side to make the screen easy to see, and adjusting the hot water temperature There are provided a hot water temperature setting device 26, a flow rate setting device 27 for setting the total flow rate dropped into the bathtub 21, a buzzer 8, and the like. Reference numeral 28 denotes an outside air temperature detection sensor that operates by detecting the freezing temperature of the appliance, and is controlled so that the bypass water amount adjusting valve 21 provided in the bypass pipe 20 is fully closed after a certain time has elapsed after detecting the freezing temperature. To do.
[0014]
Next, the operation of the present invention will be described based on the flowchart of FIG.
In winter, when the outside air temperature decreases and the appliance is frozen, the outside air temperature detection sensor 28 is activated (step S1), and the bypass water amount adjustment valve 21 provided in the bypass pipe is fully closed via the main body controller 5. (Step S2). In general, the antifreeze heater operates to protect the heat exchanger, but freezing can occur when the antifreeze heater is out of order. When the hot water supply currant 25 or the like is opened in this state, water is normally started. However, when both the heat exchanger and the bypass pipe are frozen, water is not passed and the water amount sensor 12 is not activated. Therefore, there is no problem because the appliance does not ignite.
[0015]
However, in rare cases, when the heat exchanger 2 is frozen and clogged, but the bypass pipe 20 is not yet frozen, and the bypass water amount adjustment valve 21 is not fully closed due to a failure, but is opened. Flow occurs through the bypass pipe 20. For this reason, when the water amount sensor detects a value equal to or higher than the minimum working water amount required for the burner ignition (in the case of YES in step S3), the process proceeds to the next step, and the maximum leakage amount of the bypass water amount adjustment valve 21 within a certain time (3 seconds). Whether or not there is a flow rate of 7 liters or more per second is detected (step S4). As a result of detection by the water amount sensor, if there is a flow rate of 7 liters or more, it means that there is water passing through the heat exchanger in addition to the bypass pipe, so the heat exchanger 2 is not completely clogged. . Therefore, in this case, the subsequent combustion control is performed with the normal combustion amount.
[0016]
However, if there is only a flow rate of less than 7 liters / second within a predetermined time in step S4, the heat exchanger is heated at a stroke and dangerous if it is controlled with the normal combustion amount as it is. Therefore, in this case, a small amount of combustion is performed by the limited combustion control means for burning with a combustion amount smaller than the normal required combustion amount of the appliance (step S5). The amount of combustion may be about 1/10 of the normal heating amount. As a result, it is possible to prevent the heat exchanger from becoming empty due to rapid heating.
[0017]
Then, after a lapse of a certain time (about 10 seconds) from the small amount of combustion (in the case of YES in step S6), the temperature sensor 14 detects an increase in the hot water temperature (step S7) and, for example, rises by 7 ° C. from the incoming water temperature. Since it is determined that the clogging of the heat exchanger 2 has been resolved, the control is shifted to the combustion control (step S8). Otherwise (in the case of no in step S7), the combustion itself is stopped and the safety side is reached. It is made to operate (step S9). Of course, when the outside air temperature is high (in the case of NO in step S1), if the hot water supply curan is opened and the water amount sensor detects the amount of the minimum working water amount or more, the transition to the combustion control is not changed. .
[0018]
Next, another embodiment of the present invention will be described with reference to the flowchart of FIG. The flow numbered the same as in FIG. 2 indicates the same movement.
[0019]
In winter, when the outside air temperature decreases and the appliance is frozen, the outside air temperature detection sensor 28 is activated (step S1), and the bypass water amount adjustment valve 21 provided in the bypass pipe is fully closed via the main body controller 5. (Step S2).
When the heat exchanger 2 is frozen and clogged, but the bypass pipe 20 has not been frozen yet, and the bypass water amount adjusting valve 21 is not fully closed due to a failure, the bypass pipe 20 passes through the bypass pipe 20. A flow occurs. For this reason, when the water amount sensor detects a value equal to or higher than the minimum working water amount required for the burner ignition (in the case of YES in step S3), the process proceeds to the next step, and the maximum leakage amount of the bypass water amount adjustment valve 21 within a certain time (3 seconds). It is detected whether or not there is a flow rate of 7 liters or more in one second (step S4). As a result of detection by the water amount sensor, if there is a flow rate of 7 liters or more, it means that there is water passing through the heat exchanger in addition to the bypass pipe, so the heat exchanger 2 is not completely clogged. . Therefore, in this case, the subsequent combustion control is performed with the normal combustion amount.
However, if there is only a flow rate of less than 7 liters / second within a predetermined time in step S4, the heat exchanger is heated at a stroke and dangerous if it is controlled with the normal combustion amount as it is.
[0020]
Therefore, in this case, the main controller 5 limits the opening degree of the overflow prevention valve 19 to a predetermined flow rate between the minimum working water amount and a constant flow rate (7 liters / second) (step S10). Here, the predetermined flow rate is preferably a flow rate of about 4 liters / second, for example. Thereby, since the rise in the hot water temperature with respect to the same required combustion amount can be expected to be large, the accuracy of temperature detection can be improved. Moreover, since the flow rate is constant regardless of the amount of leakage from the bypass water amount adjustment valve, the temperature rise is stabilized. In addition to this control, a small amount of combustion is performed by the limited combustion control means for burning with a combustion amount smaller than the normal required combustion amount of the appliance (step S5). The amount of combustion may be about 1/10 of the normal heating amount. As a result, it is possible to prevent the heat exchanger from becoming empty due to rapid heating.
[0021]
Then, after a lapse of a certain time (about 10 seconds) from the small amount of combustion (in the case of YES in step S6), the temperature sensor 14 detects an increase in the hot water temperature (step S7). Since it is determined that the clogging of the heat exchanger 2 has been resolved, the control is shifted to the combustion control (step S8). Otherwise (in the case of no in step S7), the combustion itself is stopped and the safety side is reached. It is made to operate (step S9). Of course, when the outside air temperature is high (in the case of NO in step S1), if the hot water supply curan is opened and the water amount sensor detects the amount of the minimum working water amount or more, the transition to the combustion control is not changed. .
[0022]
In addition, embodiment mentioned above shows suitable embodiment of this invention, This invention is not limited to this, Various design changes are possible within the range. For example, in the above embodiment, the hot water temperature is detected by the temperature sensor provided at the outlet of the heat exchanger. However, the present invention is not limited to this example, and the hot water temperature after bypass mixing may be detected.
In addition, in the present embodiment, when the temperature rise cannot be detected, the combustion is stopped, but the flow may be repeated from the start after a certain time.
Further, it is determined whether or not the shift to the combustion control is performed by detecting the rise in the hot water temperature. While detecting the rise in the hot water temperature, the outlet temperature of the heat exchanger is a constant high temperature (for example, 90). (° C.) may also be detected that the heat exchanger is clogged.
Similarly, in the above-described embodiment, the case where the water heater main body and the remote controller are connected by wire is illustrated, but it is also possible to link them in a wireless manner. Moreover, although the hot water heater using gas as fuel has been described, it is needless to say that oil may be used as fuel.
[0023]
【The invention's effect】
The present invention comprises the above-described configuration and action, and according to the hot water heater according to claim 1, a heat exchanger heated by a burner, a bypass pipe provided in a water pipe bypassing the heat exchanger, A water amount sensor provided in a water pipe upstream of the bypass pipe, a temperature sensor provided in a water pipe downstream of the heat exchanger, a bypass water amount adjustment valve provided in the bypass pipe, and an outside air temperature detection sensor When the freezing temperature is detected, the bypass water amount adjustment valve is fully closed, and when the water amount sensor detects a minimum working water amount or more, the combustion is controlled with a combustion amount smaller than the required combustion amount of the appliance. Since the combustion control means is provided, even if the water in the heat exchanger solidifies due to freezing, the water volume sensor does not detect the flow rate even when the hot water supply curl is opened by fully closing the bypass water volume control valve. Ignite It is safe, not with. Moreover, even when the bypass water amount adjustment valve is fully closed, the valve itself leaks due to some cause of failure, and even if a water flow occurs in the bypass pipe and the water amount sensor detects the minimum operating water amount, The heat exchanger is not heated at a stretch, and the water pipe inside the heat exchanger is gradually warmed and the internal ice melts. Thus, there is an advantage that the subsequent measurement and detection of the water temperature can be performed accurately.
According to the water heater of claim 2, the heat exchanger heated by the burner, the bypass pipe bypassing the heat exchanger and provided in the water pipe, and the upstream side of the bypass pipe When the freezing temperature of the appliance is detected by the water amount sensor provided in the water pipe, the temperature sensor provided in the water pipe downstream of the heat exchanger, the bypass water amount control valve provided in the bypass pipe, and the outside air temperature detection sensor The bypass water amount control valve is fully closed, and when the water amount sensor detects a minimum working water amount or more, a restriction combustion control means for burning with a combustion amount smaller than the required combustion amount of the appliance is provided and the temperature of the tapping water is adjusted. Since there is a judgment means for detecting whether or not to shift to combustion control, when there is a possibility of freezing, the degree of rise in the hot water temperature that burns the burner with a small combustion amount and is discharged from the heat exchanger In addition to the above first feature, when the heat exchanger is frozen and clogged, no water flow is generated in the heat exchanger, so the temperature on the downstream side of the heat exchanger does not rise, Further, when the heat exchanger is not clogged, the temperature of the tapping water gradually rises, and clogging of the heat exchanger can be detected safely by measuring and detecting the degree of temperature rise.
Further, the water heater of the present invention includes a heat exchanger heated by a burner, a bypass pipe provided in the water pipe bypassing the heat exchanger, and a water amount sensor provided in the water pipe upstream of the bypass pipe. And a temperature sensor provided in the water flow pipe on the downstream side of the heat exchanger, a bypass water amount adjustment valve provided in the bypass pipe, and the bypass water amount adjustment valve when the freezing temperature of the appliance is detected by the outside air temperature detection sensor. When the water amount sensor detects a minimum working water amount or more, it is provided with a limited combustion control means for combusting with a combustion amount smaller than the required combustion amount of the appliance, and detecting a rise in the tapping temperature and combusting A determination means is provided to determine whether or not to shift to control, and if there is a temperature rise above a certain level, the control shifts to combustion control, and if the temperature rise is less than a certain level, a control means is provided to stop combustion. Is one By you to stop combustion if migrated less constant combustion control as long or more, it is possible to prevent the Taki empty safely and reliably instrument.
Furthermore, the present invention includes a heat exchanger heated by a burner, a bypass pipe that is provided in the water pipe so as to bypass the heat exchanger, a water amount sensor that is provided in the water pipe on the upstream side of the bypass pipe, When the temperature sensor provided in the water flow pipe on the downstream side of the exchanger, the bypass water amount adjustment valve provided in the bypass pipe, and the freezing temperature of the appliance is detected by the outside air temperature detection sensor, the bypass water amount adjustment valve is fully closed, When the water amount sensor detects a minimum working water amount or more, it shifts to combustion control. Since the transition control means to shift to the control is provided, the shift to the combustion control such as proportional control is performed only when water is surely flowing to the heat exchanger, so that the heat exchanger does not become empty Use safely It can be.
The present invention also includes a heat exchanger that is heated by a burner, a bypass pipe that bypasses the heat exchanger and is provided in the water pipe, a water amount sensor that is provided in the water pipe upstream of the bypass pipe, When the freezing temperature of the appliance is detected by the temperature sensor provided in the water flow pipe on the downstream side of the exchanger, the overflow prevention valve that prevents overflow, the bypass water amount adjustment valve provided in the bypass pipe, and the outside air temperature detection sensor The bypass water amount control valve is fully closed, and the control is shifted to the combustion control when the water amount sensor detects a minimum working water amount or more, and after a certain time after detecting the minimum working water amount or more, a constant flow rate over the minimum working water amount. If a flow rate of less than 10 is detected, there is provided limiting means for limiting the opening degree of the overflow prevention valve to a predetermined flow rate between the minimum working water amount and a constant flow rate, so that the rise of the tapping temperature for the same combustion amount increases. , It is possible to improve the detection accuracy in temperature detection after.
[Brief description of the drawings]
FIG. 1 is an overall configuration diagram of a water heater to which the present invention is applied.
FIG. 2 is a flowchart showing an embodiment of the present invention.
FIG. 3 is a flowchart showing another embodiment of the present invention.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 Water heater 2 Heat exchanger 3 Burner 5 Main body controller 11 Water flow pipe 12 Water quantity sensor 14 Temperature sensor 19 Overflow prevention valve 20 Bypass pipe 21 Bypass water quantity adjustment valve 28 Outside air temperature detection sensor

Claims

A heat exchanger heated by a burner; a bypass pipe provided in the water pipe bypassing the heat exchanger; a water amount sensor provided in the water pipe upstream of the bypass pipe; and a downstream side of the heat exchanger A temperature sensor provided in the water pipe, a bypass water amount adjustment valve provided in the bypass pipe, and when the freezing temperature of the instrument is detected by an outside air temperature detection sensor, the bypass water amount adjustment valve is fully closed, A water heater provided with a limited combustion control means for burning with a combustion amount smaller than a required combustion amount of the appliance when the water amount sensor detects a minimum working water amount or more.

A heat exchanger heated by a burner; a bypass pipe provided in the water pipe bypassing the heat exchanger; a water amount sensor provided in the water pipe upstream of the bypass pipe; and a downstream side of the heat exchanger A temperature sensor provided in the water pipe, a bypass water amount adjustment valve provided in the bypass pipe, and when the freezing temperature of the instrument is detected by an outside air temperature detection sensor, the bypass water amount adjustment valve is fully closed, When the water amount sensor detects a minimum working water amount or more, a limited combustion control means for burning with a combustion amount smaller than the required combustion amount of the appliance is provided, and a determination is made as to whether or not to shift to combustion control by detecting an increase in the tapping temperature. A hot water heater, characterized in that a determination means is provided.

A heat exchanger heated by a burner; a bypass pipe provided in the water pipe bypassing the heat exchanger; a water amount sensor provided in the water pipe upstream of the bypass pipe; and a downstream side of the heat exchanger A temperature sensor provided in the water pipe, a bypass water amount adjustment valve provided in the bypass pipe, and when the freezing temperature of the instrument is detected by an outside air temperature detection sensor, the bypass water amount adjustment valve is fully closed, When the water amount sensor detects a minimum working water amount or more, a limited combustion control means for burning with a combustion amount smaller than the required combustion amount of the appliance is provided, and a determination is made as to whether or not to shift to combustion control by detecting an increase in the tapping temperature. The hot water heater is provided with a control means for providing a determination means for shifting to combustion control if the temperature rises above a certain level and stopping combustion if the temperature rise is less than a certain level.

A heat exchanger heated by a burner; a bypass pipe provided in the water pipe bypassing the heat exchanger; a water amount sensor provided in the water pipe upstream of the bypass pipe; and a downstream side of the heat exchanger When the freezing temperature of the appliance is detected by the outside air temperature detection sensor, the bypass water amount adjustment valve is fully closed, and the water amount sensor is at least at the minimum. Transition to combustion control when the amount of operating water or more is detected, transition to combustion control if a flow rate that exceeds the maximum leakage amount of the bypass water amount control valve is detected within a certain time after detecting the minimum amount of operating water A water heater provided with a control means.

A heat exchanger heated by a burner; a bypass pipe provided in the water pipe bypassing the heat exchanger; a water amount sensor provided in the water pipe upstream of the bypass pipe; and a downstream side of the heat exchanger A temperature sensor provided in the water flow pipe, an overflow prevention valve for preventing excessive outflow, a bypass water amount adjustment valve provided in the bypass pipe, and the bypass water amount adjustment valve when the freezing temperature of the appliance is detected by an outside air temperature detection sensor Is fully closed, and the control goes to combustion control when the water flow sensor detects the minimum working water amount or more, and after a certain amount of time after detecting the minimum working water amount or more, the flow rate that is above the minimum working water amount and less than the constant flow rate is detected. In this case, the water heater is provided with limiting means for limiting the opening degree of the overflow prevention valve to a predetermined flow rate between the minimum working water amount and a constant flow rate.