Water heater

Abstract

To suppress low-temperature hot water supply from one combustion unit without impairing usability of the other combustion units.SOLUTION: A hot water supply heater 1 comprises a hot water combustion unit 4A, a heating combustion unit 5A, one combustion fan 10 shared by these combustion units, and a control board 79. The hot water combustion unit 4A has: a water supply pipe 22 that supplies water supplied from a water inlet to heat exchangers (hot water primary heat exchanger 11 and hot water secondary heat exchanger 12); a hot water outlet pipe 27 that discharges hot water heated by the heat exchanger from a hot water outlet; a bypass pipe 30 that is connected to the water supply pipe 22 and the hot water outlet pipe 27 and short-circuits the water inlet and the hot water outlet without passing through the heat exchangers; and a bypass valve 31 that opens and closes the bypass pipe 30. The control board 79 controls the opening of the bypass valve 31 to be smaller when the combustion fan 10 rotates after combustion of the hot water combustion section 4A has stopped than when the combustion fan 10 does not rotate.SELECTED DRAWING: Figure 4

Description

Technical Field

[0001] The technology disclosed in this specification relates to a water heater.

Background Art

[0002] Conventionally, a water heater that shares one combustion fan between two combustion units has been known. In such a water heater, after one combustion unit stops combustion, when the combustion fan starts rotating due to the combustion of the gas burner of the other combustion unit, etc., the heat exchanger of one combustion unit is cooled. Therefore, when one water heater resumes combustion, there is a risk of low-temperature hot water discharge where hot water significantly lower than the target temperature is discharged.

[0003] For this reason, conventionally, a technology for suppressing low-temperature hot water discharge has been known (see, for example, Patent Document 1). Specifically, the hot water supply system described in Patent Document 1 includes a water heater and a heat dissipation device. The water heater includes a first heat exchanger for hot water supply and a first combustion chamber that houses a first burner, a second heat exchanger for a heating circuit and a second combustion chamber that houses a second burner, and a combustion fan that operates during combustion of at least one of the first and second burners to blow air into both the first and second combustion chambers. In this hot water supply system, during a predetermined period after the hot water supply operation stops, transmission of an operation request from the heat dissipation device to the water heater is prohibited, etc. Thereby, if the hot water supply operation is not resumed after the hot water supply operation stops, the combustion fan is maintained in a stopped state (or a state of a small air volume), and cooling of the hot water supply side heat exchanger (first heat exchanger) by the air blown from the combustion fan is suppressed, preventing a significant drop in the hot water discharge temperature when the hot water supply resumes.

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0005] However, in the water supply system described in Patent Document 1, during a predetermined period after the stop of the water supply operation, the transmission of an operation request from the heat dissipation device to the water heater is prohibited, etc., so the water heater cannot be used during the predetermined period. For this reason, there is a risk that the usability will be impaired. One aspect of the present invention aims to suppress low-temperature hot water discharge of one combustion unit without impairing the usability of the other combustion unit.

Means for Solving the Problems

[0006] The water heater of the present disclosure includes two combustion units having a gas burner and a heat exchanger that heats water by the combustion heat of the gas burner, one combustion fan shared by the two combustion units, and a controller. One of the combustion units includes a water supply pipe that supplies water supplied from a water inlet to the heat exchanger, a hot water outlet pipe that discharges hot water heated by the heat exchanger from a hot water outlet, is connected to the water supply pipe and the hot water outlet pipe, and short-circuits the water inlet and the hot water outlet without passing through the heat exchanger. a bypass pipe, and a bypass valve that opens and closes the bypass pipe. When the combustion fan rotates after the combustion of one of the combustion units stops, the controller reduces the opening degree of the bypass valve compared to when the combustion fan does not rotate.

Advantages of the Invention

[0007] According to the above configuration, it is possible to suppress low-temperature hot water discharge of one combustion unit without impairing the usability of the other combustion unit.

Brief Description of the Drawings

[0008]

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5

Mode for Carrying Out the Invention

[0009] [Outline of Embodiment] First, the outline of the embodiment of the present disclosure will be listed and explained.

[0010] (1) The water heater according to the embodiment includes two combustion sections having a gas burner and a heat exchanger that heats water by the combustion heat of the gas burner, one combustion fan shared by the two combustion sections, and a controller. One of the combustion sections includes a water supply pipe that supplies water supplied from a water inlet to the heat exchanger, a hot water outlet pipe that discharges hot water heated by the heat exchanger from a hot water outlet, a bypass pipe that is connected to the water supply pipe and the hot water outlet pipe and short-circuits the water inlet and the hot water outlet without passing through the heat exchanger, and a bypass valve that opens and closes the bypass pipe. When the combustion fan rotates after the combustion of one of the combustion sections has stopped, the controller reduces the opening degree of the bypass valve compared to the case where the combustion fan does not rotate.

[0011] When the water heater is supplying hot water by burning one of the combustion sections, if the flow of water in the heat exchanger of one of the combustion sections stops, the combustion of one of the combustion sections is stopped. When the flow of water in the heat exchanger stops, the hot water in the heat exchanger is heated by the residual heat of the heat exchanger and after-boiling occurs. If the combustion of one of the combustion sections resumes in a state where after-boiling is occurring (in other words, when the operation of supplying hot water is started), there is a possibility of high-temperature hot water discharge where hot water significantly higher than the temperature (target temperature) set by the user is discharged. If the opening degree of the bypass valve is increased to a certain extent after the combustion of one combustion part stops, when the combustion of one combustion part restarts, the water from the bypass pipe can be mixed into the hot water that has become hot due to after-boiling, thereby suppressing the high-temperature hot water discharge. The opening degree of the bypass valve immediately after the combustion of one combustion part stops is preferably an opening degree at which hot water at the target temperature or a temperature close thereto is discharged even if the combustion of one combustion part restarts immediately after the combustion of one combustion part stops. Such an opening degree can be determined by experiments in advance.

[0012] However, when one combustion part stops combustion while both combustion parts are performing combustion, or when the combustion of the other combustion part starts while the combustion of both combustion parts has stopped, the combustion fan rotates when one combustion part has stopped combustion. In this case, since the temperature of the hot water in the heat exchanger of one combustion part decreases due to the air supply from the combustion fan, when the combustion of one combustion part restarts thereafter, if the opening degree of the bypass valve remains large, the water from the bypass pipe may be mixed more than necessary, resulting in low-temperature hot water discharge.

[0013] According to the water heater described in (1) above, when the combustion fan rotates after the combustion of one combustion part stops, the opening degree of the bypass valve is made smaller than when the combustion fan does not rotate, so that low-temperature hot water discharge can be suppressed even when the combustion fan rotates. Furthermore, according to the water heater described in (1) above, since low-temperature hot water discharge can be suppressed even when the combustion fan rotates, it is not necessary to prohibit the combustion of the other combustion part when one combustion part has stopped combustion. Therefore, the usability of the other combustion part is not impaired. Therefore, according to the water heater described in (1) above, low-temperature hot water discharge of one combustion part can be suppressed without impairing the usability of the other combustion part.

[0014] (2) The water heater described in (1) above, wherein the controller may increase the opening degree of the bypass valve stepwise or continuously until a first specified time elapses after the combustion of the one combustion part stops, and may decrease the opening degree of the bypass valve stepwise or continuously when the first specified time elapses.

[0015] According to the water heater described in (2) above, when the combustion of one combustion part stops, the opening degree of the bypass valve is increased stepwise or continuously until the first specified time elapses. The reason for increasing the opening degree of the bypass valve stepwise or continuously is that since the temperature of the hot water in the heat exchanger rises due to after-boiling, high-temperature hot water is suppressed by increasing the opening degree of the bypass valve accordingly. The first specified time is preferably the time or a time close thereto until the temperature of the hot water in the heat exchanger becomes the highest due to after-boiling after the combustion of one combustion part stops. Such a time can be determined in advance by experiments.

[0016] However, since the temperature of the hot water in the heat exchanger decreases as time elapses after the combustion stops, if the opening degree of the bypass valve is large, when the combustion of one combustion part restarts, water from the bypass pipe may be mixed more than necessary, resulting in low-temperature hot water. According to the water heater described in (2) above, when the first specified time elapses, the opening degree of the bypass valve is decreased stepwise or continuously, so low-temperature hot water can be suppressed.

[0017] (3) The water heater described in (1) or (2) above, wherein the controller may decrease the opening degree of the bypass valve when the cumulative rotation time of the combustion fan from when the combustion of one combustion part stops reaches a second specified time.

[0018] According to the water heater in (3) above, even if the combustion fan rotates after the combustion of one combustion part stops, the opening degree of the bypass valve is not decreased until the cumulative rotation time of the combustion fan from when the combustion of one combustion part stops reaches the second specified time. Therefore, high-temperature hot water can be suppressed compared to the case where the opening degree of the bypass valve is decreased immediately when the combustion fan starts rotating. On the other hand, when the cumulative rotation time reaches the second specified time, the opening degree of the bypass valve is decreased, so low-temperature hot water can be suppressed.

[0019] (4) The water heater according to (3) above, wherein when the cumulative rotation time reaches the second specified time and the opening degree of the bypass valve is reduced, the controller may reduce the opening degree of the bypass valve step by step.

[0020] The temperature of the hot water in the heat exchanger decreases over time. According to the water heater described in (4) above, since the amount of water mixed into the hot water in the heat exchanger decreases step by step over time, when combustion starts immediately after the second specified time has elapsed, the difference between the temperature of the hot water discharged and the temperature of the hot water discharged when combustion starts after a certain time has elapsed since the second specified time has elapsed can be reduced. That is, the temperature of the hot water discharged after the second specified time has elapsed can be made substantially the same.

[0021] (5) The water heater according to (3) above, wherein the one combustion unit has a plurality of the gas burners, and the number of the gas burners to be combusted can be switched, and the controller may vary the second specified time according to the number of the gas burners that were combusting immediately before the one combustion unit stops combustion.

[0022] The degree of temperature overshoot that occurs in the heat exchanger after combustion stops varies depending on the number of gas burners that were combusting immediately before combustion stops. For this reason, if the second specified time is made the same regardless of the number of gas burners that were combusting immediately before, the temperature of the hot water discharged after the second specified time has elapsed may vary significantly depending on the number of gas burners that were combusting immediately before combustion stops. According to the water heater described in (5) above, since the second specified time is varied according to the number of gas burners that were combusting immediately before the one combustion unit stops combustion, the temperature of the hot water discharged after the second specified time has elapsed can be made substantially the same regardless of the number of gas burners that were combusting immediately before the one combustion unit stops combustion.

[0023] (6) The water heater according to (3) above, when the gas input amount at which hot water of the target temperature is discharged is defined as the normal gas input amount, if the controller starts the combustion of the one combustion unit after the second specified time has elapsed, the gas input amount to the gas burner may be made larger than the normal gas input amount until a certain time has elapsed since the start of the combustion.

[0024] At the time when the second specified time has elapsed, the temperature of the hot water in the heat exchanger has decreased. According to the water heater described in (6) above, since the gas input amount is made larger than the normal gas input amount until a certain time has elapsed since the start of the combustion, the heating amount can be increased. Thereby, the target temperature can be reached quickly.

[0025] (7) The water heater according to (3) above, comprising a first temperature sensor that detects the temperature of the hot water on the downstream side of the heat exchanger in the hot water discharge pipe and on the upstream side of the confluence position with the bypass pipe, and if the controller starts the combustion of the one combustion unit after the second specified time has elapsed, the opening degree of the bypass valve immediately before the start of the combustion may be maintained until the temperature detected by the first temperature sensor reaches a predetermined temperature.

[0026] When the elapsed time since the combustion fan started rotating has passed the second specified time, the opening degree of the bypass valve immediately before the start of the combustion is small. If the opening degree of the bypass valve immediately before the start of the combustion is maintained until the temperature of the hot water on the downstream side of the heat exchanger in the hot water discharge pipe and on the upstream side of the confluence position with the bypass pipe reaches a predetermined temperature, the amount of water mixed into the hot water can be reduced. Thereby, the target temperature can be reached quickly. The above-mentioned predetermined temperature may be a temperature higher than the target temperature. This is because even if the predetermined temperature is higher than the target temperature, the hot water discharge temperature can be lowered to the target temperature by mixing the water from the bypass pipe.

[0027] (8) The water heater according to (3) above, comprising a second temperature sensor for detecting the temperature of the water supplied from the water inlet, wherein the controller may vary the second specified time according to the temperature of the water detected by the second temperature sensor.

[0028] When the temperature of the water supplied from the water inlet (inlet water temperature) is low, if the second specified time is long, the time for cold water to mix into the hot water will be long, and there is a possibility of low-temperature hot water discharge. Specifically, when the inlet water temperature is low, the temperature drop in the heat exchanger due to the hot water circulation becomes faster. Also, when mixing low-temperature water during hot water discharge, the hot water discharge temperature will drop too much. Therefore, it was necessary to close the bypass valve quickly. Conversely, when the inlet water temperature is high, if the second specified time is short, the temperature of the reheated hot water may not drop sufficiently, and there is a possibility of high-temperature hot water discharge. According to the water heater described in (8) above, since the second specified time is varied according to the inlet water temperature detected by the second temperature sensor, low-temperature hot water discharge and high-temperature hot water discharge can be suppressed. As a modification, for a water heater capable of measuring the air supply temperature, by varying the second specified time according to the inlet water temperature and the air supply temperature, low-temperature hot water discharge and high-temperature hot water discharge can be more reliably suppressed.

[0029] [Details of Embodiment] Details of the embodiment of the present disclosure will be described. The present disclosure is not limited to these examples, and is shown by the claims, and is intended to include all modifications within the meaning and scope equivalent to the claims. The embodiment of the present disclosure can be realized in various forms such as an apparatus, a method, a computer program for realizing the functions of these apparatuses or methods, and a recording medium recording the computer program.

[0030] [Embodiment 1] The embodiment of the present disclosure will be described with reference to FIGS. 1 to 5. In the following description, the reference numerals of the drawings may be omitted for some of the same components.

[0031] (1) Overall Structure of the Water Heater with Heating Function Referring to FIG. 1, the outline of the hot water heater 1 as a hot water supply and heating device according to Embodiment 1 will be described. The hot water supply and heating device 1 has a hot water supply function of heating the supplied tap water and supplying hot water to the outside, and a heating function of supplying hot water to radiators installed in the indoor or underfloor area outside and heating the indoor or floor. The hot water supply and heating device 1 includes a front cover 72. The front cover 72 has an exhaust port 73 for accommodating an exhaust pipe 16 described later, an air supply port 74 for taking in outside air, and the like.

[0032] As shown in FIG. 2, the hot water supply and heating device 1 includes a housing 70, an inner cylinder 2 accommodated in the housing 70, a control board 79 (an example of a controller), and the like. The housing 70 includes a box-shaped housing main body 71 having an opening 71A on the front surface, and a front cover 72 (see FIG. 1) that closes the opening 71A of the housing main body 71. The housing main body 71 includes a bottom plate 71B located on the lower side in a front view, a left side plate 71C located on the left side in a front view, a right side plate 71D located on the right side in a front view, a top plate 71E located on the upper side in a front view, and a rear wall 71F located on the rear side.

[0033] The inner cylinder 2 includes a hot water supply combustion chamber 4, a heating combustion chamber 5, a hot water supply primary heat exchanger 11, a heating primary heat exchanger 13, a hot water supply secondary heat exchanger 12, a heating secondary heat exchanger 14, an exhaust hood 15, and the like. The inner cylinder 2 is partitioned left and right by a partition member 3 (see FIG. 3) described later. The hot water supply combustion chamber 4, the hot water supply primary heat exchanger 11, and the hot water supply secondary heat exchanger 12 are provided on the right side, and the heating combustion chamber 5, the heating primary heat exchanger 13, and the heating secondary heat exchanger 14 are provided on the left side.

[0034] As shown in FIG. 3, the hot water supply and heating device 1 has a hot water supply circuit A, a heating circuit B, and a bath circuit C. The water heater and space heater 1 has a water heating combustion chamber 4 and a space heating combustion chamber 5 formed by a partition member 3 inside an inner cylinder 2, and a gas burner 6. The gas burner 6 includes a plurality of water heating burners 6A arranged at the lower part of the water heating combustion chamber 4 and a plurality of space heating burners 6B arranged at the lower part of the space heating combustion chamber 5. An ignition plug 8 and a flame rod 9 are respectively provided in each of the combustion chambers 4 and 5. A combustion fan 10 for supplying combustion air to each of the gas burners 6A and 6B is provided at the lower part of the inner cylinder 2.

[0035] At the upper part inside the water heating combustion chamber 4, a water heating primary heat exchanger 11 and a water heating secondary heat exchanger 12 through which the combustion exhaust gas of the water heating burner 6A passes are provided. At the upper part of the space heating combustion chamber 5, a space heating primary heat exchanger 13 and a space heating secondary heat exchanger 14 through which the combustion exhaust gas of the space heating burner 6B passes are provided. Each of the secondary heat exchangers 12 and 14 is housed in an exhaust hood 15 provided at the upper part of the inner cylinder 2. An exhaust pipe 16 for discharging the combustion exhaust gas that has passed through each of the secondary heat exchangers 12 and 14 is formed in the exhaust hood 15.

[0036] In the following description, the water heating burner 6A, the water heating primary heat exchanger 11, and the water heating secondary heat exchanger 12 are referred to as a water heating combustion part 4A, and the space heating burner 6B, the space heating primary heat exchanger 13, and the space heating secondary heat exchanger 14 are referred to as a space heating combustion part 5A. The water heating combustion part 4A is an example of one of the combustion parts.

[0037] A gas pipe 17 to which an external gas pipe is connected is connected to a gas inlet provided on the bottom plate 71B of the housing 70. Gas branch pipes 18, 18... branched from the gas pipe 17 are respectively connected to each of the water heating burners 6A and the space heating burners 6B, and a gas solenoid valve 19 for opening and closing a gas flow path is respectively provided in each of the gas branch pipes 18. Further, an original gas solenoid valve 20 and a gas proportional valve 21 are respectively provided in the gas pipe 17 before branching.

[0038] At the inlet of the heat absorption pipe of the secondary hot water heat exchanger 12, a water supply pipe 22 connected to the water inlet 78 of the bottom plate 71B is connected. In the water supply pipe 22, from the upstream side, there are a strainer 23 equipped with a drain plug, a hot water supply amount sensor 24 for detecting the amount of water flowing through the water supply pipe 22, a hot water supply inlet thermistor 25 (an example of a second temperature sensor) for detecting the temperature of the water (inlet water temperature) supplied from the water inlet 78, and a water amount control valve 26 for controlling the amount of water flowing through the water supply pipe 22.

[0039] The outlet of the heat absorption pipe is connected to the inlet of the heat transfer pipe of the primary hot water heat exchanger 11, and at the outlet of the heat transfer pipe, a hot water outlet pipe 27 connected to the hot water outlet 77 of the bottom plate 71B is connected. In the hot water outlet pipe 27, there are a hot water heat exchanger thermistor 28 (an example of a first temperature sensor) for detecting the outlet temperature from the primary hot water heat exchanger 11, and a hot water outlet thermistor 29 for detecting the hot water outlet temperature from the appliance downstream of the hot water heat exchanger thermistor 28. Between the upstream side of the hot water outlet thermistor 29 in the hot water outlet pipe 27 and the downstream side of the water amount control valve 26 in the water supply pipe 22, a bypass pipe 30 bypassing the primary and secondary hot water heat exchangers 11 and 12 is connected, and in the bypass pipe 30, a bypass valve 31 for controlling the bypass flow rate is provided. In this way, in the housing 70, a hot water supply circuit A is formed in which water from the water supply pipe 22 passes through the secondary hot water heat exchanger 12 and the primary hot water heat exchanger 11 in sequence, exchanges heat with the combustion exhaust of the hot water supply burner 6A and is heated, and then hot water is discharged from the hot water outlet pipe 27.

[0040] On the other hand, at the inlet of the heat absorption pipe of the secondary heating heat exchanger 14, a heating return pipe 32 connected to the heating return port 76 of the bottom plate 71B is connected. The heating return port 76 is connected to the downstream end of the pipes extending from the high-temperature radiator 33 and the low-temperature radiator 34 outside the hot water supply and heating unit 1. The high-temperature radiator 33 is, for example, a heating blower that blows warm air into the room. The low-temperature radiator 34 is, for example, floor heating. The outlet of the heat absorption pipe of the secondary heating heat exchanger 14 is connected to an intermediate pipe 35 (intermediate pipes 35A and 35B). In the intermediate pipe 35, a heating tank 69 and a heating circulation pump 36 are provided.

[0041] The downstream end of the intermediate pipe 35 is connected to the inlet of the heat transfer pipes of the low-temperature heating supply pipe 38 and the primary heating heat exchanger 13. A thermostatic valve 39 is arranged on the downstream side of the low-temperature heating supply pipe 38, branching the low-temperature heating supply pipe 38. The downstream end of the thermostatic valve 39 serves as the low-temperature heating outlet 77. The low-temperature heating outlet 77 is connected to the low-temperature radiator 34.

[0042] The outlet of the heat transfer pipes of the primary heating heat exchanger 13 is connected to the high-temperature heating supply pipe 40. The downstream end of the high-temperature heating supply pipe 40 serves as the high-temperature heating outlet 75 provided on the bottom plate 71B. The high-temperature heating outlet 75 is connected to the high-temperature radiator 33. A high-temperature heating thermostat 41 is provided on the high-temperature heating supply pipe 40. The high-temperature heating supply pipe 40 and the heating return pipe 32 are connected by a bath heating pipe 42. A supplementary boiling flow control valve 43 is provided on the bath heating pipe 42. A heating bypass pipe 44 that bypasses the primary and secondary heating heat exchangers 13 and 14 is connected between the upstream side of the heating tank 69 in the intermediate pipe 35 and the high-temperature heating supply pipe 40, and a bypass thermostatic valve 45 for controlling the bypass flow rate is provided on the heating bypass pipe 44.

[0043] Therefore, in the heating circuit B, the hot water heated by the secondary heating heat exchanger 14 circulates to the heating return pipe 32 via the intermediate pipe 35, the heating tank 69, the low-temperature heating supply pipe 38, and the low-temperature radiator 34, and flows into the primary heating heat exchanger 13 via the intermediate pipe 35. The hot water heated by the primary heating heat exchanger 13 returns to the heating return pipe 32 via the high-temperature heating supply pipe 40 and the high-temperature radiator 33, and circulates to the primary heating heat exchanger 13 via the secondary heating heat exchanger 14, the intermediate pipe 35, and the heating tank 69.

[0044] The bathtub circuit C is provided with a bathtub heat exchanger 46 into which a bathtub heating pipe 42 is inserted. The inlet of the bathtub heat exchanger 46 is connected to a bathtub return pipe 47 connected to the bathtub return port of the bottom plate 71B. The bathtub return port is connected to the bathtub 49 via an external bathtub return pipe 48. A bathtub circulation pump 50 is provided on the downstream side of the bathtub return pipe 47. A bathtub return thermistor 51 for detecting the bathtub return temperature is provided on the upstream side of the bathtub circulation pump 50. A water flow switch 52 and a water level sensor 53 are provided on the downstream side of the bathtub circulation pump 50. The outlet of the bathtub heat exchanger 46 is connected to a bathtub supply pipe 54 connected to the bathtub supply port of the bottom plate 71B. The bathtub supply port is connected to the bathtub 49 via an external bathtub supply pipe 55. A bathtub supply thermistor 56 for detecting the bathtub supply temperature is provided on the bathtub supply pipe 54.

[0045] A drop pipe 57 is connected between the downstream side of the bypass pipe 30 in the hot water supply pipe 27 and the upstream side of the bathtub circulation pump 50 in the bathtub return pipe 47. In this drop pipe 57, a drop water solenoid valve 58 for opening and closing the drop pipe 57 and a bathtub water volume sensor 59 for detecting the amount of water flowing through the drop pipe 57 are provided from the upstream side (hot water supply pipe 27 side), respectively. The drop pipe 57 enables the hot water heated in the hot water supply circuit A to be supplied to the bathtub 49. Three check valves 60, 60, 60 are provided on the downstream side of the bathtub water volume sensor 59. An edge cut valve 61 is connected between these check valves 60. This edge cut valve 61 is connected to a drain pipe 62 connected to an overflow discharge port provided on the bottom plate 71B and an introduction pipe 63 connected to the downstream side of the strainer 23 in the water supply pipe 22. When the internal pressure of the hot water in the drop pipe 57 increases due to the back pressure from the bathtub return pipe 47 and becomes greater than the back pressure from the introduction pipe 63, the edge cut valve 61 discharges the hot water flowing back from the drop pipe 57 to the overflow discharge port via the drain pipe 62. In this way, a bathtub circuit C for circulating the hot water in the bathtub 49 is formed by the bathtub heat exchanger 46, the bathtub supply pipe 54, the bathtub return pipe 47, and the like.

[0046] Inside the housing 70, a neutralizer 64 is provided for neutralizing the drain generated by the hot water supply secondary heat exchanger 12 and the heating secondary heat exchanger 14. This neutralizer 64 is connected to a drain receiver 66 provided on the bottom surface of the exhaust hood 15 via a drain introduction pipe 65, and is also connected to the drain pipe 62 of the edge cut valve 61 via a drain discharge pipe 67. The neutralizer 64 is provided with a water level electrode 68 for detecting the water level.

[0047] Referring to FIG. 2, the control board 79 will be described. The control board 79 has a control unit and various electronic components mounted thereon. The control unit is, for example, a CPU, a microcomputer (so-called microcontroller), an FPGA (Field Programmable Gate Array), etc. The control board 79 receives detection signals from various thermistors, sensors, etc. and operates each valve, etc. to perform hot water temperature control, hot water filling control for the bathtub 49, temperature control related to heating, etc. Although not shown, the hot water supply and heating machine 1 is provided with a remote control or the like that is communicably connected to the control board 79.

[0048] (2) Control of the bypass valve after the combustion of the hot water supply combustion unit has stopped Referring to FIG. 4, the control of the bypass valve 31 after the combustion of the hot water supply combustion unit 4A has stopped will be described. In FIG. 4, ON indicates combustion and OFF indicates combustion stop. The example shown in FIG. 4 shows the case where the combustion of the hot water supply combustion unit 4A stops when both the heating combustion unit 5A and the hot water supply combustion unit 4A are burning.

[0049] In FIG. 4, the dashed-dotted line 90 indicates the control of the conventional bypass valve 31. In the conventional control, when the combustion of the hot water supply combustion unit 4A stops, the control board 79 increases the opening degree of the bypass valve to a certain extent. The reason for increasing the opening degree of the bypass valve 31 is to suppress high-temperature hot water discharge by mixing the water from the bypass pipe 30 into the hot water in the hot water primary heat exchanger 11 that has become high in temperature due to after-boiling when the combustion of the hot water supply combustion unit 4A restarts (in other words, when the next hot water supply operation starts). The opening degree of the bypass valve 31 immediately after the combustion of the hot water supply combustion unit 4A stops is preferably an opening degree at which hot water at the target temperature or a temperature close thereto is discharged even if the combustion of the hot water supply combustion unit 4A restarts immediately after the combustion of the hot water supply combustion unit 4A stops. Such an opening degree can be determined in advance through experiments.

[0050] Then, the control board 79 continuously increases the opening degree of the bypass valve 31 until 10 seconds (an example of the first specified time) elapses. The control board 79 may increase the opening degree of the bypass valve 31 step by step. The reason for increasing the opening degree of the bypass valve 31 is to suppress high-temperature hot water discharge by increasing the opening degree of the bypass valve 31 in accordance with the increase in the temperature of the hot water in the hot water primary heat exchanger 11 due to after-boiling. The first specified time is preferably the time when the temperature of the hot water in the hot water primary heat exchanger 11 becomes the highest or a time close thereto due to after-boiling after the combustion of the hot water supply combustion unit 4A stops. Such a time can be determined in advance through experiments.

[0051] Then, when 10 seconds elapse, the control board 79 continuously decreases the opening degree of the bypass valve. The control board 79 may decrease the opening degree of the bypass valve 31 step by step. The reason for decreasing the opening degree of the bypass valve 31 is that as time elapses after the combustion of the hot water supply combustion unit 4A stops, the temperature of the hot water in the hot water primary heat exchanger 11 decreases. If the opening degree of the bypass valve 31 is large, there is a possibility that when the next hot water supply operation starts, the water from the bypass pipe 30 will be mixed more than necessary, resulting in low-temperature hot water discharge.

[0052] The solid line 91 indicates the control of the bypass valve 31 according to Embodiment 1. In addition to the conventional control described above, when the combustion fan 10 rotates after the combustion of the hot water combustion unit 4A stops, the control board 79 performs control to reduce the opening degree of the bypass valve 31 compared to the case where the combustion fan 10 does not rotate. Here, the change in the opening degree of the bypass valve 31 when the combustion fan 10 does not rotate after the combustion of the hot water combustion unit 4A stops is the same as the change in the case of performing only the conventional control (that is, the change indicated by the dashed-dotted line 90).

[0053] The control board 79 does not immediately reduce the opening degree of the bypass valve 31 even when the combustion fan 10 rotates after the combustion of the hot water combustion unit 4A stops, and reduces the opening degree of the bypass valve 31 when the cumulative rotation time of the combustion fan 10 from the time when the hot water combustion unit 4A stops combustion reaches a second specified time (150 seconds in FIG. 4). In the case of the example shown in FIG. 4, since the heating combustion unit 5A is burning even when the hot water combustion unit 4A stops combustion, the combustion fan 10 continues to rotate. In this case, the time point T1 when the combustion of the hot water combustion unit 4A stops becomes the starting point for counting the cumulative rotation time of the combustion fan 10.

[0054] As shown in Table 1 below, the control board 79 varies the second specified time according to the inlet water temperature. The inlet water temperature is the temperature of the water supplied from the water inlet and is detected by the hot water inlet thermistor 25.

Table 1

[0055] For example, when the inlet water temperature is 15°C or less, the control board 79 sets the second specified time to 150 seconds. Further, when the inlet water temperature is 15°C or less, the control board 79 gradually reduces the opening degree of the bypass valve 31 when the cumulative rotation time of the combustion fan 10 reaches the second specified time. Specifically, when the cumulative rotation time of the combustion fan 10 reaches 150 seconds (time point T2 shown in FIG. 4), the control board 79 closes the bypass motor (stepping motor) that drives the bypass valve 31 by 200 steps. 200 steps corresponds to approximately 10% of the opening degree. Assuming the current opening degree is 100%, the opening degree of the bypass valve 31 after closing by 200 steps is approximately 90%.

[0056] Then, when the cumulative rotation time of the combustion fan 10 reaches 180 seconds, the control board 79 fully closes the bypass valve 31. Here, in this embodiment, fully closed does not necessarily mean that the opening degree is 0%. For example, there may be a case where the bypass valve 31 is always controlled to be open by 5% or more. In that case, the state where the opening degree of the bypass valve 31 is 5% is considered fully closed. The maximum standby position shown in Table 1 is the position of the bypass valve 31 when it is fully closed. By applying the pulse of the difference between the current position (current number of steps) of the bypass valve 31 and the maximum standby position to the bypass motor, the bypass valve 31 is fully closed.

[0057] As shown in Table 1, when the inlet water temperature is greater than 15°C and less than or equal to 20°C, the second specified time is set to 180 seconds. When the inlet water temperature is greater than 20°C and less than or equal to 22.5°C, the second specified time is set to 210 seconds. As shown in Table 1, when the inlet water temperature is greater than 15°C and less than or equal to 20°C, and when it is greater than 20°C and less than or equal to 22.5°C, when the cumulative rotation time of the combustion fan 10 reaches the second specified time, the bypass valve 31 is immediately fully closed.

[0058] In FIG. 4, time point T3 indicates the time when the combustion of the hot water supply combustion unit 4A resumes, in other words, when the hot water supply resumes. It is assumed that time point T3 is a time point when 180 seconds or more have elapsed since the combustion of the hot water supply combustion unit 4A stopped (time point T1). Therefore, the opening degree of the bypass valve 31 at time point T3 is fully closed. For example, if the user sets the set temperature (target temperature) of the hot and cold water to 32°C. In this case, the control board 79 heats the hot and cold water to, for example, 50°C for dew prevention and mixes the water from the bypass pipe 30 to make it 32°C. Since it cannot drop to 32°C with the opening degree remaining at 5%, the control board 79 opens the bypass valve 31 to lower the temperature of the heated hot and cold water.

[0059] However, when the control board 79 starts the combustion of the hot water supply combustion unit 4A after the elapse of the second specified time, it does not open the bypass valve 31 immediately even if the combustion is started, and maintains the current opening degree of the bypass valve 31 (in other words, the opening degree of the bypass valve 31 immediately before the hot water supply combustion unit 4A starts combustion) until the inner cylinder temperature reaches a predetermined temperature. The inner cylinder temperature refers to the temperature of the hot water on the downstream side of the hot water supply primary heat exchanger 11 and on the upstream side of the confluence position with the bypass pipe 30 in the hot water outlet pipe 27. The inner cylinder temperature is detected by the hot water supply heat exchanger thermistor 28. The predetermined temperature may be higher than the set temperature (target temperature). Even if the predetermined temperature is higher than the set temperature, the hot water outlet temperature can be lowered to the set temperature by mixing the water from the bypass pipe 30. In FIG. 4, the time point T4 is the time point when the inner cylinder temperature reaches the predetermined temperature. Therefore, the control board 79 opens the bypass valve 31 at the time point T4.

[0060] Furthermore, when the control board 79 starts the combustion of the hot water supply combustion unit 4A after the elapse of the second specified time, it increases the gas input amount to the hot water supply burner 6A to be more than the normal gas input amount until a certain time elapses after the start of the combustion. The normal gas input amount refers to the gas input amount when the hot water at the set temperature (target temperature) is discharged. The above-mentioned certain time may vary depending on the flow rate of the discharged hot water. For example, the control board 79 may set it to 1.3 seconds in the case of a small flow rate (5 L / min or less), 2.3 seconds in the case of a large flow rate (11 L / min or more), and a time proportional to the flow rate (for example, 1.8 seconds for 8 L / min) in between. Or, it may be set to the normal gas input amount when the hot water outlet temperature reaches the target temperature. For example, when the flow rate is 12 L / min and the target temperature is reached in 1.5 seconds, it may be set to the normal gas input amount at that time point (in other words, before the above-mentioned 2.3 seconds elapses).

[0061] In the description so far, the case where the combustion of the hot water supply combustion unit 4A stops when both the heating combustion unit 5A and the hot water supply combustion unit 4A are burning has been described as an example. On the other hand, when the heating combustion unit 5A is not burning and only the hot water supply combustion unit 4A is burning, the combustion of the hot water supply combustion unit 4A may stop. In this case, since both the heating combustion unit 5A and the hot water supply combustion unit 4A have stopped burning, the combustion fan 10 stops rotating when the combustion of the hot water supply combustion unit 4A stops. Then, when the combustion of the heating combustion unit 5A is started thereafter, the combustion fan 10 resumes rotation at that time. In this case, the point in time when the combustion of the heating combustion unit 5A is started and the combustion fan 10 resumes rotation becomes the starting point for counting the cumulative rotation time of the combustion fan 10.

[0062] It may also be controlled such that only the combustion fan 10 rotates when both the hot water supply combustion unit 4A and the heating combustion unit 5A have stopped burning. In that case, the time during which only the combustion fan 10 is rotating is also counted as the cumulative rotation time of the combustion fan 10. After the hot water supply combustion unit 4A stops burning, the combustion fan 10 may not start rotating even after, for example, 300 seconds have elapsed. Since the control board 79 also performs conventional control, when the combustion fan 10 does not start rotating even after 300 seconds have elapsed, the opening degree of the bypass valve 31 until 300 seconds have elapsed is the opening degree indicated by the dashed-dotted line 90. The opening degree when the combustion fan 10 does not rotate after the combustion of the hot water supply combustion unit 4A stops can be grasped by detecting the change in the opening degree of the bypass valve 31 without starting the combustion of the heating combustion unit 5A after stopping the combustion of the hot water supply combustion unit 4A.

[0063] (3) Effects of the Embodiment With reference to FIG. 5, the effects of the hot water supply and heating machine 1 according to Embodiment 1 will be described. The time point T3 shown in FIG. 5 is the same time point as the time point T3 shown in FIG. 4. That is, the time point T3 is the time point when the hot water supply combustion unit 4A starts burning. The solid line 92 shown in FIG. 5 indicates the change in the temperature of the hot water discharged by the hot water supply and heating machine 1, and the dashed-dotted line 93 indicates the change in the temperature of the hot water in the case of performing only conventional control. Here, it is assumed that the set temperature (target temperature) of the hot water is 40°C.

[0064] When only performing conventional control, even if the combustion fan 10 rotates after the combustion of the hot water supply combustion unit 4A stops, the opening degree of the bypass valve 31 does not decrease. Therefore, when the combustion of the hot water supply combustion unit 4A resumes thereafter, there is a possibility of low-temperature hot water discharge due to the water from the bypass pipe 30 mixing more than necessary with the hot and cold water in the hot water supply primary heat exchanger 11 cooled by the air blown from the combustion fan 10. On the other hand, according to the hot water supply and heating apparatus 1, when the combustion fan 10 rotates after the combustion of the hot water supply combustion unit 4A stops, the opening degree of the bypass valve 31 is made smaller than when the combustion fan 10 does not rotate. Therefore, even if the combustion fan 10 rotates, low-temperature hot water discharge can be suppressed. Furthermore, according to the hot water supply and heating apparatus 1, since low-temperature hot water discharge can be suppressed even if the combustion fan 10 rotates, it is not necessary to prohibit the combustion of the heating combustion unit 5A when the hot water supply combustion unit 4A is stopped. For this reason, the usability of the heating combustion unit 5A is not impaired. Therefore, according to the hot water supply and heating apparatus 1, low-temperature hot water discharge of the hot water supply combustion unit 4A can be suppressed without impairing the usability of the heating combustion unit 5A.

[0065] According to the hot water supply and heating apparatus 1, when the combustion of the hot water supply combustion unit 4A stops, the opening degree of the bypass valve 31 is continuously increased until 10 seconds (the first specified time) elapses. Therefore, the opening degree of the bypass valve 31 can be increased in accordance with the increase in the temperature of the hot and cold water in the hot water supply primary heat exchanger 11 due to after-boiling. Thereby, high-temperature hot water discharge can be suppressed. And according to the hot water supply and heating apparatus 1, when the first specified time elapses, the opening degree of the bypass valve 31 is continuously decreased, so that low-temperature hot water discharge can be suppressed.

[0066] According to the hot water supply and heating apparatus 1, even if the combustion fan 10 rotates after the combustion of the hot water supply combustion unit 4A stops, the opening degree of the bypass valve 31 is not decreased until the cumulative rotation time of the combustion fan 10 from the time when the combustion of the hot water supply combustion unit 4A stops reaches the second specified time. Therefore, high-temperature hot water discharge can be suppressed as compared with the case where the opening degree of the bypass valve 31 is decreased immediately when the combustion fan 10 starts rotating. On the other hand, when the cumulative rotation time reaches the second specified time, the opening degree of the bypass valve 31 is decreased, so that low-temperature hot water discharge can be suppressed.

[0067] According to the hot water supply and heating unit 1, when the inlet water temperature is 15°C or lower, the amount of water mixed into the hot water in the primary hot water exchanger 11 of the hot water supply gradually decreases over time. Therefore, when combustion starts immediately after the elapse of the second specified time, the difference between the temperature of the hot water discharged and the temperature of the hot water discharged when combustion starts after a certain time has elapsed since the elapse of the second specified time can be reduced. That is, the temperature of the hot water discharged after the elapse of the second specified time can be made substantially the same.

[0068] According to the hot water supply and heating unit 1, when starting the combustion of the hot water supply combustion unit 4A after the elapse of the second specified time, the gas input amount is made larger than the normal gas input amount until a certain time has elapsed since the start of combustion, so the heating amount can be increased. Thereby, the set temperature (target temperature) can be reached quickly.

[0069] According to the hot water supply and heating unit 1, when starting the combustion of the hot water supply combustion unit 4A after the elapse of the second specified time, the opening degree of the bypass valve 31 immediately before starting the combustion is maintained until the inner cylinder temperature reaches a predetermined temperature, so the amount of water mixed into the hot water can be reduced. Thereby, the set temperature (target temperature) can be reached quickly.

[0070] According to the hot water supply and heating unit 1, since the second specified time is varied according to the inlet water temperature detected by the hot water supply inlet water thermistor 25, low-temperature hot water discharge and high-temperature hot water discharge can be suppressed. As a modification, in the case of the hot water supply and heating unit 1 capable of measuring the air supply temperature, by varying the second specified time according to the inlet water temperature and the air supply temperature, low-temperature hot water discharge and high-temperature hot water discharge can be more reliably suppressed.

[0071] <Embodiment 2> The hot water supply combustion unit 4A can adjust the heating power by switching the number (number of stages) of the hot water supply burners 6A to be burned. As shown in Table 2 below, the control board 79 according to Embodiment 2 varies the second specified time according to the number of stages of the hot water supply burner 6A that was burning immediately before the hot water supply combustion unit 4A stopped combustion. One stage indicates that the number of hot water supply burners 6A burning is one, and two stages indicates that the number is two.

Table 2

[0072] In the example shown in Table 2, the longer the number of stages that were burning immediately before, the longer the second specified time. This is because the higher the temperature of the hot water in the hot water primary heat exchanger 11 as the number of burning stages increases, so as to suppress high-temperature hot water discharge, the timing of closing the bypass valve 31 is delayed to lengthen the time for water to mix.

[0073] According to the hot water supply and heating machine 1 according to Embodiment 2, since the second specified time is varied according to the number of stages of the hot water supply burner 6A that was burning immediately before the hot water supply combustion unit 4A stops combustion, regardless of the number of stages of the hot water supply burner 6A that was burning immediately before the hot water supply combustion unit 4A stops combustion, the temperature of the hot water discharged after the second specified time has elapsed can be made substantially the same.

[0074] <Other Embodiments> (1) In the above embodiment, the hot water supply combustion unit 4A is exemplified as one of the combustion units. However, the heating combustion unit 5A may be one of the combustion units, and the hot water supply combustion unit 4A may be the other combustion unit. In the above embodiment, the case where the heating combustion unit 5A includes the heating circuit B and the bath circuit C is exemplified. However, the heating combustion unit 5A may not include the heating circuit B and may include only the bath circuit C.

[0075] (2) In the above embodiment, the case where the opening degree of the bypass valve 31 is not reduced until the cumulative rotation time of the combustion fan 10 reaches the second specified time is exemplified. That is, in the above embodiment, the case where the opening degree of the bypass valve 31 is reduced after waiting until the cumulative rotation time of the combustion fan 10 reaches the second specified time is exemplified. In contrast, for example, the opening degree of the bypass valve 31 may be immediately reduced by 10% as soon as the combustion fan 10 starts rotating after the hot water supply combustion unit 4A stops combustion, without waiting for the second specified time to elapse.

[0076] (3) In the above embodiment, the case where the opening degree of the bypass valve 31 is gradually reduced when the inlet water temperature is 15°C or lower was described as an example. In contrast, when the inlet water temperature is 15°C or lower, it may be fully closed immediately when the second specified time is reached.

[0077] (4) In the above embodiment, the conventional control is also performed, but the conventional control may not be performed.

[0078] (5) In the above embodiment, the case where the opening degree of the bypass valve 31 is reduced when the combustion fan 10 rotates even when the inlet water temperature is 22.5°C or higher was exemplified. In contrast, when the inlet water temperature is 22.5°C or higher, the opening degree of the bypass valve 31 may not be reduced even when the combustion fan 10 rotates. This is because when the inlet water temperature is 22.5°C or higher, it is difficult for the temperature of the heat exchanger to decrease, and thus it is difficult for low-temperature hot water supply to occur even without performing the control of the above embodiment. 22.5°C is an example, and it can be appropriately determined at what temperature or higher the opening degree of the bypass valve 31 should not be reduced.

Explanation of Reference Numerals

[0079] 1: Hot water supply and heating machine (an example of a hot water supply device) 4A: Hot water supply combustion unit (an example of a combustion unit and one of the combustion units) 5A: Heating combustion unit (an example of a combustion unit) 6: Gas burner 10: Combustion fan 11: Primary hot water supply heat exchanger (an example of a heat exchanger) 12: Secondary hot water supply heat exchanger (an example of a heat exchanger) 13: Primary heating heat exchanger (an example of a heat exchanger) 14: Secondary heating heat exchanger (an example of a heat exchanger) 22: Water supply pipe 25: Inlet hot water supply thermistor (an example of a second temperature sensor) 27: Hot water supply pipe 28: Hot water supply heat exchanger thermistor (an example of a first temperature sensor) 30: Bypass pipe 31: Bypass valve 79: Control board (an example of a controller)

Claims

1. A water heater, comprising two combustion parts having a gas burner and a heat exchanger for heating water by the combustion heat of the gas burner, one combustion fan shared by the two combustion parts, and a controller, wherein one of the combustion parts has a water supply pipe for supplying water supplied from a water inlet to the heat exchanger, a hot water outlet pipe for discharging hot water heated by the heat exchanger from a hot water outlet, a bypass pipe connected to the water supply pipe and the hot water outlet pipe and short - circuiting the water inlet and the hot water outlet without passing through the heat exchanger, and a bypass valve for opening and closing the bypass pipe, wherein when the combustion fan rotates after the combustion of one of the combustion parts stops, the controller reduces the opening degree of the bypass valve compared to the case where the combustion fan does not rotate. A water heater.

2. The water heater according to Claim 1, wherein when the combustion of one of the combustion parts stops, the controller gradually or continuously increases the opening degree of the bypass valve until a first specified time elapses, and gradually or continuously reduces the opening degree of the bypass valve when the first specified time elapses. A water heater.

3. The water heater according to Claim 1 or Claim 2, wherein when the cumulative rotation time of the combustion fan from the time when the combustion of one of the combustion parts stops reaches a second specified time, the controller reduces the opening degree of the bypass valve. A water heater.

4. The water heater according to Claim 3, wherein when the cumulative rotation time reaches the second specified time and the controller reduces the opening degree of the bypass valve, the controller reduces the opening degree of the bypass valve step by step. A water heater.

5. The water heater according to Claim 3, wherein one of the combustion parts has a plurality of the gas burners and the number of the gas burners to be combusted can be switched, and the controller varies the second specified time according to the number of the gas burners that were burning immediately before one of the combustion parts stops combustion. A water heater.

6. The water heater according to Claim 3, when the gas input amount for discharging hot water at a target temperature is defined as a normal gas input amount, if the controller starts the combustion of one of the combustion parts after the second specified time has elapsed, the controller increases the gas input amount to the gas burner to be more than the normal gas input amount until a certain time elapses from the start of the combustion. A water heater.

7. The water heater according to claim 3, comprising a first temperature sensor that detects the temperature of the hot water on the downstream side of the heat exchanger and on the upstream side of the confluence position with the bypass pipe in the hot water outlet pipe, wherein when the controller starts the combustion of the one combustion unit after the elapse of the second specified time, the controller maintains the opening degree of the bypass valve immediately before the start of the combustion until the temperature detected by the first temperature sensor reaches a predetermined temperature. The water heater.

8. The water heater according to claim 3, comprising a second temperature sensor that detects the temperature of the water supplied from the water inlet, wherein the controller varies the second specified time according to the temperature of the water detected by the second temperature sensor. The water heater.

Images