water heater

Abstract

This system detects heater malfunctions within the water heater in a way that minimizes the complexity of the device configuration. [Solution] The water heater 1 comprises a water pipe 9, a heater 35 that heats the water pipe 9, a drive control unit that controls the operation of the heater 35, a temperature detection unit that detects the temperature, and an abnormality determination unit. The abnormality determination unit performs an abnormality determination process to determine whether the heater 35 is abnormal or not, based on the degree of temperature rise detected by the temperature detection unit after the drive control unit starts operating the heater 35, or the degree of temperature decrease detected by the temperature detection unit after the drive control unit stops operating the heater 35.

Description

Technical Field

[0001] This disclosure relates to a water heater.

Background Art

[0002] Patent Document 1 discloses an example of a water heater. The water heater of Patent Document 1 is equipped with a structure for preventing a short circuit in the wiring of a freeze prevention heater provided in a pipe connector. In this water heater, a cylindrical pipe connector for connecting an internal pipe disposed inside the housing to an external pipe outside the housing is provided on the bottom plate of the housing. Below the bottom plate in the pipe connector, a heater housing portion having a housing hole for inserting and housing the freeze prevention heater from above is provided. The freeze prevention heater is inserted and housed into the housing hole from the inside of the housing through a through hole provided in the bottom plate, and in the inserted and housed state, the upper end portion is supported at a position above the upper surface of the bottom plate through the through hole.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] In a water heater, a heater is provided for the purpose of preventing freezing and the like, but this type of heater has a concern that malfunction may occur due to disconnection or the like. If a malfunction occurs in the heater and the fact is left undetected, there is a concern that unexpected problems may occur. On the other hand, if a complicated circuit or the like is provided to detect a malfunction of the heater, it will lead to a complication of the internal configuration.

[0005] One of the objects of this disclosure is to provide a technique capable of detecting an abnormality of a heater occurring in a water heater while suppressing complication of the device configuration.

Means for Solving the Problems

[0006] One of the disclosed items is a water heater, A gas burner that burns gas and supplies exhaust gas produced by the combustion of the gas, A heat exchanger comprising heat transfer tubes heated by the exhaust supplied from the gas burner, A water pipe having a water inlet for introducing water and a water inlet pipe provided between the heat transfer tube for supplying water to the heat transfer tube, and a hot water outlet pipe connected to the downstream side of the heat transfer tube for carrying hot water supplied from the heat transfer tube, forming a path for carrying hot and cold water, A heater for heating the water pipe, A drive control unit that controls the drive of the heater, A temperature detection unit that detects temperature, An abnormality determination unit performs an abnormality determination process to determine whether the heater is abnormal or not, based on the degree of temperature rise detected by the temperature detection unit after the drive control unit starts driving the heater, or the degree of temperature decrease detected by the temperature detection unit after the drive control unit stops driving the heater. It is equipped with. [Effects of the Invention]

[0007] The technology disclosed herein can detect heater abnormalities occurring within a water heater without complicating the device configuration. [Brief explanation of the drawing]

[0008] [Figure 1] Figure 1 is a schematic diagram illustrating a water heater according to the first embodiment. [Figure 2] Figure 2 is a block diagram illustrating a simplified electrical configuration of a part of the water heater shown in Figure 1. [Figure 3] Figure 3 is a circuit diagram illustrating the circuit configuration of the heater and other components in the water heater shown in Figure 1. [Figure 4] Figure 4 is a flowchart illustrating the flow of the abnormality detection process performed on the water heater shown in Figure 1. [Modes for carrying out the invention]

[0009] Each of the following [1] to [6] is an example of the technology included in this disclosure.

[0010] [1] A gas burner that burns gas and supplies exhaust gas produced by the combustion of the gas, A heat exchanger comprising heat transfer tubes heated by the exhaust supplied from the gas burner, A water pipe having a water inlet for introducing water and a water inlet pipe provided between the heat transfer tube for supplying water to the heat transfer tube, and a hot water outlet pipe connected to the downstream side of the heat transfer tube for carrying hot water supplied from the heat transfer tube, forming a path for carrying hot and cold water, A heater for heating the water pipe, A drive control unit that controls the drive of the heater, A temperature detection unit that detects temperature, An abnormality determination unit performs an abnormality determination process to determine whether the heater is abnormal or not, based on the degree of temperature rise detected by the temperature detection unit after the drive control unit starts driving the heater, or the degree of temperature decrease detected by the temperature detection unit after the drive control unit stops driving the heater. A water heater equipped with the following features.

[0011] In the water heater described in [1] above, the abnormality determination unit performs abnormality determination processing and can determine whether or not the heater is abnormal, thus enabling the detection of heater abnormalities occurring within the water heater. Furthermore, the abnormality determination unit determines whether or not the heater is abnormal based on the degree of temperature rise detected by the temperature detection unit after the drive control unit starts driving the heater, or the degree of temperature decrease detected by the temperature detection unit after the drive control unit stops driving the heater, thus enabling the detection of heater abnormalities in a manner that minimizes the complexity of the device configuration.

[0012] 〔2〕If the temperature detected by the temperature detection unit does not rise by a certain value or more within a predetermined time after the drive control unit starts driving the heater, or if the temperature detected by the temperature detection unit does not drop by a certain value or more within a predetermined time after the drive control unit stops driving the heater, the abnormality determination unit determines that there is an abnormality. The water heater according to 〔1〕.

[0013] In the water heater of 〔2〕 above, when the temperature detected by the temperature detection unit does not rise by a certain value or more within a predetermined time after the drive control unit starts driving the heater, or when the temperature detected by the temperature detection unit does not drop by a certain value or more within a predetermined time after the drive control unit stops driving the heater, an abnormality is determined. Therefore, the abnormality determination can be performed while suppressing complex arithmetic expressions and complex detection operations as much as possible.

[0014] 〔3〕Comprising a plurality of thermistors, The abnormality determination unit includes the proximity thermistor closest to the heater among the plurality of thermistors, The abnormality determination unit determines the abnormality of the heater based on the degree of temperature rise detected by the proximity thermistor after the drive control unit starts driving the heater or the degree of temperature drop detected by the proximity thermistor after the drive control unit stops driving the heater. The water heater according to 〔1〕 or 〔2〕.

[0015] In the water heater of 〔3〕 above, the proximity thermistor closest to the heater is more likely to quickly reflect the temperature change corresponding to the temperature rise of the heater when the heater starts driving normally. And this proximity thermistor is more likely to quickly reflect the temperature change corresponding to the temperature drop of the heater accompanying the stop of driving when the heater stops driving normally after driving normally. And the water heater of 〔3〕 above determines the abnormality of the heater based on the degree of temperature rise detected by the proximity thermistor after the heater starts driving or the degree of temperature drop detected by the proximity thermistor after the heater stops driving, so it is easier to detect the abnormality of the heater more quickly.

[0016] [4] The heater is provided at least at a predetermined position of the water pipe, The temperature detection unit is a thermistor that detects the temperature of the water in the water pipe The water heater according to any one of [1] to [3].

[0017] In the water heater of [4] above, it is possible to determine whether the heater is abnormal based on the degree of temperature rise at a predetermined position of the water pipe after starting the drive of the heater that heats the water pipe or the degree of temperature drop at a predetermined position of the water pipe after stopping the drive of the heater. When the heater that heats the water pipe is normal, it is likely to be reflected in the temperature of the water in the water pipe after starting the drive or after stopping the drive. Therefore, if the abnormality of the heater is determined by the above method, it is easier to detect the abnormality of the heater more quickly and accurately.

[0018] [5] The heater is provided at least at a predetermined position of the water pipe, The temperature detection unit is a thermistor that is arranged separately from the water in the water pipe so as to detect the ambient temperature in the water heater The water heater according to any one of [1] to [3].

[0019] In the water heater of [5] above, it is possible to determine whether the heater is abnormal based on the degree of temperature rise of the ambient temperature after starting the drive of the heater that heats the water pipe or the degree of temperature drop of the ambient temperature after stopping the drive of the heater. When the heater that heats the water pipe is normal, it is likely to be reflected in the ambient temperature after starting the drive or after stopping the drive. Therefore, if the abnormality of the heater is determined by the above method, it is easier to detect the abnormality of the heater more quickly and accurately.

[0020] [6] The abnormality determination unit newly performs the abnormality determination process when the operation time or the number of operations from the previous abnormality or normal determination in the abnormality determination process exceeds a reference value The water heater according to any one of [1] to [5].

[0021] The water heater described in [6] above can perform an abnormality determination process each time the operating time or number of operations since the last abnormality or normality determination exceeds a standard value, thus preventing the operating time from exceeding the limit or the number of operations from exceeding the limit without a determination being made.

[0022] <First Embodiment> The following description relates to the first embodiment. 1.Basic configuration The water heater 1 shown in Figure 1 is configured as a bath and hot water supply system equipped with a function to supply hot water to a bathtub 60 and a function to heat the water in the bathtub. The water heater 1 comprises a hot water supply circuit 2 and a bath side circuit 3. The hot water supply circuit 2 includes an inlet pipe 12, an outlet pipe 10, a gas burner 4, a hot water supply heat exchanger 6, etc., and functions as a device that heats tap water supplied from the outside and dispenses it as hot water. The bath side circuit 3 includes a gas burner 54, a bath side heat exchanger 56, circulation piping 66, a circulation pump 62, thermistors 64, 65, etc., and is used for circulation heating during automatic bath filling, reheating the bath, etc. In the following representative example, the part of the water heater 1 excluding the controller 22 and remote controller 80 is the hot water supply device 1A. The hot water supply device 1A is configured with a hot water supply circuit 2 and a bath side circuit 3.

[0023] In the configuration shown in Figure 1, the water supply pipe 9 is configured by connecting the water inlet pipe 12, heat transfer pipe 8a, piping 20, heat transfer pipe 7a, and hot water outlet pipe 10. The water supply pipe 9 forms a path for hot and cold water to flow and functions as a channel for water (water to be heated) introduced from a water supply pipe (not shown) located outside the water heater 1. The water inlet pipe 12 is installed between the water inlet 16 and the heat transfer pipes 7a and 8a, and is configured as a pipeline into which water flows from the water inlet 16. The water inlet pipe 12 is a pipe for supplying water to the heat transfer pipes 7a and 8a, and functions as a path for sending the water introduced via the water inlet 16 to the hot water heat exchanger 6. The hot water outlet pipe 10 is connected to the downstream side of the heat transfer pipes 7a and 8a and is a pipe for carrying the hot water supplied from the heat transfer pipe 7a. The hot water outlet pipe 10 is configured as a pipeline for sending hot water to the hot water outlet 18.

[0024] The gas burner 4 burns the gas (combustion gas) supplied via the gas pipe 40 to generate exhaust (combustion exhaust), and operates to supply this exhaust to the downstream side of the exhaust path. The hot water side heat exchanger 6 transfers the heat generated by the gas burner 4 to the water passing through the water pipe 9. The hot water side heat exchanger 6 has heat transfer tubes 7a and 8a that are heated by the exhaust generated by the combustion of gas in the gas burner 4 (exhaust supplied from the gas burner 4) to the water passing through the water pipe 9 (a pipeline consisting of the inlet pipe 12, heat transfer tube 8a, pipe 20, heat transfer tube 7a, and outlet pipe 10), and is the part that transfers the heat of the exhaust to the water in the heat transfer tubes 7a and 8a to heat the water. The hot water side heat exchanger 6 is installed in the middle of the water pipe 9 and functions to transfer the heat generated by the combustion in the gas burner 4 to the water passing through the heat transfer tubes 8a and 7a. The hot water supply side heat exchanger 6 comprises a primary heat exchanger 7 and a secondary heat exchanger 8. The primary heat exchanger 7 is located upstream of the combustion exhaust path of the gas burner 4 within the hot water supply combustion chamber 90, and the secondary heat exchanger 8 is located downstream of the combustion exhaust path within the hot water supply combustion chamber 90.

[0025] In the hot water supply circuit 2, an inlet pipe 12 is connected to the inlet of the secondary heat exchanger 8, supplying tap water. The inlet pipe 12 is equipped with a thermistor 25 and a water flow sensor 34. The thermistor 25 functions as a water temperature detection unit that detects the temperature of the water passing through the inlet pipe 12 (i.e., the water temperature at a location upstream of the heat exchanger in the water supply pipe 9). The water flow sensor 34 functions as a water flow detection unit that detects the amount of water passing through the inlet pipe 12 (specifically, the amount of water introduced at the water inlet 16). Downstream of the inlet pipe 12, the heat transfer tubes 8a of the secondary heat exchanger 8 are connected. Downstream of the heat transfer tubes 8a, a pipe 20 is connected that connects the heat transfer tubes 8a to the heat transfer tubes 7a of the primary heat exchanger 7. Downstream of the pipe 20, the heat transfer tubes 7a of the primary heat exchanger 7 are connected in a configuration that is connected to the pipe 20. Downstream of the heat transfer tube 7a, a hot water outlet pipe 10 is connected to the outlet of the primary heat exchanger 7. The hot water outlet pipe 10 is a pipeline that guides the hot water heated in the primary heat exchanger 7. The hot water outlet pipe 10 is equipped with thermistors 26 and 27. Thermistors 26 and 27 detect the temperature of the water in the hot water outlet pipe 10. Thermistor 27 is an inner cylinder outlet water temperature detection thermistor that detects the temperature of the hot water flowing out of the primary heat exchanger 7, and is located in the hot water outlet pipe 43 closer to the primary heat exchanger 7, and more specifically, in the hot water outlet pipe 10 upstream of the connection between the hot water outlet pipe 10 and the bypass passage 14. Thermistor 26 is a thermistor that detects the temperature of the water near the outlet 18 in the hot water outlet pipe 10, and is located downstream of thermistor 27 in the hot water outlet pipe 43, and more specifically, is located downstream of the connection between the hot water outlet pipe 10 and the bypass passage 14.

[0026] The hot water supply side heat exchanger 6 functions to recover sensible heat from the combustion exhaust using the primary heat exchanger 7, and then recover latent heat using the secondary heat exchanger 8. The primary heat exchanger 7 is equipped with heat transfer tubes 7a that serve as the water passage path within the primary heat exchanger 7. The primary heat exchanger 7 transfers the combustion heat contained in the combustion exhaust generated by the gas burner 4 to the water passing through the heat transfer tubes 7a, and exchanges heat by transferring sensible heat energy to the water. The secondary heat exchanger 8 is equipped with heat transfer tubes 8a that serve as the water passage path within the secondary heat exchanger 8. The secondary heat exchanger 8 transfers the combustion heat generated by the gas burner 4 after it has passed through the primary heat exchanger 7 to the water passing through the heat transfer tubes 8a, and exchanges heat by transferring latent heat energy to the water.

[0027] A bypass path 14 is provided as a water flow path that bypasses the inlet pipe 12 and the outlet pipe 10, and is configured as a water flow path different from that of the hot water heat exchanger 6. The bypass path 14 is equipped with a bypass valve 32 that can change from a closed state that blocks the flow of water through the bypass path 14 to an open state (a state in which the opening degree is increased compared to the closed state) (for example, a configuration that allows for stepless change). In the inlet pipe 12, a water flow rate control valve 33 is provided upstream of the branching point where the bypass path 14 is connected. The water flow rate control valve 33 is configured to continuously change the opening degree of the inlet pipe 12 between a closed state and a fully open state, and functions to adjust the amount of water flowing through the water pipe 9.

[0028] The gas pipe 40 that supplies gas to the gas burner 4 is equipped with a gas source solenoid valve 42, a hot water gas proportional control valve 44, and hot water switching solenoid valves 46, 46... for each branch route to each gas burner 4, starting from the upstream side. Below the hot water combustion chamber 90, a fan 48 is provided to supply combustion air to each gas burner 4 and gas burner 54. The gas pipe 40 branches into a pipeline that supplies gas to the gas burner 4 side (first branch pipe) and a pipeline that supplies gas to the gas burner 54 side (second branch pipe). The second branch pipe is connected to the gas burner 54, and a switching solenoid valve 53 is provided in this second branch pipe. The hot water gas proportional control valve 44 and the hot water switching solenoid valve 46 function to adjust the amount of gas supplied to the gas burner 4.

[0029] In the bath-side circuit 3, the circulation piping 66 comprises piping 67, piping 68, and piping 69. Piping 67 is for guiding water from the bathtub 60 to the bath-side heat exchanger 56. Piping 68 is for guiding water from the bath-side heat exchanger 56 to the bathtub 60. Piping 69 is a pipe inside the bath-side heat exchanger 56 that is connected to piping 67 and piping 68. One end of the circulation piping 66 is connected to the inside of the bathtub 60. The circulation piping 66 is a path that circulates the hot water drawn out of the bathtub 60 and returns it to the bathtub 60. For example, during reheating or heating operations, the circulation piping 66 is a path that guides the hot water drawn from the bathtub 60 to the bath-side heat exchanger 56 via piping 67, and then circulates the hot water that has passed through the bath-side heat exchanger 56 back to the bathtub 60 via piping 68. A water flow sensor 63 is provided in the circulation piping 66.

[0030] The gas burner 54 burns combustion gas supplied via the gas pipe 40, generating combustion exhaust. The bath-side heat exchanger 56 transfers the heat generated by the gas burner 54 (second burner) to the hot water passing through the circulation pipe 66. The bath-side heat exchanger 56 comprises a primary bath heat exchanger 57 and a secondary bath heat exchanger 58. The primary bath heat exchanger 57 is located upstream of the combustion exhaust path of the gas burner 54 within the hot water combustion chamber 90, and the secondary bath heat exchanger 58 is located downstream of the combustion exhaust path within the hot water combustion chamber 90. The piping 67 is located between the bathtub 60 and the secondary bath heat exchanger 58.

[0031] The piping 67 is equipped with a circulation pump 62 and a thermistor 64. The thermistor 64 detects the temperature of the water passing through the piping 67. That is, the thermistor 64 detects the temperature of the hot water discharged from the bathtub 60 (i.e., the temperature of the hot water in the bathtub 60). The circulation pump 62 is a pump that transfers the hot water in the circulation piping 66. The circulation pump 62 functions to cause the hot water to flow through the piping 67 from the bathtub 60 towards the secondary bath heat exchanger 58, and to draw the hot water from the bathtub 60 and discharge it toward the bath-side heat exchanger 56. The piping 68 is located between the primary bath heat exchanger 57 and the bathtub 60.

[0032] A drop-off pipe 70, branched from the hot water outlet pipe 10, is connected to piping 67. The circulation piping 66 is a pipeline through which hot water can be supplied from the drop-off pipe 70. The drop-off pipe 70 is equipped with a solenoid valve 72 and a water volume sensor 74. When the hot water supply solenoid valve 72 installed in the drop-off pipe 70 is switched to the open state, hot water heated in the hot water supply circuit 2 can be supplied to the bathtub 60 via the circulation piping 66. When the hot water supply solenoid valve 72 is switched to the closed state, hot water heated in the hot water supply circuit 2 is not supplied to the bathtub 60. The drop-off pipe 70 is a pipeline that guides hot water heated by the hot water supply heat exchanger 6 (first heat exchanger) through the water passage pipe 9 to the bathtub 60. The drop-off pipe 70 is a path through which hot water passes from the hot water outlet pipe 10 of the hot water supply circuit 2 to the circulation piping 66 of the bath-side circuit 3. The drop-in pipe 70 branches off from the hot water outlet pipe 10 and is connected to the piping 67. The drop-in pipe 70 functions to guide the hot water, which has been heated by the hot water supply side heat exchanger 6 after passing through the water supply pipe 9 and flowing to the hot water outlet pipe 10, to the bathtub 60 via the circulation piping 66. In a typical example, the drop-in pipe 70, solenoid valve 72, and water volume sensor 74 are also considered part of the bath-side circuit.

[0033] The water heater 1 is equipped with a controller 22 as shown in Figures 1 and 2. The controller 22 is housed in a casing that accommodates the hot water combustion chamber 90 and various components. As shown in Figure 2, the controller 22 comprises a control unit 22A configured as a known microcomputer, a memory 22B configured as a known storage means (e.g., semiconductor memory or other storage medium), and a communication unit 22C configured as an interface for communication with the outside. It is desirable that the memory 22B be provided with, for example, a non-volatile storage means. The controller 22 is configured to acquire signals from various sensors provided in the hot water supply circuit 2 and the bath side circuit 3. The controller 22 can control various actuators provided in the hot water supply circuit 2 and the bath side circuit 3. The controller 22 can control the hot water supply circuit 2 (hot water supply device), the bath side circuit 3 (bathtub side device), and perform other detection and determination operations.

[0034] As shown in Figure 2, the multiple remote controllers 80 are remote control devices capable of communicating with the controller 22, and are provided, for example, outside the housing described above. In the example of Figures 1 and 2, the multiple remote controllers 80 include a first remote controller 81 provided in the bathroom and a second remote controller 82 provided in a location other than the bathroom (for example, the kitchen). As shown in Figure 2, the first remote controller 81 includes a control unit 81A configured as a known microcomputer, a display unit 81B configured as a liquid crystal display device, and an operating means 81C provided with a plurality of known switches such as push buttons. Furthermore, the first remote controller 81 includes a communication unit 81D that communicates with the controller 22 and the second remote controller 82, and an audio output unit 81E consisting of a speaker that outputs sound. The operating means 81C is composed of a plurality of operating means and is used for input operations to instruct automatic filling of the bathtub 60, input operations to reserve automatic filling, input operations to set values, etc.

[0035] The second remote controller 82 includes a control unit 82A configured as a known microcomputer or the like, a display unit 82B configured as a liquid crystal display or the like, and an operating means 82C provided with a plurality of known switches such as push buttons. Furthermore, the second remote controller 82 also includes a communication unit 82D for transmitting signals generated by the second remote controller 82 to the controller 22, and an audio output unit 82E consisting of a speaker or the like for outputting sound. The second remote controller 82 has the same configuration as the first remote controller 81, or a simplified configuration. The same operations and settings as the first remote controller 81 are possible. The operating means 81C and operating means 82C may include input interfaces such as touch panels or levers.

[0036] 2. Anti-freeze heater As shown in Figure 1, the water heater 1 is equipped with a heater 35. In the example in Figure 1, the heater 35 is provided in multiple locations, and each heater 35 can operate to heat its respective location. The heater 35 functions as a freeze prevention heater. In the example in Figure 1, the heater 35 operates to heat the water supply pipe 9. Specifically, the heater 35A is provided in a manner that allows it to heat the hot water outlet pipe 10, which is part of the water supply pipe 9, by being fixed to the hot water outlet pipe 10 and having a portion of the heater 35A positioned inside the water supply pipe 9. Furthermore, a heater 35B is also provided in the pipe 68 so that it can heat the pipe 68. Note that the arrangement of heaters 35A and 35B is merely an example, and the heater 35 may also be provided in the water inlet pipe 12, in the pipe 20, in the pipe 67, or in the bypass pipe 14.

[0037] The heater 35 has a configuration in which multiple resistive elements are electrically connected. In the example in Figure 3, the resistive elements 35Y constituting heater 35A are connected in series, and the resistive elements 35Z constituting heater 35B are connected in series. In the example in Figure 3, the heater 35 is connected between the power line 39 to which the power supply voltage from the power supply circuit 38 is applied and the ground. The power supply circuit 38 receives power supplied from an external power source (for example, an external commercial AC power source) to the water heater 1 and operates to apply a predetermined level of DC power supply voltage to the power line 39. When the switch 37 is switched to the ON state (energized state) while the power supply circuit 38 is applying a DC voltage to the power line 39, current flows through heaters 35A and 35B, causing both heaters 35A and 35B to generate heat. When switch 37 is switched to the off state (power cut off state), the power to heaters 35A and 35B is stopped, and no current flows to either heater 35A or heater 35B. Various known switches can be used for switch 37. Switch 37 may be a mechanical relay or a semiconductor relay. Furthermore, the power supply circuit 38 only needs to be configured to apply a desired voltage to the power line 39, provided that power is supplied to the water heater 1 from an external power source, and various known power supply circuits can be used.

[0038] 3. Anomaly detection operation The following explanation concerns the abnormality detection operation of water heater 1. In this embodiment, the controller 22 and switch 37 correspond to an example of a drive control unit, which controls the drive of the heater 35. Furthermore, the thermistor 27 corresponds to an example of a temperature detection unit or a short-range thermistor. The controller 22 corresponds to an example of an abnormality determination unit, and operates to perform an abnormality determination process to determine whether the heater 35 is abnormal or not, based on the degree of temperature rise detected by the temperature detection unit after the drive control unit starts driving the heater 35, or the degree of temperature decrease detected by the temperature detection unit after the drive control unit stops driving the heater 35.

[0039] The control unit 22A of the controller 22 starts the abnormality detection process shown in Figure 4 when power is supplied to the water heater 1 from the external power source mentioned above and predetermined control start conditions are met. The control start conditions may be a switch from a state where power is not supplied to the water heater 1 to a state where power is supplied, or a predetermined time may have elapsed since the control in Figure 4 was completed, or other conditions may be used.

[0040] When the control unit 22A starts the control shown in Figure 4, it determines in step S1 whether the inspection start condition has been met. The inspection start condition may be "the state in which power is not supplied to the water heater 1 has switched from a state in which power is supplied while the heater 35 is stopped operating," or "the operation of the heater 35 has stopped, and the operating time or number of operations since the previous abnormality determination process in Figure 4 (step S7 or S8) has exceeded the standard value," and it may be the case that either of these conditions has been met.

[0041] In the representative examples described below, the inspection start condition is met if any of the following is met: "While the heater 35 is stopped (for example, while switch 37 is off), the state in which power is supplied to the water heater 1 switches from a state in which no power is supplied to a state in which power is supplied"; "The operating time since the end of the judgment in the previous abnormality judgment process in Figure 4 (step S7 or S8) exceeds a predetermined standard operating time (for example, a predetermined first fixed value), and the heater 35 is stopped"; or "The number of operations since the judgment in the previous abnormality judgment process in Figure 4 (step S7 or S8) exceeds a predetermined standard number of operations (for example, a predetermined second fixed value), and the heater 35 is stopped." Note that "operating time" refers to, for example, the time during which either gas burner (either gas burner 4 or gas burner 54) is burning (the time during which combustion continues). "Number of operations" refers to the number of times the system switches from a state where all gas burners are stopped to a state where one of the gas burners (either gas burner 4 or gas burner 54) is burning.

[0042] If the control unit 22A determines in step S1 that the inspection start condition has been met, it proceeds to step S2 and checks the temperature detected by the thermistor 27 (the detected temperature T1 of the thermistor 27 at the time of step S2). If the control unit 22A determines in step S1 that the inspection start condition has not been met, it terminates the abnormality determination process shown in Figure 4.

[0043] After step S2, the control unit 22A starts driving the heater 35 in step S3. Note that if step S1 is determined to be Yes, the heater 35 is stopped before the start of step S3. In other words, when step S2 is determined to be Yes, immediately before the start of step S3, the switch 37 in Figure 3 is in the off state (power off). When performing step S3, the control unit 22A switches the switch 37 from the off state to the on state while a power supply voltage (a predetermined DC voltage) is applied to the power path 39 in the circuit of Figure 3. As a result of this operation, if the circuit is functioning correctly, the resistor elements 35Y and 35Z constituting the heater 35 switch from a state where no current flows to a state where current flows.

[0044] The control unit 22A determines whether a predetermined time has elapsed since the heater 35 was energized in step S3. The predetermined time is not particularly limited, but may be, for example, the time required for the temperature of the heater 35A to stabilize, or it may be any other time.

[0045] If the control unit 22A determines in step S4 that "the predetermined time has not elapsed since the heater 35 was energized in step S3", it proceeds to No in step S4 and repeats the determination in step S4. If the control unit 22A determines in step S4 that "the predetermined time has elapsed since the heater 35 was energized in step S3", it proceeds to step S5 and confirms the temperature detected by the thermistor 27 (the detected temperature T2 of the thermistor 27 at the time of step S5).

[0046] After step S5, the control unit 22A determines whether the temperature difference (T2-T1) between the temperature T1 confirmed in step S2 and the temperature T2 confirmed in step S2 is greater than or equal to a certain value. If the control unit 22A determines in step S6 that the temperature difference (T2-T1) is greater than or equal to a certain value, it proceeds to step S7 and determines that the heater 35 is normal. If the control unit 22A determines in step S6 that the temperature difference (T2-T1) is not greater than or equal to a certain value, it proceeds to step S8 and determines that the heater 35 is abnormal.

[0047] If the control unit 22A determines in step S7 that the heater 35 is functioning normally, it may notify the user of this fact by voice or image, and may record the time of this normal determination and the information indicating that the heater is functioning normally in memory. Similarly, if the control unit 22A determines in step S8 that the heater is functioning abnormally, it may notify the user of this fact by voice or image, and may record the time of this abnormal determination and the information indicating that the heater is functioning abnormally in memory. An example of abnormal notification by image is the display of an error code. If the control unit 22A determines in step S8 that the heater is functioning abnormally, it may prohibit subsequent predetermined operations of the water heater 1 (for example, the combustion operation of the gas burner) until predetermined recovery conditions are met.

[0048] 4. Examples of effects In the water heater 1, the abnormality determination unit performs abnormality determination processing and can determine whether or not the heater 35 is abnormal, thus enabling the detection of abnormalities in the heater 35 occurring within the water heater 1. Furthermore, since the abnormality determination unit determines whether or not the heater 35 is abnormal based on the degree of temperature rise detected by the temperature detection unit after the drive control unit starts driving the heater 35, it is possible to detect abnormalities in the heater 35 in a way that does not complicate the device configuration.

[0049] The water heater 1 determines that there is an abnormality if the temperature detected by the temperature detection unit does not rise above a certain value within a predetermined time after the drive control unit starts driving the heater 35. Therefore, it is possible to determine an abnormality while minimizing complex calculation formulas and complex detection operations.

[0050] In water heater 1, thermistor 27, which is the short-range thermistor closest to heater 35A, is more likely to quickly reflect temperature changes corresponding to the temperature rise of heater 35 when heater 35A starts operating normally. Furthermore, when heater 35A stops operating normally after starting to operate normally, thermistor 27 is more likely to quickly reflect temperature changes corresponding to the temperature drop of heater 35A that occurs when the heater stops operating. Based on this configuration, water heater 1 can more quickly detect abnormalities in heater 35A by determining the degree of temperature rise detected by thermistor 27 (short-range thermistor) after heater 35A starts operating or the degree of temperature drop detected by thermistor 27 (short-range thermistor) after heater 35A stops operating.

[0051] In the water heater 1, it is possible to determine whether the heater 35 is malfunctioning based on the degree of temperature rise at a predetermined position in the water pipe 9 (specifically, the position where the thermistor 27 is installed) after the heater 35 that heats the water pipe 9 is started to operate, or the degree of temperature drop at the predetermined position in the water pipe 9 after the heater 35 is stopped to operate. When the heater 35 that heats the water pipe 9 is functioning normally, this is easily reflected in the temperature of the water in the water pipe 9 after it is started to operate or stopped to operate. Therefore, using the above method to determine if the heater 35 is malfunctioning makes it easier to detect the malfunction of the heater 35 more quickly and accurately.

[0052] In water heater 1, an abnormality detection process is performed again if the operating time or number of operations since the last abnormality detection process exceeds a standard value. In this way, water heater 1 can perform an abnormality detection process each time the operating time or number of operations since the last abnormality detection process exceeds a standard value, thus preventing situations where too much operating time or too many operations occur without a detection being performed.

[0053] <Other Embodiments> The present invention is not limited to the embodiments described above and in the drawings. For example, any combination of the features of the embodiments described above or below is possible as long as it does not contradict each other. Furthermore, any feature of the embodiments described above or below may be omitted unless explicitly stated as essential. In addition, the embodiments described above may be modified as follows.

[0054] Figure 3 shows an example of the circuit around the heater, but the configuration is not limited to this. For example, part of the circuit may be configured in parallel, heater 35A and heater 35B may be connected in parallel, and in addition to the configuration in Figure 3, heaters other than heaters 35A and 35B may be connected in series or in parallel.

[0055] In the above-described embodiment, the heater is determined to be abnormal based on the degree of temperature rise detected by the temperature detection unit after the drive control unit starts driving the heater, but the system is not limited to this example. For example, the controller 22, which is the abnormality determination unit, may perform an abnormality determination process to determine whether the heater 35 is abnormal based on the degree of temperature decrease detected by the temperature detection unit after the drive control unit stops driving the heater 35. For example, the abnormality determination unit may determine that there is an abnormality if the temperature detected by the temperature detection unit does not fall by a certain value or more within a predetermined time after the drive control unit stops driving the heater. For example, when the power supply circuit 38 applies a DC voltage to the power line 39 and the switch 37 is ON, and the switch 37 switches from an ON state to an OFF state, the heater 35 may be determined to be normal (the heater was driven normally) if the difference (T3-T4) between the detected temperature T3 of the thermistor 27 at the time the switch 37 switches from ON to OFF or immediately before the switch switches from ON to OFF and the detected temperature T4 of the thermistor 27 at a predetermined time after the switch 37 switches from ON to OFF is greater than or equal to a certain value, and the heater 35 may be determined to be abnormal (the heater was not driven normally) if the difference (T3-T4) is less than a certain value. In this example, if the control unit 22A determines that the heater 35 is normal, it should perform the process in step S7 described above, and if it determines that the heater 35 is abnormal, it should perform the process in step S8 described above.

[0056] In the embodiment described above, the difference (T2-T1) was used as an indicator of the "degree of temperature rise," but for example, if the rate of temperature rise since the heater was started in step S3 (for example, the amount of temperature rise per unit time of the thermistor 27 detected) is above a certain value, it may be determined to be normal as in step S7, and if it is below a certain value, it may be determined to be abnormal as in step S8. Alternatively, when the power supply circuit 38 switches from an energized state (a state in which current is flowing to the heater 35) with a DC voltage applied to the power line 39 and the switch 37 is ON to a state in which the switch 37 is OFF, if the rate of temperature decrease (for example, the amount of temperature decrease per unit time of the thermistor 27 detected) is above a certain value, it may be determined to be normal as in step S7, and if it is below a certain value, it may be determined to be abnormal as in step S8.

[0057] In the above-described embodiment, a thermistor 27 is used as the temperature detection unit, but the configuration is not limited to this. For example, the temperature detection unit may be a thermistor positioned away from the water in the water pipe 9 to detect the ambient temperature inside the water heater 1. In this case, the water heater 1 can determine whether the heater 35 is abnormal based on the degree of rise in ambient temperature after the start of operation of the heater 35 that heats the water pipe 9, or the degree of decrease in ambient temperature after the stop of operation of the heater 35. When the heater 35 that heats the water pipe 9 is functioning normally, this is easily reflected in the ambient temperature after the start or stop of operation, so determining the abnormality of the heater 35 using the above method makes it easier to detect the abnormality of the heater 35 more quickly and accurately.

[0058] In the above-described embodiment, the temperature detection unit does not have to be thermistor 27 or a thermistor that detects ambient temperature. For example, it may be thermistor 25 or thermistor 26, or it may be thermistor 64 or thermistor 65.

[0059] In the above-described embodiment, an example of the inspection start condition is used, but the invention is not limited to this example. For example, in addition to the above-described inspection start condition, the condition that "a certain amount of time has elapsed since the last heater operation ended" may be added as an additional condition.

[0060] It should be noted that the embodiments disclosed herein are illustrative and not restrictive in all respects. The scope of the present invention is not limited to the embodiments disclosed herein, and is intended to include all modifications within the scope set forth in the claims or equivalents thereof. [Explanation of Symbols]

[0061] 1: Water heater 1A: Hot water supply system 2: Hot water supply circuit 3: Bathroom side circuit 4: Gas burner 6: Hot water side heat exchanger 7 :Primary heat exchanger 7a: Heat transfer tube 8:Secondary heat exchanger 8a: Heat transfer tube 9: Water pipe 10: Hot water outlet pipe 12: Inlet pipe 14: Bypass Road 16: Water inlet 18: Hot water outlet 20: Piping 22: Controller (Drive Control Unit) 22A: Control Unit 22B: Memory 22C:Communication Department 25: Thermistor 26: Thermistor 27: Thermistor (temperature detection unit) 32: Bypass valve 33: Water flow control valve 34: Water volume sensor 35: Heater 35A: Heater 35B: Heater 35Y: Resistor element 35Z: Resistor element 37: Switch (Drive Control Unit) 38: Power supply circuit 39: Power line 40: Gas pipe 42: Gas source solenoid valve 43: Hot water outlet pipe 44: Proportional control valve for hot water gas 46: Hot water switching solenoid valve 48: Fan 53: Switching Solenoid Valve 54: Gas burner 56: Heat exchanger on the bathroom side 57: Bath primary heat exchanger 58: Bath secondary heat exchanger 60: Bathtub 62: Circulation pump 63: Water flow sensor 64: Thermistor 65: Thermistor 66: Circulation piping 67: Piping 68: Piping 69: Piping 70: Drop-in pipe 72: Solenoid valve for hot water supply 74: Water volume sensor 80: Remote Controller 81: First remote controller 81A: Control Unit 81B: Display section 81C: Operating means 81D: Communications Department 81E: Audio output section 82: Second remote controller 82A: Control Unit 82B: Display section 82C: Operating means 82D: Communications Department 82E: Audio output section 90: Hot water combustion chamber S1: Step S2: Step S3: Step S4: Step S5: Step S6: Step S7: Step S8: Step T1: Temperature T2: Temperature

Claims

1. A gas burner that burns gas and supplies exhaust gas produced by the combustion of the gas, A heat exchanger comprising heat transfer tubes heated by the exhaust supplied from the gas burner, A water pipe having a water inlet for introducing water and a water inlet pipe provided between the heat transfer tube for supplying water to the heat transfer tube, and a hot water outlet pipe connected to the downstream side of the heat transfer tube for carrying hot water supplied from the heat transfer tube, forming a path for carrying hot and cold water, A heater for heating the aforementioned water pipe, A drive control unit that controls the drive of the heater, A temperature detection unit that detects temperature, An abnormality determination unit performs an abnormality determination process to determine whether the heater is abnormal or not, based on the degree of temperature rise detected by the temperature detection unit after the drive control unit starts driving the heater, or the degree of temperature decrease detected by the temperature detection unit after the drive control unit stops driving the heater. A water heater equipped with the following features.

2. The abnormality determination unit determines an abnormality if, within a predetermined time after the drive control unit starts driving the heater, the temperature detected by the temperature detection unit does not rise above a certain value, or if, within a predetermined time after the drive control unit stops driving the heater, the temperature detected by the temperature detection unit does not fall below a certain value. The water heater according to claim 1.

3. Equipped with multiple thermistors, The abnormality determination unit includes the short-range thermistor that is closest to the heater among the plurality of thermistors, The abnormality determination unit determines an abnormality in the heater based on the degree of temperature rise detected by the near-field thermistor after the drive control unit starts driving the heater, or the degree of temperature decrease detected by the near-field thermistor after the drive control unit stops driving the heater. A water heater according to claim 1 or claim 2.

4. The heater is provided at least at a predetermined position in the water pipe, The temperature detection unit is a thermistor that detects the temperature of the water in the water pipe. A water heater according to claim 1 or claim 2.

5. The heater is provided at least at a predetermined position in the water pipe, The temperature detection unit is a thermistor positioned at a distance from the water in the water pipe to detect the ambient temperature inside the water heater. A water heater according to claim 1 or claim 2.

6. The abnormality determination unit performs the abnormality determination process again if the operating time or number of operations since the previous abnormality or normal determination in the abnormality determination process exceeds a standard value. A water heater according to claim 1 or claim 2.

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