Piping structure for expansion tank

Abstract

To provide a piping structure of an expansion tank capable of securing water head pressure without increasing the installation height of the expansion tank.SOLUTION: The piping structure includes an expansion pipe (10) connected to the heat source equipment (1) and extending at a position lower than the expansion tank (6), a rising pipe (11) extending upward from the expansion pipe (10) to a position higher than the expansion tank (6), a falling pipe (13) extending downward from an upper portion of the rising pipe (11) to a position lower than the expansion tank (6), and a connecting pipe (15) extending upward from a lower portion of the falling pipe (13) and connected to the expansion tank (6).SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a piping structure for an expansion tank. [Background technology]

[0002] Generally, in configurations where heat source equipment has a piping system with a closed or semi-closed circuit, the liquid in the piping system expands and contracts as the temperature of the liquid changes. Fluctuations in the volume of the liquid are particularly large in closed piping systems, and as the temperature rises, the liquid expands beyond the volume of the piping or equipment. Therefore, an expansion tank is provided to absorb these volume fluctuations. Even in configurations where heat source equipment has a semi-closed piping system, an expansion tank is provided to absorb these volume fluctuations.

[0003] As a conventional example, Fig. 7 shows a configuration in which a heat source device 1 is provided with an expansion tank 6 via a semi-closed piping system. The heat source device 1 is a modular chiller equipped with a pump. A connection part 2 of the heat source device 1 is provided with an IN-side pipe 3 into which liquid flows in, and an OUT-side pipe 4 from which the liquid flows out. An expansion pipe 5 is connected to the IN-side pipe 3, and the expansion pipe 5 extends horizontally and also extends upward at one end to be connected to an expansion tank 6 of a predetermined height.

[0004] The expansion tank 6 is installed at a higher position than the semi-closed circuit piping system, stores liquid inside, and allows the liquid to flow in and out according to changes in the volume of the liquid in the expansion pipe 5. The expansion tank 6 also has a float 7 inside and is connected to a water supply pipe 8, so that water can be supplied in response to changes in the liquid level. Furthermore, the expansion tank 6 is connected to an overflow pipe 9, so that water can be drained to the outside when the liquid level exceeds a certain height. The expansion tank 6 can be configured as either a closed type or an open type.

[0005] As a result, when the liquid in the expansion pipe 5 expands due to a rise in temperature, the liquid is absorbed by the expansion tank 6, and when the liquid in the expansion pipe 5 contracts due to a drop in temperature, the liquid flows from the expansion tank 6 into the expansion pipe 5.

[0006] Incidentally, prior art documents relating to this type of piping structure and expansion tank include Patent Document 1 below. [Prior art documents] [Patent documents]

[0007] [Patent Document 1] Patent No. 4126411 Summary of the Invention [Problem to be solved by the invention]

[0008] However, in the case of heat source equipment 1 such as a modular chiller, it is necessary to ensure the necessary head pressure. When modifying existing equipment, if there is no extra space and the height of the expansion tank 6 cannot be increased, resulting in low head pressure, there is a risk that the head pressure will be insufficient at the pump inlet of the modular chiller, causing cavitation near the pump inlet.

[0009] If a sealed expansion tank 6 is installed to ensure the hydraulic head pressure, a huge tank with a large capacity must be installed. Also, with a sealed expansion tank 6, the pressure in the sealed system fluctuates widely, which can cause the pressure in the sealed system to exceed the pressure resistance of the heat source equipment 1 and the piping system.

[0010] When installing an open-type expansion tank 6 to ensure hydraulic head pressure, there is a problem in that the installation height of the expansion tank 6 must be increased. Furthermore, when increasing the installation height of the expansion tank 6, space must be secured for the installation height, but such space is often unavailable due to height restrictions caused by interference from existing equipment. Furthermore, even if it were possible to increase the installation height of the open-type expansion tank 6, the center of gravity of the expansion tank 6 would be higher, requiring a sturdy frame, which would complicate the configuration and increase costs.

[0011] In view of the above circumstances, the present invention aims to provide a piping structure for an expansion tank that can ensure sufficient head pressure without increasing the installation height of the expansion tank. [Means for solving the problem]

[0012] The present invention provides a piping structure for an expansion tank disposed between a heat source device and the expansion tank, an expansion pipe connected to the heat source equipment and extending at a position lower than the expansion tank; a riser pipe extending upward from the expansion pipe to a position higher than the expansion tank; a faller pipe extending downward from an upper portion of the riser pipe to a position lower than the expansion tank; and a connecting pipe extending upward from a lower portion of the faller pipe to the expansion tank, The height of the rising pipe is such that a higher head pressure than that of the expansion tank can be ensured.

[0013] The piping structure of the expansion tank of the present invention may further include a sensor for detecting the liquid level in the riser pipe, and a water supply pipe for supplying water to the riser pipe in accordance with the liquid level in the riser pipe.

[0014] In the piping structure of the expansion tank of the present invention, a check valve may be provided between the riser pipe and the faller pipe at a position lower than the expansion tank, allowing water in the faller pipe to flow into the riser pipe.

[0015] In the piping structure of the expansion tank of the present invention, an opening that is open to the atmosphere may be provided between the rising pipe and the falling pipe.

[0016] In the piping structure of the expansion tank of the present invention, the expansion tank is preferably an open type expansion tank.

[0017] In the piping structure of the expansion tank of the present invention, when the chilled water in the system contracts during chilled water operation of the heat source equipment, water may be supplied from the water supply pipe according to the liquid level in the riser pipe.

[0018] In the piping structure of the expansion tank of the present invention, when the hot water in the system expands during hot water operation of the heat source equipment, the liquid level in the rising pipe rises and the overflow from the rising pipe flows into the expansion tank via the falling pipe.

[0019] In the piping structure of the expansion tank of the present invention, when the hot water in the system contracts when the hot water operation of the heat source equipment is stopped, water can be supplied from the expansion tank to the expansion pipe via the downflow pipe, check valve, and upflow pipe, and the check valve can be set to close when the differential pressure between the upflow pipe and the downflow pipe is below the minimum opening pressure.

[0020] In the piping structure of the expansion tank of the present invention, when filling the system with water after completing installation of the heat source equipment or when the heat source equipment is stopped, water can be supplied from the expansion tank to the expansion pipe via the downflow pipe, check valve, and upflow pipe, and the check valve can be set to close when the differential pressure between the upflow pipe and the downflow pipe is below the minimum opening pressure. [Effects of the Invention]

[0021] According to the piping structure of the expansion tank of the present invention, it is possible to obtain the excellent effect of ensuring the head pressure with a simple configuration without increasing the installation height of the expansion tank. [Brief explanation of the drawings]

[0022] [Figure 1] 1 is a schematic diagram showing an example of a piping structure of an expansion tank according to an embodiment of the present invention. [Figure 2] 1 is a schematic enlarged view showing an example of a piping structure of an expansion tank according to an embodiment of the present invention, illustrating the state when filled with water after installation of a heat source device is completed and when chilled water operation is stopped. FIG. [Figure 3] This is an example of the piping structure of an expansion tank according to an embodiment of the present invention, and is a schematic enlarged view showing the state when water is supplied to ensure head pressure after the cold water contracts during cold water operation of the heat source equipment. [Figure 4] 1 is a schematic enlarged view showing an example of a piping structure of an expansion tank according to an embodiment of the present invention, illustrating the state when the expansion tank is filled with water after installation of the heat source equipment is completed and when hot water operation is stopped. [Figure 5] 1 is a schematic enlarged view showing an example of a piping structure of an expansion tank according to an embodiment of the present invention, illustrating a state in which hot water expands during hot water operation of a heat source device. [Figure 6] 1 is a schematic enlarged view showing an example of a piping structure of an expansion tank according to an embodiment of the present invention, illustrating a state in which hot water contracts when hot water operation of a heat source device is stopped. [Figure 7] FIG. 1 is a conceptual diagram showing an example of a piping structure of a conventional expansion tank. DETAILED DESCRIPTION OF THE INVENTION

[0023] Hereinafter, an embodiment of the present invention will be described with reference to the accompanying drawings.

[0024] Fig. 1 shows an example of the piping structure of an expansion tank according to the present invention. In Fig. 1, heat source equipment 1 is a modular chiller, as in the conventional example, and components with the same reference numerals as in the conventional example have the same configuration.

[0025] The expansion tank 6 is an open-type tank, located at approximately the same height as the conventional tank, but higher than the semi-closed piping system. The expansion tank 6 is equipped with a float 7 and is connected to a water supply pipe 8, allowing water to be supplied in response to fluctuations in the liquid level. The expansion tank 6 is also connected to an overflow pipe 9, which allows water to be discharged to the outside when the liquid level exceeds a certain height.

[0026] A piping structure is provided between the heat source equipment 1 and the expansion tank 6. The piping structure includes a semi-closed circuit expansion pipe 10 extending from the heat source equipment 1, a riser pipe 11 extending upward from the expansion pipe 10, a first return pipe 12 that allows the riser pipe 11 to bend downward, a faller pipe 13 extending downward from the first return pipe 12, a second return pipe 14 that allows the faller pipe 13 to bend upward, and a connecting pipe 15 extending upward from the second return pipe 14.

[0027] The expansion pipe 10 is connected to a connection portion 2 of the module chiller of the heat source equipment 1 via an IN-side pipe 3 and extends laterally at a position lower than the expansion tank 6 .

[0028] The riser pipe 11 extends upward from the end of the expansion pipe 10 to a position higher than the expansion tank 6, and the height of the riser pipe 11 is set to a height that ensures a higher head pressure than the expansion tank 6. The upper end of the riser pipe 11 is positioned higher than the first return pipe 12, and the tip of the upper end is turned downward, with an opening 16 that is open to the atmosphere formed at the end of the turned portion. The opening 16 is turned downward to prevent rainwater and the like from entering, and is equipped with an insect screen 17 to prevent insects and the like from entering. The opening 16 is preferably formed at a height that is within reach of the user to facilitate maintenance.

[0029] The first return pipe 12 branches off from the upper part of the riser pipe 11 and extends laterally at a position higher than the expansion tank 6. Here, the first return pipe 12 may be an inverted U-shaped branch pipe, a branch pipe extending diagonally, or a pipe of another shape, as long as it can be folded back from the riser pipe 11 to the faller pipe 13. Furthermore, the upper part of the first return pipe 12 may be provided with an opening that is open to the atmosphere.

[0030] The falling pipe 13 extends downward from the upper part of the rising pipe 11 via the first return pipe 12 to a position lower than the expansion tank 6, and is set so that the lower end of the falling pipe 13 is at approximately the same height as the lower end of the rising pipe 11. The upper part of the falling pipe 13 may be provided with an opening that is open to the atmosphere.

[0031] The second return pipe 14 extends laterally from the lower end of the downflow pipe 13 at a position lower than the expansion tank 6 .

[0032] The connecting pipe 15 extends upward from the lower end of the downflow pipe 13 via the second return pipe 14 and is connected to the bottom of the expansion tank 6. Here, the second return pipe 14 may be a U-shaped pipe or a diagonal pipe as long as it can be bent back from the downflow pipe 13 to the connecting pipe 15.

[0033] The riser pipe 11 is provided at its lower part with a sensor 18, such as a pressure sensor, for detecting the liquid level. A head pressure supply pipe 19, which branches off from the water supply pipe 8 to the expansion tank 6 and extends from the riser pipe 11, is connected to its upper part. The sensor 18 is connected to the control unit 20 as shown in FIGS. 2 to 6 , and the liquid level in the riser pipe 11 is sent as a signal from the sensor 18 to the control unit 20. The head pressure supply pipe 19 is provided with a water supply valve 21, which opens and closes in response to a signal from the control unit 20. The location of the sensor 18 is not particularly limited, but it is preferably located at the lower part of the riser pipe 11. The sensor 18 is not limited to a pressure sensor, and other sensors capable of detecting the liquid level may be used. The head pressure supply pipe 19 is preferably connected to the upper part of the riser pipe 11, above the first return pipe 12. The control unit 20 may receive data such as the water temperature of the piping system as an external signal.

[0034] A check valve 22 is provided between the riser pipe 11 and the faller pipe 13 at a position lower than the expansion tank 6. The check valve 22 is configured to allow water to flow in only one direction from the faller pipe 13 to the riser pipe 11, and is configured to close when the pressure difference Pd between the head pressure of the riser pipe 11 and the head pressure of the faller pipe 13 is equal to or less than a predetermined pressure difference (equal to or less than the minimum opening pressure).

[0035] Here, the differential pressure Pd at which check valve 22 closes is set under the condition that the liquid level in downstream pipe 13 is approximately the same height as the liquid level in expansion tank 6, and the liquid level in riser pipe 11 is lower than the liquid level in downstream pipe 13 by a predetermined height (approximately 100 mm) that is the minimum opening pressure. Furthermore, the connection position of check valve 22 is not particularly limited as long as it is lower than the expansion tank 6, but is preferably near the bottom end of riser pipe 11 and near the bottom end of falldown pipe 13. Furthermore, check valve 22 is configured so that it does not require a signal from control unit 20, but signals from sensors such as water level and pressure provided in riser pipe 11 and falldown pipe 13 can be input to control unit 20, and an electric ball valve or the like can receive the signal from control unit 20 and operate it.

[0036] The operation of the embodiment of the present invention will be described.

[0037] The following describes a case where the piping system (within the system) of the heat source equipment 1 is for chilled water. When installation of the heat source equipment 1 is complete, the piping system, including the expansion pipe 10, is filled with water. In this water filling process, water is supplied from the expansion tank 6 to the expansion pipe 10 via the downflow pipe 13, check valve 22, and riser pipe 11, as shown in FIG. 2, to fill the expansion pipe 10 with water. At the same time, the water level in the riser pipe 11 rises, and when the differential pressure Pd between the head pressure in the riser pipe 11 and the head pressure in the fallr pipe 13 reaches a predetermined differential pressure, the check valve 22 closes as the pressure is lowered below the minimum opening pressure, completing the water filling process. Note that even when chilled water operation is stopped, the check valve 22 closes as the differential pressure Pd between the head pressure in the riser pipe 11 and the head pressure in the fallr pipe 13 reaches a predetermined differential pressure as the pressure is lowered below the minimum opening pressure.

[0038] During chilled water operation of the heat source equipment 1, the chilled water in the piping system contracts. When the chilled water contracts, the liquid level in the riser pipe 11 drops, and the head pressure of the expansion pipe 10 and the riser pipe 11 also drops. At this time, the control unit 20 determines that the head pressure of the riser pipe 11 is insufficient based on the liquid level in the riser pipe 11 sent from the sensor 18, as shown in FIG. 3, and opens the water supply valve 21 to supply water to the riser pipe 11 from the water supply pipe 19 for head pressure. This increases the liquid level in the riser pipe 11, thereby increasing the head pressure of the riser pipe 11, the expansion pipe 10, and the connection part 2 of the module chiller. Furthermore, if the control unit 20 determines that the head pressure of the riser pipe 11 is appropriate based on the liquid level in the riser pipe 11 sent from the sensor 18, it closes the water supply valve 21 to stop the supply of water.

[0039] Here, when the heat source equipment 1 is operating in chilled water mode, the chilled water in the piping system rarely expands, and even if the chilled water does expand, it does not affect the piping system, so there is no need to take the expansion of the chilled water into consideration when determining the chilled water operating conditions of the heat source equipment 1.

[0040] The following describes a case where the piping system (within the system) of the heat source equipment 1 is hot water. When installation of the heat source equipment 1 is complete, the piping system, including the expansion pipe 10, is filled with water. In this water filling, water is supplied from the expansion tank 6 to the expansion pipe 10 via the downflow pipe 13, check valve 22, and riser pipe 11, as shown in Fig. 4, to fill the expansion pipe 10 with water. At the same time, the water level in the riser pipe 11 rises, and when the differential pressure Pd between the head pressure of the riser pipe 11 and the head pressure of the downflow pipe 13 reaches a predetermined differential pressure, the check valve 22 closes as it is below the minimum opening pressure, and water filling is complete.

[0041] During hot water operation of the heat source equipment 1, the hot water in the piping system expands. In the case of this hot water expansion, the liquid level in the riser pipe 11 rises as shown in Figure 5, and the hot water flows down (overflows) from the riser pipe 11 through the first return pipe 12 to the faller pipe 13, maintaining the head pressure at the connection part 2 of the riser pipe 11, expansion pipe 10, and module chiller while preventing the head pressure from rising above a predetermined value. When the hot water flows down from the riser pipe 11 to the faller pipe 13, the hot water flows in and out between the faller pipe 13 and the expansion tank 6. Furthermore, if there is a large amount of hot water flowing into the expansion tank 6, the hot water is discharged from the expansion tank 6 to the outside through the overflow pipe 9.

[0042] If the temperature of the hot water in the piping system subsequently drops, for example, there may be a shortage of hot water in the riser pipe 11 and the expansion pipe 10, causing the liquid level in the riser pipe 11 to drop and the head pressure in the expansion pipe 10 and the riser pipe 11 to decrease. At this time, the control unit 20 sends a signal to the water supply valve 21 based on the liquid level in the riser pipe 11 sent from the sensor 18, etc., to open the water supply valve 21, and appropriately supply water to the riser pipe 11 from the water supply pipe 19 for head pressure. This increases the liquid level in the riser pipe 11, reducing the risk of a drop in head pressure in the riser pipe 11, the expansion pipe 10, and the connection part 2 of the module chiller. The control unit 20 also closes the water supply valve 21 to stop the supply of water based on the liquid level in the riser pipe 11 sent from the sensor 18, etc.

[0043] When the hot water operation of the heat source equipment 1 is stopped, the hot water in the piping system contracts. In the case of this hot water contraction, the hot water contracts in the expansion pipe 10 as shown in Fig. 6, and at the same time, the water level in the riser pipe 11 drops. At this time, water is supplied from the expansion tank 6 to the expansion pipe 10 via the fall-down pipe 13, the check valve 22, and the riser pipe 11, and when the differential pressure Pd between the head pressure in the riser pipe 11 and the head pressure in the fall-down pipe 13 reaches a predetermined differential pressure, the check valve 22 closes as it is lowered below the minimum opening pressure, and the head pressure in the riser pipe 11 is maintained.

[0044] As described above, an example of the piping structure for an expansion tank 6 is a piping structure for an expansion tank 6 disposed between the heat source equipment 1 and the expansion tank 6. The piping structure includes the expansion pipe 10 connected to the heat source equipment 1 and extending at a position lower than the expansion tank 6, the riser pipe 11 extending upward from the expansion pipe 10 to a position higher than the expansion tank 6, the faller pipe 13 extending downward from the top of the riser pipe 11 to a position lower than the expansion tank 6, and the connecting pipe 15 extending upward from the bottom of the faller pipe 13 to the expansion tank 6. The riser pipe 11 is set at a height that ensures a higher head pressure than the expansion tank 6. This configuration ensures a higher head pressure than the expansion tank 6 without increasing the installation height of the expansion tank 6. Furthermore, the head pressure can be ensured with a simple configuration, such as the riser pipe 11 and the faller pipe 13, thereby reducing costs. Furthermore, compared to increasing the installation height of the expansion tank 6, the configuration using the riser pipe 11 and the faller pipe 13 facilitates space conservation and construction. In addition, because the head pressure is ensured, it is possible to prevent a lack of head pressure at the pump inlet of the modular chiller and reduce the risk of cavitation near the pump inlet.In addition, because the head pressure is ensured and the pressure fluctuation range is smaller than with a sealed expansion tank, it is possible to suppress the adverse effects on the pressure resistance of equipment connected to the piping system.

[0045] In an example of the piping structure of an expansion tank, if a sensor 18 is provided to detect the liquid level in the riser pipe 11 and a water supply pipe 19 is provided to supply water to the riser pipe 11 according to the liquid level in the riser pipe 11, when the piping system such as the expansion pipe 10 contracts, water is supplied from the water supply pipe 19 to the riser pipe 11, and as a result, the head pressure can be secured without increasing the installation height of the expansion tank 6, and changes in the liquid level in the riser pipe 11 can be appropriately responded to.

[0046] In an example of the piping structure of the expansion tank, if a check valve 22 is provided between the riser pipe 11 and the faller pipe 13 at a position lower than the expansion tank 6, which allows water from the faller pipe 13 to flow into the riser pipe 11, when filling the system with water after installation of the heat source equipment 1 is completed, or when the hot water contracts when the hot water operation of the heat source equipment 1 is stopped, water can be supplied from the expansion tank 6 to the expansion pipe 10 via the faller pipe 13, the check valve 22, and the riser pipe 11, allowing for proper operation while maintaining head pressure.

[0047] In an example of the piping structure of an expansion tank, if an open port 16 that is open to the atmosphere is provided between the rising pipe 11 and the falling pipe 13, it becomes easier to supply water from the water supply pipe 19 for head pressure to the rising pipe 11, thereby enabling proper operation while ensuring head pressure.

[0048] In the example of the expansion tank piping structure, if the expansion tank 6 is an open-type expansion tank, it can eliminate the problems that occur with closed-type expansion tanks, such as the problem that a closed-type expansion tank must be a huge tank to ensure head pressure, and it can reduce costs compared to closed-type expansion tanks.In addition, it can solve the problem that the pressure in the closed system exceeds the withstand pressure of the heat source equipment 1 and the piping system due to the large fluctuation range of the pressure in the closed system.

[0049] In an example of the piping structure of an expansion tank, if the cold water in the system contracts during cold water operation of the heat source equipment 1, water can be supplied from the water supply pipe 19 according to the liquid level in the riser pipe 11, allowing for proper operation while ensuring head pressure.

[0050] In an example of the piping structure of the expansion tank, when the hot water in the system expands during hot water operation of the heat source equipment 1, the liquid level in the rising pipe 11 rises, and the overflow from the rising pipe 11 flows into the expansion tank 6 via the falling pipe 13, which enables proper operation while ensuring head pressure.

[0051] In an example of the piping structure of an expansion tank, if the hot water in the system contracts when the hot water operation of the heat source equipment 1 is stopped, water is supplied from the expansion tank 6 to the expansion pipe 10 via the downflow pipe 13, check valve 22, and upflow pipe 11, and the check valve 22 is set to close when the differential pressure Pd between the upflow pipe 11 and the downflow pipe 13 is below the minimum opening pressure, allowing for proper operation while ensuring sufficient head pressure.

[0052] In an example of the piping structure of an expansion tank, when water is filled in the system when the heat source equipment 1 is shut down or when installation is completed, water is supplied from the expansion tank 6 to the expansion pipe 10 via the downflow pipe 13, check valve 22, and upflow pipe 11, and the check valve 22 is set to close when the differential pressure Pd between the upflow pipe 11 and the downflow pipe 13 is below the minimum opening pressure, which enables proper operation while ensuring the head pressure.

[0053] The piping structure of the expansion tank of the present invention is not limited to the above-described embodiment, and it goes without saying that various modifications can be made within the scope of the present invention. [Explanation of symbols]

[0054] 1 Heat source equipment 2 Connection 3 Piping 4 Piping 5 Expansion tube 6. Expansion tank 7. Float 8 Water pipe 9 Overflow pipe 10 Expansion tube 11 Rise piping 12 First turn pipe 13 Down piping 14 Second turn tube 15 Connecting pipe 16 Open mouth 17 Insect net 18 Sensors 19 Water supply pipe 20 Control Unit 21 Water supply valve 22 Check valve Pd differential pressure

Claims

1. A piping structure of an expansion tank disposed between a heat source device and the expansion tank, an expansion pipe connected to the heat source equipment and extending at a position lower than the expansion tank; a riser pipe extending upward from the expansion pipe to a position higher than the expansion tank; a faller pipe extending downward from an upper portion of the riser pipe to a position lower than the expansion tank; and a connecting pipe extending upward from a lower portion of the faller pipe to the expansion tank, A piping structure for an expansion tank, characterized in that the height of the riser pipe is such that a higher head pressure than that of the expansion tank can be ensured.

2. 2. The piping structure of an expansion tank according to claim 1, further comprising: a sensor for detecting the liquid level in the riser pipe; and a water supply pipe for supplying water to the riser pipe according to the liquid level in the riser pipe.

3. 2. The piping structure of an expansion tank according to claim 1, further comprising a check valve between the riser pipe and the faller pipe, at a position lower than the expansion tank, which allows water from the faller pipe to flow into the riser pipe.

4. 2. The piping structure of claim 1, further comprising an opening that is open to the atmosphere between the rising pipe and the falling pipe.

5. 2. The piping structure of an expansion tank according to claim 1, wherein the expansion tank is an open-type expansion tank.

6. The expansion tank piping structure described in claim 2, characterized in that when the cold water in the system contracts during cold water operation of the heat source equipment, water is supplied from the water supply pipe depending on the liquid level in the riser pipe.

7. The piping structure of an expansion tank described in at least one of claims 1 to 4, characterized in that when the hot water in the system expands during hot water operation of the heat source equipment, the liquid level in the riser pipe rises and the overflow from the riser pipe flows into the expansion tank through the faller pipe.

8. The expansion tank piping structure described in claim 3, characterized in that when the hot water in the system contracts when the hot water operation of the heat source equipment is stopped, water is supplied from the expansion tank to the expansion pipe via the downflow pipe, check valve, and upflow pipe, and the check valve is set to close when the differential pressure between the upflow pipe and the downflow pipe is below the minimum opening pressure.

9. The expansion tank piping structure described in claim 3, characterized in that when water is filled in the system after installation of the heat source equipment is completed or when the heat source equipment is stopped, water is supplied from the expansion tank to the expansion pipe via the downflow pipe, check valve, and upflow pipe, and the check valve is set to close when the differential pressure between the upflow pipe and the downflow pipe is below the minimum opening pressure.

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