JP2004037053A

JP2004037053A - Water heating system

Info

Publication number: JP2004037053A
Application number: JP2002198603A
Authority: JP
Inventors: Tomoaki Nishikawa; 西川　知明; Tetsuji Morita; 森田　哲司; Yuichi Murase; 村瀬　裕一
Original assignee: Osaka Gas Co Ltd; Noritz Corp
Current assignee: Osaka Gas Co Ltd; Noritz Corp
Priority date: 2002-07-08
Filing date: 2002-07-08
Publication date: 2004-02-05
Anticipated expiration: 2022-07-08
Also published as: JP3864116B2

Abstract

<P>PROBLEM TO BE SOLVED: To provide a water heating system capable of stably supplying hot water at a water heating set temperature even if a mixing control valve does not have a nearly linear mixing characteristic. <P>SOLUTION: This water heating system is provided with a solar water heater 10 having a heat storage vessel 14 for storing the pre-heated hot water generated by solar heating and a water heater 20 having a mixing control valve 21 for mixing the pre-heated hot water fed from the heat storage vessel 14 with the low-temperature water when necessary to feed it to a heat exchanger 22. In the mixing control valve 21, opening of the valve is controlled to the target mixing ratio, while computing a mixing ratio and a target mixing ratio, and when the valve is opened to the maximum opening, if the mixing ratio at that time is lower than the preset lowest mixing ratio, the valve is forcibly closed till the mixing ratio reaches the lowest mixing ratio. <P>COPYRIGHT: (C)2004,JPO

Description

【０００１】
【発明の属する技術分野】
この発明は、補助熱源によって生成された予熱温水を利用して給湯を行う給湯システムに関する。
【０００２】
【従来の技術】
補助熱源を利用した給湯システムとしては、例えば、補助熱源である太陽熱を利用して生成された予熱温水を貯留する蓄熱槽を備えている太陽熱利用温水器と、主熱源である給湯器とを組み合わせた給湯システムが従来から一般的に知られている。
【０００３】
こういった、給湯システムでは、太陽熱利用温水器の蓄熱槽と給湯器とが接続されており、出湯時には、太陽熱利用温水器の蓄熱槽に貯留された予熱温水が給湯器に送出されるようになっているが、蓄熱槽から送出される予熱温水をそのままの状態で熱交換器に送出するのではなく、必要に応じて、低温水（常水温の水道水または予熱温水より低い温度の水）を混合した状態で熱交換器に送出することができるように、蓄熱槽から送出される予熱温水と低温水とを任意の混合比率で混合するための混合調節弁が熱交換器の上流側に内蔵された給湯器を使用する場合があり、混合調節弁は、開弁するに従って予熱温水に対する低温水の混合比率が小さくなり、閉弁するに従って予熱温水に対する低温水の混合比率が大きくなるようになっている。
【０００４】
こういった混合調節弁が内蔵された給湯器を使用した給湯システムでは、給湯器に対して設定された給湯設定温度以上の予熱温水が蓄熱槽に貯留されている場合は、混合調節弁が、蓄熱槽から送出される給湯設定温度以上の予熱温水と低温水とを適宜混合することによって給湯設定温度の温水を生成し、これを熱交換器に送出することによって、熱交換器を加熱するバーナーを燃焼させることなく、給湯設定温度の温水を出湯することになる。一方、給湯設定温度以上の予熱温水が蓄熱槽に貯留されていない場合は、混合調節弁が、蓄熱槽から送出される給湯設定温度より低い予熱温水を低温水と適宜混合することによって予め定められた固定温度まで下げた状態で熱交換器に送出し、バーナーを燃焼させて熱交換器を加熱することによって、給湯設定温度の温水を生成しながら出湯することになる。
【０００５】
【発明が解決しようとする課題】
ところで、こういった給湯システムでは、良好な制御性を確保するため、低温水の供給圧と予熱温水の供給圧とが略同圧である場合に、図２に実線で示すように、予熱温水に対する低温水の混合比率が弁開度に対して略リニアに変化する混合特性を示す混合調節弁が使用されており、しかも、こういった給湯システムでは、制御タイミング毎に、その時点における予熱温水温度、低温水温度及び混合調節弁から送出される温水の温度に基づいて、その時点における混合比率を算出しているので、混合調節弁が最大開度まで開弁した状態においても、その状態での混合比率を算出することができるように、即ち、予熱温水温度と混合調節弁から送出される温水の温度との間に僅かな温度差が生じるように、低温水の供給圧と予熱温水の供給圧とが略同圧である場合の混合特性を前提として、最大開度時における最低混合比率が予め定められている。従って、低温水の供給圧と予熱温水の供給圧とが略同圧である状態で、給湯システムが使用される場合は、良好な制御性が確保されると共に、混合調節弁が最大開度まで開弁した状態であっても、そのときの混合比率が最低混合比率を下回ることはない。
【０００６】
しかしながら、実際は、低温水の供給圧と予熱温水の供給圧とが略同圧であるとは限らず、例えば、予熱温水の供給圧が低温水の供給圧よりも高い場合は、図２に一点鎖線で示すように、最大開度側において、弁開度の変化率に対する混合比率の変化率が小さく、しかも、最大開度まで開弁する前に最低混合比率を下回ってしまうような混合特性に変化してしまう場合があり、そのような場合は、以下に示すような問題が発生する。
【０００７】
例えば、蓄熱槽には、固定温度以上で給湯設定温度を下回る予熱温水が貯留されているが、蓄熱槽と給湯器とを接続する配管内に滞留している予熱温水の温度が固定温度以下に低下しているような状態で給湯を開始した場合、給湯開始当初は配管内に滞留していた固定温度以下の予熱温水が給湯器の混合調節弁に送出されるため、混合調節弁は固定温度の温水を生成しようとして最大開度まで開弁しているが、配管内に滞留していた固定温度以下の予熱温水が送出され終わって、蓄熱槽内に貯留されている固定温度を上回る予熱温水が送出されるようになると、混合調節弁は低温水を混合することによって固定温度の温水を生成しようとして閉弁し始める。
【０００８】
しかしながら、モータによる混合調節弁の開閉駆動速度が遅いために、上述したように、最大開度側において、弁開度の変化率に対する混合比率の変化率が小さく、しかも、最大開度まで開弁する前に最低混合比率を下回ってしまうような混合特性に変化している場合は、混合調節弁の閉弁動作が混合調節弁に送出される温水の急激な温度変化に追従できず、目標混合比率に到達するまでにある程度の時間がかかってしまい、その間は固定温度を上回る温水が熱交換器に送出されることになるので、バーナーが燃焼することによって給湯設定温度の温水を送出している給湯器が出湯温度制御を確実に行うことができなくなり、一時的に出湯温度が高くなってしまうという問題がある。
【０００９】
そこで、この発明の課題は、混合調節弁が略リニアな混合特性を有していない場合であっても、給湯設定温度の温水を安定して出湯することができる給湯システムを提供することにある。
【００１０】
【課題を解決するための手段及びその効果】
上記の課題を解決するため、請求項１にかかる発明は、補助熱源によって生成された予熱温水に、必要に応じて低温水を混合しながら、目標温度の温水を給湯器の熱交換器に送出する混合調節弁を備えた給湯システムにおいて、前記混合調節弁は、開弁するに従って予熱温水に対する低温水の混合比率が小さくなり、閉弁するに従って予熱温水に対する低温水の混合比率が大きくなるようになっており、前記混合調節弁は、制御タイミング毎に、その時点における予熱温水温度、低温水温度及び前記混合調節弁から送出されている温水の温度に基づいて、予熱温水に対する低温水の混合比率を算出すると共に、その時点における予熱温水温度、低温水温度及び目標温度に基づいて、予熱温水に対する低温水の目標混合比率を算出しながら、その目標混合比率になるように弁開度が制御されるようになっており、前記混合調節弁が最大開度まで開弁した時点で、そのときの予熱温水に対する低温水の混合比率が予め定められた最低混合比率を下回っている場合は、その最低混合比率になるまで、前記混合調節弁を強制的に閉弁するようにしたことを特徴とする給湯システムを提供するものである。
【００１１】
以上のように、この給湯システムでは、給湯開始直後に、配管内に滞留していた固定温度を下回る予熱温水が混合調節弁に送出され始めると、混合調節弁が一旦最大開度まで開弁することになるが、最大開度まで開弁した時点で、そのときの予熱温水に対する低温水の混合比率が予め定められた最低混合比率を下回っている場合は、混合調節弁が最低混合比率になるまで即座に閉弁することになるので、その後に、固定温度以上の予熱温水が混合調節弁に送出されるようになった時点で混合調節弁が閉弁動作を行う際、目標混合比率まで短時間で閉弁することができる。
【００１２】
従って、低温水の供給圧と予熱温水の供給圧とが異なるために、混合調節弁の混合特性が、最大開度側において、弁開度の変化率に対する混合比率の変化率が小さく、しかも、最大開度まで開弁する前に最低混合比率を下回ってしまうような混合特性に変化したような場合や低温水の供給圧と予熱温水の供給圧とが同圧であってもそういった混合特性を示すような廉価な混合調節弁を使用した場合であっても、混合調節弁に送出される予熱温水の急激な温度上昇にもある程度追従することができ、給湯開始から給湯設定温度の温水を安定して出湯することが可能となる。
【００１３】
また、上記の課題を解決するため、請求項２にかかる発明は、補助熱源によって生成された予熱温水に、必要に応じて低温水を混合しながら、目標温度の温水を給湯器の熱交換器に送出する混合調節弁を備えた給湯システムにおいて、前記混合調節弁は、開弁するに従って予熱温水に対する低温水の混合比率が小さくなり、閉弁するに従って予熱温水に対する低温水の混合比率が大きくなるようになっており、前記混合調節弁は、制御タイミング毎に、その時点における予熱温水温度、低温水温度及び前記混合調節弁から送出されている温水の温度に基づいて、予熱温水に対する低温水の混合比率を算出すると共に、その時点における予熱温水温度、低温水温度及び目標温度に基づいて、予熱温水に対する低温水の目標混合比率を算出しながら、その目標混合比率になるように弁開度が制御されるようになっており、算出された目標混合比率が予め定められた最低混合比率を下回っている場合は、目標混合比率を最低混合比率に設定するようにしたことを特徴とする給湯システムを提供することにある。
【００１４】
以上のように、この給湯システムでは、給湯開始直後に、配管内に滞留していた固定温度を下回る予熱温水が混合調節弁に送出され始めると、その時点における予熱温水温度、低温水温度及び固定温度に基づいて、その時点における予熱温水に対する低温水の目標混合比率を算出するが、算出された目標混合比率が予め定められた最低混合比率を下回っている場合は、目標混合比率を最低混合比率に設定するようになっているので、低温水の供給圧と予熱温水の供給圧とが異なるために、混合調節弁の混合特性が、最大開度側において、弁開度の変化率に対する混合比率の変化率が小さく、しかも、最大開度まで開弁する前に最低混合比率を下回ってしまうような混合特性に変化したような場合や低温水の供給圧と予熱温水の供給圧とが同圧であってもそういった混合特性を示すような廉価な混合調節弁を使用した場合には、最大開度まで開弁することはなく、最低混合比率を下回る直前の開度までしか開弁しないので、その後に、固定温度以上の予熱温水が混合調節弁に送出されるようになった時点で混合調節弁が閉弁動作を行う際、目標混合比率まで短時間で閉弁することができる。従って、混合調節弁に送出される予熱温水の急激な温度上昇にもある程度追従することができ、給湯開始から給湯設定温度の温水を安定して出湯することが可能となる。
【００１５】
【発明の実施の形態】
以下、実施の形態について図面を参照して説明する。図１は、補助熱源として太陽熱を利用した給湯システム１の概略構成を示している。この給湯システム１は、同図に示すように、太陽熱利用温水器１０と給湯器２０とが接続されたものであり、太陽熱利用温水器１０によって生成された予熱温水が給湯器２０に送出されるようになっている。
【００１６】
前記太陽熱利用温水器１０は、ソーラー集熱器１１と密閉式の蓄熱槽１４とを備えており、蓄熱槽１４には、その下端部に低温水を供給するための給水管１５が接続されていると共に、上端部には貯留された予熱温水を給湯器２０に送出するための予熱温水供給管１６が接続されている。
【００１７】
前記ソーラー集熱器１１には、その入口側と出口側とを接続するソーラー配管１２によって熱媒体の循環経路が形成されており、このソーラー配管１２は、部分的に蓄熱槽１４内に導入された熱交換部１３を有している。従って、ソーラー集熱器１１によって加熱された熱媒体は、ソーラー配管１２を通って蓄熱槽１４内に導かれ、熱交換部１３で蓄熱槽１４内の水と熱交換を行うことで、蓄熱槽１４内に温水が生成されるようになっている。
【００１８】
前記給湯器２０は、給水管１７を介して供給される低温水と蓄熱槽１４から予熱温水供給管１６を介して供給される予熱温水とを必要に応じて混合する、ステッピングモータによって開閉駆動される一軸式の混合調節弁２１と、混合調節弁２１の出口側に接続された、混合調節弁２１から送出される温水を必要に応じて加熱する熱交換器２２を有するメイン流路２３と、熱交換器２２をバイパスするように、メイン流路２３に接続されたバイパス流路２４とを備えており、バイパス流路２４には、熱交換器２２から送出される高温の温水に、混合調節弁２１から送出される比較的低温の温水を適宜混合することによって給湯設定温度Ｔｅの温水を生成するためのバイパス弁２４ａが設置されている。
【００１９】
また、給水管１７及び混合調節弁２１の温水出口側に接続されたメイン流路２３には、混合調節弁２１をバイパスするバイパス管２５が接続されており、このバイパス管２５には、通電状態でバイパス管２５の流路を遮断するダイヤフラム方式の電磁弁２５ａが設置されている。
【００２０】
また、混合調節弁２１に接続された予熱温水供給管１６、混合調節弁２１に接続された給水管１７、メイン流路２３におけるバイパス管２５の接続部の上流側及び熱交換器２２とバイパス流路２４の下流側接続部との間には、蓄熱槽１４から送出される予熱温水の温度（以下、予熱温水温度という。）Ｔｐを検出するための予熱温水温度センサ２６、混合調節弁２１に送出される低温水の温度（以下、低温水温度という。）Ｔｗを検出するための低温水温度センサ２７、混合調節弁２１から送出される温水の温度（以下、混合温水温度という。）Ｔｍを検出するための混合温水温度センサ２８及び熱交換器２２の出口温水温度を、熱交換器２２自体の温度（以下、熱交換器温度という。）Ｔｃとして検出する熱交換器温度センサ２９がそれぞれ設置されている。
【００２１】
また、給湯器２０には、シリアルインターフェースを介して、操作リモコン３０のコントローラ３０ａとの間で通信可能なコントローラ２０ａが搭載されており、これらのコントローラ２０ａ、３０ａが相互に連携をとりながら、給湯器２０の運転動作を統括的に制御している。
【００２２】
前記コントローラ２０ａには、予熱温水温度センサ２６、低温水温度センサ２７、混合温水温度センサ２８及び熱交換器温度センサ２９からの温度検出信号が入力されると共に、操作リモコン３０によって設定された給湯設定温度Ｔｅや運転スイッチ信号等が操作リモコン３０のコントローラ３０ａから送信されるようになっており、これらの温度検出信号及び給湯設定温度Ｔｅ等に基づいて、コントローラ２０ａが混合調節弁２１、バイパス弁２４ａ及び熱交換器２２を加熱するバーナー（図示せず）を制御するようになっている。
【００２３】
蓄熱槽１４から送出される予熱温水の温度、即ち、予熱温水温度センサ２６によって検出された予熱温水温度Ｔｐが給湯設定温度Ｔｅ以上の場合は、給湯器２０のバーナーを燃焼させなくても、低温水を適宜混合することによって給湯設定温度Ｔｅの温水を出湯することができるので、混合調節弁２１から送出される温水の温度、即ち、混合温水温度センサ２８によって検出される混合温水温度Ｔｍが目標温度である給湯設定温度Ｔｅになるように、混合調節弁２１の開度を調整する目標温度制御を行うようになっている。
【００２４】
一方、予熱温水温度Ｔｐが給湯設定温度Ｔｅより低い場合は、給湯器２０のバーナーを燃焼させなければ、給湯設定温度Ｔｅの温水を出湯することができないので、給湯器２０のバーナーを燃焼させることによって、確実に給湯設定温度Ｔｅの温水を生成することができるように、目標温度である給湯設定温度Ｔｅ−１０℃（以下、固定温度Ｔｆという）の温水が熱交換器２２に送出されるように、混合調節弁２１の開度を調整して低温水を混合する目標温度制御を行うようになっている。
【００２５】
この場合、給湯器２０のバーナーは、熱交換器温度センサ２９によって検出される熱交換器温度Ｔｃが給湯設定温度Ｔｅ＋１２℃になるように、その燃焼制御を行うようになっており、バイパス弁２４ａは、熱交換器２２から送出される給湯設定温度Ｔｅ＋１２℃の温水と、バイパス流路２４を通って供給される固定温度Ｔｆの温水とを適宜混合することによって、給湯設定温度Ｔｅの温水を生成する出湯温度制御を行うようになっている。
【００２６】
前記混合調節弁２１は、開弁するに従って予熱温水に対する低温水の混合比率Ｐが小さくなり、閉弁するに従って予熱温水に対する低温水の混合比率Ｐが大きくなるようになっており、混合調節弁２１を駆動しているステッピングモータは、０ステップから１０５０ステップまで駆動することで、混合調節弁２１を全閉、全開させるようになっている。
【００２７】
この混合調節弁２１は、低温水の供給圧と予熱温水の供給圧とが略同圧である場合に、図２に実線で示すように、予熱温水に対する低温水の混合比率Ｐが混合調節弁２１を駆動するステッピングモータのステップ数、即ち、弁開度に対して略リニアに変化する混合特性を示すようになっており、この混合特性を示す状態において、混合比率Ｐが最低混合比率Ｐｍｉｎ（この場合、０．０３）を下回らないように、ステッピングモータの最大ステップ数（この場合、８００）、即ち、最大開度が設定されていると共に、混合比率Ｐが最大混合比率Ｐｍａｘ（この場合、１９）を上回らないように、ステッピングモータの最小ステップ数（この場合、０）、即ち、最小開度が設定されている。
【００２８】
混合調節弁２１が、上述した目標温度制御を行う場合は、制御タイミング（この場合、１００ｍｓ）毎に、その時点で検出された予熱温水温度Ｔｐ、低温水温度Ｔｗ及び混合温水温度Ｔｍから、数１に示す演算式に従って、その時点における、予熱温水に対する低温水の混合比率Ｐを算出すると共に、その時点で検出された予熱温水温度Ｔｐ、低温水温度Ｔｗ及び給湯設定温度Ｔｅや固定温度Ｔｆといった目標温度から、数２に示す演算式に従って、目標温度の温水を生成するために必要な予熱温水に対する低温水の目標混合比率Ｐｏを算出し、この目標混合比率Ｐｏになるように、混合調節弁２１の開度を調整することになるが、混合調節弁２１が、上述した最大開度まで開弁した時点で、そのときの予熱温水に対する低温水の混合比率Ｐが最低混合比率Ｐｍｉｎを下回っている場合は、その最低混合比率Ｐｍｉｎになるまで、混合調節弁２１を強制的に閉弁するようになっている。
【００２９】
【数１】

【００３０】
【数２】

【００３１】
以上のように、この給湯システム１では、混合調節弁２１が最大開度まで開弁した時点で、そのときの混合比率Ｐが最低混合比率Ｐｍｉｎを下回っている場合は、その最低混合比率Ｐｍｉｎになるまで、混合調節弁２１を強制的に閉弁するようになっているので、例えば、低温水の供給圧と予熱温水の供給圧とが異なるために、混合調節弁２１の混合特性が、図２に一点鎖線で示すように、最大開度側において、ステッピングモータのステップ数の変化率（弁開度の変化率）に対する混合比率Ｐの変化率が小さく、最大開度まで開弁する前に最低混合比率Ｐｍｉｎを下回ってしまうような混合特性に変化しており、しかも、蓄熱槽１４には固定温度Ｔｆ以上で給湯設定温度Ｔｅを下回る予熱温水が貯留されているが、予熱温水供給管１６に滞留している予熱温水が固定温度Ｔｆを下回る温度状態まで低下している場合において、給湯を開始すると、まず、予熱温水供給管１６内に滞留していた固定温度Ｔｆを下回る予熱温水が混合調節弁２１に送出され始めるので、混合調節弁２１が、固定温度Ｔｆの温水を生成しようとして、一旦最大開度まで開弁することになるが、最大開度まで開弁した時点における混合比率Ｐは最低混合比率Ｐｍｉｎを下回ることになるので、混合調節弁２１が最低混合比率Ｐｍｉｎになるまで即座に閉弁することになる。
【００３２】
その後に、蓄熱槽１４に貯留されていた固定温度Ｔｆ以上の予熱温水が混合調節弁２１に送出され始めると、混合調節弁２１が、固定温度Ｔｆの温水を生成しようとして、閉弁動作を開始することになるが、その時点では、混合調節弁２１が、最低混合比率Ｐｍｉｎの開度まで既に閉弁されているので、最大開度から目標混合比率まで閉弁させなければならない従来の給湯システムに比べて、混合調節弁２１を目標混合比率Ｐｏまで短時間で閉弁させることができる。
【００３３】
従って、この給湯システム１では、混合調節弁２１の混合特性が変化しているような場合であっても、予熱温水の急激な温度上昇に対して、混合調節弁２１の閉弁動作をある程度追従させることができ、給湯開始から給湯設定温度Ｔｅの温水を安定して出湯することが可能となる。
【００３４】
なお、上述した実施形態では、混合調節弁２１を一旦最大開度まで開弁させ、そのときの混合比率Ｐが最低混合比率Ｐｍｉｎを下回っている場合は、その最低混合比率Ｐｍｉｎになるまで、混合調節弁２１を強制的に閉弁させるようになっているが、これに限定されるものではなく、混合調節弁２１が目標温度制御を行っているときに算出された目標混合比率Ｐｏが最低混合比率Ｐｍｉｎを下回っているような場合は、目標混合比率Ｐｏを最低混合比率Ｐｍｉｎに設定したり、算出された目標混合比率Ｐｏが最低混合比率Ｐｍｉｎを下回っているような場合であっても、最低混合比率Ｐｍｉｎを下回る弁開度まで開弁しないように、混合調節弁２１の開弁動作を制限したりすることによって、混合調節弁２１の混合特性が変化したような場合には、混合調節弁２１を最大開度まで開弁させないようにすることも可能である。
【００３５】
また、上述した実施形態では、低温水の供給圧と予熱温水の供給圧とが略同圧である場合に、弁開度に対して混合比率が略リニアに変化する混合特性を示す混合調節弁を使用した給湯システムについて説明したが、これに限定されるものではなく、低温水の供給圧と予熱温水の供給圧とが同圧であっても、略リニアな混合特性を示さないような廉価な混合調節弁を使用した場合についても、本発明が有効であることはいうまでもない。
【００３６】
また、上述した実施形態では、混合調節弁２１が固定温度制御を行う場合の目標温度である固定温度Ｔｆを、給湯設定温度Ｔｅ−１０℃に設定しているが、これに限定されるものではなく、例えば、給湯設定温度Ｔｅが６０℃以上、６０℃未満３５℃以上、３５℃未満に場合分けし、６０℃以上の場合は４５℃、６０℃未満３５℃以上の場合は３０℃、３５℃未満の場合は２５℃といった具合に、給湯設定温度Ｔｅに応じて、固定温度Ｔｆを段階的に設定することも可能である。
【００３７】
また、上述した実施形態では、混合調節弁２１が組み込まれた給湯器２０を使用した給湯システムについて説明したが、これに限定されるものではなく、混合調節弁を有する給湯接続ユニットを介して、太陽熱利用温水器と通常の給湯器とを接続した給湯システムについても、本発明を適用することができることはいうまでもない。
【００３８】
また、上述した実施形態では、補助熱源が太陽熱である給湯システムについて説明したが、補助熱源はこういった太陽熱に限定されるものではなく、例えば、コージェネレーションシステムにおけるガスエンジンやガスタービンの排熱を補助熱源とした給湯システムのように、種々の補助熱源を使用した給湯システムについて、本発明を適用することができることはいうまでもなく、特に、低温水の供給圧と予熱温水の供給圧とが通常異なるような給湯システムの場合に、本発明が有効である。
【図面の簡単な説明】
【図１】この発明にかかる給湯システムの一実施形態を示す概略構成図である。
【図２】同上の給湯システムに使用されている給湯器に搭載された混合調節弁の混合特性を示す図である。
【符号の説明】
１　給湯システム
１０　太陽熱利用温水器
１４　蓄熱槽
１５、１７　給水管
１６　予熱温水供給管
２０　給湯器
２０ａ　コントローラ
２１　混合調節弁
２２　熱交換器
２３　メイン流路
２４　バイパス流路
２４ａ　バイパス弁
２５　バイパス管
２５ａ　電磁弁
２６　予熱温水温度センサ
２７　低温水温度センサ
２８　混合温水温度センサ
２９　熱交換器温度センサ
３０　操作リモコン
３０ａ　コントローラ[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a hot water supply system for supplying hot water using preheated hot water generated by an auxiliary heat source.
[0002]
[Prior art]
As a hot water supply system using an auxiliary heat source, for example, a solar water heater that includes a heat storage tank that stores preheated hot water generated using solar heat that is an auxiliary heat source, and a water heater that is a main heat source is combined. BACKGROUND ART Hot water supply systems are conventionally generally known.
[0003]
In such a hot water supply system, the heat storage tank of the solar water heater is connected to the water heater, and when hot water is supplied, the preheated hot water stored in the heat storage tank of the solar water heater is sent to the water heater. However, instead of sending the preheated hot water sent from the heat storage tank to the heat exchanger as it is, use low-temperature water (tap water at normal water temperature or water at a temperature lower than the preheated hot water) as necessary. A mixing control valve for mixing the preheated hot water and the low-temperature water sent from the heat storage tank at an arbitrary mixing ratio so that the mixed water can be sent to the heat exchanger in a mixed state is provided upstream of the heat exchanger. The built-in water heater may be used, and the mixing control valve is designed such that as the valve opens, the mixing ratio of low-temperature water to preheating hot water decreases, and as the valve closes, the mixing ratio of low-temperature water to preheating hot water increases. Has become
[0004]
In a hot water supply system using a water heater incorporating such a mixing control valve, when preheated hot water is stored in a heat storage tank at a temperature higher than a set hot water supply temperature set for the water heater, the mixing control valve is A burner that heats the heat exchanger by generating hot water at the hot water supply set temperature by appropriately mixing preheated hot water and low temperature water at or above the hot water supply set temperature sent from the heat storage tank, and sending this to the heat exchanger. The hot water at the set hot water supply temperature is discharged without burning the water. On the other hand, when the preheated hot water not lower than the hot water supply set temperature is not stored in the heat storage tank, the mixing control valve is predetermined by appropriately mixing the preheated hot water lower than the hot water supply set temperature sent from the heat storage tank with the low-temperature water. By sending the water to the heat exchanger in a state where the temperature has been lowered to the fixed temperature, and burning the burner to heat the heat exchanger, hot water is generated while generating hot water at the hot water supply set temperature.
[0005]
[Problems to be solved by the invention]
Incidentally, in such a hot water supply system, in order to ensure good controllability, when the supply pressure of the low-temperature water and the supply pressure of the preheating hot water are substantially the same, as shown by a solid line in FIG. A mixing control valve is used that exhibits a mixing characteristic in which the mixing ratio of low-temperature water to water varies substantially linearly with valve opening. In addition, in such a hot water supply system, the preheated hot water Since the mixing ratio at that time is calculated based on the temperature, the low-temperature water temperature, and the temperature of the hot water sent from the mixing control valve, even in a state where the mixing control valve is opened to the maximum opening, the state is maintained. The supply pressure of the low-temperature water and the pre-heated hot water so that a slight temperature difference occurs between the temperature of the pre-heated hot water and the temperature of the hot water sent from the mixing control valve. Supply pressure and Given the mixing properties when substantially a same pressure, a minimum mixing ratio is determined in advance at the time of maximum opening. Therefore, when the hot water supply system is used in a state where the supply pressure of the low-temperature water and the supply pressure of the preheating hot water are substantially the same, good controllability is ensured and the mixing control valve is moved to the maximum opening degree. Even when the valve is open, the mixing ratio at that time does not fall below the minimum mixing ratio.
[0006]
However, actually, the supply pressure of the low-temperature water and the supply pressure of the preheated hot water are not necessarily substantially the same. For example, when the supply pressure of the preheated hot water is higher than the supply pressure of the low-temperature water, one point is shown in FIG. As indicated by the dashed line, on the maximum opening side, the change ratio of the mixture ratio with respect to the change ratio of the valve opening is small, and the mixing characteristics are such that the mixture ratio falls below the minimum mixture ratio before opening the valve to the maximum opening. It may change, and in such a case, the following problem occurs.
[0007]
For example, in the heat storage tank, preheated hot water that is higher than the fixed temperature and lower than the set hot water supply temperature is stored, but the temperature of the preheated hot water staying in the pipe connecting the heat storage tank and the water heater becomes equal to or lower than the fixed temperature. When the hot water supply is started in a state where the temperature is lowered, the pre-heated hot water having a fixed temperature or less staying in the pipe at the beginning of the hot water supply is sent to the mixing control valve of the water heater, so that the mixing control valve has a fixed temperature. Although the valve is opened to the maximum opening to generate hot water, the preheated hot water below the fixed temperature that has accumulated in the piping has been sent out, and the preheated hot water that exceeds the fixed temperature stored in the heat storage tank has been sent out. Is being delivered, the mixing control valve begins to close in an attempt to produce a fixed temperature hot water by mixing the cold water.
[0008]
However, since the opening / closing drive speed of the mixing control valve by the motor is slow, as described above, the change rate of the mixing ratio with respect to the change rate of the valve opening is small on the maximum opening side, and the valve is opened to the maximum opening degree. If the mixing characteristics change below the minimum mixing ratio before the mixing, the valve closing operation of the mixing control valve cannot follow the rapid temperature change of the hot water sent to the mixing control valve, and the target mixing It takes some time to reach the ratio, during which time hot water exceeding the fixed temperature will be sent to the heat exchanger, so the burner burns and sends hot water at the set hot water supply temperature. There is a problem that the hot water supply device cannot reliably perform the hot water temperature control, and the hot water temperature temporarily rises.
[0009]
Therefore, an object of the present invention is to provide a hot water supply system capable of stably supplying hot water at a set hot water supply temperature even when a mixing control valve does not have a substantially linear mixing characteristic. .
[0010]
Means for Solving the Problems and Their Effects
In order to solve the above problem, the invention according to claim 1 sends hot water at a target temperature to a heat exchanger of a water heater while mixing low-temperature water as necessary with preheated hot water generated by an auxiliary heat source. In the hot water supply system provided with the mixing control valve, the mixing control valve is configured such that the mixing ratio of the low-temperature water to the preheating hot water decreases as the valve opens, and the mixing ratio of the low-temperature water to the preheating hot water increases as the valve closes. The mixing control valve is configured such that, at each control timing, the mixing ratio of low-temperature water to preheating hot water is determined based on the preheated hot water temperature, the low-temperature water temperature, and the temperature of the hot water sent from the mixing control valve at that time. While calculating the target mixing ratio of low-temperature water to pre-heated hot water based on the preheated hot water temperature, low-temperature water temperature, and target temperature at that time. The valve opening is controlled so as to reach the target mixing ratio, and when the mixing control valve opens to the maximum opening, the mixing ratio of low-temperature water to preheated hot water at that time is predetermined. If the mixing ratio is below the minimum mixing ratio, the hot water supply system is characterized in that the mixing control valve is forcibly closed until the minimum mixing ratio is reached.
[0011]
As described above, in this hot water supply system, immediately after the start of hot water supply, when the preheated hot water having a temperature lower than the fixed temperature remaining in the pipe starts to be sent to the mixing control valve, the mixing control valve is once opened to the maximum opening. That is, at the time when the valve is opened to the maximum opening, if the mixing ratio of the low-temperature water to the preheated hot water at that time is lower than a predetermined minimum mixing ratio, the mixing control valve becomes the minimum mixing ratio. After that, when the mixing control valve performs the valve closing operation when the preheated hot water at a fixed temperature or more starts to be sent to the mixing control valve, the target mixing ratio is shortened. The valve can be closed in time.
[0012]
Therefore, since the supply pressure of the low-temperature water and the supply pressure of the preheated hot water are different, the mixing characteristic of the mixing control valve has a small change rate of the mixing ratio with respect to the change rate of the valve opening on the maximum opening side, and If the mixing characteristics change below the minimum mixing ratio before opening the valve to the maximum opening, or if the supply pressure of the low-temperature water and the supply pressure of the pre-heated hot water are the same, such mixing characteristics Even when an inexpensive mixing control valve as shown in the figure is used, it can follow the rapid rise in the temperature of the preheated hot water sent to the mixing control valve to some extent, and stabilizes hot water at the set hot water supply temperature from the start of hot water supply. It is possible to take a bath.
[0013]
Further, in order to solve the above-mentioned problem, the invention according to claim 2 provides a heat exchanger for a water heater by mixing hot water at a target temperature with preheated hot water generated by an auxiliary heat source while mixing low-temperature water as necessary. In the hot water supply system provided with the mixing control valve that sends out the water to the mixing control valve, the mixing ratio of the low-temperature water to the preheating hot water decreases as the valve opens, and the mixing ratio of the low-temperature water to the preheating hot water increases as the valve closes. The mixing control valve is configured such that, at each control timing, the preheating hot water temperature, the low temperature water temperature at that time, and the temperature of the hot water sent from the mixing control valve, While calculating the mixing ratio, the target mixing ratio of the low-temperature water to the preheating hot water is calculated based on the preheating hot water temperature, the low-temperature water temperature, and the target temperature at that time. The valve opening is controlled so as to reach the target mixture ratio, and if the calculated target mixture ratio is lower than the predetermined minimum mixture ratio, the target mixture ratio is set to the minimum mixture ratio. The present invention is to provide a hot water supply system characterized by being set to.
[0014]
As described above, in this hot water supply system, immediately after the start of hot water supply, when preheated hot water having a temperature lower than the fixed temperature remaining in the pipes starts to be sent to the mixing control valve, the preheated hot water temperature, the low-temperature water temperature and the fixed Based on the temperature, the target mixing ratio of the low-temperature water to the preheated hot water at that time is calculated, but if the calculated target mixing ratio is lower than the predetermined minimum mixing ratio, the target mixing ratio is set to the minimum mixing ratio. Since the supply pressure of the low-temperature water and the supply pressure of the preheated hot water are different, the mixing characteristics of the mixing control valve are changed at the maximum opening side to the mixing ratio with respect to the rate of change of the valve opening degree. Is small, and the mixing characteristics change below the minimum mixing ratio before opening the valve to the maximum opening, or when the supply pressure of low-temperature water and the supply pressure of preheated hot water are the same. If an inexpensive mixing control valve that exhibits such mixing characteristics is used, the valve will not open to the maximum opening, but only to the opening immediately before the minimum mixing ratio falls. Further, when the mixing control valve performs the valve closing operation when the preheated hot water having a temperature equal to or higher than the fixed temperature is sent to the mixing control valve, the valve can be closed to the target mixing ratio in a short time. Therefore, it is possible to follow a rapid rise in the temperature of the preheated hot water sent to the mixing control valve to some extent, and it is possible to stably discharge hot water at the set hot water supply temperature from the start of hot water supply.
[0015]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, embodiments will be described with reference to the drawings. FIG. 1 shows a schematic configuration of a hot water supply system 1 using solar heat as an auxiliary heat source. In this hot water supply system 1, as shown in the figure, a solar water heater 10 and a water heater 20 are connected, and preheated hot water generated by the solar water heater 10 is sent to the water heater 20. It has become.
[0016]
The solar water heater 10 includes a solar heat collector 11 and a closed heat storage tank 14. The lower end of the heat storage tank 14 is connected to a water supply pipe 15 for supplying low-temperature water. A preheated hot water supply pipe 16 for sending stored preheated hot water to the water heater 20 is connected to the upper end.
[0017]
In the solar collector 11, a circulation path of the heat medium is formed by a solar pipe 12 connecting the inlet side and the outlet side, and the solar pipe 12 is partially introduced into the heat storage tank 14. Heat exchange part 13. Therefore, the heat medium heated by the solar heat collector 11 is guided into the heat storage tank 14 through the solar pipe 12, and the heat exchange unit 13 performs heat exchange with water in the heat storage tank 14. Hot water is generated in the inside of the fuel cell 14.
[0018]
The water heater 20 is opened and closed by a stepping motor that mixes low-temperature water supplied via a water supply pipe 17 and preheated hot water supplied from a heat storage tank 14 via a preheated hot water supply pipe 16 as necessary. A single-shaft type mixing control valve 21, a main flow path 23 having a heat exchanger 22 connected to the outlet side of the mixing control valve 21 and heating the hot water delivered from the mixing control valve 21 as necessary. A bypass flow path 24 connected to the main flow path 23 is provided so as to bypass the heat exchanger 22. The bypass flow path 24 is provided for mixing and adjusting hot water discharged from the heat exchanger 22 with hot water. A bypass valve 24a for generating hot water at the hot water supply set temperature Te by appropriately mixing relatively low-temperature hot water sent from the valve 21 is provided.
[0019]
A bypass pipe 25 that bypasses the mixing control valve 21 is connected to the main flow path 23 connected to the water supply pipe 17 and the hot water outlet side of the mixing control valve 21. A solenoid valve 25a of a diaphragm type for shutting off the flow path of the bypass pipe 25 is provided.
[0020]
The preheating hot water supply pipe 16 connected to the mixing control valve 21, the water supply pipe 17 connected to the mixing control valve 21, the upstream side of the connection of the bypass pipe 25 in the main flow path 23, and the heat exchanger 22 and the bypass flow A preheated hot water temperature sensor 26 for detecting the temperature (hereinafter, referred to as preheated hot water temperature) Tp of the preheated hot water sent from the heat storage tank 14 and a mixing control valve 21 are provided between the downstream side connection portion of the passage 24 and the heat storage tank 14. A low-temperature water temperature sensor 27 for detecting the temperature of the low-temperature water sent out (hereinafter, referred to as low-temperature water temperature) Tw, and the temperature Tm of hot water sent out from the mixing control valve 21 (hereinafter, referred to as mixed hot-water temperature) Tm. The mixed hot water temperature sensor 28 for detecting the temperature of the hot water at the outlet of the heat exchanger 22 and the heat exchanger temperature sensor 29 for detecting the temperature of the hot water at the outlet of the heat exchanger 22 itself (hereinafter, referred to as the heat exchanger temperature) Tc. It is installed.
[0021]
The water heater 20 is equipped with a controller 20a capable of communicating with the controller 30a of the operation remote controller 30 via a serial interface. The

controllers

20a and 30a cooperate with each other to supply hot water. The operation of the heater 20 is controlled in an integrated manner.
[0022]
The controller 20a receives temperature detection signals from the preheated hot water temperature sensor 26, the low-temperature water temperature sensor 27, the mixed hot water temperature sensor 28, and the heat exchanger temperature sensor 29, and sets hot water supply set by the operation remote controller 30. The temperature Te, the operation switch signal, and the like are transmitted from the controller 30a of the operation remote controller 30. Based on the temperature detection signal and the hot water supply set temperature Te, the controller 20a sets the mixing control valve 21, the bypass valve 24a, and the like. Further, a burner (not shown) for heating the heat exchanger 22 is controlled.
[0023]
If the temperature of the preheated hot water sent from the heat storage tank 14, that is, the preheated hot water temperature Tp detected by the preheated hot water temperature sensor 26 is equal to or higher than the hot water set temperature Te, the low temperature can be maintained without burning the burner of the water heater 20. Hot water at the set hot water supply temperature Te can be discharged by appropriately mixing the water. Therefore, the temperature of the hot water sent from the mixing control valve 21, that is, the mixed hot water temperature Tm detected by the mixed hot water temperature sensor 28 is set as the target. Target temperature control for adjusting the opening of the mixing control valve 21 so as to reach the hot water supply set temperature Te, which is the temperature, is performed.
[0024]
On the other hand, when the preheating hot water temperature Tp is lower than the hot water supply set temperature Te, the hot water at the hot water supply set temperature Te cannot be discharged unless the burner of the hot water supply 20 is burned. As a result, the hot water at the hot water supply set temperature Te−10 ° C. (hereinafter, referred to as a fixed temperature Tf), which is the target temperature, is sent to the heat exchanger 22 so that the hot water at the hot water supply set temperature Te can be reliably generated. In addition, target temperature control for mixing low-temperature water by adjusting the opening of the mixing control valve 21 is performed.
[0025]
In this case, the burner of the water heater 20 controls the combustion so that the heat exchanger temperature Tc detected by the heat exchanger temperature sensor 29 becomes the hot water supply set temperature Te + 12 ° C., and the bypass valve 24a Generates hot water at the set hot water supply temperature Te by appropriately mixing hot water at the set hot water supply temperature Te + 12 ° C. sent from the heat exchanger 22 and hot water at the fixed temperature Tf supplied through the bypass passage 24. Hot water temperature control is performed.
[0026]
The mixing control valve 21 is configured such that the mixing ratio P of the low-temperature water with respect to the preheated hot water decreases as the valve opens, and the mixing ratio P of the low-temperature water with respect to the preheating hot water increases as the valve closes. Is driven from step 0 to step 1050 to fully close and fully open the mixing control valve 21.
[0027]
When the supply pressure of the low-temperature water and the supply pressure of the preheating hot water are substantially the same, the mixing control valve 21 changes the mixing ratio P of the low-temperature water to the preheating hot water as shown by a solid line in FIG. 21 shows a mixing characteristic that changes substantially linearly with the number of steps of the stepping motor that drives the motor 21, that is, the valve opening degree. In this case, the maximum number of steps of the stepping motor (800 in this case), that is, the maximum opening is set so that the value does not fall below 0.03), and the mixing ratio P becomes the maximum mixing ratio Pmax (in this case, 19), the minimum step number (0 in this case) of the stepping motor, that is, the minimum opening degree is set.
[0028]
In the case where the mixing control valve 21 performs the above-described target temperature control, at every control timing (in this case, 100 ms), the temperature of the preheated hot water temperature Tp, the low-temperature water temperature Tw, and the mixed hot water temperature Tm detected at that time is calculated by several times. According to the arithmetic expression shown in FIG. 1, the mixing ratio P of the low-temperature water to the pre-heating hot water at that time is calculated, and the pre-heating hot water temperature Tp, the low-temperature water temperature Tw, the hot water supply set temperature Te, and the fixed temperature Tf detected at that time are calculated. From the target temperature, a target mixing ratio Po of low-temperature water to preheated hot water required to generate hot water of the target temperature is calculated according to an arithmetic expression shown in Equation 2, and the mixing control valve is adjusted so that the target mixing ratio Po is obtained. When the mixing control valve 21 is opened to the above-described maximum opening, the mixing ratio P of the low-temperature water to the preheated hot water at that time is adjusted. If you are below the minimum mixing ratio Pmin, until that minimum mixing ratio Pmin, is adapted to forcibly closes the mixing control valve 21.
[0029]
(Equation 1)

[0030]
(Equation 2)

[0031]
As described above, in the hot water supply system 1, when the mixing ratio P at that time is lower than the minimum mixing ratio Pmin when the mixing control valve 21 is opened to the maximum opening, the minimum mixing ratio Pmin is set to the minimum mixing ratio Pmin. Until the mixing control valve 21 is forcibly closed, for example, since the supply pressure of the low-temperature water and the supply pressure of the preheating hot water are different, the mixing characteristics of the mixing control valve 21 are As shown by the dashed line in FIG. 2, the change rate of the mixing ratio P with respect to the change rate of the step number of the stepping motor (change rate of the valve opening) is small on the maximum opening side, and before the valve is opened to the maximum opening. Although the mixing characteristics have changed to be lower than the minimum mixing ratio Pmin, the preheated hot water having a temperature equal to or higher than the fixed temperature Tf and lower than the set hot water supply temperature Te is stored in the heat storage tank 14. Delay When hot water supply is started in a case where the preheated hot water that has been cooled to a temperature lower than the fixed temperature Tf, first, the preheated hot water lower than the fixed temperature Tf that has stayed in the preheated hot water supply pipe 16 is mixed with the mixing control valve. 21, the mixing control valve 21 once opens the valve to the maximum opening in an attempt to generate hot water of the fixed temperature Tf, but the mixing ratio P at the time of opening the valve to the maximum opening is the lowest. Since the mixing ratio is lower than Pmin, the mixing control valve 21 is immediately closed until the mixing ratio Pmin reaches the minimum mixing ratio Pmin.
[0032]
Thereafter, when preheated hot water having a temperature equal to or higher than the fixed temperature Tf stored in the heat storage tank 14 starts to be sent to the mixing control valve 21, the mixing control valve 21 starts the valve closing operation in an attempt to generate hot water having the fixed temperature Tf. However, at that time, since the mixing control valve 21 is already closed to the opening of the minimum mixing ratio Pmin, the conventional hot water supply system which must be closed from the maximum opening to the target mixing ratio is required. , The mixing control valve 21 can be closed to the target mixing ratio Po in a short time.
[0033]
Therefore, in this hot water supply system 1, even when the mixing characteristics of the mixing control valve 21 are changing, the valve closing operation of the mixing control valve 21 follows the rapid temperature rise of the preheating hot water to some extent. It is possible to stably supply hot water at the hot water supply set temperature Te from the start of hot water supply.
[0034]
In the above-described embodiment, the mixing control valve 21 is once opened to the maximum opening, and when the mixing ratio P at that time is lower than the minimum mixing ratio Pmin, the mixing is continued until the mixing ratio Pmin becomes the minimum mixing ratio Pmin. Although the control valve 21 is forcibly closed, the present invention is not limited to this. The target mixing ratio Po calculated when the mixing control valve 21 is performing the target temperature control is the minimum mixing ratio. When the target mixture ratio Po is lower than the minimum mixture ratio Pmin, the target mixture ratio Po is set to the minimum mixture ratio Pmin, or when the calculated target mixture ratio Po is lower than the minimum mixture ratio Pmin. When the mixing characteristic of the mixing control valve 21 changes, for example, by restricting the opening operation of the mixing control valve 21 so as not to open the valve below the mixing ratio Pmin. , It is also possible to mixing control valve 21 so as not to open to the maximum degree.
[0035]
Further, in the above-described embodiment, when the supply pressure of the low-temperature water and the supply pressure of the preheated hot water are substantially the same, the mixing control valve having the mixing characteristic in which the mixing ratio changes substantially linearly with the valve opening degree. However, the present invention is not limited to this, and even if the supply pressure of the low-temperature water and the supply pressure of the preheating hot water are the same, an inexpensive price that does not show a substantially linear mixing characteristic. It is needless to say that the present invention is also effective when a suitable mixing control valve is used.
[0036]
In the above-described embodiment, the fixed temperature Tf, which is the target temperature when the mixing control valve 21 performs the fixed temperature control, is set to the hot water supply set temperature Te-10 ° C., but is not limited to this. For example, for example, the hot water supply set temperature Te is divided into 60 ° C. or more, less than 60 ° C. and 35 ° C. or more, and less than 35 ° C .; When the temperature is lower than 0 ° C., the fixed temperature Tf can be set stepwise according to the hot water supply set temperature Te, such as 25 ° C.
[0037]
Further, in the above-described embodiment, the hot water supply system using the water heater 20 in which the mixing control valve 21 is incorporated has been described. However, the present invention is not limited to this. It goes without saying that the present invention can be applied to a hot water supply system in which a solar water heater and a normal water heater are connected.
[0038]
Further, in the above-described embodiment, the hot water supply system in which the auxiliary heat source is solar heat has been described. However, the auxiliary heat source is not limited to such solar heat, and for example, exhaust heat of a gas engine or a gas turbine in a cogeneration system. Needless to say, the present invention can be applied to a hot water supply system using various auxiliary heat sources, such as a hot water supply system using an auxiliary heat source, particularly, a supply pressure of low-temperature water and a supply pressure of preheated hot water. The present invention is effective in the case of a hot water supply system in which the water supply system is usually different.
[Brief description of the drawings]
FIG. 1 is a schematic configuration diagram showing one embodiment of a hot water supply system according to the present invention.
FIG. 2 is a diagram showing mixing characteristics of a mixing control valve mounted on a water heater used in the same hot water supply system.
[Explanation of symbols]
REFERENCE SIGNS LIST 1 hot water supply system 10 solar water heater 14

heat storage tanks

15, 17 water supply pipe 16 preheated hot water supply pipe 20 water heater 20 a controller 21 mixing control valve 22 heat exchanger 23 main flow path 24 bypass flow path 24 a bypass valve 25 bypass pipe 25 a electromagnetic Valve 26 Preheated hot water temperature sensor 27 Low temperature water temperature sensor 28 Mixed hot water temperature sensor 29 Heat exchanger temperature sensor 30 Operation remote controller 30a Controller

Claims

In a hot water supply system including a mixing control valve that sends out hot water of a target temperature to a heat exchanger of a water heater while mixing low-temperature water as necessary with preheated hot water generated by the auxiliary heat source,
The mixing control valve, as the valve is opened, the mixing ratio of the low-temperature water to the preheated hot water decreases, and as the valve closes, the mixing ratio of the low-temperature water to the preheating hot water increases.
The mixing control valve, for each control timing, based on the preheating hot water temperature at that time, the low temperature water temperature and the temperature of the hot water sent from the mixing control valve, the mixing ratio of low temperature water to preheating hot water at that time. While calculating, based on the preheated hot water temperature, the low-temperature water temperature, and the target temperature at that time, while calculating the target mixing ratio of the low-temperature water to the preheated hot water at that time, the valve opening degree is adjusted to the target mixing ratio. Is controlled,
At the time when the mixing control valve is opened to the maximum opening, if the mixing ratio of the low-temperature water to the preheated hot water at that time is lower than a predetermined minimum mixing ratio, the above-mentioned mixing ratio becomes the minimum mixing ratio. A hot water supply system wherein the mixing control valve is forcibly closed.

In a hot water supply system including a mixing control valve that sends out hot water of a target temperature to a heat exchanger of a water heater while mixing low-temperature water as necessary with preheated hot water generated by the auxiliary heat source,
The mixing control valve, as the valve is opened, the mixing ratio of the low-temperature water to the preheated hot water decreases, and as the valve closes, the mixing ratio of the low-temperature water to the preheating hot water increases.
The mixing control valve, for each control timing, based on the preheating hot water temperature at that time, the low temperature water temperature and the temperature of the hot water sent from the mixing control valve, the mixing ratio of low temperature water to preheating hot water at that time. While calculating, based on the preheated hot water temperature, the low-temperature water temperature, and the target temperature at that time, while calculating the target mixing ratio of the low-temperature water to the preheated hot water at that time, the valve opening degree is adjusted to the target mixing ratio. Is controlled,
When the calculated target mixture ratio is lower than a predetermined minimum mixture ratio, the target mixture ratio is set to the minimum mixture ratio.