Heat medium circulation device

Abstract

This system promptly detects overheating abnormalities in heat transfer fluids caused by poor circulation of the heat transfer fluid within the circulation circuit of a heat transfer fluid circulation device, resulting in localized overheating of the heat transfer fluid. [Solution] A heating means for heating a heat transfer medium and a heat dissipation means for releasing heat from the heat transfer medium are connected to form a closed, annular circulation circuit in which the heat transfer medium is sent in a predetermined direction by a circulation pump, and the temperature of the heat transfer medium flowing out from the heating means is detected by a supply temperature sensor. When the heat dissipation operation that utilizes heat dissipation by the heat dissipation means is started, the circulation pump is activated and heating of the heating means is started. Then, an overheating abnormality is detected when the rising gradient, which is the rate of increase in the temperature detected by the supply temperature sensor per unit time, exceeds a predetermined judgment gradient.

Description

Technical Field

[0001] The present invention relates to a heat medium circulation device that circulates a heat medium between a heating means for heating the heat medium and a heat radiation means for releasing the heat of the heat medium.

Background Art

[0002] A heat medium circulation device that circulates a heat medium between a heating means for heating the heat medium and a heat radiation means for releasing the heat of the heat medium is widely used as a heater or a water heater. Such a heat medium circulation device includes a circulation circuit that connects a heating means (for example, a heat exchanger) and a heat radiation means (for example, a heating terminal or a hot water heat exchanger) to form a closed loop, and a circulation pump that sends the heat medium in the circulation circuit in a predetermined direction. Then, when starting a heat radiation utilization operation (for example, a heating operation or a hot water supply operation) that utilizes heat radiation in the heat radiation means, the circulation pump is operated and the heating of the heating means is started. During the execution of the heat radiation utilization operation, the operation of the circulation pump is continued, and the heating of the heating means is controlled according to the temperature of the circulating heat medium.

[0003] In such a heat medium circulation device, due to reasons such as a failure of the circulation pump or the on-off valve on the heating terminal side not opening, the heat medium in the circulation circuit may not be circulating or the circulation flow rate may be small (hereinafter, poor circulation of the heat medium). Nevertheless, an abnormality (hereinafter, overheating abnormality) may occur in which the heat medium in the circulation circuit is locally overheated by performing the heating of the heating means. Therefore, in order to detect the overheating abnormality, it has been proposed to install a bimetal switch, which is a temperature sensing switch, in a heat exchanger as a heating means (for example, Patent Document 1). In the heat exchanger, since the heat of the combustion exhaust generated by the combustion of the burner is transmitted to the heat medium, due to poor circulation of the heat medium in the circulation circuit, the heat medium inside the heat exchanger is overheated and the temperature of the heat exchanger itself also rises. When the temperature at the installation location of the bimetal switch in the heat exchanger reaches the threshold temperature, the bimetal switch operates (the contact changes from the closed state to the open state), and it becomes possible to detect the overheating abnormality.

Prior Art Documents

Patent Documents

[0004] [Patent Document 1] Japanese Patent Publication No. 2013-167426 [Overview of the project] [Problems that the invention aims to solve]

[0005] However, as mentioned above, when detecting overheating abnormalities using a bimetallic switch installed in the heat exchanger as a heating means, the heat exchanger is often already at a considerably high temperature when the bimetallic switch is activated. This presents a problem in that the heat exchanger and surrounding components may be damaged by heat, and there has been a need for the development of a technology that can detect overheating abnormalities before the bimetallic switch is activated.

[0006] This invention addresses the aforementioned problems of the prior art and aims to provide a technology that can quickly detect overheating abnormalities in which the heat medium is locally overheated due to poor circulation of the heat medium in the circulation circuit of a heat medium circulation device. [Means for solving the problem]

[0007] To solve the above-mentioned problems, the heat transfer medium circulation device of the present invention employs the following configuration: <First aspect> In a heat transfer medium circulation device that circulates a heat transfer medium between a heating means for heating the heat transfer medium and a heat dissipation means for releasing the heat from the heat transfer medium, A circulating circuit is formed by connecting the heating means and the heat dissipation means to form a closed, annular circuit, A circulation pump that sends the heat transfer medium in the circulation circuit in a predetermined direction, A supply temperature sensor for detecting the temperature of the heat transfer medium that has flowed out from the heating means, A heating control means for controlling the heating of the heating means, An overheating abnormality detection means for detecting an overheating abnormality in which the heat medium is locally overheated due to poor circulation of the heat medium in the circulation circuit. Equipped with, The circulation pump starts operating upon the commencement of the heat dissipation operation that utilizes the heat dissipation means, and continues to operate throughout the execution of the heat dissipation operation. The heating control means starts heating the heating means in conjunction with the start of the heat dissipation utilization operation. The overheating abnormality detection means detects the overheating abnormality when the upward slope, which is the change in the temperature detected by the supply temperature sensor per unit time, exceeds a predetermined determination slope. It is characterized by the following:

[0008] In this first embodiment of a heat transfer medium circulation device, if an overheating abnormality occurs due to poor circulation of the heat transfer medium in the circulation circuit, the heat transfer medium overheated by the heating means may expand due to thermal expansion and overflow from the heating means, causing the temperature detected by the supply temperature sensor (hereinafter referred to as the supply temperature) to rise rapidly. Therefore, if the rise gradient of the supply temperature is greater than or equal to the judgment gradient, there is a possibility of an overheating abnormality, and by using this as a detection condition, it becomes possible to quickly detect an overheating abnormality.

[0009] <Second aspect> In a heat transfer fluid circulation device according to the first embodiment, When the heating control means detects the temperature of the supply temperature sensor during the heat dissipation operation and the temperature reaches the heating stop temperature, it temporarily stops the heating of the heating means. The overheating abnormality detection means detects the overheating abnormality when, in addition to the upward slope of the temperature detected by the supply temperature sensor becoming equal to or greater than the determination slope, the heating means stops heating based on the temperature detected by the supply temperature sensor reaching the heating stop temperature, and then, after the temperature detected by the supply temperature sensor remains above an abnormality determination temperature higher than the heating stop temperature for a specified period of time or longer, as the detection conditions. It is characterized by the following:

[0010] In this second embodiment of a heat transfer medium circulation device, if an overheating abnormality occurs due to poor circulation of the heat transfer medium in the circulation circuit, a portion of the heat transfer medium overheated by the heating means may boil and overflow from the heating means. Even if the heating means is temporarily stopped when the supply temperature reaches the heating stop temperature, the supply temperature may rise further, exceeding the abnormality detection temperature and continuing for some time. On the other hand, if the heating means is temporarily stopped because the supply temperature reaches the heating stop temperature due to air mixed in the heat transfer medium in the circulation circuit, the supply temperature rarely rises further, and even if the supply temperature exceeds the abnormality detection temperature, it will quickly decrease if the heat transfer medium is circulating. Therefore, if the supply temperature exceeds the abnormality detection temperature and continues for a specified time or longer, there is a high possibility of an overheating abnormality, and by adding this to the detection conditions, the accuracy of detecting overheating abnormalities can be improved.

[0011] <Third aspect> In a heat transfer fluid circulation device according to the first or second embodiment, The heating means is equipped with a return temperature sensor that detects the temperature of the heat transfer medium flowing into it. In addition to the detection conditions, the overheating abnormality detection means detects the overheating abnormality if, during the period from the start of the heat dissipation operation until a predetermined return waiting time has elapsed, the temperature detected by the return temperature sensor has not reached the return reference temperature. It is characterized by the following:

[0012] In this third embodiment of a heat transfer medium circulation device, when an overheating abnormality occurs, even if the supply temperature of the heat transfer medium rises rapidly due to heating by the heating means, the temperature detected by the return temperature sensor (hereinafter referred to as the return temperature) hardly rises due to poor circulation of the heat transfer medium in the circulation circuit. On the other hand, if the supply temperature rises rapidly due to air mixed in with the heat transfer medium in the circulation circuit, the return temperature will rise at least once between the return trigger and the return waiting time, due to the circulation of the heat transfer medium in the circulation circuit. Therefore, by adding the condition that the return temperature has not risen to the return reference temperature between the return trigger and the return waiting time, the detection accuracy of overheating abnormalities caused by poor circulation of the heat transfer medium can be improved.

[0013] <Fourth aspect> In a heat transfer fluid circulation device of the third embodiment, The aforementioned return reference temperature is the temperature obtained by adding the expected return rise value to the temperature detected by the return temperature sensor at the return specific trigger. It is characterized by the following:

[0014] In this fourth embodiment of the heat transfer fluid circulation system, if the current heat transfer fluid utilization operation is started not long after the previous heat transfer fluid utilization operation has ended, the heat transfer fluid in the circulation circuit may already be somewhat warm at the start. Even in such cases, by comparing the return temperature with the return temperature at the specific return trigger and confirming that the return temperature does not rise above the expected return rise value, it is possible to further improve the accuracy of detecting overheating abnormalities.

[0015] <Fifth aspect> In any one of the first to fourth embodiments of the heat transfer fluid circulation device, The heat dissipation means is a hot water heat exchanger that heats water supplied from a water source through heat exchange with the heat transfer medium to produce hot water. The system includes a hot water temperature sensor that detects the temperature of the hot water supplied from the hot water heat exchanger, In addition to the detection conditions, the overheat abnormality detection means detects the overheat abnormality on the condition that the detected temperature of the hot water supply temperature sensor does not reach the hot water supply reference temperature during the period from the hot water supply specific trigger after the start of the heat dissipation utilization operation until a predetermined hot water supply standby time elapses. It is characterized by this.

[0016] In such a heat medium circulation device of the fifth aspect, when an overheat abnormality occurs, even if the forward temperature of the heat medium rapidly rises due to the heating of the heating means, the detected temperature of the hot water supply temperature sensor (hereinafter referred to as the hot water supply temperature) hardly rises due to poor circulation of the heat medium in the circulation circuit. On the other hand, when the forward temperature rapidly rises due to air or the like mixed in the heat medium in the circulation circuit, the hot water supply temperature rises at least once during the period from the hot water supply specific trigger until the hot water supply standby time elapses because the heat medium in the circulation circuit is circulating. Therefore, by adding the condition that the hot water supply temperature does not rise to the hot water supply reference temperature during the period from the hot water supply specific trigger until the hot water supply standby time elapses, the detection accuracy of the overheat abnormality caused by poor circulation of the heat medium can be improved.

[0017] <The sixth aspect> In the heat medium circulation device of the fifth aspect, The hot water supply reference temperature is a temperature obtained by adding an assumed rise value of the hot water supply to the detected temperature of the hot water supply temperature sensor at the hot water supply specific trigger. It is characterized by this.

[0018] In such a heat medium circulation device of the sixth aspect, when the current heat dissipation utilization operation is started without much time having elapsed since the previous heat dissipation utilization operation (hot water supply operation) ended, the heat medium in the circulation circuit (particularly, in the hot water supply heat exchanger) may be warmed to a certain extent at the start point. Even in such a case, by confirming that there is no rise in the hot water supply temperature by more than the assumed rise value of the hot water supply compared to the hot water supply temperature at the hot water supply specific trigger, it becomes possible to further improve the detection accuracy of the overheat abnormality.

[0019] <The seventh aspect> In any one of the heat medium circulation devices of the first aspect to the sixth aspect, The heat dissipation means includes a heating terminal that heats the room by releasing heat from the heat transfer medium, and a hot water heat exchanger that heats water supplied from a water source by heat exchange with the heat transfer medium to produce hot water. The aforementioned heat dissipation utilization operation includes a switching means that can switch between a heating operation in which the heat transfer medium is circulated to the heating terminal and a hot water supply operation in which the heat transfer medium is circulated to the hot water heat exchanger. Different determination gradients are set for the heating operation and the hot water supply operation, with the determination gradient for the heating operation being gentler than the determination gradient for the hot water supply operation. It is characterized by the following:

[0020] In this seventh embodiment of the heat transfer fluid circulation system, the amount of heat generated by the heating means is generally greater during hot water supply operation than during heating operation, and the supply temperature tends to rise more easily. Therefore, by switching the judgment gradient depending on whether it is heating operation or hot water supply operation, it is possible to reduce the failure to detect overheating abnormalities, especially during heating operation, while suppressing false detections and improving the accuracy of overheating abnormality detection. [Brief explanation of the drawing]

[0021] [Figure 1] This is an explanatory diagram showing the configuration of a heating and hot water supply system 1 as an example of the application of a heat transfer medium circulation system. [Figure 2] This diagram illustrates characteristic phenomena that occur when an overheating abnormality occurs while the controller 40 controls the combustion of burner 3. [Figure 3] This is a flowchart of the combustion control process in this embodiment, which is performed by the controller 40 to control the combustion of burner 3. [Figure 4] This is a flowchart of the first part of the combustion control process of the first modified example performed by the controller 40. [Figure 5] This is a flowchart of the latter part of the combustion control process of the first modified example performed by the controller 40. [Figure 6] This is a flowchart of the first half of the combustion control process of the second modified example performed by the controller 40. [Figure 7]This is a flowchart of the latter part of the combustion control process in the second modified example performed by the controller 40. [Modes for carrying out the invention]

[0022] Figure 1 is an explanatory diagram showing the configuration of a heating and hot water supply system 1 as an example of the application of a heat transfer medium circulation device. As shown in the figure, the heating and hot water supply system 1 of this embodiment is equipped with a combustion unit 4, which has a burner 3 built inside a housing 2 that burns a mixture of fuel gas and combustion air. A combustion fan 5 is connected to the combustion unit 4, and the mixture gas is supplied by this combustion fan 5.

[0023] On the intake side of the combustion fan 5, there is a confluence section 6 that merges an air supply passage 7 that supplies combustion air and a gas supply passage 8 that supplies fuel gas. The gas supply passage 8 is equipped with an on / off valve 9 that opens and closes the gas supply passage 8, and a zero governor 10 that reduces the pressure of the fuel gas pumped from the upstream side to atmospheric pressure. The confluence section 6 has a built-in control valve that makes it possible to adjust the ratio of combustion air and fuel gas flowing into the combustion fan 5. When the combustion fan 5 is driven, air from inside the housing 2 and fuel gas downstream of the zero governor 10 in the gas supply passage 8 are drawn into the combustion fan 5 through the confluence section 6 in a predetermined ratio via the air supply passage 7, and the mixed gas is sent to the combustion unit 4.

[0024] In the combustion unit 4, the mixed gas is burned in the built-in burner 3. In the illustrated example, as the mixed gas is ejected downward from the burner 3, a flame is formed downward and the combustion exhaust is sent downward. The combustion fan 5 and the on-off valve 9 are electrically connected to a controller 40 that controls the overall operation of the heating and hot water supply system 1. The controller 40 controls the opening and closing of the on-off valve 9 and also controls the amount of combustion in the burner 3 by changing the rotation speed of the combustion fan 5 according to the required amount of heating.

[0025] Furthermore, the combustion unit 4 is equipped with a spark plug 11 that generates a spark for the burner 3 by discharging a high voltage, a flame rod 12 that detects the flame (ignition) of the burner 3, and a check valve 13 that prevents backflow from the combustion unit 4 to the combustion fan 5. The spark plug 11 and the flame rod 12 are electrically connected to the controller 40.

[0026] A first heat exchanger 15 is provided below the burner 3, and a second heat exchanger 16 is provided below the first heat exchanger 15. The combustion exhaust generated by the combustion in the burner 3 is sent downward and passes through the first heat exchanger 15 and the second heat exchanger 16 in sequence. At this time, the first heat exchanger 15 recovers sensible heat from the combustion exhaust, and the second heat exchanger 16 recovers latent heat from the combustion exhaust.

[0027] The combustion exhaust that has passed through the first heat exchanger 15 and the second heat exchanger 16 is then discharged through the exhaust duct 17 and out of the exhaust port 18 protruding from the top of the housing 2. In the illustrated example, an air intake port 19 is also provided at the top of the housing 2, and air taken into the housing 2 from the air intake port 19 is supplied to the confluence section 6 through the air supply passage 7.

[0028] The first heat exchanger 15 is connected upstream to the downstream side of the second heat exchanger 16. The downstream side of the first heat exchanger 15 is connected to the upstream side of the panel radiator 20, which serves as a heating terminal, via a supply passage 21, and the upstream side of the second heat exchanger 16 is connected to the downstream side of the panel radiator 20 via a return passage 22. The return passage 22 is equipped with a circulation pump 23 that sends the heat transfer medium toward the second heat exchanger 16, and a return temperature sensor 24 that detects the temperature of the heat transfer medium flowing into the second heat exchanger 16 (hereinafter referred to as the return temperature). The circulation pump 23 and the return temperature sensor 24 are electrically connected to the controller 40.

[0029] The heat transfer medium sent to the second heat exchanger 16 by the operation of the circulation pump 23 is preheated in the second heat exchanger 16 by the latent heat recovered from the combustion exhaust of the burner 3, and then sent to the first heat exchanger 15. In the first heat exchanger 15, the heat transfer medium is heated by the sensible heat recovered from the combustion exhaust of the burner 3, and the high-temperature heat transfer medium is supplied to the panel radiator 20 through the supply passage 21. A supply temperature sensor 25 is provided in the supply passage 21 connected downstream of the first heat exchanger 15 to detect the temperature of the heat transfer medium flowing out of the first heat exchanger 15 (hereinafter referred to as the supply temperature), and the supply temperature sensor 25 is electrically connected to the controller 40. The controller 40 determines the required amount of heating based on the temperature detected by the supply temperature sensor 25 and controls the combustion of the burner 3. In this embodiment, the burner 3, the first heat exchanger 15, and the second heat exchanger 16 correspond to the "heating means" of the present invention. Furthermore, the controller 40 in this embodiment has a function equivalent to the "heating control means" of the present invention.

[0030] Furthermore, a bimetallic switch 26, which is a temperature-sensing switch, is installed in the first heat exchanger 15, and the bimetallic switch 26 is electrically connected to the controller 40. When the temperature of the first heat exchanger 15 rises excessively and the temperature at the location where the bimetallic switch 26 is installed reaches a threshold temperature, the contacts of the bimetallic switch 26 change from a closed state to an open state, causing the on-off valve 9 of the gas supply passage 8 to close and forcibly stopping combustion in the burner 3.

[0031] The panel radiator 20 includes a pipe 20a that meanders within a metal panel and an on-off valve 20b that opens and closes the pipe 20a. When the on-off valve 20b is opened, the heat transfer medium passes through the pipe 20a and dissipates heat, warming the surrounding area. In this embodiment, the panel radiator 20 (heating terminal) corresponds to the "heat dissipation means" of the present invention.

[0032] The heat transfer fluid that has passed through the panel radiator 20 returns to the circulation pump 23 via the return passage 22 and is sent back to the second heat exchanger 16 for further circulation. The circulation pump 23 in this embodiment is designed to maintain a constant rotational speed while supplying the heat transfer fluid. In this embodiment, hot water is used as the heat transfer fluid in the heating and hot water supply system 1, but the heat transfer fluid is not limited to hot water; an antifreeze such as ethylene glycol or silicone oil may also be used.

[0033] Furthermore, a branch passage 27, which branches off from the supply passage 21 downstream of the supply temperature sensor 25, is connected to the return passage 22 upstream of the circulation pump 23, and a hot water heat exchanger 28 is provided in this branch passage 27. In addition, a three-way valve 29 is provided at the connection point between the branch passage 27 and the return passage 22, and the three-way valve 29 is electrically connected to the controller 40. This three-way valve 29 makes it possible to switch whether the heat transfer medium flowing out of the first heat exchanger 15 is circulated through the route passing through the panel radiator 20 (heating terminal) (hereinafter referred to as the external circulation circuit) or through the route passing through the hot water heat exchanger 28 (hereinafter referred to as the internal circulation circuit). Furthermore, both the external circulation circuit in this embodiment, which is formed by connecting the first heat exchanger 15 and the second heat exchanger 16 with the panel radiator 20 in a closed annular shape via a supply passage 21 and a return passage 22, and the internal circulation circuit in which the first heat exchanger 15 and the second heat exchanger 16 with the hot water heat exchanger 28 in a closed annular shape via a supply passage 21, a return passage 22, and a branch passage 27, correspond to the "circulation circuit" of the present invention. Also, the three-way valve 29 in this embodiment corresponds to the "switching means" of the present invention. Hereafter, when there is no need to particularly distinguish between the external circulation circuit and the internal circulation circuit, they may simply be referred to as the "circulation circuit".

[0034] The hot water heat exchanger 28 is a liquid-liquid heat exchanger, and is connected to a water supply passage 30 and a hot water outlet passage 31. The tap water supplied to the hot water heat exchanger 28 through the water supply passage 30 is heated in the hot water heat exchanger 28 by heat exchange with a heat transfer medium, and flows out as hot water through the hot water outlet passage 31. The water supply passage 30 is equipped with a water flow sensor 32 for measuring the flow rate of tap water flowing into the heating and hot water supply device 1, a water flow servo 33 for adjusting the flow rate of tap water, and a water supply temperature sensor 34 for detecting the temperature of tap water. The hot water outlet passage 31 is equipped with a heat exchange outlet hot water temperature sensor 35 for detecting the temperature of the hot water immediately after it flows out of the hot water heat exchanger 28. These water flow sensors 32, water flow servo 33, water supply temperature sensor 34, and heat exchange outlet hot water temperature sensor 35 are electrically connected to the controller 40. In this embodiment, the hot water heat exchanger 28 corresponds to the "heat dissipation means" of the present invention.

[0035] Furthermore, in the heating and hot water supply system 1 of this embodiment, the downstream side of the water supply temperature sensor 34 in the water supply passage 30 and the downstream side of the heat exchanger hot water temperature sensor 35 in the hot water outlet passage 31 are connected by a bypass passage 36. Some of the tap water flowing into the heating and hot water supply system 1 can pass through the bypass passage 36 without being supplied to the hot water heat exchanger 28, while the remainder is supplied to the hot water heat exchanger 28. The hot water heated in the hot water heat exchanger 28 is then mixed with the tap water that has passed through the bypass passage 36 and flows out of the heating and hot water supply system 1. A bypass servo 37 is provided at the connection point between the bypass passage 36 and the hot water outlet passage 31, and the bypass servo 37 is electrically connected to the controller 40. The mixing ratio of the hot water heated in the hot water heat exchanger 28 and the tap water that has passed through the bypass passage 36 can be changed by the bypass servo 37.

[0036] Downstream of the bypass servo 37 in the hot water outlet passage 31, a hot water outlet temperature sensor 38 is provided to detect the temperature of the hot water flowing out from the heating and hot water supply system 1. The hot water outlet temperature sensor 38 is electrically connected to the controller 40. As described above, if a portion of the tap water from the water supply passage 30 flows through the bypass passage 36 and joins the hot water outlet passage 31 without passing through the hot water heat exchanger 28, the temperature detected by the hot water outlet temperature sensor 38 will naturally be lower than the temperature detected by the heat exchanger outlet temperature sensor 35. By adjusting the mixing ratio with the bypass servo 37, temperature fluctuations of the hot water flowing out from the heating and hot water supply system 1 can be suppressed.

[0037] Furthermore, the controller 40 is electrically connected to a hot water remote control 41 and a heating remote control 42. By operating the hot water remote control 41, the user can switch the hot water operation ON and OFF states and set the hot water temperature. The user can also operate the heating remote control 42 to start and stop the heating operation and set the heating temperature. In this embodiment, the heating operation in which the heat medium is circulated in the external circulation circuit (panel radiator 20) and the hot water operation in which the heat medium is circulated in the internal circulation circuit (hot water heat exchanger 28) correspond to the "heat dissipation utilization operation" of the present invention.

[0038] In the heating and hot water supply system 1 described above, if the circulation pump 23 fails, combustion may occur in the burner 3 even though the heat medium is not circulating in either the external or internal circulation circuit, or the circulation flow rate is small (hereinafter referred to as poor circulation of the heat medium). This can cause an abnormality in which the heat medium in the circulation circuit is locally overheated in the first heat exchanger 15 (hereinafter referred to as an overheating abnormality). Furthermore, an overheating abnormality can occur not only when the circulation pump 23 fails, but also when the on-off valve 20b of the panel radiator 20 (heating terminal) is not open during heating operation in which the heat medium is circulated in the external circulation circuit, or when the three-way valve 29 remains stuck in circulation to the external circulation circuit side during hot water supply operation in which the heat medium is circulated in the internal circulation circuit, and the on-off valve 20b of the panel radiator 20 is closed. Furthermore, while it is conceivable to install a flow sensor in the circulation circuit to detect the circulation (flow) of the heat transfer medium within the circulation circuit, flow sensors generally have a large pressure loss. Therefore, in the heating and hot water supply system 1 of this embodiment, a flow sensor is not used with the intention of reducing the pressure loss in the circulation circuit.

[0039] When an overheating abnormality occurs, the heat transfer medium in the first heat exchanger 15 overheats, and as a result, the temperature of the first heat exchanger 15 itself rises. When the temperature at the installation site of the bimetal switch 26 reaches the threshold temperature, the bimetal switch 26 activates (the contact changes from a closed state to an open state), allowing for the detection of the overheating abnormality. This then forcibly stops combustion in the burner 3 by shutting off the fuel gas supply. However, since the threshold temperature at which the bimetal switch 26 activates is generally quite high, the first heat exchanger 15 is often already at a high temperature when the bimetal switch 26 activates, which can cause thermal damage to the first heat exchanger 15 and surrounding components. Therefore, in the heating and hot water supply system 1 of this embodiment, the controller 40 controls the combustion of the burner 3 based on the temperature detected by the supply temperature sensor 25, and by capturing characteristic events that occur when an overheating abnormality occurs, it is possible to detect the overheating abnormality before the bimetal switch 26 activates. The following will explain this point in detail, but as preparation, the characteristic events that occur when an overheating abnormality occurs will be explained first.

[0040] Figure 2 is an explanatory diagram illustrating characteristic events that occur when an overheating abnormality occurs while the controller 40 is controlling the combustion of the burner 3. The graph in Figure 2 has time on the horizontal axis and temperature on the vertical axis, and shows the change in the supply temperature of the heat transfer medium (temperature detected by the supply temperature sensor 25) associated with the combustion control of the burner 3. First, Figure 2(a) shows an example of how the supply temperature of the heat transfer medium changes during normal operation when the heat transfer medium is circulating in the circulation circuit and no overheating abnormality has occurred.

[0041] As shown in the diagram, when combustion is started (ignited) in burner 3, the temperature of the heat transfer medium flowing out of the first heat exchanger 15 (feed temperature) rises due to heat exchange with the combustion exhaust of burner 3. When the feed temperature reaches a predetermined combustion stop temperature, combustion in burner 3 is temporarily stopped (extinguished), and the feed temperature stops rising and begins to decrease. Subsequently, when the feed temperature drops to a predetermined combustion restart temperature lower than the combustion stop temperature, combustion in burner 3 is restarted (ignited), and the feed temperature begins to rise again. Note that the combustion stop temperature in this embodiment corresponds to the "heating stop temperature" of the present invention.

[0042] In this way, when the supply temperature reaches the combustion stop temperature, combustion in burner 3 is temporarily stopped (extinguished), and when the supply temperature drops to the combustion restart temperature, combustion in burner 3 is restarted (ignited). This control is repeatedly performed by the controller 40. Even while combustion in burner 3 is temporarily stopped, the circulation of the heat medium by the circulation pump 23 continues, and the temperature of the heat medium in the circulation circuit is made uniform. Therefore, it is also possible to restart combustion in burner 3 based on the return temperature (temperature detected by the return temperature sensor 24) of the heat medium dropping to the combustion restart temperature, instead of the supply temperature.

[0043] On the other hand, Figure 2(b) shows an example where the heat transfer medium in the circulation circuit is not circulating and the supply temperature of the heat transfer medium changes when an overheating abnormality occurs. When combustion is started (ignited) in the burner 3 with the heat transfer medium in the circulation circuit not circulating, the heat transfer medium that has been overheated in the first heat exchanger 15 becomes hot and expands due to thermal expansion (partially boiling), and the hot heat transfer medium that overflows from the first heat exchanger 15 into the supply passage 21 reaches the supply temperature sensor 25, causing the temperature detected by the supply temperature sensor 25 (supply temperature) to rise rapidly. At this time, although combustion in the burner 3 is temporarily stopped (extinguished) when the supply temperature reaches the combustion stop temperature, the heat transfer medium that has been overheated in the first heat exchanger 15 is already at a high temperature (partially boiling), so the supply temperature rises further and may exceed the abnormality detection temperature which is higher than the combustion stop temperature.

[0044] Then, after a while from the cessation of combustion in burner 3, the thermal expansion (boiling) of the heat transfer medium in the first heat exchanger 15 subsides, and the low-temperature heat transfer medium is drawn back from the downstream side of the supply passage 22 (panel radiator 20 side) to the first heat exchanger 15 side and reaches the supply temperature sensor 25, causing the supply temperature to drop sharply. In addition, in the heating and hot water supply system 1, an overpressure prevention device (not shown) may be installed in the supply passage 21 outside the housing 2. If the pressure in the circulation circuit increases due to the thermal expansion (partial boiling) of the heat transfer medium overheated in the first heat exchanger 15 and the overpressure prevention device is activated, a flow of heat transfer medium towards the overpressure prevention device will occur in the supply passage 21 as the heat transfer medium is ejected, which may cause the supply temperature detected by the supply temperature sensor 25 to drop sharply.

[0045] When the supply temperature drops to the combustion restart temperature, the combustion in burner 3 is restarted (ignited), which overheats the heat transfer medium in the first heat exchanger 15, causing the supply temperature to rise rapidly again. As a result, the supply temperature quickly reaches the combustion stop temperature, and combustion in burner 3 is temporarily stopped (extinguished) once more. If combustion in burner 3 is restarted based on the return temperature instead of the supply temperature, the return temperature will not rise if the heat transfer medium in the circulation circuit is not circulating. If it is lower than the combustion restart temperature, combustion in burner 3 will restart after a predetermined waiting period following the stop of combustion. Thus, when an overheating abnormality occurs, the supply temperature may fluctuate wildly, and the stopping (extinguishing) and restart (ignition) of combustion in burner 3 may occur repeatedly in a shorter time than under normal conditions.

[0046] Figure 2(c) shows an enlarged example comparing the upward gradient, which is the rate of increase in the supply temperature of the heat transfer medium per unit time, under normal conditions and when an overheating abnormality occurs. Under normal conditions, the heat transfer medium circulating due to the operation of the circulation pump 23 is gradually heated as it passes through the first heat exchanger 15, so the supply temperature of the heat transfer medium flowing out of the first heat exchanger 15 and detected by the supply temperature sensor 25 rises slowly, as shown by the solid line in Figure 2(c).

[0047] In contrast, when an overheating abnormality occurs, as mentioned above, the heat medium overheats in the first heat exchanger 15 due to poor circulation of the heat medium, causing thermal expansion (partial boiling). As a result, the supply temperature of the heat medium overflowing from the first heat exchanger 15 and detected by the supply temperature sensor 25 may rise sharply, as shown by the dashed line in Figure 2(c).

[0048] Therefore, by setting a judgment gradient (an unusual upward gradient shown by a dashed line in Figure 2(c)) that is steeper than the upper limit of the upward gradient of the supply temperature experimentally determined in advance while the heat transfer medium in the circulation circuit is circulating, and if the upward gradient of the supply temperature detected by the supply temperature sensor 25 exceeds the judgment gradient, there is a possibility that an overheating abnormality has occurred, and by using this as a detection condition, it becomes possible to quickly detect an overheating abnormality. In this embodiment, different judgment gradients are set for heating operation and hot water supply operation. During hot water supply operation, the amount of combustion at the burner 3 tends to be larger (the supply temperature rises more easily) compared to heating operation in order to quickly supply hot water at the set temperature, so the judgment gradient for hot water supply operation is steeper than the judgment gradient for heating operation.

[0049] Figure 3 is a flowchart of the combustion control process performed by the controller 40 for combustion control of the burner 3 in this embodiment. This combustion control process is performed when either the heating operation or the hot water supply operation starts and continues until the heating operation or hot water supply operation ends. As shown in the figure, when the combustion control process starts, first the circulation pump 23 is activated (STEP 1), and the combustion of the mixed gas is started in the burner 3 (STEP 2).

[0050] Next, it is determined whether the rising gradient, which is the rate of increase in the temperature detected by the supply temperature sensor 25 (supply temperature) per unit time, has exceeded the judgment gradient (STEP 3). As mentioned above, different judgment gradients are set for heating operation and hot water supply operation, and the judgment gradient corresponding to the current operating state (whether heating operation or hot water supply operation is in progress) is referred to.

[0051] If the upward gradient of the supply temperature is not equal to or greater than the judgment gradient (STEP3: no), then it is determined whether or not the supply temperature (temperature detected by the supply temperature sensor 25) has reached a predetermined combustion stop temperature (STEP4). As mentioned above, in the combustion control of burner 3 in this embodiment, the condition for temporarily stopping combustion in burner 3 (hereinafter referred to as the combustion stop condition) is when the supply temperature reaches the combustion stop temperature. If the supply temperature has not yet reached or greater than the combustion stop temperature (STEP4: no), the process returns to STEP3, and the determination of whether or not the upward gradient of the supply temperature is equal to or greater than the judgment gradient (STEP3), and the determination of whether or not the supply temperature has reached or greater than the combustion stop temperature (STEP4) are repeated.

[0052] Then, if the supply temperature rises above the combustion stop temperature (STEP 4: yes), the combustion stop condition is met, so combustion in burner 3 is temporarily stopped (STEP 5), and then it is determined whether the supply temperature (temperature detected by supply temperature sensor 25) has fallen below a predetermined combustion restart temperature (STEP 6). As mentioned above, in the combustion control of burner 3 in this embodiment, the condition for restarting combustion in burner 3 (hereinafter referred to as the combustion restart condition) is when the supply temperature drops to the combustion restart temperature. Alternatively, the combustion restart condition may be when the return temperature (temperature detected by return temperature sensor 24) drops to the combustion restart temperature instead of the supply temperature.

[0053] If the supply temperature is not yet below the combustion restart temperature (STEP6: no), the judgment in STEP6 is repeated at a predetermined interval. Then, if the supply temperature falls below the combustion restart temperature (STEP6: yes), the combustion restart condition is met, so combustion is restarted in burner 3 (STEP7), and then the process returns to STEP3, where the judgment of whether the rise gradient of the supply temperature is equal to or greater than the judgment gradient (STEP3), and the judgment of whether the supply temperature is equal to or greater than the combustion stop temperature (STEP4) are repeated again.

[0054] Then, if the rising gradient of the supply temperature exceeds the judgment gradient (STEP 3: yes), a characteristic event of an overheating abnormality has occurred, which is an unusually rapid rise in the supply temperature. Therefore, an overheating abnormality is detected (STEP 8), and the overheating abnormality is reported (STEP 9). In this embodiment, the overheating abnormality is reported by displaying it on a display unit (not shown) of the hot water remote control 41 or the heating remote control 42. Furthermore, the manner of notification is not limited to this, and the overheating abnormality may also be reported by audio output from a speaker (not shown) built into the hot water remote control 41 or the heating remote control 42. After that, the combustion control process shown in Figure 3 is terminated. Note that the controller 40 in this embodiment has a function equivalent to the "overheating abnormality detection means" of the present invention.

[0055] As described above, in the heating and hot water supply system 1 of this embodiment, the circulation pump 23 is activated and combustion in the burner 3 is started when either the heating operation or the hot water supply operation is initiated. Then, an overheating abnormality is detected when the rising gradient, which is the rate of increase in the temperature (supply temperature) detected by the supply temperature sensor 25 per unit time, exceeds the judgment gradient.

[0056] As mentioned above, if an overheating abnormality occurs due to poor circulation of the heat transfer medium in the circulation circuit, the overheated heat transfer medium in the first heat exchanger 15 will thermally expand (partially boiling) and overflow from the first heat exchanger 15, which may cause the supply temperature of the heat transfer medium detected by the supply temperature sensor 25 to rise sharply. Therefore, if the rise gradient of the supply temperature exceeds the judgment gradient, there is a possibility of an overheating abnormality, and by using this as a detection condition, it becomes possible to quickly detect an overheating abnormality.

[0057] Furthermore, in the heating and hot water supply device 1 of this embodiment, different judgment gradients are set for heating operation and hot water supply operation, with the judgment gradient for heating operation being gentler than the judgment gradient for hot water supply operation. Generally, during hot water supply operation, the amount of combustion at the burner 3 is larger than during heating operation, and the supply temperature tends to rise more easily. By switching the judgment gradient depending on whether it is heating operation or hot water supply operation, it is possible to reduce the failure to detect overheating abnormalities, especially during heating operation, while suppressing false detections and improving the accuracy of overheating abnormality detection.

[0058] The heating and hot water supply device 1 of the above-described embodiment also has the following modifications. Below, the modifications will be described focusing on the differences from the above-described embodiment. In the description of the modifications, components that are the same as those in the above-described embodiment will be denoted by the same reference numerals and their description will be omitted.

[0059] Figures 4 and 5 are flowcharts of the combustion control process of the first modified example executed by the controller 40. Since the combustion control process of the first modified example has many processes in common with the combustion control process of the embodiment described above, a detailed explanation of the common processes will be omitted. When the combustion control process of the first modified example is started, first the circulation pump 23 is activated (STEP 21), and after combustion in the burner 3 is started (STEP 22), it is determined whether the rising gradient of the supply temperature has become greater than or equal to the judgment gradient (STEP 23).

[0060] If the upward gradient of the supply temperature is not equal to or greater than the judgment gradient (STEP23: no), then it is determined whether or not the supply temperature has reached or exceeded the combustion stop temperature (STEP24). If the supply temperature has not yet reached or exceeded the combustion stop temperature (STEP24: no), the process returns to STEP23, and the determination of whether or not the upward gradient of the supply temperature is equal to or greater than the judgment gradient (STEP23) and the determination of whether or not the supply temperature has reached or exceeded the combustion stop temperature (STEP24) are repeated.

[0061] Then, if the upward gradient of the supply temperature does not exceed the judgment gradient and the supply temperature exceeds the combustion stop temperature (STEP24: yes), combustion in burner 3 is temporarily stopped (STEP25). After that, it is determined whether or not the supply temperature has fallen below the combustion restart temperature (STEP26), and if the supply temperature has not yet fallen below the combustion restart temperature (STEP26: no), the determination in STEP26 is repeated at a predetermined interval. On the other hand, if the supply temperature has fallen below the combustion restart temperature (STEP26: yes), combustion in burner 3 is restarted (STEP27), and then the process returns to STEP23 to determine again whether or not the upward gradient of the supply temperature has exceeded the judgment gradient (STEP23).

[0062] If the upward gradient of the supply temperature exceeds the judgment gradient (STEP23: yes), then it is determined whether the supply temperature has risen above the combustion stop temperature (STEP28). The supply temperature may rise sharply temporarily due to air mixed in with the heat transfer medium in the circulation circuit, but the supply temperature may quickly drop without reaching the combustion stop temperature, or the supply temperature may rise more slowly and remain below the combustion stop temperature. Therefore, if the supply temperature has not risen above the combustion stop temperature (STEP28: no), the process returns to STEP23 to determine again whether the upward gradient of the supply temperature has risen above the judgment gradient (STEP23).

[0063] On the other hand, if the upward gradient of the supply temperature exceeds the judgment gradient and the supply temperature exceeds the combustion stop temperature (STEP 28: yes), combustion in burner 3 is temporarily stopped (STEP 29), and then the judgment timer is activated (STEP 30). This judgment timer is a timer for measuring the elapsed time from a specific trigger, and in the first modified example of the heating and hot water supply system 1, the judgment timer is activated when combustion in burner 3 stops after the upward gradient of the supply temperature exceeds the judgment gradient, which is used as the return specific trigger. Note that the return specific trigger is not limited to this, and can be any time after the start of either heating operation or hot water supply operation. For example, the return specific trigger may be immediately after combustion in burner 3 starts in STEP 22, or immediately after the upward gradient of the supply temperature exceeds the judgment gradient in STEP 23.

[0064] Furthermore, when the judgment timer is activated, the return temperature (temperature detected by the return temperature sensor 24) is acquired and the return reference temperature is set (STEP 31). In the first modified example of the heating and hot water supply device 1, the return reference temperature is set by adding a predetermined expected return rise value to the return temperature at the return specific trigger, and as will be described in more detail later, the detection accuracy of overheating abnormalities is improved by adding the condition that the return temperature does not reach the return reference temperature.

[0065] Next, it is determined whether the supply temperature remained above the abnormal detection temperature for a specified period of time or longer (STEP 32 in Figure 5). As mentioned above, if an overheating abnormality occurs, even if combustion in burner 3 is temporarily stopped when the supply temperature reaches the combustion stop temperature, the supply temperature may rise further and exceed the abnormal detection temperature, which is higher than the combustion stop temperature (see Figure 2(b)). Also, the specified time in the first modified example is set to be longer than the duration required to eliminate noise in the supply temperature detection. On the other hand, if combustion in burner 3 is stopped because the supply temperature reaches the combustion stop temperature due to air mixed in the heat transfer medium in the circulation circuit, it is rare for the supply temperature to rise further, and even if the supply temperature exceeds the abnormal detection temperature, it will quickly decrease if the heat transfer medium in the circulation circuit is circulating.

[0066] Then, if the supply temperature is below the abnormal detection temperature, or if it exceeds the abnormal detection temperature but does not continue for the specified time (STEP32: no), the possibility of an overheating abnormality is low, so the judgment timer is stopped (STEP33), and the overheating abnormality judgment is temporarily terminated. After that, it is determined whether or not the supply temperature has fallen below the combustion restart temperature (STEP34), and if the supply temperature has not yet fallen below the combustion restart temperature (STEP34: no), the judgment in STEP34 is repeated at a predetermined cycle. On the other hand, if the supply temperature has fallen below the combustion restart temperature (STEP34: yes), combustion in burner 3 is restarted (STEP35), and then the process returns to STEP23 to determine again whether or not the rising gradient of the supply temperature has risen above the detection gradient (STEP23).

[0067] In contrast, if the supply temperature exceeds the abnormal judgment temperature and continues for a specified period of time or longer (STEP32: yes), it is determined whether the return temperature has risen above the return reference temperature (STEP36). As mentioned above, this return reference temperature is the return temperature at the specific return trigger plus the assumed return rise value. In the first modified example, the assumed return rise value is set to the lower limit of the return temperature rise value experimentally determined in advance while the heat transfer medium in the circulation circuit is circulating. Note that the return reference temperature is not limited to one that fluctuates according to the return temperature at the specific return trigger, as in the first modified example, but may also be a predetermined fixed value.

[0068] If the return temperature is not above the return reference temperature (STEP36: no), the judgment timer determines whether the predetermined return waiting time has elapsed (STEP37). If the judgment timer indicates that the return waiting time has not yet elapsed (STEP37: no), the process returns to STEP36, and it is determined again whether the return temperature is above the return reference temperature (STEP36). When an overheating abnormality occurs, the heat transfer medium in the circulation circuit is not circulating, so even if the supply temperature rises rapidly due to combustion in burner 3, the return temperature hardly rises. In contrast, if the supply temperature rises rapidly due to air mixed in the heat transfer medium in the circulation circuit, the heat transfer medium in the circulation circuit is circulating, so the return temperature rises at least once between the return trigger (stopping combustion in burner 3 after the rise gradient of the supply temperature exceeds the judgment gradient) and the expiration of the return waiting time.

[0069] Then, if the return temperature rises above the return reference temperature before the return waiting time elapses according to the judgment timer (STEP36: yes), it is determined that the heat transfer medium in the circulation circuit is circulating, and the possibility of an overheating abnormality is low, so the process proceeds to STEP33, and the judgment timer is stopped (STEP33). If, as described above, the supply temperature falls below the combustion restart temperature (STEP34: yes), combustion is restarted in burner 3 (STEP35), and the process returns to STEP23.

[0070] On the other hand, if the return temperature does not reach the return reference temperature and the return waiting time set by the judgment timer has elapsed (STEP37: yes), there is a high possibility that an overheating abnormality has occurred due to poor circulation of the heat transfer medium in the circulation circuit. In this case, the overheating abnormality is detected (STEP38) and the overheating abnormality is reported (STEP39). After that, the combustion control process shown in Figures 4 and 5 is terminated.

[0071] As explained above, in the first modified heating and hot water supply device 1, in addition to the rising gradient of the supply temperature exceeding the judgment gradient, the device is configured to detect overheating abnormalities when, after combustion in the burner 3 stops due to the supply temperature reaching the combustion stop temperature, the supply temperature continues to exceed an abnormal judgment temperature higher than the combustion stop temperature for a specified period of time or longer, as a detection condition.

[0072] As mentioned above, if an overheating abnormality occurs due to poor circulation of the heat medium in the circulation circuit, some of the heat medium overheated in the first heat exchanger 15 may boil and overflow from the first heat exchanger 15 into the supply passage 21. Even if combustion in the burner 3 is stopped when the supply temperature (temperature detected by the supply temperature sensor 25) reaches the combustion stop temperature, the supply temperature may rise further, exceeding the abnormality detection temperature and continuing for some time (see Figure 2(b)). On the other hand, if combustion in the burner 3 is stopped because the supply temperature reaches the combustion stop temperature due to air mixed in the heat medium in the circulation circuit, the supply temperature rarely rises further, and even if the supply temperature exceeds the abnormality detection temperature, it will quickly decrease if the heat medium in the circulation circuit is circulating. Therefore, if the supply temperature exceeds the abnormality detection temperature and continues for more than a specified time, there is a high possibility of an overheating abnormality, and by adding this to the detection conditions, the accuracy of detecting overheating abnormalities can be improved.

[0073] Furthermore, in the first modified heating and hot water supply device 1, in addition to the fact that the upward slope of the supply temperature has exceeded the judgment slope, and that the supply temperature has exceeded the abnormal judgment temperature for a specified period of time or longer, the detection conditions for detecting an overheating abnormality are that the temperature detected by the return temperature sensor 24 (return temperature) has not reached the return reference temperature during the period from the return specific trigger (stopping of combustion in the burner 3 after the upward slope of the supply temperature has exceeded the judgment slope) after the start of either heating operation or hot water supply operation until a predetermined return waiting time has elapsed.

[0074] As mentioned above, when an overheating abnormality occurs, the heat transfer medium in the circulation circuit is not circulating, so even if the supply temperature rises rapidly due to combustion in burner 3, the return temperature hardly rises. On the other hand, if the supply temperature rises rapidly due to air mixed in with the heat transfer medium in the circulation circuit, the return temperature will rise at least once between the return trigger and the return waiting time, because the heat transfer medium in the circulation circuit is circulating. Therefore, by adding the condition that the return temperature has not risen to the return reference temperature between the return trigger and the return waiting time, the accuracy of detecting overheating abnormalities caused by poor circulation of the heat transfer medium can be improved.

[0075] In particular, in the first modified heating and hot water supply system 1, the return reference temperature is set to the return temperature at the specific return trigger (the temperature detected by the return temperature sensor 24) plus an estimated return rise value. For example, if the current heating operation is started not long after the previous heating operation has ended, the heat transfer medium in the circulation circuit (external circulation circuit) may already be somewhat warm at the start. Even in such cases, by confirming that the return temperature does not rise by more than the estimated return rise value compared with the return temperature at the specific return trigger, it is possible to further improve the accuracy of detecting overheating abnormalities.

[0076] Figures 6 and 7 are flowcharts of the combustion control process of the second modified example executed by the controller 40. Since the combustion control process of the second modified example has many processes in common with the combustion control process of the previously described embodiment and the first modified example, a detailed explanation of the common processes will be omitted. When the combustion control process of the second modified example is started, first the circulation pump 23 is activated (STEP 51), combustion at the burner 3 is started (STEP 52), and then it is determined whether or not hot water supply operation is in progress (STEP 53).

[0077] Then, if hot water supply operation is in progress (STEP 53: yes), the judgment timer is activated (STEP 54). In the second modified example of the heating and hot water supply device 1, the judgment timer is activated when combustion at burner 3 during hot water supply operation is used as the hot water supply specific trigger. However, the hot water supply specific trigger is not limited to this, and can be any event after the start of hot water supply operation. For example, as in the first modified example described above, the stopping of combustion at burner 3 after the rising gradient of the supply temperature exceeds the judgment gradient, or the moment immediately after the rising gradient of the supply temperature exceeds the judgment gradient, may be used as the hot water supply specific trigger.

[0078] Furthermore, when the judgment timer is activated, the temperature detected by the heat exchange outlet water temperature sensor 35 (hereinafter referred to as the hot water supply temperature) is acquired and the hot water supply reference temperature is set (STEP 55). In the heating and hot water supply device 1 of the second modified example, the hot water supply reference temperature is set by adding a predetermined expected rise value to the hot water supply temperature at the hot water supply specific trigger, and as will be described in detail later, the detection accuracy of overheating abnormalities is improved by adding the detection condition that the hot water supply temperature does not reach the hot water supply reference temperature. Note that the hot water supply temperature may be obtained from the outlet water temperature sensor 38 instead of the temperature detected by the heat exchange outlet water temperature sensor 35.

[0079] On the other hand, if the system is in heating mode rather than hot water mode (STEP 53: no), steps 54 and 55 are omitted, the judgment timer is not activated, and the hot water temperature is not acquired or the hot water reference temperature is not set. Next, regardless of whether the system is in hot water mode or heating mode, it is determined whether the rising gradient of the supply temperature has become equal to or greater than the judgment gradient (STEP 56).

[0080] If the upward gradient of the supply temperature is not equal to or greater than the judgment gradient (STEP56: no), then it is determined whether or not the supply temperature has reached or exceeded the combustion stop temperature (STEP57). If the supply temperature has not yet reached or exceeded the combustion stop temperature (STEP57: no), the process returns to STEP56, and the determination of whether or not the upward gradient of the supply temperature is equal to or greater than the judgment gradient (STEP56) and the determination of whether or not the supply temperature has reached or exceeded the combustion stop temperature (STEP57) are repeated.

[0081] Then, if the upward gradient of the supply temperature does not exceed the judgment gradient and the supply temperature exceeds the combustion stop temperature (STEP 57: yes), combustion in burner 3 is temporarily stopped (STEP 58). After that, it is determined whether or not the supply temperature has fallen below the combustion restart temperature (STEP 59), and if the supply temperature has not yet fallen below the combustion restart temperature (STEP 59: no), the determination in STEP 59 is repeated at a predetermined interval. On the other hand, if the supply temperature has fallen below the combustion restart temperature (STEP 59: yes), combustion in burner 3 is restarted (STEP 60), and then the process returns to STEP 56 to determine again whether or not the upward gradient of the supply temperature has exceeded the judgment gradient (STEP 56).

[0082] If the upward gradient of the supply temperature exceeds the judgment gradient (STEP56: yes), then it is determined whether the supply temperature has reached or exceeded the combustion stop temperature (STEP61). If the supply temperature has not reached or exceeded the combustion stop temperature (STEP61: no), the process returns to STEP56 to determine again whether the upward gradient of the supply temperature has reached or exceeded the judgment gradient (STEP56).

[0083] On the other hand, if the upward gradient of the supply temperature exceeds the judgment gradient and the supply temperature exceeds the combustion stop temperature (STEP61: yes), combustion in burner 3 is temporarily stopped (STEP62). Then, it is determined whether the supply temperature remained above the abnormal judgment temperature for a specified period of time or longer (STEP63 in Figure 7). If the supply temperature is below the abnormal judgment temperature, or if it exceeded the abnormal judgment temperature but did not remain above it for a specified period of time (STEP63: no), the judgment timer is stopped if it is operating (STEP64).

[0084] Next, it is determined whether the supply temperature has fallen below the combustion restart temperature (STEP65). If the supply temperature has not yet fallen below the combustion restart temperature (STEP65: no), the determination in STEP65 is repeated at predetermined intervals. If the supply temperature has fallen below the combustion restart temperature (STEP65: yes), combustion is restarted in burner 3 (STEP66), and then the process returns to STEP56 to determine again whether the upward slope of the supply temperature has risen above the judgment slope (STEP65).

[0085] In response to this, if the supply temperature exceeds the abnormal judgment temperature and continues for a specified period of time or longer (STEP63: yes), it is determined whether or not hot water supply operation is in progress (STEP67). If hot water supply operation is in progress (STEP67: yes), it is determined whether or not the hot water supply temperature has reached or exceeded the hot water supply standard temperature (STEP68). As mentioned above, this hot water supply standard temperature is the hot water supply temperature at the specific trigger for hot water supply plus an assumed rise value for hot water supply. In the second modified example, the assumed rise value for hot water supply is set to the lower limit of the rise value for hot water supply temperature experimentally determined in advance while the heat transfer medium in the circulation circuit is circulating. Note that the hot water supply standard temperature is not limited to one that fluctuates according to the hot water supply temperature at the specific trigger for hot water supply, as in the second modified example, but may also be a predetermined fixed value.

[0086] If the hot water temperature is not above the standard hot water temperature (STEP68: no), the judgment timer determines whether the predetermined hot water waiting time has elapsed (STEP69). If the judgment timer indicates that the hot water waiting time has not yet elapsed (STEP69: no), the process returns to STEP68 to determine again whether the hot water temperature has reached or exceeded the standard hot water temperature (STEP68). When an overheating abnormality occurs during hot water operation, the heat transfer medium in the circulation circuit (internal circulation circuit) is not circulating, so even if the supply temperature rises rapidly due to combustion at burner 3, the hot water temperature hardly rises. In contrast, if the supply temperature rises rapidly due to air mixed in the heat transfer medium in the circulation circuit, the heat transfer medium in the internal circulation circuit is circulating, so the hot water temperature rises at least once between the specific hot water trigger (start of combustion at burner 3 during hot water operation) and the elapsed hot water waiting time.

[0087] Then, if the hot water temperature reaches or exceeds the hot water standard temperature before the hot water waiting time expires according to the judgment timer (STEP68: yes), it is determined that the heat transfer medium in the internal circulation circuit is circulating during hot water operation, and the possibility of an overheating abnormality is low, so the process proceeds to STEP64, and the judgment timer is stopped (STEP64). If, as described above, the supply temperature falls below the combustion restart temperature (STEP65: yes), combustion is restarted at burner 3 (STEP66), and the process returns to STEP56.

[0088] On the other hand, if the hot water supply standby time elapses without the hot water supply temperature reaching the hot water supply standard temperature (STEP69: yes), there is a high possibility that an overheating abnormality has occurred due to poor circulation of the heat transfer medium in the internal circulation circuit. In this case, an overheating abnormality is detected (STEP70), and the overheating abnormality is reported (STEP71). Also, if, as determined in STEP67, heating operation is in progress and not hot water supply operation is in progress (STEP67: no), an overheating abnormality is detected (STEP70), and the overheating abnormality is reported (STEP71), without making a determination based on the hot water supply temperature. After that, the combustion control process shown in Figures 6 and 7 is terminated.

[0089] As explained above, in the second modified heating and hot water supply device 1, in addition to the fact that the rising gradient of the supply temperature exceeds the judgment gradient, and that the supply temperature exceeds the abnormal judgment temperature and continues for a specified time or longer, the detection conditions for detecting an overheating abnormality are that the temperature detected by the heat exchange outlet water temperature sensor 35 (hot water temperature) has not reached the hot water standard temperature between the start of hot water supply operation and the start of a specific hot water supply trigger (start of combustion at burner 3) until a predetermined hot water supply waiting time has elapsed.

[0090] As mentioned above, when an overheating abnormality occurs during hot water supply operation, the heat transfer medium in the internal circulation circuit is not circulating, so even if the supply temperature rises rapidly due to combustion in burner 3, the hot water temperature hardly rises. On the other hand, if the supply temperature rises rapidly due to air mixed in with the heat transfer medium in the circulation circuit (internal circulation circuit), the heat transfer medium in the internal circulation circuit is circulating, so the hot water temperature will rise at least once between the hot water supply trigger and the hot water supply waiting time. Therefore, by adding the condition that the hot water temperature has not risen to the hot water supply standard temperature between the hot water supply trigger and the hot water supply waiting time, the accuracy of detecting overheating abnormalities caused by poor circulation of the heat transfer medium during hot water supply operation can be improved.

[0091] In particular, in the heating and hot water supply system 1 of the second modified example, the hot water supply reference temperature is set to the hot water supply temperature at the specific trigger for hot water supply (the temperature detected by the heat exchange outlet hot water temperature sensor 35) plus an estimated rise in the hot water supply temperature. For example, if the current hot water supply operation is started not long after the previous hot water supply operation has ended, the heat transfer medium in the internal circulation circuit (especially in the hot water heat exchanger 28) may already be somewhat warm at the start. Even in such cases, by confirming that the hot water supply temperature does not rise by more than the estimated rise in the hot water supply temperature compared to the hot water supply temperature at the specific trigger for hot water supply, it is possible to further improve the accuracy of detecting overheating abnormalities.

[0092] Although the heating and hot water supply device 1 (heat medium circulation device) of the embodiments and modified examples have been described above, the present invention is not limited to the embodiments and modified examples described above, and can be implemented in various forms without departing from the spirit of the invention.

[0093] For example, in the first modified example described above, overheating abnormalities were detected based on three detection conditions: (a) the upward slope of the supply temperature exceeded the judgment slope; (b) after combustion in burner 3 stopped due to the supply temperature reaching the combustion stop temperature, the supply temperature continued to exceed the abnormal judgment temperature for a specified time or longer; and (c) the return temperature never reached the return reference temperature between the return specific trigger and the return waiting time elapsed after the start of either heating operation or hot water operation. However, (c) may be excluded from the detection conditions. In this case, processes STEP 30, 31, 33, 36, and 37 can be omitted from the combustion control process in Figures 4 and 5. Alternatively, (b) may be excluded from the detection conditions. In this case, process STEP 32 can be omitted from the combustion control process in Figures 4 and 5.

[0094] Furthermore, in the second modified example described above, overheating abnormalities were detected based on three detection conditions: (a) the upward gradient of the supply temperature exceeded the judgment gradient; (b) after combustion in burner 3 stopped due to the supply temperature reaching the combustion stop temperature, the supply temperature continued to exceed the abnormal judgment temperature for a specified period of time or longer; and (d) the hot water temperature never reached the hot water standard temperature between the start of hot water supply operation and the hot water supply waiting time. However, (b) may be excluded from the detection conditions. In this case, the process of STEP 63 can be omitted from the combustion control process in Figures 6 and 7.

[0095] Furthermore, it is possible to combine the first and second modified examples described above, and in addition to (a) the upward slope of the supply temperature becoming greater than or equal to the judgment slope, and (b) the supply temperature exceeding the abnormal judgment temperature and continuing for a specified time or longer after the combustion in the burner 3 has stopped due to the supply temperature reaching the combustion stop temperature, (c) the return temperature has not reached the return standard temperature between the return specific trigger and the return waiting time elapsed since the start of hot water supply operation, and (d) the hot water temperature has not reached the hot water standard temperature between the hot water specific trigger and the hot water waiting time elapsed since the start of hot water supply operation, the detection conditions for detecting an overheating abnormality during hot water supply operation may be set as follows. This makes it possible to further improve the accuracy of detecting an overheating abnormality during hot water supply operation.

[0096] Furthermore, in the embodiments and modifications described above, a heating and hot water supply system 1 equipped with an external circulation circuit for heating operation and an internal circulation circuit for hot water supply operation was described as an example of application of the heat medium circulation system. However, the application of the heat medium circulation system is not limited to the heating and hot water supply system 1, and may also be a heater or water heater equipped with either an external circulation circuit or an internal circulation circuit.

[0097] Furthermore, in the embodiments described above, a panel radiator 20 was used as an example of a heating terminal. However, the heating terminal is not limited to a panel radiator 20, as long as it releases heat from the heat transfer medium, it may also be a bathroom heater / dryer, a fan convector, or underfloor heating.

[0098] Furthermore, in the embodiment described above, the water supply passage 30 and the hot water outlet passage 31 are connected by a bypass passage 36, and the mixing ratio of the hot water heated by the hot water heat exchanger 28 and the tap water that passes through the bypass passage 36 can be changed by a bypass servo 37. However, the embodiment is not limited to this, and the bypass passage 36 and the bypass servo 37 may be omitted. In this case, it is not necessary to provide the heat exchanger outlet hot water temperature sensor 35 and the outlet hot water temperature sensor 38 separately, and they may be combined into a single temperature sensor.

[0099] Furthermore, in the embodiment described above, a first heat exchanger 15 and a second heat exchanger 16 are provided, and the circulating heat transfer medium is preheated in the second heat exchanger 16 before being heated in the first heat exchanger 15. However, the embodiment is not limited to this, and the second heat exchanger 16 may be omitted, and the heat transfer medium may be heated by the first heat exchanger 15 alone.

[0100] Furthermore, in the embodiment described above, the heating means for heating the heat transfer medium was configured to burn the mixed gas in the burner 3. However, the configuration of the heating means is not limited to this, and may also include an electric heater, a heat pump, a fuel cell, etc. [Explanation of Symbols]

[0101] 1...Heating and hot water supply system, 2...Housing, 3...Burner, 4... Combustion unit, 5... Combustion fan, 6... Junction, 7...Air supply passage, 8...Gas supply passage, 9...On / off valve, 10... Zero governor, 11... Spark plug, 12... Flame rod 13... Check valve, 15... First heat exchanger, 16... Second heat exchanger, 17... Exhaust duct, 18... Exhaust port, 19... Air intake port, 20... Panel radiator, 20a... Pipe, 20b... On / off valve, 21... Outbound passage, 22... Return passage, 23... Circulation pump, 24...Return temperature sensor, 25...Forward temperature sensor, 26...Bimetal switch, 27...Branch passage, 28...Hot water heat exchanger, 29... Three-way valve, 30... Water supply passage, 31... Hot water outlet passage, 32...Water volume sensor, 33...Water volume servo, 34...Water supply temperature sensor, 35...Heat exchange hot water temperature sensor, 36...Bypass passage, 37...Bypass servo, 38...Hot water temperature sensor, 40...Controller, 41...Hot water remote control, 42... Remote control for heating.

Claims

1. In a heat transfer medium circulation device that circulates a heat transfer medium between a heating means for heating the heat transfer medium and a heat dissipation means for releasing the heat from the heat transfer medium, A circulating circuit is formed by connecting the heating means and the heat dissipation means to form a closed, annular circuit, A circulation pump that sends the heat transfer medium in the circulation circuit in a predetermined direction, A supply temperature sensor for detecting the temperature of the heat transfer medium that has flowed out from the heating means, A heating control means for controlling the heating of the heating means, An overheating abnormality detection means for detecting an overheating abnormality in which the heat medium is locally overheated due to poor circulation of the heat medium in the circulation circuit. Equipped with, The circulation pump starts operating upon the commencement of the heat dissipation operation that utilizes the heat dissipation means, and continues to operate throughout the execution of the heat dissipation operation. The heating control means starts heating the heating means in conjunction with the start of the heat dissipation utilization operation. The overheating abnormality detection means detects the overheating abnormality when the upward slope, which is the change in the temperature detected by the supply temperature sensor per unit time, exceeds a predetermined determination slope. A heat transfer fluid circulation device characterized by the following features.

2. In the heat transfer fluid circulation device according to claim 1, When the heating control means detects the temperature of the supply temperature sensor during the heat dissipation operation and the temperature reaches the heating stop temperature, it temporarily stops the heating of the heating means. The overheating abnormality detection means detects the overheating abnormality when, in addition to the upward slope of the temperature detected by the supply temperature sensor becoming equal to or greater than the determination slope, the heating means stops heating based on the temperature detected by the supply temperature sensor reaching the heating stop temperature, and then, after the temperature detected by the supply temperature sensor remains above an abnormality determination temperature higher than the heating stop temperature for a specified period of time or longer, as the detection conditions. A heat transfer fluid circulation device characterized by the following features.

3. In the heat transfer fluid circulation device according to claim 1 or claim 2, The heating means is equipped with a return temperature sensor that detects the temperature of the heat transfer medium flowing into it. In addition to the detection conditions, the overheating abnormality detection means detects the overheating abnormality if, during the period from the start of the heat dissipation operation until a predetermined return waiting time has elapsed, the temperature detected by the return temperature sensor has not reached the return reference temperature. A heat transfer fluid circulation device characterized by the following features.

4. In the heat transfer fluid circulation device according to claim 3, The aforementioned return reference temperature is the temperature obtained by adding the expected return rise value to the temperature detected by the return temperature sensor at the return specific trigger. A heat transfer fluid circulation device characterized by the following features.

5. In the heat transfer fluid circulation device according to claim 1 or claim 2, The heat dissipation means is a hot water heat exchanger that heats water supplied from a water source through heat exchange with the heat transfer medium to produce hot water. The system includes a hot water temperature sensor that detects the temperature of the hot water supplied from the hot water heat exchanger, In addition to the detection conditions, the overheating abnormality detection means detects the overheating abnormality if, during the period from the start of the heat dissipation operation until a predetermined hot water supply waiting time has elapsed, the temperature detected by the hot water temperature sensor has not reached the hot water supply standard temperature. A heat transfer fluid circulation device characterized by the following features.

6. In the heat transfer fluid circulation device according to claim 5, The aforementioned hot water supply standard temperature is the temperature obtained by adding an expected increase in hot water supply temperature to the temperature detected by the hot water supply temperature sensor at the specific trigger for hot water supply. A heat transfer fluid circulation device characterized by the following features.

7. In the heat transfer fluid circulation device according to claim 1 or claim 2, The heat dissipation means includes a heating terminal that heats the room by releasing heat from the heat transfer medium, and a hot water heat exchanger that heats water supplied from a water source by heat exchange with the heat transfer medium to produce hot water. The aforementioned heat dissipation utilization operation includes a switching means that can switch between a heating operation in which the heat transfer medium is circulated to the heating terminal and a hot water supply operation in which the heat transfer medium is circulated to the hot water heat exchanger. Different determination gradients are set for the heating operation and the hot water supply operation, with the determination gradient for the heating operation being gentler than the determination gradient for the hot water supply operation. A heat transfer fluid circulation device characterized by the following features.

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