SPACE AND WATER HEATING APPARATUS

Abstract

To detect an abnormality without a limit switch, a space and water heating apparatus includes external and internal circulation channels, including a shared portion, to respectively circulate a heating medium through space heating equipment (20) and a water-heating heat exchanger (28), a first temperature sensor (25) that detects a temperature of the heating medium heated in the shared portion, and a second temperature sensor (35) that detects a temperature of hot water produced with the heat exchanger. A switch controller (40) controls a circulation switcher (29) to switch between the circulation channels. A storage (40a) prestores, in association with a mode of the circulation switcher, a detection value from the second temperature sensor expected when the circulation switcher operates normally. An abnormality detector (40) detects an abnormality in the circulation switcher in response to the actual detection value being different from the expected detection value associated with the instructed mode.

Claims

1. A space and water heating apparatus for performing a space heating operation and a water heating operation, the space heating operation being an operation in which a heating medium is circulated through space heating equipment for space heating, the water heating operation being an operation in which the heating medium circulated in the space heating operation is circulated through a water-heating heat exchanger to heat, by heat exchange with the heating medium, water supplied to the water-heating heat exchanger to produce hot water, the space and water heating apparatus comprising: an external circulation channel configured to circulate the heating medium through the space heating equipment; an internal circulation channel configured to circulate the heating medium through the water-heating heat exchanger, the internal circulation channel including a shared portion shared with the external circulation channel; a circulation pump in the shared portion, the circulation pump being configured to pump the heating medium in a predetermined direction; a heater in the shared portion, the heater being configured to heat the heating medium; a first temperature sensor downstream from the heater in the shared portion, the first temperature sensor being configured to detect a temperature of the heating medium heated by the heater; a circulation switcher configured to switch between a space-heating circulation mode in which the heating medium is circulated along the external circulation channel and a water-heating circulation mode in which the heating medium is circulated along the internal circulation channel; a switch controller configured to control switching performed by the circulation switcher; a second temperature sensor configured to detect a temperature of the hot water produced with heat from the water-heating heat exchanger; a storage configured to prestore an expected detection value associated with a switching mode of the circulation switcher, the expected detection value being a detection value from the second temperature sensor expected when the circulation switcher operates normally; and an abnormality detector configured to detect an abnormality in the circulation switcher in response to the detection value from the second temperature sensor being different from the expected detection value associated with the switching mode of the circulation switcher indicated by an instruction from the switch controller.

2. The space and water heating apparatus according to claim 1, wherein the expected detection value associated with the space-heating circulation mode is less than a predetermined threshold, and when an instruction from the switch controller indicates the space-heating circulation mode, the abnormality detector detects an abnormality in the circulation switcher in response to the detection value from the second temperature sensor being greater than or equal to the threshold.

3. The space and water heating apparatus according to claim 2, wherein the threshold differs based on an initial detection value and is greater for a greater initial detection value, and the initial detection value is the detection value from the second temperature sensor detected at a time at which an instruction from the switch controller indicating the space-heating circulation mode is provided.

4. The space and water heating apparatus according to claim 1, wherein the storage stores a temporal change in the expected detection value, a rate of increase being the temporal change in the expected detection value associated with the space-heating circulation mode within a predetermined period is less than a predetermined rate of increase, and when the detection value from the second temperature sensor is less than a predetermined value at a time at which an instruction from the switch controller indicating the space-heating circulation mode is provided, the abnormality detector detects an abnormality in the circulation switcher in response to the detection value from the second temperature sensor having a rate of increase greater than or equal to the predetermined rate of increase within the predetermined period.

5. The space and water heating apparatus according to claim 1, wherein when an instruction from the switch controller indicates the water-heating circulation mode and a detection value from the first temperature sensor is greater than or equal to a reference value, the expected detection value associated with the water-heating circulation mode is greater than or equal to a determination value after a wait time elapsed from a time at which the instruction is provided, and when an instruction from the switch controller indicates the water-heating circulation mode and the detection value from the first temperature sensor is greater than or equal to the reference value, the abnormality detector detects an abnormality in the circulation switcher in response to the detection value from the second temperature sensor being less than the determination value after the wait time elapsed from a time at which the instruction is provided.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0018] FIG. 1 is a diagram of a space and water heating apparatus 1 according to an embodiment.

[0019] FIGS. 2A and 2B are each a cross-sectional view of a three-way valve 29 in the present embodiment.

[0020] FIG. 3 is a flowchart of a three-way valve abnormality detection process performed by a controller 40 in the present embodiment.

[0021] FIG. 4 is a flowchart of a space-heating abnormality detection process in the present embodiment performed in the three-way valve abnormality detection process.

[0022] FIG. 5 is a flowchart of a water-heating abnormality detection process in the present embodiment performed in the three-way valve abnormality detection process.

[0023] FIG. 6 is a flowchart of a space-heating abnormality detection process in a modification performed in the three-way valve abnormality detection process.

[0024] FIG. 7 is a graph showing example comparison of the rate of increase in the detection value from a heat-exchanger outlet temperature sensor 35 between a normal state and an abnormal state of the three-way valve 29.

DETAILED DESCRIPTION

[0025] FIG. 1 is a diagram of a space and water heating apparatus 1 according to an embodiment. As illustrated, the space and water heating apparatus 1 includes a combustion unit 4 housed in a housing 2. The combustion unit 4 incorporates a burner 3 that burns a gas mixture of fuel gas and combustion air. The combustion unit 4 is connected to a combustion fan 5 to feed the gas mixture to the combustion unit 4.

[0026] The combustion fan 5 has an intake connected to a joint 6 at which an air supply channel 7 for supplying combustion air joins a gas supply channel 8 for supplying fuel gas. The gas supply channel 8 includes a valve (not shown) that opens and closes the gas supply channel 8 and a zero governor 9 that lowers the pressure of fuel gas fed from upstream under pressure to the atmospheric pressure. The joint 6 incorporates a control valve that regulates the ratio of combustion air and fuel gas flowing into the combustion fan 5. When the combustion fan 5 is driven, the air in the housing 2 and the fuel gas in the gas supply channel 8 downstream from the zero governor 9 are drawn into the combustion fan 5 through the joint 6 at a predetermined ratio, and the resultant gas mixture is fed to the combustion unit 4.

[0027] In the combustion unit 4, the burner 3 incorporated in the combustion unit 4 burns the gas mixture. In the illustrated example, the burner 3 ejects the gas mixture downward to generate flames downward and emits exhaust gas downward. The combustion fan 5 is electrically connected to a controller 40 that controls the overall operation of the space and water heating apparatus 1. The controller 40 controls the combustion level of the burner 3 by changing the rotational speed of the combustion fan 5 based on the amount of heat to be used.

[0028] The combustion unit 4 includes a spark plug 11 that produces sparks in the burner 3 through high-voltage discharge, a flame rod 12 that detects the flames (ignition) of the burner 3, and a check valve 13 that blocks a 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.

[0029] A first heat exchanger 15 is located below the burner 3. A second heat exchanger 16 is located below the first heat exchanger 15. The exhaust gas produced from combustion with the burner 3 is emitted downward and passes through the first heat exchanger 15 and the second heat exchanger 16 in this order. The first heat exchanger 15 recovers sensible heat from the exhaust gas, and the second heat exchanger 16 recovers latent heat from the exhaust gas.

[0030] After passing through the first heat exchanger 15 and the second heat exchanger 16, the exhaust gas flows through an exhaust duct 17 and is discharged through an exhaust port 18 protruding from the top of the housing 2. In the illustrated example, the housing 2 has an air supply port 19 at the top. The air supply port 19 allows air to be drawn into the housing 2, in which the air is supplied to the joint 6 through the air supply channel 7.

[0031] The upstream end of the first heat exchanger 15 is connected to the downstream end of the second heat exchanger 16. The downstream end of the first heat exchanger 15 is connected to the upstream end of a panel radiator 20 as space heating equipment through an outgoing channel 21. The upstream end of the second heat exchanger 16 is connected to the downstream end of the panel radiator 20 through a return channel 22. The return channel 22 includes a circulation pump 23 that pumps the heating medium toward the second heat exchanger 16 and a return temperature sensor 24 that detects the temperature of the heating medium flowing into the second heat exchanger 16 (hereafter, a return temperature). The circulation pump 23 and the return temperature sensor 24 are electrically connected to the controller 40. The circulation pump 23 in the present embodiment is operated at a constant rotational speed to pump the heating medium.

[0032] The circulation pump 23 is operated to deliver the heating medium to the second heat exchanger 16, which preheats the heating medium using latent heat recovered from the exhaust gas from the burner 3. The preheated heating medium is then delivered to the first heat exchanger 15. The first heat exchanger 15 heats the heating medium using sensible heat recovered from the exhaust gas from the burner 3. The resultant high-temperature heating medium is supplied to the panel radiator 20 through the outgoing channel 21. The outgoing channel 21 connected to the downstream end of the first heat exchanger 15 includes an outgoing temperature sensor 25 that detects the temperature of the heating medium flowing out of the first heat exchanger 15 (hereafter, an outgoing temperature). The outgoing temperature sensor 25 is electrically connected to the controller 40. The controller 40 determines the amount of heat to be used based on the detection value from the outgoing temperature sensor 25, and controls combustion in the burner 3. The outgoing temperature sensor 25 in the present embodiment corresponds to a first temperature sensor in one or more aspects of the present invention. The burner 3, the first heat exchanger 15, and the second heat exchanger 16 in the present embodiment correspond to a heater in one or more aspects of the present invention.

[0033] The panel radiator 20 includes a serpentine pipe 20a in a metal panel. The heating medium passes through the pipe 20a while radiating heat, thus heating the surroundings. The heating medium passes through the panel radiator 20, returns to the circulation pump 23 through the return channel 22, and is delivered to the second heat exchanger 16 again to circulate. Although the space and water heating apparatus 1 according to the present embodiment uses hot water as the heating medium, the heating medium may be, for example, antifreeze (e.g., ethylene glycol) or silicone oil.

[0034] A branch channel 27 branches from the outgoing channel 21 downstream from the outgoing temperature sensor 25. The branch channel 27 is connected to the return channel 22 upstream from the circulation pump 23. The branch channel 27 includes a water-heating heat exchanger 28. The branch channel 27 and the return channel 22 include a three-way valve 29 at their connection. The three-way valve 29 is electrically connected to the controller 40. The three-way valve 29 can switch the circulation route of the heating medium flowing out of the first heat exchanger 15. More specifically, the three-way valve 29 can switch between a route through the panel radiator 20 (space heating equipment) (hereafter, an external circulation channel) and a route through the water-heating heat exchanger 28 (hereafter, an internal circulation channel). The structure of the three-way valve 29 will be described later with reference to other figures. The three-way valve 29 in the present embodiment corresponds to a circulation switcher in one or more aspects of the present invention. The controller 40 in the present embodiment functions as a switch controller in one or more aspects of the present invention. A section downstream from the connection between the return channel 22 and the branch channel 27 and upstream from the connection between the outgoing channel 21 and the branch channel 27 in the present embodiment corresponds to a shared portion in one or more aspects of the present invention.

[0035] The water-heating heat exchanger 28 is a liquid-liquid heat exchanger, to which a water inlet channel 30 and a hot-water outlet channel 31 are connected. The water inlet channel 30 allows clean water to flow to the water-heating heat exchanger 28, at which the clean water is heated by heat exchange with the heating medium, and the resultant hot water flows out into the hot-water outlet channel 31. The water inlet channel 30 includes a water flow sensor 32 that measures the flow rate of clean water flowing into the space and water heating apparatus 1, a water flow servo 33 that adjusts the flow rate of clean water, and a water inlet temperature sensor 34 that detects the temperature of clean water. The hot-water outlet channel 31 includes a heat-exchanger outlet temperature sensor 35 that detects the temperature of the hot water immediately after flowing out of the water-heating heat exchanger 28. The water flow sensor 32, the water flow servo 33, the water inlet temperature sensor 34, and the heat-exchanger outlet temperature sensor 35 are electrically connected to the controller 40. The heat-exchanger outlet temperature sensor 35 in the present embodiment corresponds to a second temperature sensor in one or more aspects of the present invention.

[0036] The space and water heating apparatus 1 according to the present embodiment includes a bypass channel 36 connecting a section of the water inlet channel 30 downstream from the water inlet temperature sensor 34 and a section of the hot-water outlet channel 31 downstream from the heat-exchanger outlet temperature sensor 35. The clean water flowing into the space and water heating apparatus 1 can partly flow through the bypass channel 36 without flowing to the water-heating heat exchanger 28, with the remaining clean water flowing to the water-heating heat exchanger 28. The water heated by the water-heating heat exchanger 28 mixes with the clean water passing through the bypass channel 36, and then flows out of the space and water heating apparatus 1. The bypass channel 36 and the hot-water outlet channel 31 include a bypass servo 37 at their connection. The bypass servo 37 is electrically connected to the controller 40. The bypass servo 37 can change the mixing ratio between the water heated by the water-heating heat exchanger 28 and the clean water passing through the bypass channel 36.

[0037] The hot-water outlet channel 31 includes a hot-water outlet temperature sensor 38 downstream from the bypass servo 37 to detect the temperature of the hot water flowing out of the space and water heating apparatus 1. The hot-water outlet temperature sensor 38 is connected to the controller 40. As described above, the clean water in the water inlet channel 30 can partly flow into the hot-water outlet channel 31 through the bypass channel 36 without flowing through the water-heating heat exchanger 28. Thus, the detection value from the hot-water outlet temperature sensor 38 is less than the detection value from the heat-exchanger outlet temperature sensor 35. The bypass servo 37 can adjust the mixing ratio to reduce temperature fluctuations of the hot water flowing out of the space and water heating apparatus 1.

[0038] The controller 40 is also connected to a water-heating remote control 41 and a space-heating remote control 42. The user can operate the water-heating remote control 41 to turn on or off the water heating operation or set the hot water temperature. Similarly, the user can operate the space-heating remote control 42 to provide an instruction to start or stop the space heating operation or set the temperature for space heating. The controller 40 includes a storage 40a that can store various items of information about the space and water heating apparatus 1 as described later.

[0039] FIGS. 2A and 2B are each a cross-sectional view of a three-way valve 29 in the present embodiment. As illustrated, the three-way valve 29 includes a valve cavity 50 that can be open in three directions. In the illustrated example, the valve cavity 50 has a left opening connecting with the branch channel 27, a right opening connecting with a section of the return channel 22 closer to the panel radiator 20 than the connection with the branch channel 27 (hereafter, an equipment return channel 22a), and an upper opening connecting with a section of the return channel 22 closer to the second heat exchanger 16 than the connection with the branch channel 27 (hereafter, a heat-exchanger return channel 22b).

[0040] The valve cavity 50 accommodates a water-heating valve element 51 that opens and closes the branch channel 27 and a space-heating valve element 52 that opens and closes the equipment return channel 22a. The water-heating valve element 51 and the space-heating valve element 52 are attached in a reversed manner to a movable shaft 53 that can reciprocate laterally. The movable shaft 53 is driven by a drive 54. The drive 54 in the present embodiment incorporates a stepper motor and converts its rotation to axial (lateral) movement of the movable shaft 53.

[0041] In FIG. 2A, the movable shaft 53 is moved to the left, with the water-heating valve element 51 closing the branch channel 27 and the space-heating valve element 52 opening the equipment return channel 22a. In this state, the heating medium forced out of the first heat exchanger 15 by the circulation pump 23 circulates through the panel radiator 20 (external circulation channel) without being distributed to the water-heating heat exchanger 28. This is a space-heating circulation mode.

[0042] When the movable shaft 53 is driven by the drive 54 to move to the right as shown in FIG. 2B, the space-heating valve element 52 closes the equipment return channel 22a, and the water-heating valve element 51 opens the branch channel 27. In this state, the heating medium forced out of the first heat exchanger 15 by the circulation pump 23 circulates through the water-heating heat exchanger 28 (internal circulation channel) without being distributed to the panel radiator 20. This is a water-heating circulation mode.

[0043] Although not shown, the movable shaft 53 can be placed between the position for the space-heating circulation mode in FIG. 2A and the position for the water-heating circulation mode in FIG. 2B. In this state, both the branch channel 27 and the equipment return channel 22a are open. This allows the heating medium to circulate simultaneously through both the panel radiator 20 (external circulation channel) and the water-heating heat exchanger 28 (internal circulation channel).

[0044] In such a space and water heating apparatus 1, an abnormality (failure) in the three-way valve 29 may decrease user comfort. For example, in the water-heating circulation mode, the space-heating valve element 52 closes the equipment return channel 22a and may be stuck or blocked by foreign matter. The three-way valve 29 may thus remain in the water-heating circulation mode without switching to the space-heating circulation mode during the space heating operation. This causes the hot water in the water-heating heat exchanger 28 to heat up. This may cause the hot water to flow out at high temperature the next time hot water is supplied. In particular, this is more likely to occur when the space and water heating apparatus 1 according to the present embodiment includes the panel radiator 20 as the space heating equipment. With the panel radiator 20, the heating medium temperature may be set higher during the space heating operation than during the water heating operation. Conversely, when the three-way valve 29 remains in the space-heating circulation mode without switching to the water-heating circulation mode during the water heating operation, the temperature of the supplied hot water may not sufficiently rise and may be different from a set temperature, thus decreasing user comfort. Thus, in the space and water heating apparatus 1 according to the present embodiment, the controller 40 performs a three-way valve abnormality detection process described below to detect an abnormality in the three-way valve 29. The controller 40 in the present embodiment functions as an abnormality detector in one or more aspects of the present invention.

[0045] FIG. 3 is a flowchart of the three-way valve abnormality detection process performed by the controller 40 in the present embodiment. As illustrated, at the start of the three-way valve abnormality detection process, the determination is first performed as to whether an instruction for switching to the space-heating circulation mode has been provided to the three-way valve 29 (STEP 1). The controller 40 provides an instruction for switching to the space-heating circulation mode in response to an operation on the space-heating remote control 42. When an instruction for switching to the space-heating circulation mode has been provided to the three-way valve 29 (Yes in STEP 1), a space-heating abnormality detection process described below is performed (STEP 2). After the space-heating abnormality detection process is performed, the process returns to STEP 1.

[0046] FIG. 4 is a flowchart of the space-heating abnormality detection process in the present embodiment performed in the three-way valve abnormality detection process. In the space-heating abnormality detection process, an initial detection value from the heat-exchanger outlet temperature sensor 35 is obtained first (STEP 10). As described above, the heat-exchanger outlet temperature sensor 35 can detect the temperature of the hot water immediately after flowing out of the water-heating heat exchanger 28. The initial detection value is the detection value from the heat-exchanger outlet temperature sensor 35 obtained at the start of the space-heating abnormality detection process in response to an instruction for switching to the space-heating circulation mode.

[0047] A threshold for the detection value from the heat-exchanger outlet temperature sensor 35 is then selected based on the obtained initial detection value (STEP 11). The threshold is set to a value greater than the initial detection value and not to be exceeded by the detection value from the heat-exchanger outlet temperature sensor 35 when the three-way valve 29 is in the space-heating circulation mode. The threshold is prestored in the storage 40a in the controller 40 in a manner associated with the space-heating circulation mode of the three-way valve 29. When the three-way valve 29 in normal operation has switched to the space-heating circulation mode (refer to FIG. 2A), the heating medium does not circulate through the water-heating heat exchanger 28 (internal circulation channel). Thus, the detection value from the heat-exchanger outlet temperature sensor 35 that is expected (hereafter, an expected detection value) is less than the threshold. However, the initial detection value from the heat-exchanger outlet temperature sensor 35 may be already high when an instruction for switching to the space-heating circulation mode is provided to the three-way valve 29. This may occur when the water heating operation has been performed (the heating medium has been circulating through the water-heating heat exchanger 28) before the instruction. Thus, the threshold differs based on the initial detection value. For example, for an initial detection value less than 30 C., the threshold is set to 40 C. For an initial detection value greater than or equal to 30 C. and less than 40 C., the threshold is set to 50 C. For an initial detection value greater than or equal to 40 C., the threshold is set to 60 C. The threshold is greater for a greater initial detection value. Although the initial detection values are divided into three levels each associated with the corresponding threshold in the present embodiment, the initial detection values may be divided into more than three levels each associated with the corresponding threshold.

[0048] After the threshold is selected based on the initial detection value, the determination is performed as to whether the detection value from the heat-exchanger outlet temperature sensor 35 is greater than or equal to the threshold (STEP 12). When the detection value from the heat-exchanger outlet temperature sensor 35 is greater than or equal to the threshold (Yes in STEP 12), such a detection value indicates that the heating medium has been circulating through the water-heating heat exchanger 28 (internal circulation channel) and has heated the hot water in the water-heating heat exchanger 28. Thus, an abnormality in the three-way valve 29 is detected (STEP 13). A notification about the abnormality in the three-way valve 29 is then provided (STEP 14). In the present embodiment, the notification about the abnormality is provided using a display (not shown) on the water-heating remote control 41 or the space-heating remote control 42. The notification about the abnormality may be provided in any other manner, such as using sound output from a speaker (not shown) incorporated in the water-heating remote control 41 or the space-heating remote control 42. In addition to providing the notification about the abnormality, the combustion in the burner 3 may be stopped, or the hot water supply may be stopped (restricted) by controlling the water flow servo 33. The space-heating abnormality detection process in FIG. 4 and the three-way valve abnormality detection process in FIG. 3 then end

[0049] When the detection value from the heat-exchanger outlet temperature sensor 35 is less than the threshold (No in STEP 12), the determination is performed as to whether the monitoring period has ended (STEP 15). In the present embodiment, the monitoring period is set to a predetermined time (e.g., three minutes) from when an instruction for switching to the space-heating circulation mode is provided to the three-way valve 29. When the monitoring period has not ended (No in STEP 15), the process returns to STEP 12 to repeat the determination as to whether the detection value from the heat-exchanger outlet temperature sensor 35 is greater than or equal to the threshold. When the monitoring period has ended without the detection value from the heat-exchanger outlet temperature sensor 35 being greater than or equal to the threshold (Yes in STEP 15), the three-way valve 29 is determined to be normal. Thus, the space-heating abnormality detection process in FIG. 4 ends, and the process returns to the three-way valve abnormality detection process in FIG. 3.

[0050] The process described above is performed when an instruction for switching to the space-heating circulation mode has been provided to the three-way valve 29 in STEP 1 (Yes in STEP 1) in the three-way valve abnormality detection process. In contrast, when no instruction for switching to the space-heating circulation mode has been provided to the three-way valve 29 (No in STEP 1), the determination is performed as to whether an instruction for switching to the water-heating circulation mode has been provided to the three-way valve 29 (STEP 3). The controller 40 provides an instruction for switching to the water-heating circulation mode in response to an operation on the water-heating remote control 41. When no instruction for switching to the water-heating circulation mode has been provided to the three-way valve 29 (No in STEP 3), the process returns to STEP 1.

[0051] When an instruction for switching to the water-heating circulation mode has been provided to the three-way valve 29 (Yes in STEP 3), a water-heating abnormality detection process described below is performed (STEP 4). After the water-heating abnormality detection process is performed, the process returns to STEP 1.

[0052] FIG. 5 is a flowchart of the water-heating abnormality detection process in the present embodiment performed in the three-way valve abnormality detection process. In the water-heating abnormality detection process, the determination is first performed as to whether a predetermined wait time (e.g., five minutes) has elapsed after an instruction for switching to the water-heating circulation mode is provided to the three-way valve 29 (STEP 20). When the wait time has not elapsed (No in STEP 20), the water-heating abnormality detection process returns to its starting point, and the determination in STEP 20 is repeated.

[0053] When the wait time has elapsed (Yes in STEP 20), the determination is performed as to whether the detection value from the outgoing temperature sensor 25 is greater than or equal to a reference value (STEP 21). As described above, the outgoing temperature sensor 25 can detect the temperature of the heating medium flowing out of the first heat exchanger 15 (outgoing temperature). The reference value is preset as a minimum detection value from the outgoing temperature sensor 25 that is expected when the operation of the circulation pump 23 and the combustion in the burner 3 are normal. The reference value may be prestored in the storage 40a in the controller 40. The reference value may be variable based on the hot water temperature set with the water-heating remote control 41. The reference value may be greater for a higher set temperature of the hot water.

[0054] When the detection value from the outgoing temperature sensor 25 is less than the reference value (No in STEP 21), the circulation pump 23 or the combustion in the burner 3 is determined to be abnormal (STEP 22). Thus, a notification about the abnormality in the circulation pump 23 or the combustion in the burner 3 is provided (STEP 23). In the present embodiment, the notification about the abnormality is provided using the display on the water-heating remote control 41 or the space-heating remote control 42. However, the notification may be provided using sound output from the speaker incorporated in the water-heating remote control 41 or the space-heating remote control 42. In addition to providing the notification about the abnormality, the combustion in the burner 3 may be stopped. The water-heating abnormality detection process in FIG. 5 and the three-way valve abnormality detection process in FIG. 3 then end. When the detection value from the outgoing temperature sensor 25 is less than the reference value, the hot water supply may be restricted by controlling the water flow servo 33, instead of providing a direct notification about an abnormality. This situation indicates less possibility of hot water flowing out at high temperature.

[0055] When the detection value from the outgoing temperature sensor 25 is greater than or equal to the reference value (Yes in STEP 21), the operation of the circulation pump 23 and the combustion in the burner 3 are determined to be normal. The determination is then performed as to whether the detection value from the heat-exchanger outlet temperature sensor 35 is less than a determination value (STEP 24). The determination value is set to the lower limit detectable by the heat-exchanger outlet temperature sensor 35 when the three-way valve 29 is in the water-heating circulation mode. The determination value is prestored in the storage 40a in the controller 40 in a manner associated with the water-heating circulation mode of the three-way valve 29. When the three-way valve 29 in normal operation has switched to the water-heating circulation mode (refer to FIG. 2B), the heating medium circulates through the water-heating heat exchanger 28 (internal circulation channel) to heat the hot water in the water-heating heat exchanger 28. Thus, the expected detection value from the heat-exchanger outlet temperature sensor 35 is greater than or equal to the determination value. The determination value may differ based on the hot water temperature set with the water-heating remote control 41. The determination value may be greater for a higher set temperature of the hot water.

[0056] When the detection value from the heat-exchanger outlet temperature sensor 35 is less than the determination value (Yes in STEP 24), such a detection value indicates that the heating medium has not been circulating through the water-heating heat exchanger 28 (internal circulation channel) and has not heated the hot water in the water-heating heat exchanger 28 after flowing out of the first heat exchanger 15 at a temperature higher than or equal to the reference value. Thus, an abnormality in the three-way valve 29 is detected (STEP 25). A notification about the abnormality in the three-way valve 29 is then provided (STEP 26). The water-heating abnormality detection process in FIG. 5 and the three-way valve abnormality detection process in FIG. 3 then end. In the present embodiment, the notification about the abnormality is provided using the display on the water-heating remote control 41 or the space-heating remote control 42. However, the notification may be provided using sound output from the speaker incorporated in the water-heating remote control 41 or the space-heating remote control 42. Instead of providing such a direct notification about an abnormality, the hot water supply may be restricted by controlling the water flow servo 33. This situation indicates less possibility of hot water flowing out at high temperature, although also indicating that the temperature of the hot water in the water-heating heat exchanger 28 does not increase to the determination value. The abnormality detected in the three-way valve 29 may be stored into the storage 40a and displayed on the water-heating remote control 41 or the space-heating remote control 42 at the maintenance of the space and water heating apparatus 1.

[0057] When the detection value from the heat-exchanger outlet temperature sensor 35 is greater than or equal to the determination value (No in STEP 24), the three-way valve 29 is determined to be normal. The water-heating abnormality detection process in FIG. 5 thus ends, and the process returns to the three-way valve abnormality detection process in FIG. 3.

[0058] As described above, the space and water heating apparatus 1 according to the present embodiment includes the heat-exchanger outlet temperature sensor 35 that detects the temperature of the hot water immediately after flowing out of the water-heating heat exchanger 28, separately from the outgoing temperature sensor 25 that detects the temperature of the heating medium flowing out of the first heat exchanger 15 (outgoing temperature). The detection value from the heat-exchanger outlet temperature sensor 35 that is expected when the three-way valve 29 operates normally (expected detection value) is prestored in the storage 40a in the controller 40 in a manner associated with the switching mode of the three-way valve 29. The controller 40 detects an abnormality in the three-way valve 29 in response to the detection value from the heat-exchanger outlet temperature sensor 35 being different from the expected detection value associated with the switching mode of the three-way valve 29 indicated by an instruction from the controller 40.

[0059] In the space and water heating apparatus 1 according to the present embodiment, when the three-way valve 29 operates normally, the detection value from the heat-exchanger outlet temperature sensor 35 is to be the same as the expected detection value associated with the switching mode (the space-heating circulation mode or the water-heating circulation mode) of the three-way valve 29 indicated by an instruction from the controller 40. Thus, an abnormality in the three-way valve 29 can be detected in response to the detection value from the heat-exchanger outlet temperature sensor 35 being different from the expected detection value. Such abnormality detection can be achieved without the three-way valve 29 including, for example, a limit switch that operates based on the switching mode. The heat-exchanger outlet temperature sensor 35 is typically included in the space and water heating apparatus 1 to detect the temperature of the hot water to be supplied. Using this heat-exchanger outlet temperature sensor 35 also to detect an abnormality in the three-way valve 29 eliminates any additional component for such detection, thus reducing the manufacturing costs.

[0060] In the space and water heating apparatus 1 according to the present embodiment, the expected detection value associated with the space-heating circulation mode is less than a predetermined threshold. When an instruction from the controller 40 to the three-way valve 29 indicates the space-heating circulation mode, the controller 40 detects an abnormality in the three-way valve 29 in response to the detection value from the heat-exchanger outlet temperature sensor 35 being greater than or equal to the threshold. In response to an instruction indicating the space-heating circulation mode, the normal three-way valve 29 allows no heating medium to circulate through the water-heating heat exchanger 28 (internal circulation channel). In this normal state, the detection value from the heat-exchanger outlet temperature sensor 35 cannot reach the threshold. In other words, an abnormality in the three-way valve 29 can be detected in response to the detection value from the heat-exchanger outlet temperature sensor 35 increasing to the threshold.

[0061] In the space and water heating apparatus 1 according to the present embodiment, in particular, the threshold differs based on the detection value (initial detection value) from the heat-exchanger outlet temperature sensor 35 at the time at which an instruction from the controller 40 indicating the space-heating circulation mode is provided to the three-way valve 29. The threshold is greater for a greater initial detection value. The initial detection value from the heat-exchanger outlet temperature sensor 35 may be already high when an instruction indicating the space-heating circulation mode is provided by the controller 40 to the three-way valve 29. This may occur when, for example, the water heating operation has been performed (the heating medium has been circulating through the water-heating heat exchanger 28) before the instruction. In this case as well, the detection value from the heat-exchanger outlet temperature sensor 35 may increase from the initial detection value when the three-way valve 29 operates abnormally. Thus, the threshold is greater for a greater initial detection value. An abnormality in the three-way valve 29 can be detected in response to the detection value from the heat-exchanger outlet temperature sensor 35 being greater than or equal to such a threshold. This achieves the abnormality detection with less erroneous detection.

[0062] In the space and water heating apparatus 1 according to the present embodiment, when an instruction from the controller 40 to the three-way valve 29 indicates the water-heating circulation mode and the detection value from the outgoing temperature sensor 25 is greater than or equal to the reference value, the expected detection value associated with the water-heating circulation mode is greater than or equal to the determination value after the predetermined wait time elapsed from the time at which the instruction is provided. When an instruction from the controller 40 to the three-way valve 29 indicates the water-heating circulation mode and the detection value from the outgoing temperature sensor 25 is greater than or equal to the reference value, the controller 40 detects an abnormality in the three-way valve 29 in response to the detection value from the heat-exchanger outlet temperature sensor 35 being less than the determination value after the wait time elapsed from the time at which the instruction is provided. The detection value from the outgoing temperature sensor 25 being greater than or equal to the reference value indicates that the heating medium heated by combustion with the burner 3 is circulating with the operating circulation pump 23. In this state, in response to an instruction indicating the water-heating circulation mode, the normal three-way valve 29 allows the heating medium to circulate through the water-heating heat exchanger 28 (internal circulation channel). This causes the detection value from the heat-exchanger outlet temperature sensor 35 to increase to the determination value. In other words, an abnormality in the three-way valve 29 can be detected in response to the detection value from the heat-exchanger outlet temperature sensor 35 not increasing to the determination value.

[0063] With repeated switching between the water heating operation and the space heating operation, the detection value from the heat-exchanger outlet temperature sensor 35 may be already high when an instruction for switching to the water-heating circulation mode is provided to the three-way valve 29. This may be caused by the heat from the preceding water heating operation remaining in the water-heating heat exchanger 28. The space and water heating apparatus 1 according to the present embodiment has the wait time. With an abnormality, the three-way valve 29 may not switch to the water-heating circulation mode, allowing no heating medium to circulate through the water-heating heat exchanger 28 (internal circulation channel). This causes the detection value from the heat-exchanger outlet temperature sensor 35 to decrease to below the determination value after the wait time. Thus, an abnormality in the three-way valve 29 can be detected in response to such a decrease in the detection value.

[0064] The space and water heating apparatus 1 according to the above embodiment may be modified as described below. The modification will be described focusing on the differences from the above embodiment. Like reference numerals in the modification denote like components in the above embodiment. Such components will not be described.

[0065] FIG. 6 is a flowchart of a space-heating abnormality detection process in the modification performed by the controller 40 in the three-way valve abnormality detection process. As illustrated, in the space-heating abnormality detection process in the modification, an initial detection value is obtained first (STEP 30). The initial detection value is the detection value from the heat-exchanger outlet temperature sensor 35 obtained at the start of the space-heating abnormality detection process in response to an instruction for switching to the space-heating circulation mode provided to the three-way valve 29.

[0066] The determination is then performed as to whether the obtained initial detection value is less than a predetermined value (STEP 31). The predetermined value is prestored in the storage 40a in the controller 40. When the initial detection value is less than the predetermined value (Yes in STEP 31), the determination is performed as to whether the rate of increase in the detection value from the heat-exchanger outlet temperature sensor 35 is greater than or equal to a predetermined rate of increase (STEP 32). The rate of increase in the detection value from the heat-exchanger outlet temperature sensor 35 is the amount of change (rise) in the detection value for each predetermined time. This rate differs greatly between a normal state and an abnormal state of the three-way valve 29.

[0067] FIG. 7 is a graph showing example comparison of the rate of increase in the detection value from the heat-exchanger outlet temperature sensor 35 between a normal state and an abnormal state of the three-way valve 29. The horizontal axis indicates time. The vertical axis indicates the detection value from the heat-exchanger outlet temperature sensor 35. When the three-way valve 29 in normal operation has switched to the space-heating circulation mode, the heating medium does not circulate through the water-heating heat exchanger 28 (internal circulation channel). However, in the space-heating circulation mode, the three-way valve 29 located at the connection between the branch channel 27 and the return channel 22 (refer to FIG. 1) may still cause the heat from the outgoing channel 21 to transfer to the water-heating heat exchanger 28 on the branch channel 27 through the heating medium, with the branch channel 27 being continuous with the outgoing channel 21. Thus, the expected detection value from the heat-exchanger outlet temperature sensor 35 increases gradually as indicated by the solid line in FIG. 7. The rate of increase in this expected detection value is less than the predetermined rate of increase indicated by the broken line. The predetermined rate of increase is prestored in the storage 40a in the controller 40 in a manner associated with the space-heating circulation mode of the three-way valve 29.

[0068] In contrast, when the three-way valve 29 operates abnormally and remains in the water-heating circulation mode, the heating medium circulates through the water-heating heat exchanger 28 (internal circulation channel). This causes the detection value from the heat-exchanger outlet temperature sensor 35 to increase steeply as indicated by the dot-dash line in FIG. 7, with its rate of increase greater than the predetermined rate of increase.

[0069] Thus, when the rate of increase in the detection value from the heat-exchanger outlet temperature sensor 35 is greater than or equal to the predetermined rate of increase in STEP 32 in FIG. 6 (Yes in STEP 32), an abnormality in the three-way valve 29 is detected (STEP 33), and a notification about the abnormality in the three-way valve 29 is provided (STEP 34). The space-heating abnormality detection process in FIG. 6 and the three-way valve abnormality detection process in FIG. 3 then end.

[0070] When the rate of increase in the detection value from the heat-exchanger outlet temperature sensor 35 is less than the predetermined rate of increase (No in STEP 32), the determination is performed as to whether the monitoring period has ended (STEP 35). The monitoring period is set to a predetermined time (e.g., one minute) from when an instruction for switching to the space-heating circulation mode is provided to the three-way valve 29. When the monitoring period has not ended (No in STEP 35), the process returns to STEP 32 to repeat the determination as to whether the rate of increase in the detection value from the heat-exchanger outlet temperature sensor 35 is greater than or equal to the predetermined rate of increase. When the monitoring period has ended without the rate of increase in the detection value from the heat-exchanger outlet temperature sensor 35 being greater than or equal to the predetermined rate of increase (Yes in STEP 35), the three-way valve 29 is determined to be normal. Thus, the space-heating abnormality detection process in FIG. 6 ends, and the process returns to the three-way valve abnormality detection process in FIG. 3. The monitoring period in the modification corresponds to a predetermined period in one or more aspects of the present invention.

[0071] The process described above is performed when the initial detection value from the heat-exchanger outlet temperature sensor 35 is less than the predetermined value in STEP 31 (Yes in STEP 31). In contrast, when the initial detection value is greater than or equal to the predetermined value (No in STEP 31), the space-heating abnormality detection process in FIG. 6 ends, and the process returns to the three-way valve abnormality detection process in FIG. 3. The initial detection value from the heat-exchanger outlet temperature sensor 35 may be already high when an instruction for switching to the space-heating circulation mode is provided to the three-way valve 29. This may occur when, for example, the water heating operation has been performed (the heating medium has been circulating through the water-heating heat exchanger 28) before the instruction. With an abnormality in the three-way valve 29 in this case, the detection value from the heat-exchanger outlet temperature sensor 35 increases less steeply (has a lower rate of increase). An abnormality in the three-way valve 29 is thus less easily detectable based on the rate of increase. Thus, when the initial detection value is greater than or equal to the predetermined value, the detection of an abnormality in the three-way valve 29 based on the rate of increase is not performed. After the space-heating abnormality detection process in the modification (FIG. 6) ends in response to the initial detection value being greater than or equal to the predetermined value, the space-heating abnormality detection process in the above embodiment (FIG. 4) may then be performed. An abnormality in the three-way valve 29 is detectable based on the rate of increase in the detection value from the heat-exchanger outlet temperature sensor 35 when the initial detection value from the heat-exchanger outlet temperature sensor 35 is sufficiently different from the set value for the heating medium temperature in the space heating operation that is based on the space heating temperature set with the space-heating remote control 42. Thus, the predetermined value may be variable based on the set value for the heating medium temperature in the space heating operation. The predetermined value may be greater for a greater set value for the heating medium temperature in the space heating operation.

[0072] As described above, in the space and water heating apparatus 1 according to the modification, the rate of increase in the expected detection value associated with the space-heating circulation mode within the monitoring period is less than the predetermined rate of increase. When the initial detection value from the heat-exchanger outlet temperature sensor 35 is less than the predetermined value at the time at which an instruction from the controller 40 indicating the space-heating circulation mode is provided to the three-way valve 29, the controller 40 detects an abnormality in the three-way valve 29 in response to the detection value from the heat-exchanger outlet temperature sensor 35 having a rate of increase greater than or equal to the predetermined rate of increase within the monitoring period.

[0073] In the space and water heating apparatus 1 according to the modification, the initial detection value from the heat-exchanger outlet temperature sensor 35 may be less than the predetermined value at the time at which an instruction from the controller 40 indicating the space-heating circulation mode is provided to the three-way valve 29. In this case, the detection value from the heat-exchanger outlet temperature sensor 35 increases more steeply when the three-way valve 29 operates abnormally (when the heating medium is circulating through the water-heating heat exchanger 28) than when the three-way valve 29 operates normally. Thus, an abnormality in the three-way valve 29 can be detected in response to the rate of increase in the detection value from the heat-exchanger outlet temperature sensor 35 being greater than or equal to the predetermined rate of increase within the monitoring period. Such abnormality detection based on the rate of increase in the detection value from the heat-exchanger outlet temperature sensor 35 allows an abnormality in the three-way valve 29 to be detected promptly before the detection value from the heat-exchanger outlet temperature sensor 35 increases to the predetermined threshold.

[0074] The space and water heating apparatus 1 according to the present embodiment and the modification has been described. However, the present invention is not limited to the above embodiment and the modification and may be implemented in various manners without departing from the spirit and scope of the invention.

[0075] For example, in the above embodiment, the three-way valve 29 is located at the connection between the branch channel 27 and the return channel 22. In some embodiments, the three-way valve 29 may be located at the connection between the branch channel 27 and the outgoing channel 21. In this case as well, the three-way valve 29 can switch between the space-heating circulation mode and the water-heating circulation mode, and the technique according to one or more aspects of the present invention may be used for such a structure. In the space-heating circulation mode, the three-way valve 29 located at the connection between the branch channel 27 and the outgoing channel 21 may cause the heat from the return channel 22 to transfer to the water-heating heat exchanger 28 on the branch channel 27 through the heating medium, with the branch channel 27 being continuous with the return channel 22.

[0076] In the above embodiment, the apparatus includes the first heat exchanger 15 and the second heat exchanger 16. The circulating heating medium is preheated by the second heat exchanger 16 and then heated by the first heat exchanger 15. In some embodiments, the apparatus may eliminate the second heat exchanger 16 and use the first heat exchanger 15 alone to heat the heating medium.

[0077] In the above embodiment, the bypass channel 36 connects the water inlet channel 30 and the hot-water outlet channel 31, and the bypass servo 37 can change the mixing ratio between the water heated by the water-heating heat exchanger 28 and the clean water passing through the bypass channel 36. In some embodiments, the apparatus may eliminate the bypass channel 36 and the bypass servo 37, and may have a structure that allows the user to adjust the mixing ratio between the hot water and the water as appropriate using a mixing faucet. In this case, the heat-exchanger outlet temperature sensor 35 and the hot-water outlet temperature sensor 38 may be combined as a single temperature sensor, rather than being separate temperature sensors.

[0078] In the above embodiment, the water-heating remote control 41 and the space-heating remote control 42 are separate remote controls. In some embodiments, the water-heating remote control 41 and the space-heating remote control 42 may be combined as a single remote control that receives operations for both the water heating operation and the space heating operation.

[0079] In the above embodiment, the panel radiator 20 is described as an example of the space heating equipment. However, the space heating equipment including a radiator is not limited to the panel radiator 20, and may be, for example, a bathroom heating and drying unit, a fan convector, or a floor heating unit.

[0080] In the above embodiment, the burner 3 burns the gas mixture as the heater that heats the heating medium. In some embodiments, the heater may have another structure, such as an electric heating unit, a heat pump, or a fuel cell.

REFERENCE SIGNS LIST

[0081] 1 space and water heating apparatus [0082] 2 housing [0083] 3 burner [0084] 4 combustion unit [0085] 5 combustion fan [0086] 6 joint [0087] 7 air supply channel [0088] 8 gas supply channel [0089] 9 zero governor [0090] 11 spark plug [0091] 12 flame rod [0092] 13 check valve [0093] 15 first heat exchanger [0094] 16 second heat exchanger [0095] 17 exhaust duct [0096] 18 exhaust port [0097] 19 air supply port [0098] 20 panel radiator [0099] 20a pipe [0100] 21 outgoing channel [0101] 22 return channel [0102] 22a equipment return channel [0103] 22b heat-exchanger return channel [0104] 23 circulation pump [0105] 24 return temperature sensor [0106] 25 outgoing temperature sensor [0107] 27 branch channel [0108] 28 water-heating heat exchanger [0109] 29 three-way valve [0110] 30 water inlet channel [0111] 31 hot-water outlet channel [0112] 32 water flow sensor [0113] 33 water flow servo [0114] 34 water inlet temperature sensor [0115] 35 heat-exchanger outlet temperature sensor [0116] 36 bypass channel [0117] 37 bypass servo [0118] 38 hot-water outlet temperature sensor [0119] 40 controller [0120] 40a storage [0121] 41 water-heating remote control [0122] 42 space-heating remote control [0123] 50 valve cavity [0124] 51 water-heating valve element [0125] 52 space-heating valve element [0126] 53 movable shaft [0127] 54 drive