SPACE HEATING SYSTEM

REFERENCE TO RELATED APPLICATIONS

[0001]This application claims priority from Japanese Patent Application No. 2024-116958 filed on Jul. 22, 2024. The entire content of the priority application is incorporated herein by reference.

TECHNICAL FIELD

[0002]The disclosure herein relates to a space heating system.

BACKGROUND ART

[0003]US Patent Application Publication No. 2016/0116185 describes a space heating system including: a heat source device configured to heat a heat medium; a space heating terminal configured for space heating by dissipating heat from the heat medium; a space heating circuit including a primary outward path which delivers the heat medium to the heat source device, a primary return path to which the heat medium is delivered from the heat source device, a secondary outward path which delivers the heat medium to the space heating terminal, and a secondary return path to which the heat medium is delivered from the space heating terminal; a fluid mixer fluidly connecting an upstream end of the primary outward path, a downstream end of the primary return path, an upstream end of the secondary outward path, and a downstream end of the secondary return path to each other; a primary return temperature sensor configured to detect a temperature of the heat medium flowing in the primary return path; a secondary outward temperature sensor configured to detect a temperature of the heat medium flowing in the secondary outward path; and a controller.

[0004]In the space heating system, detection failure may occur in the secondary outward temperature sensor. The detection failure herein is a discrepancy being generated between an actual temperature of the heat medium flowing in the secondary outward path and the detected temperature of the secondary outward temperature sensor. The present teachings provide an art configured to allow for determining whether or not detection failure is occurring in a secondary outward temperature sensor.

SUMMARY

[0005]In a first aspect of the technology disclosed herein, a space heating system may comprise: a heat source device configured to heat a heat medium; a space heating terminal configured for space heating by dissipating heat from the heat medium; a heating circuit including a primary outward path to which the heat medium is delivered from the heat source device, a primary return path which delivers the heat medium to the heat source device, a secondary outward path which delivers the heat medium to the space heating terminal, and a secondary return path to which the heat medium is delivered from the space heating terminal; a fluid mixer fluidly connecting a downstream end of the primary outward path, an upstream end of the primary return path, an upstream end of the secondary outward path, and a downstream end of the secondary return path to each other; a primary return temperature sensor configured to detect a temperature of the heat medium flowing in the primary return path; a secondary outward temperature sensor configured to detect a temperature of the heat medium flowing in the secondary outward path; and a controller. The controller may be configured to determine whether detection failure is occurring in the secondary outward temperature sensor based on the temperature detected by the primary return temperature sensor and the temperature detected by the secondary outward temperature sensor.

[0006]According to the above configuration, the controller can determine whether detection failure is occurring in the secondary outward temperature sensor based on the detected temperature of the primary return temperature sensor and the detected temperature of the secondary outward temperature sensor.

[0007]In a second aspect according to the first aspect, the heat source device may comprise a plurality of heat source devices. The primary return temperature sensor may comprise a plurality of primary return temperature sensors, each of the plurality of primary return temperature sensors being disposed for corresponding one of the plurality of heat source devices. The controller may be configured to determine whether detection failure is occurring in the secondary outward temperature sensor based on the temperature detected by one of the plurality of primary return temperature sensors and the temperature detected by the secondary outward temperature sensor.

[0008]In determining whether or not detection failure is occurring in the secondary outward temperature sensor, the controller can be made to refer to the temperatures detected by two or more primary return temperature sensors. This may however complicate the processes executed by the controller. According to the above configuration, in determining whether or not detection failure is occurring in the secondary outward temperature sensor, it suffices to have the controller refer to the detected temperature of one of the primary return temperature sensors. Due to this, the process of the controller can be made relatively simple.

[0009]In a third aspect according to the first aspect, the heat source device may comprise a plurality of heat source devices. The primary return temperature sensor may comprise a plurality of primary return temperature sensors, each of the plurality of primary return temperature sensors being disposed for corresponding one of the plurality of heat source devices. The controller may be configured to determine whether detection failure is occurring in the secondary outward temperature sensor based on the temperatures detected by two or more of the plurality of primary return temperature sensors and the temperature detected by the secondary outward temperature sensor.

[0010]According to the above configuration, in determining whether or not detection failure is occurring in the secondary outward temperature sensor, the controller can be made to refer to the temperatures detected by the two or more primary return temperature sensors. Due to this, as compared to the configuration in which the controller is made to refer to the detected temperature of one of the primary return temperature sensors, determination on whether or not detection failure has occurred at the secondary outward temperature sensor can be made more accurately. For example, the plurality of primary return temperature sensors may include a primary return temperature sensor which detects an abnormal temperature as compared to the other sensor(s) (i.e., primary return temperature sensor in which detection failure is occurring). If the controller is configured to refer only to the detected temperature of one primary return temperature sensor, the controller cannot determine whether or not that primary return temperature sensor is detecting an abnormal temperature as compared to the other one(s). Contrary to this, according to the above configuration, since the controller refers to the temperatures detected by two or more primary return temperature sensors, the controller can specify the primary return temperature sensor which detects an abnormal temperature (i.e., primary return temperature sensor in which detection failure is occurring) as compared to the other sensor(s) by comparing the respective detected temperatures. Due to this, the controller can determine whether or not detection failure is occurring without referring to the detected temperature of the primary return temperature sensor in which detection failure is occurring.

[0011]In a fourth aspect according to any of the first to third aspects, when a temperature difference obtained by subtracting the temperature detected by the primary return temperature sensor from the temperature detected by the secondary outward temperature sensor is less than a predetermined temperature, the controller may determine that detection failure is occurring in the secondary outward temperature sensor.

[0012]The heat medium, which was heated by the heat source device and also is yet to have its heat dissipated by the space heating terminal, flows in the secondary outward path. On the other hand, in the primary return path, the heat medium, which had its heat dissipated by the space heating terminal and also is yet to be heated by the heat source device, flows. Due to this, the heat medium at a high temperature flows in the secondary outward path and the heat medium at a low temperature flows in the primary return path. Given these situations, it is normal that the temperature of the heat medium flowing in the secondary outward path (i.e., detected temperature of the secondary outward temperature sensor) is higher than the temperature of the heat medium flowing in the primary return path (i.e., detected temperature of the primary return temperature sensor), and there is a certain degree of temperature difference between both of them. However, if detection failure is occurring in the secondary outward temperature sensor, the temperature of the heat medium flowing in the secondary outward path could be significantly lower than the actual temperature of the heat medium flowing in the secondary outward path. In this case, the temperature difference obtained by subtracting the detected temperature of the primary return temperature sensor from the detected temperature of the secondary outward temperature sensor becomes lower than usual. According to the above configuration, it can be determined that detection failure is occurring in the secondary outward temperature sensor in such cases. Specifically, when the temperature difference obtained by subtracting the detected temperature of the primary return temperature sensor from the detected temperature of the secondary outward temperature sensor is less than a predetermined temperature, it can be determined that detection failure is occurring in the secondary outward temperature sensor.

[0013]In a fifth aspect according to any of the first to third aspects, when a temperature difference obtained by subtracting the temperature detected by the primary return temperature sensor from the temperature detected by the secondary outward temperature sensor remains less than a predetermined temperature for a predetermined duration or longer, the controller may determine that detection failure is occurring in the secondary outward temperature sensor.

[0014]It is possible to determine that detection failure is occurring in the secondary outward temperature sensor at a timing when the temperature difference obtained by subtracting the detected temperature of the primary return temperature sensor from the detected temperature of the secondary outward temperature sensor becomes less than a predetermined temperature. However, even if there is no detection failure at the secondary outward temperature sensor, the above temperature difference can drop below the predetermined temperature over a short period of time. In a configuration that the occurrence of detection failure is determined at the timing when the temperature difference becomes less than the predetermined temperature, it may make wrong determination in such cases. According to the above configuration, only when the temperature difference remains less than the predetermined temperature for a predetermined duration or longer, it is determined that detection failure is occurring in the secondary outward temperature sensor. Due to this, when the temperature difference remains less than the predetermined temperature only for a short time, it is not determined that detection failure is occurring. Due to this, wrong determination on whether or not detection failure is occurring in the secondary outward temperature sensor can be suppressed.

[0015]In a sixth aspect according to any of the first to fifth aspects, the controller may be configured to execute a first process of controlling a heating capability of the heat source device based on the temperature detected by the secondary outward temperature sensor. When the controller determines that detection failure is occurring in the secondary outward temperature sensor, the controller may not execute the first process.

[0016]If the heating capability of the heat source device is controlled based on the secondary outward temperature sensor in which detection failure is occurring, the heating capability of the heat source device may be set excessively high. According to the above configuration, the heating capability of the heat source device can be suppressed from being controlled based on the secondary outward temperature sensor in which detection failure is occurring. Due to this, the heating capability of the heat source device can be suppressed from being set excessively high.

[0017]In a seventh aspect according to any of the sixth aspect, the controller may be configured to execute a second process of controlling the heating capability of the heat source device without referring to the temperature detected by the secondary outward temperature sensor. When the controller determines that detection failure is occurring in the secondary outward temperature sensor, the controller may execute the second process.

[0018]According to the above configuration, by executing the second process, the controller can control the heating capability of the heat source device without referring to the detected temperature of the secondary outward temperature sensor. Due to this, even if detection failure is occurring in the secondary outward temperature sensor, the heating capability of the heat source device can be controlled without being affected by such detection failure.

BRIEF DESCRIPTION OF DRAWINGS

[0019]FIG. 1 illustrates a schematic configuration view of a space heating system 2 according to an embodiment.

[0020]FIG. 2 schematically illustrates a fluid mixer 20 of the space heating system 2 according to the embodiment.

[0021]FIG. 3 illustrates a flow of heat medium when a first heating operation is executed in a heat source device 100 in the space heating system 2 according to the embodiment.

[0022]FIG. 4 illustrates a flow of heat medium when a second heating operation is executed in the heat source device 100 in the space heating system 2 according to the embodiment.

[0023]FIG. 5 illustrates, in the space heating system 2 according to the embodiment, a flow of the heat medium when a space heating terminal 8a is conducting space heating and heat source devices 400, 500 execute the first heating operation.

[0024]FIG. 6 illustrates a flowchart of processes executed by a parent device controller 102 in the space heating system 2 according to the embodiment.

[0025]FIG. 7 illustrates a flowchart of a first output control process executed by the parent device controller 102 of the space heating system 2 according to the embodiment in the processes shown in FIG. 6.

[0026]FIG. 8 illustrates a flowchart of a second output control process executed by the parent device controller 102 of the space heating system 2 according to the embodiment in the processes shown in FIG. 6.

DETAILED DESCRIPTION

Embodiments

[0027]As illustrated in FIG. 1, a space heating system 2 comprises hot water supply circuits 4 (a part thereof is not illustrated), a space heating circuit 6, five heat source devices 100, 200, 300, 400, 500 and three space heating terminals 8a, 8b, 8c. Water flows through the hot water supply circuits 4. Heat medium (e.g., water, antifreeze) flows through the space heating circuit 6. The heat source devices 100, 200, 300, 400, 500 are arranged in parallel for the space heating circuit 6 and their corresponding hot water supply circuits 4. The heat source devices 100, 200, 300, 400, 500 are configured to heat the water flowing in the hot water supply circuits 4 and are also configured to heat the heat medium flowing in the space heating circuit 6. In the hot water supply circuits 4, faucet(s) and/or bath tub(s) (not illustrated) are arranged. In the space heating circuit 6, the space heating terminals 8a, 8b, 8c are disposed in parallel. The space heating terminals 8a, 8b, 8c include, for example, a floor heating device and a panel heater. The space heating terminals 8a, 8b, 8c conduct space heating by dissipation of heat from the heat medium flowing in the space heating circuit 6. The space heating system 2 is configured to supply the water heated by the heat source device(s) 100, 200, 300, 400, 500 to the faucet(s) and/or bath tub(s) via the hot water supply circuit(s) 4. Further, the space heating system 2 can cause the space heating terminal(s) 8a, 8b, 8c to conduct space heating by delivering the heat medium heated by the heat source device(s) 100, 200, 300, 400, 500 to the space heating terminal(s) 8a, 8b, 8c via the space heating circuit 6.

[0028]The space heating circuit 6 includes a primary outward path 12 to which the heat medium is delivered from each of the heat source devices 100, 200, 300, 400, 500, a primary return path 14 which delivers the heat medium to each of the heat source devices 100, 200, 300, 400, 500, a secondary outward path 16 which delivers the heat medium to each of the space heating terminals 8a, 8b, 8c, and a secondary return path 18 to which the heat medium is delivered from each of the space heating terminals 8a, 8b, 8c. A fluid mixer 20 is disposed between a downstream end of the primary outward path 12, an upstream end of the primary return path 14, an upstream end of the secondary outward path 16, and a downstream end of the secondary return path 18. The fluid mixer 20 allows a difference to be generated between a flow rate of the heat medium flowing in the primary outward path 12 and the primary return path 14 (i.e., total flow rate of the heat medium flowing in the heat source devices 100, 200, 300, 400, 500) and a flow rate of the heat medium flowing in the secondary outward path 16 and the secondary return path 18 (i.e., total flow rate of the heat medium flowing in the space heating terminals 8a, 8b, 8c).

[0029]As illustrated in FIG. 2, the fluid mixer 20 comprises a mixer body 72, an air vent valve 74, a debris disposal valve 76, a primary inlet 78 to which the downstream end of the primary outward path 12 is connected, a primary outlet 80 to which an upstream end of the primary return path 14 is connected, a secondary outlet 82 to which an upstream end of the secondary outward path 16 is connected, and a secondary inlet 84 to which the downstream end of the secondary return path 18 is connected. The mixer body 72 has a substantially cylindrical shape extending between the air vent valve 74 and the debris disposal valve 76. The fluid mixer 20 is oriented such that an axial direction of the mixer body 72 is along a vertical direction. The fluid mixer 20 is oriented such that the air vent valve 74 is positioned at a top in the vertical direction of the mixer body 72 and the debris disposal valve 76 is positioned at a bottom in the vertical direction of the mixer body 72. By releasing the air vent valve 74, air accumulated in the fluid mixer 20 can be discharged outside the fluid mixer 20. By releasing the debris disposal valve 76, debris accumulated in the fluid mixer 20 can be discharged outside the fluid mixer 20. The primary inlet 78 and the secondary outlet 82 are disposed so as to face each other via inside of the mixer body 72. Due to this, the heat medium following from the primary outward path 12 into the primary inlet 78 can easily flow through the secondary outlet 82 to the secondary outward path 16. Similarly, the secondary inlet 84 and the primary outlet 80 are disposed so as to face each other via the inside of the mixer body 72. Due to this, the heat medium flowing from the secondary return path 18 into the secondary inlet 84 can easily flow through the primary outlet 80 to the primary return path 14.

[0030]The heat medium at a high temperature, which was heated by the heat source devices 100, 200, 300, 400, 500 and is yet to have its heat dissipated by the space heating terminals 8a, 8b, 8c, flows in the primary outward path 12. Accordingly, the high-temperature heat medium flows into the primary inlet 78. Also, the heat medium at a low temperature, which had its heat dissipated by the space heating terminals 8a, 8b, 8c and is yet to be heated by the heat source devices 100, 200, 300, 400, 500, flows in the secondary return path 18. Accordingly, the low-temperature heat medium flows into the secondary inlet 84. Inside the mixer body 72, a phenomenon where the high-temperature heat medium ascends and the low-temperature descends (so-called convection) occurs. In the present embodiment, the primary inlet 78 and the secondary outlet 82 are connected to the top of the mixer body 72, and the secondary inlet 84 and the primary outlet 80 are connected to the bottom of the mixer body 72. Due to this, the high-temperature heat medium flowing from the primary outward path 12 into the primary inlet 78 can easily flow through the secondary outlet 82 to the secondary outward path 16. The low-temperature heat medium flowing from the secondary return path 18 into the secondary inlet 84 can easily flow through the primary outlet 80 to the primary return path 14.

[0031]The space heating circuit 6 illustrated in FIG. 1 further includes terminal paths 22a, 22b, 22c corresponding respectively to the space heating terminals 8a, 8b, 8c. An upstream end of each of the terminal paths 22a, 22b, 22c is connected to the secondary outward path 16. A downstream end of each of the terminal paths 22a, 22b, 22c is connected to the secondary return path 18. Terminal pumps 24a, 24b, 24c are disposed on the terminal paths 22a, 22b, 22c. The terminal pumps 24a, 24b, 24c suction the heat medium in the secondary outward path 16 into the terminal paths 22a, 22b, 22c and deliver the heat medium in the terminal paths 22a, 22b, 22c to the secondary return path 18. By operating the terminal pumps 24a, 24b, 24c, the heat medium is delivered to the space heating terminals 8a, 8b, 8c, and space heating by the space heating terminals 8a, 8b, 8c is conducted.

[0032]The space heating system 2 comprises thermostats 26a, 26b, 26c corresponding to the space heating terminals 8a, 8b, 8c. The thermostats 26a, 26b, 26c each detect a temperature of a space in which its corresponding one of the space heating terminals 8a, 8b, 8c is installed, that is, a space which the corresponding space heating terminal 8a, 8b, 8c is to heat (e.g., inside a house). The thermostats 26a, 26b, 26c also output a heating ON signal for starting space heating by the space heating terminals 8a, 8b, 8c when the detected temperature falls below a predetermined heating ON threshold (e.g., 20° C.), and output a heating OFF signal for terminating the space heating by the space heating terminals 8a, 8b, 8c when the detected temperature exceeds a predetermined heating OFF threshold (e.g., 25° C.). In the present teachings, the heating ON signal and the heating OFF signal may also be referred to as “heating signal” collectively.

[0033]The heat source device 100 comprises a burner 32, a first heat exchanger 34 configured to heat the heat medium by combustion heat of the burner 32, a primary return branch path 36 connecting a fluid inlet of the first heat exchanger 34 and the primary return path 14, a primary outward branch path 38 connecting a fluid outlet of the first heat exchanger 34 and the primary outward path 12, a heat source pump 40 disposed on the primary return branch path 36, a bypass path 42 configured to bypass the first heat exchanger 34 and the heat source pump 40 to connect the primary return branch path 36 and the primary outward branch path 38, a second heat exchanger 44 configured to heat water flowing in the hot water supply circuits 4 by heat exchange with the heat medium flowing in the bypass path 42, and a three-way valve 46 disposed at a connection between the primary outward branch path 38 and the bypass path 42. The three-way valve 46 is configured to switch between a first state (see FIG. 3) of delivering the heat medium flowing out of the first heat exchanger 34 through the primary outward branch path 38 to the primary outward path 12 and a second state (see FIG. 4) of delivering the heat medium flowing out of the first heat exchanger 34 through the primary outward branch path 38 to the bypass path 42. The three-way valve 46 is configured to switch a destination of the heat medium flowing out of the first heat exchanger 34 between the bypass path 42 and the primary outward path 12. Also, a primary return thermistor 48 configured to detect the temperature of the heat medium just before being heated by the first heat exchanger 34 is disposed on the primary return branch path 36. A primary outward thermistor 50 configured to detect the temperature of the heat medium just after being heated by the first heat exchanger 34 is disposed on the primary outward branch path 38.

[0034]As illustrated in FIG. 3, the heat source device 100 is configured to execute a first heating operation of heating the heat medium flowing in the space heating circuit 6 by firstly setting the three-way valve 46 in the first state, causing the burner 32 to ignite, and operating the heat source pump 40. When the first heating operation is executed, the heat medium in the primary return path 14 passes sequentially through the primary return branch path 36, the first heat exchanger 34, and the primary outward branch path 38, and is delivered to the primary outward path 12. When the heat medium passes through the first heat exchanger 34, the heat medium is heated by the combustion heat of the burner 32.

[0035]As illustrated in FIG. 4, the heat source device 100 is configured to execute a second heating operation of heating the water flowing in the hot water supply circuits 4 by firstly setting the three-way valve 46 in the second state, causing the burner 32 to ignite, and operating the heat source pump 40. When the second heating operation is executed, the heat medium is circulated through the primary return branch path 36, the first heat exchanger 34, the primary outward branch path 38, and the bypass path 42 (i.e., the second heat exchanger 44). When the heat medium passes through the first heat exchanger 34, the heat medium is heated by the combustion heat of the burner 32, and when the heat medium passes through the second heat exchanger 44, the heat medium releases its heat to the water flowing in the hot water supply circuits 4. Due to this, the water flowing in the hot water supply circuits 4 is heated.

[0036]The heat source device 100 further comprises a heat source controller 102 including a CPU, ROM, RAM, etc. The ROM stores various types of operation programs therein. The RAM temporarily stores various signal(s) inputted to the heat source controller 102 and various types of data generated in the course of the CPU executing processes. The heat source controller 102 controls respective constituent features of the heat source device 100 by the CPU executing processes based on the information stored in the ROM and RAM. The heat source controller 102 is configured to set a setting value regarding an output of the burner 32 (also called “output setting value”). The output setting value is set to one of five steps, for example, “1”, “2”, “3”, “4”, “5”. The heat source controller 102 controls the output of the burner 32 based on the output setting value when causing the burner 32 to ignite (e.g., when executing the first heating operation). The heat source controller 102 causes the burner 32 to output at a greater degree for a greater output setting value.

[0037]Each of the heat source devices 200, 300, 400, 500 shown in FIG. 1 comprises the same constituent features as those of the heat source device 100. For example, each of heat source controllers 202, 302, 402, 502 which the heat source devices 200, 300, 400, 500 respectively comprise is a constituent feature corresponding to the heat source controller 102, and controls the constituent features of its corresponding heat source device 200, 300, 400, 500. Other constituent features which each of the heat source devices 200, 300, 400, 500 comprises are not given reference signs, for simplification.

[0038]The heat source controller 102 of the heat source device 100 is connected with a first signal line 62a for communicating with the thermostat 26a and a second signal line 64a for communicating with the terminal pump 24a. The heating signals outputted by the thermostat 26a are transmitted through the first signal line 62a to the heat source controller 102. Further, the heat source controller 102 controls operation of the terminal pump 24a by sending an instruction to the terminal pump 24a through the second signal line 64a. For example, when the heating ON signal is transmitted from the thermostat 26a, the heat source controller 102 causes the terminal pump 24a to operate. Due to this, the heat medium starts to be supplied to the space heating terminal 8a corresponding to the thermostat 26a, by which space heating by the space heating terminal 8a is started. Thereafter, when the heating OFF signal is transmitted from the thermostat 26a, the heat source controller 102 causes the terminal pump 24a to stop operating. Due to this, the supply of the heat medium to the space heating terminal 8a corresponding to the thermostat 26a ends, by which the space heating by the space heating terminal 8a ends.

[0039]The heat source controller 202 of the heat source device 200 is connected with a first signal line 62b for communicating with the thermostat 26b and a second signal line 64b for communicating with the terminal pump 24b. A relationship between the heat source controller 202, the thermostat 26b, the terminal pump 24b, and the space heating terminal 8b is same as the aforementioned relationship between the heat source controller 102, the thermostat 26a, the terminal pump 24a, and the space heating terminal 8a. Also, the heat source controller 302 of the heat source device 300 is connected with a first signal line 62c for communicating with the thermostat 26c and a second signal line 64c for communicating with the terminal pump 24c. A relationship between the heat source controller 302, the thermostat 26c, the terminal pump 24c, and the space heating terminal 8c is the same as the aforementioned relationship between the heat source controller 102, the thermostat 26a, the terminal pump 24a, and the space heating terminal 8a.

[0040]In the present embodiment, among the heat source controllers 102, 202, 302, 402, 502, the heat source controller 102 functions as a parent device controller, and the remaining heat source controllers 202, 302, 402, 502 function as child device controllers configured to communicate with the parent device controller. Hereinafter, the heat source controller 102 will also be referred to as “parent device controller 102”, and the heat source controllers 202, 302, 402, 502 will also be referred to as “child device controllers 202, 302, 402, 502”. The parent device controller 102 and the child device controllers 202, 302, 402, 502 control the space heating system 2 by cooperating with each other. For example, the parent device controller 102 sends a signal regarding operations of the heat source devices 200, 300, 400, 500 (e.g., instruction for starting the first heating operation) to the child device controllers 202, 302, 402, 502. Each of the child device controllers 202, 302, 402, 502 sends information regarding the heat source device 200, 300, 400, 500 which each of the child device controllers 202, 302, 402, 502 controls (e.g., temperature detected by the primary return thermistor 48) to the parent device controller 102.

[0041]The space heating system 2 further comprises a remote controller 10 configured to communicate with the parent device controller 102. The remote controller 10 is operated by a user. The user can operate the remote controller 10 so as to switch ON/OFF of power of the space heating system 2 and/or perform various settings on the space heating system 2. For example, the user can set a space heating target temperature (i.e., temperature of the heat medium flowing in the space heating circuit 6) of the space heating terminals 8a, 8b, 8c via the remote controller 10.

[0042]The parent device controller 102 is configured to communicate with a secondary outward thermistor 52 disposed on the secondary outward path 16. The secondary outward thermistor 52 detects the temperature of the heat medium flowing in the secondary outward path 16 and sends the detected temperature to the parent device controller 102.

[0043]The parent device controller 102 memorizes the space heating signal that was most recently transmitted to the parent device controller 102 (i.e., signal which the thermostat 26a outputted most recently). Also, the parent device controller 102 obtains the heating signals most recently transmitted to the child device controllers 202, 302 (i.e., heating signals which the thermostats 26b, 26c outputted most recently) through communication with the child device controllers 202, 302, and memorizes those signals. Due to this, the parent device controller 102 can acknowledge the heating signals which the thermostats 26a, 26b, 26c most recently outputted. The heating signal which each of the thermostats 26a, 26b, 26c outputted most recently indicates whether the space heating is ongoing at the corresponding space heating terminal 8a, 8b, 8c or not. When the heating signal which one of the thermostats 26a, 26b, 26c most recently outputted is the heating ON signal, the space heating is ongoing at the space heating terminal 8a, 8b, 8c corresponding to that thermostat 26a, 26b, 26c. When the heating signal which one of the thermostats 26a, 26b, 26c most recently outputted is the heating OFF signal, the space heating is not ongoing at the space heating terminal 8a, 8b, 8c corresponding to that thermostat 26a, 26b, 26c.

[0044]When at least one of the thermostats 26a, 26b, 26c has most recently outputted the heating ON signal, because the space heating is ongoing at the at least one of the space heating terminals 8a, 8b, 8c, at least one of the heat source devices 100, 200, 300, 400, 500 should be caused to execute the first heating operation (see FIG. 3) in order to supply the heated heat medium to the operating space heating terminal 8a, 8b, 8c. Accordingly, when at least one of the thermostats 26a, 26b, 26c has outputted the heating ON signal most recently, the parent device controller 102 causes at least one of the heat source devices 100, 200, 300, 400, 500 to execute the first heating operation. FIG. 5 illustrates an example where the thermostat 26a outputs the heating ON signal and accordingly the space heating terminal 8a performs space heating, and the heat source devices 400, 500 execute the first heating operation.

[0045]When the first heating operation is performed in at least one of the heat source devices 100, 200, 300, 400, 500, the parent device controller 102 repeatedly executes a process illustrated in FIG. 6. The process illustrated in FIG. 6 is a process of determining whether detection failure is occurring or not based on the detected temperature of the primary return thermistor 48 (also referred to as detected primary return temperature T1) and the detected temperature of the secondary outward thermistor 52 (also referred to as detected secondary outward temperature T2) and switching how to control the output of the burner(s) 32 according to its determination results.

[0046]In S2, the parent device controller 102 obtains the detected primary return temperature(s) T1 at the heat source device(s) which are executing the first heating operation. In the example of FIG. 5, the parent device controller 102 communicates with the child device controllers 402, 502 of the heat source devices 400, 500 executing the first heating operation, and obtains the detected primary return temperatures T1 of the heat source devices 400, 500. Also, the parent device controller 102 obtains the detected secondary outward temperature T2 from the secondary outward thermistor 52. After S2, the process proceeds to S4.

[0047]In S4, the parent device controller 102 determines whether the detected primary return temperature(s) T1 obtained in S2 contain an abnormal value or not. In the example of FIG. 5, the plurality of detected primary return temperatures T1 (i.e., the detected primary return temperature T1 at the heat source device 400 and the detected primary return temperature T1 at the heat source device 500) is obtained. In this case, the parent device controller 102 determines whether the plurality of detected primary return temperatures T1 contains a temperature abnormally higher than the other (or temperature abnormally lower than the other) or not. When the obtained detected primary return temperatures T1 contain the abnormal value, the process proceeds to S6.

[0048]In S6, the parent device controller 102 excludes the abnormal value specified in S4 from among the detected primary return temperature(s) T1 obtained in S2. In the subsequent process (process from S8 to S18), the parent device controller 102 refers to the detected primary return temperature T1 from which the abnormal value was excluded. Alternatively, with respect to the primary return thermistor 48 indicating the abnormal value specified in S4, the parent device controller 102 may determine that detection failure is occurring in that primary return thermistor 48.

[0049]After S6 or when the detected primary return temperature(s) T1 obtained in S2 do not contain an abnormal value (i.e., in case of NO in S4), the process proceeds to S8. In S8, the parent device controller 102 determines whether the detected secondary outward temperature T2 with a predetermined buffer temperature (e.g., Tb=10° C.) added thereto is equal to or higher than the detected primary return temperature T1. That is, the parent device controller 102 determines whether T2+Tb≥T1 is satisfied or not. Here, when there are plural detected primary return temperatures T1, the parent device controller 102 determines whether T2+Tb≥T1 is satisfied or not for each of the plural detected primary return temperatures T1. The parent device controller 102 determines YES when T2+Tb≥T1 is satisfied for each of the plural detected primary return temperatures T1. The parent device controller 102 determines NO when T2+Tb≥T1 is not satisfied (i.e., when T2+Tb<T1 is satisfied) for at least one of the plural detected primary return temperatures T1. In another example, the parent device controller 102 may determine YES when T2+Tb≥T1 is satisfied for at least one of the plural detected primary return temperatures T1. The parent device controller 102 may determine NO when T2+Tb≥T1 is not satisfied (i.e., when T2+Tb<T1 is satisfied) for each of the plural detected primary return temperatures T1.

[0050]When YES is determined in S8, the process proceeds to S10. In S10, the parent device controller 102 determines that detection failure is not occurring in the secondary outward thermistor 52. After S10, the process proceeds to S12.

[0051]In S12, the parent device controller 102 executes a first output control process illustrated in FIG. 7. Although not illustrated, the first output control process is a process for controlling the output of the burner(s) 32 based on the detected secondary outward temperature T2. After S12, the process illustrated in FIG. 6 ends.

[0052]When NO is determined in S8, the process proceeds to S14. In S14, the parent device controller 102 determines whether T2+Tb<T1 remains satisfied (i.e., NO is determined in S8) for a predetermined duration or longer. When T2+Tb<T1 does not remain satisfied (i.e., NO is determined in S8) for a predetermined duration or longer (in case of NO), the process proceeds to S8. When T2+Tb<T1 remains satisfied (i.e., NO is determined in S8) for a predetermined duration or longer (in case of YES), the process proceeds to S16.

[0053]In S16, the parent device controller 102 determines that detection failure is occurring in the secondary outward thermistor 52. After S16, the process proceeds to S18.

[0054]In S18, the parent device controller 102 executes a second output control process illustrated in FIG. 8. Although details will be described later, the second output control process is a process of controlling the output of the burner(s) 32 without referring to the detected secondary outward temperature T2. After S18, the process illustrated in FIG. 6 ends.

[0055](Principle for Determining Detection Failure)

[0056]In the secondary outward path 16 illustrated in FIG. 1, a high-temperature heat medium, which was heated by the heat source devices 100, 200, 300, 400, 500 and also is yet to have its heat dissipated by the space heating terminals 8a, 8b, 8c, flows. On the other hand, in the primary return path 14, a low-temperature heat medium, which had its heat dissipated by the space heating terminals 8a, 8b, 8c and also is yet to be heated by the heat source devices 100, 200, 300, 400, 500, flows. Given these situations, it is normal that the detected secondary outward temperature T2 (i.e., detected temperature of the secondary outward thermistor 52) is higher than the detected primary return temperature T1 (i.e., detected temperature of the primary return thermistor 48). That is, it is normal that T2≥T1 is satisfied. However, if detection failure is occurring in the secondary outward thermistor 52, the detected secondary outward temperature T2 could be significantly lower than the actual temperature of the heat medium flowing in the secondary outward path 16 and the detected secondary outward temperature T2 could be lower than the detected primary return temperature T1 (i.e., T2<T1 stands true). Given these situations, in the present embodiment, when T2+Tb<T1 remains satisfied for a predetermined duration or longer, it is determined that detection failure is occurring in the secondary outward thermistor 52 (see S8, S14, S16 in FIG. 6). Here, the buffer temperature Tb may be set to zero, may be set to a value more than zero, or may be set to a value smaller than zero.

(First Output Control Process; FIG. 7 )

[0057]The first output control process is executed in S12 in the process illustrated in FIG. 6.

[0058]In S32, the parent device controller 102 determines whether a temperature obtained by subtracting the detected secondary outward temperature T2 (i.e., detected temperature of the secondary outward thermistor 52) from a secondary outward target temperature exceeds a predetermined first increase threshold (e.g., 5° C.). The secondary outward target temperature herein mentioned is a target temperature of the heat medium flowing in the secondary outward path 16. The secondary outward target temperature is specified based on the space heating target temperature which was set by the user through the remote controller 10, for example. When the temperature obtained by subtracting the detected secondary outward temperature T2 from the secondary outward target temperature exceeds the first increase threshold (in case of YES), the process proceeds to S34.

[0059]In S34, the parent device controller 102 causes heat source device(s) which are executing the first heating operation to increase the output setting value for the burner(s) 32. In the example of FIG. 5, the parent device controller 102 sends an instruction for increasing the output setting value of the burners 32 to the child device controllers 402, 502. The child device controllers 402, 502 increase the output setting values of the burners 32 which the child device controllers 402, 502 respectively control in accordance with the instruction from the parent device controller 102. After S34, the process returns to S32.

[0060]In S32, when the temperature obtained by subtracting the detected secondary outward temperature T2 from the secondary outward target temperature is equal to or less than the first increase threshold (in case of NO), the process proceeds to S36. In S36, the parent device controller 102 determines whether the temperature obtained by subtracting the detected secondary outward temperature T2 from the secondary outward target temperature falls below a predetermined first decrease threshold (e.g., −5° C.) or not. When the temperature obtained by subtracting the detected secondary outward temperature T2 from the secondary outward target temperature has fallen below the first decrease threshold (in case of YES), the process proceeds to S38.

[0061]In S38, the parent device controller 102 reduces the output setting value(s) of the burner(s) 32. In the example of FIG. 5, the parent device controller 102 sends an instruction to decrease the output setting values of the burners 32 to the child device controllers 402, 502. The child device controllers 402, 502 decrease the output setting values of the burners 32 which the child device controllers 402, 502 respectively control in accordance with the instruction from the parent device controller 102. After S38, the process returns to S36.

[0062]In S36, when the temperature obtained by subtracting the detected secondary outward temperature T2 from the secondary outward target temperature is equal to or more than the first decrease threshold (in case of NO), the process illustrated in FIG. 7 ends.

[0063]According to the first output control process, when the detected secondary outward temperature T2 significantly falls below the secondary outward target temperature (i.e., in case of YES in S32), the output setting value(s) of the burner(s) 32 are increased (see S34), by which heat quantity given by the burner(s) 32 to the heat medium increases, resulting in an increase in the temperature of the heat medium flowing in the secondary outward path 16. Also, according to the first output control process, when the detected secondary outward temperature T2 is significantly higher than the secondary outward target temperature (i.e., in case of YES in S36), the output setting value(s) of the burner(s) 32 are decreased (see S38), by which the heat quantity given by the burner(s) 32 to the heat medium decreases, resulting in a decrease in the temperature of the heat medium flowing in the secondary outward path 16. As such, according to the first output control process, the temperature of the heat medium flowing in the secondary outward path 16 can be maintained at or near the secondary outward target temperature.

(Second Output Control Process; FIG. 8 )

[0064]The second output control process is executed in S18 in the process illustrated in FIG. 6.

[0065]In S52, the parent device controller 102 determines whether a temperature obtained by subtracting a detected primary outward temperature T3 (i.e., detected temperature of the primary outward thermistor 50) from a target primary outward temperature exceeds a predetermined second increase threshold (e.g., 5° C.) or not. The target primary outward temperature herein is a target temperature of the heat medium flowing in the primary outward path 12. The target primary outward temperature is specified based on the space heating target temperature which was set by the user through the remote controller 10. When the temperature obtained by subtracting the detected primary outward temperature T3 from the target primary outward temperature exceeds the second increase threshold (in case of YES), the process proceeds to S54.

[0066]In S54, the parent device controller 102 causes the heat source device(s) which are now executing the first heating operation to increase the output setting value(s) of the burner(s) 32. In the example of FIG. 5, the parent device controller 102 sends an instruction of increasing the output setting values of the burners 32 to the child device controllers 402, 502. The child device controllers 402, 502 increase the output setting values of the burners 32 which the child device controllers 402, 502 respectively control in accordance with the instruction from the parent device controller 102. After S54, the process returns to S52.

[0067]In S52, when the temperature obtained by subtracting the detected primary outward temperature T3 from the target primary outward temperature is equal to or less than the second increase threshold (in case of NO), the process proceeds to S56. In S56, the parent device controller 102 determines whether the temperature obtained by subtracting the detected primary outward temperature T3 from the target primary outward temperature falls below a predetermined second decrease threshold (e.g., −5° C.) or not. When the temperature obtained by subtracting the detected primary outward temperature T3 from the target primary outward temperature falls below the second decrease threshold (in case of YES), the process proceeds to S58.

[0068]In S58, the parent device controller 102 decreases the output setting value(s) of the burner(s) 32. In the example of FIG. 5, the parent device controller 102 sends an instruction of decreasing the output setting values of the burners 32 to the child device controllers 402, 502. The child device controllers 402, 502 decrease the output setting values of the burners 32 which the child device controllers 402, 502 respectively control in accordance with the instruction from the parent device controller 102. After S58, the process returns to S56.

[0069]In S56, when the temperature obtained by subtracting the detected primary outward temperature T3 from the target primary outward temperature is equal to or more than the second decrease threshold (in case of NO), the process illustrated in FIG. 8 ends.

[0070]According to the second output control process, when the detected primary outward temperature T3 significantly falls below the target primary outward temperature (i.e., in case of YES in S52), the output setting value(s) of the burner(s) 32 increase (see S54), by which the heat quantity given to the heat medium by the burner(s) 32 increases, resulting in an increase in the temperature of the heat medium flowing in the primary outward path 12. Also, according to the second output control process, when the detected primary outward temperature T3 significantly exceeds the target primary outward temperature (i.e., in case of YES in S56), the output setting value(s) of the burner(s) 32 decreases (see S58), by which the heat quantity given to the heat medium by the burner(s) 32 decreases, resulting in a decrease in the temperature of the heat medium flowing in the primary outward path 12. As such, according to the second output control process, the temperature of the heat medium flowing in the primary outward path 12 can be maintained at or near the target primary outward temperature.

[0071]According to the second output control process, the output of the burner(s) 32 can be controlled without referring to the detected secondary outward temperature T2 (i.e., detected temperature of the secondary outward thermistor 52). Due to this, even if detection failure is occurring in the secondary outward thermistor 52, the output of the burner(s) 32 can be controlled without being affected by the detection failure.

(Modifications)

[0072]The number of heat source devices which the space heating system 2 comprises may not be limited to five, but may be one, two, three, four, or six or more.

[0073]The number of space heating terminals which the space heating system 2 comprises may not be limited to three, but may be one, two, or four or more.

[0074](See FIG. 1) The space heating system 2 may further comprise a temperature sensor disposed on the primary return path 14 and configured to detect the temperature of the heat medium flowing in the primary return path 14. In this example, in S2 in the process illustrated in FIG. 6, instead of the parent device controller 102 obtaining the detected temperature of the primary return thermistor 48 as the detected primary return temperature T1, a detected temperature of the temperature sensor disposed on the primary return path 14 may be obtained as the detected primary return temperature T1.

[0075](See FIG. 1) The secondary outward thermistor 52 may be disposed upstream of the space heating terminals 8a, 8b, 8c in the terminal paths 22a, 22b, 22c.

[0076](See FIG. 2) The fluid mixer 20 may be oriented such that the axial direction of the mixer body 72 is along a horizontal direction. In that case, the fluid mixer 20 may not comprise the debris disposal valve 76 and the air vent valve 74. Also, the mixer body 72 may have a shape other than the cylindrical shape (e.g., may have a sphere shape, circular cone shape). Also, the positional relationship between the primary inlet 78, the primary outlet 80, the secondary outlet 82, and the secondary inlet 84 may differ from that in the embodiment. For example, the primary inlet 78, the primary outlet 80, the secondary outlet 82, and the secondary inlet 84 may not be arranged to face each other. Alternatively, the primary inlet 78 and the primary outlet 80 may be arranged to face each other through the inside of the mixer body 72. The secondary outlet 82 and the secondary inlet 84 may be arranged to face each other through the inside of the mixer body 72.

[0077](See FIG. 6) In S2 in the process illustrated in FIG. 6, even if there are plural heat source devices which are executing the first heating operation, the parent device controller 102 may obtain one detected primary return temperature T1 from among the plurality of detected primary return temperatures T1 in this plural heat source devices. The parent device controller 102 may execute the subsequent process (process from S4 to S18) based on the one detected primary return temperature T1.

[0078](See FIG. 6) S14 may be skipped in the process illustrated in FIG. 6. That is, when T2+Tb<T1 (i.e., when NO is determined in S8), the parent device controller 102 may immediately determine that detection failure is occurring in the secondary outward thermistor 52.

[0079](See FIG. 6) In S18 in the process illustrated in FIG. 6, instead of executing the second output control process (see FIG. 8), the parent device controller 102 may cause the heat source device(s) which are executing the first heating operation to suspend the first heating operation. Then, the parent device controller 102 may notify the user that detection failure is occurring in the secondary outward thermistor 52, for example through the remote controller 10.

[0080](See FIG. 1) The space heating system 2 may further comprise an outside-air temperature configured to detect an outside-air temperature (e.g., temperature outside a house in which the space heating system 2 is installed). The parent device controller 102 may be configured to change the output setting value(s) of the burner(s) 32 based on the outside-air temperature obtained from the outside-air temperature sensor in the first output control process illustrated in FIG. 7 and/or the second output control process illustrated in FIG. 8. For example, when increasing the output of the burner(s) 32 in S34 in the first output control process, the parent device controller 102 may be configured to increase the output setting value(s) of the burner(s) 32 by two levels when the outside-air temperature obtained from the outside-air temperature sensor is low, and to increase the output setting value(s) of the burner(s) 32 by one level when the outside-air temperature is high.

[0081](See FIG. 1) The space heating system 2 may comprise terminal remote controller(s) (not illustrated) corresponding to the space heating terminals 8a, 8b, 8c instead of or in addition to the thermostats 26a, 26b, 26c. The user may be able to instruct start/termination of the space heating by the space heating terminals 8a, 8b, 8c through the terminal remote controller(s).

[0082]In the second output control process illustrated in FIG. 8, the parent device controller 102 may increase/decrease the output setting value(s) of the burner(s) 32 based on the detected primary return temperature T1 instead of increasing/decreasing the output setting value(s) of the burner(s) 32 based on the detected primary outward temperature T3. Specifically, in S52 of the second output control process, the parent device controller 102 may determine whether a temperature obtained by subtracting the detected primary return temperature T1 from a primary return target temperature (i.e., target temperature of the heat medium flowing in the primary return path 14) exceeds the second increase threshold or not. In S56 of the second output control process, the parent device controller 102 may determine whether the temperature obtained by subtracting the detected primary return temperature T1 from the primary return target temperature falls below the second decrease threshold or not.

(Correspondence Relationships)

[0083]In the embodiment, the hot water supply circuits 4 are an example of “hot water supply circuit”. The space heating circuit 6 is an example for “space heating circuit”. The space heating terminals 8a, 8b, 8c are an example for “space heating terminal”. The heat source devices 100, 200, 300, 400, 500 are examples for “heat source device”. The heat source controllers 102, 202, 302, 402, 502 are examples for “controller”. The primary outward path 12 is an example for “primary outward path”. The primary return path 14 is an example for “primary return path”. The secondary outward path 16 is an example for “secondary outward path”. The secondary return path 18 is an example for “secondary return path”. The fluid mixer 20 is an example for “fluid mixer”. The primary return thermistor(s) 48 is an example for “primary return temperature sensor”. The detected primary return temperature T1 is an example for “temperature detected by the primary return temperature sensor”. The secondary outward thermistor 52 is an example for “secondary outward temperature sensor”. The detected secondary outward temperature T2 is an example for “temperature detected by the secondary outward temperature sensor”. The state where T2+Tb<T1 is satisfied is equivalent to the state where T2−T1<−Tb is satisfied, and is an example for “a temperature difference obtained by subtracting the temperature detected by the primary return temperature sensor from the temperature detected by the secondary outward temperature sensor remains less than a predetermined temperature”. The output of the burner(s) 32 is an example for “heating capability of the heat source device”. The first output control process is an example for “first process”. The second output control process is an example for “second process”.

[0084]Specific examples of the present invention have been described in detail, however, these are mere exemplary indications and thus do not limit the scope of the claims. The art described in the claims includes modifications and variations of the specific examples presented above. Technical features described in the description and the drawings may technically be useful alone or in various combinations, and are not limited to the combinations as originally claimed. Further, the art described in the description and the drawings may concurrently achieve a plurality of aims, and technical significance thereof resides in achieving any one of such aims.