Storage-type hot water supply system

Abstract

To provide a storage type hot water supply system capable of promptly controlling a mixing ratio in a mixing section to an appropriate mixing ratio immediately after start of hot water supply.SOLUTION: A control device 70 of a storage type hot water supply system 1 sequentially executes: processing for acquiring a measurement value of a tank inner hot water temperature and a measurement value of a supply water temperature during stop of hot water supply to a hot water supply target section and determining a target value of a mixing ratio from the measurement value of the tank inner hot water temperature, the measurement value of the supply water temperature and a target temperature of hot water obtained in a mixing section 44 so that a temperature of hot water obtained in the mixing section becomes a target temperature when hot water supply to the hot water supply target section is started; and processing for controlling the mixing ratio to the determined target value.SELECTED DRAWING: Figure 4

Description

Technical Field

[0001] The present invention relates to a hot water storage type hot water supply system.

Background Art

[0002] In a hot water storage type hot water supply system including a hot water storage tank for storing heated hot water, a mixing unit connected to the hot water storage tank is provided so that water (hot water supply water in an unheated state) can be mixed with the hot water discharged from the hot water storage tank, which is the hot water discharged from the tank. When supplying hot water to the hot water supply target section, a system is known in which the hot water whose temperature is controlled by the mixing unit is supplied via a combustion type heat source machine or by bypassing the combustion type heat source machine (see, for example, Patent Documents 1 and 2).

[0003] And in Patent Documents 1 and 2, during the stop of hot water supply (during water stop), usually, the mixing ratio of the hot water discharged from the tank and the hot water supply water in the mixing unit is maintained at the ratio at the end of the previous hot water supply (the operating state of the valve device for adjusting the mixing ratio is maintained). In a specific situation where there is a risk that the temperature of the hot water obtained in the mixing unit immediately after the start of hot water supply becomes excessively high, a technique has been proposed in which the mixing ratio of the hot water discharged from the tank and the hot water supply water in the mixing unit is controlled to a ratio that increases the flow rate of the hot water supply water.

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Patent Document 2

Summary of the Invention

Problems to be Solved by the Invention

[0005] In the technologies described in Patent Documents 1 and 2, in particular, when the mixing ratio is maintained at the state it was at the end of the previous hot water supply while the hot water supply is stopped, the mixing ratio maintained while the hot water supply is stopped tends to deviate from the mixing ratio required to control the hot water obtained at the mixing unit to the required target temperature immediately after the hot water supply is started, due to changes in the temperature of the hot water in the hot water storage tank during the hot water supply stop (temperature rise due to heating or temperature drop due to heat dissipation), or changes in the set value of the target hot water supply temperature.

[0006] Furthermore, even if the mixing ratio is controlled to a ratio that increases the flow rate of hot water while the hot water supply is stopped, if the target hot water temperature setting is changed to a higher temperature than the one used during hot water supply, the mixing ratio during the hot water supply stoppage is likely to deviate from the ratio required immediately after the hot water supply is restarted.

[0007] In this case, because it takes time for the actual mixing ratio to reach the required value immediately after the start of hot water supply, the time required for temperature-controlled hot water to be supplied to the target hot water supply area becomes longer. In particular, in systems where the flow path from the mixing unit to the target hot water supply area is relatively long, the time it takes for hot water to reach the target hot water supply area from the mixing unit, in addition to the delay in controlling the mixing ratio, makes it easy for the user to feel that the time it takes for hot water to be supplied to the target hot water supply area is too long.

[0008] This invention was made in view of the above background, and aims to provide a storage-type hot water supply system that can quickly control the mixing ratio in the mixing section to an appropriate mixing ratio immediately after the start of hot water supply. [Means for solving the problem]

[0009] The present invention provides a storage-type hot water supply system that, in order to achieve the above objective, comprises a storage tank for storing hot water heated by a heating device, a mixing unit connected to the storage tank that can mix hot water supplied to the tank (which is the hot water supplied to the storage tank) with hot water supplied to the hot water supply unit, and can adjust the mixing ratio of the tank (which is the hot water supplied to the tank) and the hot water supplied to the hot water supply unit, and a control device that has a function to control the mixing ratio, wherein the control device is configured to have a function to control the mixing ratio so that the temperature of the hot water obtained in the mixing unit reaches a predetermined target temperature when hot water is supplied to the target unit. The control device is configured to sequentially perform the following steps: acquire an observed value of the water temperature in the hot water storage tank and an observed value of the water supply temperature while the hot water supply to the hot water supply target unit is stopped; determine a target value for the mixing ratio from the observed value of the water temperature in the tank, the observed value of the water supply temperature and the predetermined target temperature, so that the temperature of the water obtained in the mixing unit when the hot water supply to the hot water supply target unit is started becomes the predetermined target temperature; and control the mixing ratio to the determined target value (First Invention).

[0010] In this invention, observed temperature values, such as the observed water temperature inside the tank, refer to values ​​obtained by detecting the temperature using a temperature sensor (detected values), or values ​​obtained by estimating the temperature based on the correlation between the detected values ​​of one or more state variables having a certain correlation with the temperature (estimated values). Furthermore, the mixing ratio during the suspension of hot water supply to the hot water supply target unit refers, more specifically, to the mixing ratio achieved in the mixing unit when hot water supply to the hot water supply target unit is resumed during the suspension of hot water supply.

[0011] According to the first invention described above, while the hot water supply to the hot water supply target is stopped, the mixing ratio in the mixing unit is controlled to the target value determined as described above. Therefore, the mixing ratio immediately before the start of hot water supply can be made to match or nearly match the mixing ratio required for temperature control so that the temperature of the hot water obtained in the mixing unit at the start of hot water supply reaches a predetermined target temperature. Therefore, according to the first invention, it is possible to quickly control the mixing ratio in the mixing unit to an appropriate mixing ratio immediately after the start of hot water supply.

[0012] In the first invention described above, the mixing unit is connected to the hot water storage tank so that hot water from the hot water storage tank is supplied from the top of the hot water storage tank, and a configuration may be adopted in which the mixing unit is equipped with a first temperature sensor mounted on the side of the top of the hot water storage tank and a second temperature sensor located near the upstream end of the flow path connecting the mixing unit to the hot water storage tank or located in the upper part of the hot water storage tank as a temperature sensor for detecting the temperature of the hot water in the hot water storage tank.

[0013] In this case, it is preferable that the control device is configured to determine the target value of the mixing ratio using the higher of the temperature detected by the first temperature sensor and the temperature detected by the second temperature sensor as the observed value of the water temperature in the tank while the supply of hot water to the hot water target unit is stopped (Second Invention).

[0014] In this case, when the hot water supply is stopped, the temperature detected in real time by the first temperature sensor or the second temperature sensor may be lower than the actual temperature of the hot water dispensed from the hot water supply tank during hot water supply, due to the influence of the distribution of hot water in the hot water storage tank, the heating state by the heating device, the air in the hot water storage tank, etc.

[0015] Therefore, in the second invention, the control device determines the target value of the mixing ratio using the higher of the temperature detected by the first temperature sensor and the temperature detected by the second temperature sensor as the observed value of the water temperature in the tank when the hot water supply is stopped. This makes it possible to avoid as much as possible determining the target value of the mixing ratio using a temperature lower than the actual temperature of the hot water dispensed from the hot water storage tank during hot water supply.

[0016] As a result, it is possible to prevent, as much as possible, the mixing ratio immediately before the start of hot water supply from becoming a ratio on the side where more hot water on the hot water storage tank side is used than the mixing ratio required for temperature control so that the temperature of the hot and cold water obtained in the mixing section at the start of hot water supply reaches a predetermined target temperature.

[0017] In the second invention, it is preferable that the control device is configured to control the mixing ratio using the temperature detection value by the second temperature sensor without using the temperature detection value by the first temperature sensor among the first temperature sensor and the second temperature sensor when supplying hot water to the hot water supply target section (third invention).

[0018] When supplying hot water to the hot water supply target section, hot water is supplied from the upper part of the hot water storage tank to the mixing section, so the temperature detection value by the second temperature sensor accurately indicates the temperature of the hot water actually supplied to the mixing section. Therefore, it is possible to appropriately perform temperature control so that the temperature of the hot water obtained in the mixing section reaches the required target temperature during hot water supply.

Brief Description of Drawings

[0019] [Figure 1] A diagram showing the overall configuration of the hot water storage type hot water supply system according to an embodiment of the present invention. [Figure 2] A flowchart showing the processing (processing during hot water supply) by the control device provided in the hot water storage type hot water supply system according to the embodiment. [Figure 3] A graph exemplifying the operation characteristics of the mixing valve provided in the hot water storage type hot water supply system according to the embodiment. [Figure 4] A flowchart showing the processing (processing during hot water supply stop) by the control device provided in the hot water storage type hot water supply system according to the embodiment.

Embodiments for Carrying Out the Invention

[0020] An embodiment of the present invention will be described below with reference to FIGS. 1 to 4. The stored hot water supply system 1 of this embodiment includes a tank unit 10 equipped with a hot water storage tank 11 for storing heated hot water, a heat pump unit 20 as a heating device for heating the hot water stored in the hot water storage tank 11, a water supply circuit 30 configured to supply hot water for hot water supply supplied from a water supply source (not shown) to the hot water storage tank 11, a hot water supply circuit 40 configured to supply the hot water in the hot water storage tank 11 to a hot water supply target part (not shown) such as a kitchen, a bathroom, or a washroom, and a combustion type heat source machine 50 configured to heat the hot water supplied to the hot water supply target part by the hot water supply circuit 40.

[0021] The heat pump unit 20 is connected to the hot water storage tank 11 via a circulation path 21 for circulating hot water between the heat pump unit 20 and the hot water storage tank 11. The circulation path 21 includes a forward path 21a arranged to flow the hot water in the hot water storage tank 11 from the lower part of the hot water storage tank 11 to the heat pump unit 20, and a return path 21b arranged to flow the hot water from the heat pump unit 20 to the upper part of the hot water storage tank 11. By the operation of a pump (not shown) mounted on the heat pump unit 20 (or the tank unit 10), it is possible to circulate the hot water between the heat pump unit 20 and the hot water storage tank 11. A check valve 22 is assembled to the return path 21b.

[0022] And when the hot water is circulated between the heat pump unit 20 and the hot water storage tank 11, the heat pump unit 20 is configured to heat the hot water flowing through the heat pump unit 20 by a known heat pump operation (an operation that repeats evaporation (heat absorption), compression, condensation (heat release), and expansion of a refrigerant).

[0023] The water supply circuit 30 comprises an upstream water supply channel 31 from which hot water is supplied from a water source, and a tank water supply channel 32 and a bypass water supply channel 33 branched downstream of the upstream water supply channel 31. The tank water supply channel 32 is arranged to allow hot water to flow from the upstream water supply channel 31 to the lower part of the hot water storage tank 11, and the bypass water supply channel 33 is arranged to allow hot water to flow from the upstream water supply channel 31 to the mixing section 44 of the hot water supply circuit 40 without passing through the hot water storage tank 11. The mixing section 44 is the part that mixes the hot water supplied from the bypass water supply channel 33 with the hot water supplied from the hot water storage tank 11.

[0024] Furthermore, check valves 34 and 35 are installed in the tank water supply channel 32 and the bypass water supply channel 33, respectively. In addition, a flow sensor 36 is installed in the bypass water supply channel 33 to detect the water supply flow rate, which is the flow rate of hot water that flows through the bypass water supply channel 33 to the mixing section 44. Also, a temperature sensor 37 is installed in the upstream water supply channel 31 to detect the water supply temperature, which is the temperature of the hot water supplied from the water source to the upstream water supply channel 31.

[0025] The hot water supply circuit 40 includes a first hot water supply passage 41 arranged to allow hot water in the hot water storage tank 11 to flow from the top of the hot water storage tank 11 to the mixing section 44, a second hot water supply passage 42 arranged to allow hot water to flow from the mixing section 44 to the combustion type heat source unit 50, and a third hot water supply passage 43 arranged to supply hot water flowing out of the combustion type heat source unit 50 to a hot water supply target unit (not shown).

[0026] The mixing unit 44 is equipped with a mixing valve 45 configured to mix the hot water flowing in from the hot water storage tank 11 through the first hot water supply channel 41 with the hot water supply water flowing in from the bypass water supply channel 33 and discharge it into the second hot water supply channel 42. The mixing valve 45 is an electrically operated three-way valve or the like powered by a stepping motor (not shown), and is configured to variably adjust the mixing ratio, which is the ratio of the flow rate of hot water flowing from the hot water storage tank 11 through the first hot water supply channel 41 to the second hot water supply channel 42 (the flow rate of hot water coming out of the tank) to the flow rate of hot water supply water flowing from the bypass water supply channel 33 to the second hot water supply channel 42. By controlling the mixing ratio through the operation control of the mixing valve 45, it is possible to adjust the temperature of the hot water flowing from the mixing valve 45 to the second hot water supply channel 42 downstream (the temperature of the hot water supplied from the mixing valve 45 to the combustion type heat source unit 50).

[0027] To add to this, the valve device for controlling the mixing ratio is not limited to the mixing valve 45. For example, it is also possible to install flow control valves in both the first hot water supply channel 41 and the bypass water supply channel 33 and adjust the mixing ratio using these flow control valves.

[0028] The first hot water supply channel 41 is equipped with a temperature sensor 46 for detecting the tank outlet temperature, which is the temperature of the hot water dispensed from the top of the hot water storage tank 11, a check valve 47, and a flow sensor 48 for detecting the tank outlet flow rate, which is the flow rate of hot water from the hot water storage tank 11 to the mixing section 44. The temperature sensor 46 is installed in the first hot water supply channel 41 near its upstream end and functions as a temperature sensor for detecting the temperature of the hot water in the upper part of the hot water storage tank 11, near the connection point at the upstream end of the first hot water supply channel 41.

[0029] Furthermore, a temperature sensor 49 is installed near the upstream end of the second hot water supply passage 42 (near the mixing section 44) to detect the mixed hot water temperature, which is the temperature of the hot water supplied from the mixing section 44 to the combustion-type heat source unit 50.

[0030] Furthermore, multiple (for example, three) temperature sensors 12a, 12b, and 12c are mounted on the side of the hot water storage tank 11 (the outer side in the illustrated example) at intervals in the vertical direction. These temperature sensors 12a, 12b, and 12c are temperature sensors for detecting the temperature of the hot water in the hot water storage tank 11 at their respective height positions. Specifically, temperature sensor 12a is for detecting the temperature of the hot water in the upper part of the hot water storage tank 11, temperature sensor 12b is for detecting the temperature of the hot water in the middle part of the hot water storage tank 11 in the vertical direction, and temperature sensor 12c is for detecting the temperature of the hot water in the lower part of the hot water storage tank 11. Note that temperature sensors 12a, 12b, and 12c may also be mounted on the inner surface of the hot water storage tank 11.

[0031] The combustion-type heat source unit 50 comprises an inlet channel 51, a hot water outlet channel 52, a heat exchanger 53, and a burner 54. The hot water outlet channel 52 is connected to the downstream side of the inlet channel 51 via a water passage 53a of the heat exchanger 53. A second hot water supply channel 42 is connected to the upstream side of the inlet channel 51, and a third hot water supply channel 43 is connected to the downstream side of the hot water outlet channel 52.

[0032] Furthermore, a bypass channel 55 is connected in parallel with the water passage 53a of the heat exchanger 53 between the inlet channel 51 and the outlet channel 52, allowing hot water to flow from the inlet channel 51 to the outlet channel 52 without passing through the heat exchanger 53. A distribution valve 56 is installed at the connection point between the inlet channel 51 and the bypass channel 55, configured to distribute the hot water flowing in from the upstream inlet channel 51 to the downstream inlet channel 51 and the bypass channel 55.

[0033] The distribution valve 56 is configured with an electrically operated three-way valve or the like, and is configured to variably adjust the bypass ratio, which is the ratio between the flow rate of hot and cold water flowing from the upstream inlet channel 51 to the downstream inlet channel 51 (= the flow rate of hot and cold water flowing through the water passage 53a of the heat exchanger 53) and the flow rate of hot and cold water flowing from the upstream inlet channel 51 to the bypass channel 55.

[0034] To add to this, the valve device for controlling the bypass ratio is not limited to the distribution valve 56. For example, instead of the distribution valve 56, an electrically operated mixing valve can be installed at the connection point between the bypass passage 55 and the hot water outlet passage 52. This mixing valve is configured to mix the hot water flowing in from the upstream hot water outlet passage 52 with the hot water flowing in from the bypass passage 55 and discharge it to the downstream hot water outlet passage 52, and to adjust the mixing ratio. Alternatively, a flow control valve can be installed in either or both of the flow paths through the water passage 53a of the heat exchanger 53 (the inlet passage 51 downstream of the connection point between the inlet passage 51 and the bypass passage 55, or the hot water outlet passage 52 upstream of the connection point between the hot water outlet passage 52 and the bypass passage 55) and the bypass passage 55, and the bypass ratio can be adjusted using the flow control valve.

[0035] Furthermore, the combustion-type heat source unit 50 is equipped with a temperature sensor 57 that detects the temperature of the hot water flowing from the outlet passage 52 to the third hot water supply passage 43, which is the heat source unit outlet temperature. The temperature sensor 57 is installed in the outlet passage 52 downstream of the connection point between the outlet passage 52 and the bypass passage 55.

[0036] The burner 54 is, for example, a gas burner, and is supplied with fuel gas and combustion air by a fuel supply device and a blower (fan) (not shown). The burner 54 is arranged to heat the heat exchanger 53 with the heat of combustion (either sensible heat or latent heat, or both) generated by its combustion operation, and in turn, heat the hot water flowing through the water passage 53a of the heat exchanger 53. Note that the burner 54 is not limited to a gas burner, but may be a burner that burns liquid fuel such as kerosene.

[0037] As the combustion-type heat source unit 50 is configured as described above, it is possible to supply all or part of the hot water supplied from the second hot water supply channel 42 of the hot water supply circuit 40 to the third hot water supply channel 43 (and thereby to the part to be supplied with hot water) via the inlet channel 51, the water passage 53a of the heat exchanger 53 and the outlet channel 52. At this time, by operating the burner 54, it is possible to heat the hot water supplied from the second hot water supply channel 42 and raise its temperature. Furthermore, by adjusting both or either the fuel amount and the bypass ratio of the burner 54, it is possible to adjust the hot water outlet temperature of the heat source unit.

[0038] The storage-type hot water supply system 1 further includes a control device 70 that has the function of controlling the operation of the storage-type hot water supply system 1. The control device 70 is composed of one or more electronic circuit units, including, for example, a processor such as a microcontroller, memory, interface circuits, etc. For example, the control device 70 may be configured as a collection of multiple electronic circuit units that are separately mounted on the tank unit 10, the heat pump unit 20, and the combustion-type heat source unit 50, and that can communicate with each other. However, the control device 70 may be a single configuration.

[0039] The control device 70 is capable of communicating via wired or wireless means with a remote control 75 for the user to operate the hot water storage system 1. The remote control 75 includes an operation unit 75a with multiple operation switches, a display unit 75b that displays various information related to the operation of the hot water storage system 1, and the like.

[0040] The control panel 75a of the remote control 75 allows for operations such as turning the hot water supply operation on / off to the target hot water supply unit, and setting the target hot water temperature (specifically, the target value of the hot water temperature downstream of the heat source unit). The display panel 75b of the remote control 75 can display the set value of the target hot water temperature (hereinafter referred to as the hot water supply setting temperature) and the operating status of the storage-type hot water supply system 1.

[0041] The control device 70 can then control the operation of each of the controlled devices of the tank unit 10, the heat pump unit 20, and the combustion heat source unit 50 through the functions realized by the implemented hardware configuration and program (software configuration). In this case, the controlled devices of the tank unit 10 include the mixing valve 45, and the controlled devices of the heat pump unit 20 include equipment for operating the heat pump (compressor, expansion valve, etc.) and a pump for circulating hot and cold water (not shown).

[0042] Furthermore, the controlled equipment of the combustion-type heat source unit 50 includes the burner 54, distribution valve 56, etc. The operation of the burner 54 is controlled, in more detail, through the operation control of a fuel supply device, blower (fan), and ignition device (not shown).

[0043] Next, the operation of the storage-type hot water supply system 1 of this embodiment will be described. The control device 70 operates the heat pump unit 20 to heat the hot water in the storage tank 11 under predetermined conditions, such as when it detects that the storage tank 11 is out of hot water. In this case, the operation of the heat pump unit 20 is controlled so that the entire or almost entire volume of the hot water in the storage tank 11 reaches a predetermined temperature or higher (for example, 45°C or higher).

[0044] The state of the hot water storage tank 11 being depleted is defined as a state in which the amount of hot water at a predetermined temperature or higher inside the hot water storage tank 11 has fallen to a predetermined amount or less. Whether or not the hot water storage tank 11 is depleted can be determined, for example, based on the output of temperature sensors 12a, 12b, and 12c attached to the side of the hot water storage tank 11.

[0045] Next, the operation during hot water supply to the hot water supply target will be explained. When the control device 70 starts supplying water to the hot water supply target (water flow exceeding a predetermined flow rate) by opening a hot water tap (not shown) in the hot water supply target, it executes the process shown in the flowchart of Figure 2 until the water flow is stopped.

[0046] In this case, whether or not water has been supplied to the hot water supply unit is determined by whether the sum of the flow rates detected by the flow sensors 36 and 48 (water supply flow rate and tank hot water outlet flow rate) is equal to or greater than a first predetermined flow rate (for example, 2.4 liters / minute or more). Furthermore, whether or not water has been supplied to the hot water supply unit is determined by whether the sum of the flow rates detected by the flow sensors 36 and 48 (water supply flow rate and tank hot water outlet flow rate) is equal to or less than a second predetermined flow rate which is smaller than the first predetermined flow rate (for example, 1.8 liters / minute or less).

[0047] Furthermore, if, for example, a flow sensor is provided in the upstream water supply channel 31, or the second hot water supply channel 42, or the inlet channel 51 of the combustion-type heat source unit 50 (the inlet channel 51 upstream of the connection with the bypass channel 55), or the outlet channel 52 of the combustion-type heat source unit 50 (the outlet channel 52 downstream of the connection with the bypass channel 55), then it may be determined whether or not water has been started to flow to the hot water supply target and whether or not the water flow has been stopped based on the flow rate detected by the flow sensor.

[0048] When water is supplied to the hot water supply target section, the control device 70 determines in STEP 1 whether the water temperature in the tank is equal to or above the hot water supply set temperature. In this embodiment, the water temperature in the tank at the time of hot water supply (when water is supplied to the hot water supply target section) is the temperature detected by the temperature sensor 46 of the first hot water supply passage 41 (the temperature of the hot water coming out of the hot water storage tank 11 to the first hot water supply passage 41). However, for example, if a temperature sensor is provided at the top of the hot water storage tank 11, the temperature detected by the temperature sensor may be used as the water temperature in the tank.

[0049] If the result of STEP 1 is positive (i.e., the water temperature in the tank is greater than or equal to the set hot water temperature), the control device 70 performs temperature control of the hot water supply using the mixing valve 45 in STEP 2. In this temperature control, the control device 70 determines a target value for the mixing ratio in the mixing unit 44 so that the water temperature (mixed hot water temperature) detected by the temperature sensor 49 matches or nearly matches the set hot water temperature, and controls the mixing valve 45 according to that target value.

[0050] In this case, the target value of the mixing ratio is calculated using the following equation (1) from the target values ​​of the tank water temperature (temperature of hot water coming out of the hot water storage tank 11) detected by the temperature sensor 46, the water supply temperature (temperature of the hot water supplied to the mixing unit 44) detected by the temperature sensor 37, and the mixed hot water temperature (temperature of the hot water flowing downstream from the mixing unit 44). The hot water set temperature, which is the set value of the target hot water temperature for the hot water supply target unit, is used as the target value of the mixed hot water temperature. Target value of mixing ratio = (Target value of mixed hot water temperature - Tank water temperature) / (Tank water temperature - Water supply temperature) ...(1)

[0051] In this embodiment, the mixing ratio is defined as the ratio of the water supply flow rate (the flow rate of hot water flowing into the mixing section 44 from the bypass water supply channel 33) to the total flow rate of hot water flowing downstream from the mixing section 44 (= water supply flow rate / total flow rate).

[0052] The control device 70 then operates the stepping motor of the mixing valve 45 to achieve the target value of the mixing ratio. Here, the control device 70 has pre-stored correlation data in the form of a calculation formula or table data that shows the relationship between the number of steps that define the rotation angle of the stepping motor of the mixing valve 45 and the mixing ratio. The relationship between the number of steps (rotation angle) of the stepping motor and the mixing ratio shown by this correlation data is such that the mixing ratio increases monotonically as the number of steps increases, as shown in the graph in Figure 3, for example.

[0053] Then, in STEP 2, the control device 70 operates the stepping motor so as to change the number of steps of the stepping motor from the number of steps corresponding to the current mixing ratio to the number of steps corresponding to the target ratio, while referring to the correlation data mentioned above.

[0054] This controls the operation of the mixing valve 45 so that the mixing ratio reaches the target value. Consequently, the temperature control is performed so that the mixed hot water temperature obtained in the mixing unit 44 matches or nearly matches the hot water set temperature. The mixing ratio may also be fine-tuned from the target value according to the deviation between the hot water set temperature and the detected value of the mixed hot water temperature detected by the temperature sensor 49 (to bring the deviation closer to zero).

[0055] On the other hand, if the judgment result in STEP 1 becomes negative due to the hot water storage tank 11 running out of hot water, etc. (i.e., the water temperature in the tank is less than the hot water supply set temperature), the control device 70 will perform temperature control of the hot water supply using the combustion type heat source unit 50 in STEP 3.

[0056] In this temperature control system, the control device 70 determines a target value for the mixing ratio in the mixing unit 44 so that the mixed hot water temperature detected by the temperature sensor 49 matches or nearly matches a predetermined target temperature for the combustion operation of the combustion-type heat source unit 50. The control device then controls the mixing valve 45 according to this target value and starts the combustion operation of the burner 54.

[0057] Then, after the burner 54 starts combustion operation, the control device 70 controls the combustion rate and bypass ratio of the burner 54 so that the temperature of the hot water detected by the temperature sensor 57 (hot water outlet temperature of the heat source unit) matches or nearly matches the hot water set temperature. In this case, the combustion rate of the burner 54 is controlled through the operation control of a fuel supply device and a blower (fan) (not shown), and the bypass ratio is controlled through the operation control of the distribution valve 56.

[0058] Furthermore, a predetermined target temperature for the mixed hot water supply temperature during combustion operation is determined so that the hot water outlet temperature of the heat source unit does not exceed the hot water supply set temperature, assuming that the burner 54 is operated at the minimum combustion rate while the hot water supplied to the combustion heat source unit 50 is temperature-controlled to that temperature. This predetermined target temperature is determined, for example, using a predetermined calculation formula or map based on the tank water temperature (hot water outlet temperature from the hot water storage tank 11) detected by the temperature sensor 46, the water supply temperature detected by the temperature sensor 37, the total flow rate of the flow rates detected by the flow rate sensors 36 and 48, the hot water supply set temperature, etc.

[0059] Then, the target value of the mixing ratio to make the mixed hot water temperature match or nearly match the predetermined target temperature is determined by formula (1), and the mixing valve 45 is controlled according to that target value. In this case, the target temperature for combustion operation is used as the target value of the mixed hot water temperature. The control of the mixing valve 45 according to the target value of the mixing ratio is performed in the same manner as in STEP 2.

[0060] This controls the operation of the mixing valve 45 so that the mixing ratio reaches the target value. Consequently, the temperature is controlled so that the mixed hot water temperature obtained in the mixing unit 44 matches or nearly matches the target temperature for combustion operation. Then, by controlling the combustion rate and bypass ratio of the burner 54 of the combustion-type heat source unit 50, the temperature is controlled so that the hot water outlet temperature of the heat source unit matches or nearly matches the set hot water temperature.

[0061] Next, we will explain the operation while the hot water supply to the target unit is stopped. While the hot water supply is stopped, the control device 70 controls the operation of the mixing valve 45 by executing the process shown in the flowchart of Figure 4. In STEP 11, the control device 70 sequentially determines whether or not the hot water storage tank 11 is out of hot water. If the result of this determination is negative (not out of hot water), in STEP 12, the control device 70 sets the hot water supply set temperature as the target value for the mixed hot water supply temperature.

[0062] Furthermore, if the judgment result in STEP 11 is positive (i.e., there is no hot water left), the control device 70 sets the target temperature for combustion operation as the target value for the mixed hot water temperature in STEP 13. However, in this case, the target temperature for combustion operation is the target temperature determined immediately before the end of the previous combustion hot water supply (hot water supply while the burner 54 of the combustion heat source unit 50 is in combustion operation) (the target temperature for combustion operation determined by the temperature control in STEP 3).

[0063] In STEP 14, following the processing in STEP 12 or 13, the control device 70 determines a target value for the mixing ratio in the mixing unit 44 by calculating equation (1) based on the target value of the mixed hot water temperature determined as described above, the detected value of the water temperature in the tank, and the detected value of the water supply temperature. In this case, the detected value of the water temperature in the tank is the higher of the temperature detected by the temperature sensor 46 of the first hot water supply line 41 and the temperature detected by the temperature sensor 12a on the upper side of the hot water storage tank 11. The detected value of the water supply temperature is the temperature detected by the temperature sensor 37.

[0064] Here, when the hot water supply is stopped, the temperature detected by the temperature sensor 46 may not be the same as or nearly the same as the temperature of the hot water dispensed from the hot water storage tank 11 at the start of hot water supply, due to the influence of the temperature distribution of the hot water in the hot water storage tank 11 and the heating state of the hot water in the hot water storage tank 11 by the heat pump unit 20.

[0065] Furthermore, when hot water supply is stopped, the temperature detected by the temperature sensor 12a on the upper side of the hot water storage tank 11 may not be the same as or nearly the same as the temperature of the hot water dispensed from the hot water storage tank 11 at the start of hot water supply, due to the influence of the temperature distribution of the hot water in the hot water storage tank 11, the air inside the hot water storage tank 11, and the heating state of the hot water in the hot water storage tank 11 by the heat pump unit 20.

[0066] Furthermore, if a temperature lower than the actual temperature is used as the tank water temperature in equation (1), the target value of the mixing ratio will become smaller than the appropriate target value, and consequently, the hot water temperature supplied to the hot water supply target will be higher than the hot water supply set temperature.

[0067] Therefore, in this embodiment, the control device 70 determines the target value of the mixing ratio using the higher of the temperature detected by the temperature sensor 46 and the temperature detected by the temperature sensor 12a as the detected value of the tank water temperature when the hot water supply is stopped. In this embodiment, the temperature sensor 12a corresponds to the first temperature sensor in the present invention, and the temperature sensor 46 corresponds to the second temperature sensor in the present invention.

[0068] Next, in STEP 15, the control device 70 refers to correlation data showing the relationship between the number of steps of the stepping motor of the mixing valve 45 and the mixing ratio, and changes the number of steps of the stepping motor until the absolute value of the difference between the mixing ratio corresponding to the number of steps of the stepping motor and the target value determined in STEP 14 falls within a range of less than or equal to a predetermined threshold th. This controls the mixing ratio in the mixing unit 44 to match or nearly match the target value. Thereafter, the process from STEP 11 is repeated.

[0069] In this embodiment, the operation control of the mixing valve 45 while the hot water supply is stopped is performed as described above. Therefore, regardless of changes in the water temperature in the tank or changes in the hot water supply setting temperature while the hot water supply is stopped, the operating state of the mixing valve 45 (number of steps of the stepping motor) immediately before the start of hot water supply to the target area will be in an operating state that matches or nearly matches the operating state corresponding to the mixing ratio required at the start of hot water supply.

[0070] Therefore, the mixing ratio can be quickly controlled to the target value immediately after the start of hot water supply to the hot water supply target. Consequently, the temperature of the hot water supplied downstream from the mixing unit 44 can be controlled to an appropriate target temperature for supplying hot water at the set hot water temperature to the hot water supply target.

[0071] Furthermore, when the hot water supply is stopped, the higher of the temperatures detected by temperature sensors 46 and 12a is used as the detected value of the water temperature inside the tank to determine the target value of the mixing ratio. This makes it possible to avoid, as much as possible, the mixed hot water temperature obtained in the mixing unit 44 being higher than the target temperature.

[0072] It should be noted that the present invention is not limited to the embodiments described above, and other embodiments may be adopted. Several other embodiments are given below as examples. In the above embodiment, the hot water supply circuit 40 is configured such that when hot water is supplied to the hot water supply target, the hot water supplied to the hot water supply target always passes through the combustion type heat source 50. However, it may also be provided with a bypass flow path that bypasses the combustion type heat source 50 from the second hot water supply passage 42 and flows the hot water to the third hot water supply passage 43.

[0073] Furthermore, in the above embodiment, when hot water is supplied or when hot water is stopped, the value detected by the temperature sensor 46 installed near the upstream end of the first hot water supply line 41 was used as the detected value of the water temperature inside the tank, which corresponds to the temperature detected by the second temperature sensor in the present invention. However, for example, if a temperature sensor is provided at the top of the hot water storage tank 11, the temperature detected by the temperature sensor may be used as the detected value of the water temperature inside the tank instead of the value detected by the temperature sensor 46.

[0074] Furthermore, in the above embodiment, when the hot water supply is stopped, the higher of the temperature detected by the temperature sensor 46 and the temperature detected by the temperature sensor 12a was used as the detected value of the water temperature inside the tank for determining the target value of the mixing ratio. However, it is also possible to determine the target value of the mixing ratio by using, for example, only the temperature detected by the temperature sensor 46 as the detected value of the water temperature inside the tank, or by using only the temperature detected by the temperature sensor located at the top of the hot water storage tank 11 as the detected value of the water temperature inside the tank.

[0075] Furthermore, in the above embodiment, a heat pump unit 20 was used as a heating device for heating the hot water in the hot water storage tank 11, but the heating device may be of other types. For example, the heating device may be a combustion-type heating device, or a heating device that uses a fuel cell or the like as a heat source. Also, in the above embodiment, a hot water storage system 1 equipped with a combustion-type heat source 50 was exemplified, but the hot water storage system in the present invention may be a system that does not have a combustion-type heat source. [Explanation of Symbols]

[0076] 1...Storage-type hot water supply system, 11...Storage tank, 20...Heat pump unit (heating device), 44...Mixing unit, 70...Control device, 12a...Temperature sensor (first temperature sensor), 46...Temperature sensor (second temperature sensor).

Claims

[Claim 1] A storage-type hot water supply system comprising: a hot water storage tank for storing hot water heated by a heating device; a mixing unit connected to the hot water storage tank, which is the hot water discharged from the hot water storage tank, and which can mix hot water supply water with the hot water supply water and adjust the mixing ratio of the hot water discharged from the hot water storage tank and the hot water supply water; and a control device having a function to control the mixing ratio, wherein the system is configured to supply hot water from the hot water storage tank to a target hot water supply unit via the mixing unit, and the control device has a function to control the mixing ratio so that the temperature of the hot water obtained in the mixing unit reaches a predetermined target temperature when supplying hot water to the target hot water supply unit, The control device is configured to sequentially perform the following steps while the hot water supply to the hot water supply target unit is stopped: acquire an observed value of the water temperature in the hot water storage tank and an observed value of the water supply temperature, and then, based on the observed value of the water temperature in the tank, the observed value of the water supply temperature, and the predetermined target temperature, determine a target value for the mixing ratio so that the temperature of the water obtained in the mixing unit when the hot water supply to the hot water supply target unit is started becomes the predetermined target temperature; and control the mixing ratio to the determined target value. Furthermore, the system includes a first temperature sensor mounted on the upper side of the hot water storage tank and a second temperature sensor located near the upstream end of the flow path connecting the mixing unit to the hot water storage tank or at the top of the hot water storage tank, as temperature sensors for detecting the temperature of the hot water in the hot water storage tank. The mixing unit is connected to the hot water storage tank so that hot water from the hot water storage tank is supplied from the top of the hot water storage tank. The control device is further configured to (i) determine a target value for the mixing ratio using the higher of the temperature detected by the first temperature sensor and the temperature detected by the second temperature sensor as the observed value of the water temperature in the tank when the supply of hot water to the target unit is stopped, and (ii) control the mixing ratio using the temperature detected by the second temperature sensor, rather than using the temperature detected by the first temperature sensor, when supplying hot water to the target unit.

Images