JP2008116148A - Water heater - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To efficiently recover heat of combustion emission gas generated by a gas burner 12 by means of a circulation heat exchanger 13 for improving heat efficiency of a water heater having: a circulation heating circuit which has the circulation heat exchanger heated by the gas burner 12 and a circulation pump 15; a liquid-liquid heat exchanger performing heat exchange between water flowing through a hot water supply circuit to be heated and circulation hot water flowing through the circulation heating circuit; a supply water temperature sensor detecting an entering water temperature Tin of the water to be heated flowing into the liquid-liquid heat exchanger in the hot water supply circuit; a hot water supply temperature setting apparatus for setting a hot water supply set temperature Tset of supplied hot water taken out from the hot water supply circuit; and a flow rate sensor determining a flow rate Q1 of the supplied hot water. <P>SOLUTION: The number of revolutions of the circulation pump 15 is lowered within the limit to maintain a temperature of the supplied hot water at the hot water supply set temperature Tset. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a water heater in which hot water at a hot water supply set temperature can be taken out from the hot water supply circuit by exchanging heat between the circulating hot water in the circulation heating circuit and the heated water in the hot water supply circuit using a liquid heat exchanger. .

FIG. 11 is a schematic configuration diagram of a composite water heater having a hot water supply function, a heating function, a bath retreat function, and the like (Patent Document 1).
This device was equipped with a hot water supply circuit (3) for supplying hot water to a hot water tap (not shown) arranged in a kitchen or a washroom, etc., and a recuperation heat exchanger (41) for retreating the bathtub (40). It is equipped with a heating circuit (5) to which a bath circuit (4) and a floor heating mat (110) etc. are connected. These circuits (3), (4) and (5) are connected to the circulation heating circuit (2). It is designed to be heated with warm water.

The circulation heating circuit (2) consists of a circulation heat exchanger (13) heated by a gas burner (12) → a hot water supply heating valve (16) → a primary side of a liquid-liquid heat exchanger (10) → a tank (14) → circulation It is a circuit that circulates with the pump (15) → the heat exchanger for circulation (13). Note that the liquid-liquid heat exchanger (10) means a circuit in which the primary side that is the circulation circuit (2) and the secondary side that is the hot-water supply circuit (3) are both liquid circuits.
The hot water supply circuit (3) is a circuit connected in the order of the water supply inlet (37) → the secondary side of the liquid-liquid heat exchanger (10) → the hot water outlet (38) → the hot water tap (not shown).

The heating circuit (5) is a circuit connected from the heat exchanger for circulation (13) to the circulation pump (15) via the heating terminal (11), and the high-temperature heating circuit (52) provided with the fan convector (111). And a low-temperature heating circuit (53) provided with a floor heating mat (110).
The high temperature heating circuit (52) branches from the outlet side of the circulation heat exchanger (13) to the high temperature heating valve (50) and is connected to the tank (14) via the fan convector (111). The low-temperature heating circuit (53) branches from the circuit connected to the high-temperature heating valve (50) from the circulation heat exchanger (13), and is connected to the low-temperature heating valve (51) → floor heating mat (110) → tank (14). ing.

Next, the hot water supply operation by the composite water heater will be described.
When a hot water tap (not shown) disposed on the downstream side of the hot water outlet (38) is opened, heated water that has flowed from the water supply inlet (37) begins to flow through the hot water supply circuit (3). On the other hand, when a flow rate sensor (not shown) in the hot water supply circuit (3) detects a water flow, the hot water heating valve (16) of the circulation heating circuit (2) is opened and the circulation pump (15) is operated to operate the gas burner. (12) is combusted, and the circulating hot water heated by the circulation heat exchanger (13) is heated to the circulation heat exchanger (13) → the hot water supply heating valve (16) → the liquid-liquid heat exchanger. (10) Primary side-> Tank (14)-> Circulation pump (15)-> Circulate through a path connected to the circulation heat exchanger (13). Then, the circulating hot water in the circulating heating circuit (2) and the heated water in the hot water supply circuit (3) are heat-exchanged in the liquid-liquid heat exchanger (10), whereby the heated water is heated to the hot water supply set temperature, Hot water is supplied to a tap tap connected to the downstream side of the circuit (3).
In this case, from the hot water supply flow rate Q1 in the hot water supply circuit (3), the incoming water temperature Tin of the heated water flowing into the hot water supply circuit (3), and the hot water supply set temperature Tset set in the remote controller (not shown), The amount of heat required for hot water supply is calculated, the gas burner (12) is combusted according to the required amount of heat, and the pump rotational speed of the circulation pump (15) is set.
JP 2003-130448 A

  However, in the above conventional one, the heat of the combustion exhaust generated by the gas burner (12) may not be sufficiently recovered by the circulation heat exchanger (13), and the thermal efficiency of the entire instrument may not be sufficiently high. There was a problem.

  That is, when the combustion amount of the gas burner (12) is the same, the temperature of the circulating hot water returning to the circulation heat exchanger (13) from the liquid-liquid heat exchanger (10) in the circulation heating circuit (2) (hereinafter, If the "return temperature") can be lowered, the temperature of the circulating hot water flowing into the circulation heat exchanger (13) is lowered, and the circulation heat exchanger (13) itself is also lowered. In such a case, since the temperature difference between the combustion exhaust from the circulation heat exchanger (13) and the gas burner (12) increases, the amount of heat that can be recovered from the combustion exhaust from the gas burner (12) by the circulation heat exchanger (13). Will increase. Therefore, in order to recover a large amount of heat from the combustion exhaust generated by the gas burner (12) by the circulation heat exchanger (13), it is desirable to lower the return temperature. However, in the above-mentioned conventional one, since the rotational speed of the circulation pump (15) is determined only from the necessary amount of heat, the circulating hot water returning from the liquid-liquid heat exchanger (10) to the circulation heat exchanger (13) is determined. The return temperature is not actively controlled. Accordingly, the return temperature to the circulation heat exchanger (13) is in a state of success, the circulation heat exchanger (13) cannot efficiently recover the heat of the combustion exhaust, and sufficient thermal efficiency cannot be ensured. There is.

The present invention has been made in view of such points.
`` A circulation heating circuit (2) having a circulation heat exchanger (13) heated by a gas burner (12) and a circulation pump (15);
A liquid-liquid heat exchanger (10) for performing heat exchange between heated water flowing through the hot water supply circuit (3) and circulating hot water flowing through the circulation heating circuit (2);
A water supply temperature sensor (32) for detecting an incoming temperature Tin of heated water flowing into the liquid-liquid heat exchanger (10) in the hot water supply circuit (3);
A hot water supply temperature setting section (65) for setting a hot water supply set temperature Tset of hot water and hot water to be taken out from the hot water supply circuit (3);
A flow rate sensor (33) for determining a flow rate Q1 of the hot water supply hot water;
By exchanging heat between the circulating hot water in the circulation heating circuit (2) circulated by the circulation pump (15) and the heated water in the hot water supply circuit (3) in the liquid-liquid heat exchanger (10), In the “water heater for raising the temperature of the heated water to the hot water supply set temperature Tset”, the heat of the combustion exhaust generated by the gas burner (12) is efficiently recovered by the circulation heat exchanger (13). Thus, an object is to improve the thermal efficiency of the water heater.

[Invention of Claim 1]
The solution means of the invention according to claim 1 for solving the above-mentioned problem is as follows:
“To reduce the rotational speed of the circulation pump (15) as long as the temperature of the hot water supply hot water can be maintained at the hot water supply set temperature Tset”.
The above solution works as follows.
When the pump rotational speed of the circulation pump (15) is reduced, the time for the circulating hot water in the circulating heating circuit (2) to pass through the liquid-liquid heat exchanger (10) becomes longer, so that the circulating hot water is supplied to the hot water supply circuit (3). The time for cooling with water to be heated becomes longer. As a result, the return temperature of the circulating hot water returning to the circulating heat exchanger (13) is lowered, so that the circulating heat exchanger (13) is easily cooled by the returning circulating hot water. The exchanger (13) can recover a lot of heat from the combustion exhaust.

[Invention of Claim 2]
In the invention according to claim 1,
“The pump speed decreases as the incoming water temperature Tin decreases”.
When other hot water supply conditions such as the hot water supply set temperature are constant, if the incoming temperature Tin of the heated water flowing into the primary side of the liquid-liquid heat exchanger (10) in the hot-water supply circuit (3) becomes high, the liquid-liquid heat Since the temperature difference between the circulating heating circuit (2), which is the primary side of the exchanger (10), and the hot water supply circuit (3), which is the secondary side, becomes small, heat is transferred from the circulating heating circuit (2) to the hot water supply circuit (3). It becomes difficult to flow and heat exchange is difficult. Therefore, by increasing the flow rate Q2 of the circulating hot water flowing through the circulating heating circuit (2) (increasing the pump rotation speed of the circulating pump (15)), the hot circulating hot water from the circulating heat exchanger (13) is removed. If the liquid-liquid heat exchanger (10) is not actively supplied, hot water at the hot water supply set temperature Tset cannot be taken out from the hot water supply circuit (3). Conversely, when the incoming water temperature Tin decreases, the temperature difference between the circulating heating circuit (2) which is the primary side of the liquid-liquid heat exchanger (10) and the hot water supply circuit (3) which is the secondary side increases. In addition, heat easily flows from the circulating heating circuit (2) side to the hot water supply circuit (3), and heat exchange is easy. From this, when extracting hot-water hot water having the same temperature, the flow rate Q2 of the circulating hot water can be made smaller when the incoming water temperature Tin is lower than when it is high. Therefore, when the incoming water temperature Tin is low, the hot water supply hot water at the hot water supply set temperature Tset can be taken out from the hot water supply circuit (3) even if the flow rate Q2 of the circulating hot water is reduced by reducing the pump rotation speed of the circulation pump (15). Therefore, in the invention according to claim 2, the pump rotational speed is decreased as the incoming water temperature Tin decreases.

[Invention of Claim 3]
In the invention according to claim 1 or claim 2,
“The pump rotation speed decreases as the hot water supply set temperature Tset decreases”.
In this case, if the incoming water temperature Tin of the hot water supply circuit (3) is constant, if the hot water supply set temperature Tset is lowered, the heat demand on the hot water supply circuit (3) side is reduced. The amount of heat to be reduced also decreases. Therefore, the hot water at the hot water supply set temperature Tset can be taken out from the hot water supply circuit (3) without increasing the amount of heat exchanged by increasing the circulation flow rate Q2. Therefore, in the invention according to claim 3, the pump rotational speed is decreased as the hot water supply set temperature Tset decreases.

[Invention of Claim 4]
In the invention according to claims 1 to 3,
“The inlet temperature on the circulating heating circuit (2) side of the liquid-liquid heat exchanger (10) is set to 70 ° C. or higher and 85 ° C. or lower”.
In this case, the inlet temperature on the circulating heating circuit (2) side of the liquid-liquid heat exchanger (10) is set to a high temperature of 70 ° C. or higher and 85 ° C. or lower. Compared to the case of a low temperature of less than ℃, the return temperature from the outlet on the circulation heating circuit (2) side of the liquid-liquid heat exchanger (10) to the circulation heat exchanger (13) can be further lowered, The thermal efficiency of the heat exchanger (13) can be further improved.
In addition, since the inlet temperature on the circulating heating circuit (2) side of the liquid-liquid heat exchanger (10) is set to 85 ° C. or lower, there is a problem that the circulating hot water is heated until it boils in the circulating heat exchanger (13). It can be surely prevented.

[Invention of Claim 5]
In the invention according to claims 1 to 4,
`` A bypass circuit (36) for bypassing the liquid-liquid heat exchanger (10) in the hot water supply circuit (3) is provided,
Hot water mixing means for mixing hot water through the liquid-liquid heat exchanger (10) in the hot water supply circuit (3) and cold water through the bypass circuit (36) to make the hot water at the hot water supply set temperature Tset. In the case of “provided”, the flow rate Q1 of the water to be heated distributed to the liquid-liquid heat exchanger (10) side in the hot water supply circuit (3) can be adjusted by the hot water mixing means. Therefore, even if the temperature of hot water supplied to the faucet or the like seems to fluctuate, it can be stabilized by adjusting the ratio of the flow rate Q1 on the liquid-liquid heat exchanger (10) side and the flow rate on the bypass circuit (36) side. Hot water temperature control.

The present invention has the following specific effects.
In the invention according to the first aspect, as described above, since a large amount of heat can be recovered from the combustion exhaust gas by the circulation heat exchanger (13), the thermal efficiency of the water heater is improved.
In the invention which concerns on Claim 2, the return temperature to the heat exchanger (13) for circulation can be reduced and thermal efficiency can be improved by reducing pump rotation speed with the fall of incoming water temperature Tin. Therefore, it is possible to provide a water heater with high thermal efficiency even with respect to changes in the incoming water temperature Tin.

  In the invention which concerns on Claim 3, the return temperature to the heat exchanger (13) for circulation can be reduced and thermal efficiency can be improved by reducing pump rotation speed with the fall of hot water supply preset temperature Tset. Therefore, it is possible to provide a hot water heater with high thermal efficiency even with respect to changes in the hot water supply set temperature Tset.

The invention according to claim 4 can provide a water heater with higher thermal efficiency, as will be described in an embodiment described later.
In the invention according to claim 5, as described above, the flow rate Q1 and the bypass circuit (36) on the liquid-liquid heat exchanger (10) side even when the temperature of hot water supplied to the faucet or the like seems to fluctuate. By adjusting the ratio of the flow rate on the side, stable hot water supply temperature control can be performed.

The best mode for carrying out the present invention will be described below with reference to the accompanying drawings.
A. Embodiment 1
[overall structure]
FIG. 1 shows an overall configuration of a water heater according to the present embodiment.
In this product, a hot water supply circuit (3) for supplying hot water to a tap (30) provided in a kitchen or a washroom, a bath circuit (4) for reheating the bathtub (40), and a floor heating mat ( 110) and a fan convector (111) are connected, and these circuits (3), (4), and (5) are heated by circulating hot water from a circulating heating circuit (2) described later. It has become so.
Details of each part will be described below.

《Circulating heating circuit (2)》
The gas burner (12), which is the heat source of the circulation heating circuit (2) for heating the hot water supply circuit (3), the bath circuit (4), and the heating circuit (5), has a large burner (12a), a medium burner (12b), and a small burner ( 12c), and gas is supplied to the gas burner (12) via the gas circuit (17). The gas circuit (17) is provided with a gas main valve (18) and a gas proportional valve (19) in order from the upstream side, and a large burner (12a) and a middle burner (12b) from the downstream side of the gas proportional valve (19). In the branch circuit to the small burner (12c), gas on-off valves (20a), (20b), and (20c) are provided separately.

  The circulation heat exchanger (13) heated by the gas burner (12) includes a sensible heat exchanger (13b) for recovering sensible heat of combustion exhaust from the gas burner (12), and a combustion from the gas burner (12). And a latent heat exchanger (13a) for recovering latent heat by cooling the exhaust gas below the dew point. For this reason, the circulation heat exchanger (13) and the gas burner (12) are housed in a can (21) having an exhaust port (22) opened at the upper end, and above the gas burner (12) The heat heat exchanger (13b) and the latent heat exchanger (13a) are arranged in this order from below. In addition, combustion air is supplied into the can body (21) from a lower air supply fan (26). Drain water generated when the combustion exhaust is cooled below the dew point by the latent heat exchanger (13a) is recovered by the drain pan (23) below it, and is provided in the drain pipe (24). It is drained after the pH is adjusted by the neutralizer (25).

  The circulating heating circuit (2) is connected to the circulating pump (15) shown on the right side of the can (21) → latent heat exchanger (13a) → sensible heat exchanger (13b) → circulating hot water temperature sensor (70) → It is a circuit that circulates in the order of the remnant distribution valve (28) → the heating path for hot water supply (29) → the primary side of the liquid-liquid heat exchanger (10) → the system turn (59) → the circulation pump (15).

《Hot water supply circuit (3)》
The hot water supply circuit (3) includes a flow rate regulator (31), a feed water temperature sensor (32) for detecting the incoming water temperature Tin, a feed water flow meter (33) for detecting the hot water flow rate Q1, and a liquid / liquid heat exchanger (10). This circuit is connected in the order of secondary side → hot water supply heated circuit (39) → bypass mixing valve (34) → mixed temperature sensor (35). The liquid-liquid heat exchanger (10) is bypassed by the bypass circuit (36), and hot water heated by the liquid-liquid heat exchanger (10) (hot water from the hot water supply heated circuit (39)) and the bypass circuit The cold water from (36) is mixed by the bypass mixing valve (34), and hot water at the hot water set temperature Tset set by the remote controller (6) (see FIG. 2) is fed to the outlet tap (30) side by the mixing. It comes to be supplied. In the present embodiment, the bypass mixing valve (34) corresponds to “hot water mixing means” which is a specific matter of the invention of claim 5.

《Heating circuit (5)》
The heating circuit (5) is composed of a circuit including a floor heating mat (110) and a fan convector (111). The circuit on the floor heating mat (110) side is the heating branch (54) branched from the outlet side of the latent heat exchanger (13a) in the circulation heating circuit (2) → the heating distribution valve (55) → the low temperature heating path (56) → floor heating mat (110) → sis turn (59). On the other hand, the circuit on the fan convector (111) side is connected in the order of sensible heat exchanger (13b) → circulating water temperature sensor (70) → high temperature heating circuit (57) → fan convector (111) → systern (59). ing. The middle of the high-temperature heating circuit (57) and the above-described heating distribution valve (55) are connected, and if necessary, a part of the high-temperature water supplied to the high-temperature heating circuit (57) is heated to the heating distribution valve ( 55) can be distributed to the low-temperature heating circuit (56).

《Bath circuit (4)》
The bath circuit (4) is a circuit that circulates from the bathtub (40) to the remedy pump (42) to the internal pipe (411) of the remedy heat exchanger (41) with a double pipe structure to the tub (40), High temperature water from the additional distribution valve (28) is supplied to the outer pipe (410) of the additional heat exchanger (41), and this is returned to the systern (59). In addition, the hot water supply circuit (46) drawn from the hot water supply circuit (3) is connected to the upstream side of the inner pipe (41) of the additional heat exchanger (41) in the bath circuit (4). When the hot water valve (47) provided in the hot water circuit (46) is opened, the hot water is filled in the bathtub (40).

"Remote controller"
As shown in FIG. 2, the remote control (6) is provided with a display screen (60) for displaying the operation state of hot water supply and heating, a hot water supply set temperature Tset, and the like. There are provided an operation switch (61) to perform, a heating switch (62) to be operated when using the floor heating mat (110), etc., a bath retreat switch (63), and a hot water switch (64). The remote controller (6) includes a hot water supply temperature setting unit (65) including a temperature raising button (65a) and a temperature lowering button (65b) for setting the hot water supply set temperature Tset, the hot water temperature of the bath, and the like. 1 is connected to a control device (not shown) incorporated in the water heater of FIG. 1 by a communication cable.

[Description of operation]
Next, each operation | movement, such as a hot water supply operation | movement by the said complex water heater, and heating operation, is demonstrated.
《Hot-water supply operation》
First, a schematic hot water supply operation will be described.
When the hot water tap (30) is opened with the operation switch (61) of the remote control (6) turned on and the feed water flow meter (33) detects a predetermined flow rate, the supply fan (26) and the circulation pump (15 ) Is activated, the gas burner (12) is combusted, and the hot water supply operation is started.

  During this hot water supply operation, the circulating hot water in the circulation heating circuit (2) collects latent heat from the combustion exhaust of the gas burner (12) when passing through the latent heat exchanger (13a), while the sensible heat exchanger (13b) When passing through the sensible heat, the sensible heat is recovered from the combustion exhaust and the temperature is raised. And this circulating hot water whose temperature has been heated is the heat exchanger for circulation (13) → circulating water temperature sensor (70) → remnant distribution valve (28) → heating path for hot water supply (29) → liquid-liquid heat exchanger (10) It is circulated in a circulation heating circuit (2) connected to the primary side → systern (59) → circulation pump (15) → circulation heat exchanger (13). Also, circulating hot water flowing through the circulating heating circuit (2) that is the primary side of the liquid-liquid heat exchanger (10) and hot water supply heating of the hot-water supply circuit (3) that is the secondary side of the liquid-liquid heat exchanger (10) Heated water flowing to the circuit (39) exchanges heat. Then, the mixing ratio of the high temperature water of the hot water supply heated circuit (39) that has passed through the liquid-liquid heat exchanger (10) and the cold water supplied from the bypass circuit (36) is adjusted by the opening of the bypass mixing valve (34). Then, the temperature of the mixed water is adjusted to the hot water supply set temperature Tset (temperature set by the remote controller (6)), and then supplied to the hot water tap (30) side.

  In the composite water heater according to the present embodiment, the necessary amount of heat (output number α) for obtaining hot water at the hot water set temperature Tset set by the remote controller (6) is supplied via the liquid-liquid heat exchanger (10). By reducing the pump speed of the circulation pump (15) as much as possible to the extent that it can be taken out to the circuit (3) side, the heat of the combustion exhaust gas generated by the gas burner (12) is converted into a circulation heat exchanger ( 13) is efficiently recovered (the heat efficiency of the circulation heat exchanger (13) is improved). Further, by setting the temperature of the inlet of the liquid-liquid heat exchanger (10) in the circulation heating circuit (2) (hereinafter referred to as “circulation inlet temperature TX”) to a high temperature of 85 ° C., Heat is recovered more efficiently by the circulation heat exchanger (13).

  Here, when the pump rotation speed of the circulation pump (15) is reduced as much as possible, and the circulation inlet temperature TX is set to a high temperature (85 ° C. in the present embodiment), the combustion exhaust generated by the gas burner (12) is reduced. The reason why heat can be efficiently recovered by the circulation heat exchanger (13) will be described.

{Reason why the heat of combustion exhaust can be efficiently recovered by the circulation heat exchanger (13) by reducing the pump speed of the circulation pump (15)}
FIG. 3 is a schematic diagram showing the relationship between the circulating heating circuit (2) and the hot water supply circuit (3) of FIG. FIG. 4 shows a flow rate of circulating hot water (hereinafter referred to as “circulation flow rate Q2”) and a gas burner (hereinafter referred to as “circulation flow rate Q2”) when the following experiment is performed using the composite water heater according to the present embodiment. It is a graph which shows the relationship of the combustion amount W etc. of 12). Specifically, the graphs F1, F2, and F3 in FIG. 4 show the circulation flow rate Q2 of the circulation heating circuit (2) and the circulating hot water returning from the liquid-liquid heat exchanger (10) to the circulation heat exchanger (13). The relationship between the temperature (hereinafter referred to as “return temperature TY”) and the graph G1 represents the relationship between the combustion amount W of the gas burner (12) and the return temperature TY.

The experiment for obtaining each graph in FIG. 4 was performed under the following conditions.
Hot water flow rate Q1 = 12.1L / min in the hot water supply circuit (3)
Incoming water temperature Tin = 17 ° C. on the primary side of the liquid-liquid heat exchanger (10) of the hot water supply circuit (3),
Hot water set temperature set with remote control (6) Tset = 60 ℃
Under the above experimental conditions, downstream of the junction of the bypass circuit (36) in the hot water supply circuit (3) (the outlet of the liquid-liquid heat exchanger (10) if the bypass circuit (36) is not provided) The circulating flow rate Q2 of the circulation heating circuit (2) and the combustion amount W of the gas burner (12) were changed within the limits that the hot water temperature Tout of the circulation heating circuit (2) can be maintained substantially at the hot water supply set temperature Tset.

  That is, while extracting the heat quantity of Eout = (60 ° C.−17 ° C.) × 12.1 L / min ÷ 25≈21 to the hot water supply circuit (3) which is the secondary side of the liquid-liquid heat exchanger (10), the circulation is performed. The flow rate Q2 and the combustion amount W of the gas burner (12) were changed.

Graphs F1, F2, and F3 in FIG. 4 show the relationship between the circulation flow rate Q2 and the return temperature TY when the circulation inlet temperature TX of the liquid-liquid heat exchanger (10) in the circulation heating circuit (2) is changed as a parameter. And
F1 is a graph of the circulation inlet temperature TX = 85 ° C. F2 is a graph of the circulation inlet temperature TX = 76 ° C. F3 is a graph of the circulation inlet temperature TX = 70 ° C.

  Also, the graph G1 in FIG. 4 shows the relationship between the combustion amount W of the gas burner (12) and the return temperature TY at the “circulation inlet temperature TX = 85 ° C.”, and the “return” shown in the table of FIG. Each point determined by each combination of “temperature TY” and “combustion amount W” is plotted on the graph of FIG.

Next, the contents of the graph F1 appearing in FIG. 4 will be specifically described.
As described above, the graph F1 shows the relationship between the return temperature TY and the circulation flow rate Q2 when the circulation inlet temperature TX is fixed at 85 ° C. In addition, the dew point of the combustion exhaust gas produced | generated with a gas burner (12) is 45 degreeC.

  In the graph F1, in the range where the return temperature TY is 56 ° C. or less and exceeds 45 ° C. (dew point) (the range of points P4 to P5), the return temperature TY is lower as the circulation flow rate Q2 is lower. This is due to the following reason.

  The lower the circulating flow rate Q2, the longer it takes for the circulating hot water in the circulating heating circuit (2) to pass through the primary side of the liquid-liquid heat exchanger (10). The time for cooling with the heated water in the hot water supply circuit (3), which is the secondary side, becomes longer. Accordingly, when the circulation flow rate Q2 is lowered, the return temperature TY to the circulation heat exchanger (13) is lowered.

  When the circulation inlet temperature TX of the liquid-liquid heat exchanger (10) is constant, the circulation heat exchanger (13) is easily cooled as the return temperature TY to the circulation heat exchanger (13) decreases. Therefore, the exhaust temperature after the combustion exhaust gas passes through the circulation heat exchanger (13) is lowered, and the heat from the combustion exhaust gas of the gas burner (12) is reduced by the amount that the exhaust temperature is lowered. ) Can be recovered a lot. That is, when the rotational speed of the circulation pump (15) is reduced (the circulation flow rate Q2 is reduced) to reduce the return temperature TY, the heat of the combustion exhaust can be efficiently recovered by the circulation heat exchanger (13). .

When the return temperature TY decreases (when the rotational speed of the circulation pump (15) decreases), the heat of the combustion exhaust can be efficiently recovered by the circulation heat exchanger (13) (circulation heat exchanger (13 It can be confirmed from the graph G1 in FIG. That is, when the range in which the return temperature TY decreases from 56 ° C. to 45 ° C. (dew point of combustion exhaust) (the range in which the circulation flow rate Q2 decreases from about 18 L / min to about 13 L / min) is seen, the combustion of the gas burner (12) It is confirmed that even if the amount W is decreased according to the curve between W1 and W2 in the graph G1, the amount of heat Eout taken out to the secondary side (hot water supply circuit (3)) of the liquid-liquid heat exchanger (10) can be kept constant. it can. In this way, the amount of heat Eout can be kept constant even when the combustion amount W of the gas burner (12) is decreased, as the return temperature TY decreases (with the decrease in the rotational speed of the circulation pump (15)). This is nothing but evidence that the heat of the combustion exhaust can be efficiently recovered by the circulation heat exchanger (13).
Thus, if the circulating flow rate Q2 is lowered to lower the return temperature TY, the thermal efficiency of the circulating heat exchanger (13) can be increased.

Next, when the return temperature TY enters an area of 45 ° C. (dew point) or less, the latent heat recovery in the latent heat exchanger (13a) starts, and the thermal efficiency of the circulating heat exchanger (13) is significantly increased. Further, when the circulating flow rate Q2 is reduced in the region where the return temperature TY is 45 ° C. or lower, the return temperature TY is lowered for the same reason as described above. When the temperature gradually decreases in the region where the return temperature TY is 45 ° C. or lower, the circulation heat exchanger (13) is easily cooled as described above, and thereby the latent heat recovery amount gradually increases. That is, even in the region where the return temperature TY is 45 ° C. or less, if the rotational speed of the circulation pump 15 is reduced (the circulation flow rate Q2 is reduced) to reduce the return temperature TY, the heat of the combustion exhaust is increased. It can be efficiently recovered by the circulation heat exchanger (13).
This can also be confirmed from the graph G1 in FIG. That is, when the return temperature TY is in the range of 45 ° C. or less (the circulation flow rate Q2 is in the range of about 13 L / min or less), the combustion amount W of the gas burner (12) is decreased according to the curve between W2 and W3 in the graph G1. However, it can be confirmed that the amount of heat Eout taken out to the secondary side (the hot water supply circuit (3)) of the liquid-liquid heat exchanger (10) can be kept constant.

  From the above, when the same amount of heat of Eout = 21 is taken out to the hot water supply circuit (3), the combustion amount of the gas burner (12) can be reduced by lowering the circulation flow rate Q2 and lowering the return temperature TY. Thus, the heat of the combustion exhaust can be efficiently recovered by the circulation heat exchanger (13). That is, the heat efficiency of the circulation heat exchanger (13) can be increased. Further, when the return temperature TY is lower than the dew point (45 ° C.) of the combustion exhaust of the gas burner (12), the above effect becomes remarkable.

  Next, when looking at the graph F2 when the circulation inlet temperature TX is 76 ° C. and the graph F3 when the circulation inlet temperature TX is 70 ° C., the circulation flow rate Q2 is decreased in this case as well as the graph F1. Thus, if the return temperature TY is lowered, the heat of the combustion exhaust can be efficiently recovered by the circulation heat exchanger (13). That is, it can be understood that the thermal efficiency is increased.

{Reason why the heat of combustion exhaust can be efficiently recovered by the heat exchanger for circulation (13) when the circulation inlet temperature TX is set to a high temperature}
As is apparent from FIG. 4, the return temperature TY1 corresponding to the lower end P1 of the graph F1 with the circulation inlet temperature TX = 85 ° C., the return temperature TY2 corresponding to the lower end P2 of the graph F2 with the circulation inlet temperature TX = 76 ° C., and The return temperature TY3 corresponding to the lower end P3 of the graph F3 with the circulation inlet temperature TX = 70 ° C. has a relationship of TY1 <TY2 <TY3. As will be described later, the point P1 is a lower limit value of the circulation flow rate Q2 at which the amount of heat of Eout = 21 can be extracted from the hot water supply circuit (3) which is the secondary side of the liquid-liquid heat exchanger (10). In other words, if the circulating flow rate is less than Q2, the amount of heat from the hot water supply circuit (3) becomes less than Eout = 21. Similarly, the points P2 and P3 are lower limit values of the circulation flow rate Q2 when TX = 76 ° C. and TX = 70 ° C. From this, when taking out the heat quantity of the same No. 21 to the secondary side of the liquid-liquid heat exchanger (10), if the circulation inlet temperature TX is set to a high temperature of 85 ° C., the temperature becomes lower (TX = 76 ° C., 70 ° C.). It can be understood that the return temperature can be lowered to TY1 compared to the case of (° C.), whereby the heat of the combustion exhaust gas of the gas burner (12) can be efficiently recovered by the circulation heat exchanger (13).

  As described above, the return temperature of the circulation heating circuit (2) to the circulation heat exchanger (13) is kept as low as possible (decreasing the circulation flow rate Q2), and the liquid-liquid heat in the circulation heating circuit (2). It can be understood that if the circulation inlet temperature TX of the exchanger (10) is set to a high temperature, the heat of the combustion exhaust generated by the gas burner (12) can be efficiently recovered by the circulation heat exchanger (13). That is, the thermal efficiency of the circulation heat exchanger (13) is improved, and as a result, the thermal efficiency of the entire composite water heater is also improved.

{About the lower limit of circulating flow Q2}
As described above, the heat of the combustion exhaust can be efficiently recovered by the circulation heat exchanger (13) by lowering the return flow rate TY by lowering the circulation flow rate Q2 of the circulation heating circuit (2). In order to obtain the hot water supply hot water having the temperature Tset, there is a lower limit value of the circulation flow rate Q2.

Next, the lower limit value of the circulation flow rate Q2 necessary for obtaining hot water supply hot water at the hot water supply set temperature Tset will be described.
This lower limit is determined by the incoming water temperature Tin of the heated water flowing from the inlet of the hot water supply circuit (3) to the secondary side of the liquid-liquid heat exchanger (10) and the hot water supply set temperature Tset set by the remote controller (6). Determined.

* Reason why the lower limit value of the circulation flow rate Q2 is determined by the incoming water temperature Tin According to the above-mentioned experiment for obtaining the graph F1 (see FIG. 4) of the circulation inlet temperature TX = 85 ° C., the circulation flow rate Q2 is 9 L / min (point P1) or less. Then, it was confirmed that the heat quantity of Eout = 21 could not be secured. Specifically, when the circulation flow rate Q2 is set to 8 L / min, the return temperature TY is about 22 ° C., and only the amount of heat of No. 20.2 can be secured and the hot water supply set temperature Tset = 60 ° C. cannot be maintained. It was.

  This is because when the circulation flow Q2 is reduced, the heat transfer wall of the liquid-liquid heat exchanger (10) (boundary wall of the circulation heating circuit (2) and the hot water supply circuit (3)) and the circulation hot water of the circulation heating circuit (2) It is considered that the heat transfer rate β2 (a function of the circulation flow rate Q2) decreases with the deterioration of the performance of the liquid-liquid heat exchanger (10), and as a result, hot water at the hot water supply set temperature Tset cannot be obtained. .

Next, the reason why the performance of the liquid-liquid heat exchanger (10) deteriorates as described above when the circulating flow rate Q2 is reduced will be described in detail.
The lower limit flow rate graphs Y1 to Y3 in FIG. 6 (a) show the circulation flow rate Q2 and the liquid-liquid heat exchanger (10) in the experiment in which (Tout−Tin) = ΔT in FIG. 3 and the hot water supply flow rate Q1 are kept constant. Is a graph showing the relationship between the output number α and the amount of heat that can be taken out by the hot water supply circuit (3) on the secondary side of the liquid-liquid heat exchanger (10).

  Y1 is a lower limit flow rate graph in an experiment in which the incoming water temperature Tin is set to 25 ° C., Y2 is a lower limit flow rate graph in an experiment in which the incoming water temperature Tin is set to 15 ° C., and T3. These are lower limit flow rate graphs in an experiment in which the incoming water temperature Tin is set to 5 ° C. From this lower limit flow rate graph, the following can be understood when the output number α1, which is the amount of heat extracted from the liquid-liquid heat exchanger (10) to the hot water supply circuit (3) side, is constant.

  That is, in the lower limit flow rate graph Y3 (Tin = 5 ° C.) where the incoming water temperature Tin is low, the heat quantity of the output number α1 can be taken out even if the circulating flow rate Q2 is set to a relatively small lower limit value Qc. In the flow rate graph Y2 (Tin = 15 ° C.), the heat quantity of the output number α1 cannot be taken out unless the circulating flow rate Q2 is increased to the lower limit value Qd. Further, in the lower limit flow rate graph Y1 (Tin = 25 ° C.) where the incoming water temperature Tin is higher, the heat quantity of the output number α1 cannot be extracted unless the circulation flow rate Q2 is further increased to the lower limit value Qe. From this, it can be understood that when the heat quantity of the same output number α1 is taken out, it is necessary to increase the circulation flow rate Q2 as the incoming water temperature Tin increases.

The reason is as follows.
In the case of the lower limit flow rate graph Y3 (Tin = 5 ° C) where the incoming water temperature Tin is low, the temperature difference Δt between the circulating heating circuit (2) and the hot water supply circuit (3) in the liquid-liquid heat exchanger (10) is large. The heat exchange amount Φ per unit time of the circulating hot water in the circulating heating circuit (2) and the heated water in the hot water supply circuit (3) in the liquid-liquid heat exchanger (10) portion is the liquid-liquid heat exchanger (10) Even if the heat transfer rate k is reduced, it can be ensured. This means
Heat exchange amount Φ = (k × A × Δt) Equation 1
It can be understood from. This is because Equation 1 indicates that if the temperature difference Δt is large, the heat exchange amount Φ can be maintained even if the heat passage rate k decreases.
Here, k is a heat transmission rate representing the performance of the liquid-liquid heat exchanger (10), and using the heat transfer coefficients β1 and β2 described above,
1 / k = (1 / β1) + (1 / β2) Equation 2
It is represented by
Β1 = a1 × Q1 ^b
β2 = a2 × Q2 ^b
It is. (However, a1, a2, and b are constants.)
A is the heat exchange area of the boundary wall (heat transfer wall) between the circulation heating circuit (2) and the hot water supply circuit (3) in the liquid-liquid heat exchanger (10).

  On the other hand, when the incoming water temperature Tin is high (in the case of the lower limit flow rate graphs Y1 and Y2), the temperature difference Δt between the circulating heating circuit (2) and the hot water supply circuit (3) in the liquid-liquid heat exchanger (10) is small. The heat exchange amount Φ per unit time of the circulating hot water in the circulating heating circuit (2) and the heated water in the hot water supply circuit (3) in the liquid-liquid heat exchanger (10) is It cannot be ensured unless the heat passage rate k is increased (see Equation 1).

  Therefore, when trying to extract the amount of heat of the same output number α1 to the secondary side (hot water supply circuit (3) side), the circulation in the liquid-liquid heat exchanger (10) is higher when the incoming water temperature Tin is higher than when it is low. It is necessary to increase the heat transfer rate k described above from the heating circuit (2) to the hot water supply circuit (3). In this case, assuming that the flow rate Q1 of the hot water supply circuit (3) in the liquid-liquid heat exchanger (10) is constant, the circulation heating circuit (2) and the hot water supply circuit (3) in the liquid-liquid heat exchanger (10) The heat transfer coefficient β1 between the boundary wall (heat transfer wall) and the hot water supply circuit (3) is constant. This is because the heat transfer coefficient β1 is a function of the flow rate Q1 as described above. Therefore, in order to increase the heat transfer rate k representing the performance of the liquid-liquid heat exchanger (10), the heat transfer wall (liquid-liquid heat) is increased by increasing the circulation flow rate Q2 of the circulation heating circuit (2). It is necessary to increase the heat transfer coefficient β2 between the circulation heating circuit (2) and the hot water supply circuit (3) in the exchanger (10) and the circulation heating circuit (2) (see Equation 2).

  Thus, it can be understood that if the heat quantity with the same output number α1 is taken out, it is necessary to increase the circulation flow rate Q2 in order to increase the heat transfer coefficient β2 as the incoming water temperature Tin increases.

  When the circulation flow rate Q2 is increased, the heat transmission rate k of the liquid-liquid heat exchanger (10) is increased and the performance is improved. On the contrary, when the circulation flow rate Q2 is decreased, the liquid-liquid heat exchange is performed. The heat transfer rate k of the vessel (10) is lowered and the performance is deteriorated.

If the performance of the liquid-liquid heat exchanger (10) deteriorates, hot water at the hot water supply set temperature Tset cannot be obtained.
That is, if it is going to take out the calorie | heat amount of the same output number (alpha) 1 from a liquid-liquid heat exchanger (10), it is necessary to increase the circulating flow rate Q2 as the incoming water temperature Tin becomes high, and the lower limit of the circulating flow rate Q2 is the incoming water temperature. It is determined by Tin.
As is clear from the above, in order to obtain hot water supply hot water at the hot water supply set temperature Tset, the circulation flow rate Q2 needs to be equal to or higher than the lower limit flow rate graphs Y1, Y2, and Y3 representing the lower limit values.

* Reason why the lower limit value of the circulating flow rate Q2 is determined by the hot water supply set temperature Tset Next, the reason why the lower limit value of the circulating flow rate Q2 is determined by the hot water supply set temperature Tset will be described.
The lower limit flow rate graphs Z1 to Z3 in (b) of FIG. 6 show the relationship between the circulation flow rate Q2 and the output number α of the liquid-liquid heat exchanger (10) when the experiment is performed under the same conditions as in (b). It is a graph which shows.

  The hot water supply set temperature Tset is a parameter, Z1 is a lower limit flow rate graph in an experiment in which the hot water supply set temperature Tset is set to 60 ° C., and Z2 is a lower limit flow rate graph in an experiment in which the hot water supply set temperature Tset is set to 50 ° C. Yes, Z3 is a lower limit flow rate graph in an experiment in which the hot water supply set temperature Tset is set to 37 ° C. From this lower limit flow rate graph, the following can be understood when the output number α3, which is the amount of heat extracted from the liquid-liquid heat exchanger (10) to the hot water supply circuit (3) side, is constant.

  That is, in the lower limit flow rate graph Z3 (Tset = 37 ° C.) where the hot water supply set temperature Tset is low, the heat quantity of the output number α3 can be taken out even if the circulation flow rate Q2 is set to a relatively small lower limit value Qf. In the high lower limit flow graph Z2 (Tset = 50 ° C.), the heat quantity of the output number α3 cannot be taken out unless the circulating flow rate Q2 is increased to the lower limit value Qg. Further, in the lower limit flow rate graph Z1 (Tset = 60 ° C.) where the hot water supply set temperature Tset is higher, the heat quantity of the output number α3 cannot be extracted unless the circulation flow rate Q2 is further increased to the lower limit value Qh. From this, it can be understood that if it is attempted to extract the amount of heat of the same output number α3, it is necessary to increase the circulation flow rate Q2 as the hot water supply set temperature Tset increases.

The reason is as follows.
First, it is necessary to increase the outlet temperature T′out of the liquid-liquid heat exchanger (10) as the hot water supply set temperature Tset increases.
Then, for the same reason as described for the incoming water temperature Tin, when the outlet temperature T′out is low, the circulation heating circuit (2) which is the primary side of the liquid-liquid heat exchanger (10) and the secondary side Since the temperature difference Δt of the hot water supply circuit (3) is large, per unit time of the circulating hot water of the circulating heating circuit (2) and the heated water of the hot water supply circuit (3) in the liquid-liquid heat exchanger (10) part The amount of exchange heat Φ tends to increase.

  On the other hand, when the outlet temperature T′out is high (in the case of the lower limit flow rate graphs Z1 and Z2), the circulating heating circuit (2) which is the primary side of the liquid-liquid heat exchanger (10) and the hot water supply circuit which is the secondary side ( Since the temperature difference Δt of 3) is small, the heat exchange amount Φ per unit time of the circulating hot water in the circulating heating circuit (2) and the heated water in the hot water supply circuit (3) in the liquid-liquid heat exchanger (10) is It tends to be small. Therefore, when trying to extract the amount of heat of the same output number α3 to the secondary side (hot water supply circuit (3) side), the liquid-liquid heat exchanger (10) is higher when the outlet temperature T'out is higher than when it is low. It is necessary to increase the heat transfer rate k described above from the circulating heating circuit (2) to the hot water supply circuit (3). In order to increase the heat transfer rate k representing the performance of the liquid-liquid heat exchanger (10), the circulation flow rate Q2 of the circulation heating circuit (2) must be increased as described above.

  Therefore, if it is going to take out the calorie | heat amount of the same output number (alpha) 3 from a liquid-liquid heat exchanger (10), it is necessary to increase the circulation flow rate Q2 as the hot water supply setting temperature Tset becomes high, and the lower limit of the circulation flow rate Q2 is a hot water supply. It is determined by the set temperature Tset.

  Next, even when the hot water supply set temperature Tset becomes high, the lower limit value of the circulation flow rate Q2 is set to the hot water supply set even when the outlet temperature T'out is kept constant by adjusting the mixing ratio of hot water with the bypass mixing valve (34). The reason determined by the temperature Tset will be described.

In order to keep the outlet temperature T'out constant even when the hot water supply set temperature Tset becomes high, it is necessary to increase the mixing ratio of hot water by the bypass mixing valve (34). Therefore, when the hot water supply set temperature Tset increases, it is necessary to increase the flow rate of the heated water (water in the hot water heated circuit (39)) flowing through the liquid-liquid heat exchanger (10). As a result, the heat demand on the hot water supply heated circuit (39) side of the liquid-liquid heat exchanger (10) increases, so that the circulation flow rate Q2 is set so as to supply an amount of heat corresponding to this from the circulation heating circuit (2). Need to increase.
Therefore, even when the outlet temperature T′out is kept constant by adjusting the mixing ratio of hot water with the bypass mixing valve (34), the lower limit value of the circulation flow rate Q2 is determined by the hot water supply set temperature Tset.

  Then, when it is attempted to take out a heat amount of a desired output number α from the circulation heating circuit (2) to the hot water supply circuit (3) at a predetermined hot water supply set temperature Tset, the circulation flow rate Q2 of the circulation heating circuit (2) is expressed as a lower limit flow graph Z1. , Z2 and Z3 need to be set in the region above.

* Relationship between the lower limit value of the circulation flow rate Q2 and the incoming water temperature Tin and the hot water supply set temperature Tset As described above, according to FIGS. When an amount of heat of several α is to be taken from the circulation heating circuit (2) to the hot water supply circuit (3), the lower limit flow rate graphs Y1, Y2, Y3 and the lower limit flow rate graphs Z1, Z2, Z3 determined by the incoming water temperature Tin and the hot water supply set temperature Tset It can be seen that the circulation flow rate Q2 may be set in the upper region of both.

A graph X2 in FIG. 7 is a combination of the lower limit flow rate graph Y2 in FIG. 6 (A) and the lower limit flow rate graph Z2 in (B), and the lower limit flow rate graph Y2 in the region where the output number α is smaller than the intersection R. And the lower limit flow rate graph Z2 is used in a region larger than the intersection point P. This graph X2 shows the circulation of the circulation heating circuit (2) when the heat quantity of the desired output number α is taken out to the hot water supply circuit (3) under the conditions of the incoming water temperature Tin = 15 ° C. and the hot water supply set temperature Tset = 50 ° C. It shows that the flow rate Q2 may be set in a region above the graph X2. That is, in the region where the hot water number α is smaller than the intersection point R, the circulating flow rate Q2 is set in the region above the lower limit flow rate graph Y2 depending on the incoming water temperature Tin, and in the region where the hot water number α is larger than the intersection point R, the hot water supply setting is set. The circulation flow rate Q2 may be set in a region above the lower limit flow rate graph Z2 depending on the temperature Tset.
As described above, in order to increase the thermal efficiency of the circulation heat exchanger (13) within a range in which the heat quantity of the desired output number α can be taken out to the hot water supply circuit (3), the following condition may be satisfied.

(A). In order to extract the amount of heat of the desired output number α to the hot water supply circuit (3), the circulation flow rate Q2 is set in the region above the graph X2 in FIG. 7 or the linear approximate graph X2 ′ above this.
(I). In order to keep the return temperature TY of the circulating heating circuit (2) to the circulating heat exchanger (13) as low as possible, the pump rotational speed of the circulating pump (15) is reduced.
Therefore, in the present embodiment, in order to satisfy the conditions (a) and (b) above, the hot water supply control according to the flowchart of FIG. 8 is executed in the composite water heater according to the present embodiment.

Next, the description returns to the hot water supply operation of the composite water heater shown in FIG.
In the present embodiment, the graph of FIG. 9 (hereinafter referred to as “control graph Xi”) in which the approximate graph X2 ′ of FIG. 7 is created for each combination of a plurality of hot water supply set temperatures Tset and incoming water temperatures Tin. It is designed to control hot water supply.

When the hot water supply control shown in the flowchart of FIG. 8 is started, it is first determined in step (ST1) whether the hot water flow meter (33) has detected a hot water supply start flow rate (whether the hot water tap (30) has been opened).
When the hot water supply flow meter (33) detects the hot water supply start flow rate, the hot water supply set temperature Tset set in the remote control (6) in step (ST2), and the flow into the liquid-liquid heat exchanger (10) flowing from the hot water supply circuit (3). The flow rate Q1 of the heating water and the incoming water temperature Tin are read.

  Next, in step (ST3), the combustion amount αa of the gas burner (12) necessary for heating and generating hot water at the hot water supply set temperature Tset is calculated, and then in step (ST4), the incoming water temperature Tin and the hot water set temperature Tset are calculated. Based on the above, a specific control graph Xi to be used is selected from the control graph Xi in FIG. The control graph Xi may be stored as a function in the microcomputer of the control device. Further, specific values of the incoming water temperature Tin and the hot water supply set temperature Tset specified by the control graph Xi may be stored as a table.

Next, step (ST5) is executed to obtain a provisional circulation flow rate Q2 (see FIG. 9) corresponding to the combustion amount αa of the gas burner (12), and then the circulation pump (15) is turned on in step (ST6). Operate.
In step (ST7), the air supply fan (26) is operated, and the gas burner (12) is combusted with the combustion amount αa.

  After that, execute step (ST8) and adjust the rotation speed of the circulation pump (15) so that the circulation inlet temperature TX to the liquid-liquid heat exchanger (10) of the circulation heating circuit (2) is as high as 85 ° C. To do. Specifically, when the circulation inlet temperature TX is lower than 85 ° C., the circulation inlet temperature TX is increased by decreasing the pump rotation speed of the circulation pump (15) (step (ST10)). The combustion amount αa = (Δt ′ × Q2) of the gas burner (12) is constant (where Δt ′ is the temperature difference between the inlet and outlet of the circulation heat exchanger (13)). This is because if the circulation flow rate Q2 in the heat exchanger (13) portion is reduced, the outlet temperature of the circulation heat exchanger (13) is increased and the circulation inlet temperature TX is increased. Contrary to the above, when the circulation inlet temperature TX is higher than 85 ° C., the circulation inlet temperature TX is decreased by increasing the pump rotation speed of the circulation pump (15) (step (ST9)). The circulation inlet temperature TX is adjusted to 85 ° C. As a result, during the subsequent hot water supply control, the circulating flow rate Q2 and the return temperature TY change along the graph F1 in FIG.

  Next, step (ST11) is executed, and the actual flow rate QR of the circulation heating circuit (2) determined from the pump rotational speed of the circulation pump (15) is calculated from the circulation flow rate Q2a (see FIG. 9) obtained from the control graph Xi. If it is determined that the value is greater than (), the pump rotational speed and the combustion amount of the gas burner (12) are decreased in step (ST12). On the other hand, if it is determined that the actual flow rate QR of the circulation heating circuit (2) is smaller than the above-described circulation flow rate Q2a obtained from the control graph Xi, the pump rotational speed and the combustion amount of the gas burner (12) are determined in step (ST13). Increase. As a result, the actual flow rate QR is matched with the circulation flow rate Q2a obtained from the control graph Xi (see FIG. 9), and the pump rotational speed of the circulation pump (15) is set as much as possible within the range where hot water at the hot water supply set temperature Tset is obtained. The heat of the combustion exhaust gas can be efficiently recovered by the circulation heat exchanger (13). That is, the heat efficiency of the circulation heat exchanger (13) is increased.

  Next, steps (ST14) to (ST16) are executed, and feedback control is performed to finely adjust the temperature of hot water supply hot water supplied to the hot water tap (30). Specifically, step (ST14) is executed, and when the hot water temperature detected by the mixed temperature sensor (35) is lower than the hot water supply set temperature Tset, the combustion amount of the gas burner (12) is increased in step (ST16), When the hot water temperature is higher than the hot water supply set temperature Tset, the combustion amount of the gas burner (12) is decreased in step (ST15).

Thereby, the temperature of the hot water supplied to the hot water tap (30) matches the hot water supply set temperature Tset.
In this embodiment, the hot water heated by the liquid-liquid heat exchanger (10) and the cold water from the bypass circuit (36) are mixed by the bypass mixing valve (34), and the remote controller (6 ) (See FIG. 2) etc. As described above, hot water hot water having a hot water supply set temperature Tset that is set is obtained. In this case, the hot water mixing ratio by the bypass mixing valve (34) is adjusted, whereby the outlet temperature T'out of the liquid-liquid heat exchanger (10) in the hot water heated circuit (39) becomes the hot water supply set temperature Tset. The temperature is controlled to be 10 ° C. lower. In the present embodiment, as described above, the hot water heated by the liquid-liquid heat exchanger (10) and the cold water from the bypass circuit (36) are mixed by the bypass mixing valve (34). Even if the temperature of the hot water supplied to the water etc. seems to fluctuate, a stable hot water temperature can be obtained by adjusting the ratio of the flow rate Q1 on the liquid-liquid heat exchanger (10) side and the flow rate on the bypass circuit (36) side. Control is possible.

《Heating operation》
Next, the heating operation will be described.
When the water supply flow meter (33) does not detect the hot water supply start flow rate when step (ST1) is executed, the heating operation is started when the heating switch (62) of the remote control (6) is confirmed to be turned on in step (ST18). Be started.

  During room heating by the fan convector (111), the relatively hot circulating hot water heated by both the latent heat exchanger (13a) and the sensible heat exchanger (13b) of the circulation heat exchanger (13) is circulated. The hot water temperature sensor (70) flows in the following sequence: arrangement portion → high temperature heating path (57) → fan convector (111) → systern (59), and indoor heating is performed in the fan convector (111).

  Also, during floor heating, the relatively low-temperature circulating hot water heated only by the latent heat exchanger (13a) of the circulation heat exchanger (13) is the heating branch (54) → heating distribution valve (55) → low temperature. It flows along the route of heating path (56) → floor heating mat (110) → systern (59), and floor heating is performed by the floor heating mat (110). In this case, the relatively high-temperature circulating hot water heated by the latent heat exchanger (13a) and the sensible heat exchanger (13b) is branched from the high-temperature heating path (57) as necessary, and the heating distribution valve (55 ) And the relatively hot circulating water from the heating branch (54) is mixed by the heating distribution valve (55) and supplied to the floor heating mat (110).

《Cheiling operation》
If turning on the heating switch (62) is not confirmed in step (ST18) described in the heating operation above, turning on the additional switch (63) of the remote control (6) is confirmed in step (ST19). The whispering operation is started.

  During reheating, a part of the circulating hot water in the recirculation heating circuit (2) flows through the recirculation distribution valve (28) → recuperation heat exchanger (41) → systern (59), and the recuperation heat exchanger (41 ) Is heated. On the other hand, the remedy pump (42) operates, and the bath water in the bathtub (40) circulates in the bath circuit (4) including the remedy heat exchanger (41). As a result, the bath water is heated in the recuperation heat exchanger (41) and the bath is refurbished.

<Water filling operation>
If it is not confirmed in step (ST19) described above in the reheating operation that the reheating switch (63) is turned on, if the hot water switch (64) on the remote control (6) is confirmed to be turned on in step (ST20), The filling operation to (40) is started.
During hot water filling, the hot water flowing out of the hot water supply circuit (3) described in the hot water supply operation described above branches downstream of the bypass mixing valve (34) and enters the hot water valve (47) → hot water supply circuit (46) → additional It is supplied by the path of the dredging pump (42) → bath circuit (4) → bathtub (40) and filled with hot water.

B. Embodiment 2
Next, the hot water supply operation by the composite water heater of Embodiment 2 of the present invention will be described with reference to the flowchart of FIG.
Control is performed in the same manner as in FIG. 8 until the rotational speed of the circulation pump (15) is adjusted so that the circulation inlet temperature TX to the liquid-liquid heat exchanger (10) of the circulation heating circuit (2) is as high as 85 ° C. Is done. In the present embodiment, when the control corresponding to step (ST8) in FIG. 8 is exited, step (ST30) in FIG. 10 is executed, and the hot water temperature detected by the mixed temperature sensor (35) is lower than the hot water supply set temperature Tset. In this case, after increasing the pump rotational speed of the circulation pump (15) in step (ST31), the combustion amount of the gas burner (12) is increased in step (ST32). On the other hand, when the tapping temperature is equal to or higher than the hot water supply set temperature Tset, the process branches from step (ST30) to step (ST33), and after reducing the pump rotational speed of the circulation pump (15), the gas burner ( Reduce the combustion amount of 12).

In this case, the pump rotation speed of the circulation pump (15) is set as much as possible within the range in which the hot water supply temperature of the hot water supply circuit (3) can be maintained at the hot water supply set temperature Tset by the control of the steps (ST30) (ST33) (ST34) Can be reduced. Accordingly, the circulating flow rate Q2 of the circulating hot water in the circulating heating circuit (2) is lowered and the return temperature TY to the circulating heat exchanger (13) is decreased. As described above, the combustion exhaust of the gas burner (12) Can be efficiently recovered by the circulation heat exchanger (13). That is, the thermal efficiency of the circulation heat exchanger (13) is improved, and as a result, the thermal efficiency of the entire composite water heater is also improved.
In each of the above embodiments, the circulation inlet temperature TX of the liquid-liquid heat exchanger (10) in the circulation heating circuit (2) is set to 85 ° C. If so, the heat of the combustion exhaust from the gas burner (12) can be efficiently recovered by the circulation heat exchanger (13).

Overall configuration diagram of a composite water heater according to an embodiment of the present invention The front view of the circulation heating circuit (2) used for the composite water heater which concerns on embodiment of this invention Schematic showing the relationship between the circulating heating circuit (2) and hot water supply circuit (3) in FIG. A graph showing the relationship between the circulation flow rate Q2 and the combustion amount W of the gas burner (12) in the experiment using the combined water heater according to the present embodiment Table showing the relationship between the circulation flow rate Q2 and the combustion amount W of the gas burner (12) in the experiment using the composite water heater according to the present embodiment It is a graph showing the relationship between the circulation flow rate Q2 and the output number α of the liquid-liquid heat exchanger (10). (A) is a graph when the incoming water temperature Tin changes, (b) is the hot water supply set temperature Tset. It is a graph when doing. A graph that combines the lower limit flow rate graph Y2 of FIG. 6 (a) and the lower limit flow rate graph Z2 of (b). The flowchart explaining operation | movement of the composite water heater which concerns on embodiment of this invention. The approximate graph X2 'shown in FIG. 7 is created for each combination of a plurality of hot water supply set temperatures Tset and incoming water temperatures Tin. The flowchart explaining the principal part of the hot water supply operation | movement of the composite water heater which concerns on 2nd Embodiment of this invention. Illustration of conventional example

Explanation of symbols

(2) ・ ・ ・ Circulating heating circuit
(3) ... Hot water supply circuit
(10) ... Liquid-liquid heat exchanger
(12) ・ ・ ・ Gas burner
(13) ・ ・ ・ Circulating heat exchanger
(15) ・ ・ ・ Circulating pump
(32) ... Water supply temperature sensor
(36) ... Bypass circuit

Claims (5)

A circulation heating circuit (2) having a circulation heat exchanger (13) and a circulation pump (15) heated by a gas burner (12);
A liquid-liquid heat exchanger (10) for performing heat exchange between heated water flowing through the hot water supply circuit (3) and circulating hot water flowing through the circulation heating circuit (2);
A water supply temperature sensor (32) for detecting an incoming temperature Tin of heated water flowing into the liquid-liquid heat exchanger (10) in the hot water supply circuit (3);
A hot water supply temperature setting section (65) for setting a hot water supply set temperature Tset of hot water and hot water to be taken out from the hot water supply circuit (3);
A flow rate sensor (33) for determining a flow rate Q1 of the hot water supply hot water;
By exchanging heat between the circulating hot water in the circulation heating circuit (2) circulated by the circulation pump (15) and the heated water in the hot water supply circuit (3) in the liquid-liquid heat exchanger (10), In a water heater that raises the temperature of water to be heated to the hot water supply set temperature Tset,
A water heater that reduces the pump rotation speed of the circulation pump (15) as long as the temperature of the hot water supply hot water can be maintained at the hot water supply set temperature Tset. In the water heater according to claim 1,
The water heater in which the pump rotational speed decreases as the incoming water temperature Tin decreases. In the water heater according to claim 1 or 2,
The water heater in which the pump rotation speed decreases as the hot water supply set temperature Tset decreases. In the water heater according to any one of claims 1 to 3,
A water heater in which the inlet temperature on the circulating heating circuit (2) side of the liquid-liquid heat exchanger (10) is set to 70 ° C or higher and 85 ° C or lower. In the water heater according to any one of claims 1 to 4,
A bypass circuit (36) for bypassing the liquid-liquid heat exchanger (10) in the hot water supply circuit (3) is provided,
Hot water mixing means for mixing hot water through the liquid-liquid heat exchanger (10) in the hot water supply circuit (3) and cold water through the bypass circuit (36) to make the hot water at the hot water supply set temperature Tset. A water heater is provided.

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