JP7792811B2 - Hot water system - Google Patents

Description

The present invention relates to a hot water supply system in which multiple water heaters are connected.

As seen in Patent Document 1, for example, a known system involves connecting multiple water heaters in parallel between a main water supply channel that supplies hot water and another main water supply channel that dispenses heated hot water. Hot water is supplied from the main water supply channel to one or more water heaters, and the hot water heated by the one or more water heaters is then supplied from the main water supply channel to a hot water supply target such as a hot water tap (a hot water supply target common to the multiple water heaters). In the system shown in Patent Document 1, a closable flow control valve is provided in the flow path that discharges heated hot water from each water heater into the main hot water supply channel.

In such systems, one of the multiple water heaters is typically set as the main water heater, and the others as auxiliary water heaters, with the main water heater primarily supplying hot water to hot water taps and other hot water supply targets. In situations where the main water heater alone is insufficient in capacity, the auxiliary water heater additionally heats the hot water supply water in addition to the main water heater. Furthermore, the flow control valve installed in the flow path that flows hot water from the auxiliary water heater to the main hot water supply line is kept closed when the auxiliary water heater is not heating the hot water supply water (when the auxiliary water heater is in standby mode).

Furthermore, with regard to individual water heaters, as seen in Patent Document 2, for example, it has been conventionally known that heated hot water can be distributed and supplied to multiple hot water supply targets, such as hot water taps and bathtubs.

JP 2017-78518 A JP 2014-152993 A

In a system such as that described in Patent Document 1, in which heated hot water can be supplied from one or more of a plurality of water heaters to a common hot water supply target (e.g., a hot water tap) for the plurality of water heaters, it is possible to connect each of the one or more water heaters to another hot water supply target (e.g., a bathtub), and configure the system so that in addition to being able to supply hot water from each water heater to the common hot water supply target, the other hot water supply target can also be supplied with hot water from the water heater connected to it.

For example, a hot water supply system can be configured that includes at least two water heaters, a first water heater and a second water heater, with the hot water supply passage of the first water heater connected to a first hot water supply target (e.g., a hot water tap) so as to supply hot water to the first hot water supply target, and the hot water supply passage of the second water heater connected to the first hot water supply target and the second hot water supply target (e.g., a bathtub) so as to distribute hot water to the first and second hot water supply targets, and further with a hot water supply on-off valve attached to the hot water supply passage of the second water heater that can open and close the hot water supply passage.

In this case, when the second water heater is not supplying hot water to the second hot water supply target portion, if a specified condition regarding the need for supplementary hot water supply from the second water heater to the first hot water supply target portion (e.g., a hot water tap) is met when the first water heater is supplying hot water to the first hot water supply target portion (such as a condition where the first water heater alone is insufficient), in addition to the hot water supply from the first water heater to the first hot water supply target portion, it is possible for the second water heater to supply hot water to the first hot water supply target portion as a supplementary supply.

However, when hot water is being supplied from the second water heater to the second hot water supply target portion (e.g., a bathtub), if a predetermined condition regarding the need for supplemental hot water supply from the second water heater to the first hot water supply target portion is met, as described above, the inventors of the present application have discovered through their investigations that if supplemental hot water is supplied from the second water heater to the first hot water supply target portion, the following problem occurs.

In other words, when hot water is being supplied to a first hot water supply target (e.g., a hot water tap) while the second hot water heater is supplying hot water to a second hot water supply target, if the second water heater is opened to supply hot water to the first hot water supply target in addition to supplying hot water from the first hot water heater to the first hot water supply target, a portion of the hot water water heated by the second water heater to supply hot water to the second hot water supply target is mixed with the hot water water heated by the first water heater and supplied to the first hot water supply target.

In this case, if the second water heater supplies hot water to the second hot water supply target unit at the target hot water supply temperature for the second hot water supply target unit set in advance by the user, and the first water heater supplies hot water to the first hot water supply target unit at the target hot water supply temperature for the first hot water supply target unit set in advance by the user, the temperature of the hot water supplied from the second water heater to the first hot water supply target unit will be temperature-controlled to the target hot water supply temperature for the second hot water supply target unit.

In addition, the temperature of the hot water supplied from the first water heater to the first hot water supply target unit is temperature-controlled to the target hot water supply temperature for the first hot water supply target unit. Therefore, the temperature of the hot water supplied to the first hot water supply target unit is a temperature different from both the target hot water supply temperature for the first hot water supply target unit and the target hot water supply temperature for the second hot water supply target unit (a temperature intermediate between both temperatures).

For this reason, particularly when there is a relatively large temperature difference between the target hot water supply temperature for the first hot water supply target unit and the target hot water supply temperature for the second hot water supply target unit, the temperature of the hot water supplied to the first hot water supply target unit will differ from both the target hot water supply temperature for the first hot water supply target unit and the target hot water supply temperature for the second hot water supply target unit set by the user, which may cause the user to feel uncomfortable or mistakenly believe that there is a malfunction in the hot water supply system.

The present invention was made in light of this background, and aims to provide a hot water supply system in which a first hot water supply target is connected to both a first hot water heater and a second hot water heater, and a second hot water supply target is further connected to the second hot water heater, that can supply hot water at an appropriate temperature when supplying hot water to the first hot water supply target while supplying hot water to the second hot water supply target.

In order to achieve the above-mentioned object, the hot water supply system of the present invention comprises a first water heater and a second water heater each having a water supply passage, a hot water supply passage, and a heating unit, and each configured to heat hot water supplied through the water supply passage in the heating unit and to dispense the heated hot water through the hot water supply passage, and a control device that controls the operation of the first water heater and the second water heater, wherein the hot water supply passage of the first water heater is connected to a first hot water supply target portion so as to be able to supply hot water to the first hot water supply target portion, and the hot water supply passage of the second water heater is connected to the first hot water supply target portion and the second hot water supply target portion so as to be able to distribute the hot water to the first hot water supply target portion, and further, an on-off valve that can open and close the passage is assembled to the passage that distributes hot water from the hot water supply passage of the second water heater to the first hot water supply target portion,
a flow rate regulating valve capable of regulating the flow rate of hot water supply water flowing from the first hot water heater to the first hot water supply target part;
The control device has a function of executing a first control process to control the operation of the first water heater and the flow rate adjustment valve so that hot water at a first target hot water temperature, which is a target temperature for the hot water for the first hot water supply target portion, is supplied from the first water heater to the first hot water supply target portion when a predetermined condition regarding the need for hot water supply from the second water heater to the first hot water supply target portion is met while hot water supply from the second water heater to the second hot water supply target portion is stopped and the operation of the on-off valve and the second water heater so that hot water at the first target hot water temperature is supplied from the second water heater to the first hot water supply target portion while the on-off valve is open;
When hot water is supplied to the first hot water supply target portion while the operation of the second hot water heater is being controlled so that the second hot water heater supplies hot water to the second hot water supply target portion, the system is configured to have the function of executing a second control process that controls the operation of the on-off valve and the second water heater so that hot water at a second target hot water supply temperature, which is the target temperature of the hot water for the second hot water supply target portion, is supplied from the second water heater to the second hot water supply target portion, regardless of whether the specified condition is met, and controls the operation of the first water heater and the flow rate control valve so that hot water at the first target hot water supply temperature is supplied from the first water heater to the first hot water supply target portion (first invention).

According to the first aspect of the invention, when hot water is being supplied from the first water heater to the first hot water supply target unit while hot water supply from the second water heater to the second hot water supply target unit is stopped, if a predetermined condition regarding the need for hot water supply from the second water heater to the first hot water supply target unit is met, the first control process is executed, so that in addition to hot water being supplied from the first water heater to the first hot water supply target unit, hot water can also be supplied from the second water heater to the first hot water supply target unit. In this case, hot water at the first target hot water supply temperature can be supplied from both the first and second water heaters.

Furthermore, when hot water is supplied to the first hot water supply target unit while the operation of the second hot water heater is being controlled to supply hot water from the second hot water heater to the second hot water supply target unit, the second control process is executed regardless of whether the specified condition is met, thereby allowing hot water to be supplied to the first hot water supply target unit only from the first hot water heater, regardless of whether the specified condition is met. In this case, by controlling the operation of the flow rate adjustment valve, the flow rate of hot water supplied from the first hot water heater to the first hot water supply target unit can be reduced, allowing hot water at the first target hot water temperature to be supplied to the first hot water supply target unit.

Therefore, according to the first invention, in either case where the specified condition is met when hot water is being supplied from the first water heater to the first hot water supply target portion while hot water supply from the second water heater to the second hot water supply target portion is stopped, or where the specified condition is met when hot water is being supplied to the first hot water supply target portion while the operation of the second water heater is controlled so that hot water is supplied from the second water heater to the second hot water supply target portion, hot water at the first target hot water supply temperature can be supplied to the first hot water supply target portion, thereby preventing the user from feeling uncomfortable with the temperature of the hot water.
Therefore, according to the first aspect of the present invention, when supplying hot water to the second hot water supply target, hot water can be supplied at an appropriate temperature when supplying hot water to the first hot water supply target.

In the first invention, the control device may be configured to execute the second control process when supplying hot water to the first hot water supply target portion while controlling the operation of the second hot water heater so that the second hot water heater supplies hot water to the second hot water supply target portion and when the second target hot water supply temperature does not match the first target hot water supply temperature; and when the second target hot water supply temperature matches the first target hot water supply temperature, control the operation of the on-off valve and the second hot water heater so that the second hot water heater supplies hot water at the first target hot water supply temperature or the second target hot water supply temperature to the first hot water supply target portion and the second hot water supply target portion while opening the on-off valve, and execute a third control process to control the operation of the first hot water heater and the flow rate adjustment valve so that the first hot water heater supplies hot water at the first target hot water supply temperature or the second target hot water supply temperature to the first hot water supply target portion (second invention).

In the present invention, the second target hot water supply temperature matching the first target hot water supply temperature does not necessarily mean that the second target hot water supply temperature exactly matches the first target hot water supply temperature, but may also mean that the second target hot water supply temperature almost matches (approximately matches) the first target hot water supply temperature.

According to the second aspect of the invention, when hot water is supplied to a first hot water supply target portion while the operation of the second hot water supply device is being controlled so that the second hot water supply device supplies hot water to the second hot water supply target portion, the second control process is executed if the second target hot water supply temperature does not match the first target hot water supply temperature, while the third control process is executed if the second target hot water supply temperature matches the first target hot water supply temperature. This reduces the number of situations in which the flow control valve reduces the flow rate of hot water to the first hot water supply target portion even when the specified condition is met. This makes it possible to improve the convenience of the hot water supply flow rate for the first hot water supply target portion.

In the above first invention, when the first hot water supply target portion is a hot water tap and the second hot water supply target portion is a bathtub, the control device is configured to execute the second control process when supplying hot water to the first hot water supply target portion while controlling the operation of the second hot water heater so that the second hot water supply target portion is supplied with hot water from the second hot water heater, if the second target hot water supply temperature is lower than the first target hot water supply temperature or is a temperature lower than the first target hot water supply temperature, and if the second target hot water supply temperature is a temperature higher than the first target hot water supply temperature or is higher than the first target hot water supply temperature, with the on-off valve open, control the operation of the on-off valve and the second water heater so that the second water heater supplies hot water at the first target hot water supply temperature to the first hot water supply target portion and the second hot water supply target portion, and control the operation of the first water heater and the flow rate adjustment valve so that the first water heater supplies hot water at the first target hot water supply temperature to the first hot water supply target portion (third invention) (invention).

According to this, when hot water is supplied to a first hot water supply target (hot water tap) while the operation of the second hot water heater is controlled to supply hot water from the second hot water heater to a second hot water supply target (bathtub), the second control process is executed if the second target hot water supply temperature is lower than the first target hot water supply temperature or is at or below the first target hot water supply temperature, while the fourth control process is executed if the second target hot water supply temperature is at or above the first target hot water supply temperature or is higher than the first target hot water supply temperature.This reduces the number of situations in which the flow control valve reduces the flow rate of hot water to the first hot water supply target (hot water tap) even when the specified condition is met.This makes it possible to improve the convenience of the hot water supply flow rate to the first hot water supply target (hot water tap).

In addition, in the fourth control process, which is executed when the second target hot water supply temperature is equal to or higher than the first target hot water supply temperature, hot water at the first target hot water supply temperature is supplied from the second water heater to the first hot water supply target area (hot water tap) and the second hot water supply target area (bathtub). Therefore, although the hot water supply temperature to the second hot water supply target area (bathtub) will be lower than the second target hot water supply temperature, after hot water supply (filling) to the second hot water supply target area (bathtub) is completed, so-called reheating can be performed, and the hot water used to fill the second hot water supply target area (bathtub) can be heated to the second target hot water supply temperature.

In the third aspect of the invention, the control device may be further configured to execute a third control process in which, when a request for hot water supply to the first hot water supply target unit occurs while controlling the operation of the second hot water heater to supply hot water from the second hot water heater to the second hot water supply target unit, if the second target hot water supply temperature matches the first target hot water supply temperature, the control device controls the operation of the on-off valve and the second hot water heater so that the second hot water heater supplies hot water at the first target hot water supply temperature or the second target hot water supply temperature to the first hot water supply target unit and the second hot water supply target unit, while opening the on-off valve, and controls the operation of the first hot water heater and the flow rate adjustment valve so that the first hot water heater supplies hot water at the first target hot water supply temperature or the second target hot water supply temperature to the first hot water supply target unit (fourth aspect of the invention).

As in the second invention, the second target hot water supply temperature matching the first target hot water supply temperature does not necessarily mean that the second target hot water supply temperature exactly matches the first target hot water supply temperature, but may also mean that the second target hot water supply temperature almost matches (approximately matches) the first target hot water supply temperature.

According to the fourth aspect of the invention, the third control process is executed when the second target hot water supply temperature matches (including when they are nearly the same) the first target hot water supply temperature. This further reduces the number of situations in which the flow control valve reduces the flow rate of hot water to the first hot water supply target (hot water tap), even when the specified condition is met. This further increases the convenience of the hot water supply flow rate to the first hot water supply target (hot water tap).

1 is a diagram showing the overall configuration of a hot water supply system according to an embodiment of the present invention. 4 is a flowchart showing the process of operation control of the main water heater (first water heater) in the first embodiment. 4 is a flowchart showing the process of controlling the operation of the auxiliary water heater (second water heater) in the first embodiment. 10 is a flowchart showing the process of operation control of the main water heater (first water heater) in the second embodiment. 10 is a flowchart showing the process of controlling the operation of an auxiliary water heater (second water heater) in the second embodiment.

[First embodiment]
A first embodiment of the present invention will be described below with reference to FIGS. 1 to 3. Referring to FIG. 1, a hot water supply system 1 of this embodiment includes multiple (e.g., two) water heaters 2A and 2B. Each of the water heaters 2A and 2B includes a heat source unit 3 having the same configuration as the heat source unit for heating hot water. A hot water tap CL located in a kitchen, washroom, bathroom, or the like is connected to the heat source unit 3 of each of the water heaters 2A and 2B as a common hot water supply target. A bathtub BTB is also connected to the water heater 2B as another hot water supply target. In this embodiment, a bathtub is not connected to the water heater 2A.

Here, of the water heaters 2A and 2B, the water heater 2A is the main water heater that supplies hot water to the hot water tap CL, and will hereinafter be referred to as the main water heater 2A. Furthermore, the water heater 2B is a water heater that supplementarily supplies hot water to the hot water tap CL when the hot water supply capacity of the main water heater 2A alone is insufficient, and will hereinafter be referred to as the auxiliary water heater 2B. In this embodiment, the main water heater 2A corresponds to the first water heater in the present invention, and the auxiliary water heater 2B corresponds to the second water heater in the present invention. Furthermore, the hot water tap CL and the bathtub BTB correspond to the first hot water supply target and the second hot water supply target, respectively, in the present invention. In the following description, when there is no need to distinguish between the water heaters 2A and 2B, they will be simply referred to as the water heater 2.

To give a representative explanation of the configuration of the heat source unit 3 of the auxiliary water heater 2B to which the bathtub BTB is connected, the heat source unit 3 includes a water supply channel 10 to which hot water is supplied from a water supply source (not shown), a first heating unit 11 that heats the hot water supplied from the water supply channel 10, a hot water supply channel 12 that supplies the hot water heated by the first heating unit 11, a second heating unit 13 that heats the bathtub water in the bathtub BTB, a circulation water channel 14 that circulates the bathtub water between the second heating unit 13 and the bathtub BTB, and a bath filling water channel 15 that supplies the hot water heated by the first heating unit 11 from the hot water supply channel 12 via the circulation water channel 14 to the bathtub BTB.

The water supply passage 10 branches off from the upstream water supply passage 4, which is common to the water heaters 2A and 2B, and hot water is supplied to each water supply passage 10 from a water source (not shown) via the upstream water supply passage 4. The downstream side of the hot water supply passage 12 merges with the downstream hot water supply passage 5 (the downstream hot water supply passage 5 common to the water heaters 2A and 2B) to which the hot water tap CL is connected at its downstream end, and hot water is supplied from the hot water supply passage 12 to the hot water tap CL via the downstream hot water supply passage 5. Note that while only a single hot water tap CL is shown in Figure 1, multiple hot water taps may be connected to the downstream hot water supply passage 5.

The first heating unit 11, although not shown in detail, is composed of, for example, a known combustion-type heating device including a burner and a heat exchanger. In this case, the first heating unit 11 circulates hot water supplied from the water supply line 10 through the heat exchanger into the hot water supply line 12, and heats the hot water flowing through the heat exchanger with combustion heat generated by the combustion operation of the burner. The first heating unit 11 may also be equipped with a bypass path that allows hot water to flow from the water supply line 10 into the hot water supply line 12 without passing through the heat exchanger, and a bypass ratio adjustment valve for adjusting the bypass ratio, which is the ratio between the flow rate of hot water flowing through the bypass path and the flow rate of hot water flowing through the heat exchanger.

The water supply line 10 is fitted with a water supply volume adjustment valve 16 for adjusting the water supply volume, which is the flow rate of hot water flowing through the water supply line 10, and a flow rate sensor 17 for detecting this water supply volume. The hot water supply line 12 is fitted with a temperature sensor 18 for detecting the hot water temperature, which is the temperature of the hot water supplied through the hot water supply line 12 to the hot water tap CL or bathtub BTB downstream. The water supply volume adjustment valve 16 of the main hot water heater 2A corresponds to the flow rate adjustment valve in this invention.

The circulation water channel 14 comprises a return water channel 14a, which flows bathwater from inside the bathtub BTB to the second heating section 13, and an outward water channel 14b, which flows bathwater from the second heating section 13 into the bathtub BTB. One of the return water channel 14a or the outward water channel 14b, for example the return water channel 14a, is fitted with an electric pump 19 as a power source for circulating bathwater in the circulation water channel 14. The end of each of the return water channel 14a and the outward water channel 14b on the bathtub BTB side is connected to a pouring spout Ba formed in the side wall near the bottom of the bathtub BTB.

The second heating section 13, while not shown in detail, is composed of a known combustion-type heating device including a burner and a heat exchanger, similar to the first heating section 11. In this case, the heat exchanger of the second heating section 13 is connected to the return water channel 14a and the outward water channel 14b so that bathwater flows from the return water channel 14a to the outward water channel 14b. The second heating section 13 is configured so that the bathwater flowing through the circulation water channel 14 by the operation of the pump 19 is heated in the heat exchanger by the combustion heat generated by the combustion operation of the burner.

Additionally, the first heating section 11 and the second heating section 13 of the heat source unit 3 are not limited to combustion-type heating devices. For example, the first heating section 11 and the second heating section 13 may each be equipped with an electric heating device or a heat pump-type heating device instead of or in addition to a combustion-type heating device.

One of the return water channel 14a and the outward water channel 14b, for example the return water channel 14a, is equipped with a temperature sensor 20 that detects the temperature of the bathtub water, a water flow switch 21 that detects the presence or absence of water flow in the circulation water channel 14, and a water level sensor 22 that detects the water level in the bathtub BTB. The temperature sensor 20, water flow switch 21, and water level sensor 22 may also be provided on the outward water channel 14b.

The filling water channel 15 branches off from the hot water supply channel 12 and merges into one of the return water channel 14a and the outward water channel 14b of the circulation water channel 14, for example, the return water channel 14a. The filling water channel 15 is fitted with a filling solenoid valve 23 that can open and close the filling water channel 15, and a flow rate sensor 24 that detects the flow rate of hot water supplied from the hot water supply channel 12 through the filling water channel 15 to the bathtub BTB (the flow rate of hot water supplied to the bathtub BTB).

The heat source unit 3 of the auxiliary water heater 2B is configured as described above. The heat source unit 3 of the main water heater 2A is configured in the same way as the auxiliary water heater 2B. Therefore, the configuration of the heat source unit 3 of the main water heater 2A will be given the same reference numerals as the heat source unit 3 of the auxiliary water heater 2B, and explanations will be omitted. However, in this embodiment, a bathtub is not connected to the circulation water channel 14 of the heat source unit 3 of the main water heater 2A.

In addition, in the hot water supply system 1 of this embodiment, a hot water supply on-off valve 26 capable of opening and closing the hot water supply passage 12a is installed in the hot water supply passage 12 of the auxiliary hot water heater 2B, in the passage 12a downstream of the branch point of the hot water filling passage 15 (the passage 12a that flows hot water from the hot water supply passage 12 to the hot water tap CL via the downstream hot water supply passage 5). The hot water supply on-off valve 26 corresponds to the on-off valve in the present invention and is composed of a solenoid valve or the like.

Additionally, in FIG. 1, the hot water supply on-off valve 26 is provided outside the heat source unit 3 of the auxiliary hot water heater 2B, but it may also be mounted on the heat source unit 3. The hot water supply on-off valve 26 may also have the function of adjusting the flow rate of hot water. The auxiliary hot water heater 2B may also omit the water supply volume adjustment valve 16. The main hot water heater 2A may also have a flow rate adjustment valve, instead of the water supply volume adjustment valve 16, in the hot water supply path 12, in the flow path 12a downstream of the branch point of the water filling path 15.

Each of the water heaters 2A, 2B further includes a control device 31A, 31B that has the function of controlling the operation of the respective heat source unit 3. The control devices 31A, 31B are mounted on the heat source unit 3 of each of the water heaters 2A, 2B. The hot water supply system 1 also includes a kitchen remote control 32A installed in the kitchen or the like, and a bathroom remote control 33B installed in the bathroom where the bathtub BTB is installed, as remote controls for operating the system.

Although detailed illustrations are omitted, the kitchen remote control 32A is equipped with an operation unit that includes an ON/OFF switch (ON/OFF switch) for operating the hot water supply operation that supplies hot water to the hot water tap CL, an operation switch for setting the target hot water temperature, and an operation switch for instructing the execution of a water filling operation that fills the bathtub BTB, as well as a display unit that displays various information related to the operation of the water heaters 2A and 2B, and a sound unit that outputs alarm sounds and audio information.

In addition, although detailed illustrations are omitted, the bathroom remote control 33B is equipped with an operation unit that includes operation switches for setting the target temperature of the bathwater in the bathtub BTB, the target water level of the bathwater, and the target hot water temperature, as well as operation switches for instructing the execution of a bath filling operation corresponding to each bathtub BTB, a display unit that displays various information related to bath filling, etc., and a sound unit that outputs alarm sounds and audio information.

Control devices 31A and 31B are each composed of one or more electronic circuit units including a processor such as a microcomputer, memory, interface circuits, etc., and are capable of communicating with each other. Furthermore, control device 31A of water heater 2A can communicate with kitchen remote control 32A, and control device 31B of water heater 2B can communicate with bathroom remote control 33B. Note that kitchen remote control 32A may be able to communicate with control device 31B of water heater 2B instead of or in addition to control device 31A of water heater 2A.

Each of the control devices 31A and 31B has the function of controlling the operation of the heat source unit 3 of the corresponding water heater 2A or 2B through functions realized by the implemented hardware configuration and program (software configuration). The control device 31B also has the function of controlling the operation of the on-off valve 26. However, the control device 31A may also have the function of controlling the operation of the on-off valve 26.

Next, the operation of the hot water supply system 1 of this embodiment will be explained. First, the basic operation of the hot water filling operation, which supplies hot water (fills the bathtub BTB), will be explained. The initial state immediately after the hot water supply operation is turned on using the kitchen remote control 32A or bathroom remote control 33B, is the standby state of the main hot water heater 2A and auxiliary hot water heater 2B. In this standby state, the hot water supply on/off valve 26 of the auxiliary hot water heater 2B is controlled to be closed by the control device 31B. In addition, the water supply amount adjustment valves 16 of each of the main hot water heater 2A and auxiliary hot water heater 2B are controlled to be fully open by the control devices 31A and 31B, respectively.

In the above standby state, when an operation is performed using the kitchen remote control 32A or bathroom remote control 33B to command the execution of a bathtub filling operation for the bathtub BTB, the control device 31B of the auxiliary water heater 2B controls the bathtub filling solenoid valve 23 to open, and also starts the operation of the first heating unit 11 (burner combustion operation). This starts the supply of hot water (filling) to the bathtub BTB.

The control device 31B then controls the amount of heating from the first heating unit 11 so that the hot water temperature detected by the temperature sensor 18 of the auxiliary hot water heater 2B matches or nearly matches the target hot water temperature for filling the bathtub BTB. In this case, the target hot water temperature for filling the bathtub is basically the bath filling set temperature, which is the temperature most recently set by the user on the bathroom remote control 33B (or kitchen remote control 32A). This allows hot water to be supplied (filled) to the bathtub BTB at the bath filling set temperature. The bath filling set temperature corresponds to the second target hot water temperature in this invention.

The control device 31B calculates the amount of hot water required to raise the bathtub water level in the bathtub BTB to the set water level, which is the target value most recently set by the bathroom remote control 33B (or kitchen remote control 32A). The control device 31B then supplies hot water to the bathtub BTB until the amount of hot water supplied to the bathtub BTB (accumulated flow rate) detected based on the output of the flow rate sensor 24 in the bath filling water channel 15 reaches the calculated required amount of hot water. Once the required amount of hot water is reached, the control device 31B stops operation of the first heating unit 11 and closes the bath filling solenoid valve 23. This completes filling the bathtub BTB to the set water level.

The control device 31B then determines whether the bathwater temperature detected by the temperature sensor 20 of the auxiliary water heater 2B has reached the bathwater filling set temperature, which is the target bathwater temperature for filling the bath. If the determination is negative due to bathwater water remaining in the bathtub BTB when the bathwater filling operation begins, the control device 31B activates the second heating unit 13 and pump 19 of the auxiliary water heater 2B to heat and circulate the bathwater in the bathtub BTB through the circulation water path 14 until the detected bathwater water temperature reaches the bathwater filling set temperature (reheating the bathwater).
In the hot water supply system 1 of this embodiment, the hot water filling operation for filling the bathtub BTB with hot water is carried out as described above with the hot water supply opening/closing valve 26 of the auxiliary hot water heater 2B in a closed state.

Next, the operation of supplying hot water to the hot water tap CL will be explained with reference to Figures 2 and 3. In the following explanation, unless otherwise specified, "filling operation" refers to the operation during the process of filling the bathtub BTB with hot water, and does not include the operation during the reheating process that may be performed afterwards.

The control device 31A of the main water heater 2A executes the control process shown in the flowchart of Figure 2 regarding the supply of hot water to the hot water tap CL. When the main water heater 2A is in standby mode, the control device 31A executes a determination process in STEP 1 to determine whether water supply to the hot water tap CL has started, until the determination result becomes affirmative.

Here, by opening the hot water tap CL, water begins to flow from the upstream water supply passage 4 to the hot water tap CL via the water supply passage 10, first heating section 11, and hot water passage 12 of the main hot water heater 2A, and the downstream hot water passage 5. Then, in STEP 1, the control device 31A determines whether water has begun to flow to the hot water tap CL based on whether the flow rate detected by the flow rate sensor 17 of the main hot water heater 2A is equal to or greater than a predetermined flow rate.

When the result of the determination in STEP 1 becomes positive due to the start of water flow to the hot water tap CL, the control device 31A starts the hot water supply operation of the main hot water heater 2A in STEP 2. In this case, the operation of the first heating section 11 of the main hot water heater 2A (burner combustion operation) is started, thereby starting the hot water supply operation that supplies hot water from the main hot water heater 2A to the hot water tap CL.

During this hot water supply operation, the control device 31A controls the temperature of the hot water supplied to the hot water tap CL by controlling the amount of heat (burner combustion amount) of the first heating unit 11 so that the hot water temperature detected by the temperature sensor 18 of the main hot water heater 2A matches or nearly matches the target hot water temperature, which is its target value. In this case, the hot water setting temperature, which is the temperature most recently set by the user using the kitchen remote control 32A or bathroom remote control 33B for hot water supply to the hot water tap CL, is used as the target hot water temperature. As a result, hot water is supplied to the hot water tap CL at the hot water setting temperature. The hot water setting temperature corresponds to the first target hot water temperature in this invention.

Next, in STEP 3, the control device 31A determines whether the flow of water to the hot water tap CL has been stopped (whether the hot water tap CL has been closed). In this case, the control device 31A determines whether the flow of water to the hot water tap CL has been stopped based on whether the flow rate detected by the flow rate sensor 17 of the main hot water heater 2A has fallen below a predetermined flow rate.

If the determination result in STEP 3 is positive (water supply to the hot water tap CL is stopped), the control device 31A stops operation of the first heating section 11 of the main hot water heater 2A in STEP 10. This stops the hot water supply operation of the main hot water heater 2A.

If the determination result in STEP 3 is negative (water continues to flow to the hot water tap CL), the control device 31A determines in STEP 4 whether the hot water heat quantity, which is the amount of heat required to heat the hot water supplied to the hot water tap CL to the hot water set temperature, is greater than the upper limit heat quantity, which is the upper limit of the amount of heat that can be input to the hot water from the first heating section 11 of the main hot water heater 2A.

Here, the hot water heat quantity is calculated by multiplying the difference between the hot water setting temperature and the water supply temperature (the temperature of the hot water water flowing through the water supply passage 10 of the main hot water heater 2A) by the hot water supply flow rate to the hot water tap CL. The water supply temperature is detected by a temperature sensor (not shown), or can be estimated from the flow rate detected by the flow rate sensor 17, the hot water temperature detected by the temperature sensor 18, and the set value of the heating amount of the first heating section 11. The flow rate detected by the flow rate sensor 17 of the main hot water heater 2A can also be used as the hot water supply flow rate to the hot water tap CL.

Additionally, in this embodiment, the positive determination result in STEP 4 (the hot water supply heat quantity > the upper limit heat quantity) corresponds to the predetermined condition in the present invention (the predetermined condition regarding whether or not hot water needs to be supplied from the auxiliary hot water heater 2B to the hot water tap CL) being met.

If the determination result in STEP 4 is negative (the amount of hot water heat <= the upper limit of the amount of hot water heat), the control device 31A repeats the process from STEP 3. On the other hand, if the hot water supply flow rate to the hot water tap CL is high, for example, the determination result in STEP 4 will be positive (the amount of hot water heat > the upper limit of the amount of hot water heat). In this case, the control device 31A next determines in STEP 5 whether the auxiliary hot water heater 2B is currently in the hot water filling operation. In this case, information indicating whether the auxiliary hot water heater 2B is currently in the hot water filling operation is obtained through communication between the control device 31A and the control device 31B of the auxiliary hot water heater 2B.

If the determination result in STEP 5 is negative (the auxiliary water heater 2B is not currently filling the water), the control device 31A requests the control device 31B of the auxiliary water heater 2B to start auxiliary hot water supply from the auxiliary water heater 2B to the hot water tap CL in STEP 6. In response, auxiliary hot water supply from the auxiliary water heater 2B to the hot water tap CL is started as described below. Consequently, by reducing the flow rate of hot water supply water flowing from the upstream water supply line 4 into the water supply line 10 of the main water heater 2A, the hot water supply water can be heated to the hot water supply setting temperature in the main water heater 2A.

Next, in STEP 7, the control device 31A determines whether the flow of water to the hot water tap CL has been stopped, as in STEP 3 above. If the result of this determination is positive (if the flow of water to the hot water tap CL has been stopped), the control device 31A requests the control device 31B of the auxiliary hot water heater 2B to stop hot water supply in STEP 12, and further stops the operation of the first heating unit 11 of the main hot water heater 2A in STEP 10 described above.

Furthermore, if the determination result in STEP 7 is negative (water is still flowing to the hot water tap CL), the control device 31A determines in STEP 8 whether the hot water heat quantity has decreased to a heat quantity that is a predetermined amount α lower than the upper limit heat quantity of the main hot water heater 2A (= upper limit heat quantity - α). In this case, the hot water heat quantity is calculated by multiplying the difference between the hot water setting temperature and the water supply temperature by the hot water supply flow rate to the hot water tap CL. Furthermore, the hot water supply flow rate to the hot water tap CL is calculated as the sum of the flow rate detected by the flow rate sensor 17 of the main hot water heater 2A and the flow rate detected by the flow rate sensor 17 of the auxiliary hot water heater 2B. The control device 31A obtains the flow rate detected by the flow rate sensor 17 of the auxiliary hot water heater 2B through communication with the control device 31B.

If the determination result in STEP 8 is negative (the amount of hot water heat > the upper limit of the heat - α), the control device 31A repeats the process from STEP 7. If the determination result in STEP 8 is positive (the amount of hot water heat ≦ the upper limit of the heat - α), the control device 31A requests the control device 31B of the auxiliary hot water heater 2B to stop hot water supply in STEP 9, and then repeats the process from STEP 3 described above. In this case, the process from STEP 3 is repeated with the supply of hot water from the auxiliary hot water heater 2B to the hot water tap CL stopped.

On the other hand, if the judgment result in STEP 5 is positive, i.e., if the hot water heat quantity is greater than the upper limit heat quantity and the auxiliary hot water heater 2B is currently filling the water tank, the control device 31A will not request the control device 31B of the auxiliary hot water heater 2B to start supplying hot water, but will instead control the operation of the water supply adjustment valve 16 of the main hot water heater 2A in STEP 11 to adjust the amount of hot water supplied to the hot water tap CL.

In this case, the control device 31B reduces the amount of hot water supplied to the hot water tap CL so that the condition that the amount of hot water heat supplied is less than or equal to the upper limit amount of heat is satisfied. The control device 31A then repeats the process from STEP 3. This allows hot water to be supplied to the hot water tap CL at the hot water supply setting temperature without providing auxiliary hot water from the auxiliary hot water heater 2B to the hot water tap CL.

In parallel with the processing being carried out in main water heater 2A as described above, in auxiliary water heater 2B, control device 31B executes the control processing shown in the flowchart of Figure 3.
When the hot water supply on-off valve 26 of the auxiliary hot water heater 2B is in the closed state, the control device 31B determines in STEP 21 whether or not the auxiliary hot water heater 2B is in the hot water filling operation, and if the result of this determination is affirmative, the control device 31B keeps the hot water supply on-off valve 26 in the closed state in STEP 26 and repeats the determination process of STEP 21. Therefore, when the auxiliary hot water heater 2B is in the hot water filling operation, auxiliary hot water is not supplied from the auxiliary hot water heater 2B to the hot water tap CL.

If the determination result in STEP 21 is negative (the water filling operation is not in progress), the control device 31B determines in STEP 22 whether or not a request to start hot water supply has been made by the control device 31A of the main hot water heater 2A.If the determination result is negative, the process goes through STEP 26 described above (while the hot water supply on-off valve 26 is kept closed) and repeats the process from STEP 21.

If the determination result in STEP 22 is positive (if there is a request to start hot water supply), this is when the auxiliary hot water heater 2B is not filling the water with hot water and the determination result in STEP 4 is positive (if the hot water supply heat quantity > upper limit heat quantity). In this case, in STEP 23, the control device 31B controls the hot water supply on-off valve 26 to open, and starts the hot water supply operation of the auxiliary hot water heater 2B.

During this hot water operation, the control device 31B controls the temperature of the hot water supplied from the auxiliary water heater 2B to the hot water tap CL by controlling the amount of heat (amount of combustion from the burner) of the first heating unit 11 so that the hot water temperature detected by the temperature sensor 18 of the auxiliary water heater 2B matches or nearly matches the hot water set temperature as its target value. As a result, hot water is supplied from the auxiliary water heater 2B to the hot water tap CL at the hot water set temperature in parallel with hot water supply from the main water heater 2A to the hot water tap CL.

Furthermore, in STEP 24, the control device 31B repeats the process of determining whether a request to stop hot water supply has been received from the control device 31A of the main hot water heater 2A until the determination result becomes affirmative. Then, when the determination result in STEP 24 becomes affirmative (a request to stop hot water supply has been received from the control device 31A), the control device 31B closes the hot water supply on-off valve 26 of the auxiliary hot water heater 2B in STEP 25 and stops operation of the first heating unit 11. This stops auxiliary hot water supply from the auxiliary hot water heater 2B to the hot water tap CL.

In this embodiment, with regard to the supply of hot water to the hot water tap CL, the operation of the main water heater 2A and auxiliary water heater 2B is controlled as described above. When the hot water filling operation of the auxiliary water heater 2B is stopped, if the condition of hot water supply heat quantity > upper limit heat quantity, which is a predetermined condition regarding whether or not hot water is required to be supplied from the auxiliary water heater 2B to the hot water tap CL, is met, in addition to the supply of hot water from the main water heater 2A to the hot water tap CL, auxiliary hot water is supplied from the auxiliary water heater 2B to the hot water tap CL.

In this case, hot water is supplied from the main water heater 2A to the hot water tap CL and from the auxiliary water heater 2B to the hot water tap CL at the set hot water supply temperature, preventing the user from feeling uncomfortable with the hot water supply temperature to the hot water tap CL.

Furthermore, while the auxiliary water heater 2B is performing a hot water filling operation, the hot water on-off valve 26 of the auxiliary water heater 2B is kept closed, and auxiliary hot water is not supplied from the auxiliary water heater 2B to the hot water tap CL, regardless of whether the condition of hot water supply heat quantity > upper limit heat quantity, which is a predetermined condition regarding whether or not hot water is required to be supplied from the auxiliary water heater 2B to the hot water tap CL, is met.

In this case, the main water heater 2A controls the operation of the water supply adjustment valve 16 to reduce the hot water supply flow rate to the hot water tap CL, allowing hot water to be supplied to the hot water tap CL at the hot water supply set temperature. This prevents the user from feeling uncomfortable with the hot water supply temperature to the hot water tap CL. In addition, in this case, the auxiliary water heater 2B can continuously supply hot water (fill the bathtub BTB) at the hot water filling set temperature until the bathtub is completely filled.
Second Embodiment

Next, a second embodiment of the present invention will be described with reference to Figures 4 and 5. Note that this embodiment differs from the first embodiment only in the control processes of the main water heater 2A and auxiliary water heater 2B related to the supply of hot water to the hot water tap CL, and therefore a description of the same aspects as in the first embodiment will be omitted.

The control device 31A of the main hot water heater 2A executes the control process for supplying hot water to the hot water tap CL, starting from STEP 31 shown in the flowchart of FIG. 4. In this case, the processes in STEPs 31 to 40 and 44 are the same as the processes in STEPs 1 to 10 and 12 in the first embodiment.

In this embodiment, when the determination result in STEP 34 is positive (when the condition that the hot water supply heat quantity > the upper limit heat quantity is met), the processing when the determination result in STEP 35 is positive (when the auxiliary hot water heater 2B is performing a hot water filling operation) differs from that in the first embodiment.

Specifically, if the determination result in STEP 35 is positive, the control device 31A determines in STEP 41 whether the set temperature for filling the bathtub BTB matches the set hot water supply temperature. Here, in this embodiment, "the set temperature for filling the bathtub matches the set hot water supply temperature" does not necessarily mean that the set temperature for filling the bathtub exactly matches the set hot water supply temperature, but also includes cases where the set temperature for filling the bath matches the set hot water supply temperature almost exactly. Therefore, in STEP 41, the control device 31A determines whether the set temperature for filling the bath matches the set hot water supply temperature based on whether the absolute value of the difference between the set temperature for filling the bathtub and the set hot water supply temperature is a small value below a predetermined threshold.

If the determination result in STEP 41 is positive (the set temperature for filling the bath water matches (or nearly matches) the set temperature for hot water supply), the control device 31A executes the processing from STEP 36. As a result, in addition to the supply of hot water from the main water heater 2A to the hot water tap CL, auxiliary hot water is supplied from the auxiliary water heater 2B to the hot water tap CL.

Furthermore, if the determination result in STEP 41 is negative (if the absolute value of the difference between the bath filling set temperature and the hot water supply set temperature exceeds a predetermined threshold), the control device 31A determines in STEP 42 whether the bath filling set temperature is higher than the hot water supply set temperature. If the determination result in STEP 42 is positive (if the bath filling set temperature is greater than the hot water supply set temperature), the control device 31A executes the processing from STEP 36, as if the determination result in STEP 41 were positive. As a result, in addition to hot water being supplied from the main water heater 2A to the hot water tap CL, auxiliary hot water is also supplied from the auxiliary water heater 2B to the hot water tap CL.

If the determination result in STEP 42 is negative (the absolute value of the difference between the bath filling set temperature and the hot water supply set temperature exceeds a predetermined threshold and the bath filling set temperature is less than the hot water supply set temperature), the control device 31A adjusts the amount of hot water supplied to the hot water tap CL in STEP 43 by controlling the operation of the water supply adjustment valve 16 of the main water heater 2A without requesting the control device 31B of the auxiliary water heater 2B to start supplying hot water.

In this case, similar to STEP 11 in the first embodiment, the operation of the water supply adjustment valve 16 of the main water heater 2A is controlled to reduce the amount of hot water supplied to the hot water tap CL. The control device 31A then repeats the process from STEP 33. This allows hot water to be supplied to the hot water tap CL at the hot water supply setting temperature without providing auxiliary hot water from the auxiliary water heater 2B to the hot water tap CL.

In parallel with the processing being carried out in main water heater 2A as described above, in auxiliary water heater 2B, control device 31B executes the control processing shown in the flowchart of Figure 5.
When the hot water supply on-off valve 26 of the auxiliary water heater 2B is in the closed state, the control device 31B determines in STEP 51 whether the auxiliary water heater 2B is currently performing a hot water filling operation, and if the result of this determination is positive (the hot water filling operation is currently being performed), it further determines in STEP 58 whether there has been a request from the control device 31A of the main water heater 2A to start hot water supply.

If the determination result in STEP 58 is negative (if there is no request to start hot water supply), the control device 31A keeps the hot water supply on-off valve 26 closed in STEP 59 and repeats the process from STEP 51. If the determination result in STEP 58 is positive (if a request to start hot water supply has been received), the control device 31A changes the bath fill temperature setting, which is the target hot water supply temperature for hot water supply (filling) to the bathtub BTB, to the hot water supply setting temperature in STEP 60, and then executes the process from STEP 53 described below.

If the determination result in STEP 51 is negative (water filling operation is stopped), the control device 31A determines in STEP 52 whether or not there has been a request from the control device 31A of the main water heater 2A to start supplying hot water.If the determination result is negative (there has been no request to start supplying hot water), the process goes through STEP 59 described above (while the hot water supply on-off valve 26 is kept closed) and repeats the process from STEP 51.

The determination result in STEP 52 is positive (when there is a request to start hot water supply) when the auxiliary water heater 2B is not filling the water and the determination result in STEP 34 is positive (when the amount of hot water heat supplied is greater than the upper limit of the amount of heat). Furthermore, the processing in STEP 60 is executed when the auxiliary water heater 2B is filling the water and the determination result in STEP 34 is positive (when the amount of hot water heat supplied is greater than the upper limit of the amount of heat), and when the determination result in STEP 41 or 42 is positive (when the set temperature for filling the water matches (or nearly matches) the set temperature for hot water supply, or when the set temperature for filling the water is higher than the set temperature for hot water supply).

In these cases, in STEP 53, the control device 31A controls the hot water supply on/off valve 26 to open and starts hot water supply operation of the auxiliary hot water heater 2B. During this hot water supply operation, the control device 31B controls the amount of heat (amount of combustion in the burner) of the first heating section 11 so that the hot water temperature detected by the temperature sensor 18 of the auxiliary hot water heater 2B matches or nearly matches the hot water supply set temperature as its target value, thereby controlling the temperature of the hot water water supplied from the auxiliary hot water heater 2B to the hot water tap CL. As a result, hot water is supplied from the auxiliary hot water heater 2B to the hot water tap CL at the hot water supply set temperature in parallel with hot water supply from the main hot water heater 2A to the hot water tap CL.

Here, when the auxiliary water heater 2B performs hot water supply operation after processing in STEP 60, the bathtub filling operation (filling the bathtub BTB) is also performed in parallel. In this case, hot water temperature-controlled to the same temperature (= hot water supply set temperature) as the hot water supply temperature from the auxiliary water heater 2B to the hot water tap CL is supplied to the bathtub BTB (filling the bathtub). Therefore, if the judgment result in STEP 41 is positive, the bathtub BTB is filled at a temperature that matches (including a temperature that is almost the same as) the original bath filling set temperature (the temperature set by the user using the kitchen remote control 32A or bathroom remote control 33B). If the judgment result in STEP 42 is positive, the bathtub is filled at a temperature lower than the original bath filling set temperature.

Furthermore, in STEP 54, the control device 31B repeats the process of determining whether a request to stop hot water supply has been received from the control device 31A of the main hot water heater 2A until the determination result becomes positive. Then, when the determination result in STEP 54 becomes positive (a request to stop hot water supply has been received from the control device 31A), the control device 31B controls the hot water supply on-off valve 26 of the auxiliary hot water heater 2B to close in STEP 55. This stops auxiliary hot water supply from the auxiliary hot water heater 2B to the hot water tap CL.

Furthermore, in STEP 56, the control device 31B determines whether the auxiliary water heater 2B is currently performing a water filling operation, and if the determination result is negative (water filling operation is stopped), in STEP 57, the control device 31B stops operation of the first heating unit 11.

Also, if the determination result in STEP 56 is positive (if the bath filling operation is in progress), the control device 31B returns the bath filling set temperature to the original temperature (the temperature set by the user using the kitchen remote control 32A or bathroom remote control 33B) in STEP 61, and then executes the processing from STEP 51 described above. In this case, hot water is supplied (filled) to the bathtub BTB at the original bath filling set temperature.

In this embodiment, with regard to the supply of hot water to the hot water tap CL, the operation of the main water heater 2A and auxiliary water heater 2B is controlled as described above. When the hot water filling operation of the auxiliary water heater 2B is stopped, if the condition of hot water supply heat quantity > upper limit heat quantity, which is a predetermined condition regarding whether or not hot water is required to be supplied from the auxiliary water heater 2B to the hot water tap CL, is met, in addition to the supply of hot water from the main water heater 2A to the hot water tap CL, auxiliary hot water is supplied from the auxiliary water heater 2B to the hot water tap CL.

In this case, hot water is supplied from the main water heater 2A to the hot water tap CL and from the auxiliary water heater 2B to the hot water tap CL at the set hot water supply temperature, preventing the user from feeling uncomfortable with the hot water supply temperature to the hot water tap CL.

In addition, while the auxiliary water heater 2B is performing the hot water filling operation, unless the judgment result in STEP 41 or 42 is affirmative, the hot water on-off valve 26 of the auxiliary water heater 2B is kept closed, and auxiliary hot water is not supplied from the auxiliary water heater 2B to the hot water tap CL, regardless of whether the condition of hot water supply heat quantity > upper limit heat quantity, which is a predetermined condition regarding whether hot water is required to be supplied from the auxiliary water heater 2B to the hot water tap CL, is met.

In this case, the main water heater 2A controls the operation of the water supply adjustment valve 16 to reduce the hot water supply flow rate to the hot water tap CL, allowing hot water to be supplied to the hot water tap CL at the hot water supply set temperature. This prevents the user from feeling uncomfortable with the hot water supply temperature to the hot water tap CL. Also, in this case, the auxiliary water heater 2B can continuously supply hot water (fill the bathtub BTB) at the hot water filling set temperature until filling is complete.

Furthermore, even if the auxiliary water heater 2B is performing a hot water filling operation, if the judgment result in STEP 41 or 42 is affirmative and the condition that the hot water supply heat quantity > upper limit heat quantity is met, in addition to the hot water supply from the main water heater 2A to the hot water tap CL, auxiliary hot water supply from the auxiliary water heater 2B to the hot water tap CL will be performed, just as when the hot water filling operation is stopped. Therefore, the processing of STEP 43 can reduce situations in which the hot water supply flow rate to the hot water tap CL is reduced. Ultimately, this can increase the convenience of the hot water supply flow rate to the hot water tap CL.

In addition, in this case, hot water is supplied from the main water heater 2A to the hot water tap CL and from the auxiliary water heater 2B to the hot water tap CL at the hot water supply set temperature, preventing the user from feeling uncomfortable with the hot water supply temperature to the hot water tap CL.

Furthermore, in this case, if the judgment result in STEP 41 is affirmative (if the bath filling set temperature matches the hot water supply set temperature), the bathtub BTB can be filled with water at a temperature that matches (including a temperature that is nearly the same as) the original bath filling set temperature (the temperature set by the user using the kitchen remote control 32A or bathroom remote control 33B).

Furthermore, if the judgment result in STEP 42 is positive (the bath filling set temperature is greater than the hot water supply set temperature), the bathtub BTB will be filled with water at a temperature lower than the original bath filling set temperature, but the bathwater can be heated to the bath filling set temperature by the reheating process after filling the bath.

Other Embodiments
The present invention is not limited to the above-described embodiment, and other embodiments may be adopted. Some other embodiments are exemplified below.
In the first and second embodiments, the hot water supply system 1 is exemplified as one in which a bathtub is not connected to the main hot water heater 2A, but a bathtub may also be connected to the main hot water heater 2A. Even in this case, when supplying hot water to the hot water tap CL while the main hot water heater 2A is not filling the water with hot water, the operation of the main hot water heater 2A and the auxiliary hot water heater 2B can be controlled in the same manner as in the first or second embodiment, thereby achieving the same effect as in the first or second embodiment.

In addition, in the second embodiment, one of the processes in steps 41 and 42 may be omitted. For example, if the process in step 41 is omitted, a determination may be made in step 42 as to whether the hot water filling set temperature is equal to or greater than the hot water supply installation temperature, and if the determination result is positive (including when the hot water filling set temperature = hot water supply set temperature), hot water supply operation may be performed by the auxiliary hot water heater 2B, and if the determination result is negative (when the hot water filling set temperature < hot water supply set temperature), hot water supply operation may not be performed by the auxiliary hot water heater 2B (the process in step 43 may be performed).

Furthermore, if the judgment result in STEP 41 is positive (if the bath filling set temperature matches (or nearly matches) the hot water supply set temperature), the hot water supply to the hot water tap CL and the hot water supply (filling) to the bathtub BTB may be performed using the bath filling set temperature that matches (or nearly matches) the hot water supply set temperature as the target hot water supply temperature.

In addition, in the first embodiment, while the auxiliary water heater 2B is performing a hot water filling operation, the control device 31B of the auxiliary water heater 2B is not requested to start supplying hot water even in a situation where the hot water heat quantity exceeds the upper limit heat quantity.In the second embodiment, when the auxiliary water heater 2B is performing a hot water filling operation and the judgment results of STEPs 41 and 42 are negative, the control device 31A of the main water heater 2A is not requested to start supplying hot water from the control device 31B of the auxiliary water heater 2B, even in a situation where the hot water heat quantity exceeds the upper limit heat quantity.However, in these situations, while the control device 31A of the main water heater 2A requests the control device 31B of the auxiliary water heater 2B to start supplying hot water, the auxiliary water heater 2B may ignore the request (keep the hot water supply on-off valve 26 closed even if the request is received).

Furthermore, in the first and second embodiments described above, examples have been given in which the first hot water supply target portion and the second hot water supply target portion of the present invention are the hot water tap CL and the bathtub BTB, respectively. However, the first hot water supply target portion and the second hot water supply target portion of the present invention may be different from those described above. For example, the second hot water supply target portion may be a hot water tap other than the hot water tap CL, or a dishwasher, etc.

In addition, in the first and second embodiments, the control devices of the present invention correspond to the control devices 31A and 31B, but for example, a control device that integrates these may be provided in the hot water supply system 1. Also, for example, a higher-level control device than the control devices 31A and 31B may be provided, and this higher-level control device may execute part of the processing of the control devices 31A and 31B described above.

Furthermore, while the first and second embodiments illustrate a hot water supply system 1 equipped with only two water heaters 2A and 2B, the present invention can also be applied to a hot water supply system equipped with three or more water heaters. For example, the same control processing as in the first and second embodiments can be used to control the operation of two of the three or more water heaters.

1...hot water supply system, 2A...main water heater (first water heater), 2B...auxiliary water heater (second water heater), 10...water supply line, 11...first heating section (heating section), 12...hot water supply line, 16...water supply amount adjustment valve (flow rate adjustment valve), 26...hot water on/off valve (on/off valve), 31A, 31B...control device, CL...hot water tap (first hot water supply target part), BTB...bathtub (second hot water supply target part).

Claims (4)

a first water heater and a second water heater, each having a water supply passage, a hot water supply passage, and a heating unit, and each configured to heat hot water supplied via the water supply passage in the heating unit and to dispense the heated hot water via the hot water supply passage; and a control device that controls the operation of the first water heater and the second water heater, wherein the hot water supply passage of the first water heater is connected to a first hot water supply target portion so as to supply the hot water to the first hot water supply target portion, and the hot water supply passage of the second water heater is connected to the first hot water supply target portion and the second hot water supply target portion so as to distribute the hot water to the first hot water supply target portion, and further wherein an on-off valve is attached to a flow passage that distributes the hot water from the hot water supply passage of the second water heater to the first hot water supply target portion,
a flow rate regulating valve capable of regulating the flow rate of hot water supply water flowing from the first hot water heater to the first hot water supply target part;
When a target temperature of the hot water supply water for the first hot water supply target part is defined as a first target hot water supply temperature, a hot water supply heat quantity required to raise the temperature of the hot water supply water supplied to the first hot water supply target part to the first target hot water supply temperature, and an upper limit value of the heat quantity that can be input to the hot water supply water from the heating part of the first hot water heater is defined as an upper limit heat quantity, and a predetermined condition is met when a determination result of whether the hot water supply heat quantity is greater than the upper limit heat quantity is affirmative,
The control device has a function of executing a first control process to control the operation of the first water heater and the flow rate adjustment valve so that hot water at the first target hot water supply temperature is supplied from the first water heater to the first hot water supply target portion when the predetermined condition is met while hot water supply from the second water heater to the second hot water supply target portion is stopped, and to control the operation of the on-off valve and the second water heater so that hot water at the first target hot water supply temperature is supplied from the second water heater to the first hot water supply target portion while the on-off valve is open;
A hot water supply system characterized in that, when hot water is supplied to the first hot water supply target portion while controlling the operation of the second hot water heater to supply hot water from the second hot water supply target portion, the system is configured to have the function of executing a second control process that controls the operation of the on-off valve and the second water heater so that hot water at a second target hot water supply temperature, which is the target temperature of the hot water for the second hot water supply target portion, is supplied from the second hot water heater to the second hot water supply target portion, regardless of whether the specified condition is met, and controls the operation of the first water heater and the flow rate control valve so that hot water at the first target hot water supply temperature is supplied from the first water heater to the first hot water supply target portion. 2. The hot water supply system according to claim 1,
The control device is configured to execute the second control process when supplying hot water to the first hot water supply target area while controlling the operation of the second water heater so that the second water heater supplies hot water to the second hot water supply target area, if the second target hot water supply temperature does not match the first target hot water supply temperature, and when the second target hot water supply temperature matches the first target hot water supply temperature, to control the operation of the on-off valve and the second water heater so that the second water heater supplies hot water at the first target hot water supply temperature or the second target hot water supply temperature to the first hot water supply target area and the second hot water supply target area, while keeping the on-off valve open, and to execute a third control process to control the operation of the first water heater and the flow rate control valve so that the first water heater supplies hot water at the first target hot water supply temperature or the second target hot water supply temperature to the first hot water supply target area. a first water heater and a second water heater, each having a water supply passage, a hot water supply passage, and a heating unit, and each configured to heat hot water supplied via the water supply passage in the heating unit and to dispense the heated hot water via the hot water supply passage; and a control device that controls the operation of the first water heater and the second water heater, wherein the hot water supply passage of the first water heater is connected to a first hot water supply target portion so as to supply the hot water to the first hot water supply target portion, and the hot water supply passage of the second water heater is connected to the first hot water supply target portion and the second hot water supply target portion so as to distribute the hot water to the first hot water supply target portion, and further wherein an on-off valve is attached to a flow passage that distributes the hot water from the hot water supply passage of the second water heater to the first hot water supply target portion,
a flow rate regulating valve capable of regulating the flow rate of hot water supply water flowing from the first hot water heater to the first hot water supply target part;
The control device has a function of executing a first control process to control the operation of the first water heater and the flow rate adjustment valve so that hot water at a first target hot water temperature, which is a target temperature for the hot water for the first hot water supply target portion, is supplied from the first water heater to the first hot water supply target portion when a predetermined condition regarding the need for hot water supply from the second water heater to the first hot water supply target portion is met while hot water supply from the second water heater to the second hot water supply target portion is stopped and the operation of the on-off valve and the second water heater so that hot water at the first target hot water temperature is supplied from the second water heater to the first hot water supply target portion while the on-off valve is open;
When hot water is supplied to the first hot water supply target portion while controlling the operation of the second hot water heater to supply hot water from the second hot water heater to the second hot water supply target portion, the control unit is configured to have a function of executing a second control process that controls the operation of the on-off valve and the second hot water heater so that hot water of a second target hot water supply temperature, which is a target temperature of the hot water for the second hot water supply target portion, is supplied from the second hot water heater to the second hot water supply target portion, regardless of whether the predetermined condition is met, and controls the operation of the first hot water heater and the flow rate adjustment valve so that hot water of the first target hot water supply temperature is supplied from the first hot water heater to the first hot water supply target portion,
the first hot water supply target portion is a hot water tap, and the second hot water supply target portion is a bathtub,
The control device is configured to execute the second control process when supplying hot water to the first hot water supply target portion while controlling the operation of the second water heater so that the second water heater supplies hot water to the second hot water supply target portion, if the second target hot water supply temperature is lower than the first target hot water supply temperature or is a temperature below the first target hot water supply temperature, and if the second target hot water supply temperature is a temperature above the first target hot water supply temperature or is higher than the first target hot water supply temperature, to control the operation of the on-off valve and the second water heater so that the second water heater supplies hot water at the first target hot water supply temperature to the first hot water supply target portion and the second hot water supply target portion, while keeping the on-off valve open, and to execute a fourth control process to control the operation of the first water heater and the flow rate control valve so that the first water heater supplies hot water at the first target hot water supply temperature to the first hot water supply target portion. 4. The hot water supply system according to claim 3,
The control device is configured to execute a third control process in which, when a request for hot water supply to the first hot water supply target portion occurs while controlling the operation of the second water heater so that the second water heater supplies hot water to the second hot water supply target portion, and when the second target hot water supply temperature matches the first target hot water supply temperature, the control device controls the operation of the on-off valve and the second water heater so that the second water heater supplies hot water at the first target hot water supply temperature or the second target hot water supply temperature to the first hot water supply target portion and the second hot water supply target portion, while opening the on-off valve, and controls the operation of the first water heater and the flow rate control valve so that the first water heater supplies hot water at the first target hot water supply temperature or the second target hot water supply temperature to the first hot water supply target portion.