JP3967267B2

JP3967267B2 - Water heater

Info

Publication number: JP3967267B2
Application number: JP2003005913A
Authority: JP
Inventors: 俊元梶谷; 芳久浦川
Original assignee: Panasonic Corp; Matsushita Electric Industrial Co Ltd
Current assignee: Panasonic Corp; Panasonic Holdings Corp
Priority date: 2003-01-14
Filing date: 2003-01-14
Publication date: 2007-08-29
Anticipated expiration: 2023-01-14
Also published as: JP2004218907A

Description

【０００１】
【発明の属する技術分野】
本発明は、給湯用熱交換器によって加熱された温水を給湯タンクの上部から流入させ、冷水は給湯タンクの下部から流入させることで、給湯タンク内の上部と下部とで湯温差が生じるように給湯水を貯留する給湯機に関する。
【０００２】
【従来の技術】
従来より、冷凍サイクルを用いたヒートポンプ式給湯機が提案されており、例えば冷凍サイクルを利用して給湯タンク内に温水を貯留するものや、浴槽への給湯を行うものが提案されている（例えば特許文献１、特許文献２参照）。
【０００３】
【特許文献１】
特開２００２−１３０８１９号公報
【特許文献２】
特開２００２−２４３２７４号公報
【０００４】
【発明が解決しようとする課題】
しかし、従来では、給湯タンク内の水を加熱する給湯用熱交換器を循環するための回路や、給湯タンク内の温水を用いて浴槽での浴槽水の加熱や暖房ユニットでの暖房を行う利用側熱交換器を循環するための回路等には、それぞれに循環ポンプを設けなければならなかった。
【０００５】
そこで、本発明は、一つの循環ポンプを用いて、給湯タンクの沸き上げ運転と浴槽水の加熱運転や暖房運転とを行うことができる給湯機を提供することを目的とする。
【０００６】
【課題を解決するための手段】
請求項１記載の本発明の給湯機は、温水を貯留させる給湯タンクと、前記給湯タンク内の水と冷媒とを熱交換する給湯用熱交換器と、前記給湯タンク内の温水の放熱を行う利用側熱交換器とを備え、前記給湯タンクから流出する湯水の流路で前記利用側熱交換器の入口側を前記給湯タンクの上部に接続し、前記利用側熱交換器の出口側を前記給湯タンクの下部に第１の制御弁を介して接続するとともに、前記給湯タンクから流出する湯水の流路で前記給湯用熱交換器の入口側を前記給湯タンクの下部に前記第１の制御弁を介して接続し、前記給湯用熱交換器の出口側を前記給湯タンクの上部および下部に第２の制御弁を介して接続するとともに、前記第１の制御弁と前記第２の制御弁との間に循環ポンプと、前記循環ポンプの下流側に第３の制御弁と、前記第３の制御弁と前記第２の制御弁の上流側とを接続したバイパス管とを設け、前記第１の制御弁および前記第２の制御弁および前記第３の制御弁を切り替えて、前記循環ポンプを動作させることで、前記給湯用熱交換器を利用した沸き上げ運転または前記利用側熱交換器を利用した放熱運転を行うことを特徴とする。
請求項２記載の本発明は、請求項１に記載の給湯機において、第２の制御弁と給湯タンクの下部とを接続する下部戻し管を備え、給湯タンクの上部と下部との間で、異なる高さ位置に前記下部戻し管を複数設けたことを特徴とする。
請求項３記載の本発明は、請求項２に記載の給湯機において、前記給湯タンクの上部と下部との間で、異なる高さ位置の温度を検出する給湯温度センサを設け、給湯温度センサで検出した給湯温度に応じて前記下部戻し管を選択的に用いることを特徴とする。
請求項４記載の本発明の給湯機は、請求項２に記載の給湯機において、前記下部戻し管を流れる水温に応じて前記下部戻し管を選択的に用いることを特徴とする。
【０００７】
【発明の実施の形態】
本発明による第１の実施の形態による給湯機は、温水を貯留させる給湯タンクと、前記給湯タンク内の水と冷媒とを熱交換する給湯用熱交換器と、前記給湯タンク内の温水の放熱を行う利用側熱交換器とを備え、前記給湯タンクから流出する湯水の流路で前記利用側熱交換器の入口側を前記給湯タンクの上部に接続し、前記利用側熱交換器の出口側を前記給湯タンクの下部に第１の制御弁を介して接続するとともに、前記給湯タンクから流出する湯水の流路で前記給湯用熱交換器の入口側を前記給湯タンクの下部に前記第１の制御弁を介して接続し、前記給湯用熱交換器の出口側を前記給湯タンクの上部および下部に第２の制御弁を介して接続するとともに、前記第１の制御弁と前記第２の制御弁との間に循環ポンプと、前記循環ポンプの下流側に第３の制御弁と、前記第３の制御弁と前記第２の制御弁の上流側とを接続したバイパス管とを設け、前記第１の制御弁および前記第２の制御弁および前記第３の制御弁を切り替えて、前記循環ポンプを動作させることで、前記給湯用熱交換器を利用した沸き上げ運転または前記利用側熱交換器を利用した放熱運転を行うものである。本実施の形態によれば、第１の制御弁と第２の制御弁および第３の制御弁を切り替えるだけで、一つの循環ポンプを用いて、給湯タンクの沸き上げ運転と浴槽水の加熱運転や暖房運転とを行うことができるとともに、給湯用熱交換器をバイパスさせて給湯タンクに温水を戻すため、給湯用熱交換器での無駄な放熱を防止することができる。
本発明による第２の実施の形態は、第１の実施の形態による給湯機において、第２の制御弁と給湯タンクの下部とを接続する下部戻し管を備え、給湯タンクの上部と下部との間で、異なる高さ位置に前記下部戻し管を複数設けたものである。本実施の形態によれば、給湯タンク内の高温水が低温水と混ざり合わないように戻し口を選択することができる。
本発明による第３の実施の形態は、第２の実施の形態による給湯機において、前記給湯タンクの上部と下部との間で、異なる高さ位置の温度を検出する給湯温度センサを設け、給湯温度センサで検出した給湯温度に応じて前記下部戻し管を選択的に用いるものである。本実施の形態によれば、給湯温度センサによって給湯タンク内の温度分布を正確に把握でき、給湯タンク内の温度状況に応じた戻し口を選択でき、給湯タンク内の高温水が低温水と混ざり合うことを防止できる。
本発明による第４の実施の形態は、第２の実施の形態による給湯機において、下部戻し管を流れる水温に応じて前記下部戻し管を選択的に用いるものである。本実施の形態によれば、給湯タンク内の温度状況に応じた戻し口を選択でき、給湯タンク内の高温水が低温水と混ざり合うことを防止できる。
【０００８】
【実施例】
以下、本発明の一実施例による給湯機について図面を用いて説明する。
図１は、本実施例による給湯機の回路構成図である。
本実施例による給湯機は、給湯ユニット１０と、ヒートポンプユニット６０と、浴槽７０とから構成される。
給湯ユニット１０は、温水を貯留する給湯タンク１１と、給湯タンク１１の低温水をヒートポンプユニット６０に導き、このヒートポンプユニット６０で加熱した温水を給湯タンク１１に戻すための循環ポンプ１２と、給湯タンク１１内の温水を浴槽７０で利用するための利用側熱交換器１３とを備えている。
ヒートポンプユニット６０は、圧縮機６１、給湯用熱交換器６２、膨張弁６３、蒸発器６４を配管にて環状に接続し、冷凍サイクルを構成している。給湯用熱交換器６２は、冷凍サイクルを構成する熱源側配管と給湯ユニット１０を構成する利用側配管との間で熱交換を行う。利用側配管側で高温水を得るためには、冷凍サイクルは、冷媒として二酸化炭素を用い、臨界圧を越える圧力で運転することが好ましい。
浴槽７０は、利用側熱交換器１３の利用側配管と循環ポンプ７１とともに、浴槽用配管７２にて環状に接続した温水回路を備えている。
【０００９】
給湯用配管４１は、一端が給湯タンク１１の底部に接続され、給湯用熱交換器６２の利用側配管を構成し、他端が給湯タンク１１の上部に接続され、管路中に循環ポンプ１２を備えている。給湯用配管４１の一端側には、給湯タンク１１内の貯留水の流出を制御する三方弁３３が設けられている。この三方弁３３と給湯用熱交換器６２との間の給湯用配管４１には、循環ポンプ１２が設けられている。一方、給湯用管４１の他端側、すなわち給湯用熱交換器６２と給湯用タンク１１との間の給湯用配管４１には、三方弁３４が設けられている。そしてこの三方弁３４の他方の流出側開口には、給湯タンク１１の下部に接続される下部戻し管５７が設けられている。
二方弁２４は、一方に水道管等の水供給配管を接続し、他方に給湯ユニット１０内の出水配管４３を接続している。
混合弁２５は、一方の流入側接続口に出湯配管４２を接続し、他方の流入側接続口に出水配管４３を接続し、流出側接続口に第１利用側配管４４を接続している。
なお、出湯配管４２の一端は、給湯タンク１１の上部に接続されている。また第１利用側配管４４の一端は、浴室、キッチン、又は洗面所等の給湯用の蛇口に接続されている。給水配管４５は、出水配管４３の途中から分岐し、給湯タンク１１の底部に接続されている。
【００１０】
熱源側配管４６は、一端が給湯タンク１１の上部に接続され、利用側熱交換器１３の熱源側配管を構成し、他端が三方弁３３の流入側接続口に接続されている。熱源側配管４６には、流量制御弁２６が設けられている。
なお、熱源側配管４６は、利用側熱交換器１３の上流側に温度センサ９１を、利用側熱交換器１３の下流側に温度センサ９２を設けている。また、浴槽用配管７２は、利用側熱交換器１３の上流側に温度センサ９３を設けている。また熱源側配管４６は、流量センサ９４を設けている。
浴槽７０内に注湯する注湯機能は、出水配管４３から分岐させた冷水側注湯用配管５４Ａと、出湯配管４２から分岐させた温水側注湯用配管５４Ｂと、冷水側注湯用配管５４Ａと温水側注湯用配管５４Ｂとを流入側接続口に接続する混合弁５３と、混合弁５３の流出側接続口に接続される注湯用配管５５と、この注湯用配管５５に設けた開閉弁５６とから構成され、注湯用配管５５は浴槽用配管７２に接続している。
【００１１】
まず、図１を用いて給湯タンクの沸き上げ運転について説明する。
三方弁３３は、給湯タンク１１側配管と給湯用配管４１を連通させ、熱源側配管４６の流入側接続口を閉とする。また三方弁３４は、給湯用配管４１、すなわち給湯用熱交換器６２側の配管と給湯タンク１１の上部接続側配管とを連通させ、下部戻し管５７への流出側接続口を閉とする。
従って、循環ポンプ１２を運転することにより、給湯タンク１１の下部から流出する水は、三方弁３３、循環ポンプ１２、給湯用熱交換器６２、三方弁３４を順に通り、再び給湯タンク１１の上部から流入する。
一方、ヒートポンプユニット６０も運転を行う。圧縮機６１で圧縮された冷媒は、給湯用熱交換器６２で放熱し、膨張弁６３で減圧された後、蒸発器６４にて吸熱し、ガス状態で圧縮機６１に吸入される。
従って、給湯用熱交換器６２では、冷凍サイクルを流れる冷媒の熱が給湯用配管４１を流れる水に伝達し、加熱された水は温水となり給湯タンク１１内に蓄えられる。このとき、温水は給湯タンク１１の上部から流入させ、冷水は給湯タンク１１の下部から流出させるため、給湯タンク１１内では、上層部に温水が蓄えられ、この温水層が徐々に厚くなる。そして給湯タンク１１の下部側に設けた温度センサ（図示しない）によって、給湯タンク１１内に十分な温水が蓄積された状態を検知し、沸き上げ運転を終了する。
【００１２】
次に、給湯タンク内の温水を給湯用として利用する場合の給湯運転について説明する。
第１利用側配管４４に接続された蛇口を開くことで給湯水を利用することができる。給湯温度は、混合弁２５の流入側流路の混合比を変更することで調整される。給湯温度を高くする場合には、出湯配管４２からの流入量を増加させ、給湯温度を低くする場合には、出水配管４３からの流入量を増加させる。
給湯タンク１１内は、出湯配管４２から温水が流出することで圧力が低下する。従って、出湯配管４２からの温水の流出量だけ、給水配管４５から給湯タンク１１内に水が流入する。そして、温度センサによって給湯タンク１１内の温水量が所定量よりも少なくなったことを検知した場合には、沸き上げ運転を再開する。
【００１３】
次に、給湯タンク内の温水を利用した浴槽水沸き上げ運転について説明する。
この浴槽水沸き上げ運転では、三方弁３３は、給湯タンク１１からの流入側接続口を閉とし、熱源側配管４６と給湯用配管４１とを連通させる。また、三方弁３４は、下部戻し管５７への流出側開口を開とし、給湯タンク１１の上部への流れを阻止する。
従って、循環ポンプ１２を運転することにより、給湯タンク１１の上部から流出する温水は、利用側熱交換器１３、三方弁３３、循環ポンプ１２、給湯用熱交換器６２、三方弁３４、下部戻し管５７を順に通り、給湯タンク１１の下部から流入する。
なお、ヒートポンプユニット６０は運転を停止しておく。
一方、浴槽７０は運転を行う。循環ポンプ７１を運転することで、利用側熱交換器１３では、熱源側配管４６を流れる温水の熱が、浴槽用配管７２を流れる水に伝達し、加熱された水は温水となり浴槽７０を循環する。このとき、温水は給湯タンク１１の上部から流入させ、利用側熱交換器１３で熱を奪われた低温水は給湯タンク１１の下部から流出させるため、給湯タンク１１内では、温水層が徐々に薄くなる。そして給湯タンク１１の上部側に設けた温度センサ（図示しない）によって、給湯タンク１１内の温水量が所定量以下となった状態を検知した場合には、沸き上げ運転を再開するか、又はヒートポンプを利用した浴槽水沸き上げ運転に切り替えることで浴槽水沸き上げ運転を継続する。
【００１４】
次に、ヒートポンプを利用した浴槽水沸き上げ運転について説明する。
このヒートポンプを利用した浴槽水沸き上げ運転では、三方弁３３の流入側接続口は熱源側配管４６を連通させ、三方弁３４の流出側接続口は熱源側配管４６、すなわち給湯タンク１１の上部に接続された配管側を連通させる。
一方、ヒートポンプユニット６０も運転を行う。圧縮機６１で圧縮された冷媒は、給湯用熱交換器６２で放熱し、膨張弁６３で減圧された後、蒸発器６４にて吸熱し、ガス状態で圧縮機６１に吸入される。
従って、循環ポンプ１２を運転することにより、利用側熱交換器１３を通った低温水は、三方弁３３、循環ポンプ１２を通って給湯用熱交換器６２に流入する。そして、給湯用熱交換器６２で加熱された高温水は、三方弁３４を経由して給湯タンク１１の上部から流入する。なお、熱源側配管４６によって給湯タンク１１の上部から流出する高温水が利用側熱交換器１３に流入する。
また、浴槽７０も運転を行う。循環ポンプ７１を運転することで、利用側熱交換器１３では、熱源側配管４６を流れる温水の熱が浴槽用配管７２を流れる水に伝達し、加熱された水は温水となり浴槽７０側を循環する。
【００１５】
次に、給湯タンク１１に貯留させた温水を浴槽７０内に注湯する注湯運転について説明する。
開閉弁５６を開放することで、冷水側注湯用配管５４Ａからは水道管等の水供給配管からの水が導入され、温水側注湯用配管５４Ｂからは給湯タンク１１の上部の高温水が導入される。
給湯タンク１１内は、給湯用配管４１から温水が流出することで圧力が低下する。従って、給湯用配管４１からの温水の流出量だけ、給水配管４５から給湯タンク１１内に水が流入する。
冷水側注湯用配管５４Ａから導入される水と、温水側注湯用配管５４Ｂから導入される温水とは、混合弁７３によって設定温度に調整され、注湯用配管５５を経由して、浴槽用配管７２から浴槽７０内に導入される。
なお、この場合の給湯用熱交換器６２での能力と浴槽７０での暖房負荷との関係は、温度センサ９２での検出温度で判定できる他、温度センサ９１と温度センサ９２との検出温度から更に正確に判定することができる。
【００１６】
以下、本発明の他の実施例による給湯機について図面を用いて説明する。なお、同一機能を有する部材には同一番号を付して説明を省略する。
図２は、本実施例による給湯機の回路構成図である。
本実施例による給湯機は、出湯配管として、給湯タンク１１の上部に接続された第１の出湯配管４２Ａの他に、給湯タンク１１の上部と下部との間に接続された、第２の出湯配管４２Ｂ及び第３の出湯配管４２Ｃとを備えている。本実施例では、給湯タンク１１の上部と下部との間に２つの出湯配管４２Ｂ、４２Ｃを設けたものを示しているが、更に多くの出湯配管を高さ方向の位置を異ならせて設けてもよい。本実施例では、第２の出湯配管４２Ｂは、第３の出湯配管４２Ｃよりも高い位置に設けている。また第１の出湯配管４２Ａには開閉弁３１Ａを、第２の出湯配管４２Ｂには開閉弁３１Ｂを、第３の出湯配管４２Ｃには開閉弁３１Ｃを設け、これら開閉弁３１Ａ、３１Ｂ、３１Ｃの開閉動作によって、少なくともいずれか一つの出湯配管４２Ａ、４２Ｂ、４２Ｃから温水を流出させている。
また、本実施例による給湯機は、下部戻し管５７として、給湯タンク１１の上部と下部との間に接続された、第１の下部戻し管５７Ａ及び第２の下部戻し管５７Ｂと、給湯タンク１１の下部に接続された第３の下部戻し管５７Ｃを備えている。本実施例では、下部戻し管として給湯タンク１１の上部と下部との間に２つの下部戻し管５７Ａ、５７Ｂを設けたものを示しているが、更に多くの下部戻し管５７を高さ方向の位置を異ならせて設けてもよい。本実施例では、第１の下部戻し管５７Ａは、第２の下部戻し管５７Ｂよりも高い位置に設けている。また第１の下部戻し管５７Ａには開閉弁３５Ａを、第２の下部戻し管５７Ｂには開閉弁３５Ｂを、第３の下部戻し管５７Ｃには開閉弁３５Ｃを設け、これら開閉弁３５Ａ、３５Ｂ、３５Ｃの開閉動作によって、少なくともいずれか一つの下部戻し管５７Ａ、５７Ｂ、５７Ｃから低温水を流入させている。
【００１７】
本実施例のように、出湯配管として、給湯タンク１１の上部に接続された第１の出湯配管４２Ａの他に、給湯タンク１１の上部と下部との間に複数の出湯配管４２Ｂ、４２Ｃを設けることで、第１利用側配管４４での利用温度又は設定温度に応じた温度の温水を供給することができる。従って、給湯タンク１１の上部に貯留されている高温の温水を温存することができる。なお、図示はしないが、給湯温度センサを、給湯タンク１１の上部と下部との間で、異なる高さ位置に複数設けることが好ましい。
以上のように本実施例によれば、給湯タンク１１の上部と下部との間で、異なる高さ位置から温水を流出させる出湯配管４２Ｂ、４２Ｃを設け、出湯配管４２Ｂ、４２Ｃの流出口を、給湯温度センサで検出した給湯温度に応じて高さ位置を異ならせることで、給湯タンク１１から流出させる温水を、利用側の要望に合わせた温度の温水を用いることができるため、高温水を不必要に用いることなく、給湯タンク１１内に、より高温の温水を温存することができる。
【００１８】
また本実施例のように、下部戻し管５７として、給湯タンク１１の下部に接続された第３の下部戻し管５７Ｃの他に、給湯タンク１１の上部と下部との間に複数の下部戻し管５７Ａ、５７Ｂを設けることで、図１に示す給湯タンク内の温水を利用した浴槽水沸き上げ運転において、利用側熱交換器１３での負荷に応じて、熱源側配管４６から戻ってくる温水の温度に応じて、給湯タンク１１内に温水を流入させることができる。
以上のように本実施例によれば、利用側熱交換器１３で放熱した低温水の流入によって給湯タンク１１内の温度の異なる温水が混ざり合うことを防止できるとともに、利用側熱交換器１３で放熱した低温水の熱も有効に利用することができ、給湯タンク１１内の上部と下部とで湯温差が生じるように給湯水を貯留することができる。
また、給湯温度センサを給湯タンク１１への流入と、給湯タンク１１からの流出の両方に利用することで、給湯タンク１１内の温度差を確保して、より高温の温水を温存することができる。従って、給湯タンクの小型化が実現でき、小型の給湯タンクであっても、高温水を有効に利用することができる。
【００１９】
図３は、更に他の実施例による給湯機の回路構成図である。
本実施例による給湯機は、図１に示す実施例に、更に三方弁３６とバイパス管５８とを設けたものである。
三方弁３６は、循環ポンプ１２の流出側配管であって、給湯ユニット１０内に配置される給湯用配管４１に設けられている。そして、この三方弁の他方の流出側開口には、バイパス管５８が設けられ、このバイパス管５８の他端は、三方弁３４の流入側配管であって、給湯ユニット１０内に配置される給湯用配管４１に設けられている。
本実施例では、給湯タンク内の温水を利用した浴槽水沸き上げ運転において、循環ポンプ１２から流出した温水を、給湯用熱交換器６２に流入させることなく、バイパス管５８側に流し、三方弁３４を介して下部戻し管５７に流すものである。
本実施例のように、給湯タンク内の温水を利用した浴槽水沸き上げ運転において、給湯用熱交換器６２に温水を流すことなく、給湯ユニット１０内の配管を経由して給湯タンク１１に戻すことによって、放熱による熱ロスを少なくすることができる。
【００２０】
図４は、更に他の実施例による給湯機の回路構成図である。
本実施例による給湯機は、上記実施例で説明したヒートポンプユニット６０を設ける代わりに、給湯用熱交換器６２Ａを給湯タンク１１内に設けたものである。
給湯用配管４１Ａは、一端が給湯タンク１１の底部に接続され、他端が給湯タンク１１の上部に接続され、管路中に循環ポンプ１２を備えている。給湯用配管４１Ａの一端側には、給湯タンク１１内の貯留水の流出を制御する三方弁３３が設けられている。
【００２１】
まず、給湯タンクの沸き上げ運転について説明する。
三方弁３３は、給湯タンク１１側配管と給湯用配管４１を連通させ、熱源側配管４６の流入側接続口を閉とする。そして給湯用熱交換器６２の電源をオンする。
従って、循環ポンプ１２を運転することにより、給湯タンク１１の下部から流出する水は、給湯タンク１１の上部から流入し、給湯用熱交換器６２によって加熱される。このとき、給湯タンク１１の上部で加熱され、冷水は給湯タンク１１の下部から流出させるため、給湯タンク１１内では、上層部に温水が蓄えられ、この温水層が徐々に厚くなる。そして給湯タンク１１の下部側に設けた温度センサ（図示しない）によって、給湯タンク１１内に十分な温水が蓄積された状態を検知し、沸き上げ運転を終了する。
【００２２】
次に、給湯タンク内の温水を利用した浴槽水沸き上げ運転について説明する。
この浴槽水沸き上げ運転では、三方弁３３は、給湯タンク１１からの流入側接続口を閉とし、熱源側配管４６と給湯用配管４１とを連通させる。
従って、循環ポンプ１２を運転することにより、給湯タンク１１の上部から流出する温水は、利用側熱交換器１３、三方弁３３、循環ポンプ１２を順に通り、給湯タンク１１の上部から流入する。なお、給湯用熱交換器６２Ａの電源はオンにしておく。
【００２３】
【発明の効果】
本発明によれば、一つの循環ポンプを用いて、給湯タンクの沸き上げ運転と浴槽水の加熱運転や暖房運転とを行うことができる。
【図面の簡単な説明】
【図１】本発明の一実施例による給湯機の回路構成図
【図２】本発明の他の実施例による給湯機の回路構成図
【図３】本発明の更に他の実施例による給湯機の回路構成図
【図４】本発明の更に他の実施例による給湯機の回路構成図
【符号の説明】
１０給湯ユニット
１１給湯タンク
１２循環ポンプ
１３暖房用熱交換器
３３三方弁
３４三方弁
３６三方弁
５７下部戻し管
５８バイパス管
７１循環ポンプ
６０ヒートポンプユニット
７０浴槽[0001]
BACKGROUND OF THE INVENTION
In the present invention, hot water heated by a hot water supply heat exchanger is introduced from the upper part of the hot water supply tank, and cold water is introduced from the lower part of the hot water supply tank so that a hot water temperature difference is generated between the upper part and the lower part in the hot water supply tank. The present invention relates to a water heater that stores hot water.
[0002]
[Prior art]
Conventionally, a heat pump type hot water heater using a refrigeration cycle has been proposed, for example, one that stores hot water in a hot water supply tank using a refrigeration cycle or one that supplies hot water to a bathtub (for example, (See Patent Document 1 and Patent Document 2).
[0003]
[Patent Document 1]
JP 2002-130819 A [Patent Document 2]
Japanese Patent Laid-Open No. 2002-243274 [0004]
[Problems to be solved by the invention]
However, conventionally, a circuit for circulating a hot water heat exchanger that heats the water in the hot water tank, or heating the bathtub water in the bathtub or heating in the heating unit using the hot water in the hot water tank A circuit or the like for circulating the side heat exchanger had to be provided with a circulation pump for each.
[0005]
Therefore, an object of the present invention is to provide a water heater capable of performing a heating operation of a hot water tank, a heating operation of a bath water, and a heating operation using a single circulation pump.
[0006]
[Means for Solving the Problems]
The hot water heater of the present invention according to claim 1 performs a heat dissipation of hot water in the hot water tank, a hot water tank for storing hot water, a hot water heat exchanger for exchanging heat between water and refrigerant in the hot water tank, and the hot water in the hot water tank. A use-side heat exchanger, and an inlet side of the use-side heat exchanger is connected to an upper portion of the hot-water supply tank in a flow path of hot water flowing out of the hot-water tank, and an outlet side of the use-side heat exchanger is The first control valve is connected to the lower part of the hot water tank via a first control valve, and the inlet side of the hot water heat exchanger is connected to the lower part of the hot water tank in the flow path of hot water flowing out of the hot water tank. And the outlet side of the hot water supply heat exchanger is connected to the upper and lower parts of the hot water supply tank via a second control valve, and the first control valve and the second control valve, Between the circulation pump and the third downstream of the circulation pump And a bypass pipe connecting the third control valve and the upstream side of the second control valve, and the first control valve, the second control valve, and the third control valve. And the circulation pump is operated to perform a boiling operation using the hot water supply heat exchanger or a heat radiation operation using the use side heat exchanger .
The present invention described in claim 2 is the water heater according to claim 1, further comprising a lower return pipe connecting the second control valve and the lower part of the hot water tank, between the upper part and the lower part of the hot water tank, A plurality of the lower return pipes are provided at different height positions.
According to a third aspect of the present invention, in the hot water supply apparatus according to the second aspect, a hot water supply temperature sensor for detecting temperatures at different height positions is provided between an upper part and a lower part of the hot water tank, The lower return pipe is selectively used according to the detected hot water supply temperature .
According to a fourth aspect of the present invention, there is provided the hot water supply apparatus according to the second aspect, wherein the lower return pipe is selectively used according to a water temperature flowing through the lower return pipe .
[0007]
DETAILED DESCRIPTION OF THE INVENTION
A water heater according to a first embodiment of the present invention includes a hot water tank for storing hot water , a hot water heat exchanger for exchanging heat between the water in the hot water tank and the refrigerant, and heat dissipation from the hot water in the hot water tank. A user-side heat exchanger that connects the inlet side of the user-side heat exchanger to the upper part of the hot-water tank in a flow path of hot water flowing out of the hot-water tank, and the outlet side of the user-side heat exchanger Is connected to the lower part of the hot water tank via a first control valve, and the inlet side of the hot water heat exchanger is connected to the lower part of the hot water tank in the flow path of hot water flowing out of the hot water tank. And connecting the outlet side of the hot water supply heat exchanger to the upper and lower portions of the hot water supply tank via a second control valve, and the first control valve and the second control. A circulation pump between the valve and the circulation pump A third control valve, and a bypass pipe connecting the third control valve and the upstream side of the second control valve are provided on the side, the first control valve, the second control valve, and the By switching the third control valve and operating the circulation pump, a boiling operation using the hot water supply heat exchanger or a heat radiation operation using the use side heat exchanger is performed . According to the present embodiment, only by switching the first control valve, the second control valve, and the third control valve , the hot water tank heating operation and the bath water heating operation are performed using one circulation pump. In addition, the hot water supply heat exchanger is bypassed and the hot water is returned to the hot water supply tank, so that useless heat dissipation in the hot water supply heat exchanger can be prevented .
The second embodiment according to the present invention includes a lower return pipe that connects the second control valve and a lower portion of the hot water tank in the hot water heater according to the first embodiment, and includes an upper portion and a lower portion of the hot water tank. A plurality of the lower return pipes are provided at different height positions . According to the present embodiment , the return port can be selected so that the high temperature water in the hot water supply tank does not mix with the low temperature water.
According to a third embodiment of the present invention, in the hot water supply apparatus according to the second embodiment, a hot water supply temperature sensor for detecting temperatures at different height positions is provided between an upper part and a lower part of the hot water tank, The lower return pipe is selectively used according to the hot water temperature detected by the temperature sensor . According to this embodiment , the temperature distribution in the hot water tank can be accurately grasped by the hot water temperature sensor, the return port according to the temperature condition in the hot water tank can be selected, and the hot water in the hot water tank is mixed with the low temperature water. It can prevent fitting.
According to a fourth embodiment of the present invention , in the water heater according to the second embodiment, the lower return pipe is selectively used according to the water temperature flowing through the lower return pipe . According to the present embodiment, it is possible to select a return port according to the temperature condition in the hot water supply tank, and it is possible to prevent high temperature water in the hot water supply tank from being mixed with low temperature water.
[0008]
【Example】
Hereinafter, a water heater according to an embodiment of the present invention will be described with reference to the drawings.
FIG. 1 is a circuit configuration diagram of a water heater according to the present embodiment.
The water heater according to the present embodiment includes a hot water supply unit 10, a heat pump unit 60, and a bathtub 70.
The hot water supply unit 10 includes a hot water tank 11 for storing hot water, a circulation pump 12 for guiding the low temperature water in the hot water tank 11 to the heat pump unit 60, and returning the hot water heated by the heat pump unit 60 to the hot water tank 11, and a hot water tank. 11 and the use side heat exchanger 13 for using the hot water in the bathtub 70.
The heat pump unit 60 includes a compressor 61, a hot water supply heat exchanger 62, an expansion valve 63, and an evaporator 64 connected in a ring shape through a pipe to constitute a refrigeration cycle. The hot water supply heat exchanger 62 performs heat exchange between the heat source side pipe constituting the refrigeration cycle and the use side pipe constituting the hot water supply unit 10. In order to obtain high-temperature water on the use side piping side, the refrigeration cycle is preferably operated at a pressure exceeding the critical pressure using carbon dioxide as a refrigerant.
The bathtub 70 includes a hot water circuit connected in a ring shape by a bathtub pipe 72 together with the use side pipe of the use side heat exchanger 13 and the circulation pump 71.
[0009]
One end of the hot water supply pipe 41 is connected to the bottom of the hot water supply tank 11 and constitutes a use side pipe of the hot water supply heat exchanger 62, and the other end is connected to the upper part of the hot water supply tank 11. It has. A three-way valve 33 that controls the outflow of stored water in the hot water supply tank 11 is provided on one end side of the hot water supply pipe 41. A circulation pump 12 is provided in a hot water supply pipe 41 between the three-way valve 33 and the hot water supply heat exchanger 62. On the other hand, a three-way valve 34 is provided on the other end side of the hot water supply pipe 41, that is, on the hot water supply pipe 41 between the hot water supply heat exchanger 62 and the hot water supply tank 11. A lower return pipe 57 connected to the lower part of the hot water supply tank 11 is provided at the other outlet side opening of the three-way valve 34.
The two-way valve 24 has a water supply pipe such as a water pipe connected to one side and a water discharge pipe 43 in the hot water supply unit 10 connected to the other side.
The mixing valve 25 has a hot water supply pipe 42 connected to one inflow side connection port, a water discharge pipe 43 connected to the other inflow side connection port, and a first usage side pipe 44 connected to the outflow side connection port.
One end of the hot water supply pipe 42 is connected to the upper part of the hot water supply tank 11. In addition, one end of the first use side pipe 44 is connected to a faucet for hot water supply such as a bathroom, a kitchen, or a bathroom. The water supply pipe 45 is branched from the middle of the water discharge pipe 43 and is connected to the bottom of the hot water supply tank 11.
[0010]
One end of the heat source side pipe 46 is connected to the upper part of the hot water supply tank 11, constitutes the heat source side pipe of the use side heat exchanger 13, and the other end is connected to the inflow side connection port of the three-way valve 33. A flow control valve 26 is provided in the heat source side pipe 46.
The heat source side pipe 46 is provided with a temperature sensor 91 on the upstream side of the use side heat exchanger 13 and a temperature sensor 92 on the downstream side of the use side heat exchanger 13. Further, the bathtub pipe 72 is provided with a temperature sensor 93 on the upstream side of the use side heat exchanger 13. The heat source side piping 46 is provided with a flow rate sensor 94.
The hot water pouring function for pouring into the bathtub 70 includes a cold water side pouring pipe 54A branched from the outlet pipe 43, a hot water side pouring pipe 54B branched from the outlet pipe 42, and a cold water side pouring pipe. 54A and hot water side pouring pipe 54B are connected to the inflow side connection port, a pouring pipe 55 is connected to the outflow side connection port of the mixing valve 53, and this pouring pipe 55 is provided. The pouring pipe 55 is connected to the bathtub pipe 72.
[0011]
First, the heating operation of the hot water supply tank will be described with reference to FIG.
The three-way valve 33 communicates the hot water supply tank 11 side pipe with the hot water supply pipe 41 and closes the inflow side connection port of the heat source side pipe 46. The three-way valve 34 connects the hot water supply pipe 41, that is, the hot water supply heat exchanger 62 side pipe and the upper connection side pipe of the hot water tank 11, and closes the outflow side connection port to the lower return pipe 57.
Accordingly, when the circulation pump 12 is operated, the water flowing out from the lower portion of the hot water supply tank 11 sequentially passes through the three-way valve 33, the circulation pump 12, the hot water supply heat exchanger 62, and the three-way valve 34, and again in the upper portion of the hot water supply tank 11. Inflow from.
On the other hand, the heat pump unit 60 also operates. The refrigerant compressed by the compressor 61 radiates heat by the hot water supply heat exchanger 62, is decompressed by the expansion valve 63, absorbs heat by the evaporator 64, and is sucked into the compressor 61 in a gas state.
Therefore, in the hot water supply heat exchanger 62, the heat of the refrigerant flowing through the refrigeration cycle is transmitted to the water flowing through the hot water supply pipe 41, and the heated water becomes warm water and is stored in the hot water supply tank 11. At this time, since hot water flows in from the upper part of the hot water supply tank 11 and cold water flows out from the lower part of the hot water supply tank 11, the hot water is stored in the upper layer in the hot water supply tank 11, and this hot water layer gradually thickens. Then, a temperature sensor (not shown) provided on the lower side of the hot water supply tank 11 detects a state in which sufficient hot water is accumulated in the hot water supply tank 11 and ends the boiling operation.
[0012]
Next, a hot water supply operation when using hot water in the hot water supply tank for hot water supply will be described.
Hot water can be used by opening the faucet connected to the first usage side pipe 44. The hot water supply temperature is adjusted by changing the mixing ratio of the inflow side passage of the mixing valve 25. When the hot water supply temperature is increased, the inflow amount from the hot water supply pipe 42 is increased, and when the hot water supply temperature is decreased, the inflow amount from the water discharge pipe 43 is increased.
The pressure in the hot water supply tank 11 decreases as hot water flows out from the hot water supply pipe 42. Accordingly, water flows into the hot water supply tank 11 from the water supply pipe 45 by the amount of hot water flowing out from the hot water supply pipe 42. When the temperature sensor detects that the amount of hot water in the hot water supply tank 11 is less than a predetermined amount, the boiling operation is resumed.
[0013]
Next, a bath water heating operation using hot water in the hot water supply tank will be described.
In this bathtub water heating operation, the three-way valve 33 closes the inflow side connection port from the hot water supply tank 11 and connects the heat source side pipe 46 and the hot water supply pipe 41. Further, the three-way valve 34 opens the outflow side opening to the lower return pipe 57 and prevents the flow to the upper part of the hot water supply tank 11.
Accordingly, by operating the circulation pump 12, the hot water flowing out from the upper part of the hot water supply tank 11 is used on the use side heat exchanger 13, three-way valve 33, circulation pump 12, hot water supply heat exchanger 62, three-way valve 34, lower return. It passes through the pipe 57 in order and flows from the lower part of the hot water supply tank 11.
Note that the operation of the heat pump unit 60 is stopped.
On the other hand, the bathtub 70 operates. By operating the circulation pump 71, in the use side heat exchanger 13, the heat of the hot water flowing through the heat source side pipe 46 is transmitted to the water flowing through the bathtub pipe 72, and the heated water becomes hot water and circulates in the bathtub 70. To do. At this time, since hot water flows in from the upper part of the hot water supply tank 11 and low temperature water deprived of heat by the use side heat exchanger 13 flows out from the lower part of the hot water supply tank 11, the hot water layer gradually forms in the hot water supply tank 11. getting thin. When a temperature sensor (not shown) provided on the upper side of the hot water supply tank 11 detects that the amount of hot water in the hot water supply tank 11 is equal to or less than a predetermined amount, the boiling operation is restarted, or a heat pump The bath water heating operation is continued by switching to the bath water heating operation using the.
[0014]
Next, the bathtub water heating operation using a heat pump will be described.
In the bathtub water heating operation using this heat pump, the inflow side connection port of the three-way valve 33 communicates with the heat source side piping 46, and the outflow side connection port of the three-way valve 34 is connected to the heat source side piping 46, that is, the upper part of the hot water supply tank 11. Connect the connected piping side.
On the other hand, the heat pump unit 60 also operates. The refrigerant compressed by the compressor 61 radiates heat by the hot water supply heat exchanger 62, is decompressed by the expansion valve 63, absorbs heat by the evaporator 64, and is sucked into the compressor 61 in a gas state.
Therefore, by operating the circulation pump 12, the low-temperature water that has passed through the use side heat exchanger 13 flows into the hot water supply heat exchanger 62 through the three-way valve 33 and the circulation pump 12. The high-temperature water heated by the hot water supply heat exchanger 62 flows from the upper part of the hot water supply tank 11 via the three-way valve 34. In addition, the high temperature water which flows out from the upper part of the hot water supply tank 11 by the heat source side piping 46 flows into the use side heat exchanger 13.
The bathtub 70 also operates. By operating the circulation pump 71, in the use side heat exchanger 13, the heat of the hot water flowing through the heat source side pipe 46 is transferred to the water flowing through the bathtub pipe 72, and the heated water becomes hot water and circulates on the bathtub 70 side. To do.
[0015]
Next, a pouring operation for pouring hot water stored in the hot water supply tank 11 into the bathtub 70 will be described.
By opening the on-off valve 56, water from a water supply pipe such as a water pipe is introduced from the cold water side pouring pipe 54A, and hot water at the upper part of the hot water supply tank 11 is fed from the hot water side pouring pipe 54B. be introduced.
In the hot water supply tank 11, the pressure decreases as hot water flows out from the hot water supply pipe 41. Accordingly, water flows into the hot water supply tank 11 from the water supply pipe 45 by the amount of hot water flowing out from the hot water supply pipe 41.
The water introduced from the cold water side pouring pipe 54 A and the hot water introduced from the hot water side pouring pipe 54 B are adjusted to the set temperature by the mixing valve 73, via the pouring pipe 55, It is introduced into the bathtub 70 from the service pipe 72.
In this case, the relationship between the capacity of the hot water supply heat exchanger 62 and the heating load in the bathtub 70 can be determined by the temperature detected by the temperature sensor 92, and also from the temperature detected by the temperature sensor 91 and the temperature sensor 92. Further, it can be determined accurately.
[0016]
Hereinafter, a water heater according to another embodiment of the present invention will be described with reference to the drawings. In addition, the same number is attached | subjected to the member which has the same function, and description is abbreviate | omitted.
FIG. 2 is a circuit configuration diagram of the water heater according to the present embodiment.
The hot water supply apparatus according to the present embodiment has a second hot water supply pipe connected between the upper and lower parts of the hot water supply tank 11 in addition to the first hot water supply pipe 42A connected to the upper part of the hot water supply tank 11 as a hot water supply pipe. A pipe 42B and a third tapping pipe 42C are provided. In the present embodiment, two hot water supply pipes 42B and 42C are provided between the upper and lower portions of the hot water supply tank 11, but more hot water supply pipes are provided with different positions in the height direction. Also good. In the present embodiment, the second hot water piping 42B is provided at a position higher than the third hot water piping 42C. Also, the first hot water piping 42A is provided with an opening / closing valve 31A, the second hot water piping 42B is provided with an opening / closing valve 31B, and the third hot water piping 42C is provided with an opening / closing valve 31C, and these opening / closing valves 31A, 31B, 31C are provided. The hot water is caused to flow out from at least one of the hot water pipings 42A, 42B, 42C by the opening / closing operation.
Further, in the water heater according to the present embodiment, as the lower return pipe 57, the first lower return pipe 57A and the second lower return pipe 57B connected between the upper part and the lower part of the hot water tank 11, and the hot water tank 11 is provided with a third lower return pipe 57C connected to the lower portion. In the present embodiment, two lower return pipes 57A and 57B are provided as the lower return pipe between the upper and lower parts of the hot water tank 11, but more lower return pipes 57 in the height direction are shown. The positions may be provided differently. In the present embodiment, the first lower return pipe 57A is provided at a position higher than the second lower return pipe 57B. The first lower return pipe 57A is provided with an opening / closing valve 35A, the second lower return pipe 57B is provided with an opening / closing valve 35B, and the third lower return pipe 57C is provided with an opening / closing valve 35C. , 35C opens and closes low temperature water from at least one of the lower return pipes 57A, 57B, 57C.
[0017]
As in this embodiment, in addition to the first hot water supply pipe 42 A connected to the upper part of the hot water supply tank 11, a plurality of hot water supply pipes 42 B and 42 C are provided between the upper part and the lower part of the hot water supply tank 11. Thereby, the hot water of the temperature according to the utilization temperature or preset temperature in the 1st utilization side piping 44 can be supplied. Therefore, the hot water stored in the upper part of the hot water supply tank 11 can be preserved. Although not shown, it is preferable to provide a plurality of hot water temperature sensors at different height positions between the upper part and the lower part of the hot water tank 11.
As described above, according to the present embodiment, the hot water supply pipes 42B and 42C for allowing the hot water to flow out from different height positions are provided between the upper part and the lower part of the hot water supply tank 11, and the outlets of the hot water supply pipes 42B and 42C are provided. By changing the height position according to the hot water temperature detected by the hot water temperature sensor, it is possible to use hot water flowing out of the hot water tank 11 at a temperature that meets the demands of the user side. Higher temperature hot water can be preserved in the hot water supply tank 11 without using it as necessary.
[0018]
In addition to the third lower return pipe 57 C connected to the lower part of the hot water supply tank 11 as the lower return pipe 57 as in the present embodiment, a plurality of lower return pipes are provided between the upper part and the lower part of the hot water supply tank 11. By providing 57A and 57B, the hot water returning from the heat source side pipe 46 according to the load on the use side heat exchanger 13 in the bath water heating operation using the hot water in the hot water tank shown in FIG. Hot water can be allowed to flow into the hot water supply tank 11 in accordance with the temperature.
As described above, according to the present embodiment, hot water having different temperatures in the hot water supply tank 11 can be prevented from being mixed by the inflow of the low temperature water radiated by the use side heat exchanger 13, and at the use side heat exchanger 13. The heat of the radiated low-temperature water can also be used effectively, and hot water can be stored so that a hot water temperature difference is generated between the upper part and the lower part in the hot water tank 11.
Further, by using the hot water temperature sensor for both the inflow into the hot water supply tank 11 and the outflow from the hot water supply tank 11, a temperature difference in the hot water supply tank 11 can be secured, and hotter hot water can be preserved. . Therefore, the hot water tank can be miniaturized, and high-temperature water can be used effectively even with a small hot water tank.
[0019]
FIG. 3 is a circuit configuration diagram of a water heater according to still another embodiment.
The water heater according to this embodiment is obtained by further providing a three-way valve 36 and a bypass pipe 58 in the embodiment shown in FIG.
The three-way valve 36 is an outflow side pipe of the circulation pump 12 and is provided in a hot water supply pipe 41 arranged in the hot water supply unit 10. The other outflow side opening of the three-way valve is provided with a bypass pipe 58, and the other end of the bypass pipe 58 is an inflow side pipe of the three-way valve 34 and is disposed in the hot water supply unit 10. The pipe 41 is provided.
In the present embodiment, in the bathtub water heating operation using the hot water in the hot water tank, the hot water flowing out from the circulation pump 12 is caused to flow to the bypass pipe 58 side without flowing into the hot water heat exchanger 62, and the three-way valve The flow is made to flow through the lower return pipe 57 via 34.
In the bathtub water heating operation using the hot water in the hot water supply tank as in this embodiment, the hot water is returned to the hot water supply tank 11 via the piping in the hot water supply unit 10 without flowing the hot water through the hot water supply heat exchanger 62. Thus, heat loss due to heat radiation can be reduced.
[0020]
FIG. 4 is a circuit configuration diagram of a water heater according to still another embodiment.
The hot water supply apparatus according to this embodiment is provided with a hot water supply heat exchanger 62A in the hot water supply tank 11 instead of providing the heat pump unit 60 described in the above embodiment.
One end of the hot water supply pipe 41A is connected to the bottom of the hot water supply tank 11, the other end is connected to the upper part of the hot water supply tank 11, and the circulation pump 12 is provided in the pipeline. A three-way valve 33 that controls the outflow of stored water in the hot water supply tank 11 is provided on one end side of the hot water supply pipe 41 A.
[0021]
First, the boiling operation of the hot water supply tank will be described.
The three-way valve 33 communicates the hot water supply tank 11 side pipe with the hot water supply pipe 41 and closes the inflow side connection port of the heat source side pipe 46. Then, the power supply of the hot water supply heat exchanger 62 is turned on.
Accordingly, by operating the circulation pump 12, the water flowing out from the lower part of the hot water supply tank 11 flows from the upper part of the hot water supply tank 11 and is heated by the hot water supply heat exchanger 62. At this time, the hot water is heated in the upper part of the hot water supply tank 11 and the cold water flows out from the lower part of the hot water supply tank 11, so that the hot water is stored in the upper layer in the hot water supply tank 11, and this hot water layer becomes gradually thicker. Then, a temperature sensor (not shown) provided on the lower side of the hot water supply tank 11 detects a state in which sufficient hot water is accumulated in the hot water supply tank 11 and ends the boiling operation.
[0022]
Next, a bath water heating operation using hot water in the hot water supply tank will be described.
In this bathtub water heating operation, the three-way valve 33 closes the inflow side connection port from the hot water supply tank 11 and connects the heat source side pipe 46 and the hot water supply pipe 41.
Therefore, by operating the circulation pump 12, the hot water flowing out from the upper part of the hot water supply tank 11 passes through the use side heat exchanger 13, the three-way valve 33, and the circulation pump 12 in order and flows from the upper part of the hot water supply tank 11. The power supply for the hot water supply heat exchanger 62A is turned on.
[0023]
【The invention's effect】
ADVANTAGE OF THE INVENTION According to this invention, the boiling operation of a hot water supply tank, the heating operation of a bathtub water, and a heating operation can be performed using one circulation pump.
[Brief description of the drawings]
1 is a circuit configuration diagram of a water heater according to an embodiment of the present invention. FIG. 2 is a circuit configuration diagram of a water heater according to another embodiment of the present invention. FIG. 3 is a water heater according to still another embodiment of the present invention. FIG. 4 is a circuit configuration diagram of a water heater according to still another embodiment of the present invention.
DESCRIPTION OF SYMBOLS 10 Hot-water supply unit 11 Hot-water supply tank 12 Circulation pump 13 Heat exchanger for heating 33 Three-way valve 34 Three-way valve 36 Three-way valve 57 Lower return pipe 58 Bypass pipe 71 Circulation pump 60 Heat pump unit 70 Bathtub

Claims

A hot water supply tank for storing hot water, a hot water supply heat exchanger for exchanging heat between water and refrigerant in the hot water tank, and a use side heat exchanger for releasing heat of the hot water in the hot water tank ,
A first control is provided such that an inlet side of the use side heat exchanger is connected to an upper part of the hot water supply tank and an outlet side of the use side heat exchanger is connected to a lower part of the hot water supply tank through a flow path of hot water flowing out of the hot water tank. Connected via a valve,
The inlet side of the hot water supply heat exchanger is connected to the lower part of the hot water supply tank via the first control valve in the flow path of hot water flowing out from the hot water supply tank, and the outlet side of the hot water supply heat exchanger is While connecting to the upper and lower parts of the hot water tank via the second control valve,
A circulation pump between the first control valve and the second control valve; a third control valve downstream of the circulation pump; an upstream of the third control valve and the second control valve; A bypass pipe connected to the side,
By switching the first control valve, the second control valve, and the third control valve and operating the circulation pump, the boiling operation using the hot water supply heat exchanger or the use side heat is performed. A water heater that performs heat dissipation operation using an exchanger.

Includes a lower return conduit connecting the lower portion of the second control valve and the hot water tank, between the upper and lower hot water tank, wherein, characterized in that a plurality of said lower return pipe in different heights Item 2. A water heater according to item 1 .

A hot water supply temperature sensor that detects temperatures at different height positions is provided between an upper part and a lower part of the hot water tank, and the lower return pipe is selectively used according to the hot water temperature detected by the hot water temperature sensor. The water heater according to claim 2 .

The water heater according to claim 2 , wherein the lower return pipe is selectively used according to a temperature of water flowing through the lower return pipe.