JP7378737B2 - hot water system - Google Patents

Description

The present disclosure relates to a hot water supply system.

Patent Document 1 discloses a water heater that automatically fills hot water. When starting to fill hot water, this water heater determines whether there is any remaining hot water in the bathtub, and if there is no remaining hot water, it drops the set amount of hot water into the bathtub, and if there is remaining hot water, it drops the set amount of hot water into the bathtub. The insufficient amount of hot water is poured into the bathtub. The amount of hot water that is insufficient is calculated as follows. When performing a trial run to fill the bathtub with hot water, this water heater memorizes the reference water level when the minimum set amount of hot water is poured in, and also calculates the rise in water level when 60L of hot water is poured from the minimum set water level. , set the relational expression between the amount of hot water in the bathtub and the water level. When this hot water heater actually fills the bathtub with hot water, if there is any remaining hot water in the bathtub, the above relational expression is compared with the detected value of the water level sensor to determine the amount of hot water that is insufficient to reach the set amount of hot water.

Japanese Patent Application Publication No. 2010-91169

By the way, there are various shapes of bathtubs, and it is required to calculate the amount of shortage taking into account the differences in the shapes of bathtubs.

Therefore, the present disclosure provides a technique that can calculate the amount of shortage by taking into consideration the difference in the shape of the bathtub.

A hot water supply system according to one aspect of the present disclosure includes a water pipe for passing water introduced from the outside, a burner for burning combustion gas to generate exhaust gas, and a burner provided in the middle of the water pipe. a heat exchanger that transfers the heat of the exhaust gas to the water passing through the interior; a communication pipe that guides the water heated by the heat exchanger to the bathtub through the water pipe; A dropping control unit that performs dropping control to supply a set value of water into the bathtub, a water level detecting unit that detects the water level in the bathtub, and a detection result of the water level detecting unit when water is dropped into the bathtub. a calculation unit that calculates the area value of each of a plurality of water level regions having different height levels based on the above-mentioned water level, and the drop-in control unit calculates the area value of each of the plurality of water level regions having different height levels; When the drop control start condition is satisfied, at least one of the area values is selected from among the area values based on the level of the remaining water in the bathtub, and the selected area value and the remaining water are and a shortage amount calculation unit that calculates a shortage amount with respect to the set value based on the water level and the set value.

The hot water supply system according to one aspect of the present disclosure can calculate the shortage amount by taking into account the difference in the shape of the bathtub.

FIG. 1 is a schematic circuit diagram illustrating a hot water supply system according to a first embodiment. FIG. 2 is a block diagram schematically illustrating a controller and a remote controller that constitute the hot water supply system according to the first embodiment. FIG. 3(A) is a schematic cross-sectional view illustrating a bathtub with a general shape. FIG. 3(B) is a schematic cross-sectional view illustrating a bathtub with a special shape. FIG. 4 is a flowchart illustrating the first half of the area value setting process performed in the hot water supply system of the first embodiment. FIG. 5 is a flowchart illustrating the second half of the flow of the area value setting process performed in the hot water supply system of the first embodiment. FIG. 6(A) is a schematic cross-sectional view illustrating a generally shaped bathtub into which a set amount of hot water is poured. FIG. 6(B) is a schematic cross-sectional view illustrating a specially shaped bathtub into which a set amount of hot water is poured. FIG. 7 is an explanatory diagram illustrating various data stored in the memory. FIG. 8 is a flowchart illustrating the flow of automatic hot water filling control performed in the hot water supply system of the first embodiment.

The following description relates to an example embodiment of a hot water supply system. Note that the features [1] to [3] shown below may be combined in any manner consistent with each other.

[1] A water pipe for passing water introduced from the outside, a burner for burning combustion gas to produce exhaust gas, and a burner installed in the middle of the water pipe to prevent water from passing through the water pipe. a heat exchanger that transfers heat of exhaust gas; a communication pipe that leads the water heated by the heat exchanger to the bathtub through the water pipe; and a set value of water that is introduced into the bathtub through the communication pipe. A dropping control unit that performs dropping control to supply water, a water level detecting unit that detects the water level in the bathtub, and a water level detecting unit that has different height levels based on the detection result of the water level detecting unit when water is dropped into the bathtub. a calculation unit that calculates the area value of each of the plurality of water level regions, and the drop-in control unit is configured to determine that the start condition for the drop-in control is satisfied when the relationship between the plurality of area values does not satisfy a normal condition. In this case, at least one area value is selected from among the area values based on the level of residual water in the bathtub, and the selected area value, the level of residual water, and the set value are selected. A hot water supply system comprising: a shortage amount calculation unit that calculates a shortage amount with respect to the set value based on the set value.

The hot water system of [1] above uses an area value selected based on the water level of the remaining water in the bathtub from among the area values of each of a plurality of water level areas with different height levels, the water level of the remaining water, and a set value. Based on this, it is possible to calculate the amount of shortage that is short of the set value. Therefore, according to this hot water supply system, it is possible to more accurately calculate the amount of shortage in a bathtub whose area value varies depending on the water level region.

Note that "the height levels are different" may mean that at least either the upper limit water level or the lower limit water level is different. For example, when comparing one water level area with another water level area, if at least either the upper limit water level or the lower limit water level is different, those water level areas are considered to be "multiple water levels with different height levels." area”.

[2] The calculation unit has a plurality of rising water level calculation methods defined for each water level area, in which a lower limit water level determining condition and an upper limit water level determining condition are defined, and when water is dropped into the bathtub, each of the rising water level calculations is performed. The hot water supply system according to [1], wherein each of the area values for each water level region corresponding to each of the rising water level calculation methods is calculated based on each rising water level calculated by each method.

According to the hot water supply system of [2] above, by calculating each area value for each water level area according to the rising water level calculation method, each area value for each water level area can be easily calculated.

[3] The plurality of water level regions include a first water level from a state in which water is poured into the empty bathtub to a first proportion of the set value to a second proportion greater than the first proportion; a second water level region from a state in which water is dropped to a third ratio larger than the first ratio to the empty bathtub until water is dropped to the set value; A third water level region is determined from a state in which water has dropped to the first ratio of the set value to a state in which water has been dropped to the set value, and the calculation unit is based on the amount of water dropped into the first water level region. to calculate a first area value corresponding to the first water level area, calculate a second area value corresponding to the second water level area based on the amount of water dropped into the second water level area, and calculate the second area value corresponding to the second water level area based on the amount of water dropped into the second water level area. A third area value corresponding to the third water level area is calculated based on the amount of water dropped into the area, and the dropping control unit calculates the starting condition when the relationship between the plurality of area values does not satisfy the normal condition. is established, if the water level of the residual water in the bathtub is less than the threshold value, select the third area value, and if the water level of the residual water in the bathtub is equal to or higher than the threshold value, select the third area value. The hot water supply system according to [1] or [2], in which the second area value is selected.

The hot water supply system in [3] above selects the third area value that corresponds to the wide third water level region when the water level of the remaining water in the bathtub is less than the threshold and the shortage is widespread. , if "the shortage is limited to a relatively upper part of the bathtub", the second area value corresponding to the second water level area is selected. Therefore, according to this hot water supply system, even if the water level of the remaining water in the bathtub is limited to a relatively upper part in a bathtub with a shape where the area value differs depending on the water level area, the amount of insufficient water can be determined more accurately. can be calculated.

[4] The water heating system according to [3], wherein the dropping control unit determines that the normal condition is not satisfied when the ratio of the first area value to the second area value is not within a predetermined normal range. .

According to the hot water supply system of [4] above, it is possible to more accurately calculate the amount of shortage even for a bathtub whose shape is such that the first area value and the second area value are significantly different.

[5] The hot water system according to [3] or [4], wherein the third ratio is the same as the second ratio.

According to the hot water system in [5] above, there is no need to store the third ratio separately from the second ratio, and information related to the third ratio (for example, when an empty bathtub is filled with water up to the third ratio), there is no need to store the third ratio separately from the second ratio. Since there is no need to manage the water level (such as the water level when water is dropped), it is possible to suppress the increase in storage space.

<First embodiment>
The following description relates to the first embodiment.
(Basic configuration)
A hot water supply system 1 shown in FIG. 1 is configured as a bath and hot water supply system having a function of supplying hot water to a bathtub 60 and a function of heating water in the bathtub, and mainly includes a hot water supply side circuit 2 and a bath side circuit 3. The hot water supply side circuit 2 includes a water inlet pipe 12, a hot water outlet pipe 10, a gas burner 4 (burner), a hot water supply side heat exchanger 6 (heat exchanger), etc., and functions as a path for heating tap water supplied from the outside and discharging the hot water. do. The bath side circuit 3 includes a gas burner 54 (bath side burner), a bath side heat exchanger 56, piping 66, a circulation pump 62, a water level sensor 63, thermistors 64, 65, etc., and is used for circulating heating during automatic hot water filling, bath It is used for cooking etc.

In the hot water supply side circuit 2, a pipe line constituted by the water inlet pipe 12, the heat transfer tube 8a, the piping 20, the heat transfer tube 7a, and the hot water outlet pipe 10 functions as a hot water supply side water passage. The water inlet pipe 12 is configured as a path through which water flows from the water inlet 16, and the hot water outlet pipe 10 is configured as a path through which hot water is sent to the hot water outlet 18. The gas burner 4 corresponds to an example of a burner, and is a part that burns combustion gas to generate combustion exhaust gas. The hot water supply side heat exchanger 6 corresponds to an example of a heat exchanger, and allows water to pass through a hot water supply side water passage (a pipe line constituted by the water inlet pipe 12, the heat transfer pipe 8a, the pipe 20, the heat transfer pipe 7a, and the hot water outlet pipe 10). It is a part that transfers the heat generated by the gas burner 4 to boil water, and is installed in the middle of the hot water supply side water passage, and is a part that boils water by transferring the heat generated by the gas burner 4 to the water passing inside the hot water supply side water passage. It functions to conduct heat. The hot water supply side heat exchanger 6 includes a primary heat exchanger 7 and a secondary heat exchanger 8. The primary heat exchanger 7 is arranged in the hot water supply combustion chamber 90 on the upstream side of the combustion exhaust path of the gas burner 4, and the secondary heat exchanger 8 is arranged in the hot water supply combustion chamber 90 on the downstream side of the combustion exhaust path. There is.

In the hot water supply side circuit 2, a water inlet pipe 12 is connected to the inlet of the secondary heat exchanger 8 in a configuration that supplies tap water. The water inlet pipe 12 includes a thermistor 25 as a water temperature detection unit that detects the temperature of the water passing through the water inlet pipe 12 (that is, the temperature of the water at a position upstream of the heat exchanger in the water pipe), and a A water amount sensor 34 is provided as a water amount detection section that detects the amount of water (that is, the amount of water flowing through the water pipe). A heat exchanger tube 8a of the secondary heat exchanger 8 is connected to the downstream side of the water inlet pipe 12, and further downstream thereof, a heat exchanger tube 8a of the secondary heat exchanger 8 and a heat exchanger tube 7a of the primary heat exchanger 7 are connected. A pipe 20 connecting the two is connected. A heat exchanger tube 7a of the primary heat exchanger 7 is connected to this piping 20, and a hot water outlet pipe 10 is connected to the outlet of the primary heat exchanger 7, and a hot water outlet pipe 10 is connected to the outlet of the primary heat exchanger 7. is connected. The hot water tap pipe 10 is provided with a thermistor 26 that detects the temperature of water within the hot water tap pipe 10. In this configuration, the water inlet pipe 12, the heat transfer pipe 8a, the pipe 20, the heat transfer pipe 7a, and the hot water outlet pipe 10 correspond to an example of water pipes, and pass water introduced from a water supply (not shown) provided outside the hot water supply system 1. Functions as a flow path.

The hot water supply side heat exchanger 6 functions so that the primary heat exchanger 7 recovers sensible heat of the combustion exhaust gas, and then the secondary heat exchanger 8 recovers latent heat. Specifically, the primary heat exchanger 7 includes a heat exchanger tube 7a that serves as a water flow path in the primary heat exchanger 7, and the combustion exhaust gas generated by the gas burner 4 is connected to the water passing through the heat exchanger tube 7a. Heat is exchanged by transferring the combustion heat contained therein and transferring sensible heat energy to water. In addition, the secondary heat exchanger 8 is provided with a heat transfer tube 8a that serves as a water flow path in the secondary heat exchanger 8, and the combustion exhaust generated in the gas burner 4 is transferred to the The combustion heat after passing through the heat exchanger 7 is transferred, and the heat is exchanged so that the thermal energy of latent heat is transferred to the water.

A bypass path 14 configured as a water path different from that of the hot water supply side heat exchanger 6 is provided as a water path that bypasses between the water inlet pipe 12 and the hot water outlet pipe 10. The bypass path 14 has a configuration (for example, a configuration that can change steplessly) that can change the bypass path 14 from a closed state in which water flow is blocked to an open state (a state in which the degree of opening is increased compared to the closed state). A bypass valve 32 is provided. In the water inlet pipe 12, a water flow rate control valve 33 is provided upstream of the branch position where the bypass path 14 connects. The water flow control valve 33 includes a motor that controls the rotation angle of the drive shaft in response to instructions from the controller 22, and continuously changes the opening of the water inlet pipe 12 to various degrees between a closed state and a fully open state. It is configured so that it can be done. In this configuration, the water flow control valve 33 functions to adjust the amount of water flowing through the water pipe.

The gas pipe 40 that supplies gas to the gas burner 4 includes, from the upstream side, a gas source solenoid valve 42, a hot water supply gas proportional control valve 44, and hot water supply switching solenoid valves 46, 46 for each branch pipe to each gas burner 4. Each is provided. Further, a fan 48 is provided below the hot water supply combustion chamber 90 to supply combustion air to each gas burner 4 (burner) and the gas burner 54 (bath side burner). A switching solenoid valve 53 is provided in a branch pipe from the gas pipe connected to the gas burner 54 (bath side burner). The hot water supply gas proportional control valve 44 and the hot water supply switching solenoid valve 46 function to adjust the amount of gas supplied to the gas burner 4 .

In the bath-side circuit 3, the pipe 66 includes a return pipe 67 for guiding water from the bath-side heat exchanger 56 side to the bath-side heat exchanger 56 side, and a return pipe 67 for guiding water from the bath-side heat exchanger 56 side to the bath-side heat exchanger 56 side. It includes an outgoing pipe 68 for guiding the bath, and a pipe 69 in the bath side heat exchanger 56 that is connected to the return pipe 67 and the outgoing pipe 68. The bath side heat exchanger 56 includes a bath primary heat exchanger 57 and a bath secondary heat exchanger 58, and functions to transfer heat generated by the gas burner 54 (bath side burner) to the water passing through the piping 66. .

The return piping 67 is arranged between the bathtub 60 and the bath secondary heat exchanger 58, and the return piping 67 includes a circulation pump 62, a water level sensor 63, and a temperature of the water passing through the return piping 67. That is, a thermistor 64 (bath thermistor) that detects the water temperature in the bathtub 60 is provided. The circulation pump 62 is a device that causes water in the piping 66 to flow. The water level sensor 63 corresponds to an example of a water level detection section, and functions to detect the water level in the bathtub 31 based on water pressure.

The outgoing pipe 68 is arranged between the bath primary heat exchanger 57 and the bathtub 60. A dropping pipe 70 branched from the outlet pipe 10 is connected to the outgoing pipe 68, and the dropping pipe 70 is provided with a hot water supply electromagnetic valve 72 and a dropping water amount sensor 74. Then, by opening the hot water supply electromagnetic valve 72 provided in the drop pipe 70, hot water heated by the hot water supply side circuit 2 can be supplied to the bathtub 60. The drop-in water amount sensor 74 has a function of detecting the amount of water supplied to the bathtub 60 via the drop-in pipe 70. The drop pipe 70 serves as a path for passing hot water from the hot water supply side passageway of the hot water supply side circuit 2 to the piping 66 (circulation path) of the bath side circuit 3. Specifically, the drop pipe 70 and the pipe 66 correspond to an example of a communication pipe, and are branched from a water pipe (specifically, the hot water outlet pipe 10), communicate with the bathtub 60, and pass through the water pipe to the hot water supply side. It functions to guide the water heated by the heat exchanger 6 to the bathtub 60.

The hot water supply system 1 is provided with a controller 22 shown in FIGS. 1 and 2. The controller 22 shown in FIG. 2 includes a control unit 22A configured as, for example, a known microcomputer, a memory 22B configured as a known semiconductor memory (for example, non-volatile memory such as EEPROM), and communication with the outside. The communication unit 22C is configured as an interface for performing the following. The controller 22 is configured to be able to acquire signals from various sensors provided in the hot water supply side circuit 2 and the bath side circuit 3, and can control various actuators provided in the hot water supply side circuit 2 and the bath side circuit 3. .

As shown in FIG. 2, a plurality of remote controllers 80 are arranged in a configuration that allows them to communicate with the controller 22. In the example of FIGS. 1 and 2, the plurality of remote controllers 80 include a first remote controller 81 provided in a bathroom and a second remote controller 82 provided in a location other than the bathroom (for example, the kitchen). .

As shown in FIG. 2, the first remote controller 81 includes a control section 81A configured as a known microcomputer or the like, a display section 81B configured as a liquid crystal display device, etc., and a plurality of known switches such as push buttons. A communication unit 81D that communicates with the controller 22 and the second remote controller 82, and an audio output unit 81E that includes a speaker that outputs audio. The operation unit 81C is composed of a plurality of operation units, and is used for input operations to instruct automatic filling of the bathtub 60, input operations to reserve automatic hot water filling, input operations to switch on/off states of the above-mentioned additional functions, etc. used.

The second remote controller 82 is similar, and includes a control section 82A configured as a known microcomputer or the like, a display section 82B configured as a liquid crystal display device, etc., and a plurality of known switches such as push buttons. It includes an operation section 82C, a communication section 82D for transmitting signals generated by the second remote controller 82 to the controller 22, and an audio output section 82E including a speaker for outputting audio. The second remote controller 82 has the same or simplified configuration as the first remote controller 81, and can be set in the same way as the first remote controller 81. The on/off states of both remote controllers 80 are linked together. In both remote controllers 80, the contents set on one are reflected on each other.

The controller 22 described above corresponds to an example of a drop-in control section, a calculation section, and a shortage amount calculation section. The controller 22 can perform drop-in control to supply a set amount of hot water into the bathtub 60 via the drop-in pipe 70 (communication pipe). The set amount of hot water corresponds to an example of a set value. The set amount of hot water is set to, for example, an initial value (eg, 160 L), and the user can set an arbitrary value using the remote controller 80, for example. The controller 22 can calculate the area value of each of the plurality of water level regions based on the detection result of the water level sensor 63 when water is poured into the bathtub 60. More specifically, the controller 22 has a plurality of rising water level calculation methods defined for each water level region, in which a lower limit water level determination condition and an upper limit water level determining condition are defined, and when water is poured into the bathtub 60, each rising water level calculation method is determined. Based on each rising water level calculated by each calculation method, each area value for each water level region corresponding to each rising water level calculation method can be calculated. The controller 22 can store each calculated area value. In the case where the relationship between the plurality of area values does not satisfy the normal condition, the controller 22 selects one of the area values from among the area values based on the water level of the remaining water in the bathtub 60 when the start condition for the dropping control is satisfied. At least one area value may be selected. The controller 22 can calculate the insufficient amount of hot water relative to the set amount of hot water based on the selected area value, the water level of the remaining water, and the set amount of hot water.

In this embodiment, a first water level region, a second water level region, and a third water level region are defined as the plurality of water level regions. The first water level region is a region from when the controller 22 fills the empty bathtub 60 with water to a first proportion of the set amount of hot water to when the controller 22 fills the empty bathtub 60 with water to a second proportion, which is larger than the first proportion. The controller 22 can detect the amount of water supplied to the bathtub 60 based on the signal from the amount of water dropped into the bathtub 60, and can calculate the amount of water poured into the bathtub 60 by integrating the detected amount of supplied water. can. Thereby, the controller 22 can grasp how much water has fallen into the bathtub 60. The lower limit water level determination condition corresponding to the first water level region is, for example, the water level detected by the water level sensor 63 when the empty bathtub 60 is filled with water up to a first proportion of the set amount of hot water (hereinafter referred to as "first water level"). ) is determined as the lower limit water level. The upper limit water level determination condition corresponding to the first water level region is, for example, the water level detected by the water level sensor 63 when the empty bathtub 60 is filled with water up to a second proportion of the set amount of hot water (hereinafter referred to as "second water level"). ) is determined as the upper limit water level. The rising water level calculation method corresponding to the first water level region is, for example, a calculation method that subtracts the lower limit water level (first water level) of the first water level region from the upper limit water level (second water level) of the first water level region. Note that the first ratio is larger than 0% and smaller than 100%. The second percentage is less than 100%.

The second water level region is a region from a state in which the controller 22 fills the empty bathtub 60 with water up to a second proportion of the set amount of hot water until it drops water to the set amount of hot water. The lower limit water level determination condition corresponding to this second water level region is, for example, the lower limit of the water level (second water level) detected by the water level sensor 63 when the empty bathtub 60 is filled with water to a second proportion of the set hot water amount. It is decided as the water level. The upper limit water level determination condition corresponding to the second water level region is, for example, the water level detected by the water level sensor 63 when the empty bathtub 60 is filled with water up to the set amount of hot water (hereinafter also referred to as "set water level"). This is to be determined as the upper limit water level. The rising water level calculation method corresponding to the second water level area is, for example, a calculation method that subtracts the lower limit water level (second water level) of the second water level area from the upper limit water level (set water level) of the second water level area.

The third water level region is a region from when the controller 22 fills the empty bathtub 60 with water to the first proportion of the set amount of hot water to when the water reaches the set amount of hot water. The lower limit water level determination condition corresponding to this third water level region is, for example, the lower limit of the water level (first water level) detected by the water level sensor 63 when the empty bathtub 60 is filled with water to a first proportion of the set hot water amount. It is decided as the water level. The upper limit water level determination condition corresponding to the third water level region is, for example, the water level detected by the water level sensor 63 when the empty bathtub 60 is filled with water up to the set amount of hot water (hereinafter also referred to as "set water level"). This is to be determined as the upper limit water level. The rising water level calculation method corresponding to the third water level region is, for example, a calculation method that subtracts the lower limit water level (first water level) of the third water level region from the upper limit water level (set water level) of the third water level region.

The controller 22 calculates an area value A, an area value B, and an area value C (hereinafter also referred to as area values A to C) as the area values. The area value A corresponds to an example of the first area value, the area value B corresponds to an example of the second area value, and the area value C corresponds to an example of the third area value. The controller 22 calculates the area value A corresponding to the first water level region based on the amount of water dropped into the first water level region, and calculates the area value A corresponding to the second water level region based on the amount of water dropped into the second water level region. A value B is calculated, and an area value C corresponding to the third water level area is calculated based on the amount of water dropped into the third water level area. The controller 22 calculates each area value using Equation 1 below, for example.
[Area value (cm ² )]=[Amount of water dropped into the corresponding water level area (cm ³ )]/[Rising water level in the corresponding water level area (cm)]...Equation 1

For example, the controller 22 calculates the area value A as follows. The controller 22 calculates a first ratio of the set amount of hot water and a second ratio of the set amount of hot water based on the set amount of hot water stored in the memory 22B. Then, the controller 22 calculates the amount of water dropped into the first water level region by subtracting the first ratio of the set amount of hot water from the second ratio of the set amount of hot water. Further, the controller 22 calculates the rising water level in the first water level region by subtracting the first water level from the second water level. Then, the controller 22 calculates the area value A by calculating "the amount of water dropped into the first water level area"/"the rising water level in the first water level area".

Further, the controller 22 calculates the area value B as follows, for example. The controller 22 calculates a second ratio of the set amount of hot water based on the set amount of hot water stored in the memory 22B. Then, the controller 22 calculates the amount of water dropped into the second water level region by subtracting the second ratio of the set amount of hot water from the set amount of hot water. The controller 22 also calculates the rising water level in the second water level region by subtracting the second water level from the set water level. Then, the controller 22 calculates the area value B by calculating "the amount of water dropped into the second water level area"/"the rising water level in the second water level area".

Further, the controller 22 calculates the area value C as follows, for example. The controller 22 calculates a first ratio of the set amount of hot water based on the set amount of hot water stored in the memory 22B. Then, the controller 22 calculates the amount of water dropped into the third water level region by subtracting the first ratio of the set amount of hot water from the set amount of hot water. Further, the controller 22 calculates the rising water level in the third water level region by subtracting the first water level from the set water level. Then, the controller 22 calculates the area value C by calculating "the amount of water dropped into the third water level area"/"the rising water level in the third water level area". The controller 22 stores the calculated area values A to C in the memory 22B.

The controller 22 sets the area value C when the water level of the remaining water in the bathtub 60 is less than the threshold value when the start condition for drop-in control is satisfied and the relationship between the plurality of area values does not satisfy the normal condition. If the remaining water level in the bathtub 60 is equal to or higher than the threshold value, area value B is selected. The normal condition is a condition for determining that the shape inside the bathtub 60 is a general shape that is approximately constant in the vertical direction or gradually expands toward the top, as in the bathtub 60A shown in FIG. 3(A). It is. The normal condition is a bathtub 60B shown in FIG. 3B, in which a seat surface is formed that is one step higher than the bottom surface, and the lower part of the bathtub 60 is significantly narrower than the upper part. The condition is that the bathtub 60 is excluded.

For example, the controller 22 determines that the normal condition is satisfied when the ratio of area value A to area value B is within a predetermined normal range, and the controller 22 determines that the normal condition is satisfied when the ratio of area value A to area value B is within a predetermined normal range. If it is not within the range, it is determined that the normal condition is not satisfied. The normal range is, for example, a range in which "area value A/area value B" satisfies the following formula 2.
0.67<[Area value A (cm ² )/Area value B (cm ² )]<1.5...Formula 2
The threshold value is, for example, the second water level.

(Area value setting process)
Next, an area value setting process for setting an area value will be explained. The controller 22 performs the area value setting process according to the flow shown in FIGS. 4 and 5, for example. For example, the controller 22 executes the area value setting process after turning on the power, and determines in S11 of FIG. 4 whether or not the area value setting condition is satisfied. The area value setting condition may be, for example, "the test run start condition for starting the test run is met" or "the first hot water filling start condition is met after the bathtub 60 is installed". Alternatively, it may be "the first hot water filling start condition is satisfied after the set amount of hot water is set", or it may be another condition. Furthermore, if the setting of the area value fails even though the area value setting condition is met, "the next hot water filling start condition is met" may be set as the area value setting condition.

In addition, it is preferable that the area value setting condition is satisfied when the inside of the bathtub 60 is empty. For example, the area value setting condition is a condition that is satisfied in response to a predetermined operation by the user (for example, an operation to start a trial run using the operation units 81C, 82C, an operation to start filling water, etc.), and that the inside of the bathtub 60 is in an empty state. The bathtub 60 may be left in an empty state by the user who visually confirms this and performs the predetermined operation described above. As another example, the controller 22 itself may determine whether the inside of the bathtub 60 is empty when determining whether the area value setting condition is satisfied. As a method for determining whether or not the interior of the bathtub 60 is empty, for example, the controller 22 may determine based on the detection result of the water level sensor 63. More specifically, when it is determined that the remaining water level in the bathtub 60 is below the adapter water level based on the detection result of the water level sensor 63, it is determined that the bathtub 60 is empty. good.

When the controller 22 determines that the area value setting condition is not satisfied (S11: No), the controller 22 returns to the process of S11 and enters a standby state until the area value setting condition is satisfied. When the controller 22 determines that the area value setting condition is satisfied (S11: Yes), the controller 22 starts the drop-in control described above in S12. That is, the controller 22 starts supplying hot water into the bathtub 60 via the drop pipe 70 by opening the hot water supply electromagnetic valve 72 provided in the drop pipe 70 . The controller 22 detects the amount of water supplied to the bathtub 60 based on the signal from the water amount sensor 74, and calculates the amount of water to be poured into the bathtub 60 by integrating the detected amount of supplied water, thereby controlling the amount of water to be poured into the bathtub 60. Calculate the amount dropped after starting.

After starting the drop-in control, the controller 22 determines in S13 whether the amount of hot water dropped into the bathtub 60 has reached a first ratio of the set amount of hot water (see FIGS. 6(A) and 6(B)). . The set amount of hot water is stored in the memory 22B. More specifically, various data are stored in a predetermined storage area of the memory 22B in association with addresses, as illustrated in FIG. 7, and the set hot water amount is stored at address 014. Further, the first ratio is, for example, 50%, and the adapter 61 that connects the inside of the bathtub 60 with the return piping 67 and the outgoing piping 68 (see FIGS. 3(A)(B) and 6(A)(B)) This corresponds to the amount of water that is dropped to the extent that it is submerged in water. The first ratio is stored in advance in the memory 22B. Therefore, the controller 22 reads the set hot water amount Qset and the first ratio stored at address 014 of the memory 22B, and calculates the first ratio of the set hot water amount Qset based on the read set hot water amount Qset and first ratio. The controller 22 determines whether the first ratio of the set hot water amount Qset calculated in this way has been reached. Note that the set hot water amount Qset is, for example, set to an initial value (for example, 160L) in advance, and is changed according to the operation of the operation units 81C and 82C.

When the controller 22 determines that the amount of hot water poured into the bathtub 60 has not reached the first ratio of the set hot water amount Qset (S13: No), the controller 22 returns to the process of S13 and stops pouring hot water into the bathtub 60. The process of S13 is repeated until it is determined that the amount has reached the first ratio of the set hot water amount Qset. When the controller 22 determines that the amount of hot water poured into the bathtub 60 has reached the first ratio of the set hot water amount Qset (S13: Yes), the controller 22 adjusts the water level in the bathtub 60 based on the detection result of the water level sensor 63 in S14. is detected as the first water level SUadp (see FIGS. 6(A) and 6(B)). In other words, the first water level SUadp is the water level in the bathtub 60 when a first proportion of the set amount of hot water is poured into the empty bathtub 60.

After detecting the first water level SUadp in S14, the controller 22 determines in S15 that the amount of hot water dropped into the bathtub 60 has reached a second ratio of the set amount of hot water (see FIGS. 6(A) and (B)). Determine whether or not. The second ratio is higher than the first ratio and lower than 100%, for example, 80%. The second ratio is stored in advance in the memory 22B. The second ratio of the set amount of hot water is calculated based on the set amount of hot water Qset and the second ratio stored at address 014 of the memory 22B. If the controller 22 determines that the amount of hot water poured into the bathtub 60 has not reached the second ratio of the set amount of hot water (S15: No), the controller 22 returns to the process of S15 and changes the amount of hot water poured into the bathtub 60. The process of S15 is repeated until it is determined that the amount of hot water has reached the second ratio of the set amount of hot water. When the controller 22 determines that the amount of hot water poured into the bathtub 60 has reached the second ratio of the set amount of hot water (S15: Yes), the controller 22 adjusts the water level in the bathtub 60 based on the detection result of the water level sensor 63 in S16. It is detected as the second water level SUhalf (see FIGS. 6(A) and 6(B)). In other words, the second water level SUhalf is the water level in the bathtub 60 when a second proportion of the set amount of hot water is poured into the empty bathtub 60.

After detecting the second water level SUhalf in S16, the controller 22 determines in S17 whether the amount of hot water poured into the bathtub 60 has reached the set amount of hot water stored at address 014 of the memory 22B. do. If the controller 22 determines that the amount of hot water poured into the bathtub 60 has not reached the set amount of hot water (S17: No), the controller 22 returns to the process of S17 and sets the amount of hot water poured into the bathtub 60 to the set amount of hot water. The process of S17 is repeated until it is determined that the point has been reached. When the controller 22 determines that the amount of hot water poured into the bathtub 60 has reached the set amount of hot water (S17: Yes), the controller 22 sets the water level in the bathtub 60 to the reference water level SUmemo ( (see FIGS. 6(A) and 6(B)). In other words, the reference water level SUmemo is the water level in the bathtub 60 when a set amount of hot water is poured into the empty bathtub 60.

After detecting the reference water level SUmemo in S18, the controller 22 ends the dropping control in S19. That is, the controller 22 stops the supply of hot water to the bathtub 60 by closing the hot water supply electromagnetic valve 72 provided in the drop pipe 70 . After completing the drop-in control in S19, the controller 22 calculates area values A, B, and C in S20. An example of a specific calculation method will be described below.

The controller 22 calculates the "amount of water dropped into the first water level region" using equation 3 below.
[Amount of water dropped into the first water level area] = [Set amount of hot water] x [Second ratio] - [Set amount of hot water] x [First ratio]...Equation 3
The controller 22 calculates the "increased water level in the first water level region" using equation 4 below.
[Rising water level in the first water level area] = [Second water level (cm)] - [First water level (cm)]...Equation 4
The "set hot water amount", "second ratio", and "first ratio" are values stored in the memory 22B. The "second water level" is the value detected in S16. The "first water level" is the value detected in S14. The controller 22 calculates the area value A by substituting the "amount of water dropped into the first water level area" calculated by Equation 3 and the "rising water level in the first water level area" calculated by Equation 4 into Equation 1 above. calculate.

The controller 22 calculates "the amount of water dropped into the second water level region" using the following equation 5.
[Amount of water dropped into the second water level area (cm ³ )] = [Set amount of hot water (cm ³ )] - [Set amount of hot water (cm ³ )] × [Second ratio]...Equation 5
The controller 22 calculates the "increased water level in the second water level region" using Equation 6 below.
[Rising water level in the second water level area (cm)] = [Reference water level (cm)] - [Second water level (cm)]...Formula 6
The "set hot water amount" and "second ratio" are values stored in the memory 22B. The "reference water level" is the value detected in S18. The "second water level" is the value detected in S16. The controller 22 calculates the area value B by substituting the "amount of water dropped into the second water level area" calculated by Equation 5 and the "rising water level in the second water level area" calculated by Equation 6 into Equation 1 above. calculate.

The controller 22 calculates the "amount of water dropped into the third water level region" using equation 7 below.
[Amount of water dropped into the third water level area (cm ³ )] = [Set amount of hot water (cm ³ )] - [Set amount of hot water (cm ³ )] × [First ratio]...Equation 7
The controller 22 calculates the "increased water level in the third water level region" using equation 8 below.
[Rising water level in the third water level area (cm)] = [Reference water level (cm)] - [First water level (cm)]...Formula 8
The "set amount of hot water" and "first ratio" are values stored in the memory 22B. The "reference water level" is the value detected in S18. The "first water level" is the value detected in S14. The controller 22 calculates the area value C by substituting the "amount of water dropped into the third water level area" calculated by Equation 7 and the "rising water level in the third water level area" calculated by Equation 7 into Equation 1 above. calculate.

After calculating the area values A, B, and C in S20, the controller 22 stores the area values A, B, and C in the memory 22B. More specifically, the controller 22 stores area value A at address 011, area value B at address 012, and area value C at address 013. Further, when storing the area values A, B, and C, the controller 22 stores the first water level SUadp detected in S14 at address 004, stores the second water level SUhalf detected in S16 at address 006, [Set amount of hot water] x [1st ratio] is stored in address 005 as "amount of water dropped to the 1st ratio Qadp", and [set amount of hot water] x [2nd ratio] is stored as "amount of water dropped to the 2nd ratio Qhalf". Stored at address 007.

After storing the area values A, B, and C, the controller 22 determines in S31 of FIG. 5 whether the preconditions are satisfied. The preconditions are, for example, "the water level sensor 63 is not abnormal", "the water level detection is not defective", and "the calculation of the area values A, B, and C is not defective". When the controller 22 determines that the preconditions are satisfied (S31: Yes), the controller 22 determines whether the ratio of the area value A to the area value B is within a predetermined normal range (S32). The normal range is, for example, a range in which "Area value A/Area value B" satisfies Equation 2 described above.

When the controller 22 determines that the ratio of the area value A to the area value B is within a predetermined normal range (S32: Yes), the controller 22 sets the area value C to the set bathtub area at address 001 of the memory 22B (see FIG. 7). ). Further, the controller 22 stores the reference water level SUmemo detected in S18 at address 002 (see FIG. 7), and stores the set hot water amount at address 014 as "amount Qmemo dropped to the reference water level" at address 003 (see FIG. 7). do. The controller 22 also resets a "failure counter" and a "temporary area" stored at address 015, which will be described later. After completing the process of S33, the controller 22 ends the area value setting process.

If the controller 22 determines in S31 that the preconditions are not satisfied (S31: No), or if it determines in S32 that the ratio of area value A to area value B is not within a predetermined normal range (S32 : No), it is determined that the setting of the area value has failed, and 1 is added to the failure counter in S34. After S34, the controller 22 determines in S35 whether the failure counter has become 3 or more.

If the controller 22 determines that the failure counter is less than 3 (S35: No), it performs a temporary area setting process in S36. In the temporary area setting process, the controller 22 stores the smallest value among the area values A, B, and C stored at addresses 011 to 013 at address 015 (see FIG. 7) as the temporary area. However, if the temporary area has already been stored at address 015 and the already stored temporary area is smaller than any of the area values A, B, and C stored at addresses 011 to 013, the controller 22 will change the temporary area. It will not be updated. After completing the temporary area setting process (S36), the controller 22 ends the area value setting process.

If the controller 22 determines in S35 that the failure counter is 3 or more (S35: Yes), it determines in S37 whether or not the preconditions are satisfied. This precondition may be the same as the precondition explained in the process of S31, or may be different. If the controller 22 determines in S37 that the precondition is satisfied (S37: Yes), it determines in S38 whether the specific condition is satisfied. The specific condition is a bathtub 60 that has a seat surface that is one step higher than the bottom, such as a bathtub 60B shown in FIG. This is a condition for specifying the bathtub 60.

For example, the controller 22 determines that the specific condition is satisfied when the ratio of area value B to area value A is within a predetermined specific range, and the controller 22 determines that the specific condition is satisfied when the ratio of area value B to area value A is within a predetermined specific range. If the specified condition is not within the specified range, it is determined that the specific condition is not satisfied. The specific range is, for example, a range where "area value B/area value A" satisfies the following formula 9.
1.5<[Area value B (cm ² )/Area value A (cm ² )]<3.0...Equation 9

When the controller 22 determines that the specific condition is satisfied (S38: Yes), the area value C stored at address 013 in S39 is stored at address 001 as the set bathtub area. Further, when the controller 22 determines that the specific condition is not satisfied (S38: No), the controller 22 stores a predetermined fixed value as the set bathtub area at address 001 (S40). The fixed value is, for example, a value determined by Equation 10 below.
[Fixed value (cm ² )]=[Set hot water amount (cm ³ )]/40...Formula 10

Furthermore, when storing the set bathtub area in S39 or S40, the controller 22 stores the reference water level SUmemo detected in S18 at address 002 (see FIG. 7), and sets the set hot water amount at address 014 to "Drop down to the reference water level". Quantity Qmemo" is stored at address 003 (see FIG. 7). The controller 22 also resets a "failure counter" and a "temporary area" stored at address 015, which will be described later. After completing the process of S39 or S40, the controller 22 ends the area value setting process. When the area value setting process is completed, it is executed again, and thus it is repeatedly executed.

(Automatic hot water filling control)
The controller 22 performs automatic hot water filling control according to the flow shown in FIG. 8, for example. After turning on the power, the controller 22 executes the automatic hot water filling control shown in FIG. 8 and determines whether hot water filling start conditions are satisfied (S51). The hot water filling start condition corresponds to an example of the start condition for drop-in control. The hot water filling start conditions are, for example, ``the hot water filling start operation was performed using the operation unit 81C of the first remote controller 81 (for example, the automatic button provided in advance was pressed)'', and ``the second remote controller 82's operation unit 82C has been performed (for example, an automatic button provided in advance has been pressed),""the reservation-based filling conditions have been met," and so on. The system remains in a standby state until the hot water filling start conditions are satisfied, and the determination of No is repeated in S51.

When the controller 22 determines that the hot water filling start condition is satisfied (S51: Yes), the controller 22 determines whether there is any water remaining in the bathtub 60 (S52). As a method for determining whether or not the interior of the bathtub 60 is empty, for example, the controller 22 may determine based on the detection result of the water level sensor 63. More specifically, when it is determined that the remaining water level in the bathtub 60 is below the adapter water level based on the detection result of the water level sensor 63, it is determined that the bathtub 60 is empty. good. When the controller 22 determines that there is no remaining water (S52: No), the controller 22 pours the set amount of hot water stored in the address 014 into the bathtub 60 (S53), and ends the automatic hot water filling control.

When the controller 22 determines that there is residual water (S52: Yes), the controller 22 calculates the set water level (S54). The set water level SUset is calculated using Equation 11 below.
"Set water level (cm)" = Standard water level (cm) + ("Set water level (cm ³ )" - "Amount of water dropped to the standard water level (cm ³ )") / "Set water level calculation area (cm ² )" ・・・Formula 11
"Reference water level" is the value stored at address 002, "set hot water amount" is the value stored at address 014, and "amount of water dropped to the reference water level" is the value stored at address 003. be. "Setting water level calculation area" is the "setting bathtub area" stored in address 001 when the value of the failure counter is less than 3, and "setting water level calculation area" is the "setting bathtub area" stored in address 001 when the value of the failure counter is 3 or more. If “amount of hot water Qset”≧“amount of water dropped to the second ratio Qhalf” and “amount of water poured into the second ratio Qmemo”≧“amount of water dropped to the second ratio Qhalf”, the area value B stored at address 012 is used. Yes, and if it is other than this, it is the "set bathtub area" stored at address 001.

After calculating the set water level (S54), the controller 22 determines whether normal conditions are satisfied (S55). The controller 22 determines that the normal condition is satisfied when the value of the failure counter is less than 3, and determines that the normal condition is not satisfied when the value of the failure counter is 3 or more. That is, in the area value setting process, if the controller 22 determines that the ratio of area value A to area value B is within the normal range while performing the process of S32 three times, it determines that the normal condition is satisfied, If it is determined three times in a row that the ratio of the area value A to the area value B is not within the normal range in the process of S32, it is determined that the normal condition is not satisfied. When the controller 22 determines that the normal conditions are satisfied (S55: Yes), the controller 22 selects the set bathtub area stored at address 001 (S56). If the controller 22 determines that the normal conditions are not satisfied (S55: No), the controller 22 determines whether the water level of the remaining water in the bathtub 60 is equal to or higher than the threshold (S57). The threshold value is, for example, the second water level SUhalf stored at address 006. When the controller 22 determines that the water level of the remaining water is equal to or higher than the threshold value (S57: Yes), the controller 22 selects the area value B of address 012 (S58), and when it determines that the water level of the remaining water is less than the threshold value ( S57: No), area value C of address 013 is selected (S59).

The controller 22 calculates the insufficient amount of hot water relative to the set hot water amount based on the area value selected in S56, S58, or S59 (S60). The shortage amount is calculated, for example, using the following equation 12.
“Insufficient amount (cm ³ )” = (“Set water level (cm)” - “Residual water level (cm)”) × “Insufficient hot water amount calculation area (cm ² )” ... Formula 12
The “set water level” is a value calculated using Equation 11. “Residual water level” is a value detected by the water level sensor 63. The "insufficient hot water amount calculation area" is the area value selected in S56, S58, or S59. Note that the controller 22 determines that there is an abnormality when the "insufficient amount" does not satisfy Expression 13 below.
"Insufficient amount (cm ³ )" ≦ "Set hot water amount (cm ³ )" - "Predetermined value (cm ³ )" ...Formula 13
The “deficit amount” is a value calculated using Equation 12. The “set hot water amount” is the value stored at address 014. The "predetermined value" is, for example, 15,000 (cm ³ ).

After calculating the amount of shortage, the controller 22 drops the calculated amount of hot water into the bathtub 60 (S61). After the controller 22 pours the insufficient amount of hot water into the bathtub 60, it ends the automatic hot water filling control. When the automatic hot water filling control is finished, it is executed again, and is thereby repeatedly executed.

The following description relates to an example of the effect of this configuration.
The hot water supply system 1 calculates the area value of each of the plurality of water level regions calculated based on the detection results of the water level sensor 63 (specifically, the volume of each water level region divided by the water level (height) of each water level region). Based on the area value selected based on the water level of the remaining water in the bathtub 60 from among values), the water level of the remaining water, and the set amount of hot water, it is possible to calculate the insufficient amount of hot water that is insufficient for the set amount of hot water. . Therefore, according to this hot water supply system, it is possible to more accurately calculate the amount of shortage in a bathtub whose area value varies depending on the water level region.

According to the hot water supply system 1, by calculating each area value for each water level area according to the rising water level calculation method, it is possible to easily calculate each area value for each water level area.

When the water level of the remaining water in the bathtub 60 is less than the threshold value and the shortage is widespread, the hot water supply system 1 selects the area value C corresponding to the third wide water level region, If the area is limited to a relatively upper part of the water level area, the area value B corresponding to the second water level area is selected. Therefore, according to this hot water supply system 1, even if the water level of the remaining water in the bathtub 60 is limited to a relatively upper portion in the bathtub 60 having a shape where the area value differs depending on the water level region, it is possible to more accurately The amount of shortage can be calculated.

According to the hot water supply system 1, a more accurate amount of shortage can be calculated even for a bathtub whose shape has a large difference in area value A and area value B.

<Other embodiments>
The present disclosure is not limited to the embodiments described above and illustrated in the drawings. For example, the features of the embodiments described above or below can be combined in any combination without contradicting each other. Furthermore, any feature of the embodiments described above or below may be omitted unless explicitly stated as essential. Furthermore, the embodiment described above may be modified as follows.

In the embodiment described above, the second water level region is defined as the region from the state in which the empty bathtub 60 is filled with water up to the second ratio until the set amount of hot water is filled. However, the second water level region may be any region from a state in which water has been poured into the empty bathtub 60 to a third proportion larger than the first proportion to a state in which water has been poured to a set amount of hot water, and the third proportion is as follows. The ratio may be the same as the second ratio as in the embodiment described above, or it may be a ratio different from the second ratio. More specifically, the third ratio may be smaller or larger than the second ratio. That is, the first water level area and the second water level area may partially overlap or may be separated from each other. Note that the third ratio is smaller than 100%.

In the embodiment described above, the area between the first water level and the reference water level was configured to be divided into two water level areas, but it may be configured to be divided into three or more water level areas. Then, the controller 22 may calculate an area value for each water level area divided into three or more areas, and calculate the shortage amount based on these calculated area values.
In the embodiment described above, only one area value is selected for use in calculating the amount of shortage, but a configuration may be adopted in which two or more area values are selected.
In the above-described embodiment, if the area value calculation fails three times, it is finally determined that the normal condition is not satisfied, but if the area value calculation fails once, twice, or four or more times, the normal condition is not satisfied. The configuration may be such that it is determined that there is no such information.

It should be noted that the embodiments disclosed herein are illustrative in all respects and should not be considered restrictive. The scope of the present invention is not limited to the embodiments disclosed herein, and includes all modifications within the scope indicated by the claims or within the scope equivalent to the claims. is intended.

1...Hot water system 4...Gas burner (burner)
6...Hot water supply side heat exchanger (heat exchanger)
10... Hot water pipe (water pipe)
12... Water inlet pipe (water pipe)
20...Piping (water pipe)
22...Controller (drop-in control section, calculation section, shortage amount calculation section)
60...Bathtub 63...Water level sensor (water level detection part)
66...Piping (communication pipe)
70...Drop pipe (communication pipe)

Claims (5)

A water pipe that passes water introduced from the outside,
a burner that burns combustion gas to produce exhaust gas;
a heat exchanger that is provided in the middle of the water pipe and transfers heat of the exhaust gas to water passing through the water pipe;
a communication pipe that leads the water heated by the heat exchanger to the bathtub through the water pipe;
a drop-in control unit that performs drop-in control to supply a set value of water into the bathtub via the communication pipe;
a water level detection unit that detects the water level in the bathtub;
a calculation unit that calculates an area value of each of a plurality of water level regions having different height levels based on a detection result of the water level detection unit when water is dropped into the bathtub;
Equipped with
The drop-in control section is
In a case where the relationship between the plurality of area values does not satisfy the normal condition, if the start condition for the drop-in control is satisfied, at least one of the area values is determined based on the water level of the remaining water in the bathtub. Select the area value,
a shortage amount calculation unit that calculates a shortage amount with respect to the set value based on the selected area value, the water level of the remaining water, and the set value;
Hot water system with. The calculation unit has a plurality of rising water level calculation methods defined for each water level area, in which a lower limit water level determination condition and an upper limit water level determination condition are defined, and calculates using each of the rising water level calculation methods when water is dropped into the bathtub. The hot water supply system according to claim 1, wherein each of the area values for each water level region corresponding to each of the rising water level calculation methods is calculated based on each rising water level calculated. The plurality of water level regions include a first water level region in which the empty bathtub is filled with water to a first percentage of the set value to a second percentage that is larger than the first percentage; a second water level region from a state in which water is dropped to a third ratio larger than the first ratio to the empty bathtub to a state in which water is dropped to the set value; A third water level region is defined from a state in which the water has dropped to the first ratio to a state in which the water has dropped to the set value,
The calculation unit calculates a first area value corresponding to the first water level area based on the amount of water dropped into the first water level area, and calculates the first area value corresponding to the first area value based on the amount of water dropped into the second water level area. calculating a second area value corresponding to the water level area; calculating a third area value corresponding to the third water level area based on the amount of water dropped into the third water level area;
The drop-in control section is
In a case where the relationship between the plurality of area values does not satisfy a normal condition, the third area value is selected if the water level of the residual water in the bathtub is less than a threshold value when the start condition is satisfied. The hot water supply system according to claim 1 or 2, wherein the second area value is selected when the water level of the remaining water in the bathtub is equal to or higher than the threshold value. The hot water supply system according to claim 3, wherein the dropping control unit determines that the normal condition is not satisfied when the ratio of the first area value to the second area value is not within a predetermined normal range. The hot water supply system according to claim 3 or 4, wherein the third ratio is the same as the second ratio.

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