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 and a heat dissipation means are connected to form a closed annular circulation circuit in which the heat medium is sent in a predetermined direction by a circulation pump. The supply temperature of the heat medium flowing out of the heating means and the return temperature of the heat medium flowing into the heating means are detected. When the heat dissipation utilization operation starts, the circulation pump is activated and heating of the heating means is started. Heating is stopped when the supply temperature reaches the heating stop temperature, which is used as the heating stop condition. Heating is then restarted when the supply temperature drops below the heating restart temperature, which is used as the heating restart condition. An additional condition can be added to the heating restart condition, which is that the temperature difference between the supply temperature and the return temperature becomes smaller than a judgment value. If an additional condition is included, an overheating abnormality is detected when the additional condition is not met during the time elapsed from the stop of heating until the judgment time has elapsed, which is used as the detection condition.

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. Also, 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 a non-opening of the on-off valve on the heating terminal side, even though the heat medium in the circulation circuit is not circulating or the circulation flow rate is small (hereinafter referred to as poor circulation of the heat medium), an abnormality (hereinafter referred to as overheating abnormality) may occur in which the heat medium in the circulation circuit is locally overheated by executing 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 transferred to the heat medium, due to poor circulation of the heat medium in the circulation circuit, the heat medium in the heat exchanger is overheated and the temperature of the heat exchanger itself also rises. Then, 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 return temperature sensor for detecting the temperature of the heat transfer medium flowing into the heating means, A heating control means for controlling the heating of the aforementioned 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 aforementioned heating control means is Upon commencement of the heat dissipation utilization operation, the heating means is started to heat up. When the temperature detected by the aforementioned supply temperature sensor reaches the heating stop temperature, the heating of the heating means is temporarily stopped, The heating restart condition is when either the temperature detected by the supply temperature sensor or the temperature detected by the return temperature sensor drops to the heating restart temperature, and it is possible to add as an additional condition to the heating restart condition that the temperature difference between the temperature detected by the supply temperature sensor and the temperature detected by the return temperature sensor becomes smaller than a determination value. The overheating abnormality detection means detects the overheating abnormality when the additional condition is included in the heating restart condition, and the detection condition is that the additional condition has not been met during the period from the cessation of heating by the heating means based on the fulfillment of the heating stop condition until a predetermined determination time has elapsed. It is characterized by the following:

[0008] In this first embodiment of the heat transfer medium circulation device, when an overheating abnormality occurs, the temperature of the heat transfer medium in the circulation circuit is not uniformly distributed as under normal conditions, even when the heating means has stopped heating, due to poor circulation of the heat transfer medium in the circulation circuit. As a result, the temperature detected by the return temperature sensor (hereinafter referred to as the return temperature) hardly rises, and the temperature difference between the temperature detected by the supply temperature sensor (hereinafter referred to as the supply temperature) and the return temperature tends not to decrease. Therefore, if the temperature difference between the supply temperature and the return temperature does not fall below the judgment value (i.e., the additional condition is not met) during the period from the cessation of heating by the heating means until the judgment time has elapsed, there is a possibility of an overheating abnormality. By making this a detection condition, it becomes possible to quickly detect an overheating abnormality. Furthermore, by including the additional condition as a heating restart condition, heating by the heating means will not be restarted simply because either the supply temperature or the return temperature has fallen to the heating restart temperature before the judgment time has elapsed. This allows for continued confirmation of whether the temperature of the heat transfer medium in the circulation circuit is uniformly distributed while heating by the heating means is stopped until the judgment time has elapsed.

[0009] <Second aspect> In a heat transfer fluid circulation device according to the first embodiment, In addition to the detection conditions, 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:

[0010] In this second embodiment of a heat transfer fluid circulation system, if an overheating abnormality occurs due to poor circulation of the heat transfer fluid in the circulation circuit, the heat transfer fluid overheated by the heating means may expand due to thermal expansion and overflow from the heating means, causing an unusually rapid increase in the supply temperature of the heat transfer fluid detected by the supply temperature sensor. Therefore, if the rise gradient of the supply temperature is greater than or equal to the judgment gradient, 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 a second embodiment, The heating control means includes the additional condition in the heating restart condition based on the fact that the upward slope of the temperature detected by the supply temperature sensor has become equal to or greater than the determination slope. It is characterized by the following:

[0012] In this third embodiment of a heat transfer medium circulation device, confirming whether the additional conditions are met (whether the temperature of the heat transfer medium in the circulation circuit is uniform) requires waiting until the maximum judgment time has elapsed since the heating means stopped. Therefore, the additional conditions are included in the heating restart conditions and used to detect overheating abnormalities only when there is a high possibility of overheating abnormalities, such as when the rising gradient of the supply temperature exceeds the judgment gradient. When the possibility of overheating abnormalities is low, the additional conditions are not included in the heating restart conditions, thereby maintaining the convenience and comfort of the user of the heat transfer medium circulation device without delaying the restart of heating by the heating means.

[0013] <Fourth aspect> In a heat transfer fluid circulation device according to the first or second embodiment, The overheating abnormality detection means detects the overheating abnormality when, in addition to the detection conditions, the heating means stops heating based on the fulfillment of the heating stop conditions, and the temperature detected by the supply temperature sensor remains above the abnormality determination temperature (higher than the heating stop temperature) for a specified period of time or longer, as a detection condition. It is characterized by the following:

[0014] In such a heat medium circulation device of the fourth aspect, when an overheat abnormality occurs due to poor circulation of the heat medium in the circulation circuit, a part of the heat medium heated by the heating means may boil and overflow from the heating means. Even if the heating of the heating means is temporarily stopped when the forward temperature reaches the heating stop temperature and the heating stop condition is satisfied, the forward temperature may further rise and exceed the abnormal determination temperature and continue for a while. On the other hand, when the forward temperature reaches the heating stop temperature (the heating stop condition is satisfied) due to air or the like mixed in the heat medium in the circulation circuit, and the heating of the heating means is temporarily stopped, it is rare for the forward temperature to further rise. Even if the forward temperature exceeds the abnormal determination temperature, if the heat medium is circulating, it will immediately drop. Therefore, if the forward temperature exceeds the abnormal determination temperature and continues for a specified time or more, the possibility of overheat abnormality is high. By adding this as a detection condition, the detection accuracy of overheat abnormality can be improved.

[0015] <Fifth Aspect> In the heat medium circulation device of the fourth aspect, after the heating of the heating means is stopped based on the satisfaction of the heating stop condition, the additional condition is included in the heating restart condition based on the fact that the detected temperature of the forward temperature sensor exceeds the abnormal determination temperature and continues for the specified time or more. It is characterized by this.

[0016] In such a heat medium circulation device of the fifth aspect, to confirm whether the additional condition is satisfied (whether the temperature of the heat medium in the circulation circuit is equalized), it is necessary to wait until the maximum determination time elapses from the stop of the heating of the heating means. Therefore, only when the possibility of overheat abnormality is high, such as when the forward temperature exceeds the abnormal determination temperature and continues for a specified time or more, the additional condition is included in the heating restart condition for use in detecting overheat abnormality. When the possibility of overheat abnormality is low, the additional condition is not included in the heating restart condition, so that the convenience and comfort of the user of the heat medium circulation device can be maintained without delaying the restart of the heating of the heating means.

Brief Description of the Drawings

[0017] [Figure 1] It is an explanatory diagram showing the configuration of the heating and hot water supply device 1 as an application example of the heat medium circulation device. [Figure 2] It is an explanatory diagram showing characteristic events that appear when overheating abnormality occurs while the controller 40 performs combustion control of the burner 3. [Figure 3] It is a flowchart of the combustion control process of this embodiment that the controller 40 executes for the combustion control of the burner 3. [Figure 4] It is a flowchart of the first half part in the combustion control process of the first modification example that the controller 40 executes. [Figure 5] It is a flowchart of the second half part in the combustion control process of the first modification example that the controller 40 executes. [Figure 6] It is a flowchart of the first half part in the combustion control process of the second modification example that the controller 40 executes. [Figure 7] It is a flowchart of the second half part in the combustion control process of the second modification example that the controller 40 executes.

Embodiment for Carrying Out the Invention

[0018] FIG. 1 is an explanatory diagram showing the configuration of the heating and hot water supply device 1 as an application example of the heat medium circulation device. As shown in the figure, the heating and hot water supply device 1 of this embodiment includes a combustion unit 4 having a burner 3 for burning a mixed gas of fuel gas and combustion air built inside a housing 2. A combustion fan 5 is connected to the combustion unit 4, and the mixed gas is sent in by this combustion fan 5.

[0019] 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.

[0020] 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.

[0021] 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.

[0022] 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.

[0023] 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.

[0024] 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.

[0025] 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.

[0026] 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.

[0027] 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.

[0028] 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.

[0029] 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). In this embodiment, both the external circulation circuit, which is formed by connecting the first heat exchanger 15 and the second heat exchanger 16 with the panel radiator 20 in a ring shape using a supply passage 21 and a return passage 22, and the internal circulation circuit, which is formed by connecting the first heat exchanger 15 and the second heat exchanger 16 with the hot water heat exchanger 28 in a ring shape using a supply passage 21, a return passage 22, and a branch passage 27, correspond to the "circulation circuit" 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".

[0030] 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.

[0031] 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.

[0032] 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.

[0033] 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.

[0034] 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.

[0035] 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 location of the bimetal switch 26 reaches a 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 the temperature detected by the return temperature sensor 24. 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, we will first describe the characteristic events that occur when an overheating abnormality occurs.

[0036] 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.

[0037] As shown in the figure, when combustion is started (ignited) in burner 3, the temperature of the heat medium flowing out of the first heat exchanger 15 (feed temperature) rises due to heat exchange with the combustion exhaust of burner 3. Then, when the feed temperature reaches a predetermined combustion stop temperature, which is the combustion stop condition, combustion in burner 3 is temporarily stopped (extinguished), and the feed temperature stops rising and begins to fall. Subsequently, when the feed temperature drops to a predetermined combustion restart temperature lower than the combustion stop temperature, which is the combustion restart condition, combustion in burner 3 is restarted (ignited), and the feed temperature begins to rise again from falling. Note that the combustion stop temperature in this embodiment corresponds to the "heating stop temperature" of the present invention, and the combustion stop condition in this embodiment corresponds to the "heating stop condition" of the present invention. Similarly, the combustion restart temperature in this embodiment corresponds to the "heating restart temperature" of the present invention, and the combustion restart condition in this embodiment corresponds to the "heating restart condition" of the present invention.

[0038] In this way, when the supply temperature reaches the combustion stop temperature (the combustion stop condition is met), combustion in burner 3 is temporarily stopped (extinguished), and when the supply temperature drops to the combustion restart temperature (the combustion restart condition is met), combustion in burner 3 is restarted (ignited). This control is repeatedly performed by the controller 40. Furthermore, even while combustion in burner 3 is temporarily stopped, the circulation of the heat medium by the circulation pump 23 continues, and as the temperature of the heat medium in the circulation circuit becomes uniform, the temperature detected by the return temperature sensor 24 (return temperature) rises as the supply temperature decreases, and the temperature difference between the supply temperature and the return temperature decreases. Therefore, it is also possible to restart combustion in burner 3 by using the return temperature dropping to the combustion restart temperature as the combustion restart condition instead of the supply temperature.

[0039] 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, when the supply temperature reaches the combustion stop temperature and the combustion stop condition is met, combustion in the burner 3 is temporarily stopped (extinguished), but since the heat transfer medium that has been overheated in the first heat exchanger 15 is already hot (partially boiling), the supply temperature rises further and may exceed the abnormality detection temperature which is higher than the combustion stop temperature.

[0040] Then, after a while has passed since the combustion in burner 3 stopped, 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, which can cause 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 that has been 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 can cause the supply temperature detected by the supply temperature sensor 25 to drop sharply.

[0041] When the supply temperature drops to the combustion restart temperature and the combustion restart conditions are met, combustion in burner 3 is restarted (ignited). As a result, the heat transfer medium in the first heat exchanger 15 is overheated, and the supply temperature rises rapidly again. The supply temperature quickly reaches the combustion stop temperature, the combustion stop conditions are met, and combustion in burner 3 is stopped (extinguished) once more. Thus, when an overheating abnormality occurs, the supply temperature fluctuates wildly, and the stopping (extinguishing) and restart (ignition) of combustion in burner 3 may occur repeatedly in a shorter time than under normal conditions.

[0042] Furthermore, as mentioned above, when restarting combustion in burner 3 based on the return temperature instead of the supply temperature, if the heat transfer medium in the circulation circuit is not circulating, the return temperature will hardly rise at all. If it is lower than the combustion restart temperature, the combustion restart condition will be met, and combustion in burner 3 will be restarted after a predetermined waiting time following the cessation of combustion. In this way, when an overheating abnormality occurs due to poor circulation of the heat transfer medium in the circulation circuit, even while combustion in burner 3 is stopped, the temperature of the heat transfer medium in the circulation circuit will not become uniform as under normal circumstances, and the return temperature will hardly rise. As a result, the temperature difference between the supply temperature and the return temperature tends not to decrease. Therefore, if the temperature difference between the supply temperature and the return temperature does not fall below the judgment value during the period from the cessation of combustion in burner 3 based on the meeting of the combustion stop condition until a predetermined judgment time has elapsed, there is a possibility that an overheating abnormality caused by poor circulation of the heat transfer medium has occurred. If this is used as a detection condition, it will be possible to quickly detect the overheating abnormality.

[0043] 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).

[0044] Next, it is determined whether the combustion stop condition has been met (STEP 3). As mentioned above, in the combustion control of burner 3 in this embodiment, the combustion stop condition is when the temperature detected by the supply temperature sensor 25 (supply temperature) reaches a predetermined combustion stop temperature. If the combustion stop condition has not yet been met (STEP 3: no), the determination in STEP 3 is repeated at a predetermined cycle.

[0045] Then, if the combustion stop condition is met (STEP 3: yes), the combustion in burner 3 is temporarily stopped (STEP 4), and the judgment timer is activated (STEP 5). This judgment timer measures the time elapsed since the combustion in burner 3 stopped due to the fulfillment of the combustion stop condition.

[0046] Following the operation of the judgment timer, it is determined whether or not the combustion restart condition has been met (STEP 6). In the combustion control of burner 3 in this embodiment, the combustion restart condition includes not only that the supply temperature has dropped to a predetermined combustion restart temperature, but also that the temperature difference between the supply temperature and the return temperature has become smaller than a predetermined judgment value. Note that while combustion in burner 3 is stopped, the supply temperature is not necessarily higher than the return temperature, and the situation may be reversed due to the circulation of the heat transfer medium in the circulation circuit. Alternatively, the combustion restart condition may be that the return temperature has dropped to the combustion restart temperature instead of the supply temperature.

[0047] If the combustion restart conditions, including the additional conditions, are not yet met (STEP6: no), the judgment timer determines whether the predetermined judgment time has elapsed (STEP7). If the judgment timer determines that the judgment time has not yet elapsed (STEP7: no), the process returns to STEP6 to determine again whether the combustion restart conditions, including the additional conditions, have been met (STEP6). As mentioned above, when an overheating abnormality occurs, after a while from the cessation of combustion in burner 3, the supply temperature may decrease to the combustion restart temperature, but due to poor circulation of the heat transfer medium in the circulation circuit, the return temperature hardly rises, making it difficult for the temperature difference between the supply temperature and the return temperature to become smaller than the judgment value. In contrast, when the heat transfer medium in the circulation circuit is circulating, the supply temperature decreases during the cessation of combustion in burner 3 to the combustion restart temperature, and the temperature of the heat transfer medium in the circulation circuit becomes uniform, making the temperature difference between the supply temperature and the return temperature smaller than the judgment value.

[0048] Then, if the combustion restart conditions, including the additional conditions, are met before the judgment timer expires (STEP 6: 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 judgment timer is stopped (STEP 8), and the overheating abnormality judgment is temporarily terminated. After that, when combustion is restarted in burner 3 (STEP 9), the process returns to STEP 3, and the subsequent processes described above are repeated.

[0049] On the other hand, if the judgment timer elapses without the combustion restart conditions, including the additional conditions, being met (STEP 7: yes), it is possible that an overheating abnormality has occurred due to poor circulation of the heat transfer medium in the circulation circuit, because the additional conditions have never been met (the temperature difference between the supply temperature and the return temperature has never been smaller than the judgment value). In this case, an overheating abnormality is detected (STEP 10) and the overheating abnormality is reported (STEP 11). 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.

[0050] As described above, in the heating and hot water supply device 1 of this embodiment, when either heating or hot water supply operation is started, the circulation pump 23 is activated and combustion in the burner 3 is started. Combustion in the burner 3 is temporarily stopped when the temperature detected by the supply temperature sensor 25 (supply temperature) reaches the combustion stop temperature, and then combustion in the burner 3 is restarted when the supply temperature drops to the combustion restart temperature, and this control is repeated. In addition, the combustion restart condition is further enhanced by adding that the temperature difference between the supply temperature and the temperature detected by the return temperature sensor 24 (return temperature) becomes smaller than a judgment value. An overheating abnormality is detected when the additional condition is not met during the period from the cessation of combustion in the burner 3 based on the fulfillment of the combustion stop condition until a predetermined judgment time has elapsed, and this is used as the detection condition.

[0051] As mentioned above, when an overheating abnormality occurs, due to poor circulation of the heat transfer medium in the circulation circuit, the temperature of the heat transfer medium in the circulation circuit does not become uniform as under normal circumstances, even when combustion at burner 3 is stopped. As a result, the return temperature hardly rises, and the temperature difference between the supply temperature and the return temperature tends not to decrease. Therefore, if the temperature difference between the supply temperature and the return temperature does not fall below the judgment value (i.e., the additional condition is not met) during the period from the stop of combustion at burner 3 until the judgment time has elapsed, there is a possibility of an overheating abnormality. By using this as a detection condition, it becomes possible to quickly detect an overheating abnormality. Furthermore, by including the additional condition as a combustion restart condition, combustion at burner 3 will not restart simply because the supply temperature has dropped to the combustion restart temperature before the judgment time has elapsed. This allows for continued confirmation of whether the temperature of the heat transfer medium in the circulation circuit becomes uniform while combustion at burner 3 is stopped, until the judgment time has elapsed.

[0052] 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.

[0053] 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, which is the change in the rise of the supply temperature per unit time, has become greater than or equal to the judgment gradient (STEP 23).

[0054] In the first modified example, the judgment gradient is set steeper than the upper limit of the supply temperature rise gradient experimentally determined in advance when the heat medium in the circulation circuit is circulating. Under normal conditions when the heat medium is circulating in the circulation circuit and no overheating abnormality occurs, the circulating heat medium is gradually heated as it passes through the first heat exchanger 15, so the rise gradient of the supply temperature detected by the supply temperature sensor 25 as it flows out of the first heat exchanger 15 is gentler than the judgment gradient. In contrast, when an overheating abnormality occurs, as described above, the heat medium that has been overheated in the first heat exchanger 15 due to poor circulation of the heat medium undergoes thermal expansion (partially boiling), and the rise gradient of the supply temperature detected by the supply temperature sensor 25 as it overflows from the first heat exchanger 15 may be steeper than the judgment gradient (see Figure 2). In addition, in the heating and hot water supply device 1 of the first modified example, different judgment gradients are set for heating operation and hot water supply operation, and the judgment gradient according to the current operating state (whether heating operation or hot water supply operation is in progress) is referred to. During hot water supply operation, the combustion rate at burner 3 is higher than during heating operation in order to quickly supply hot water at the set temperature, and the supply temperature tends to rise more easily. Therefore, the judgment gradient for hot water supply operation is steeper than the judgment gradient for heating operation.

[0055] 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 the combustion stop condition has been met (the supply temperature has reached the combustion stop temperature) (STEP24). If the combustion stop condition has not yet been met (STEP24: no), the process returns to STEP23, and the determination of whether the upward gradient of the supply temperature has become equal to or greater than the judgment gradient (STEP23) and the determination of whether the combustion stop condition has been met (STEP24) are repeated.

[0056] Then, if the rising gradient of the supply temperature does not exceed the judgment gradient and the combustion stop condition is met (STEP24: yes), combustion in burner 3 is temporarily stopped (STEP25). After that, it is determined whether or not the combustion restart condition has been met (STEP26). In the combustion control of burner 3 of the first modified example, the combustion restart condition does not include the aforementioned additional condition (the temperature difference between the supply temperature and the return temperature becoming smaller than the judgment value) and is standard. Therefore, in STEP26, the combustion restart condition is set to the supply temperature dropping to the combustion restart temperature, and if the combustion restart condition has not yet been met (STEP26: no), the determination in STEP26 is repeated at a predetermined cycle. On the other hand, if the combustion restart condition is met (STEP26: yes), combustion in burner 3 is restarted (STEP27), and then the process returns to STEP23 to determine again whether or not the rising gradient of the supply temperature has exceeded the judgment gradient (STEP23).

[0057] If the upward gradient of the supply temperature exceeds the judgment gradient (STEP23: yes), then it is determined whether the combustion stop condition has been met (the supply temperature has reached 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 combustion stop condition has not been met (STEP28: no), the process returns to STEP23, and it is determined again whether the upward gradient of the supply temperature has exceeded the judgment gradient (STEP23).

[0058] On the other hand, if the upward gradient of the supply temperature exceeds the judgment gradient and the combustion stop condition is met (STEP28: yes), combustion in burner 3 is temporarily stopped (STEP29), and then the judgment timer is activated (STEP30). In addition, because there is a possibility of overheating abnormality, an additional condition is added to the combustion restart condition (STEP31). That is, in addition to the supply temperature dropping to the combustion restart temperature, the combustion restart condition is set as the temperature difference between the supply temperature and the return temperature becoming smaller than the judgment value.

[0059] In this way, it is determined whether the combustion restart conditions, including the additional conditions, have been met (STEP 32 in Figure 5). If the combustion restart conditions, including the additional conditions, have not yet been met (STEP 32: no), it is determined by the judgment timer whether the predetermined judgment time has elapsed (STEP 33). If the judgment timer has not yet elapsed (STEP 33: no), it returns to STEP 32 and determines again whether the combustion restart conditions, including the additional conditions, have been met (STEP 32).

[0060] Then, if the combustion restart conditions, including the additional conditions, are met before the judgment timer expires (STEP32: yes), the likelihood of an overheating abnormality occurring is low, so the judgment timer is stopped (STEP34), and the overheating abnormality judgment is temporarily terminated. After that, when combustion is restarted in burner 3 (STEP35), the process returns to STEP23, and the above-described process is repeated.

[0061] On the other hand, if the judgment timer elapses without the combustion restart conditions, including the additional conditions, being met (STEP33: yes), it is possible that an overheating abnormality has occurred due to poor circulation of the heat transfer medium in the circulation circuit, because the additional conditions have never been met (the temperature difference between the supply temperature and the return temperature has never been less than the judgment value). In this case, the overheating abnormality is detected (STEP36) and the overheating abnormality is reported (STEP37). After that, the combustion control process shown in Figures 4 and 5 is terminated.

[0062] As explained above, in the first modified heating and hot water supply device 1, in addition to the fact that the additional conditions have never been met (the temperature difference between the supply temperature and the return temperature has never fallen below the judgment value) during the period from the cessation of combustion in the burner 3 until a predetermined judgment time has elapsed, an overheating abnormality is detected when the rising gradient, which is the rate of increase in the supply temperature per unit time, exceeds the judgment gradient.

[0063] 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 can cause an unusually rapid increase in the supply temperature of the heat transfer medium detected by the supply temperature sensor 25. Therefore, if the rise gradient of the supply temperature is greater than or equal to the judgment gradient, 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.

[0064] Furthermore, in the first modified example of the heating and hot water supply system 1, an additional condition is included in the combustion restart condition based on whether the upward gradient of the supply temperature exceeds the judgment gradient. Since it is necessary to wait until the judgment time has elapsed from the cessation of combustion at the burner 3 to confirm whether the additional condition is met (whether the temperature of the heat medium in the circulation circuit is made uniform), the additional condition is included in the combustion restart condition and used to detect overheating abnormalities only when there is a high possibility of overheating abnormalities, such as when the upward gradient of the supply temperature exceeds the judgment gradient. When the possibility of overheating abnormalities is low, the additional condition is not included in the combustion restart condition, thereby maintaining the convenience and comfort of the user of the heating and hot water supply system 1 without delaying the restart of combustion at the burner 3.

[0065] 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), and after combustion in the burner 3 is started (STEP 52), it is determined whether the combustion stop condition has been met (the supply temperature has reached the combustion stop temperature) (STEP 53). If the combustion stop condition has not yet been met (STEP 53: no), the determination in STEP 53 is repeated at a predetermined cycle.

[0066] Then, if the combustion stop condition is met (STEP 53: yes), combustion in burner 3 is temporarily stopped (STEP 54), and the judgment timer is activated (STEP 55). Next, it is determined whether the supply temperature has remained above the abnormal judgment temperature for a specified time or longer (STEP 56). 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 and the combustion stop condition is met, the supply temperature may rise further and exceed the abnormal judgment temperature, which is higher than the combustion stop temperature (see Figure 2(b)). Also, the specified time in the second 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 (combustion stop condition is met) due to air mixed in with the heat medium in the circulation circuit, the supply temperature rarely rises further, and even if the supply temperature exceeds the abnormal judgment temperature, it will quickly decrease if the heat medium in the circulation circuit is circulating.

[0067] Then, if the supply temperature is below the abnormal detection temperature, or if it exceeds the abnormal detection temperature but does not continue for a specified time (STEP56: no), the possibility of an overheating abnormality is low, so the judgment timer is stopped (STEP57) and the overheating abnormality judgment is temporarily terminated. After that, it is determined whether or not the combustion restart condition has been met (STEP58). Similar to the first modified example described above, in the combustion control of burner 3 of the second modified example, the combustion restart condition does not include the additional condition (the temperature difference between the supply temperature and the return temperature becoming smaller than the judgment value) as standard. Therefore, in STEP58, the combustion restart condition is set to the supply temperature dropping to the combustion restart temperature, and if the combustion restart condition has not yet been met (STEP58: no), the judgment in STEP58 is repeated at a predetermined cycle. On the other hand, if the combustion restart condition has been met (STEP58: yes), combustion in burner 3 is restarted (STEP59), and then the process returns to STEP53 to determine again whether or not the combustion stop condition has been met (STEP53).

[0068] In contrast, if the supply temperature exceeds the abnormal judgment temperature and continues for a specified period of time or longer (STEP 56: yes), there is a high possibility of overheating, so an additional condition is added to the combustion restart condition (STEP 60). That is, in addition to the supply temperature dropping to the combustion restart temperature, the combustion restart condition is set as the temperature difference between the supply temperature and the return temperature becoming smaller than the judgment value.

[0069] In this way, it is determined whether the combustion restart conditions, including the additional conditions, have been met (STEP 61 in Figure 7). If the combustion restart conditions, including the additional conditions, have not yet been met (STEP 61: no), it is determined by the judgment timer whether the predetermined judgment time has elapsed (STEP 62). If the judgment timer has not yet elapsed (STEP 62: no), it returns to STEP 61 and determines again whether the combustion restart conditions, including the additional conditions, have been met (STEP 61).

[0070] Then, if the combustion restart conditions, including the additional conditions, are met before the judgment timer expires (STEP61: yes), the likelihood of an overheating abnormality occurring is low, so the judgment timer is stopped (STEP63), and the overheating abnormality judgment is temporarily terminated. After that, when combustion is restarted in burner 3 (STEP64), the process returns to STEP53, and the subsequent processes described above are repeated.

[0071] On the other hand, if the judgment timer elapses without the combustion restart conditions, including the additional conditions, being met (STEP62: yes), it is possible that an overheating abnormality has occurred due to poor circulation of the heat transfer medium in the circulation circuit, because the additional conditions have never been met (the temperature difference between the supply temperature and the return temperature has never been less than the judgment value). In this case, an overheating abnormality is detected (STEP65), and the overheating abnormality is reported (STEP66). After that, the combustion control process shown in Figures 6 and 7 is terminated.

[0072] As explained above, in the second modified heating and hot water supply device 1, in addition to the fact that the additional conditions have not been met (the temperature difference between the supply temperature and the return temperature has never been less than the judgment value) between the cessation of combustion in the burner 3 and the elapsed of a predetermined judgment time, the device is configured to detect an overheating abnormality when, after the cessation of combustion in the burner 3 based on the cessation of combustion due to

[0073] As mentioned above, if an overheating abnormality occurs due to poor circulation of the heat transfer medium in the circulation circuit, some of the heat transfer 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 reaches the combustion stop temperature and the combustion stop condition is met, the supply temperature may rise further, exceeding the abnormality detection temperature, and continue for some time. On the other hand, if combustion in the burner 3 is stopped because the supply temperature reaches the combustion stop temperature (combustion stop condition is met) due to air mixed in with 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 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.

[0074] Furthermore, in the second modified heating and hot water supply system 1, an additional condition is added to the combustion restart condition based on the fact that, after combustion in the burner 3 stops due to the fulfillment of the combustion stop condition, the supply temperature exceeds the abnormal judgment temperature and continues for a specified time or longer. Since it is necessary to wait until the judgment time has elapsed from the stop of combustion in the burner 3 to confirm whether or not the additional condition is met (whether or not the temperature of the heat medium in the circulation circuit is made uniform), the additional condition is included in the combustion restart condition and used to detect overheating abnormalities only when there is a high possibility of overheating abnormalities, such as when the supply temperature exceeds the abnormal judgment temperature and continues for a specified time or longer. When the possibility of overheating abnormalities is low, the additional condition is not included in the combustion restart condition, thereby maintaining the convenience and comfort of the user of the heating and hot water supply system 1 without delaying the restart of combustion in the burner 3.

[0075] 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.

[0076] For example, it is also possible to combine the first and second modified examples described above, and in addition to (a) the additional condition not being met during the period from the cessation of combustion in the burner 3 until a predetermined judgment time has elapsed (the temperature difference between the supply temperature and the return temperature never falling below the judgment value), (b) the rise gradient, which is the rate of increase of the supply temperature per unit time, becoming equal to or greater than the judgment gradient, and (c) after the cessation of combustion in the burner 3 based on the cessation of combustion due to

[0077] 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.

[0078] 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.

[0079] 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.

[0080] 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.

[0081] 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]

[0082] 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 return temperature sensor for detecting the temperature of the heat transfer medium flowing into the heating means, A heating control means for controlling the heating of the aforementioned 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 aforementioned heating control means is Upon commencement of the heat dissipation utilization operation, the heating means is started to heat up. When the temperature detected by the aforementioned supply temperature sensor reaches the heating stop temperature, the heating of the heating means is temporarily stopped, The heating restart condition is when either the temperature detected by the supply temperature sensor or the temperature detected by the return temperature sensor drops to the heating restart temperature, and it is possible to add as an additional condition to the heating restart condition that the temperature difference between the temperature detected by the supply temperature sensor and the temperature detected by the return temperature sensor becomes smaller than a determination value. The overheating abnormality detection means detects the overheating abnormality when the additional condition is included in the heating restart condition, and the detection condition is that the additional condition has not been met during the period from the cessation of heating by the heating means based on the fulfillment of the heating stop condition until a predetermined determination time has elapsed. A heat transfer fluid circulation device characterized by the following features.

2. In the heat transfer fluid circulation device according to claim 1, In addition to the detection conditions, 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.

3. In the heat transfer fluid circulation device according to claim 2, The heating control means includes the additional condition in the heating restart condition based on the fact that the upward slope of the temperature detected by the supply temperature sensor has become equal to or greater than the determination slope. A heat transfer fluid circulation device characterized by the following features.

4. In the heat transfer fluid circulation device according to claim 1 or claim 2, The overheating abnormality detection means detects the overheating abnormality when, in addition to the detection conditions, the heating means stops heating based on the fulfillment of the heating stop conditions, and the temperature detected by the supply temperature sensor remains above the abnormality determination temperature (higher than the heating stop temperature) for a specified period of time or longer, as a detection condition. A heat transfer fluid circulation device characterized by the following features.

5. In the heat transfer fluid circulation device according to claim 4, The heating control means, after stopping heating based on the fulfillment of the heating stop condition, includes the additional condition in the heating restart condition based on the temperature detected by the supply temperature sensor exceeding the abnormal determination temperature and continuing for a specified period of time or longer. A heat transfer fluid circulation device characterized by the following features.

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