JP2019109009A - Water heating device - Google Patents

Abstract

To provide a water heating device capable of appropriately preventing freezing of a primary heat exchanger and a secondary heat exchanger.SOLUTION: A water heating device 10 comprises: a combustor 103; a can body 102 housing the combustor 103; a fan 114 supplying air into the can body 102; a temperature sensor 133 provided with an exhaust passage R1 for exhausting an exhaust gas from the can body 102; a primary heat exchanger 104 transferring heat from the combustor 103 housed in the can body 102 to water for hot water supply; a secondary heat exchanger 105 transferring heat from the combustor 103 provided in the exhaust passage R1 side with respect to the primary heat exchanger 104 to water for hot water supply; and a control unit 121 starting driving of the fan 114 on the basis of a detection temperature of the temperature sensor 133 decreasing to a first threshold value or lower during a non-combustion operation and then intermittently driving the fan 114 till the detection temperature reaches a second threshold value higher than the first threshold value.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a combustion-heated water heater, and is particularly suitable for use in a water heater installed indoors.

  In the water heater installed indoors, the exhaust gas generated in the water heater main body is discharged to the outside by the exhaust pipe. One end of the exhaust stack is connected to the water heater main body, and the other end of the exhaust stack is pulled out outdoors. In this configuration, since the water heater main body is installed indoors, the temperature inside the water heater main body is unlikely to be excessively low during non-combustion operation. For this reason, it becomes difficult to produce freezing in the member accommodated in the water heater main body.

  However, even in this type of water heater, outdoor cold air may flow into the water heater body through the exhaust stack. In this case, the flow of cold air lowers the temperature inside the water heater main body. Thereby, freezing may occur in the member accommodated in the water heater main body.

  In order to avoid such a problem, in this type of water heater, control is performed to feed the air in the water heater body to the exhaust stack during non-combustion operation. For example, when a temperature sensor provided in the exhaust passage detects a temperature at which freezing may occur, air in the water heater main body is fed to the exhaust stack by the fan. This prevents outdoor cold air from flowing into the water heater body from the exhaust stack.

  In addition to this, it is described in the following Patent Document 1 that air inside the apparatus main body is fed to the exhaust stack by the fan when it is detected that the outside air flows backward from the exhaust stack.

Japanese Patent Application Laid-Open No. 10-47655

  However, in the configuration in which the fan is operated based on the detected temperature of the exhaust path as described above, after operating the fan, if the detected temperature of the exhaust path does not rise for a long time, the fan continues to operate. become. In this case, the heat exchanger in the water heater main body continues to be supplied with air for a long period of time, and conversely, there is a possibility that the heat exchanger may be frozen due to excessive supply of air.

  In particular, in the case where the hot water supply apparatus includes the primary heat exchanger and the secondary heat exchanger, there is a possibility that the primary heat exchanger on the combustor side may freeze due to the state of excessive air supply as described above. If control is performed to stop the fan after a predetermined time has elapsed in order to prevent this, there is a possibility that freezing may occur in the secondary heat exchanger on the exhaust path side due to cold air from the exhaust stack.

  In view of such a subject, an object of the present invention is to provide a hot-water supply apparatus which can prevent freezing of a primary heat exchanger and a secondary heat exchanger appropriately.

  A hot water supply apparatus according to a main aspect of the present invention comprises a combustor, a can containing the combustor, a fan for supplying air into the can, and an exhaust passage for exhausting exhaust gas from the can. The temperature sensor provided, the primary heat exchanger housed in the can and transferring the heat from the combustor to the water for hot water supply, and the primary heat exchanger provided on the exhaust path side with respect to the primary heat exchanger The secondary heat exchanger for transferring the heat from the combustor to the water for hot water supply and the driving of the fan based on the fact that the detected temperature falls below the first threshold during non-combustion operation, and thereafter, And a controller configured to intermittently drive the fan until the detected temperature reaches a second threshold higher than the first threshold.

  According to the water heater according to the present aspect, the driving of the fan is started based on the temperature detected by the temperature sensor falling below the first threshold during non-combustion operation, and cold air from the outside flows into the can from the exhaust passage. Is deterred. Therefore, it is possible to prevent the secondary heat exchanger closer to the exhaust passage from freezing due to cold air outside. Furthermore, since the fan is intermittently driven until the temperature detected by the temperature sensor reaches the second threshold thereafter, excessive supply of air to the primary heat exchanger closer to the fan is suppressed. . Thus, it is possible to prevent the primary heat exchanger from freezing due to excessive supply of air. As described above, according to the water heater of the present aspect, it is possible to appropriately prevent freezing of the primary heat exchanger and the secondary heat exchanger.

  In the above configuration, “transfer the heat from the combustor to the water for hot water supply” means that the heat of the combustion gas generated in the process of the combustion gas generated in the combustor advances toward the exhaust passage, In the primary heat exchanger and the secondary heat exchanger, it means to be transferred to the water for hot water supply.

  In the water heating apparatus according to the present aspect, the control unit drives the fan for a first time in the intermittent drive of the fan, and then stops the fan, and thereafter, the detected temperature before a second time elapses. May be configured to repeat a cycle of driving the fan at the first time based on the fact that the second threshold is not reached.

  As described above, the intermittent drive of the fan can be smoothly controlled by switching the fan on and off based on the passage of two times.

  In this configuration, the control unit compares, after the second time has elapsed, a third threshold set between the first threshold and the second threshold with the detected temperature, and the detected temperature When the temperature is equal to or higher than the third threshold value, it may be configured to shift to control to drive the fan in the first time in response to the detected temperature becoming lower than the third threshold value.

  According to this configuration, the drive of the next fan is on standby until the detected temperature falls below the third threshold, so the timing at which the detected temperature reaches the second threshold due to the intermittent drive of the fan is delayed. That is, in this configuration, the intermittent drive of the fan is repeated while the detected temperature transitions between the second threshold and the third threshold. For this reason, even if there is a difference between the temperature detected by the temperature sensor and the actual temperature of the secondary heat exchanger due to the difference in thermal conductivity between the secondary heat exchanger and the temperature sensor, the fan may be interrupted. By repeating the driving, the difference between the temperature detected by the temperature sensor and the actual temperature of the secondary heat exchanger is suppressed, and both temperatures come closer. Thus, intermittent drive of the fan can be ended at the timing when the actual temperature of the secondary heat exchanger approximately reaches the second threshold. Therefore, it is possible to prevent freezing of the secondary heat exchanger more appropriately.

  The water heating apparatus according to this aspect may be configured to include a heater that heats the primary heat exchanger and the secondary heat exchanger, respectively. In this case, the control unit may be configured to operate the heater in parallel with the intermittent driving of the fan.

  According to this configuration, freezing of the primary heat exchanger and the secondary heat exchanger can be more effectively prevented by the heating by the heater. In addition, since air around the primary heat exchanger heated by the heater is sent to the secondary heat exchanger when the fan is driven, freezing of the secondary heat exchanger that is more easily exposed to the air can be obtained. It can prevent more effectively.

  In the water heater according to this aspect, the primary heat exchanger may be a sensible heat recovery type heat exchanger, and the secondary heat exchanger may be a latent heat recovery type heat exchanger.

  As described above, according to the present invention, it is possible to provide a water heater capable of appropriately preventing freezing of the primary heat exchanger and the secondary heat exchanger.

  The effects and significances of the present invention will become more apparent from the description of the embodiments shown below. However, the embodiment shown below is merely an example when implementing the present invention, and the present invention is not limited to the one described in the following embodiment.

FIG. 1 is a view showing a configuration of a hot water supply apparatus according to the embodiment. FIG. 2 is a flowchart showing control of the fan according to the embodiment. FIG. 3 is a flowchart showing control of the heater according to the embodiment. FIG. 4 is a graph schematically showing the relationship between the control of the fan according to the embodiment and the change in temperature detected by the temperature sensor. FIG. 5 is a flowchart showing control of the fan according to the modification. FIG. 6 is a graph schematically showing the relationship between the control of the fan according to the modification and the change in the detected temperature of the temperature sensor.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings. In the present embodiment, the present invention is applied to a gas-type water heater.

  FIG. 1 is a diagram showing the configuration of the hot water supply apparatus 10. As shown in FIG.

  As shown in FIG. 1, the water heater 10 includes a water heater 100 and a remote controller 200. Water heater 100 and remote controller 200 are installed indoors. Exhaust gas generated by the water heater 100 is exhausted to the outside by an exhaust pipe not shown. That is, the water heating apparatus 10 according to the present embodiment is an indoor installation type water heating apparatus.

  The water heater 100 includes an outer case 101. The outer shell of the water heater 100 is configured by the exterior case 101. The exterior case 101 is provided with an air inlet 101a for introducing outside air. The intake port 101a may be communicated with the outside by a feed cylinder (not shown) or may be communicated indoors. When the fan 114 is driven, the inside of the outer case 101 becomes negative pressure, so air is introduced into the outer case 101 through the intake passage R2.

  The can body 102 is disposed inside the exterior case 101. In the can 102, a combustor 103, a primary heat exchanger 104, and a secondary heat exchanger 105 are accommodated. The fuel gas is supplied to the combustor 103 by a pipe 106. The pipe 106 is provided with a solenoid valve 107 for opening and closing the pipe 106 and a proportional valve 108 for adjusting the amount of supplied fuel gas. The solenoid valve 107 and the proportional valve 108 are controlled by the control unit 121 of the circuit board 120.

  A pipe 109 is connected to the primary heat exchanger 104 and the secondary heat exchanger 105. Water is supplied to the inlet of the pipe 109, and hot water is released from the outlet of the pipe 109. While the water flowing through the pipe 109 passes through the flow paths of the primary heat exchanger 104 and the secondary heat exchanger 105, the heat generated in the combustor 103 is transmitted through the primary heat exchanger 104 and the secondary heat exchanger 105. Is transmitted to the water. This will warm the water.

  The primary heat exchanger 104 is a sensible heat recovery type heat exchanger, and the secondary heat exchanger 105 is a latent heat recovery type heat exchanger. The flow passage portion of the primary heat exchanger 104 is made of copper, and the flow passage portion of the secondary heat exchanger 105 is made of stainless steel (SUS: Steel Use Stainless). The secondary heat exchanger 105 is provided on the exhaust passage R1 side with respect to the primary heat exchanger 104. The water flowing through the pipe 109 is warmed as it passes through the secondary heat exchanger 105 and further warmed as it passes through the primary heat exchanger 104.

  The piping 109 is provided with a hot water discharge valve 110 for adjusting the discharge amount of hot water, that is, the hot water supply amount. The outlet valve 110 is driven by a stepping motor. The stepping motor is controlled by the control unit 121 of the circuit board 120.

  Further, the inlet side and the outlet side of the pipe 109 are bypassed by the pipe 111. A bypass valve 112 is provided in the pipe 111. Further, the pipe 111 is connected to the pipe 109 by the mixer 113. Thereby, the water from the pipe 111 is mixed in the hot water directed to the outlet of the pipe 109. Thus, the temperature of the hot water discharged from the outlet of the pipe 109 is adjusted. The bypass valve 112 is for adjusting the mixing amount of water. The bypass valve 112 is driven by a stepping motor. The stepping motor is controlled by the control unit 121 of the circuit board 120.

  A fan 114 is connected to the air supply port 102 a of the can body 102. Further, the exhaust port 102 b of the can 102 is connected to an exhaust cylinder (not shown) through a hole formed on the side surface of the exterior case 101 and is communicated with the outside. The fan 114 is, for example, a single phase fan. The fan 114 may be a sirocco fan. The fan 114 supplies combustion air to the combustor 103 by driving the motor 114 a. Motor 114a is, for example, a brushless DC motor. The fan 114 is controlled by the control unit 121 to have a predetermined number of revolutions so that air is supplied to the combustor 103 at a predetermined air fuel ratio.

  The water heater 100 further includes a circuit board 120, heaters 131 and 132, and a temperature sensor 133. In addition to the control unit 121, a circuit unit for driving the water heater 100 is mounted on the circuit board 120.

  The control unit 121 includes, for example, a microcomputer and a memory storing a control program of the microcomputer. The memory includes a random access memory (RAM), a read only memory (ROM), and the like. The memory is also used as a work area of the microcomputer.

  The heater 131 is installed to heat the primary heat exchanger 104, and the heater 132 is installed to heat the secondary heat exchanger 105. The heaters 131 and 132 are provided for preventing freezing, and are, for example, electrically heated heaters. The temperature sensor 133 is, for example, a thermistor, and is installed in the exhaust passage R1 connected from the can 102 to the exhaust cylinder.

  In the water heater 100, various heaters may be further provided in the outer case 101. For example, a heater for preventing freezing of the water inlet and the hot water supply port and the pipe 111 for bypass may be provided at these portions. In addition to the temperature sensor 133, various sensors are disposed in the water heater 100. For example, a temperature sensor for detecting the temperature of water input from the water inlet and the temperature of hot water flowing out from the hot water supply port, a sensor for detecting the flow rate of water flowing through the pipe 109, and the like are arranged.

  The remote controller 200 is installed, for example, in a kitchen, a living room, etc., and is used for setting a hot water supply temperature and displaying various information. In the remote controller 200, along with various operation buttons and a display unit, an operation switch for setting the hot water supply device 10 in an operation state is disposed.

  By the way, in the water heating apparatus 10 of the above configuration, when the temperature detected by the temperature sensor 133 falls below the predetermined threshold during non-combustion operation, the fan 114 is driven to feed the air in the can 102 into the exhaust passage R1. Control can be made. As a result, cold air from the outside is prevented from flowing from the exhaust stack into the interior of the can 102, and freezing of the secondary heat exchanger 105 on the exhaust passage R1 side is prevented.

  However, after operating the fan 114 in this manner, if the detected temperature of the exhaust passage R1 has not risen over a long period of time, the fan 114 will continue to operate. In this case, air continues to be supplied to the primary heat exchanger 104 in the can 102 for a long time, and conversely, there is a possibility that the primary heat exchanger 104 may be frozen due to excessive supply of air. In addition, if control is performed to stop the fan 114 with the elapse of a predetermined time in order to prevent this, there is a possibility that freezing may occur in the secondary heat exchanger 105 on the exhaust passage R1 side due to the inflow of cold air from the exhaust passage R1. is there.

  In view of such a problem, in the present embodiment, control for appropriately preventing freezing of the primary heat exchanger 104 and the secondary heat exchanger 105 is performed. Hereinafter, this control will be described.

  First, control of the fan 114 will be described with reference to FIG. The control of FIG. 2 is performed in a period (non-combustion period) in which the water heating apparatus 10 stops the combustion operation.

  First, the control unit 121 determines whether the operation of the fan 114 is permitted (S101). For example, the control unit 121 determines that the operation of the fan 114 is permitted when all of the following conditions are satisfied.

・ The hot water supply device 10 is in the combustion prohibited state ・ The temperature sensor 133 is operating normally ・ The fan 114 is operating normally

  Here, the "burn-free state" is, for example, a state in which at least one of the following conditions is satisfied.

The operation switch of the remote controller 200 is in the off state (the water heater 10 is in the operation off state)
・ Hot water supply device 10 in safety stop mode with error in hot water supply device 10 (safe stop mode) ・ The operation switch is on, but the flow rate of water flowing out from the hot water supply port is less than the threshold of combustion operation (If the tip plug is not open or the amount of opening is small)
・ The combustion operation is prohibited because the temperature of the water flowing in from the water inlet is higher than the specified temperature ・ When the combustion operation is performed in the minimum combustion state, the temperature exceeding the specified set temperature The condition for hot water supply was established

  If the control unit 121 determines that the fan 114 is in the operation permitted state based on the above conditions (S101: YES), then it determines whether the detected temperature Td of the temperature sensor 133 is equal to or less than the first threshold Tth1. (S102). The first threshold Tth1 is set to, for example, about 4 ° C. If the detected temperature Td is not equal to or lower than the first threshold Tth1 (S102: NO), the control unit 121 returns the process to step S101 and repeats the processes of steps S101 and S102.

  On the other hand, when the detected temperature Td of the temperature sensor 133 is less than or equal to the first threshold Tth1 (S102: YES), the control unit 121 starts the operation of the fan 114 (S103). At this time, the control unit 121 determines whether the operation of the fan 114 is normal (S104). If the operation of the fan 114 is not normal (S104: NO), the operation of the fan 114 is stopped (S104). S105), the process returns to step S101. In this case, the control unit 121 causes the display unit of the remote controller 200 to display a predetermined error message.

  If the operation of the fan 114 is normal (S104: YES), the control unit 121 determines whether the time TM1 has elapsed since the fan 114 was activated (S106). The time TM1 is set to, for example, about 30 seconds. When the time TM1 has elapsed (S106: YES), the control unit 121 stops the operation of the fan 114 (S107), and waits for the time TM2 to elapse (S108). Meanwhile, the control unit 121 determines whether the detected temperature Td of the temperature sensor 133 is equal to or higher than the second threshold Tth2 (S109). The time TM2 is set to, for example, about 30 seconds. In addition, the second threshold Tth2 is set to, for example, about 9 ° C.

  While the detected temperature Td reaches the second threshold Tth2 or more (S109: YES) until the time TM2 elapses (S108: NO), the control unit 121 returns the process to step S101 and proceeds to step S101 and subsequent steps. Repeat the process. On the other hand, when the detected temperature Td does not reach the second threshold Tth2 or more (S109: NO) and the time TM2 elapses (S108: YES), the control unit 121 next detects the temperature Td detected by the temperature sensor 133 It is judged whether it is less than 3 threshold value Tth3 (S110). The third threshold Tth3 is set to, for example, about 7 ° C.

  In a period in which the detected temperature Td is equal to or higher than the third threshold Tth3 (S110: NO), the control unit 121 determines again whether the detected temperature Td is equal to or higher than the second threshold Tth2 (S109). If the determination in step S109 is NO, since the time TM2 has already elapsed, the determination in step S108 is uniformly YES, and the process proceeds to step S110.

  Here, the determination in step S109 is already performed in a period in which the determination in step S108 is NO before the process proceeds from step S108 to step S110. However, even if the detected temperature Td does not become equal to or higher than the second threshold Tth2 in a period in which the determination in step S108 is NO, that is, in a period from when the fan 114 is stopped to time TM2 elapses (S109 NO :) It may happen that the detected temperature Td of the temperature sensor 133 rises above the second threshold Tth2 due to the subsequent change of the temperature environment around the water heater 100 or the like. In such a case, the determination in step S109 is YES. In this case, the control unit 121 returns the process to step S101 and repeats the processes after step S101.

  If the detected temperature Td of the temperature sensor 133 falls below the third threshold Tth3 (S109: NO) and not below the third threshold Tth2 (S110: YES), the control unit 121 returns the process to step S103. , Again, drive the fan 114. After that, the control unit 121 executes the processing after step S104 again. Thus, the intermittent driving of the fan 114 is repeatedly performed at time TM1 and time TM2 until the detected temperature Td of the temperature sensor 133 becomes equal to or higher than the second threshold Tth2.

  Next, control of the heaters 131 and 132 will be described with reference to FIG. The control of FIG. 3 is performed in a period (non-combustion period) in which the hot water supply device 10 stops the combustion operation.

  First, the control unit 121 determines whether the detected temperature Td of the temperature sensor 133 is equal to or lower than the threshold Tth11 (S201). The threshold Tth11 is set to, for example, about 4 ° C. When the detected temperature Td becomes equal to or lower than the threshold Tth11 (S201: YES), the control unit 121 drives the heaters 131 and 132 (S202), and waits for the time TM11 to elapse (S203). Accordingly, at time TM11, the primary heat exchanger 104 and the secondary heat exchanger 105 are heated by the heaters 131 and 132. Time TM11 is set to, for example, about 20 to 30 minutes.

  Thus, when the time TM11 has elapsed (S203: YES), the control unit 121 determines whether the detected temperature Td of the temperature sensor 133 is equal to or higher than the threshold Tth12 (S204). If the detected temperature Td is equal to or higher than the threshold Tth12 (S204: YES), the control unit 121 stops the heaters 131 and 132 (S205), and returns the process to step S201.

  On the other hand, if the detected temperature Td is not equal to or higher than the threshold Tth12 (S204: NO), the controller 121 resets the timer (S206), returns the process to step S203, and waits for the time TM11 to elapse again. Thus, at time TM11, the primary heat exchanger 104 and the secondary heat exchanger 105 are heated by the heaters 131 and 132, respectively. The control unit 121 continues driving the heaters 131 and 132 in units of time TM11 until the detected temperature Td of the temperature sensor 133 becomes equal to or higher than the threshold Tth12.

  FIG. 4 is a graph schematically showing the relationship between the control of the fan 114 and the change in the detected temperature Td of the temperature sensor 133. As shown in FIG. Note that the change in the detected temperature Td shown in FIG. 4 is an example, and the detected temperature Td changes in a state other than FIG. 4 depending on the environmental temperature around the water heater 100, the inflow of external air to the exhaust stack, etc. Can also happen.

  When the detected temperature Td becomes equal to or lower than the first threshold Tth1 at time T1, the control unit 121 activates the fan 114 to send the air in the can 102 to the exhaust passage R1. At the same time, the control unit 121 activates the heaters 131 and 132 to heat the primary heat exchanger 104 and the secondary heat exchanger 105. Thus, the air in the can 102 is supplied to the exhaust passage R1, and the detected temperature Td of the temperature sensor 133 gradually rises.

  Thereafter, the fan 114 is stopped at time T2 when time TM1 has elapsed. With the stop of the fan 114, the supply of air in the can 102 to the exhaust passage R1 is stopped. As a result, the temperature of the exhaust passage R1, that is, the detected temperature Td of the temperature sensor 133 gradually decreases. The fan 114 is kept stopped until the time TM2 elapses. The heaters 131 and 132 continue to be driven even after time T2.

  Thereafter, at time T3 when time TM2 has elapsed, the control unit 121 activates the fan 114 again to send the air in the can 102 to the exhaust passage R1. Thus, the detected temperature Td of the temperature sensor 133 gradually rises. Thereafter, the fan 114 is stopped at time T4 when the time TM1 has elapsed, and the fan 114 is activated at time T5 when the time TM2 has elapsed. Thus, as the on / off of the fan 114 is repeated, the detected temperature Td of the temperature sensor 133 relatively rises.

  Then, when the fan 114 is stopped at time T6, the detected temperature Td of the temperature sensor 133 exceeds the third threshold Tth3 at time T7 when time TM2 has elapsed. In this case, the control unit 121 postpones the activation of the fan 114 until the detected temperature Td becomes lower than the third threshold Tth3 by the process of step S110 of FIG. 2. In the example of FIG. 4, activation of the fan 114 is postponed for a time ΔT1. Then, the control unit 121 restarts the fan 114 at time T8 when the time ΔT1 has elapsed from time T7.

  Thereafter, the control unit 121 drives the fan 114 in a period from time T8 to time T9, and stops the fan 114 in a period from time T9 to time T10. Also in this case, since the detected temperature Td of the temperature sensor 133 exceeds the third threshold Tth3 at time T10, the control unit 121 subsequently controls the fan 114 until the detected temperature Td falls below the third threshold Tth3. Defer the launch of Here, the activation of the fan 114 is postponed by the time ΔT2.

  Thus, in the control of FIG. 2, the start of the next fan 114 is delayed until the detected temperature Td falls below the third threshold Tth3. For this reason, even if the fan 114 is driven after the postponement, the temperature Td detected by the temperature sensor 133 hardly rises to the second threshold Tth2 or more. As a result, the fan 114 is repeatedly turned on and off while the detected temperature Td changes in the range between the second threshold Tth2 and the third threshold Tth3.

  In the example of FIG. 4, such on / off repetition of the fan 114 is performed only once in the period from time T8 to time T11, but usually such repetition of on / off is After repeated several times, the detected temperature Td of the temperature sensor 133 reaches the second threshold Tth2 due to factors such as an increase in environmental temperature and heat accumulation in the primary heat exchanger 104 and the secondary heat exchanger 105. You will come to

  Thus, when the detected temperature Td reaches the second threshold Tth2 at time T12, the determination in step S109 of FIG. 2 becomes YES, and the control unit 121 ends the intermittent drive of the fan 114. Thus, the detected temperature Td gradually decreases with the passage of time. Then, when the detected temperature Td becomes less than or equal to the first threshold Tth1, the control unit 121 starts the intermittent driving of the fan 114 again in order to prevent the primary heat exchanger 104 and the secondary heat exchanger 105 from freezing. .

<Effect of the embodiment>
According to the present embodiment, the following effects can be achieved.

  Driving of the fan 114 is started based on the temperature Td detected by the temperature sensor 133 falling to or below the first threshold Tth1 during non-combustion operation, and outdoor cold air is prevented from flowing into the can 102 from the exhaust passage R1. Be done. Therefore, it is possible to prevent the secondary heat exchanger 105 closer to the exhaust passage R1 from freezing due to cold air outside. Also, thereafter, since the fan 114 is intermittently driven until the detected temperature Td of the temperature sensor 133 reaches the second threshold Tth2, excessive supply of air to the primary heat exchanger 104 closer to the fan 114 becomes excessive. Being suppressed. Thus, it is possible to prevent the primary heat exchanger 104 from freezing due to excessive supply of air. Thus, according to the hot water supply apparatus 10 which concerns on this aspect, freezing of the primary heat exchanger 104 and the secondary heat exchanger 105 can be prevented appropriately.

  As shown in FIG. 2, in the intermittent drive of the fan 114, the control unit 121 drives the fan 114 for time TM1 (first time), and then stops the fan 114, and then for time TM2 (second time). Based on the fact that the detected temperature Td does not reach the second threshold Tth2 until the elapse of, the cycle of driving the fan 114 is repeated at time TM1 (first time). As described above, the intermittent drive of the fan 114 can be smoothly controlled by switching the fan 114 on and off based on the passage of two times.

  Further, in step S110 of FIG. 2, after the time TM2 (second time) has elapsed, the control unit 121 sets a third threshold Tth3 set between the first threshold Tth1 and the second threshold Tth2 and the detection temperature Td. And the step of driving the fan 114 at time TM1 (first time) in response to the detected temperature Td becoming lower than the third threshold Tth3 if the detected temperature Td is higher than the third threshold Tth3. Transfer the process to

  By this control, as described with reference to FIG. 4, the intermittent drive of the fan 114 is repeated while the detected temperature Td transits between the second threshold Tth2 and the third threshold Tth3. Therefore, when there is a difference between the temperature Td detected by the temperature sensor 133 and the actual temperature of the secondary heat exchanger 105 due to the difference in thermal conductivity between the secondary heat exchanger 105 and the temperature sensor 133 Also, by repeating the intermittent driving of the fan 114, the difference between the temperature Td detected by the temperature sensor 133 and the actual temperature of the secondary heat exchanger 105 is suppressed, and both temperatures come closer. Thus, the intermittent drive of the fan 114 can be ended at the timing when the actual temperature of the secondary heat exchanger 105 substantially reaches the second threshold Tth2. Therefore, freezing of the secondary heat exchanger 105 can be prevented more appropriately.

  Furthermore, as shown in FIG. 1, heaters 131 and 132 for respectively heating the primary heat exchanger 104 and the secondary heat exchanger 105 are provided, and the control unit 121 is operated in parallel with the intermittent driving of the fan 114. , The heaters 131 and 132 are operated. Thereby, freezing of the primary heat exchanger 104 and the secondary heat exchanger 105 can be prevented more effectively. In addition, when the fan 114 is driven, the air around the primary heat exchanger 104 heated by the heater 131 is sent to the secondary heat exchanger 105, so the secondary heat exchanger is more likely to be exposed to the outside air. Freezing of 105 can be prevented more effectively.

<Modification example>
The water heater according to the present invention is not limited to the configuration of the above embodiment, and various modifications are possible.

  For example, in the above embodiment, in consideration of the difference between the thermal conductivity of the secondary heat exchanger 105 and the thermal conductivity of the temperature sensor 133, step S110 is included in the control flowchart of FIG. If the difference between the thermal conductivity of the exchanger 105 and the thermal conductivity of the temperature sensor 133 is small, step S110 may be omitted from the control flow chart of the fan 114, as shown in FIG.

  In this case, the relationship between the control of the fan 114 and the change in the detected temperature Td of the temperature sensor 133 is, for example, as shown in the graph of FIG. Here, although the detected temperature Td becomes higher than the third threshold Tth3 at time T17, the control unit 121 immediately waits for the fan 114 at time T17 without waiting for the detected temperature Td to be less than the third threshold Tth3. Start up As a result, at time T18 at which time TM1 elapses and fan 114 is stopped, detected temperature Td becomes equal to or higher than second threshold Tth2, and intermittent driving of fan 114 is ended.

  According to this modification, the cycle of intermittent drive of the fan 114 can be reduced compared to the above embodiment.

  However, when the difference between the thermal conductivity of the secondary heat exchanger 105 and the thermal conductivity of the temperature sensor 133 is large, the temperature of the secondary heat exchanger 105 is larger than that of the temperature Td detected by the temperature sensor 133 at time T18. It may happen that the actual temperature goes down. Then, due to this temperature difference, although the detected temperature Td is the first threshold Tth1 at time T19, it may occur that the actual temperature of the secondary heat exchanger 105 has dropped to a temperature equal to or lower than the temperature at which freezing occurs. .

  Therefore, when the difference between the thermal conductivity of the secondary heat exchanger 105 and the thermal conductivity of the temperature sensor 133 is large, as in the above embodiment, step S110 is added to the control flowchart of the fan 114 to detect the detected temperature. It is preferable that the fan 114 performs control to repeat intermittent driving while causing Td to transition between the second threshold Tth2 and the third threshold Tth3. Thereby, as described above, the detection temperature Td becomes equal to or higher than the second threshold Tth2 in a state where the difference between the actual temperature of the secondary heat exchanger 105 and the detection temperature Td is substantially eliminated, and the intermittent drive of the fan 114 is performed. Will be terminated. As a result, at the timing when the intermittent drive of the fan 114 is started next, the secondary heat exchanger 105 can be prevented from falling below the temperature at which freezing occurs, and the secondary heat exchanger 105 is frozen. Can be prevented more reliably.

  Further, in the above embodiment, 4 ° C., 9 ° C. and 7 ° C. are shown as an example of the first threshold Tth1, the second threshold Tth2 and the third threshold Tth3, respectively, but the temperatures of these thresholds are limited to this. However, as long as the first threshold Tth1 is the lowest and the second threshold Tth2 is the highest, the relationship can be changed as appropriate. However, the first threshold Tth1 needs to be set to a temperature that can prevent the secondary heat exchanger 105 from freezing, and the second threshold Tth2 needs to be set to a temperature that can be reached by intermittent driving of the fan 114.

  Moreover, in the said embodiment, although 30 second was shown as an example of time TM1 and TM2, respectively, these times are not restricted to this. Also, the times TM1 and TM2 may not necessarily be the same, for example, the time TM1 may be longer than the time TM2, or the time TM2 may be longer than the time TM1. Also, the times TM1 and TM2 may be changed every cycle of intermittent driving of the fan 114, or the times TM1 and TM2 are changed according to the cycle of intermittent driving of the fan 114 being performed a predetermined number of times. May be Further, the intermittent drive of the fan 114 may be performed by a method other than the above embodiment, and the step of terminating the intermittent drive based on the detection temperature Td reaching the second threshold Tth2 while the fan 114 is driven. May be added.

  The threshold values Tth11 and Tth12 for starting and stopping the heaters 131 and 132 shown in FIG. 3 are not limited to the above, and can be changed as appropriate. The time TM11 for driving the heaters 131 and 132 can also be changed as appropriate. is there. Furthermore, the heaters 131 and 132 do not necessarily have to perform the same control. For example, the threshold values Tth11 and Tth12 or controls with different times TM11 may be separately performed on the heaters 131 and 132.

  Further, the configuration of water heater 100 is not limited to the configuration shown in FIG. 1, and can be changed as appropriate. Furthermore, although the hot-water supply apparatus 10 which can only perform hot-water supply was illustrated in the said embodiment, this invention may be applied to the hot-water supply apparatus 10 which can repel a bath with hot-water supply. The present invention may be applied to a hot water supply apparatus capable of hot water heating as well as hot water supply. In addition, the present invention may be applied to water heating apparatuses of other types such as oil type, not limited to gas type.

  Besides the above, the embodiment of the present invention can be variously modified as appropriate within the scope of the claims.

DESCRIPTION OF SYMBOLS 10 Water heater 100 Water heater 102 Can 103 103 Combustator 104 Primary heat exchanger 105 Secondary heat exchanger 114 Fan 121 Control part 131, 132 Heater 133 Temperature sensor R1 Exhaust passage

Claims (5)

A combustor,
A can containing the combustor;
A fan for supplying air into the can;
A temperature sensor provided in an exhaust passage for exhausting exhaust gas from the can body;
A primary heat exchanger housed in the can and transferring heat from the combustor to water for hot water supply;
A secondary heat exchanger provided on the exhaust passage side with respect to the primary heat exchanger, for transferring heat from the combustor to the water for hot water supply;
Driving of the fan is started based on the detected temperature falling below the first threshold during non-combustion operation, and then the fan continues until the detected temperature reaches a second threshold higher than the first threshold. And a controller for intermittently driving the
A hot water supply device characterized by In the hot water supply apparatus according to claim 1,
The control unit causes the fan to stop after driving the fan for a first time in the intermittent drive of the fan, and thereafter the detected temperature does not reach the second threshold before a second time elapses. Repeat the cycle of driving the fan again at the first time based on
A hot water supply device characterized by In the water heater according to claim 1 or 2,
The control unit compares the detected temperature with a third threshold set between the first threshold and the second threshold after the second time has elapsed, and the detected temperature is the third threshold. In the case of the above, in accordance with the fact that the detected temperature has become less than the third threshold, the control shifts to control to drive the fan in the first time,
A hot water supply device characterized by The water heater according to any one of claims 1 to 3.
A heater for heating the primary heat exchanger and the secondary heat exchanger,
The control unit operates the heater in parallel with intermittent driving of the fan.
A hot water supply device characterized by The water heater according to any one of claims 1 to 4.
The primary heat exchanger is a sensible heat recovery type heat exchanger,
The secondary heat exchanger is a latent heat recovery type heat exchanger,
A hot water supply device characterized by

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