Hot water supply system

Abstract

In a hot water supply system equipped with a hot and cold water circulation circuit, the storage capacity of the hot water storage tank and the heating capacity of the heat source are both kept in a balanced manner, thereby improving energy efficiency while making it easier to secure installation space and fitting. [Solution] The system includes an open-type hot water storage tank 40 and a hot water supply mode switching means 62. The hot water supply modes include a closed-type hot water supply mode in which the hot water circulation circuit 10 is sealed and the hot water heated by the heat source unit 1 is circulated and supplied to the hot water supply unit 2 by the circulation pump 20, and an open-type hot water supply mode in which the hot water circulation circuit 10 is open and the hot water heated by the heat source unit 1 is temporarily stored in the hot water storage tank 40 and then circulated and supplied to the hot water supply unit 2. The hot water storage tank 40 is an elevated hot water storage tank 40 installed at a higher position than the hot water supply unit 2, and the hot water supply mode switching means 62 closes the gravity supply pipeline 46 connecting the elevated hot water storage tank 40 and the hot water circulation circuit 10 in the closed-type hot water supply mode and opens it in the open-type hot water supply mode.

Description

Technical Field

[0001] The present invention relates to a hot water supply system provided with a hot water circulation circuit for circulating hot water between a heat source section and a hot water supply section.

Background Art

[0002] As a hot water supply system provided with a hot water circulation circuit for circulating hot water between a heat source section for heating hot water and a hot water supply section for consuming hot water, those described in Patent Document 1 and Patent Document 2 are known. The hot water supply system described in Patent Document 1 is a closed-type hot water supply system in which the hot water circulation circuit is in a closed state not open to the atmosphere during operation. In such a closed-type hot water supply system, the hot water heated in the heat source section is circulated and supplied to the hot water supply section by a circulation pump provided in the closed hot water circulation circuit. Therefore, the conveyance power of the hot water in the circulation pump only needs to cover the pressure loss in the hot water circulation circuit, and the conveyance power can be suppressed to improve energy saving. On the other hand, the hot water supply system described in Patent Document 2 is an open-type hot water supply system in which the hot water circulation circuit is in an open state through an open-type elevated hot water storage tank during operation. In such an open-type hot water supply system, the hot water heated in the heat source section is once stored in the hot water storage tank and then supplied to the hot water supply section. Therefore, the heating of the hot water by the heat source section can be leveled and the capacity of the heat source section can be suppressed. Further, in the hot water supply system described in Patent Document 2, by using an elevated hot water storage tank installed at a higher position than the hot water supply section, the hot water stored in the hot water storage tank is supplied to the hot water supply section by its own weight without using a pump.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Patent Document 2

Summary of the Invention

Problems to be Solved by the Invention

[0004] However, in closed-type hot water supply systems, a hot water storage tank is generally not installed, or only a relatively small, closed-type hot water storage tank is installed. Therefore, if the heating capacity of the heat source is set to a larger level to account for situations where the hot water load is high during peak periods that last for relatively long periods, or when the hot water load during such peak periods is very high, a deterioration in thermal efficiency can become a problem. On the other hand, in open-type hot water supply systems, an open-type hot water storage tank with a relatively large storage capacity that can handle all hot water loads is generally installed, which can sometimes pose problems in terms of installation space and fitting. In light of these circumstances, the main objective of the present invention is to provide a technology that can improve energy efficiency in a hot water supply system equipped with a hot water circulation circuit that circulates hot water between a heat source and a hot water supply unit, while maintaining a good balance between the hot water storage capacity of the storage tank and the heating capacity of the heat source unit, thereby facilitating the securing of installation space and fitting. [Means for solving the problem]

[0005] The first characteristic configuration of the present invention is a hot water supply system equipped with a hot water circulation circuit that circulates hot water between a heat source and a hot water supply unit, The system comprises an open-type hot water storage tank capable of storing hot water heated by the heat source unit, and a hot water supply mode switching means capable of switching the hot water supply mode in a manner that changes the state of the hot water circulation circuit. The aforementioned hot water supply modes include a sealed hot water supply mode and an open hot water supply mode. The sealed hot water supply mode is a hot water supply mode in which the state of the hot water circulation circuit is in a sealed state, separated from the hot water storage tank, and the hot water heated in the heat source unit is circulated and supplied to the hot water supply unit by a circulation pump provided in the hot water circulation circuit. The open-type hot water supply mode is a hot water supply mode in which the state of the hot water circulation circuit is in an open state connected to the hot water storage tank, and the hot water heated in the heat source unit is temporarily stored in the hot water storage tank and supplied to the hot water supply unit. The hot water storage tank is an elevated hot water storage tank installed at a higher position than the hot water supply unit. The elevated hot water storage tank and the hot water circulation circuit are connected by a gravity-fed supply pipeline, The hot water supply mode switching means closes the self-weight supply pipeline in the closed hot water supply mode and opens the self-weight supply pipeline in the open hot water supply mode.

[0006] According to this configuration, an open-type elevated hot water storage tank is configured to be connectable to and disconnectable from the hot water circulation circuit, and the hot water supply mode switching means can be used to switch between a closed-type hot water supply mode and an open-type hot water supply mode by changing the connection status of the elevated hot water storage tank as the state of the hot water circulation circuit. By switching the hot water supply mode to a sealed hot water supply mode using the hot water supply mode switching means, the hot water heated in the heat source unit is circulated to the hot water supply unit through a sealed hot water circulation circuit by a circulation pump installed in the hot water circulation circuit. As a result, the power required to transport the hot water by the circulation pump only needs to cover the pressure loss in the hot water circulation circuit, thereby reducing the transport power and improving energy efficiency. On the other hand, by switching the hot water supply mode to the open-type hot water supply mode using the hot water supply mode switching means, the hot water heated by the heat source is temporarily stored in the elevated hot water storage tank and then supplied to the hot water supply unit. This allows for leveling out the heating of the hot water by the heat source and suppressing the capacity of the heat source while still being able to handle relatively large hot water loads during peak times. Furthermore, in the open-type hot water supply mode, the hot water stored in the elevated hot water storage tank is supplied to the hot water supply unit of the hot water circulation circuit by gravity through the gravity supply pipeline. This allows for the omission or minimization of the pump required to supply the hot water stored in the elevated hot water storage tank to the hot water supply unit, thereby improving energy efficiency. Therefore, the present invention provides a technology that enables improved energy efficiency in a hot water supply system equipped with a hot water circulation circuit that circulates hot water between a heat source and a hot water supply unit, while maintaining a good balance between the storage capacity of the elevated hot water storage tank and the heating capacity of the heat source unit, thereby facilitating the securing of installation space and fitting.

[0007] A second characteristic configuration of the present invention is that, in the hot water circulation circuit, the circulation pump is provided on the primary side of the heat source unit, and a water supply pipeline is connected between the heat source unit and the circulation pump to supply water at a predetermined set supply water pressure. The hot water supply mode switching means operates the circulation pump in both the sealed hot water supply mode and the open hot water supply mode, respectively.

[0008] In this configuration, in open-type hot water supply mode, the pressure on the primary side of the heat source in the hot water circulation circuit, between the heat source and the circulation pump located on its primary side, is maintained at a relatively high set supply water pressure because water is supplied from the water supply pipe while hot water is being discharged from the circulation pump. Therefore, this pressure on the primary side of the heat source can be effectively utilized as power to pump the hot water heated in the heat source to the elevated hot water storage tank.

[0009] A third characteristic feature of the present invention is that it includes a control means that controls the operation of the hot water supply mode switching means based on the hot water supply load in the hot water supply unit, and automatically switches the hot water supply mode between the sealed hot water supply mode and the open hot water supply mode.

[0010] With this configuration, the control means can automatically switch between a closed-type hot water supply mode and an open-type hot water supply mode based on the hot water load. That is, during normal times when the hot water load is relatively small, the control means automatically switches the hot water supply mode to the closed-type mode. This enables operation that prioritizes energy saving. On the other hand, during peak times when the hot water load is relatively large, the control means automatically switches the hot water supply mode to the open-type mode. This allows the system to handle the large hot water load by storing the hot water heated by the heat source in the elevated storage tank in advance, while also leveling out the heating of the hot water by the heat source and suppressing the capacity of the heat source.

[0011] A fourth feature configuration of the present invention is the inclusion of a water supply amount detection means for detecting the amount of water supplied to the hot and cold water circulation circuit, The control means changes the hot water supply mode to the open-type hot water supply mode when the amount of replenishment water detected by the replenishment water amount detection means exceeds a predetermined set amount of replenishment water while the hot water supply mode is the closed-type hot water supply mode.

[0012] With this configuration, during normal operation when the hot water supply mode is set to closed-type hot water supply mode, the amount of replenishment water supplied to the hot water circulation circuit increases as the hot water load increases. If this amount of replenishment water exceeds a predetermined set amount, the control means automatically changes the hot water supply mode to open-type hot water supply mode, thus enabling a rapid response to relatively large hot water loads.

[0013] A fifth feature of the present invention is the inclusion of a water level detection means for detecting the water level in the elevated hot water storage tank, The control means changes the hot water supply mode to the closed-type hot water supply mode when the water level detected by the water level detection means exceeds a predetermined set water level while the hot water supply mode is the open-type hot water supply mode.

[0014] With this configuration, during peak hours when the hot water supply mode is set to open-type hot water supply mode, if the water level in the elevated hot water storage tank rises as the hot water supply load decreases and exceeds a predetermined set water level, the control means automatically changes the hot water supply mode to closed-type hot water supply mode, allowing for a quick response to relatively small hot water supply loads.

[0015] A sixth feature of the present invention is that, in addition to the hot water circulation circuit, it is provided with a tank inlet pipeline that guides the hot water heated in the heat source unit to the elevated hot water storage tank, and the destination of the hot water heated in the heat source unit can be selectively set between the hot water circulation circuit and the tank inlet pipeline. The hot water supply mode switching means selectively sets the destination of the hot water heated by the heat source to the hot water circulation circuit in the closed-type hot water supply mode, and selectively sets the destination of the hot water heated by the heat source to the tank inlet pipeline in the open-type hot water supply mode.

[0016] According to this configuration, it is provided with a tank inlet pipeline that guides the hot water heated by the heat source unit to the elevated hot water storage tank. For example, in a form where one of the connection parts of the hot water circulation circuit and the tank inlet pipeline to the heat source unit is opened and the other side is closed, the supply destination of the hot water heated by the heat source unit can be selectively set between the hot water circulation circuit and the tank inlet pipeline. And in the closed hot water supply mode, after the self-weight supply pipeline is closed, the supply destination of the hot water heated by the heat source unit is selectively set to the hot water circulation circuit, so that the state of the hot water circulation circuit is separated from the elevated hot water storage tank and in a closed state, and the hot water heated by the heat source unit can be circulated and supplied to the hot water supply part by the circulation pump provided in the hot water circulation circuit. On the other hand, in the open hot water supply mode, after the self-weight supply pipeline is opened, the supply destination of the hot water heated by the heat source unit is selectively set to the tank inlet pipeline, so that the state of the hot water circulation circuit is in an open state connected to the elevated hot water storage tank. The hot water heated by the heat source unit is temporarily stored in the elevated hot water storage tank through the tank inlet pipeline, and the hot water stored in the elevated hot water storage tank can be supplied to the hot water supply part of the hot water circulation circuit by self-weight through the self-weight supply pipeline.

Brief Description of the Drawings

[0017] [Figure 1] Figure showing the schematic configuration of the hot water supply system in the first embodiment and the operating state in the closed hot water supply mode [Figure 2] Figure showing the schematic configuration of the hot water supply system in the first embodiment and the operating state in the open hot water supply mode [Figure 3] Figure showing the schematic configuration of the hot water supply system in the second embodiment and the operating state in the closed hot water supply mode [Figure 4] Figure showing the schematic configuration of the hot water supply system in the second embodiment and the operating state in the open hot water supply mode (high water level state) [Figure 5] Figure showing the schematic configuration of the hot water supply system in the second embodiment and the operating state in the open hot water supply mode (low water level state) [Figure 6] Figure showing the schematic configuration of the hot water supply system in the third embodiment and the operating state in the closed hot water supply mode [Figure 7]Diagram showing the schematic configuration of the hot water supply system of the third embodiment and the operating state of the open-type hot water supply mode. [Figure 8] Diagram showing the processing flow for changing the hot water supply mode. [Modes for carrying out the invention]

[0018] An embodiment of the hot water supply system according to the present invention will be described with reference to the drawings. In Figures 1 to 7, open valves are shown in white, closed valves are shown in black, pipes through which hot and cold water flows are shown with solid lines, and pipes through which hot and cold water does not flow are shown with dashed lines.

[0019] [First Embodiment] The hot water supply system of the first embodiment will be described with reference to Figures 1, 2, and 8. As shown in Figures 1 and 2, the hot water supply system of this embodiment is configured to include a hot water circulation circuit 10 that circulates hot water between a heat source unit 1 such as a boiler and a hot water supply unit 2 such as a hot water tap, a hot water heating device, or a bathtub. The hot water supply system of this embodiment is also provided with a control device 60 for controlling the operation of various devices, and this control device 60 functions as a hot water load acquisition means 61, a hot water mode switching means 62, a control means 63, etc., which will be described later, by executing a predetermined computer program.

[0020] The hot water supply system of this embodiment is equipped with an open-type hot water storage tank 40 capable of storing hot water heated by the heat source unit 1, and a hot water supply mode switching means 62 that can switch the hot water supply mode by changing the state of the hot water circulation circuit 10. The system is designed to improve energy efficiency while maintaining a good balance between the hot water storage capacity of the storage tank 40 and the heating capacity of the heat source unit 1, making it easy to secure installation space and fit. The details of this system will be explained below.

[0021] The hot and cold water circulation circuit 10 includes a supply pipe 11 that supplies hot and cold water heated by the heat source unit 1 to the hot water supply unit 2, and a return pipe 12 that returns the hot and cold water that has passed through the hot water supply unit 2 to the heat source unit 1. An open-type hot water storage tank 40 capable of storing hot and cold water heated by the heat source unit 1 is provided on the supply pipe 11 side. On the return pipe 12 side, multiple circulation pumps 20 connected in parallel are provided. The hot and cold water circulation circuit 10 is also equipped with a pressure relief valve 15 to mitigate excessive pressure increases and a pressure tank 16 to mitigate sudden pressure fluctuations.

[0022] The specific configuration will be described later, but the open-type hot water storage tank 40 is configured to be connectable to and disconnected from the hot water circulation circuit 10. With this configuration, the state of the hot water circulation circuit 10 can be switched between a sealed state disconnected from the hot water storage tank 40 (the state shown in Figure 1) and an open state connected to the hot water storage tank 40 (the state shown in Figure 2). Furthermore, the system is configured to circulate hot water through the hot water circulation circuit 10 by operating the circulation pump 20. The hot water supply mode switching means 62 is configured to switch the hot water supply mode between a closed-type hot water supply mode (see Figure 1) and an open-type hot water supply mode (see Figure 2), which will be described later, by changing the connection state of the hot water circulation circuit 10 and the operating state of the hot water storage tank 40 and the circulation pump 20.

[0023] In other words, in the sealed hot water supply mode described above, as shown in Figure 1, the state of the hot water circulation circuit 10 is set to the sealed state, and the hot water heated in the heat source unit 1 is not stored in the hot water storage tank 40 but is circulated and supplied to the hot water supply unit 2 by the operation of the circulation pump 20 provided in the hot water circulation circuit 10. Furthermore, when the hot water supply mode is set to the sealed hot water supply mode, the power required to transport the hot water in the circulation pump 20 only needs to cover the pressure loss in the hot water circulation circuit 10, thus reducing the transport power and improving energy efficiency.

[0024] On the other hand, in the open-type hot water supply mode described above, as shown in Figure 2, the state of the hot water circulation circuit 10 is set to the open state, and the hot water heated by the heat source unit 1 is temporarily stored in the hot water storage tank 40 and then supplied to the hot water supply unit 2. When the hot water supply mode is set to the open-type hot water supply mode, the heating of the hot water by the heat source unit 1 is leveled out, and the capacity of the heat source unit 1 is suppressed, while still being able to handle relatively large hot water supply loads during peak times.

[0025] Next, we will explain the specific configuration for switching the hot water supply mode using the hot water supply mode switching means 62. As shown in Figures 1 and 2, the hot water storage tank 40 is configured as an elevated hot water storage tank 40 installed at a higher position than the hot water supply unit 2. Furthermore, a gravity-fed pipeline 46 connecting the elevated hot water storage tank 40 and the hot and cold water circulation circuit 10 is provided as a pipeline connecting the bottom of the elevated hot water storage tank 40 to the end of the supply pipeline 11 opposite to the heat source section 1. The gravity-fed pipeline 46 is equipped with a backflow prevention valve 47 that allows the flow of hot and cold water from the elevated hot water storage tank 40 to the hot and cold water circulation circuit 10, and prevents the flow of hot and cold water from the hot and cold water circulation circuit 10 to the elevated hot water storage tank 40.

[0026] In addition to the hot and cold water circulation circuit 10, a tank inlet pipeline 43 is provided to guide the hot and cold water heated by the heat source unit 1 to the elevated hot water storage tank 40. This pipeline connects the secondary side (supply pipeline 11 side) of the heat source unit 1 in the hot and cold water circulation circuit 10 to the elevated hot water storage tank 40. Furthermore, a hot and cold water supply destination switching valve 45 is provided at the connection point of the tank inlet pipeline 43 to the secondary side of the heat source unit 1 in the hot and cold water circulation circuit 10, allowing the supply destination of the hot and cold water heated by the heat source unit 1 to be selectively set between the supply pipeline 11 side and the tank inlet pipeline 43 side. In this embodiment, the hot and cold water supply destination switching valve 45 is configured as a three-way switching valve that can selectively open the connection to the supply line 11 and the connection to the tank inlet line 43 while keeping the connection to the secondary side of the heat source unit 1 open at all times. However, it is also possible to configure the system so that the destination of the hot and cold water heated by the heat source unit 1 can be selectively set between the supply line 11 and the tank inlet line 43 by providing on / off valves to each of the supply line 11 and the tank inlet line 43 and selectively opening them.

[0027] In other words, in the sealed hot water supply mode shown in Figure 1, the hot water supply mode switching means 62 sets the state of the hot water supply destination switching valve 45 to a state where the hot water heated by the heat source unit 1 is supplied to the supply line 11 of the hot water circulation circuit 10. That is, the supply line 11 side of the hot water supply destination switching valve 45 is opened, and the tank inlet line 43 side of the hot water supply destination switching valve 45 is closed. Furthermore, as the pressure in the sealed hot water circulation circuit 10 rises, the backflow prevention valve 47 is closed, and the gravity supply line 46 is closed. As a result, the hot water heated in the heat source unit 1 is supplied to the hot water supply unit 2 side through the supply pipe 11 without being stored in the elevated hot water storage tank 40. The hot water that has passed through the hot water supply unit 2 side is returned to the heat source unit 1 by passing through the operating circulation pump 20 installed in the return pipe 12 of the hot water circulation circuit 10.

[0028] On the other hand, in the open-type hot water supply mode shown in Figure 2, the hot water supply mode switching means 62 sets the state of the hot water supply destination switching valve 45 to a state where the hot water heated by the heat source unit 1 is supplied to the tank inlet pipe 43. That is, the supply pipe 11 side of the hot water supply destination switching valve 45 is closed, and the tank inlet pipe 43 side of the hot water supply destination switching valve 45 is opened. Furthermore, as the pressure in the open hot water circulation circuit 10 decreases, the backflow prevention valve 47 opens and the gravity supply pipe 46 is opened. The hot water heated in the heat source unit 1 is then supplied to the elevated hot water storage tank 40 via the tank inlet pipeline 43 and stored there. The hot water stored in the elevated hot water storage tank 40 is then supplied to the hot water supply unit 2 side of the hot water circulation circuit 10 via the gravity supply pipeline 46, due to the weight of the hot water stored in the elevated hot water storage tank 40. Thus, the power required to supply the hot water stored in the elevated hot water storage tank 40 to the hot water supply unit 2 is reduced, improving energy efficiency. In addition, any hot water that is not supplied to the hot water supply unit 2 is returned to the heat source unit 1 by passing through the operating circulation pump 20 located in the return pipeline 12 of the hot water circulation circuit 10.

[0029] In the return pipe 12 connected to the primary side of the heat source unit 1, a water supply pipe 50 is connected to the primary side portion 12A of the heat source unit, between the heat source unit 1 and the circulation pump 20 provided in the return pipe 12 on its primary side, to supply water at a predetermined set supply water pressure. The water supply pipe 50 is also equipped with a flow sensor 51 (an example of a supply water amount detection means) that detects the amount of supply water supplied from the water supply pipe 50 to the primary side portion 12A of the heat source unit. In the open-type hot water supply mode shown in Figure 2, water is supplied from the water supply pipe 50 to the primary side portion 12A of the heat source unit 1 and the circulation pump 20 located on its primary side in the hot water circulation circuit 10, while hot water is being discharged from the circulation pump 20. This ensures that the pressure in the primary side portion 12A of the heat source unit is maintained at a relatively high set supply water pressure. This pressure in the primary side portion 12A of the heat source unit is then effectively used as power to pump the hot water heated by the heat source unit 1 to the elevated hot water storage tank 40.

[0030] The elevated hot water storage tank 40 is equipped with a water level sensor 41 (an example of a water level detection means) for detecting the water level of the hot water stored in the elevated hot water storage tank 40. In the open-type hot water supply mode, the amount of hot water flowing into the elevated hot water storage tank 40 is adjusted by adjusting the opening of the flow control valve 44 provided in the tank inlet pipeline 43, so that the water level in the elevated hot water storage tank 40, as detected by the water level sensor 41, is maintained at a desired water level.

[0031] [Automatic hot water supply mode switching control] Next, I will explain the automatic hot water mode switching control. The hot water supply system of this embodiment is provided with a hot water load acquisition means 61 and a control means 63 for automatically switching the hot water supply mode using the hot water supply mode switching means 62 as described above.

[0032] The hot water load acquisition means 61 is a means for acquiring the hot water load of the hot water supply unit 2. Then, the control means 63 controls the operation of the hot water mode switching means 62 based on the hot water load acquired by the hot water load acquisition means 61, and performs automatic hot water mode switching control to automatically switch the hot water mode between the sealed hot water mode (see Figure 1) and the open hot water mode (see Figure 2). In other words, the hot water load acquisition means 61 determines that it is a normal period if the hot water load itself or its moving average value is relatively small, and determines that it is a peak period if the hot water load itself or its moving average value is relatively large. Although such determinations can be made at all times, performing them at regular intervals, such as when weekdays and holidays change, or when off-peak and peak seasons change at accommodation facilities, can avoid excessive switching of the hot water mode.

[0033] Under normal conditions, the hot water supply mode is set to the sealed hot water supply mode (see Figure 1). In this way, during normal operation when the hot water supply load is relatively small, the control means 63 automatically sets the hot water supply mode to the sealed hot water supply mode (see Figure 1), thus achieving operation that prioritizes energy saving.

[0034] On the other hand, during peak times, the hot water supply mode is set to open-type hot water supply mode (see Figure 2). In this way, during peak times when the hot water supply load is relatively large, the control means 63 automatically sets the hot water supply mode to open-type hot water supply mode (see Figure 2). This allows the hot water heated by the heat source unit 1 to be stored in the elevated hot water storage tank 40 in advance, making it possible to cope with the large hot water supply load, and also equalizing the heating of the hot water by the heat source unit 1, thereby suppressing the capacity of the heat source unit 1.

[0035] Various known methods can be used to acquire the hot water load using the hot water load acquisition means 61. For example, the amount of heat consumed in the hot water supply unit 2 can be determined by multiplying the temperature difference between the hot water supplied to the hot water supply unit 2 and the temperature of the hot water returning to the heat source unit 1 in the hot water circulation circuit 10 by the flow rate of these hot waters, and this amount of heat consumed can be acquired as the hot water load. Alternatively, instead of directly determining the hot water load, the hot water load of the hot water supply unit 2 can be predicted from other information related to the heat consumption state of the hot water supply unit 2. For example, if the facility where the hot water supply system of this embodiment is installed is an accommodation facility such as a hotel with multiple guest rooms that serve as hot water supply units 2, the hot water load in each guest room can be predicted based on the occupancy status and reservation status of each guest room. In this embodiment, the automatic hot water mode switching control described above was performed, but this automatic hot water mode switching control may be omitted, and the system may be configured to switch the hot water mode manually, for example, by a facility manager.

[0036] Furthermore, the control means 63 is configured to perform automatic hot water mode switching control by acquiring the amount of replenishment water detected by the flow sensor 51 and the water level detected by the water level sensor 41, and then performing a hot water mode change process to change the hot water mode based on these amounts of replenishment water and water level. The details of the hot water mode change process will be explained below with reference to the flow chart in Figure 8.

[0037] First, it is determined whether the current hot water supply mode is a sealed hot water supply mode or an open hot water supply mode (step #10 in Figure 8). When it is determined that the current hot water supply mode is a sealed hot water supply mode, the amount of replenishment water detected by the flow sensor 51 is monitored to see if it exceeds a predetermined set replenishment water amount (step #11 in Figure 8). If the amount of replenishment water exceeds a predetermined set replenishment water amount while operating in sealed hot water supply mode (Yes in step #11 in Figure 8), it is determined that the hot water supply load has increased to a relatively large level, and in order to cope with the relatively large hot water supply load, the hot water supply mode is changed from the current sealed hot water supply mode to an open hot water supply mode (step #12 in Figure 8).

[0038] On the other hand, when it is determined that the current hot water supply mode is open-type hot water supply mode, the water level of the elevated hot water storage tank 40 detected by the water level sensor 41 is monitored to see if it exceeds a predetermined set water level (step #13 in Figure 8). If the water level of the elevated hot water storage tank 40 exceeds the predetermined set water level while operating in open-type hot water supply mode (Yes in step #13 in Figure 8), the hot water supply load is considered to have decreased to a relatively small level, and the hot water supply mode is changed from the current open-type hot water supply mode to a closed-type hot water supply mode to accommodate the relatively small hot water supply load (step #14 in Figure 8). In this embodiment, the hot water mode change process described above was performed, but this hot water mode change process may be omitted or modified as appropriate.

[0039] [Second Embodiment] The hot water supply system of the second embodiment will be described with reference to Figures 3, 4, and 5. In the following description, components similar to those in the first embodiment described above will be denoted by the same reference numerals in the drawings, and detailed explanations may be omitted.

[0040] The hot water supply system of this embodiment eliminates the tank inlet pipeline 43 (see Figure 2) that was provided in the hot water supply system of the first embodiment described above, and the hot water supply mode switching means 62 is configured to supply hot water heated in the heat source unit 1 to the elevated hot water storage tank 40 through the hot water circulation circuit 10 and the gravity supply pipeline 46 in the open hot water supply mode.

[0041] In other words, the self-weight supply pipeline 46 is provided with an on / off valve 48 that can interrupt the self-weight supply pipeline 46 and interrupt the flow of hot water through the self-weight supply pipeline 46, instead of the backflow prevention valve 47 (see Figure 2) that was provided in the hot water supply system of the first embodiment described above.

[0042] In the sealed hot water supply mode, as shown in Figure 3, the on / off valve 48 is closed by the hot water supply mode switching means 62, thereby closing the self-weight supply pipeline 46. As a result, the hot water heated in the heat source unit 1 is supplied to the hot water supply unit 2 side through the supply pipe 11 without being stored in the elevated hot water storage tank 40. The hot water that has passed through the hot water supply unit 2 side is returned to the heat source unit 1 by passing through the operating circulation pump 20 installed in the return pipe 12 of the hot water circulation circuit 10.

[0043] On the other hand, in the open-type hot water supply mode, as shown in Figures 4 and 5, the on-off valve 48 is opened by the hot water supply mode switching means 62, and the gravity supply pipeline 46 is opened. As shown in Figure 5, the hot water heated in the heat source unit 1 is supplied to the elevated hot water storage tank 40 through the supply line 11 and the gravity supply line 46 of the hot water circulation circuit 10 and stored there. Then, as shown in Figure 4, the hot water stored in the elevated hot water storage tank 40 is supplied to the hot water supply unit 2 side of the hot water circulation circuit 10 through the gravity supply line 46 by the weight of the hot water stored in the elevated hot water storage tank 40. Thus, the power required to supply the hot water stored in the elevated hot water storage tank 40 to the hot water supply unit 2 is reduced, improving energy efficiency. In addition, the hot water that was not supplied to the hot water supply unit 2 passes through the operating circulation pump 20 located in the return line 12 of the hot water circulation circuit 10 and is returned to the heat source unit 1.

[0044] Furthermore, the control means 63 is configured to switch the inflow and outflow state of hot water to and from the gravity supply pipeline 46 in the elevated hot water storage tank 40 based on the water level of the elevated hot water storage tank 40 detected by the water level sensor 41 when operating in the open-type hot water supply mode. Specifically, the water supply pipeline 50 is equipped with a pressure regulating valve 52 that can adjust the supply water pressure to the hot and cold water circulation circuit 10 (primary side portion 12A of the heat source). When the supply water pressure is set to a lower set pressure or below by the pressure regulating valve 52, the internal pressure of the hot and cold water circulation circuit 10 decreases, as shown in Figure 4, resulting in a hot and cold water outflow state where hot and cold water flows from the elevated hot water storage tank 40 to the hot and cold water circulation circuit 10 through the gravity supply pipeline 46. On the other hand, when the supply water pressure is set to a higher set pressure or above by the pressure regulating valve 52, the internal pressure of the hot and cold water circulation circuit 10 increases, as shown in Figure 5, resulting in a hot and cold water inflow state where hot and cold water flows from the hot and cold water circulation circuit 10 to the elevated hot water storage tank 40 through the gravity supply pipeline 46.

[0045] Then, as shown in Figure 4, if the water level in the elevated hot water storage tank 40 detected by the water level sensor 41 is relatively high, for example, above the set water level, the control means 63 lowers the replenishment water pressure using the pressure regulating valve 52 so that the hot water outflow state described above occurs. In this case, hot water is supplied to the hot water supply unit 2 from the heat source unit 1 and the elevated hot water storage tank 40. On the other hand, as shown in Figure 5, if the water level in the elevated hot water storage tank 40 detected by the water level sensor 41 is relatively low, for example below the set water level, the control means 63 sets the replenishment water pressure higher using the pressure regulating valve 52 so that the hot water inflow state described above occurs. Then, hot water is supplied to the hot water supply unit 2 from the heat source unit 1, and the hot water heated by the heat source unit 1, excluding the portion supplied to the hot water supply unit 2, is supplied to the elevated hot water storage tank 40 and stored there.

[0046] [Third Embodiment] The hot water supply system of the third embodiment will be described with reference to Figures 6 and 7. In the following description, components similar to those in the first embodiment described above will be denoted by the same reference numerals in the drawings, and detailed explanations may be omitted.

[0047] In the hot water supply system of this embodiment, the hot water supply section 2 is provided with a lower-level hot water supply section 2B and a higher-level hot water supply section 2A located at a higher position than the lower-level hot water supply section 2B. That is, the hot water circulation circuit 10 has, in order from the heat source section 1 side along the direction of hot water flow, a lower-level circuit section 10B to which the lower-level hot water supply section 2B is connected and a higher-level circuit section 10A to which the higher-level hot water supply section 2A is connected. The hot and cold water circulation circuit 10 is provided with high-side separation valves 13 and 14 that can separate the high-side circuit portion 10A from the low-side circuit portion 10B by closing. Specifically, a first high-side separation valve 13, configured as an on-off valve, is provided at the boundary between the low-side circuit portion 10B and the high-side circuit portion 10A in the supply pipe 11, and a second high-side separation valve 14, configured as an on-off valve, is provided at the connection point of the high-side circuit portion 10A to the return pipe 12. By closing these high-side separation valves 13 and 14, the high-side circuit portion 10A is separated from the low-side circuit portion 10B while maintaining the connection state between the low-side circuit portion 10B and the heat source unit 1.

[0048] The self-weight supply pipeline 46 is connected to the lower-side circuit portion 10B of the hot and cold water circulation circuit 10. Furthermore, as a means for supplying hot water stored in the elevated hot water storage tank 40 to the elevated circuit section 10A, the system includes an elevated hot water supply pipe 31 that guides hot water taken from the bottom of the elevated hot water storage tank 40 to the elevated circuit section 10A, an elevated hot water return pipe 32 that guides hot water taken from near the connection point between the elevated hot water supply pipe 31 and the second elevated separation valve 14 back to the elevated hot water storage tank 40, a pressure pump 30 provided in the elevated hot water supply pipe 31 that sends hot water from the elevated hot water storage tank 40 side to the elevated circuit section 10A side, and an on / off valve 33 that can open and close the elevated hot water return pipe 32.

[0049] In the sealed hot water supply mode, as shown in Figure 6, the hot water supply mode switching means 62 opens the high-side separation valves 13 and 14, connecting the high-side circuit section 10A to the low-side circuit section 10B. At the same time, the operation of the pressurizing pump 30 provided in the high-side hot water supply pipe 31 is stopped, and the on-off valve 33 provided in the high-side hot water return pipe 32 is closed. As a result, the hot water heated in the heat source unit 1 is supplied to the high-level hot water supply unit 2A and the low-level hot water supply unit 2B through the supply pipe 11 without being stored in the elevated hot water storage tank 40. Furthermore, the hot water that has passed through the high-level hot water supply unit 2A and the low-level hot water supply unit 2B is returned to the heat source unit 1 by passing through the operating circulation pump 20 installed in the return pipe 12 of the hot water circulation circuit 10.

[0050] On the other hand, in the open-type hot water supply mode, as shown in Figure 7, the hot water supply mode switching means 62 opens the backflow prevention valve 47 as the pressure in the open hot water circulation circuit 10 decreases, opening the gravity supply pipe 46. Then, the high-side separation valves 13 and 14 are closed, separating the high-side circuit portion 10A from the low-side circuit portion 10B. At this point, the pressurizing pump 30 provided in the high-side hot water supply pipe 31 is activated, opening the on-off valve 33 provided in the high-side hot water return pipe 32. Then, the hot water heated in the heat source unit 1 is supplied to the elevated hot water storage tank 40 via the tank inlet pipeline 43 and stored there. The hot water stored in the elevated hot water storage tank 40 is then supplied to the lower-side hot water supply unit 2B of the lower-side circuit unit 10B via the gravity supply pipeline 46, due to the weight of the hot water transmitted from the elevated hot water storage tank 40 through the gravity supply pipeline 46. Thus, the power required to supply the hot water stored in the elevated hot water storage tank 40 to the lower-side hot water supply unit 2B is reduced, improving energy efficiency. Simultaneously, the hot water stored in the elevated hot water storage tank 40 is supplied to the elevated hot water supply section 2A of the elevated circuit section 10A through the operating pressurizing pump 30 installed in the elevated hot water supply pipe 31. The hot water that has passed through the elevated hot water supply section 2A is returned to the elevated hot water storage tank 40 by passing through the on-off valve 33 of the elevated hot water return pipe 32. In other words, in this open hot water supply mode, the hot water stored in the elevated hot water storage tank 40 is supplied to the lower-side hot water supply unit 2B connected to the lower-side circuit unit 10B by gravity through the gravity supply pipeline 46, while the hot water stored in the elevated hot water storage tank 40 is supplied to the upper-side hot water supply unit 2A connected to the upper-side circuit unit 10A by the pressure pump 30. Although not shown in the diagram, a back pressure valve can be provided in the high-level hot water return pipe 32 to maintain the supply pressure of hot water to the high-level hot water supply section 2A. [Explanation of symbols]

[0051] 1 Heat source 2. Hot water supply unit 10 Hot water circulation circuit 20 Circulation pump 40 Elevated hot water storage tanks 41 Water level sensor (water level detection means) 43 Tank inlet pipeline 46 Dead weight supply pipe 50 Water supply pipeline 51 Flow sensor (means for detecting the amount of replenishment water) 62 Hot water supply mode switching means 63 Control means

Claims

1. A hot water supply system equipped with a hot water circulation circuit that circulates hot water between a heat source and a hot water supply unit, The system comprises an open-type hot water storage tank capable of storing hot water heated by the heat source unit, and a hot water supply mode switching means capable of switching the hot water supply mode in a manner that changes the state of the hot water circulation circuit. The aforementioned hot water supply modes include a sealed hot water supply mode and an open hot water supply mode. The sealed hot water supply mode is a hot water supply mode in which the state of the hot water circulation circuit is in a sealed state, separated from the hot water storage tank, and the hot water heated in the heat source unit is circulated and supplied to the hot water supply unit by a circulation pump provided in the hot water circulation circuit. The open-type hot water supply mode is a hot water supply mode in which the state of the hot water circulation circuit is in an open state connected to the hot water storage tank, and the hot water heated in the heat source unit is temporarily stored in the hot water storage tank and supplied to the hot water supply unit. The hot water storage tank is an elevated hot water storage tank installed at a higher position than the hot water supply unit. The elevated hot water storage tank and the hot water circulation circuit are connected by a gravity-fed supply pipeline, A hot water supply system in which the hot water supply mode switching means closes the gravity supply pipeline in the closed hot water supply mode and opens the gravity supply pipeline in the open hot water supply mode.

2. In the hot and cold water circulation circuit, the circulation pump is provided on the primary side of the heat source, and a water supply pipeline is connected between the heat source and the circulation pump to supply water at a predetermined set supply water pressure. The hot water supply system according to claim 1, wherein the hot water supply mode switching means operates the circulation pump in the sealed hot water supply mode and the open hot water supply mode, respectively.

3. The hot water supply system according to claim 1 or 2, further comprising a control means for controlling the operation of the hot water supply mode switching means based on the hot water supply load in the hot water supply unit, thereby automatically switching the hot water supply mode between the sealed hot water supply mode and the open hot water supply mode.

4. The system includes a water supply amount detection means for detecting the amount of water supplied to the hot and cold water circulation circuit, The hot water supply system according to claim 3, wherein the control means changes the hot water supply mode to the open hot water supply mode when the amount of replenishment water detected by the replenishment water amount detection means exceeds a predetermined set amount of replenishment water while the hot water supply mode is the closed hot water supply mode.

5. The system includes a water level detection means for detecting the water level in the elevated hot water storage tank, The hot water supply system according to claim 3, wherein the control means changes the hot water supply mode to the closed hot water supply mode when the water level detected by the water level detection means exceeds a predetermined set water level while the hot water supply mode is the open hot water supply mode.

6. In addition to the hot and cold water circulation circuit, the system is equipped with a tank inlet pipeline that guides the hot and cold water heated in the heat source unit to the elevated hot water storage tank, and is configured to allow the destination of the hot and cold water heated in the heat source unit to be selectively set between the hot and cold water circulation circuit and the tank inlet pipeline. The hot water supply system according to claim 1 or 2, wherein the hot water supply mode switching means selectively sets the destination of the hot water heated by the heat source to the hot water circulation circuit in the closed hot water supply mode, and selectively sets the destination of the hot water heated by the heat source to the tank inlet pipe in the open hot water supply mode.

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