JP7303428B2 - Water heater and hot water system - Google Patents

Description

The present invention relates to a hot water supply device and a hot water supply system.

Japanese Patent Application Laid-Open No. 2017-9215 (Patent Document 1) discloses an auxiliary heat source device that is configured to reheat hot water supplied from a hot water storage tank and discharge the hot water at a set temperature. In Patent Document 1, the auxiliary heat source device controls the mixing ratio of heated water (high-temperature water) that has passed through the heating unit and non-heated water (low-temperature water) that has passed through a bypass passage that bypasses the heating unit. It consists of a mixing-type water heater. The auxiliary heat source device includes inlet water temperature detection means for detecting the temperature of hot water flowing in the water inlet side passage, and outlet hot water temperature detection means for detecting the temperature of hot water flowing in the hot water outlet side passage on the upstream side of the junction of the bypass passage. The temperature detected by the detection means is used to control the start/stop of the heating operation.

JP 2017-9215 A

In conventional auxiliary heat source equipment, when the temperature of the hot water stored in the hot water storage tank is low, or when the piping from the hot water storage tank to the auxiliary heat source equipment is cold, the auxiliary heat source equipment is burned at the same time as hot water is supplied. Run a backup tap. After that, the temperature of water entering the auxiliary heat source machine is monitored, and when the combustion prohibition condition is satisfied, the combustion of the auxiliary heat source machine is stopped and the backup hot water supply is switched to the tank hot water supply.

However, in a configuration in which the temperature of incoming water detected by the incoming water temperature detection means is used to control the combustion of the auxiliary heat source equipment, as the temperature of the water entering the auxiliary heat source equipment rises and the temperature difference from the set temperature decreases, combustion is suppressed. Since it becomes difficult to control the outlet heated water temperature, an overshoot in which the outlet heated water temperature exceeds the set temperature may occur. Further, when the temperature difference between the temperature of water entering the auxiliary heat source device and the set temperature is small, the execution/stopping of combustion control will be repeated frequently, and there is concern that the temperature of discharged hot water will fluctuate.

Furthermore, in the conventional auxiliary heat source machine, combustion of the auxiliary heat source machine is not required while hot water is being discharged from the tank, so the auxiliary heat source machine can simply serve as water flow resistance in the hot water supply circuit. As a result, there is room for improvement in terms of energy saving.

SUMMARY OF THE INVENTION Accordingly, an object of the present invention is to provide a hot water supply apparatus and a hot water supply system capable of maintaining the outlet hot water temperature at a set temperature while realizing energy saving.

A hot water supply apparatus according to one aspect of the present invention includes a heat source, a heat exchanger that heats low-temperature water with heat from the heat source and outputs high-temperature water, and a heating flow that causes the low-temperature water to pass through the heat exchanger. a bypass channel that branches off from the heating channel upstream of the heat exchanger and joins the heating channel at a junction downstream of the heat exchanger; A flow ratio adjusting unit for controlling the ratio, and a control device for controlling the operation of the heat source unit and setting the operation amount of the flow ratio adjusting unit. When the temperature difference between the temperature of the low-temperature water and the set temperature of the outlet hot water is smaller than the first threshold value, the control device prohibits the operation of the heat source and sets the operation amount of the flow rate ratio adjustment unit to a predetermined value. Set to the maximum value of the controllable range of the flow ratio. When the temperature difference is greater than a second threshold that is greater than the first threshold, the control device permits the operation of the heat source unit and sets the operation amount of the flow rate ratio adjustment unit to a value smaller than the maximum value. set.

According to the present invention, it is possible to provide a hot water supply device and a hot water supply system capable of maintaining the outlet hot water temperature at the set temperature while realizing energy saving.

1 is a schematic configuration diagram of a hot water supply system according to an embodiment; FIG. FIG. 2 is an operation principle diagram of the auxiliary heat source machine shown in FIG. 1; It is a figure which shows the correspondence of the number of steps in a distribution valve, and a flow rate. FIG. 4 is a diagram for explaining hot water supply optimization processing executed in the auxiliary heat source machine; FIG. 4 is a schematic diagram for explaining estimation of temperature of water entering a primary heat exchanger; FIG. 5 is a diagram showing an example of calculation of an estimated incoming water temperature; 4 is a flowchart for explaining the procedure of hot water supply optimization processing executed in the auxiliary heat source machine;

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. In the following description, the same or corresponding parts in the drawings are denoted by the same reference numerals, and the description thereof will not be repeated in principle.

[Configuration of hot water supply system]
FIG. 1 is a schematic configuration diagram of a hot water supply system according to an embodiment.

Referring to FIG. 1 , hot water supply system 100 includes main heat source device 1 , tank unit 2 , and auxiliary heat source device 3 . The hot water supply system has hot water storage and hot water supply functions, as well as functions such as filling hot water into a bathtub (not shown), reheating the bathtub, and supplying heating water to a hot water heating terminal such as a floor heating panel.

The main heat source device 1 is configured to heat hot water in a hot water storage tank 21 of the tank unit 2 . The main heat source device 1 uses exhaust heat generated from, for example, a fuel cell as a heat source, and performs heat exchange between the exhaust heat and hot water supplied from the bottom of the hot water storage tank of the tank unit via the heat storage circulation path. As the heat source, other than the fuel cell, it is possible to use exhaust heat generated by the operation of a gas engine or the like, a heat pump, or solar heat collected by a heat collection panel.

The tank unit 2 has a hot water storage tank 21 , a heat storage circulation circuit 22 , a water supply circuit 23 , a hot water supply circuit 24 , a high temperature avoidance section 25 and a tank controller 5 .

The hot water storage tank 21 stores high-temperature hot water heated by the main heat source device 1 . The hot water storage tank 21 is a closed tank, and the periphery of the tank is covered with a heat insulating material. A plurality of remaining hot water sensors 211 are provided at a plurality of positions in the height direction, including at least the top position, on the outer peripheral portion of the hot water storage tank 21 . Each remaining hot water quantity sensor 211 is configured to detect the temperature of stored hot water at each height position.

The heat storage circulation circuit 22 is a closed circuit that circulates hot water between the hot water storage tank 21 and the main heat source device 1 to heat the hot water. The heat storage circulation circuit 22 has an upstream end connected to the bottom of the hot water tank 21 and a downstream end connected to the top of the hot water tank 21 . When a heat storage circulation pump (not shown) operates, the heat storage circulation circuit 22 extracts relatively low-temperature hot water from the hot water storage tank 21 from the bottom of the hot water storage tank 21, and performs heat exchange for exhaust heat recovery in the main heat source device 1. It is configured to return hot water heated by passing through a vessel (not shown) to the top of the hot water storage tank 21 . As a result, heat is stored as hot water at a predetermined temperature (for example, 65° C. or higher) while forming a temperature stratification in the hot water storage tank 21 .

The water supply circuit 23 supplies low-temperature water such as tap water from a water source to the hot water storage tank 21 and the like. The water supply circuit 23 branches into a main water supply pipe 231 and a mixing water supply pipe 232 . The main water supply pipe 231 is connected to the bottom of the hot water storage tank 21 at its downstream end. The main water supply pipe 231 is configured to supply tap water to the bottom of the hot water storage tank 21 as the hot water in the hot water storage tank 21 is output from the top. A downstream end of the mixing water supply pipe 232 is connected to the mixing section 27 via a flow control valve 233 so as to be able to supply water.

The hot water supply circuit 24 supplies hot water supplied from the hot water storage tank 21 to the hot water tap K. Specifically, hot water supply circuit 24 has hot water supply pipe 241 , flow control valve 242 , and mixing section 27 . The hot water supply pipe 241 has an upper end connected to the top of the hot water storage tank 21 and a downstream end connected to the connection port 201 of the tank unit 2 . Mixing section 27 is provided in the middle of hot water supply pipe 241 via flow control valve 242 . The mixing unit 27 is supplied from the upstream side of the hot water supply pipe 241 and the flow rate is adjusted via the flow rate adjustment valve 242, and the mixed water supply pipe 232 is supplied via the flow rate adjustment valve 233. is mixed with low-temperature water adjusted to a predetermined ratio. Control in the mixing section 27 is performed by the tank controller 5 . In the example of FIG. 1, the configuration in which hot water is mixed by the flow rate adjustment valves 242 and 233 provided on both sides of the mixing section 27 has been described. A configuration in which a mixing control valve is provided may be employed.

High temperature avoidance unit 25 avoids high temperature hot water discharge from hot water supply circuit 24 . The high temperature avoidance section 25 has a bypass pipe 251 and a high temperature avoidance valve 252 . The bypass pipe 251 connects the mixing water supply pipe 232 and the hot water supply pipe 241 on the downstream side of the mixing section 27 . The high temperature avoidance valve 252 opens and closes the bypass pipe 251 .

The auxiliary heat source machine 3 can function as a backup heat source for the tank unit 2 . As the auxiliary heat source device 3, a dedicated water heater or a water heater already installed in the house where the hot water supply system 100 shown in FIG. 1 is installed can be used. In the present embodiment, the auxiliary heat source device 3 is composed of a bypass mixing water heater.

The tank unit 2 and the auxiliary heat source machine 3 are installed apart (for example, about 1.5 m to 10 m). The connection port 201 of the tank unit 2 and the water inlet connection port 311 of the auxiliary heat source machine 3 are connected via a connection pipe 41 .

The auxiliary heat source device 3 is set to a combustion inhibited state when the hot water storage tank 21 of the tank unit 2 has a sufficient amount of high-temperature hot water. On the other hand, when the temperature of the hot water supplied from the tank unit 2 is low, the auxiliary heat source device 3 operates after the combustion inhibition state is cancelled, so that it can be supplementarily heated to the set temperature Tr*. FIG. 2 shows an operating principle diagram of the auxiliary heat source machine 3 shown in FIG. The configuration of the auxiliary heat source machine 3 will be described with reference to FIGS. 1 and 2. FIG.

[Configuration of auxiliary heat source machine]
The auxiliary heat source device 3 includes a water inlet connection port 311, a combustion can body 4 (hereinafter also simply referred to as “can body”) in which a heat exchanger 32, a combustion burner 33, etc. are stored, a blower fan 340, and a water inlet pipe 30. , boiler pipe 31 , bypass pipe 38 , hot water outlet pipe 34 , distribution valve 381 , and water heater controller 6 .

A downstream end of the connection pipe 41 is connected to the water inlet connection port 311 . Hot water from the tank unit 2 is supplied to the water inlet pipe 30 through the water inlet connection port 311 . Hot water in the water inlet pipe 30 is distributed to the boiler pipe 31 and the bypass pipe 38 via the distribution valve 381 .

The boiler pipe 31 is connected to the heat exchanger 32 . Heat exchanger 32 is configured to recover primarily the sensible heat of the combustion gases. The low-temperature water introduced from the water inlet pipe 30 into the boiler pipe 31 is heated by the amount of heat generated by the combustion burner 33 as it passes through the heat exchanger 32 . In the configuration example of FIG. 1, the heat exchanger 32 is provided downstream in the direction of flow of hot water, and a primary heat exchanger 32a that mainly recovers sensible heat of the combustion gas, and is provided upstream in the direction of flow of hot water. , and a secondary heat exchanger 32b for mainly recovering the latent heat of the combustion exhaust gas after sensible heat recovery. The heat exchanger 32 may be one having only the primary heat exchanger 32a.

A gas supply pipe 331 to the combustion burner 33 is provided with a source gas electromagnetic valve 332, a gas proportional valve 333 and capacity switching valves 335a to 335c. The source gas electromagnetic valve 332 has a function of turning on and off the supply of combustion gas to the combustion burner 33 . The gas flow rate of the gas supply pipe 331 is controlled according to the opening of the gas proportional valve 333 .

The capacity switching valves 335a to 335c are controlled to open/close in order to switch the number of burners among the combustion burners 33 to which the fuel gas is supplied. The amount of heat generated by the combustion burners 33 is proportional to the amount of combustion gas generated by the combustion burners 33 as a whole, which is determined by the combination of the number of burners to which fuel is supplied and which are subject to combustion, and the gas flow rate. Therefore, it is possible to prepare in advance a setting map for determining the combination of the opening/closing patterns (the number of combustion burners) of the capacity switching valves 335a to 335c and the opening degree (gas flow rate) of the gas proportional valve 333, corresponding to the required amount of generated heat. .

In the can body 4 , the fuel gas output from the combustion burner 33 is mixed with the combustion air from the blower fan 340 . The amount of air blown by the blower fan 340 is controlled so that the air-fuel ratio with the amount of gas supplied from the entire combustion burner 33 becomes a predetermined value (for example, the stoichiometric air-fuel ratio). The rotational speed of blower fan 340 is controlled according to a target rotational speed that is set according to changes in the amount of supplied gas. Blower fan 340 is provided with rotation speed sensor 345 for detecting the rotation speed.

A mixture of fuel gas and combustion air is ignited by an igniter (not shown) to burn the fuel gas and generate a flame. Combustion heat generated by the flame from the combustion burner 33 is given to the heat exchanger 32 in the can body 4 . Combustion burner 33 corresponds to an example of a "heat source".

The secondary heat exchanger 32b preheats the flowed low-temperature water by heat exchange with the latent heat of the flue gas from the combustion burner 33 . The primary heat exchanger 32 a further heats the low-temperature water preheated by the secondary heat exchanger 32 b by exchanging sensible heat (combustion heat) of the combustion gas from the combustion burner 33 . As a result, the hot water heated by the heat exchanger 32 is output to the hot water outlet pipe 34 . An exhaust passage 40 is provided on the downstream side of the can body 4 in the flow direction of the combustion gas for exhaust treatment of the combustion exhaust gas after heat exchange.

Bypass pipe 38 and tapping pipe 34 are connected at junction 39 . Therefore, from the auxiliary heat source machine 3, hot water at an appropriate temperature adjusted by mixing the high temperature water output from the boiler body 4 and the low temperature water from the bypass pipe 38 is supplied via the hot water supply pipe 42 to the hot water tap K. Alternatively, the hot water is supplied to a predetermined hot water supply point such as a hot water pouring circuit for a bath (not shown).

Distribution valve 381 controls the ratio of the flow rate of boiler pipe 31 and the flow rate of bypass pipe 38 by controlling the valve opening according to a control command from water heater controller 6 . For example, the flow ratio by the distribution valve 381 can be controlled by the number of steps X of a stepping motor that drives a valve body (not shown) to open and close. That is, the distribution valve 381 corresponds to an embodiment of the "flow rate ratio adjustment section", and the number of steps X of the distribution valve 381 corresponds to the "manipulated amount".

Below, using the ratio of the boiler body flow rate q1 (that is, the high temperature water flow rate) from the water inlet pipe 30 to the boiler body pipe 31 and the bypass flow rate q2 (that is, the low temperature water flow rate) from the water inlet pipe 30 to the bypass pipe 38 , the flow ratio k controlled by the distribution valve 381 is defined according to the following equation (1).

k=q2/q1 (1)
FIG. 3 shows the correspondence relationship between the number of steps X in the distribution valve 381 and the flow ratio k.

Referring to FIG. 3, in distribution valve 381, the flow ratio k (k=q2/q1) of the high temperature water and the low temperature water changes as the valve opening degree changes according to the number X of steps. The number of steps X is controlled by the water heater controller 6 within a range between a minimum value X0 and a maximum value X1.

In the example of FIG. 3, the distribution valve 381 is configured such that the flow ratio k decreases (that is, the bypass flow q2 decreases) as the number of steps X increases. At the minimum number of steps X0, the flow rate ratio k=kmax, and at the maximum number of steps X1, the flow rate ratio k=kmin.

Note that the reference characteristic line 400 indicating the correspondence between the number of steps X and the flow rate k can be determined in advance based on the results of actual machine tests in advance. By setting the function for calculating the flow rate k from the number of steps X and its inverse function according to the reference characteristic line 400, the conversion from the number of steps X to the flow rate k and the conversion from the flow rate k to the number of steps X are performed. Both conversions are possible. The data defining the reference characteristic line 400 , the function and the inverse function can be stored in advance in a memory (not shown) within the water heater controller 6 .

As will be described later, the water heater controller 6 sets the number of steps X of the distribution valve 381 to the minimum step so that the bypass flow rate q2 is maximized, that is, the flow rate ratio k=kmax during hot water discharge from the tank unit 2. Set to number X0. On the other hand, during the backup hot water supply by the auxiliary heat source device 3, the water heater controller 6 mixes the high-temperature water heated by the heat exchanger 32 and the low-temperature water flowing through the bypass pipe 38 to produce hot water at the set temperature Tr* as the auxiliary heat source. The step number X of the distribution valve 381 is set so that the output from the machine 3 is obtained. The water heater controller 6 corresponds to one embodiment of the "control device".

Returning to FIG. 2, a temperature sensor 35 and a flow rate sensor 36 are arranged in the can body piping 31 . The temperature sensor 35 detects the temperature Tw of hot water entering from the tank unit 2 (hereinafter also referred to as "incoming water temperature"). The temperature sensor 35 can be provided in the can body piping 31 as shown in FIG. The flow rate sensor 36 is arranged downstream (on the can body side) of the distribution valve 381 and detects the can body flow rate q1 from the water inlet pipe 30 to the can body pipe 31 .

The upstream end of hot water discharge pipe 34 is connected to heat exchanger 32 , and the downstream end of hot water discharge pipe 34 is connected to hot water discharge connection port 341 . A temperature sensor 342 is arranged on the upstream side (the can body side) of the junction 39 to which the bypass pipe 38 of the hot water discharge pipe 34 is connected. The temperature sensor 342 detects the temperature Tb of the high-temperature water (hereinafter also referred to as "can body temperature").

A temperature sensor 37 and a flow control valve 343 are arranged downstream of the junction 39 to which the bypass pipe 38 of the hot water discharge pipe 34 is connected. The temperature sensor 37 detects the outlet hot water temperature Th after the high-temperature water and the low-temperature water are mixed. The flow control valve 343 is controlled to throttle the flow rate of hot water supply when it is difficult to supply hot water according to the set temperature due to insufficient heating capacity of the boiler body 4 .

Incoming water temperature Tw detected by temperature sensor 35 , boiler body temperature Tb detected by temperature sensor 342 , and outlet hot water temperature Th detected by temperature sensor 37 are transmitted to water heater controller 6 .

In the configuration examples of FIGS. 1 and 2, the heat exchanger 32 corresponds to an example of a "heat exchanger." Further, the boiler pipe 31 and the portion of the hot water discharge pipe 34 on the upstream side (on the boiler body side) of the junction 39 constitutes an embodiment of a "heating channel". Bypass tube 38 corresponds to one embodiment of a "bypass flow path."

Returning to FIG. 1, the tank controller 5 has a microcomputer and communication section (not shown). The microcomputer incorporates a memory, a CPU (Central Processing Unit) and an input/output interface. The communication unit has a communication function. The microcomputer controls the operation of hot water supply system 100 according to a user command input to remote controller 51 by executing a program stored in memory.

The water heater controller 6 has a microcomputer and a communication section. The microcomputer is configured in the same manner as the microcomputer of the tank controller 5 and has a built-in memory. The communication unit has a communication function.

Each of the main heat source device 1 and the remote control 51 has a microcomputer and a communication section (not shown). Each of the tank controller 5, the water heater controller 6, the main heat source device 1, and the remote controller 51 can bi-directionally communicate with each other using the communication unit.

In the configuration example of FIG. 1, the tank controller 5 receives an operation signal such as a set temperature from a remote control 51 and output signals (detected values) from various temperature sensors, flow sensors, etc., and controls the overall operation of the hot water supply system 100. , it generates a control command to each device. The control command includes a control command to the main heat source device 1 and a control command to the auxiliary heat source machine 3 .

In the auxiliary heat source device 3 , the water heater controller 6 mainly controls the combustion operation in the boiler body 4 . Specifically, the hot water supply controller 6 executes the hot water supply optimization process according to the temperature of the hot water that is supplied from the tank unit 2 (intake water temperature Tw). In the specification of the present application, the hot water supply optimization process is a process for optimizing the hot water supply so that the outlet hot water temperature Th is maintained at the set temperature Tr* in accordance with the change in the temperature Tw of water entering from the tank unit 2. be.

[Hot water supply optimization process]
Next, hot water supply optimization processing executed in the auxiliary heat source device 3 according to the present embodiment will be described.

FIG. 4 is a diagram for explaining hot water supply optimization processing executed in the auxiliary heat source device 3. As shown in FIG. FIG. 4 shows a waveform diagram showing an operation example of the auxiliary heat source device 3 when the temperature Tw of water entering from the tank unit 2 changes over time.

Referring to FIG. 4, at time t0, when the user opens hot water tap K and flow rate sensor 36 detects a flow rate equal to or higher than the minimum operating flow rate (MOQ), water heater controller 6 executes hot water supply optimization processing. to start.

Assume that the incoming water temperature Tw is lower than the set temperature Tr* at time t0. In the operation example of FIG. 4, there is high-temperature water in the hot water storage tank 21 of the tank unit 2, but when cold hot water remains in the connection pipe 41, the high-temperature water is supplied to the auxiliary heat source machine 3 through the connection pipe 41. It is assumed that the hot water remaining in the connection pipe 41 first enters the auxiliary heat source machine 3 before the connection pipe 41 is connected.

The water heater controller 6 executes combustion control of the auxiliary heat source device 3 according to the temperature Tw of water entering from the tank unit 2 . The water heater controller 6 resets the combustion prohibition flag to "0" when permitting combustion, and sets the combustion prohibition flag to "1" when prohibiting combustion.

At time t0, water heater controller 6 sets the combustion prohibition flag to "0" to permit combustion. The water heater controller 6 starts the combustion operation in the boiler body 4, heats the incoming staying hot water to the set temperature Tr*, and supplies hot water to the hot water tap K. Specifically, when the combustion operation is started, the water heater controller 6 controls the amount of heat generated in the boiler body 4 and the opening degree of the distribution valve 381 ( That is, the flow ratio k) by the distribution valve 381 is controlled.

The amount of heat generated in the can body 4 is controlled by the amount of gas supplied from the combustion burner 33 as a whole. Therefore, in order to determine the amount of gas supplied from the combustion burner 33 as a whole, the required amount of heat generated P* in the can body 4 is set so that the can body temperature Tb coincides with the can body target temperature Tb*. Specifically, the can body target temperature Tb* is set higher than the set temperature Tr*. Thus, by mixing with the low-temperature water in the bypass pipe 38, the outlet heated water temperature Th can be controlled to the set temperature Tr*. Further, the amount of temperature increase ΔTb required for the can body 4 is indicated by the difference between the can body target temperature Tb* and the incoming water temperature Tw detected by the temperature sensor 35 (ΔTb=Tb*−Tw). Therefore, the required amount of heat generated P* in the can body 4 can be calculated according to the product of the can body flow rate q1 and the required temperature rise amount ΔTb (P*=q1·ΔTb).

The water heater controller 6 sets the amount of gas supplied from the entire combustion burner 33 in correspondence with the calculated required amount of heat generated P*. For example, the water heater controller 6 controls the opening degree of the gas proportional valve 333 and the opening and closing of the capacity switching valves 335a to 335c so as to realize a combination of the number of burners and the gas flow rate that realizes the gas supply amount. .

The valve opening degree of the distribution valve 381 is controlled so that the outlet heated water temperature Th matches the set temperature Tr*. Specifically, the water heater controller 6 controls the outlet hot water temperature Th to the set temperature Tr* based on the set temperature Tr* and the temperatures (Tw, Tb, Th) detected by the temperature sensors 35, 342, and 37. Set the number of steps X of the distribution valve 381 for

In the auxiliary heat source device 3, the amount of heat associated with the temperature rise from the low-temperature water to the outlet hot water temperature and the amount of heat associated with the temperature drop from the high-temperature water to the outlet hot water temperature are balanced. Therefore, the following equation (2) holds between the boiler flow rate q1, the bypass flowrate q2, the boiler temperature Tb, the incoming water temperature Tw, and the outlet hot water temperature Th.

q2·(Th−Tw)=q1·(Tb−Tw) (2)
From the equation (2), the flow ratio k shown in the equation (1) can be expressed by the following equation (3) using the boiler body temperature Tb, the incoming water temperature Tw and the outlet hot water temperature Th.

k=q2/q1=(Tb-Th)/(Th-Tw) (3)
Therefore, the water heater controller 6 can control the outlet hot water temperature Th according to the set temperature Tr* by setting the number of steps X of the distribution valve 381 according to the flow ratio k calculated from equation (3). Furthermore, after using the calculated value from equation (3) as a feedforward control term, a feedback control term for compensating for the temperature difference ΔTh (=Tr*-Th) of the outlet heated water temperature is calculated, and the flow rate ratio is calculated according to the sum of the two. It is also possible to set k, that is, the number of steps X of the distribution valve 381 .

In the example of FIG. 4 , when the hot water remaining in the connecting pipe 41 passes through, the high-temperature water from the hot water storage tank 21 of the tank unit 2 whose temperature is adjusted to the set temperature Tr* enters the auxiliary heat source device 3 . As a result, after time t1, the incoming water temperature Tw rises and approaches the set temperature Tr*.

In order to transition from the backup hot water supply to the tank unit 2 hot water supply, the water heater controller 6 performs combustion inhibition control based on the temperature difference ΔTw (=Tr*-Tw) between the set temperature Tr* and the incoming water temperature Tw. . Specifically, the water heater controller 6 compares the temperature difference ΔTw with the first threshold A°C. At time t2, when the temperature difference ΔTw becomes smaller than the first threshold A° C., the water heater controller 6 sets the combustion prohibition flag to "1" to prohibit combustion.

When the combustion is prohibited, the water heater controller 6 stops the combustion of the auxiliary heat source device 3 and adjusts the step of the distribution valve 381 so that the bypass flow rate q2 becomes maximum, that is, the flow rate ratio k=kmax. Set the number X to the minimum number of steps X0. By doing so, the flow rate of hot water flowing in the can body 4 whose combustion is stopped is restricted, so that the water flow resistance of the auxiliary heat source device 3 in the hot water supply circuit can be reduced. As a result, an energy saving effect can be obtained.

When the hot water in the hot water storage tank 21 decreases and the hot water runs out during hot water discharge from the tank unit 2 , low temperature water is supplied from the tank unit 2 to the auxiliary heat source device 3 . As a result, after time t4, the incoming water temperature Tw gradually decreases. The water heater controller 6 permits combustion based on the temperature difference ΔTw between the set temperature Tr* and the incoming water temperature Tw in order to transition from the hot water supply of the tank unit 2 to the backup hot water supply. Specifically, the water heater controller 6 compares the temperature difference ΔTw with the second threshold B°C. The second threshold B° C. is set to a value larger than the first threshold A° C. (A° C.<B° C.) in order to avoid hunting.

At time t5, when the temperature difference ΔTw becomes greater than the second threshold value B° C., the water heater controller 6 resets the combustion prohibition flag to "0" to cancel the prohibition of combustion. When the prohibition of combustion is released, the water heater controller 6 restarts the combustion operation in the boiler body 4, heats the incoming low-temperature water to the set temperature Tr*, and supplies hot water to the hot water tap K. As described above, when the combustion operation is started, the water heater controller 6 controls the amount of heat generated in the boiler body 4 and the opening degree of the distribution valve 381 ( The flow ratio k) by the distribution valve 381 is controlled.

In this way, when the incoming water temperature Tw rises during backup hot water supply and the temperature difference ΔTw<A° C. between the set temperature Tr* and the incoming water temperature Tw, the water heater controller 6 prohibits the combustion of the auxiliary heat source device 3. By setting the number of steps X of the distributing valve 381 to the minimum number of steps X0 (flow ratio k=kmax), the hot water is transferred to the tank unit 2 . Further, when the temperature difference ΔTw>B° C. when the temperature difference ΔTw>B° C. is reached, the water heater controller 6 permits the combustion of the auxiliary heat source 3, and sets the discharged hot water temperature Th to the set temperature Tr*. By setting the number of steps X of the distributing valve 381 for controlling to , the transition is made to the backup hot water supply.

By controlling permission/prohibition of combustion of the auxiliary heat source device 3 based on the temperature difference ΔTw between the incoming water temperature Tw and the set temperature Tr*, the difficulty of controlling combustion when the incoming water temperature Tw rises is eliminated. Therefore, the overshoot of the outlet heated water temperature Th can be suppressed. Further, frequent repetition of execution/stop of combustion control can be prevented when the temperature difference ΔTw between the inlet water temperature Tw and the set temperature Tr* is small. As a result, fluctuations in the outlet heated water temperature Th can be suppressed.

Furthermore, during hot water discharge from the tank when combustion of the auxiliary heat source device 3 is unnecessary, the flow rate of hot water flowing in the boiler body 4 whose combustion is stopped is limited, so the water flow resistance of the auxiliary heat source device 3 in the hot water supply circuit is reduced. can be reduced. As a result, an energy saving effect can be obtained.

On the other hand, in the above configuration, hot water entering the primary heat exchanger 32a of the heat exchanger 32 at the point in time (time t2 in FIG. 4) when an increase in the incoming water temperature Tw is detected and combustion of the auxiliary heat source device 3 is stopped, That is, the temperature of the hot water on the upstream side of the primary heat exchanger 32a (including the secondary heat exchanger 32b) in the boiler piping 31 may be lower than the incoming water temperature Tw. Therefore, if the combustion of the auxiliary heat source device 3 is stopped at this point, the hot water that enters the primary heat exchanger 32a after that is not heated, and the boiler body 4 outputs low-temperature water. As a result, immediately after time t2, low-temperature water that is lower than the set temperature Tr* is temporarily supplied to the hot water tap K. Therefore, until the low-temperature water in the secondary heat exchanger 32b is heated, it is required to continue the combustion without stopping the combustion of the auxiliary heat source device 3.

On the other hand, when a decrease in the incoming water temperature Tw is detected and combustion of the auxiliary heat source device 3 is started (time t5 in FIG. 4), the prohibition of combustion is lifted and the mixture of fuel gas and combustion air is ignited by the ignition device. It may take some time to ignite and generate combustion heat from the combustion burner 33 . In this case, low-temperature water that is not heated within that time is output from the can body 4 . Therefore, it is required to detect a decrease in the incoming water temperature Tw as early as possible to start combustion in the auxiliary heat source device 3 .

Therefore, the water heater controller 6 estimates the temperature of the water entering the primary heat exchanger 32a so that the accuracy of the combustion control of the auxiliary heat source device 3 does not deteriorate in response to the change in the incoming water temperature Tw.

FIG. 5 is a schematic diagram for explaining estimation of the temperature of water entering the primary heat exchanger 32a.
Referring to FIG. 5 , water heater controller 6 calculates an estimated incoming water temperature Twd in primary heat exchanger 32 a based on incoming water temperature Tw detected by temperature sensor 35 . Using the detected value Tw[n] of the incoming water temperature Tw in the current control cycle, the estimated incoming water temperature Twd[n] in the current control cycle is calculated according to the following equation (4).

Twd[n]=K1·Tw[n]+K2·Twd[n−1] (4)
In equation (4), Twd[n-1] is the estimated inlet water temperature Twd in the previous control cycle. Also, the coefficients K1 and K2 are expressed as K1=1/(L+1) and K2=L/(L+1). K1 and K2 can be tuned to appropriate values by the adjustment parameter L while maintaining K1+K2=1.0.

Note that the value of the adjustment parameter L varies depending on the distance of the piping (including the secondary heat exchanger 32b) from the arrangement position of the temperature sensor 35 in the boiler piping 31 to the primary heat exchanger 32a, the piping shape, and the like. For example, it can be set in advance for each model by actual machine test or simulation.

Further, the adjustment parameter L may be variable according to the can body flow rate q1. For example, it is preferable to increase the speed at which Tw is reflected in Twd by setting L to be smaller and K1 to be larger as the can body flow rate q1 increases.

According to the equation (4), the estimated inlet water temperature Twd to the primary heat exchanger 32a is based on the history of the inlet water temperature Tw so that the change in the inlet water temperature Tw is reflected with a time delay according to the coefficients K1 and K2. is calculated sequentially.

FIG. 6 shows an example of calculation of the estimated water inlet temperature Twd according to Equation (4).
Referring to FIG. 6, temperature waveform L1 is obtained by plotting changes in incoming water temperature Tw detected by temperature sensor 35 on the time axis. A temperature waveform L2 is obtained by plotting on the time axis the calculation result according to the equation (4) of the estimated incoming water temperature Twd in the primary heat exchanger 32a when the incoming water temperature Tw changes according to the temperature waveform L1. From the comparison of the temperature waveforms L1 and L2, the estimated inlet water temperature Twd is calculated so as to give a time delay to the change in the inlet water temperature Tw.

The temperature waveform L2 coincides with the temperature waveform L1 before time t1, and after time t1, the temperature waveform L2 rises slowly with a delay from the temperature waveform L1, and coincides with the temperature waveform L1. Further, the temperature waveform L2 matches the temperature waveform L1 before time t4, and after time t4, the temperature waveform L2 gradually decreases after the temperature waveform L1 and matches the temperature waveform L1.

FIG. 6 further shows an operation example of the hot water supply optimization process in the auxiliary heat source device 3 when the incoming water temperature Tw and the estimated incoming water temperature Twd change over time.

In FIG. 6, the waveform L3 of the combustion inhibition flag and the waveform L5 of the control of the flow ratio k (step number X of the distribution valve 381) by the distribution valve 381 are the same as those shown in FIG. A change in outlet heated water temperature Th due to waveform L3 of the combustion inhibition flag and waveform L5 of control in distribution valve 381 is shown in temperature waveform L7.

On the other hand, in FIG. 6, the waveform L4 of the combustion prohibition flag and the waveform L6 of the control of the flow ratio k (step number X of the distribution valve 381) by the distribution valve 381 are created based on the temperature waveform L2 of the estimated incoming water temperature Twd. is. Specifically, after time t1, when the estimated incoming water temperature Twd rises, the water heater controller 6 sets the temperature difference ΔTwd between the set temperature Tr* and the estimated incoming water temperature Twd to transition from the backup hot water supply to the tank unit 2 hot water supply. Control for inhibiting combustion is executed based on (=Tr*-Twd). The water heater controller 6 compares the temperature difference ΔTwd with the first threshold A°C. At time t3, when the temperature difference ΔTwd becomes smaller than the first threshold A° C., the water heater controller 6 sets the combustion prohibition flag to "1" to prohibit combustion.

When the combustion is prohibited, the water heater controller 6 stops the combustion of the auxiliary heat source device 3 and adjusts the step of the distribution valve 381 so that the bypass flow rate q2 becomes maximum, that is, the flow rate ratio k=kmax. Set the number X to the minimum number of steps X0.

After time t4, when the estimated inlet water temperature Twd gradually decreases, the water heater controller 6 switches from the hot water outlet of the tank unit 2 to the backup hot water outlet based on the temperature difference ΔTwd between the set temperature Tr* and the inlet water temperature Twd. Execute burn permission control. The water heater controller 6 compares the temperature difference ΔTwd with the second threshold B°C. At time t5, when the temperature difference ΔTwd becomes greater than the second threshold B° C., the water heater controller 6 resets the combustion prohibition flag to "0" to cancel the prohibition of combustion. When the prohibition of combustion is released, the water heater controller 6 restarts the combustion operation in the boiler body 4, heats the incoming low-temperature water to the set temperature Tr*, and supplies hot water to the hot water tap K. As described above, when the combustion operation is started, the water heater controller 6 controls the amount of heat generated in the boiler body 4 and the opening degree of the distribution valve 381 ( The flow ratio k) by the distribution valve 381 is controlled. A temperature waveform L8 shows a change in outlet heated water temperature Th due to waveform L4 of the combustion prohibition flag and waveform L6 of control in distribution valve 381 .

Comparing the temperature waveform L7 of the outlet heated water temperature Th with the temperature waveform L8, it can be seen that when the inlet water temperature Tw rises (time t1), the outlet heated water temperature Th is stable in the temperature waveform L8, whereas the temperature A temporary temperature drop occurs in the waveform L7. On the other hand, when the incoming water temperature Tw drops (time t4), the outlet hot water temperature Th is stable in the temperature waveform L7, whereas the temperature temporarily drops in the waveform L8. According to this, if suitable temperature waveforms can be formed when the inlet water temperature Tw rises and falls, the outlet heated water temperature Th can be maintained at the set temperature Tr* both when the inlet water temperature Tw rises and falls. It becomes possible.

Therefore, the water heater controller 6 uses the lower temperature of the incoming water temperature Tw detected by the temperature sensor 35 and the estimated incoming water temperature Twd to control combustion and prohibition of combustion of the auxiliary heat source device 3, and the distribution valve 381 to control the degree of opening of the In this way, the outlet hot water temperature Th changes according to the temperature waveform L8 when the incoming water temperature rises, and changes according to the temperature waveform L7 when the incoming water temperature drops. Since the water heater controller 6 can make the combustion control and the opening degree control of the distribution valve 381 quickly follow changes in the incoming water temperature, even when the incoming water temperature Tw from the tank unit 2 changes, the outlet hot water temperature Th can be kept at the set temperature Tr*.

FIG. 7 is a flowchart for explaining the hot water supply optimization process executed in the auxiliary heat source device 3 . The flowchart shown in FIG. 7 can be executed by the water heater controller 6 at regular control cycles.

Referring to FIG. 7, water heater controller 6 determines in step S01 whether or not the flow rate at auxiliary heat source device 3 exceeds the minimum operating flow rate (MOQ). Hereinafter, the state in which the flow rate in the auxiliary heat source device 3 exceeds the MOQ is also referred to as "MOQ on", and the state in which the flow rate does not exceed the MOQ is also referred to as "MOQ off".

When MOQ is off (NO in S01), water heater controller 6 skips subsequent steps S02 to S11. On the other hand, when MOQ is on (YES in S01), water heater controller 6 proceeds to steps S02 to S11. Specifically, when the water heater controller 6 acquires the incoming water temperature Tw detected by the temperature sensor 35 in step S02, in step S03, the current incoming water temperature Tw acquired in step S02 is calculated by the formula (4 ), the current estimated water inlet temperature Twd to the primary heat exchanger 32a is calculated.

Next, in step S04, water heater controller 6 calculates the lower temperature of current inlet water temperature Tw and estimated current inlet water temperature Twd. In the following description, the lower one of the incoming water temperature Tw and the estimated incoming water temperature Twd is referred to as minimum incoming water temperature min(Tw, Twd).

Subsequently, in step S05, water heater controller 6 calculates temperature difference ΔTw (=Tr*-min(Tw, Twd)) between set temperature Tr* and minimum inlet water temperature min(Tw, Twd). The water heater controller 6 compares the calculated temperature difference ΔTw with the second threshold B° C. in step S06.

If temperature difference ΔTw>B° C. (YES in S06), water heater controller 6 proceeds to step S07 and resets the combustion inhibition flag to "0". That is, the water heater controller 6 permits the combustion of the auxiliary heat source machine 3 . Therefore, the water heater controller 6 performs the combustion operation in the can body 4, heats the low temperature water to the set temperature Tr*, and supplies hot water to the hot water tap K. The water heater controller 6 controls the amount of heat generated in the can body 4 so that the outlet hot water temperature Th is controlled to the set temperature Tr*. Furthermore, the water heater controller 6 controls the valve opening degree of the distribution valve 381 (the flow rate k by the distribution valve 381) in step S08.

On the other hand, if temperature difference ΔTw≦B° C. in step S07 (NO in S07), water heater controller 6 proceeds to step S09 and compares temperature difference ΔTw with first threshold A° C. If temperature difference ΔTw<A° C. (YES in S09), water heater controller 6 proceeds to step S10 and sets the combustion inhibition flag to "1". That is, the water heater controller 6 prohibits the combustion of the auxiliary heat source device 3 . Therefore, the water heater controller 6 stops the combustion of the auxiliary heat source device 3, and in step S11, adjusts the number of steps of the distribution valve 381 so that the bypass flow rate q2 becomes maximum, that is, the flow rate ratio k=kmax. Set X to the minimum number of steps X0.

As described above, according to the auxiliary heat source machine (hot water supply device) according to the present embodiment, the inlet water temperature changes by controlling the permission/prohibition of combustion based on the temperature difference between the inlet water temperature and the set temperature. Since the difficulty of combustion control is eliminated, the outlet hot water temperature can be maintained at the set temperature even if the inlet water temperature changes.

In addition, during hot water supply from the tank when the combustion of the auxiliary heat source is unnecessary, the flow rate of hot water flowing in the boiler is limited compared to the backup hot water supply, so the water flow resistance of the auxiliary heat source in the hot water supply circuit should be reduced. energy saving effect can be obtained.

Furthermore, the temperature of water entering the heat exchanger is estimated based on the temperature of the incoming water detected by the temperature sensor, and the lower temperature of the detected and estimated incoming water temperature is used for combustion control and distribution valve of the auxiliary heat source equipment. By executing the opening degree control, the combustion control and the opening degree control of the distribution valve can be made to quickly follow the change in the incoming water temperature, so it is possible to stably maintain the outlet heated water temperature at the set temperature.

The configuration of the auxiliary heat source machine 3 (hot water supply device) is not limited to the examples shown in FIGS. The present invention can be commonly applied to the control of the mixing ratio of high-temperature water and low-temperature water in a bypass mixing type hot water supply apparatus.

Also, as the heat exchanger 32 in the auxiliary heat source device 3, a latent heat recovery type configuration is illustrated in which a primary heat exchanger that absorbs the sensible heat of the combustion gas and a secondary heat exchanger that recovers the latent heat from the flue gas are combined. However, the present invention is not limited to this, and the present invention can be applied to those having no secondary heat exchanger, and it is not essential to be of the latent heat recovery type.

Furthermore, as a heat source for heating the heat exchanger, a combustion burner that generates heat of combustion was exemplified, but the invention is not limited to this, and various types of heat sources such as a heat source that generates heat using electricity can be applied. .

It should be considered that the embodiments disclosed this time are illustrative in all respects and not restrictive. The scope of the present invention is indicated by the scope of the claims rather than the above description, and is intended to include all modifications within the scope and meaning of equivalents of the scope of the claims.

1 main heat source device, 2 tank unit, 3 auxiliary heat source device (hot water supply device), 4 combustion can body, 6 water heater controller, 30 water inlet pipe, 31 boiler pipe, 32 heat exchanger, 33 combustion burner, 34 hot water outlet pipe, 35, 37 342 temperature sensor, 38 bypass pipe, 100 hot water system.

Claims (4)

a heat source;
a heat exchanger that heats low-temperature water with heat from the heat source and outputs high-temperature water;
a heating channel for passing the cold water through the heat exchanger;
a bypass flow path branching from the heating flow path upstream of the heat exchanger and joining the heating flow path at a junction point downstream of the heat exchanger;
a flow rate ratio adjusting unit that controls a flow rate ratio of the bypass channel with respect to the flow rate of the low-temperature water;
A control device that controls the operation of the heat source unit and sets the operation amount of the flow rate ratio adjustment unit,
The control device prohibits the operation of the heat source unit when the temperature difference of the low-temperature water with respect to the set temperature of the outlet hot water is smaller than a first threshold value, and the operation amount of the flow rate ratio adjustment unit is set to the maximum value of the predetermined controllable range of the flow rate ratio,
When the temperature difference is larger than a second threshold larger than the first threshold, the operation of the heat source unit is permitted, and the operation amount of the flow rate ratio adjustment unit is set to a value smaller than the maximum value is configured to set to
The heating channel comprises a boiler pipe having an upstream end connected to the water inlet pipe and a downstream end connected to the heat exchanger, and an upstream end connected to the heat exchanger and the bypass flow at the junction point. a hot water outlet pipe connected to the passage,
The heat exchanger includes a primary heat exchanger that heats the low-temperature water with sensible heat from the heat source,
further comprising a first temperature detector that detects the temperature of the low-temperature water entering the boiler pipe from the water inlet pipe;
The control device estimates the temperature of the low-temperature water entering the primary heat exchanger from the boiler pipe based on the history of temperatures detected by the first temperature detector, and estimates the low-temperature water. A water heater, wherein the temperature difference is calculated using the lower temperature of the temperature and the detected temperature . Further comprising a flow rate detector that detects the flow rate of the heating channel,
2. The hot water supply apparatus according to claim 1 , wherein said control device calculates said estimated temperature such that the time lag of said estimated temperature with respect to said detected temperature decreases as the flow rate detected by said flow rate detector increases. further comprising a second temperature detector located downstream of the coupling point for detecting the outlet temperature of hot water after mixing the high temperature water and the low temperature water;
The flow ratio adjustment unit includes a distribution valve for controlling the flow rate of the bypass channel,
The control device sets the degree of opening of the distribution valve to an upper limit when the temperature difference is smaller than the first threshold,
2. The opening degree of the distribution valve is controlled so that the temperature detected by the second temperature detector matches the set temperature when the temperature difference is greater than the second threshold. 2. The water heater according to 2 . a hot water storage tank for storing hot water heated by the main heat source;
a pipe to which the hot water of the hot water storage tank is supplied;
an auxiliary heat source device that heats the hot water supplied from the pipe to the set temperature and outputs it,
A hot water supply system, wherein the auxiliary heat source machine includes the hot water supply apparatus according to any one of claims 1 to 3 .

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