JP7616952B2 - Water heater - Google Patents

Description

The technology disclosed in this specification relates to water heaters.

Patent document 1 discloses a first water heater connected to a circulation circuit that does not have a crossover valve, and a second water heater connected to a circulation circuit that has a crossover valve.

JP 2020-139633 A

The first water heater and the second water heater each have their own appropriate controls. If the first water heater executes control suitable for the second water heater (i.e., if control inappropriate for the first water heater is executed), abnormal operation may occur in the first water heater. This specification provides technology that can provide an opportunity to correct the execution of inappropriate control.

The water heater disclosed in this specification includes a heating section that heats water, a first water supply pipe that is connected to the heating section and supplies water to the heating section, and a first hot water supply pipe that is connected to the heating section and supplies the water heated by the heating section. The water heater is connected to a path that includes a second water supply pipe that extends from a water supply source to the upstream end of the first water supply pipe, a second hot water supply pipe that extends from the downstream end of the first hot water supply pipe to a hot water supply location, a hot water supply valve that opens and closes the second hot water supply pipe, and a return pipe that is connected to the second hot water supply pipe and the second water supply pipe upstream of the hot water supply valve and returns water from the second hot water supply pipe to the second water supply pipe. A circulation path in which water circulates is formed by the first water supply pipe, the first hot water supply pipe, the second hot water supply pipe, the return pipe, and the second water supply pipe. The water heater includes a circulation pump provided in the circulation path and circulating water in the circulation path, a flow rate sensor detecting a flow rate of water flowing through the first water supply pipe, and a control unit controlling operation of the circulation pump based on a control program. The control program is set to cause the control unit to execute a first control for stopping the circulation pump when a predetermined first reference time has elapsed since the start of the circulation pump or when a flow rate detected by the flow rate sensor becomes less than a predetermined first reference flow rate during operation of the circulation pump, and starting the circulation pump when a predetermined second reference time has elapsed since the stop of the circulation pump, and a second control for stopping the circulation pump when a flow rate detected by the flow rate sensor becomes equal to or greater than a predetermined second reference flow rate that is equal to or greater than the first reference flow rate due to operation of the circulation pump, and for determining that the hot water tap is closed and starting the circulation pump when a flow rate detected by the flow rate sensor becomes zero during the stop of the circulation pump. The control unit executes the second control to count the number of times the detected flow rate of the flow sensor becomes zero, executes the first control to set the counted number to zero when the detected flow rate of the flow sensor becomes less than the first reference flow rate while the circulation pump is in operation, and reports an abnormality when the counted number becomes equal to or exceeds a predetermined reference number.

In the above configuration, the second reference flow rate is set so that it is possible to detect that the hot water tap has been opened. In this case, for example, in a water heater connected to a path having a crossover valve, such as the second water heater described in the prior art document, the second reference flow rate is set smaller than that of the first water heater. If the second reference amount is mistakenly set smaller for the first water heater, the circulation pump in the first water heater will operate and water will circulate through the circulation path, causing the flow rate detected by the flow sensor to exceed the second reference flow rate, which may result in a false detection that the hot water tap has been opened. As a result, the circulation pump will stop. If the flow rate detected by the flow sensor exceeds the second reference flow rate due to the operation of the circulation pump, it is possible that control appropriate for the first water heater is not being executed.

According to the above configuration, even if control suitable for the second water heater is being executed for the first water heater, the number of times the flow rate detected by the flow sensor becomes zero is counted, and if the counted number exceeds a reference number, an abnormality is notified, thereby providing an opportunity to correct the execution of inappropriate control.

FIG. 2 is a diagram showing a schematic diagram of a first water heater according to an embodiment. FIG. 4 is a diagram showing a second water heater according to the embodiment; 4 is a flowchart of a first process executed in the first water heater of the embodiment. 11 is a flowchart of a second process executed in the second water heater of the embodiment. 11 is a flowchart of a third process executed in the first water heater of the embodiment.

(First water heater 2; Figure 1)
A first water heater 2 of the embodiment will be described with reference to the drawings. As shown in Fig. 1, the first water heater 2 includes a casing 80, a first water supply pipe 10, a heating unit 30, a first hot water supply pipe 20, a bypass pipe 90, and a control unit 100, and is connected to a supply path 150. The supply path 150 includes a second water supply pipe 110, a second hot water supply pipe 120, and a return pipe 40.

The second water supply pipe 110 of the supply path 150 has an upstream end connected to a water supply source (not shown) and a downstream end connected to the first water supply pipe 10 of the first water heater 2. The second water supply pipe 110 extends from the water supply source to the upstream end of the first water supply pipe 10. The second water supply pipe 110 supplies water supplied from the water supply source to the first water heater 2.

The first water supply pipe 10 is disposed within the casing 80. The first water supply pipe 10 has an upstream end connected to the second water supply pipe 110 of the supply path 150, and a downstream end connected to the heating section 30. The first water supply pipe 10 supplies the water supplied from the second water supply pipe 110 to the heating section 30. The first water supply pipe 10 is provided with a flow rate sensor 16 that detects the flow rate of water flowing through the first water supply pipe 10. The flow rate sensor 16 detects the flow rate of water downstream of a connection portion 44 between the return pipe 40 and the second water supply pipe 110, which will be described later. The first water supply pipe 10 is also provided with a check valve 14.

The heating section 30 is disposed within the casing 80. The heating section 30 includes a passage pipe 32 through which water passes, and a plate 34 for heat exchange. The passage pipe 32 is connected to the first water supply pipe 10 and the first hot water supply pipe 20. Water supplied from the first water supply pipe 10 to the heating section 30 passes through the passage pipe 32 and is supplied to the first hot water supply pipe 20. The plate 34 is heated by a heating burner 36. The heating burner 36 heats the plate 34 with the heat of combustion of gas. The heating section 30 is a heat exchanger that heats the water passing through the passage pipe 32 by heat exchange via the plate 34. The water heated by the heating section 30 is supplied to the first hot water supply pipe 20.

The first hot water supply pipe 20 is disposed within the casing 80. The upstream end of the first hot water supply pipe 20 is connected to the heating section 30, and the downstream end is connected to the second hot water supply pipe 120 of the supply path 150. The first hot water supply pipe 20 supplies water (hot water) heated by the heating section 30 to the second hot water supply pipe 120. The first hot water supply pipe 20 is provided with a temperature sensor 22 that detects the temperature of the water flowing through the first hot water supply pipe 20. The temperature sensor 22 detects the temperature of the water that has passed through the heating section 30.

The second hot water supply pipe 120 of the supply path 150 has an upstream end connected to the first hot water supply pipe 20 of the first hot water heater 2, and a downstream end connected to a hot water supply location (e.g., a faucet or shower). The second hot water supply pipe 120 extends from the downstream end of the first hot water supply pipe 20 to the hot water supply location. The second hot water supply pipe 120 supplies water (hot water) supplied from the first hot water supply pipe 20 to the hot water supply location. The second hot water supply pipe 120 is provided with a hot water supply tap 24 that opens and closes the second hot water supply pipe 120. When the hot water supply tap 24 is open, water from the second hot water supply pipe 120 is supplied to the hot water supply location. When the hot water supply tap 24 is closed, water is no longer supplied to the hot water supply location.

The return pipe 40 has an upstream end connected to the second hot water supply pipe 120 and a downstream end connected to the second water supply pipe 110. The return pipe 40 is connected to the second hot water supply pipe 120 upstream of the hot water tap 24 and to the second water supply pipe 110. The return pipe 40 returns the water in the second hot water supply pipe 120 to the second water supply pipe 110. The first water supply pipe 10 and the first hot water supply pipe 20 of the first hot water heater 2, and the second hot water supply pipe 120, the return pipe 40, and the second water supply pipe 110 of the supply path 150 form a circulation path 50 in which water circulates.

The circulation path 50 is provided with a circulation pump 42. Specifically, the circulation pump 42 is provided in the first water supply pipe 10 inside the casing 80. In a modified example, the circulation pump 42 may be provided in the second water supply pipe 110 or the return pipe 40 outside the casing 80. When the circulation pump 42 operates, the water in the circulation path 50 circulates. The circulation pump 42 circulates the water in the circulation path 50 by returning the water in the second hot water supply pipe 120 to the second water supply pipe 110 through the return pipe 40.

The bypass pipe 90 of the first water heater 2 has an upstream end connected to the first water supply pipe 10 and a downstream end connected to the first hot water supply pipe 20. The bypass pipe 90 sends water from the first water supply pipe 10 to the first hot water supply pipe 20, bypassing the heating section 30. The bypass pipe 90 is provided with a bypass valve 92. When the bypass valve 92 is opened, the water from the first water supply pipe 10 is sent to the first hot water supply pipe 20 through the bypass pipe 90.

The control unit 100 includes a CPU (not shown) and a memory unit 102. The control unit 100 executes predetermined processing and control based on a program stored in the memory unit 102. For example, the memory unit 102 stores a control program for controlling the operation of the circulation pump 42. The control unit 100 controls the operation of the circulation pump 42 based on the control program. The control unit 100 also includes a timer function and can measure time.

(Second water heater 4; Figure 2)
Next, the second water heater 4 of the embodiment will be described with reference to the drawings. Note that, among the second water heater 4, the description of the same configuration as the first water heater 2 will be omitted. As shown in FIG. 2, the second water heater 4 is connected to a supply path 150 equipped with a crossover valve 200.

The crossover valve 200 is provided in the second hot water supply pipe 120. The crossover valve 200 has ports 201 to 204 and a wax thermostat 210. Port 201 is connected to the upstream second hot water supply pipe 120, and port 202 is connected to the return pipe 40. Ports 201 and 203 are connected within the crossover valve 200. Ports 202 and 204 are connected within the crossover valve 200. The wax thermostat 210 is connected to ports 201 and 202. When the temperature of the water in the second hot water supply pipe 120 is low, the wax thermostat 210 forms a bypass path Pc between ports 201 and 202. On the other hand, when the temperature of the water in the second hot water supply pipe 120 is high, the wax thermostat 210 blocks the bypass path Pc by thermal expansion force. The temperature at which the bypass path Pc switches between open and closed is set according to the material and configuration of the wax thermostat 210.

Ports 203 and 204 of crossover valve 200 are connected to downstream second hot water pipe 120 via relay pipes 213 and 214, respectively. Manual shutoff valves 331 and 332 are provided on relay pipes 213 and 214, respectively. Second hot water heater 4 operates with shutoff valves 331 and 332 open.

In the second water heater 4, even if the capacity of the circulation pump 42 provided in the circulation path 50 is the same as that of the circulation pump 42 of the first water heater 2 described above, the presence of the crossover valve 200 causes a large pressure loss in the circulation path 50, so the detected flow rate of the flow sensor 16 is small when the circulation pump 42 is operating.

(First treatment; FIG. 3)
Next, a first process (conventional process) executed by the first water heater 2 will be described. The first process is executed based on a first control program stored in the storage unit 102. The first process is started, for example, when the power supply of the first water heater 2 is turned on. As shown in FIG. 3, in S102 of the first process, the control unit 100 judges whether a predetermined off time (for example, 20 minutes) has elapsed. The off time is the time during which the circulation pump 42 is stopped. In S102 immediately after the first process is started, the control unit 100 judges whether the elapsed time since the first process is started exceeds the off time. In addition, in S102 after the process of S116 or S120 described later is executed, the control unit 100 judges whether the elapsed time since the off timer was reset in S116 or S120 exceeds the off time. The off time can be changed, and the off time may be changed according to the hot water supply set temperature. For example, the off time may be shortened when the hot water supply set temperature is high, and the off time may be lengthened when the hot water supply set temperature is high.

In S102, the control unit 100 further determines whether or not there is an instant hot water request. An instant hot water request is generated, for example, when the temperature detected by the temperature sensor 22 installed in the first hot water pipe 20 falls below a predetermined instant hot water reference temperature. If it is determined in S102 that the off time has elapsed and that there is an instant hot water request (YES in S102), the process proceeds to S104. If the off time has not elapsed or there is no instant hot water request (NO in S102), the process waits.

In the next step S104, the control unit 100 starts the circulation pump 42. When the circulation pump 42 starts, the water in the circulation path 50 circulates. The water circulating in the circulation path 50 is heated by the heating unit 30.

In the next step S106, the control unit 100 determines whether the flow rate detected by the flow sensor 16 installed in the first water supply pipe 10 is less than a predetermined abnormal reference flow rate (e.g., 1.5 L/min). If the flow rate detected by the flow sensor 16 is less than the abnormal reference flow rate (YES in S106), the process proceeds to S118. If the flow rate detected by the flow sensor 16 is equal to or greater than the abnormal reference flow rate (NO in S106), the process proceeds to S108.

In S118 after YES in S106, the control unit 100 stops the circulation pump 42. Also in S118, the control unit 100 determines an abnormality in the first water heater 2 and notifies the abnormality. For example, the control unit 100 generates an abnormality flag indicating that the first water heater 2 is abnormal and stores the abnormality in the memory unit 102. Also, the control unit 100 turns on an indicator lamp (not shown) to notify the abnormality. Also, the control unit 100 may transmit abnormality information indicating the abnormality to an external device. When the processing of S118 ends, the first processing ends.

On the other hand, in S108 after NO in S106, the control unit 100 judges whether a predetermined ON time (e.g., 9 minutes) has elapsed since the circulation pump 42 was started in S104 above. The ON time can be changed. Also, in S108, the control unit 100 judges whether the temperature detected by the temperature sensor 22 is equal to or higher than a predetermined stop reference temperature (e.g., 40°C). The stop reference temperature is set, for example, according to the hot water supply setting temperature. If the ON time has elapsed or if the temperature detected by the temperature sensor 22 is equal to or higher than the stop reference temperature (YES in S108), the process proceeds to S120. On the other hand, if the ON time has not elapsed and the temperature detected by the temperature sensor 22 is lower than the stop reference temperature (NO in S108), the process proceeds to S110.

In S120 after YES in S108, the control unit 100 resets to zero the off timer for timing the stop time of the circulation pump 42. In the following S122, the control unit 100 stops the circulation pump 42. When the processing of S122 ends, the processing returns to S102.

On the other hand, in S110 after NO in S108, the control unit 100 determines whether the flow rate detected by the flow sensor 16 is equal to or greater than a predetermined second reference flow rate (e.g., 20 L/min). The second reference flow rate is equal to or greater than the abnormal reference flow rate (see S106). The first reference flow rate will be described later. In the first water heater 2, when the hot water tap 24 provided on the second hot water supply pipe 120 is opened to supply water from the second hot water supply pipe 120 to the hot water supply location, the flow rate of water flowing through the first water supply pipe 10 increases accordingly, and the flow rate detected by the flow sensor 16 may be equal to or greater than the second reference flow rate. If the flow rate detected by the flow sensor 16 is equal to or greater than the second reference flow rate (YES in S110), the process proceeds to S112. If the flow rate detected by the flow sensor 16 is less than the second reference flow rate (NO in S110), the process returns to S108.

In S112, the control unit 100 stops the circulation pump 42. When the circulation pump 42 stops, water does not circulate in the circulation path 50 unless the hot water tap 24 is open (closed). As a result, the flow rate detected by the flow sensor 16 becomes zero. On the other hand, even if the circulation pump 42 stops, if the hot water tap 24 is open, water from the second hot water supply pipe 120 is supplied to the hot water supply location, so the flow rate detected by the flow sensor 16 does not become zero.

In the next step S114, the control unit 100 determines whether the flow rate detected by the flow sensor 16 is zero. When the hot water tap 24 is closed, the flow rate detected by the flow sensor 16 is zero. When the flow rate detected by the flow sensor 16 is below an extremely small threshold (a threshold close to zero), it is determined that the flow rate detected by the flow sensor 16 is zero. When the flow rate detected by the flow sensor 16 is zero (YES in S114), the process proceeds to S116. When the flow rate detected by the flow sensor 16 is not zero (NO in S114), the process waits. When the flow rate detected by the flow sensor 16 is not zero, the hot water tap 24 is open.

In S116, the control unit 100 resets to zero the off timer for timing the stop time of the circulation pump 42. When the process of S116 ends, the process returns to S102. The above is the description of the first process.

(Second treatment; FIG. 4)
Next, the second process (conventional process) executed by the second water heater 4 will be described. The second process is executed based on the second control program stored in the storage unit 102. The second process is started, for example, when the power supply of the second water heater 4 is turned on. As shown in FIG. 4, in S202 of the second process, the control unit 100 judges whether a predetermined off time (for example, 10 minutes) has elapsed. In S202 immediately after the second process is started, the control unit 100 judges whether the elapsed time since the second process is started exceeds the off time. In addition, in S202 after the process of S214 described later is executed, the control unit 100 judges whether the elapsed time since the off timer is reset in S214 exceeds the off time. The off time can be changed. The off time in the second process is set to a time shorter than the off time (see S102) in the first process (see FIG. 3) described above. The off time in the second process is set to a fixed time (for example, 10 minutes) regardless of the hot water supply setting temperature. In the second hot water heater 4, when the temperature of the water in the second hot water supply pipe 120 becomes low, the bypass path Pc of the crossover valve 200 is formed. It is preferable that the circulation pump 42 starts at the timing when the bypass path Pc of the crossover valve 200 is formed (the timing when the temperature of the water in the second hot water supply pipe 120 becomes low), but it is difficult to grasp the timing when the bypass path Pc of the crossover valve 200 is formed. Therefore, in the second process, the off time is set to a uniformly short time. In a modified example, the off time may be changed according to the hot water supply set temperature. For example, the off time may be shortened when the hot water supply set temperature is high, and the off time may be lengthened when the hot water supply set temperature is high.

In S202, the control unit 100 further determines whether or not there is an instant hot water request. An instant hot water request is generated, for example, when the temperature detected by the temperature sensor 22 falls below a predetermined instant hot water reference temperature. If it is determined in S202 that the off time has elapsed and that there is an instant hot water request (YES in S202), the process proceeds to S204. If the off time has not elapsed or there is no instant hot water request (NO in S202), the process waits.

In the next step S204, the control unit 100 starts the circulation pump 42. When the circulation pump 42 starts, the water in the circulation path 50 circulates. The water circulating in the circulation path 50 is heated by the heating unit 30.

In the next step S206, the control unit 100 determines whether a predetermined ON time (e.g., 9 minutes) has elapsed since the circulation pump 42 was started in S204. The ON time can be changed. Also in S206, the control unit 100 determines whether the flow rate detected by the flow sensor 16 is less than a predetermined first reference flow rate (e.g., 1 L/min). If the ON time has elapsed, or if the flow rate detected by the flow sensor 16 is less than the first reference flow rate (YES in S206), the process proceeds to S214. On the other hand, if the ON time has not elapsed and the flow rate detected by the flow sensor 16 is equal to or greater than the first reference flow rate (NO in S206), the process proceeds to S208.

In S214 after YES in S206, the control unit 100 resets to zero the off timer for timing the stop time of the circulation pump 42. In the following S216, the control unit 100 stops the circulation pump 42. When the processing of S216 ends, the processing returns to S202.

On the other hand, in S208 after NO in S206, the control unit 100 judges whether the detected flow rate of the flow sensor 16 is equal to or greater than a predetermined second reference flow rate (e.g., 6 L/min). The second reference flow rate is equal to or greater than the first reference flow rate (see S206). The second reference flow rate in the second process is equal to or less than the second reference flow rate (see S110) in the first process (see FIG. 3). In the second water heater 4, when the hot water tap 24 is opened and water from the second hot water supply pipe 120 is supplied to the hot water supply location, the flow rate of the water flowing through the first water supply pipe 10 increases accordingly, and the detected flow rate of the flow sensor 16 may be equal to or greater than the second reference flow rate. If the detected flow rate of the flow sensor 16 is equal to or greater than the second reference flow rate (YES in S208), the process proceeds to S210. If the detected flow rate of the flow sensor 16 is less than the second reference flow rate (NO in S208), the process returns to S206.

In S210, the control unit 100 stops the circulation pump 42. When the circulation pump 42 stops, water does not circulate in the circulation path 50 unless the hot water tap 24 is open (closed). As a result, the flow rate detected by the flow sensor 16 becomes zero. On the other hand, even if the circulation pump 42 stops, if the hot water tap 24 is open, water from the second hot water supply pipe 120 is supplied to the hot water supply location, so the flow rate detected by the flow sensor 16 does not become zero.

In the next step S212, the control unit 100 determines whether the flow rate detected by the flow sensor 16 becomes zero. When the hot water tap 24 is closed, the flow rate detected by the flow sensor 16 becomes zero. If the flow rate detected by the flow sensor 16 becomes zero (YES in S212), the process returns to S204. If the flow rate detected by the flow sensor 16 does not become zero (NO in S212), the process waits. This concludes the second process.

The second process (see FIG. 4) described above is a control suitable for the second water heater 4 (see FIG. 2) and should be executed by the second water heater, but if this second process is executed by the first water heater 2 (see FIG. 1), the first water heater 2 may operate abnormally because the control is inappropriate for the first water heater 2. For example, since the supply path 150 to which the first water heater 2 is connected does not have a crossover valve 200, when the circulation pump 42 operates, the detected flow rate of the flow sensor 16 may become equal to or greater than the second reference flow rate even if the hot water tap 24 is not open (YES in S208). When this happens, the circulation pump 42 stops (S210), and since the hot water tap 24 is not open, the detected flow rate of the flow sensor 16 becomes zero (YES in S212), and as a result, the circulation pump 42 starts again (S204). However, when the circulation pump 42 starts operating, the flow rate detected by the flow sensor 16 again becomes equal to or greater than the second reference flow rate (YES in S208), and as a result, the circulation pump 42 stops again (S210). Therefore, the circulation pump 42 stops and starts repeatedly.

(Third treatment; FIG. 5)
Next, the third process will be described. The third process is originally a control appropriate for execution in the second water heater 4, but here, a case will be described in which the third process is executed in the first water heater 2, i.e., a control inappropriate for the first water heater 2 is executed. The third process is executed based on a third control program stored in the memory unit 102. The third process is executed to solve the above problem. The third process is started, for example, when the power of the first water heater 2 is turned on.

As shown in FIG. 5, in S302 of the third process, the control unit 100 determines whether a predetermined off time (an example of the second reference time, for example, 10 minutes) has elapsed. In S302 immediately after the third process is started, the control unit 100 determines whether the time elapsed since the third process is started exceeds the off time. Also, in S302 after the process of S320 or S324 described below is executed, the control unit 100 determines whether the time elapsed since the off timer was reset in S320 or S324 exceeds the off time. The off time can be changed.

In S302, the control unit 100 further determines whether or not there is an instant hot water request. An instant hot water request is generated, for example, when the temperature detected by the temperature sensor 22 falls below a predetermined instant hot water reference temperature. If it is determined in S302 that the off time has elapsed and that there is an instant hot water request (YES in S302), the process proceeds to S304. If the off time has not elapsed or there is no instant hot water request (NO in S302), the process waits.

In the next step S304, the control unit 100 starts the circulation pump 42. When the circulation pump 42 starts, the water in the circulation path 50 circulates. The water circulating in the circulation path 50 is heated by the heating unit 30.

In the next step S306, the control unit 100 determines whether a predetermined ON time (one example of a first reference time, for example, 9 minutes) has elapsed since the circulation pump 42 was started in S304. The ON time can be changed. Also in S306, the control unit 100 determines whether the flow rate detected by the flow sensor 16 is less than a predetermined first reference flow rate (for example, 1 L/min). If the ON time has elapsed or if the flow rate detected by the flow sensor 16 is less than the first reference flow rate (YES in S306), the process proceeds to S320. If the ON time has not elapsed and the flow rate detected by the flow sensor 16 is equal to or greater than the first reference flow rate (NO in S306), the process proceeds to S308.

In S320 after YES in S306, the control unit 100 resets to zero the off timer for timing the stop time of the circulation pump 42. Also in S320, the control unit 100 resets to zero the cumulative number of times the detected flow rate of the flow sensor 16 becomes zero (see S314 and S316 described below). In the following S322, the control unit 100 stops the circulation pump 42. When the processing of S322 is completed, the processing returns to S302.

On the other hand, in S308 after NO in S306, the control unit 100 determines whether the detected flow rate of the flow sensor 16 is equal to or greater than a predetermined second reference flow rate (e.g., 6 L/min). The second reference flow rate is equal to or greater than the first reference flow rate (see S306). When the water heater on which the third process is being performed is the first water heater 2, when the water supply valve 24 provided on the second water supply pipe 120 is opened to supply water from the second water supply pipe 120 to the hot water supply location, the flow rate of the water flowing through the first water supply pipe 10 increases accordingly, and the detected flow rate of the flow sensor 16 may be equal to or greater than the second reference flow rate. In addition, when the water heater on which the third process is being performed is the first water heater 2, even if the water supply valve 24 is not open (closed), the water in the circulation path 50 circulates while the circulation pump 42 is operating, and the detected flow rate of the flow sensor 16 may be equal to or greater than the second reference flow rate. If the flow rate detected by the flow sensor 16 is equal to or greater than the second reference flow rate (YES in S308), processing proceeds to S310. If the flow rate detected by the flow sensor 16 is less than the second reference flow rate (NO in S308), processing returns to S306.

If the water heater on which the third process is being executed is the second water heater 4, it can be determined that the hot water tap 24 is open if the detected flow rate of the flow sensor 16 is equal to or greater than the second reference flow rate. In the second water heater 4, when the hot water tap 24 is not open (closed), the presence of the crossover valve 200 prevents the detected flow rate of the flow sensor 16 from being equal to or greater than the second reference flow rate, even if the circulation pump 42 is operating.

In S310 after YES in S308, the control unit 100 stops the circulation pump 42. When the circulation pump 42 stops, water does not circulate in the circulation path 50 unless the hot water tap 24 is open (closed). Therefore, the flow rate detected by the flow sensor 16 becomes zero. On the other hand, even if the circulation pump 42 stops, if the hot water tap 24 is open, water from the second hot water supply pipe 120 is supplied to the hot water supply location, so the flow rate detected by the flow sensor 16 does not become zero.

In the next step S312, the control unit 100 determines whether the flow rate detected by the flow sensor 16 becomes zero. If the flow rate detected by the flow sensor 16 becomes zero (YES in S312), the process proceeds to S314. If the flow rate detected by the flow sensor 16 does not become zero (NO in S312), the process proceeds to S324.

In S314, the control unit 100 increments the number of times that the flow rate detected by the flow sensor 16 becomes zero by +1. In the following S316, the control unit 100 determines whether the cumulative number of times counted in S314 is equal to or greater than a predetermined reference number. If the cumulative number is equal to or greater than the reference number (YES in S316), the process proceeds to S318. If the cumulative number is less than the reference number (NO in S316), the process returns to S304.

In S318, the control unit 100 determines an abnormality in the first water heater 2 and notifies the abnormality. For example, the control unit 100 generates an abnormality flag indicating that the setting in the first water heater 2 is abnormal, and stores the abnormality in the memory unit 102. The control unit 100 also turns on an indicator lamp (not shown) to notify the abnormality in the settings. The control unit 100 may also transmit abnormality information indicating the abnormality in the settings to an external device. When the processing of S318 ends, the third processing ends.

In S324 after NO in S312 above, the control unit 100 makes a normal determination. For example, the control unit 100 generates a normal flag indicating that the settings in the first water heater 2 are normal and stores it in the memory unit 102. If the result is NO in S312, this is because the hot water tap 24 may have actually been opened, causing the detected flow rate in S308 to be equal to or greater than the second reference flow rate. The control unit 100 may also send normal information indicating that the settings are normal to an external device.

In addition, in S324, the control unit 100 resets to zero the off timer for timing the stop time of the circulation pump 42. When the processing of S324 ends, the processing returns to S302.

The above describes the first water heater 2 and the third process of the embodiment. As is clear from the above description, the first water heater 2 includes a circulation pump 42 that circulates the water in the circulation path 50, and a flow sensor 16 that detects the flow rate of the water flowing through the first water supply pipe 10. The control unit 100 controls the operation of the circulation pump 42 based on the third control program. The third control program is set to cause the control unit 100 to execute the first control in which the circulation pump 42 is stopped when a first reference time has elapsed since the circulation pump 42 was started, or when the flow rate detected by the flow sensor 16 becomes less than the first reference flow rate while the circulation pump 42 is in operation, and the circulation pump 42 is started when a second reference time has elapsed since the circulation pump 42 was stopped (YES in S306, S322, S302). The third control program is set to cause the control unit 100 to execute a second control in which the circulation pump 42 is stopped when the flow rate detected by the flow sensor 16 becomes equal to or greater than the second reference flow rate, and the hot water tap 24 is determined to be closed and the circulation pump 42 is started when the flow rate detected by the flow sensor 16 becomes zero while the circulation pump 42 is stopped (YES in S308, YES in S310 and S312, NO in S316, S304). The control unit 100 executes the second control to count the number of times the flow rate detected by the flow sensor 16 becomes zero (S314), executes the first control to set the counted number to zero when the flow rate detected by the flow sensor 16 becomes less than the first reference flow rate while the circulation pump 42 is in operation (S320), and reports an abnormality when the counted number becomes equal to or greater than a predetermined reference number (YES in S316, S318).

With this configuration, even if the third control program suitable for the second water heater 4 is executed in the first water heater 2, the number of times the detected flow rate of the flow sensor 16 becomes zero is counted and the accumulated number is compared with a reference number, so that the user can be notified that inappropriate control is being executed. This provides an opportunity to correct the execution of inappropriate control.

(Modification)
When executing the process of S318 of the third process (see FIG. 5), the control unit 100 may change the setting of the off time (see S302) according to the hot water supply temperature setting. For example, the off time may be shortened when the hot water supply temperature setting is high, and the off time may be lengthened when the hot water supply temperature setting is high.

Although each embodiment has been described in detail above, these are merely examples and do not limit the scope of the claims. The technology described in the claims includes various modifications and variations of the specific examples exemplified above. The technical elements described in this specification or drawings exert technical utility alone or in various combinations, and are not limited to the combinations described in the claims at the time of filing. Furthermore, the technology exemplified in this specification or drawings can achieve multiple objectives simultaneously, and achieving one of those objectives is itself technically useful.

2: first water heater, 4: second water heater, 10: water supply pipe, 16: flow rate sensor, 20: hot water supply pipe, 22: temperature sensor, 24: hot water tap, 30: heating section, 32: passage pipe, 34: plate, 36: heating burner, 40: return pipe, 42: circulation pump, 44: connection section, 50: circulation path, 80: casing, 90: bypass pipe, 92: bypass valve, 100: control section, 102: memory section, 200: crossover valve, 210: wax thermo

Claims (1)

A heating unit that heats water;
A first water supply pipe connected to the heating unit and supplying water to the heating unit;
A water heater including: a first hot water supply pipe connected to the heating unit and supplying water heated by the heating unit;
a second water supply pipe extending from a water supply source to an upstream end of the first water supply pipe, a second hot water supply pipe extending from a downstream end of the first hot water supply pipe to a hot water supply location, a hot water tap for opening and closing the second hot water supply pipe, and a return pipe connected to the second hot water supply pipe and the second water supply pipe upstream of the hot water tap and returning water from the second hot water supply pipe to the second water supply pipe,
A circulation path through which water circulates is formed by the first water supply pipe, the first hot water supply pipe, the second hot water supply pipe, the return pipe, and the second water supply pipe,
The water heater comprises:
A circulation pump provided in the circulation path for circulating water in the circulation path;
a flow rate sensor for detecting a flow rate of water flowing through the first water supply pipe;
A control unit that controls the operation of the circulating pump based on a control program,
The control program includes:
a first control that stops the circulation pump when a predetermined first reference time has elapsed since the start of the circulation pump, or when a flow rate detected by the flow sensor becomes less than a predetermined first reference flow rate during operation of the circulation pump, and starts the circulation pump when a predetermined second reference time has elapsed since the stop of the circulation pump;
a second control for stopping the circulation pump when the flow rate detected by the flow sensor becomes equal to or greater than a predetermined second reference flow rate that is equal to or greater than the first reference flow rate due to the operation of the circulation pump, and for starting the circulation pump by determining that the hot water tap is closed when the flow rate detected by the flow sensor becomes zero while the circulation pump is stopped;
The control unit counts the number of times the detected flow rate of the flow sensor becomes zero by executing the second control, sets the counted number to zero when the detected flow rate of the flow sensor becomes less than the first reference flow rate while the circulation pump is operating by executing the first control, and alerts of an abnormality when the counted number becomes equal to or greater than a predetermined reference number.

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