Water heating system

Abstract

To provide a water heating system suppressed in generation of dew condensation of a can body, and widening a range of temperature adjustment of a heating medium.SOLUTION: Processing to be executed by a controller of a hot water system includes: a step (S310) of detecting a combustion demand based on an order given to the hot water system; a step (S320) of confirming an operational state of the hot water system 100; a step (S330) of determining whether or not possibility of dew condensation exists; a step (S340) of raising a lower limit of a supply amount of gas per unit burner when determining possibility of dew condensation (YES in the step S330); a step (S350) of lowering a lower limit of a supply amount of gas per unit burner to the limit when determining no possibility of dew condensation (NO in the step S330); a step (S360) of executing combustion; and a step (S370) of determining whether or not a termination condition of combustion is established.SELECTED DRAWING: Figure 3

Description

[Technical field]

[0001] The present disclosure relates to a hot water apparatus, and more particularly to a technique for suppressing the occurrence of condensation in a hot water apparatus. [Background technology]

[0002] Condensation may occur in hot water heaters and other hot water devices, and it is necessary to prevent the occurrence of condensation. For example, Japanese Patent Application Laid-Open No. 2010-117100 (Patent Document 1) discloses "a latent heat recovery type heat source device capable of effectively preventing condensation in the exhaust pipe without decreasing thermal efficiency as much as possible" (see [Abstract]). Furthermore, Japanese Patent Application Laid-Open No. 6281357 (Patent Document 2) discloses "a hot water heater capable of preventing condensation without causing a deterioration in combustion efficiency and while maintaining the hot water supply temperature" (see paragraph 0005). [Prior art documents] [Patent documents]

[0003] [Patent Document 1] JP 2010-117100 A [Patent Document 2] Patent No. 6281357 Summary of the Invention [Problem to be solved by the invention]

[0004] When a water heater burns gas to raise the temperature of the water, if the amount of gas input per burner in the combustion mechanism is too small, the exhaust gas temperature will drop, and the dew point temperature of the exhaust gas will also drop. This can cause condensation to form in the heat exchanger, which can lead to equipment failure. On the other hand, if the amount of gas input per burner is increased to prevent condensation from forming in the water heater body, the temperature of the water heater body will be maintained at a high temperature, which can narrow the range of temperatures of the hot water dispensed. Therefore, there is a need for technology that can suppress the occurrence of condensation without narrowing the range of hot water temperatures.

[0005] The present disclosure has been made in consideration of the above-described background, and one of the objectives in one aspect is to provide a hot water device that suppresses the occurrence of condensation without narrowing the range of hot and cold water temperatures. [Means for solving the problem]

[0006] According to one embodiment, a hot water device is provided. The hot water device includes a plurality of combustion tubes, a heat exchanger, a flow sensor for measuring the amount of hot water flowing through the hot water device, and a control device for controlling the operation of the hot water device. When combustion is performed under conditions that minimize the number of combustion tubes performing combustion, and when the target hot water outlet temperature of the heat exchanger is lower than a predetermined temperature and the amount of hot water is equal to or greater than a predetermined amount, the control device changes the minimum amount of gas to be combusted in the plurality of combustion tubes to a second value that is a predetermined amount greater than a first predetermined value.

[0007] In one aspect, when the target hot water outlet temperature of the heat exchanger is set to a predetermined temperature or higher, or the amount of hot water becomes less than a predetermined amount, the control device further changes the minimum amount of gas to be combusted in the multiple combustion tubes from a second value to a first value.

[0008] In one aspect, the control device can control the plurality of combustion tubes to perform intermittent combustion at a predetermined first value. When the control device has changed the minimum amount of gas burned in the plurality of combustion tubes to a second value, the control device further changes the hot water supply capacity at which intermittent combustion begins to a second hot water supply capacity that is greater than the predetermined first hot water supply capacity, and controls the combustion of the plurality of combustion tubes to perform intermittent combustion at the predetermined second value.

[0009] In one aspect, when the target hot water outlet temperature of the heat exchanger becomes higher than a predetermined temperature or the amount of hot water becomes less than a predetermined amount, the control device further changes the minimum amount of gas to be combusted in the multiple combustion tubes from a second value to a first value, and changes the hot water supply capacity at which intermittent combustion begins from the second hot water supply capacity to the first hot water supply capacity.

[0010] A hot water device according to another embodiment includes a boiler body having multiple combustion tubes, a heat exchanger, a flow sensor for measuring the amount of hot water flowing through the boiler body, and a control device for controlling the operation of the hot water device. When multiple combustion tubes are burning under conditions that minimize the number of combustion tubes performing combustion, and when the target temperature of the heat exchanger is lower than a predetermined temperature and the amount of water flowing through the boiler body is equal to or greater than a predetermined amount, the control device changes the minimum amount of gas to be combusted in the multiple combustion tubes to a second value that is a predetermined amount greater than the first predetermined value.

[0011] In one aspect, the occurrence of condensation is suppressed without narrowing the range of temperatures of hot and cold water supplied from a hot water device.

[0012] The above and other objects, features, aspects and advantages of the present invention will become apparent from the following detailed description of the invention taken in conjunction with the accompanying drawings. [Brief description of the drawings]

[0013] [Figure 1] 1 is a diagram showing an outline of the configuration of a hot water supply system 100. FIG. [Diagram 2] 2 is a block diagram showing a schematic control structure of a controller 300 included in the hot water supply system 100. FIG. [Diagram 3] 4 is a flowchart showing a part of a process executed by a controller 300 included in the hot water supply system 100. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0014] Hereinafter, an embodiment of the present invention will be described with reference to the drawings. In the following description, the same components are denoted by the same reference numerals. Their names and functions are also the same. Therefore, detailed description thereof will not be repeated.

[0015] The configuration of hot water supply system 100 will be described with reference to FIG. 1. FIG. 1 is a diagram showing an outline of the configuration of hot water supply system 100. Hot water supply system 100 includes hot water supply circuit 101, reheating circuit 102, heating circuit 103, and controller 300. Hot water supply circuit 101 is configured to supply hot water when a hot water tap such as a faucet 105 or a shower (not shown) is opened. Reheating circuit 102 is configured to heat and circulate hot water in a bathtub (not shown). Heating circuit 103 is configured to circulate and supply hot water, which is a liquid heat medium, to a heating device exemplified in FIG. 2. Controller 300 is configured, for example, by a microcomputer.

[0016] The reheating circuit 102 is configured to form a reheating circulation path for heating and circulating the hot water in the bathtub between the bathtub water inlet 191 and the bathtub water outlet 192. The bathtub water inlet 191 and the bathtub water outlet 192 are each connected via piping to an opening provided in a bathtub adapter (not shown) placed in the bathtub. A heating device that receives a heat medium from the heating circuit 103 is connected between the heating return port 302 and the heating output port (low temperature) 304, or between the heating return port 302 and the heating output port (high temperature) 306.

[0017] The hot water supply circuit 101 includes a primary heat exchanger 11a, a secondary heat exchanger 21a, and a plurality of combustion burners 30a housed in a boiler body 10. The hot water supply circuit 101 further includes a water inlet pipe 50, a bypass pipe 60, and a hot water outlet pipe .

[0018] Tap water or the like is supplied to the water inlet pipe 50. A bypass pipe 60 is arranged between the water inlet pipe 50 and the hot water outlet pipe 70. A distribution valve 80 is interposed and connected to the water inlet pipe 50 to control the diversion to the bypass pipe 60. A portion of the water supply is diverted from the water inlet pipe 50 to the bypass pipe 60 depending on the opening degree of the distribution valve 80. Furthermore, a temperature sensor 110 and a flow rate sensor 150 are arranged in the water inlet pipe 50. The temperature sensor 110 detects the inlet water temperature. The flow rate sensor 150 is arranged downstream of the distribution valve 80 (on the boiler body side) and detects the flow rate passing through the boiler body 10 (boiler body flow rate).

[0019] The water in the water inlet pipe 50 is first preheated by the secondary heat exchanger 21a, and then is mainly heated in the primary heat exchanger 11a. The hot water heated to a preset temperature by the primary heat exchanger 11a and the secondary heat exchanger 21a is discharged from the hot water outlet pipe 70.

[0020] The hot water outlet pipe 70 is connected to the bypass pipe 60 at a junction 75. Therefore, the hot water supply system 100 supplies hot water at an appropriate temperature, which is a mixture of high-temperature water output from the boiler body 10 and low-temperature water from the bypass pipe 60, to a predetermined hot water supply point such as a hot water tap in a kitchen or bathroom, or a hot water supply circuit to a bathtub.

[0021] The hot water outlet pipe 70 is provided with a flow rate adjustment valve 90 and temperature sensors 120, 130. The temperature sensor 120 is disposed upstream (towards the boiler body) of the junction 75 where the hot water outlet pipe 70 meets the bypass pipe 60, and detects the hot water temperature output from the boiler body 10. The temperature sensor 130 is disposed downstream (on the hot water outlet side) of the junction 75, and detects the hot water outlet temperature Th after the water from the bypass pipe 60 is mixed. The flow rate adjustment valve 90 is provided to control the hot water outlet flow rate. The temperature sensors 110, 120, 130 are, for example, constituted by thermistors.

[0022] In the can body 10, a mixture of fuel gas and combustion air supplied by a blower fan 40 is output from the combustion burner 30a. The mixture is ignited by an ignition device (not shown), causing the fuel gas to burn and generating a flame. Combustion heat generated by the flame from the combustion burner 30a is provided to the primary heat exchanger 11a and the secondary heat exchanger 21a in the can body 10.

[0023] The primary heat exchanger 11a heats the inlet water by heat exchange using sensible heat (combustion heat) of the combustion gas from the combustion burner 30a. The secondary heat exchanger 21a heats the water flowing through it by using latent heat of the combustion exhaust gas from the combustion burner 30a. An exhaust path 15 for discharging the combustion exhaust gas after heat exchange is provided downstream of the combustion gas flow direction of the can body 10. In this way, in the can body 10, the primary heat exchanger 11a and the secondary heat exchanger 21a heat the water supplied from the water inlet pipe 50 by the amount of heat generated by combustion in the combustion burner 30a.

[0024] A main gas solenoid valve 32, a gas proportional valve 33, and capacity switching valves 35a to 35c are arranged in a gas supply pipe 31 to the combustion burner 30a. The main gas solenoid valve 32 has a function of turning on and off the supply of fuel gas to the combustion burner 30a. The gas flow rate in the gas supply pipe 31 is controlled according to the opening degree of the gas proportional valve 33. The capacity switching valves 35a to 35c are controlled to open and close in order to switch the number of burners (number of burner combustions) to which fuel gas is supplied among the multiple combustion burners 30a.

[0025] Next, a description will be given of the configuration related to hot water supply to the bathtub in the hot water supply system 100. In the following, hot water supply to the bathtub will be referred to as "pouring hot water," while hot water supply to a hot water tap other than the bathtub (such as the faucet 105) will be simply referred to as "hot water supply."

[0026] The hot water supply system 100 further comprises a hot water supply pipe 180 that branches off from the hot water outlet pipe 70 to supply hot water to a bathtub (not shown). The hot water supply pipe 180 branches off from the hot water outlet pipe 70 via a flow rate adjustment valve 90. Furthermore, a hot water supply solenoid valve 210 and a check valve 220 are interposed and connected to the hot water supply pipe 180. The hot water supply pipe 180 is connected at a junction 185 to the bath return piping 190, which will be described later.

[0027] By controlling the opening and closing of the hot water supply solenoid valve 210 by the controller 300, it is possible to control the formation / cut-off of a path for pouring hot water from the hot water supply circuit 101 to the bathtub.

[0028] The reheating circuit 102 includes a bath return pipe 190, a bath supply pipe 195, a reheating circulation pump 400, and a bath heat exchanger 410.

[0029] The bath return pipe 190 is provided between the bath water intake port 191 and the intake port of the reheating circulation pump 400. The discharge side of the reheating circulation pump 400 is connected to one end of the bath heat exchanger 410. The other end of the bath heat exchanger 410 is connected to the bath water outlet port 192 by the bath supply pipe 195.

[0030] During reheating operation, the reheating circulation pump 400 operates to draw hot water from the bathtub into the hot water supply system 100 through the bathtub water intake port 191. A reheating circulation path is then formed in which the drawn hot water passes through the bath return pipe 190, the reheating circulation pump 400, the bath heat exchanger 410, and the bath supply pipe 195, and is returned to the bathtub through the bathtub water outlet port 192. In the reheating circulation path, temperature sensors 374 and 372 are provided on the input and output sides of the bath heat exchanger 410, respectively.

[0031] During reheating operation, the thermal valve 330 of the heating circuit 103 is opened. This causes the heat medium heated in the heating circuit 103 (described later) to flow through the bath heat exchanger 410. As a result, the hot water in the reheating circulation path is heated by the bath heat exchanger 410, and the temperature of the hot water in the bathtub can be increased.

[0032] Furthermore, the bath return pipe 190 is connected to the hot water supply pipe 180 at the junction 185. As a result, when the hot water supply solenoid valve 210 is opened, hot water from the hot water supply circuit 101 is supplied to the junction 185 via the hot water supply pipe 180. Because the reheating circulation pump 400 is stopped during the hot water supply operation, the supplied hot water is supplied into the bathtub from both the bathtub water inlet 191 and the bathtub water outlet 192 via the bath return pipe 190 and the bath supply pipe 195, respectively.

[0033] 1 again, the heating circuit 103 includes a primary heat exchanger 11b, a secondary heat exchanger 21b, and a combustion burner 30b. The primary heat exchanger 11b, the secondary heat exchanger 21b, and the combustion burner 30b are housed in the boiler body 10 common to the primary heat exchanger 11a, the secondary heat exchanger 21a, and the combustion burner 30a of the hot water supply circuit.

[0034] The primary heat exchanger 11b heats the incoming water by heat exchange using the sensible heat (combustion heat) of the combustion gas from the combustion burner 30b. The secondary heat exchanger 21b heats the flowing water by heat exchange using the latent heat of the combustion exhaust gas from the combustion burner 30b. The number of burners (number of burners) to which fuel gas is supplied among the multiple combustion burners 30b is switched by controlling the opening and closing of the capacity switching valves 36a and 36b. Fuel gas is supplied to the combustion burner 30b via the gas supply pipe 31, the main gas solenoid valve 32, and the gas proportional valve 33, which are shared with the combustion burner 30a.

[0035] Furthermore, the heating circuit 103 includes a heating circulation pump 310, a heating expansion tank 320, a thermal valve 330, a bypass thermal valve 345, pipes 340, 350, 360, 370, 380, and 390, a terminal thermal valve 305, and temperature sensors 382 and 384. The opening and closing of each of the thermal valve 330 and the bypass thermal valve 345 is controlled according to commands from the controller 300.

[0036] One end of the piping 350 is connected to one end (inlet side) of the primary heat exchanger 11b. The other end of the piping 350 is connected to a plurality of heating output ports (low temperature) 304 via a plurality of terminal thermal valves 305. The piping 360 is disposed between the other end (outlet side) of the primary heat exchanger 11b and the piping 380. The piping 360 and 370 branch off on the same side (outlet side) of the primary heat exchanger 11b, and the piping 370 connects between the other end of the primary heat exchanger 11b and the heating output port 306 (high temperature).

[0037] Piping 380 connects between heating return port 302 and one end (inlet side) of secondary heat exchanger 21b. Piping 340 is connected between heating expansion tank 320 and pipe 370. One end of pipe 390 is connected to the other end (outlet side) of secondary heat exchanger 21b, and the other end of pipe 390 is connected to pipe 340 at connection point 395.

[0038] The intake port 311 of the heating circulation pump 310 is connected to the heating expansion tank 320. The discharge port 312 of the heating circulation pump 310 is connected to the branching portion 355 of the piping 350. The heating expansion tank 320 is connected to the intake port 311 of the heating circulation pump 310. The heating expansion tank 320 temporarily stores the heat medium circulating through the heating circuit 103. When the water level in the heating expansion tank 320 drops, water can be supplied from the piping 51 by opening the water supply valve 327. When the water level rises, the heat medium can be discharged from the overflow tank 328 to the drain plug 106 via the piping 325. In addition, drain (condensed water) generated inside the can body 10 is stored in a drain tank (not shown) and discharged to the outside after neutralization treatment.

[0039] A thermal valve 330 that is controlled to open and close in response to a command from the controller 300 is interposed and connected to the piping 360. When the thermal valve 330 is opened, the heat medium heated in the primary heat exchanger 11b is divided into a path that is output to the heating output port 306 (high temperature) by the piping 370 and a path that is circulated via the piping 360. Therefore, when the thermal valve 330 is opened, a path is further formed that circulates the heat medium output from the primary heat exchanger 11b to the secondary heat exchanger 21b via the bath heat exchanger 410, the junction 385, and the piping 380.

[0040] On the other hand, when the thermal valve 330 is in a closed state, the heat medium output from the primary heat exchanger 11b is supplied only to the pipe 370. The heat medium supplied to the pipe 370 is output to the heating output port (high temperature) 306 and the pipe 340.

[0041] A temperature sensor 384 is disposed on the output side of primary heat exchanger 11b for detecting the output temperature from heater body 10 in heating circuit 103, i.e., the heat medium temperature after heating (hereinafter also referred to as "high-temperature side heat medium temperature Twh"). Meanwhile, a temperature sensor 382 is disposed in heating expansion tank 320 for detecting the heat medium temperature in the tank (hereinafter also referred to as "low-temperature side heat medium temperature Twl"). The low-temperature side heat medium temperature Twl detected by temperature sensor 382 corresponds to the temperature of the heat medium supplied from heating outlet (low temperature) 304. The temperature sensors 382 and 384 are, for example, constituted by thermistors.

[0042] Controller 300 receives output signals (detection values) from each sensor and user operations, and generates control commands to each device to control the overall operation of hot water supply system 100. User operations include an operation on / off command and a hot water temperature setting command (Tr*) for hot water supply system 100. For example, user operations are input to a remote controller (not shown).

[0043] The control commands include, for example, opening / closing and opening degree commands for each valve, commands for the combustion burners 30a, 30b (combustion on / off and heat generation amount), and on / off commands for the heating circulation pump 310. The operation on / off commands include on / off commands for the hot water supply operation and hot water pouring operation by the hot water supply circuit 101, the reheating operation by the reheating circuit 102, and the heating operation by the heating circuit 103. Regarding the heating operation, the heating operation in the hot water supply system 100 may be automatically turned on in response to an on command for the high-temperature heating device 510 and the low-temperature heating device 610 (FIG. 2). It is preferable that the set hot water temperature (Tr*) is set separately for each of the hot water supply operation and the hot water pouring operation. In addition, in the heating operation, the set temperature is generally not directly input.

[0044] During hot water supply operation and hot water pouring operation, low-temperature water in the water inlet pipe 50 is heated by combustion in the combustion burner 30a of the hot water supply circuit 101 and output to the hot water outlet pipe 70. The controller 300 calculates the required amount of heat generation P* by the combustion burner 30a during hot water supply operation and hot water pouring operation. For example, the required amount of heat generation P* is calculated so that the detected value of the boiler body outlet temperature is controlled to a target value. The target value of the boiler body outlet temperature can be set based on the set temperatures during hot water supply operation and hot water pouring operation set by the user and the flow division ratio of the bypass pipe 60 (opening degree of the distribution valve 80).

[0045] During the reheating operation and the heating operation, the heat medium circulating through the circulation path formed by driving the heating circulation pump 310 is heated by combustion in the combustion burner 30b. The controller 300 calculates the heat generation amount P* required by the combustion burner 30b so that the detection value of the output temperature (high-temperature side heat medium temperature Twh) of the primary heat exchanger 11b detected by the temperature sensor 384 is controlled to a target value.

[0046] The controller 300 calculates the amount of gas supplied to the combustion burners 30a, 30b according to the calculated required heat generation amount P* in each of the hot water supply operation, hot water pouring operation, heating operation, and reheating operation. Furthermore, the controller 300 determines a combination of the number of burners to be burned and the gas flow rate among the combustion burners 30a, 30b that will realize this amount of gas supplied, and controls the aperture of the gas proportional valve 33 and the opening and closing of the capacity switching valves 35a-35c, 36a, 36b so that the determined number of burners to be burned and the gas flow rate are realized. Furthermore, the controller 300 controls the rotation speed of the blower fan 40 so that the ratio (air-fuel ratio) of the amount of air blown by the blower fan 40 to the calculated amount of gas supplied becomes a predetermined value (for example, the ideal air-fuel ratio).

[0047] In the hot water supply system 100, when the heating operation is on, the heating circulation pump 310 operates to circulate the heat medium (hot water) from the heating circuit 103 to the high-temperature heating device 510 and / or the low-temperature heating device 610 via the heating return port 302, and the heating output port (low temperature) 304 and / or the heating output port (high temperature) 306, via the "heating circulation path" described below.

[0048] By driving the heating circulation pump 310, a suction path is formed from the heating return port 302, via the piping 380, the secondary heat exchanger 21b, the piping 390, the connection point 395, the piping 340, and the heating expansion tank 320, to the suction port 311 of the heating circulation pump 310. The heat medium sucked from the heating expansion tank 320 into the heating circulation pump 310 is output from the discharge port 312 to the branching portion 355 of the piping 350.

[0049] The heat medium discharged from the heating circulation pump 310 is branched at a branching portion 355 of the piping 350 into an output path leading to the terminal thermal valve 305 and the heating output port (low temperature) 304, and a heating path passing through the primary heat exchanger 11b. The heating path includes an output path that outputs the heat medium from the heating output port (high temperature) 306 after passing through the primary heat exchanger 11b, and a return path that leads to the heating expansion tank 320 again via the piping 340 (bypass thermal valve 345) after passing through the primary heat exchanger 11b. As described above, the return path is formed even when the bypass thermal valve 345 is closed, but when the bypass thermal valve 345 is opened, the flow rate of the return path can be increased. For example, when the temperature of the heat medium is low immediately after the heating operation is turned on, the temperature of the heat medium can be quickly increased by opening the bypass thermal valve 345.

[0050] By forming the above-mentioned heating circulation path, high-temperature water that has passed through the primary heat exchanger 11b is supplied from the heating output port 306 (high temperature) to the high-temperature heating device 510. On the other hand, hot water in the heating expansion tank 320 is supplied from the heating output port 304 (low temperature) to the low-temperature heating device 610.

[0051] When the heating operation is off, the flow of the heat medium is stopped in each of the heating circuit 103, the high-temperature heating device 510, and the low-temperature heating device 610. Therefore, in a severe cold season or the like, if the heating operation is off for a long period of time, there is a concern that the heat medium will freeze. Therefore, in the heating circuit 103, when the heating operation is off, a freeze prevention operation is automatically performed in which the heat medium is circulated in the heating circuit 103 and the low-temperature heating device 610. For example, the freeze prevention operation is automatically started when a predetermined start condition is met using at least one of the heat medium temperatures Twh, Twl, the air temperature detected by an ambient temperature sensor (not shown), and the elapsed time since the circulation of the heat medium was stopped during the heating operation off period.

[0052] [Function configuration] The configuration of hot water supply system 100 will be further described with reference to Fig. 2. Fig. 2 is a block diagram that typically illustrates a control structure of a controller 300 provided in hot water supply system 100. Controller 300 receives an input from flow rate sensor 150. Controller 300 includes a condensation determination circuit 301, a combustion control circuit 303, and a memory 307.

[0053] The condensation determination circuit 301 determines the possibility of condensation. In one aspect, the condensation determination circuit 301 determines the possibility of condensation based on a comparison between a target hot water outlet temperature of a heat exchanger (for example, heat exchanger 11a) and a predetermined temperature. In another aspect, the condensation determination circuit 301 determines the possibility of condensation based on a comparison between a total flow rate and a specified flow rate.

[0054] The combustion control circuit 303 controls the combustion of the multiple combustion burners 30a. The memory 307 is realized by a non-volatile memory.

[0055] (1) In one aspect, when combustion is occurring under conditions that minimize the number of combustion tubes performing combustion, condensation determination circuit 301 determines whether the target hot water outlet temperature of the heat exchanger is lower than a predetermined temperature and the amount of hot water is equal to or greater than a predetermined amount. When condensation determination circuit 301 determines that the target hot water outlet temperature of the heat exchanger is lower than a predetermined temperature and the amount of hot water is equal to or greater than a predetermined amount, combustion control circuit 303 changes the minimum amount of gas to be combusted in the multiple combustion tubes to a second value that is a predetermined amount greater than a first predetermined value.

[0056] (2) At a certain stage, when the target outlet temperature of the heat exchanger is set to a predetermined temperature or higher, or the amount of hot and cold water becomes less than a predetermined amount, the combustion control circuit 303 further changes the minimum amount of gas to be combusted in the multiple combustion tubes from a second value to a first value.

[0057] (3) In one aspect, the combustion control circuit 303 can control the multiple combustion tubes to perform intermittent combustion at a predetermined first value. When the minimum amount of gas burned in the multiple combustion tubes is changed to a second value, the combustion control circuit 303 further changes the hot water supply capacity at which intermittent combustion begins to a second hot water supply capacity that is greater than the predetermined first hot water supply capacity, and controls the multiple combustion tubes to perform intermittent combustion at the predetermined second value.

[0058] (4) At a certain stage, when the target hot water outlet temperature of the heat exchanger is set to a predetermined temperature or higher, or the amount of hot water becomes less than a predetermined amount, the combustion control circuit 303 further changes the minimum amount of gas to be combusted in the multiple combustion tubes from a second value to a first value, and changes the hot water capacity at which intermittent combustion begins from the second hot water capacity to the first hot water capacity.

[0059] (5) In a certain aspect, when combustion is performed under conditions that minimize the number of combustion tubes performing combustion, the condensation determination circuit 301 determines whether the target temperature of the heat exchanger to discharge hot water is lower than a predetermined temperature and the amount of water flowing through the can body is equal to or greater than a predetermined amount. When the condensation determination circuit 301 determines that the target temperature of the heat exchanger to discharge hot water is lower than a predetermined temperature and the amount of water flowing through the can body is equal to or greater than a predetermined amount, the combustion control circuit 303 changes the minimum amount of gas to be combusted in the multiple combustion tubes to a second value that is larger than a first predetermined value.

[0060] [Control Structure] A control structure of hot water supply system 100 according to the present embodiment will be described with reference to Fig. 3. Fig. 3 is a flowchart showing a part of a process executed by controller 300 included in hot water supply system 100. In one aspect, the following process is realized by a computer executing a program including instructions for realizing each step. In another aspect, the process is also realized by a combination of circuit elements configured to realize each step.

[0061] In step S310, controller 300 detects a combustion request based on a command given to hot water supply system 100.

[0062] In step S320, controller 300 checks the operating state of hot water supply system 100. In one aspect, controller 300 compares the target outlet temperature of the heat exchanger with a specified temperature. In another aspect, controller 300 compares the total flow rate with a specified flow rate.

[0063] In step S330, controller 300, functioning as condensation determination circuit 301, determines whether or not condensation is likely. In a certain aspect, controller 300 determines whether or not the target outlet temperature of the heat exchanger is less than a specified temperature (e.g., 50°C) and the total flow rate is greater than or equal to a specified flow rate (e.g., 15 liters per minute). If controller 300 determines that condensation is likely (YES in step S330), it switches control to step S340. If not (NO in step S330), controller 300 switches control to step S350.

[0064] In step S340, controller 300, functioning as combustion control circuit 303, raises the lower limit of the amount of gas supplied per unit burner.

[0065] In step S350, controller 300, functioning as combustion control circuit 303, reduces the lower limit of the amount of gas supplied per unit burner to a predetermined limit value.

[0066] In step S360, the controller 300 performs combustion as the combustion control circuit 303. That is, the controller 300 performs normal combustion using the value set in step S340 or step S350 as the lower limit of the amount of gas supplied per unit burner, or performs intermittent combustion by switching the multiple combustion burners 30a on and off.

[0067] In step S370, controller 300 determines whether or not a condition for terminating combustion has been met. In the present embodiment, the condition for terminating combustion is, for example, that the amount of water flowing through hot water supply system 100 has fallen below the amount of water required for combustion, that a user (person taking a bath) has performed an operation to stop operation of hot water supply system 100, etc. If controller 300 determines that the condition for terminating combustion has been met (YES in step S370), it terminates combustion. If not (NO in step S370), controller 300 returns control to step S330 and continues operation (combustion) of hot water supply system 100.

[0068] This prevents condensation on the boiler body by raising the minimum gas supply only under conditions where condensation would occur on the boiler body. Also, when there is no risk of condensation on the boiler body, lowering the gas supply to the lower limit permitted by the burner makes it easier to adjust the temperature, and therefore expands the range of the tapping temperature.

[0069] In the above embodiment, the combustion is performed to supply hot water, but the application of the disclosed technical concept is not limited to the combustion for supplying hot water. For example, even when the combustion is performed for heating, the occurrence of condensation is suppressed and the range of temperature adjustment for heating can be expanded.

[0070] The embodiments disclosed herein should be considered to be illustrative and not restrictive in all respects. The scope of the present invention is defined by the claims, not the above description, and is intended to include all modifications within the meaning and scope of the claims. [Industrial Applicability]

[0071] The disclosed technical features are applicable to hot water supply systems. [Explanation of symbols]

[0072] 10 boiler body, 11a, 11b primary heat exchanger, 15 exhaust path, 21a, 21b secondary heat exchanger, 30a, 30b combustion burner, 31 gas supply pipe, 32 main gas solenoid valve, 33 gas proportional valve, 35a, 35c, 36a, 36b capacity switching valve, 40 blower fan, 50 water inlet pipe, 51, 190, 325, 340, 350, 360, 370, 380, 390 piping, 60 bypass pipe, 70 hot water outlet pipe, 75, 185, 385 junction, 80 distribution valve, 90 flow control valve, 100 hot water supply system, 101 hot water supply circuit, 102 reheating circuit, 103 heating circuit, 105 faucet, 106 Drain plug, 110, 120, 130, 374, 382, ​​384 Temperature sensor, 150 Flow sensor, 180 Hot water pipe, 191 Bath water inlet, 192 Bath water outlet, 195 Bath supply piping, 210 Hot water solenoid valve, 220 Check valve, 300 Controller, 301 Condensation determination circuit, 302 Heating return port, 303 Combustion control circuit, 304, 306 Heating output port, 305 Terminal thermal valve, 307 Memory, 310 Heating circulation pump, 311 Inlet, 312 Outlet, 320 Heating expansion tank, 327 Water supply valve, 328 Overflow tank, 330 Thermal valve, 345 Bypass thermal valve, 355 Branch, 395 Connection point, 400 Reheating circulation pump, 410 Bath heat exchanger, 510 High temperature heating equipment, 610 low temperature heating equipment.

Claims

1. A hot water device, comprising: A plurality of combustion tubes; A heat exchanger; A flow rate sensor for measuring the amount of hot water flowing through the hot water device; A control device for controlling the operation of the hot water device, A hot water device in which, when combustion is performed under conditions that minimize the number of combustion tubes performing combustion, when the target hot water outlet temperature of the heat exchanger is lower than a predetermined temperature and the amount of hot water is equal to or greater than a predetermined amount, the control device changes the minimum amount of gas to be combusted in the multiple combustion tubes to a second value that is a predetermined amount larger than the predetermined first value.

2. When the target temperature of the heat exchanger is set to a temperature equal to or higher than the predetermined temperature, or when the amount of hot and cold water is less than the predetermined amount, The hot water apparatus according to claim 1 , wherein the control device further changes a minimum value of an amount of gas combusted in the plurality of combustion tubes from the second value to the first value.

3. The control device is capable of controlling the combustion in the plurality of combustion tubes so as to perform intermittent combustion at the predetermined first value, When the control device changes the minimum amount of gas to be combusted in the plurality of combustion tubes to the second value, The hot water supply capacity at which the intermittent combustion is started is changed to a second hot water supply capacity that is greater than a predetermined first hot water supply capacity, The hot water device according to claim 1 , wherein the combustion of the plurality of combustion tubes is controlled so as to perform intermittent combustion at the predetermined second value.

4. When the target temperature of the heat exchanger is set to a temperature equal to or higher than the predetermined temperature, or when the amount of hot and cold water is less than the predetermined amount, The control device further comprises: changing a minimum value of the amount of gas combusted in the plurality of combustion tubes from the second value to the first value; The hot water apparatus according to claim 3 , wherein a hot water supply capacity at which the intermittent combustion is started is changed from the second hot water supply capacity to the first hot water supply capacity.

5. A hot water device, comprising: a can body having a plurality of combustion tubes; A heat exchanger; A flow rate sensor for measuring the amount of hot and cold water flowing through the boiler body; A control device for controlling the operation of the hot water device, A hot water supply system in which, when combustion is performed under conditions that minimize the number of combustion tubes, the target outlet temperature of the heat exchanger is lower than a predetermined temperature, and the amount of water flowing through the boiler body is equal to or greater than a predetermined amount, the control device changes the minimum amount of gas to be combusted in the multiple combustion tubes to a second value that is a predetermined amount greater than the predetermined first value.

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