water heater

Abstract

Estimate the condition of the water heater's exhaust duct. [Solution] The water heater 1 includes a fan 49 that supplies air into the case 4Z (housing) by the rotation of the blades 48A, and a control unit 22A that adjusts the control amount for controlling the motor. The fan motor 48 rotates the blades 48A so as to increase the rotation speed of the rotating body when the control amount set by the control unit 22A increases, and decreases the rotation speed of the rotating body when the control amount decreases. The control unit 22A estimates the state of the exhaust passage 5 based on the rotation speed of the blades 48A when the control amount is set to a predetermined reference control amount, or based on the control amount when the rotation speed of the blades 48A is controlled to a predetermined reference rotation speed.

Description

[Technical Field]

[0001] This disclosure relates to water heaters. [Background technology]

[0002] Patent Document 1 discloses an example of a water heater. The water heater of Patent Document 1 comprises a gas burner unit, a heat exchanger, an inlet pipe, an outlet pipe, a fan that supplies combustion air to the gas burner unit, a detection unit that detects the actual rotational speed of the fan, and a control unit that controls the combustion of the gas burner unit and the rotation of the fan. The control unit changes the combustion stage of the gas burner unit when a change condition is met, and, according to information that defines a correspondence for each stage such that the target rotational speed of the fan increases as the amount of gas supplied increases, it feedback controls the rotational speed of the fan using a control amount determined by a feedback calculation using the target rotational speed and the actual rotational speed detected by the detection unit. [Prior art documents] [Patent Documents]

[0003] [Patent Document 1] Japanese Patent Publication No. 2024-92144 [Overview of the project] [Problems that the invention aims to solve]

[0004] Conventional water heaters, including the one disclosed in Patent Document 1, generally use a control unit to control the fan speed. In this type of water heater, the fan speed is affected by the condition of the exhaust passage located downstream of the fan, so there is a need for a method that can easily estimate the condition of the exhaust passage.

[0005] One of the purposes of this disclosure is to provide a technology that can estimate the condition of the exhaust duct of a water heater. [Means for solving the problem]

[0006] One of the disclosed items is a water heater, A burner that burns gas, A housing for the aforementioned burner, A heat exchanger comprising a heat transfer tube heated by the exhaust gas generated within the aforementioned containment, An exhaust passage that forms a path for discharging the exhaust gas that has passed through the heat exchanger, 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 fan comprising a rotating body and a motor that rotates the rotating body, which supplies air into the housing by the rotation of the rotating body, A control unit for adjusting the control amount for controlling the motor, Equipped with, The motor drives the rotating body to rotate such that it increases the rotational speed of the rotating body when the control amount set in the control unit increases, and decreases the rotational speed of the rotating body when the control amount decreases. The control unit estimates the state of the exhaust passage based on the rotational speed of the rotating body when the control amount is set to a predetermined reference control amount, or based on the control amount when the rotational speed of the rotating body is controlled to a predetermined reference rotational speed. [Effects of the Invention]

[0007] The technology disclosed herein can estimate the state of the exhaust duct of a water heater. [Brief explanation of the drawing]

[0008] [Figure 1] Figure 1 is an explanatory diagram illustrating a water heater according to the first embodiment. [Figure 2] Figure 2 is an explanatory diagram illustrating a schematic part of the electrical configuration of a water heater according to the first embodiment. [Figure 3] Figure 3 is a flowchart illustrating the flow of hot water supply control performed by a water heater according to the first embodiment. [Figure 4]Figure 4 is a graph showing the relationship between the gas supply amount (input request amount) and the target rotational speed at each combustion stage in the water heater according to the first embodiment. [Modes for carrying out the invention]

[0009] Each of the following [1] to [5] is an example of the technology included in this disclosure.

[0010] [1] A burner for burning gas, A housing for the aforementioned burner, A heat exchanger comprising a heat transfer tube heated by the exhaust gas generated within the aforementioned containment, An exhaust passage that forms a path for discharging the exhaust gas that has passed through the heat exchanger, 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 fan comprising a rotating body and a motor that rotates the rotating body, which supplies air into the housing by the rotation of the rotating body, A control unit for adjusting the control amount for controlling the motor, Equipped with, The motor drives the rotating body to rotate such that it increases the rotational speed of the rotating body when the control amount set in the control unit increases, and decreases the rotational speed of the rotating body when the control amount decreases. The control unit estimates the state of the exhaust passage based on the rotational speed of the rotating body when the control amount is set to a predetermined reference control amount, or based on the control amount when the rotational speed of the rotating body is controlled to a predetermined reference rotational speed. Water heater.

[0011] The water heater described in [1] above allows for the estimation of the exhaust duct condition using a simple method. In this water heater, when the control unit sets the control amount to a predetermined standard control amount, the greater the gas flow load in the exhaust duct, the lower the rotational speed of the rotating body becomes, and the smaller the gas flow load in the exhaust duct, the greater the rotational speed of the rotating body becomes. Therefore, the exhaust duct condition can be estimated more accurately using a simple method by estimating based on the rotational speed of the rotating body when the control amount is set to a predetermined standard control amount, or based on the control amount used to control the rotational speed of the rotating body to a predetermined standard rotational speed.

[0012] [2] The control unit determines whether an external exhaust passage outside the water heater is connected to the exhaust passage based on the rotational speed of the rotating body when the control amount is set to a predetermined reference control amount, or based on the control amount when the rotational speed of the rotating body is controlled to a predetermined reference rotational speed. The water heater described in [1].

[0013] The water heater described in [2] above can obtain a useful determination result regarding whether or not the external exhaust passage outside the water heater is connected to the exhaust passage, and this determination result can be put to use in the water heater.

[0014] [3] When the control unit determines that the external exhaust passage is connected to the exhaust passage, it increases the control amount compared to when it determines that it is not connected. The water heater described in [2].

[0015] In the water heater described in [3] above, when controlled with the same control amount, the flow load is greater when the external exhaust passage is connected to the exhaust passage than when it is not, so the rotational speed of the rotating body decreases. Therefore, if it is determined that the external exhaust passage is connected to the exhaust passage, increasing the control amount compared to when it is determined that it is not connected will suppress the decrease in rotational speed caused by the external exhaust passage being connected to the exhaust passage.

[0016] [4] The control unit estimates the length of the external exhaust passage outside the water heater based on the rotational speed of the rotating body when the control amount is set to a predetermined reference control amount, or based on the control amount when the rotational speed of the rotating body is controlled to a predetermined reference rotational speed. The water heater described in [1].

[0017] The water heater described in [4] above can obtain useful information such as "the length of the external exhaust passage outside the water heater." When controlled by a standard control amount, the longer the external exhaust passage connected to the exhaust passage, the greater the load and the lower the rotational speed of the rotating body. Alternatively, when controlling the rotational speed of the rotating body to the standard rotational speed, the longer the external exhaust passage connected to the exhaust passage, the greater the load, and therefore the required control amount increases. Thus, the water heater described in [4] above can use this characteristic to obtain useful information such as "the length of the external exhaust passage outside the water heater" in a simpler way.

[0018] [5] The control unit increases the control amount as the estimated length of the external exhaust passage increases. The water heater described in [4].

[0019] In the water heater described in [5] above, when controlled with the same control amount, the longer the external exhaust passage connected to the exhaust passage, the greater the flow load, and therefore the lower the rotational speed of the rotating body. Therefore, if the control is performed so that the control amount increases as the estimated length of the external exhaust passage increases, it is easier to suppress the decrease in rotational speed caused by the external exhaust passage being connected to the exhaust passage more effectively.

[0020] <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 that has the function of supplying hot water to the bathtub 60 and the hot water outlet 18, and the function of heating the water in the bathtub, and mainly comprises a hot water supply circuit 2 and a bath side circuit 3. The hot water supply circuit 2 is equipped with an inlet pipe 12, an outlet pipe 10, a gas burner section 4, a hot water supply heat exchanger 6 (heat exchanger), etc., and functions as a path for heating tap water supplied from the outside and dispensing it as hot water. The bath side circuit 3 is equipped with a gas burner 54 (bath side burner), a bath side heat exchanger 56, piping 66, a circulation pump 62, thermistors 64, 65, etc., and is used for circulating heating during automatic bath filling, reheating the bath, etc.

[0021] In the hot water supply circuit 2, the pipeline consisting of the inlet pipe 12, heat transfer pipe 8a, piping 20, heat transfer pipe 7a, and outlet pipe 10 functions as the hot water supply passage. The inlet pipe 12 is configured as the path through which water flows in from the inlet 16, and the outlet pipe 10 is connected to the downstream side of the heat transfer pipe 7a and is configured as the path that sends the hot water supplied from the heat transfer pipe 7a to the outlet 18. The gas burner section 4 is the part that burns gas (combustion gas) to generate exhaust gas. The hot water supply side heat exchanger 6 is an example of a heat exchanger and is the part that heats water by transferring heat generated in the gas burner section 4 to the water passing through the hot water supply side water passage (a pipeline consisting of an inlet pipe 12, a heat transfer pipe 8a, a pipe 20, a heat transfer pipe 7a, and a hot water outlet pipe 10). It is located in the middle of the hot water supply side water passage and functions to transfer heat generated by combustion in the gas burner section 4 to the water passing through the inside of the hot water supply side water passage. The hot water supply side heat exchanger 6 is heated by the exhaust generated by the combustion of gas in the gas burner section 4. 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 section 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.

[0022] In the hot water supply circuit 2, an inlet pipe 12 is connected to the inlet of the secondary heat exchanger 8 to supply tap water. The inlet pipe 12 is equipped with a thermistor 25 as a water temperature detection unit to detect the temperature of the water passing through the inlet pipe 12 (i.e., the water temperature at a position upstream of the heat exchanger in the water supply pipe) and a water flow sensor 34 as a water flow detection unit to detect the amount of water flowing through the inlet pipe 12 (i.e., the amount of water flowing through the water supply pipe). Downstream of the inlet pipe 12, the heat transfer tubes 8a of the secondary heat exchanger 8 are connected, and further downstream, a pipe 20 is connected that connects the heat transfer tubes 8a of the secondary heat exchanger 8 to the heat transfer tubes 7a of the primary heat exchanger 7. The heat transfer tubes 7a of the primary heat exchanger 7 are connected to this pipe 20, and a hot water outlet pipe 10 is connected to the outlet of the primary heat exchanger 7 to discharge the hot water heated by the primary heat exchanger 7. The outlet pipe 10 is equipped with a thermistor 26 for detecting the temperature of the water inside the outlet pipe 10. In this configuration, the inlet pipe 12, heat transfer pipe 8a, piping 20, heat transfer pipe 7a, and outlet pipe 10 correspond to an example of a water passage, and function as a flow path for water introduced from a water supply (not shown) located outside the water heater 1.

[0023] 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. Specifically, the primary heat exchanger 7 is equipped with heat transfer tubes 7a that serve as water passages within the primary heat exchanger 7, and transfers the combustion heat contained in the combustion exhaust generated in the gas burner section 4 to the water passing through the heat transfer tubes 7a, thereby exchanging heat by transferring sensible heat energy to the water. The secondary heat exchanger 8 is equipped with heat transfer tubes 8a that serve as water passages within the secondary heat exchanger 8, and transfers the combustion heat from the combustion exhaust generated in the gas burner section 4 after it has passed through the primary heat exchanger 7 to the water passing through the heat transfer tubes 8a, thereby exchanging heat by transferring latent heat energy to the water.

[0024] 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 greater than that of 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 equipped with a motor whose rotation angle of the drive shaft is controlled by instructions from the control unit 22A, and is configured to continuously change the opening degree of the inlet pipe 12 between a closed state and a fully open state. In this configuration, the water flow rate control valve 33 functions to adjust the amount of water flowing through the water pipe.

[0025] The gas flow path 40 that supplies gas to the gas burner section 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, etc., from the upstream side. The gas flow path 40 includes a main flow path 40A whose upstream end is connected to the gas supply source, and branch flow paths 40B, 40B, etc., which are connected to the downstream end of the main flow path 40A and branch off from the main flow path 40A toward each gas burner section 4. The gas source solenoid valve 42 corresponds to an example of a first solenoid valve and is installed in the main flow path 40A, and switches between an open state that opens the main flow path 40A (gas flow path 40) and a closed state that closes the main flow path. When the gas source solenoid valve 42 is in the open state, gas can flow from the upstream side to the downstream side of the gas source solenoid valve 42. When the gas source solenoid valve 42 is in the closed state, gas cannot flow from the upstream side to the downstream side of the gas source solenoid valve 42. The hot water switching solenoid valves 46, 46... are provided in each branch passage 40B, 40B... Each of the hot water switching solenoid valves 46, 46... corresponds to an example of a second solenoid valve and switches between an open state, opening the gas passage 40, and a closed state, closing it, at a position downstream of the gas source solenoid valve 42. When the hot water switching solenoid valve 46 is in the open state, gas can flow from the upstream side to the downstream side of the hot water switching solenoid valve 46. When the hot water switching solenoid valve 46 is in the closed state, gas cannot flow from the upstream side to the downstream side of the hot water switching solenoid valve 46. 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 section 4. A switching solenoid valve 53 is provided in the bath-side branch passage 40C from the gas passage 40 connected to the gas burner 54 (bath-side burner).

[0026] The water heater 1 includes a hot water ignition plug 35, a hot water flame rod 36, a bath ignition plug 37, and a bath flame rod 38.

[0027] The water heater 1 is equipped with a fan 48. The fan 48 comprises a blade section 48A with multiple blades and a fan motor 49 that rotates this blade section 48A. The fan 48 corresponds to an example of a blower and performs the operation of sending air into the hot water heat exchanger 6. The blade section 48A corresponds to an example of a rotating body. The fan 48 is located below the hot water combustion chamber 90 and supplies combustion air to each gas burner section 4 (burner) and gas burner 54 (bath-side burner). That is, the gas burner section 4 and gas burner 54 are located at the destination of the air sent out from the fan 48. The fan motor 49 has a drive shaft fixed to the blade section 48A, and the controller 22 controls the rotation of the drive shaft of the fan 48.

[0028] In this embodiment, the outer surface of the hot water combustion chamber 90 is composed of the case 4Z of the gas burner unit 4 (combustion device), the cases 6Z of the hot water side heat exchanger 6 and the bath side heat exchanger 56, and the exhaust passage 5. Case 4Z corresponds to an example of a housing. Air sent out by the fan 48 is supplied into the case 4Z of the gas burner unit 4 (combustion device), the gas that has passed through case 4Z is supplied into case 6Z, and the gas that has passed through case 6Z is discharged to the outside of the water heater 1 through the exhaust passage 5. The exhaust passage 5 may be connected to an external exhaust passage that communicates with the exhaust port 5A, which is the outlet, or the exhaust port 5A may be exposed to the space outside the water heater 1 without an external exhaust passage being connected.

[0029] In the bath-side circuit 3, the piping 66 includes a supply pipe 67 for guiding water from the bathtub 60 to the bath-side heat exchanger 56, a return pipe 68 for guiding water from the bath-side heat exchanger 56 to the bathtub 60, and an intermediate pipe 69 connected to the supply pipe 67 and the return pipe 68 and passing through the bath-side heat exchanger 56. The bath-side heat exchanger 56 includes a primary bath heat exchanger 57 and a secondary bath heat exchanger 58, and functions to transfer heat generated by the gas burner 54 (bath-side burner) to the water passing through the piping 66. The supply pipe 67 is connected to the circulation pump 62 and the water passing through the supply pipe 67. A thermistor 64 (bath thermistor) is provided to detect the temperature. The circulation pump 62 is a device that moves the water in the piping 66. A drop pipe 70, which is branched from the hot water outlet pipe 10, is connected to the return pipe 68, and a hot water solenoid valve 72 and a drop water volume sensor 74 are provided in the drop pipe 70. The drop pipe 70 is the path through which hot water flows from the hot water side water passage of the hot water side circuit 2 to the piping 66 (circulation path) of the bath side circuit 3.

[0030] The water heater 1 is equipped with a controller 22 as shown in Figures 1 and 2. The controller 22 shown in Figure 2 comprises a control unit 22A, which is configured as, for example, a known microcomputer; a memory 22B, which is configured as a known semiconductor memory; and a communication unit 22C, which is configured as an interface for communication with the outside. 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, and can control various actuators provided in the hot water supply circuit 2 and the bath side circuit 3.

[0031] As shown in Figure 2, the multiple remote controllers 80 are arranged in a configuration that allows them to communicate with the controller 22. In the example in Figures 1 and 2, the multiple remote controllers 80 include a first remote controller 81 installed in the bathroom and a second remote controller 82 installed in a different location (e.g., 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, an operation unit 81C provided with multiple known switches such as push buttons, 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 operation unit 81C is composed of multiple operation units and is used for input operations such as switching the power on / off state and switching the set temperature. The second remote controller 82 is similar, and 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, an operation unit 82C provided with a plurality of known switches such as push buttons, 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.

[0032] 2. Standard hot water supply control (basic control) The control unit 22A performs hot water supply control in a flow similar to that shown in Figure 3. After power is turned on, the control unit 22A executes the hot water supply control shown in Figure 3 and determines in step S11 whether the combustion start condition has been met. The combustion start condition may be, for example, "the amount of water detected by the water volume sensor 34 (for example, the amount of water per unit time) (hereinafter also simply referred to as "water volume") is equal to or greater than a predetermined threshold," or it may be another condition. The control unit 22A remains in a standby state until the combustion start condition is met, and in this standby state, it repeats the determination of No in step S11.

[0033] If the control unit 22A determines in step S11 that the combustion start conditions have been met (S11: Yes), it executes the ignition process in step S12. In the ignition process in step S12, the control unit 22A activates an igniter (not shown) to discharge from the hot water spark plug 35, opens the gas source solenoid valve 42 and the hot water switching solenoid valves 46, 46..., and sets the hot water gas proportional control valve 44 to a slow ignition operation to ignite the gas burner unit 4. After performing the operation to ignite the gas burner unit 4 in this way, the control unit 22A determines whether or not combustion of the gas burner unit 4 has been detected by the hot water flame rod 36, and if it determines that combustion has been detected, it terminates the slow ignition operation and ends the ignition process (S12).

[0034] After the ignition process in step S12 is completed, the control unit 22A determines in step S13 whether the combustion termination condition has been met. The combustion termination condition may be, for example, "the amount of water detected by the water volume sensor 34 (for example, the amount of water per unit time) is less than a predetermined threshold," or it may be another condition (such as a predetermined operation being performed to instruct the water heater 1 to terminate combustion, or a predetermined stop condition being met as a condition for stopping combustion).

[0035] If the control unit 22A determines in step S13 that the combustion termination condition has not been met (S13: No), it calculates the gas supply amount (input request amount) in step S14. In step S14, the control unit 22A calculates the gas supply amount (input request amount) using a known calculation method based on the amount of water (inlet water) detected by the water volume sensor 34 at the time of execution of step S14 or immediately before execution, the set temperature set as the target temperature, and the temperature (outlet temperature) detected by the thermistor 26. The method for calculating the gas supply amount (input request amount) can be any feedback calculation that brings the outlet temperature closer to the set temperature, for example, it may be a method such as the one disclosed in Japanese Patent Application Publication No. 2010-117053, or a method such as the one disclosed in Japanese Patent Application Publication No. 2018-200123, or any other known method.

[0036] Furthermore, in step S14, the control unit 22A calculates the gas supply amount (input request amount) based on the above calculation, and determines the target rotational speed based on the calculated gas supply amount (input request amount).

[0037] In a typical example, the burner groups 4A, 4B, and 4C that make up the gas burner section 4 consist of multiple burners with different numbers from each other. Of the burner groups 4A, 4B, and 4C, burner group 4A has the most gas burners, burner group 4B has the fewest gas burners, and burner group 4C has fewer gas burners than burner group 4A but more than burner group 4B. In controlling the hot water temperature, the controller 22 performs switching control, switching the combustion stage of the gas burner unit 4 (hereinafter also referred to as the combustion stage or combustion phase) in five stages according to the required gas supply amount (input request amount). This is done as follows: Stage 1 is single combustion of only burner group 4B, which has the fewest number of burners; Stage 2 is single combustion of only burner group 4C, which has the next largest number of burners; Stage 3 is simultaneous combustion of burner groups 4B and 4C, which have the next largest number of burners; Stage 4 is single combustion of burner group 4A, which has the next largest number of burners; and Stage 5 is full combustion of burner groups 4A to 4C, which have the largest number of burners.

[0038] In a typical example, as shown in Figure 4, a correspondence between the gas supply amount (input request amount) and the target fan speed is predetermined for each combustion stage. In all of these correspondences for each combustion stage, the larger the gas supply amount (input request amount), the higher the target fan speed. The information for each correspondence for each combustion stage is stored in memory 22B or similar as a calculation formula or table that determines the target fan speed based on the gas supply amount (input request amount). Once the combustion stage and gas supply amount are determined, the target fan speed corresponding to the combustion stage and gas supply amount is identified using this information.

[0039] For example, in the above information, the upper limit of the input requirement for the first combustion stage (first upper limit) is greater than the lower limit of the input requirement for the second combustion stage (second lower limit), the upper limit of the input requirement for the second combustion stage (second upper limit) is greater than the lower limit of the input requirement for the third combustion stage (third lower limit), the upper limit of the input requirement for the third combustion stage (third upper limit) is greater than the lower limit of the input requirement for the fourth combustion stage (fourth lower limit), and the upper limit of the input requirement for the fourth combustion stage (fourth upper limit) is greater than the lower limit of the input requirement for the fifth combustion stage (fifth lower limit). In the above information, the target rotational speed when the input requirement for the first combustion stage is at the upper limit (first upper limit) is greater than the target rotational speed when the input requirement for the second combustion stage is at the lower limit (second lower limit). The target rotational speed at the upper limit of the input requirement for the second combustion stage (second upper limit) is greater than the target rotational speed at the lower limit of the input requirement for the third combustion stage (third lower limit). The target rotational speed at the upper limit of the input requirement for the third combustion stage (third upper limit) is greater than the target rotational speed at the lower limit of the input requirement for the fourth combustion stage (fourth lower limit). The target rotational speed at the upper limit of the input requirement for the fourth combustion stage (fourth upper limit) is greater than the target rotational speed at the lower limit of the input requirement for the fifth combustion stage (fifth lower limit).

[0040] If the gas supply amount calculated in step S14 is within the range of the gas supply amount (input request amount) for the combustion stage at the time of step S14 (specifically, if it is above the lower limit and below the upper limit of the input request amount in the correspondence information that defines the correspondence between the input request amount and the target rotational speed for that combustion stage), the control unit 22A does not switch the combustion stage and determines the target rotational speed based on the correspondence between the gas supply amount and the target rotational speed determined in association with the combustion stage at the time of step S14. For example, if the combustion stage at the time of step S14 is the second stage, and the gas supply amount calculated in step S14 is above the lower limit and below the upper limit of the range of gas supply amount for the second stage, the control unit 22A does not switch the combustion stage from the second stage and determines the target rotational speed associated with the gas supply amount calculated in step S14 in the correspondence relationship (information such as the calculation formula showing the relationship indicated by symbol L2 in Figure 4) based on the correspondence between the gas supply amount and the target rotational speed determined in association with the combustion stage (second stage) at the time of step S14.

[0041] On the other hand, if the gas supply amount calculated in step S14 is outside the range of the gas supply amount for the combustion stage at the time of step S14, the combustion stage is switched, and the target rotational speed is determined based on the correspondence between the gas supply amount determined in accordance with the switched combustion stage and the target rotational speed. For example, if the combustion stage at the time of step S14 is the second stage, and the gas supply amount calculated in step S14 is less than the lower limit of the gas supply amount range for the second stage and within the range of the gas supply amount for the first stage, the combustion stage is switched to the first stage, and the target rotational speed corresponding to the gas supply amount calculated in step S14 in that correspondence is determined based on the correspondence between the gas supply amount determined in accordance with the switched combustion stage (first stage) and the target rotational speed (information such as the calculation formula showing the relationship of symbol L1 in Figure 4). Alternatively, if the combustion stage at step S14 is the second stage, and the gas supply amount calculated in step S14 exceeds the upper limit of the range for the second stage gas supply amount but is within the range for the third stage gas supply amount, the combustion stage is switched to the third stage, and the target rotational speed is determined based on the correspondence between the gas supply amount determined in accordance with the switched combustion stage (third stage) and the target rotational speed (information such as the calculation formula showing the relationship indicated by symbol L3 in Figure 4), in which case the target rotational speed corresponding to the gas supply amount calculated in step S14 is determined.

[0042] Thus, the control unit 22A determines the target rotational speed N based on the gas supply amount (input request amount) obtained in step S14 and the corresponding information described above. t Determine N t This is the target rotational speed determined in step S14.

[0043] In step S14, the control unit 22A determines the gas supply amount and the target rotation speed N. tAfter determining this, the process proceeds to step S15, and it is determined whether or not a decision to switch the combustion stage was made in step S14. When the control unit 22A determines in step S15 that a decision not to switch the combustion stage was made, the process proceeds to step S16, and the control amount (operation amount) is determined by the first feedback operation. When the control unit 22A determines in step S15 that a decision to switch the combustion stage was made, the process proceeds to step S17, and the control amount (operation amount) is determined by the second feedback operation. If the fan motor 49 is, for example, a DC motor and the rotational speed increases as the applied voltage increases, the control amount (operation amount) may be the voltage applied to the motor. If it is a motor driven by PWM control and the rotational speed increases as the duty increases, the control amount (operation amount) may be the duty.

[0044] In a representative example, a rotational speed sensor 50 for detecting the rotational speed of the fan 48 is provided, and the rotational speed of the fan 48 can be actually measured. The rotational speed sensor 50 corresponds to an example of a sensor. The rotational speed of the fan 48 detected by the rotational speed sensor 50 is the actually measured rotational speed. The rotational speed of the fan 48 detected by the rotational speed sensor 50 is the rotational speed of the shaft of the fan motor 49 and is also the rotational speed of the blade part 48A (rotating body). Specifically, it is a value indicating how many rotations the shaft of the fan motor 49 makes per unit time (for example, one minute). As long as the rotational speed sensor 50 is configured to be able to detect the rotational speed of the fan 48, various known sensors can be adopted.

[0045] In step S16, the control unit 22A uses the target rotational speed N determined in step S14 t and the actually measured rotational speed N detected by the rotational speed sensor 50 (detection unit) at the current time point of step S16 or immediately before this step S16 n to calculate the control amount by the first feedback operation. The control amount is a value of an index for increasing or decreasing the rotational speed of the fan motor 49. The first feedback operation calculates the deviation (N t - N n between the target rotational speed N t and the actually measured rotational speed N n) and proportional gain K a Based on this, proportional control quantity X n The proportional operation that determines the difference, and the difference value obtained by the difference equation and the differential gain K b Based on this, the differential control variable Y n This includes differential and integral operations that determine the result.

[0046] The above proportional calculation formula uses a predetermined fixed value, proportional gain K. a , the target rotational speed N determined in the most recent step S14 t , the current step S16 or the measured rotational speed N detected immediately before step S16 n Based on this, the proportional control quantity X is given by the following equation (Equation 1). n This is represented. X n =K a × (N t -N n )···(Math 1)

[0047] The first equation, which is one of the differential equations, is the differential gain K, which is a predetermined fixed value. b The proportional control quantity X obtained in the calculation of step S16 is... n The previous proportional control amount X calculated in the feedback calculation performed in the previous step S16 (either step S16 or step S17) n-1 Based on this, the differential control variable Y is given by the following equation (Equation 2). n This is represented. Y n =K b × (X n -X n-1 )···(Math 2)

[0048] The above integral calculation formula is derived from the previous integral control amount Z calculated in the feedback calculation performed before the calculation in step S16 (either step S16 or step S17). n-1 The differential control variable Y obtained in the calculation of step S16 is shown here. n , the integral gain K is a predetermined fixed value. d The proportional control quantity X obtained in the calculation of step S16 is...n Based on this, the integral control quantity Z is given by the following equation (Mathematics 3) n This is represented. Z n = Z n-1 +Y n +K d × (X n -Z n-1 )···(Math 3)

[0049] In the first feedback operation of step S16, Z used in equations 1, 2, and 3 above n , Y n , X n , Z n-1 , K d And each coefficient K is a predetermined fixed value. p , K i Based on this, the controlled variable (manipulated variable) P is given by the following equation (Equation 4). n We seek P. n-1 This is the previous controlled variable (operated variable) calculated in the feedback calculation (either step S16 or step S17) performed prior to the calculation in step S16. P n =K p ×(K i ×Z n +Y n +K d × (X n -Z n-1 ))+P n-1 ...(Math 4)

[0050] In step S17, the control unit 22A determines the target rotational speed N determined in step S14. t And the actual rotational speed N detected by the rotational speed sensor 50 (detection unit) at the current step S17 or immediately before step S17. n The controlled variable (manipulated variable) is calculated by a second feedback calculation using the following. The second feedback calculation also uses the target rotational speed N t and the measured rotational speed N n The deviation (N) t -N n ) and proportional gain K aA proportional operation that determines a proportional control amount based on this, a differential operation that determines a differential control amount based on the differential value obtained by a difference formula, and an integral operation are included. b In the second feedback operation as well, the proportional control amount X is obtained by the above formula (1). On the other hand, instead of the above formula (2), the following formula (5) using the above proportional gain K, the above differential gain K, the current measured rotational speed N detected by the rotational speed sensor 50 (detection unit) at the time of the current step S17 or immediately before this step S17, and the previous measured rotational speed N detected by the rotational speed sensor 50 (detection unit) at the time of the previous feedback operation (either step S16 or step S17) of the current step S17 or immediately before that is used to obtain the differential control amount Y.

[0051] In the second feedback operation as well, the proportional control amount X is obtained by the above formula (1). n On the other hand, instead of the above formula (2), the above proportional gain K, a the above differential gain K, b the current measured rotational speed N detected by the rotational speed sensor 50 (detection unit) at the time of the current step S17 or immediately before this step S17, n the previous measured rotational speed N detected by the rotational speed sensor 50 (detection unit) at the time of the previous feedback operation (either step S16 or step S17) of the current step S17 or immediately before that, n-1 and are used to obtain the differential control amount Y by the following formula (5). n Y n =K a ×K b ×(N n-1 -N n )···(Formula 5)

[0052] In the second feedback operation, based on X, Y obtained by the above formulas (1) and (5), the previous integral control amount Z calculated in the previous feedback operation (either step S16 or step S17) performed before the operation of the current step S17, and the above integral gain K, the current integral control amount Z is obtained by the following formula (3). Z n 、Y n 、the previous integral control amount Z calculated in the previous feedback operation (either step S16 or step S17) performed before the operation of the current step S17, n-1 the above integral gain K, d is used to obtain the current integral control amount Z by the following formula (3). n Z n =Z n-1 +Y n +K d ×(X n -Z n-1 )···(Formula 3)

[0053] In the second feedback operation, Z, Y, X used in the above formulas (1), (3), and (5) n 、Y n 、X​n , Z n-1 , K d and the above coefficient K p , K i Based on the above and the following Equation 4, the control quantity P n is obtained. P n-1 is the previous control quantity (operation quantity) calculated by the feedback operation (either in step S16 or step S17) performed in the previous operation of step S17 this time. P n = K p × (K i × Z n + Y n + K d × (X n - Z n-1 )) + P n-1 ···(Equation 4) <--<--<-- n-1 and the current proportional control quantity X n Using the first equation for differential operation that calculates the difference between the current proportional control quantity X b as the difference value (specifically, the equation obtained by multiplying the difference between the current proportional control quantity and the previous proportional control quantity by the differential gain K n = K b × (X n - X n-1 ) to calculate the differential control quantity Y n . On the other hand, when the condition for changing the combustion stage of the gas burner unit 4 is satisfied (Yes in step S15), the differential operation equation using the second equation that calculates the difference between the previous measured rotation speed N n-1 and the current measured rotation speed N n as the difference value (specifically, the equation obtained by multiplying the difference between the current measured rotation speed and the previous measured rotation speed by the proportional gain K a and the differential gain K b ) is Y n = K a × K b × (N n-1 - N n ) to calculate the differential control quantity Yn Calculate.

[0055] After step S16 or step S17, the control unit 22A proceeds to step S18, and in principle, the control variable (operated variable) P determined in step S16 or S17 n The fan 48 is rotated, and the hot water switching solenoid valves 46, 46... and the hot water gas proportional control valve 44 are adjusted so that the gas supply amount (input request amount) determined in step S14 is achieved. Note that P x P n When used in place of the above, in step S18, the controlled variable (manipulated variable) P x The control unit 22A rotates the fan 48 and adjusts the hot water switching solenoid valves 46, 46... and the hot water gas proportional control valve 44 so that the gas supply amount (input request amount) determined in step S14 is the same as the fan speed 48 and the hot water gas proportional control valve 44. After the control unit 22A starts adjusting the fan speed and gas supply amount in step S18, it returns to step S13 to determine whether the combustion termination condition has been met. If the control unit 22A determines in step S13 that the combustion termination condition has been met, it proceeds to step S19, closes the gas source solenoid valve 42 and the hot water switching solenoid valves 46, 46... and stops the combustion operation.

[0056] 3. Estimation of the exhaust system condition The control unit 22A adjusts the control amount for controlling the fan motor 49 in the manner described above during normal combustion operation of the gas burner unit 4. Specifically, the control unit 22A adjusts the control amount P described above. n The rotation of the fan motor 49 is controlled by the control amount P set by the control unit 22A. n As the control amount P increases, the rotational speed of the shaft of the fan motor 49 (i.e., the rotational speed of the blade portion 48A (rotating body)) increases, and the control amount P nThe shaft and the blade section 48A (rotating body) are driven to rotate such that the rotational speed of the shaft (i.e., the rotational speed of the blade section 48A (rotating body)) decreases as the amount decreases. For example, if the space outside the water heater 1 is windless and the exhaust port 5A is exposed to the outside space without an external exhaust passage connected to the exhaust passage 5, the fan motor 49 rotates at a predetermined reference rotational speed when the control unit 22A rotates the fan motor 49 by a predetermined reference control amount.

[0057] The control unit 22A performs estimation processing to estimate the state of the exhaust passage 5 at a predetermined inspection timing. The inspection timing may be the switching timing when the water heater 1 switches from a state where it is not receiving power from an external power source to a state where it is receiving power, the timing when the water heater 1 first performs hot water supply operation after this switching timing, the timing when a certain period of time has elapsed since the end of the previous operation of the water heater 1, or any other timing.

[0058] When the above-mentioned inspection timing arrives, the control unit 22A operates in inspection mode to rotate the fan motor 49 by a predetermined reference control amount.

[0059] In a typical example of this embodiment, in inspection mode, the control unit 22A controls the above-mentioned control quantity P n The fan motor 49 is driven by setting the control to a predetermined reference control amount, and the rotational speed (rotational speed of the blade section 48A (rotating body)) detected by the rotational speed sensor 50 when the fan motor 49 is driven by the reference control amount is acquired. Then, the control unit 22A estimates the state of the exhaust passage 5 based on the rotational speed acquired in this way (the measured rotational speed in inspection mode).

[0060] Specifically, the control unit 22A controls the control amount P when in the above inspection mode. nWhen the fan motor 49 is driven with the above reference control amount set, if the rotational speed detected by the rotational speed sensor 50 (measured rotational speed) is smaller than a predetermined rotational speed reference value, it is determined that the external exhaust passage outside the water heater 1 is connected to the exhaust passage 5. If the measured rotational speed is equal to or greater than the above rotational speed reference value, it is determined that the external exhaust passage outside the water heater 1 is not connected to the exhaust passage 5. The above rotational speed reference value is a value greater than 0 and smaller than the above reference rotational speed.

[0061] The control unit 22A controls the control amount P when in the above inspection mode. n When the fan motor 49 is driven with the above reference control amount set, if the rotational speed detected by the rotational speed sensor 50 (measured rotational speed) is smaller than the rotational speed reference value, the length of the external exhaust passage outside the water heater 1 is estimated based on the measured rotational speed.

[0062] As a method for estimating the length, for example, the numerical range greater than 0 and less than or equal to the above rotational speed reference value is divided into multiple ranges, and a length level is determined for each group such that the smaller the value, the higher the level of the external exhaust passage length, and if the measured rotational speed obtained in inspection mode falls within any of these ranges, the length level of the external exhaust passage is determined to be the level corresponding to that range. For example, the control unit 22A sets the rotational speed reference value to Xa, and the range less than or equal to Xa and greater than Xb to be the first group, the range less than or equal to Xb and greater than Xc to be the second group, and the range less than or equal to Xc to be the third group. Then, if the measured rotational speed obtained in inspection mode falls within the range of the first group, the control unit 22A determines the length level of the external exhaust passage to be the "first level", if the measured rotational speed obtained in inspection mode falls within the range of the second group, it determines the length level of the external exhaust passage to be the "second level", which is longer than the first level, and if the measured rotational speed obtained in inspection mode falls within the range of the third group, it determines the length level of the external exhaust passage to be the "third level", which is longer than the second level.

[0063] In this way, the control unit 22A determines whether or not the external exhaust passage is connected to the exhaust passage 5, and if it is determined that it is connected, it estimates the length of the external exhaust passage. Then, when the control unit 22A determines that the external exhaust passage is connected to the exhaust passage 5, it increases the control amount compared to when it is determined that it is not connected, and adjusts the control amount so that the longer the estimated length of the external exhaust passage, the greater the control amount. For example, when it is determined that the external exhaust passage is not connected to the exhaust passage 5, the control amount P calculated in each calculation in both the first feedback calculation and the second feedback calculation is... n The rotational speed of the fan motor 49 is controlled using this. Meanwhile, when the control unit 22A determines that the external exhaust passage is connected to the exhaust passage 5, the control amount P calculated in each calculation in both the first and second feedback calculations is used. n Instead, P x The control variable is used. For example, if the measured rotational speed is within the range of the first group, P x =α×P n If the measured rotational speed is within the range of the second group, then P x =β×P n If the measured rotational speed is within the range of the third group, then P x =γ×P n The relationship between α, β, and γ is set, for example, 1 < α < β < γ, and the calculated control variable P increases as the level (degree) of length increases. n Correction control amount P to correct to a larger value x Determine this and use it as the above-mentioned controlled variable P n Instead, use this in step S18.

[0064] 4. Another example The above explanation describes one example of an inspection mode, but other methods such as the following example may also be used. In the alternative inspection mode, the control unit 22A controls the rotational speed of the blade section 48A (rotating body) to the above-mentioned reference rotational speed, and estimates the state of the exhaust passage 5 based on the control amount when the rotational speed is controlled to the reference rotational speed in this way. Specifically, the control unit 22A controls the control amount so that the rotational speed of the blade section 48A (rotating body) becomes the above-mentioned reference rotational speed, and obtains the control amount when the rotational speed of the blade section 48A (rotating body) is stable at the above-mentioned reference rotational speed for a certain period of time. Then, the control unit 22A estimates the state of the exhaust passage 5 based on the control amount obtained in this way (the control amount when it is stable at the reference rotational speed).

[0065] Specifically, in the inspection mode, the control unit 22A determines that the external exhaust passage outside the water heater 1 is connected to the exhaust passage 5 if the control amount (measured control amount) obtained when controlling the rotation speed of the blade section 48A (rotating body) to stabilize it at the above reference rotation speed is greater than or equal to a predetermined control amount reference value, and determines that the external exhaust passage outside the water heater 1 is not connected to the exhaust passage 5 if the measured control amount is less than the above control amount reference value. The above control amount reference value is a value greater than the above reference control amount.

[0066] When the control unit 22A controls the rotation speed of the blade section 48A (rotating body) to stabilize it at the above reference rotation speed during the inspection mode, if the control amount (measured control amount) is greater than the control amount reference value, it estimates the length of the external exhaust passage outside the water heater 1 based on the measured control amount.

[0067] As a method for estimating the length, for example, the numerical range above the control variable reference value is grouped into multiple ranges, and a length level is determined for each group such that the larger the value, the higher the level of the external exhaust passage length. If the measured control variable obtained in inspection mode falls within any of these ranges, the length level of the external exhaust passage is determined to be the level corresponding to that range. For example, the control unit 22A sets the control variable reference value to Xd, and the range between Xd and less than Xe is designated as the first group, the range between Xe and less than Xf as the second group, and the range above Xf as the third group. Then, the control unit 22A determines the length level of the external exhaust passage to be the "first level" if the measured control variable obtained in inspection mode falls within the range of the first group, determines the length level of the external exhaust passage to be the "second level," which is longer than the first level, if the measured rotational speed obtained in inspection mode falls within the range of the second group, and determines the length level of the external exhaust passage to be the "third level," which is longer than the second level, if the measured rotational speed obtained in inspection mode falls within the range of the third group.

[0068] In this way, the control unit 22A determines whether or not the external exhaust passage is connected to the exhaust passage 5, and if it is determined that it is connected, it estimates the length of the external exhaust passage. Then, when the control unit 22A determines that the external exhaust passage is connected to the exhaust passage 5, it increases the control amount compared to when it is determined that it is not connected, and adjusts the control amount so that the longer the estimated length of the external exhaust passage, the greater the control amount. For example, when it is determined that the external exhaust passage is not connected to the exhaust passage 5, the control amount P calculated in each calculation in both the first feedback calculation and the second feedback calculation is... n The rotational speed of the fan motor 49 is controlled using this. Meanwhile, when the control unit 22A determines that the external exhaust passage is connected to the exhaust passage 5, the control amount P calculated in each calculation in both the first and second feedback calculations is used. n Instead, P x The control variable is used. For example, if the measured control variable is within the range of the first group, then P x =α×P nIf the measured control quantity is within the range of the second group, then P x =β×P n If the measured control quantity is within the range of the third group, then P x =γ×P n The relationship between α, β, and γ is set, for example, 1 < α < β < γ, and the calculated control variable P increases as the level (degree) of length increases. n Correction control amount P to correct to a larger value x Determine this and use it as the above-mentioned controlled variable P n Instead, use this in step S18.

[0069] 5. Examples of effects The water heater 1 can estimate the state of the exhaust passage 5 in a simple manner. In this water heater 1, when the control unit 22A sets the control amount to a predetermined reference control amount, the greater the load of gas flow in the exhaust passage 5, the smaller the rotation speed of the blade section 48A (rotating body), and the smaller the load of gas flow in the exhaust passage 5, the larger the rotation speed of the blade section 48A. Therefore, by estimating based on the rotation speed of the blade section 48A when the control amount is set to a predetermined reference control amount, or based on the control amount when controlling the rotation speed of the blade section 48A to a predetermined reference rotation speed, the state of the exhaust passage 5 can be estimated more accurately in a simple manner.

[0070] The water heater 1 can obtain a useful determination result regarding whether or not the external exhaust passage outside the water heater 1 is connected to the exhaust passage 5, and the determination result can be utilized within the water heater 1.

[0071] Specifically, when the control unit 22A determines that the external exhaust passage is connected to the exhaust passage 5, it increases the control amount during normal combustion compared to when it determines that it is not connected. In the water heater 1, when controlled with the same control amount, the flow load is greater when the external exhaust passage is connected to the exhaust passage 5 than when it is not, so the rotation speed of the blade section 48A decreases. Therefore, by increasing the control amount when it determines that the external exhaust passage is connected to the exhaust passage 5 compared to when it determines that it is not connected, the decrease in rotation speed caused by the external exhaust passage being connected to the exhaust passage 5 can be suppressed.

[0072] More specifically, the control unit 22A estimates the length of the external exhaust passage outside the water heater based on the rotational speed of the blade section 48A when the control amount is set to a predetermined reference control amount, or based on the control amount when the rotational speed of the blade section 48A is controlled to a predetermined reference rotational speed. Thus, the water heater 1 can obtain useful information such as "the length of the external exhaust passage outside the water heater." When the control unit 22A controls using a reference control amount, the longer the external exhaust passage connected to the exhaust passage 5, the greater the load and the lower the rotational speed of the blade section 48A. Alternatively, when controlling the rotational speed of the blade section 48A to a reference rotational speed, the longer the external exhaust passage connected to the exhaust passage 5, the greater the load, and therefore the required control amount increases. The water heater 1 can use this characteristic to obtain useful information such as "the length of the external exhaust passage outside the water heater" in a simpler way.

[0073] When the water heater 1 is controlled with the same control amount, the longer the external exhaust passage connected to the exhaust passage 5, the greater the flow load, and therefore the lower the rotational speed of the blade section 48A. Therefore, if the control is performed so that the control amount increases as the estimated length of the external exhaust passage increases, it is easier to suppress the decrease in rotational speed caused by the external exhaust passage being connected to the exhaust passage 5 more effectively.

[0074] <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.

[0075] The above-described embodiment shows an example of a method for estimating length, but is not limited to the above example. For example, as in the representative example of the above embodiment, in the inspection mode, the control unit 22A controls the above-described control amount P n The fan motor 49 is driven by setting a predetermined reference control amount, and when the fan motor 49 is driven by the reference control amount in this way, the rotational speed (rotational speed of the blade section 48A (rotating body)) detected by the rotational speed sensor 50 is obtained. If the rotational speed detected by the rotational speed sensor 50 (measured rotational speed) is smaller than the rotational speed reference value, the length of the external exhaust passage outside the water heater 1 may be estimated based on the obtained measured rotational speed and a predetermined table or calculation formula. Specifically, a table or calculation formula (specifically, a table or calculation formula that determines the length of the external exhaust passage to be larger the smaller the measured rotational speed) may be used to determine the length value corresponding to the measured rotational speed obtained in inspection mode using the above table or calculation formula. Alternatively, as in another example of the above embodiment, in the inspection mode, the control unit 22A controls the control amount so that the rotational speed of the blade section 48A (rotating body) becomes the above reference rotational speed, and when the control amount is obtained when the rotational speed of the blade section 48A (rotating body) is stable at the above reference rotational speed for a certain period of time, if the obtained control amount (measured control amount) is larger than the control amount reference value, the length of the external exhaust passage outside the water heater 1 may be estimated based on the obtained measured control amount and a predetermined table or calculation formula. Specifically, a table or calculation formula (specifically, a table or calculation formula that determines the value of the external exhaust passage length to be larger the larger the value of the measured control amount) may be used to determine the length value corresponding to the measured control amount obtained in the inspection mode using the above table or calculation formula.

[0076] In the above-described embodiment, an example of a method for calculating the control variable is employed, but the method is not limited to this. As a method for calculating the control variable for controlling the rotational speed of the fan motor 49, for example, other known methods may be employed.

[0077] The method for estimating the length of the external exhaust passage may be, for example, a method based on a table that associates the measured rotational speed with the length of the external exhaust passage, such that the length of the external exhaust passage increases as the measured rotational speed decreases, or a method based on a calculation formula that defines the relationship between the measured rotational speed and the length of the external exhaust passage, such that the length of the external exhaust passage increases as the measured rotational speed decreases.

[0078] 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]

[0079] 1: Water heater 4: Gas burner section (burner) 4Z: Case (container) 5: Exhaust passage 5A: Exhaust port 6: Hot water side heat exchanger (heat exchanger) 6Z: Case 7a: Heat transfer tube 8a: Heat transfer tube 10: Hot water outlet pipe (water pipe) 12: Water inlet pipe (water pipe) 22A: Control Unit 22B: Memory 22C:Communication Department 48: Fan 48A: Blade section (rotating body) 49: Fan motor (motor) 50: Rotation speed sensor 54: Gas burner (burner) 56: Bath-side heat exchanger (heat exchanger)

Claims

1. A burner that burns gas, A housing for the aforementioned burner, A heat exchanger comprising a heat transfer tube heated by the exhaust gas generated within the aforementioned containment, An exhaust passage that forms a path for discharging the exhaust gas that has passed through the heat exchanger, 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 fan comprising a rotating body and a motor that rotates the rotating body, which supplies air into the housing by the rotation of the rotating body, A control unit for adjusting the control amount for controlling the motor, Equipped with, The motor drives the rotating body to rotate such that it increases the rotational speed of the rotating body when the control amount set in the control unit increases, and decreases the rotational speed of the rotating body when the control amount decreases. The control unit estimates the state of the exhaust passage based on the rotational speed of the rotating body when the control amount is set to a predetermined reference control amount, or based on the control amount when the rotational speed of the rotating body is controlled to a predetermined reference rotational speed. Water heater.

2. The control unit determines whether an external exhaust passage outside the water heater is connected to the exhaust passage based on the rotational speed of the rotating body when the control amount is set to a predetermined reference control amount, or based on the control amount when the rotational speed of the rotating body is controlled to a predetermined reference rotational speed. The water heater according to claim 1.

3. If the control unit determines that the external exhaust passage is connected to the exhaust passage, it increases the control amount compared to when it determines that it is not connected. The water heater according to claim 2.

4. The control unit estimates the length of the external exhaust passage outside the water heater based on the rotational speed of the rotating body when the control amount is set to a predetermined reference control amount, or based on the control amount when the rotational speed of the rotating body is controlled to a predetermined reference rotational speed. The water heater according to claim 1.

5. The control unit increases the control amount as the estimated length of the external exhaust passage increases. The water heater according to claim 4.

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