JP2024067242A - Hot water supply system with instant hot water function and hot water heater with instant hot water function - Google Patents

Abstract

[Problem] To provide a hot water supply system with an instant hot water function and a hot water heater with an instant hot water function that can quickly determine when the hot water tap has started to be used, and can quickly heat the hot water in the circulation path if the temperature is low, and supply hot water from the hot water tap, thereby improving the comfort and convenience of the user. [Solution] In a hot water supply system with an instant hot water function (100), a circulation pump (5) circulates hot water in a circulation path (7) formed by a junction (50), a water supply pipe (10), an internal flow path (4A), a hot water outlet pipe (20), a hot water distribution pipe (60), and a return pipe (65). A control unit (C1) executes a hot water supply operation, an instant hot water operation, and a freeze prevention operation. The control unit (C1) controls the circulation pump (5) so that a second circulation flow rate (CF2), which is a flow rate detected by a water volume sensor (70) when the circulation pump (5) is operating in the freeze prevention operation, is smaller than a first circulation flow rate (CF1), which is a flow rate detected by a water volume sensor (70) when the circulation pump (5) is operating in the instant hot water operation. [Selected Figure] FIG. 3

Description

The present invention relates to a hot water supply system with an instant hot water function and a hot water heater with an instant hot water function.

Patent Document 1 discloses an example of a conventional hot water supply system with an instant hot water function. This hot water supply system with an instant hot water function includes a heat exchanger, a heating means, a water supply pipe, a hot water outlet pipe, a junction, a hot water tap, a hot water distribution pipe, a return pipe, a circulation pump, a water volume sensor, and a control unit.

The heat exchanger has an internal flow path. The heating means heats the heat exchanger. The water supply pipe guides water supplied from an external water supply source to the internal flow path. The hot water outlet pipe sends out hot water that has passed through the internal flow path. The water supplied from the water supply source passes through the junction upstream of the water supply pipe. The hot water distribution pipe supplies the hot water sent out from the hot water outlet pipe to the hot water tap. The return pipe returns the hot water from the hot water distribution pipe to the junction. The circulation pump is provided in the water supply pipe. The water volume sensor is provided in the water supply pipe and detects the flow rate of hot water.

The junction, water supply pipe, internal flow path, hot water outlet pipe, hot water distribution pipe and return pipe form a circulation path. The circulation pump circulates the hot water within the circulation path.

When the flow rate detected by the water volume sensor reaches or exceeds a predetermined usage determination flow rate, the control unit determines that use of the hot water tap has started. The control unit then performs hot water supply operation by operating the heating means with the circulation pump stopped, to supply hot water from the hot water tap.

When an instant hot water request is received, the control unit performs instant hot water operation by continuously or intermittently operating the circulation pump and heating means to maintain the hot water in the circulation path at or above a predetermined temperature.

When an anti-freeze request is received, the control unit performs anti-freeze operation by operating the circulation pump continuously or intermittently to prevent the hot water in the circulation path from freezing.

According to FIG. 5 of Patent Document 1, when the circulation pump is circulating hot water in the circulation path during instant hot water operation, the control unit determines whether the flow rate X detected by the water volume sensor is equal to or greater than a predetermined usage determination flow rate (basic flow rate Y + α), and if the result is "YES," determines that the hot water tap has started to be used.

JP 2021-85549 A

In the above-mentioned conventional hot water supply system with instant hot water function, even if the hot water tap is opened to start dispensing hot water while the circulation pump is circulating hot water in the circulation path, water is immediately replenished from the external water source to the circulation path. For this reason, the flow rate detected by the water volume sensor does not change significantly unless hot water is dispensed from the hot water tap at a flow rate that is somewhat greater than the flow rate at which hot water circulates in the circulation path when the hot water tap is closed.

In other words, if the flow rate of hot water circulating in the circulation path is large when the hot water tap is "closed," the usage determination flow rate is set to a correspondingly large value, so it cannot be determined that the hot water tap has started to be used until the amount of hot water flowing from the hot water tap becomes large to a certain extent.

Therefore, this hot water supply system with instant hot water function is required to quickly determine when the hot water tap has started to be used, and if the temperature of the hot water in the circulation path is low, to quickly heat it and supply it from the hot water tap, and ultimately to improve the comfort and convenience of the user. The same applies to the hot water heater with instant hot water function that is provided in this hot water supply system with instant hot water function.

The present invention has been made in consideration of the above-mentioned conventional situation, and aims to provide a hot water supply system and a hot water heater with an instant hot water function that can quickly determine when the hot water tap has started to be used, and if the temperature of the hot water in the circulation path is low, can quickly heat it and supply hot water from the hot water tap, thereby improving the comfort and convenience of the user.

The hot water supply system with instant hot water function of the present invention comprises a heat exchanger having an internal flow path formed therein,
A heating means for heating the heat exchanger;
A water supply pipe that guides water supplied from an external water supply source to the internal flow path;
A hot water outlet pipe that delivers hot water that has passed through the internal flow path;
a confluence portion through which water supplied from the water supply source passes upstream of the water supply pipe;
A hot water tap and
a hot water distribution pipe that supplies the hot water sent from the hot water outlet pipe to the hot water tap;
A return pipe for returning hot water from the hot water distribution pipe to the junction;
A circulation pump provided in the water supply pipe, the hot water outlet pipe, the hot water distribution pipe, or the return pipe;
A water flow sensor provided in the water supply pipe, the hot water outlet pipe, or the hot water distribution pipe to detect a flow rate of hot water;
A control unit;
Equipped with
A circulation path is formed by the junction, the water supply pipe, the internal flow path, the hot water outlet pipe, the hot water distribution pipe, and the return pipe,
The circulation pump circulates hot and cold water within the circulation path,
When the flow rate detected by the water volume sensor becomes equal to or greater than a predetermined use determination flow rate, the control unit stops the circulation pump and operates the heating means to supply hot water from the hot water tap,
When an instant hot water operation command is received, the control unit continuously or intermittently operates the circulation pump and the heating means to perform instant hot water operation to maintain the hot water in the circulation path at a predetermined first temperature or higher,
The control unit is configured to perform a freeze prevention operation to prevent freezing of hot water in the circulation path by continuously or intermittently operating at least the circulation pump of the circulation pump and the heating means when the ambient temperature becomes lower than a predetermined second temperature.
The control unit is characterized in that it controls the circulation pump so that the second circulation flow rate, which is the flow rate detected by the water volume sensor when the circulation pump is operating during the anti-freeze operation, is smaller than the first circulation flow rate, which is the flow rate detected by the water volume sensor when the circulation pump is operating during the instant hot water operation.

In the hot water supply system with instant hot water function of the present invention, the control unit controls the circulation pump so that the second circulation flow rate for the freeze prevention operation is smaller than the first circulation flow rate for the instant hot water operation. With this configuration, the control unit can set the usage judgment flow rate for determining whether or not the hot water tap has been started to be used while the circulation pump is operating in the freeze prevention operation to a value smaller than the usage judgment flow rate for determining whether or not the hot water tap has been started to be used while the circulation pump is operating in the instant hot water operation.

As a result, the control unit can quickly determine that use of the hot water tap has begun while the circulation pump is operating during freeze prevention operation, and can quickly heat the cold water in the circulation path and supply it from the hot water tap.

In addition, while it is difficult for the control unit to quickly determine that the hot water tap has started to be used while the circulation pump is operating during instant hot water operation, hot water at a low temperature is not dispensed from the hot water tap because the hot water in the circulation path is maintained at or above the first temperature.

The hot water supply system with instant hot water function of the present invention can therefore quickly determine when the hot water tap has been started to be used, and if the temperature of the hot water in the circulation path is low, it can quickly heat it and supply it from the hot water tap, thereby improving the comfort and convenience of the user.

In addition, this hot water supply system with instant hot water function can reduce energy consumption and noise caused by the operation of the circulation pump during freeze prevention operation.

It is preferable that the control unit is capable of controlling the circulation pump so that the first circulation flow rate is a predetermined first target flow rate, and the second circulation flow rate is a predetermined second target flow rate that is smaller than the first target flow rate. The use judgment flow rate during instant hot water operation and while the circulation pump is operating is preferably a value set based on the first target flow rate and a value larger than the first target flow rate. It is also preferable that the use judgment flow rate during freeze prevention operation and while the circulation pump is operating is a value set based on the second target flow rate and is smaller than the use judgment flow rate during instant hot water operation and while the circulation pump is operating, and is a value larger than the second target flow rate.

This configuration makes it possible to quickly determine when the hot water tap has started to be used, and if the temperature of the hot water in the circulation path is low, it can be quickly heated and dispensed from the hot water tap with a high degree of certainty, thereby improving the comfort and convenience of the user with a high degree of certainty.

The freeze prevention operation preferably includes a non-heating continuous circulation process in which the circulation pump is continuously operated while the heating means is stopped, and a heating circulation process in which the circulation pump and the heating means are continuously operated. The control unit is preferably configured to be able to determine whether or not the heating means is in a heating-unavailable state in which it is unable to heat the heat exchanger. If the control unit determines that the heating is unavailable in the heating circulation process, it preferably executes the non-heating continuous circulation process. The control unit then preferably controls the circulation pump so that the flow rate detected by the water flow sensor when determining that the heating is unavailable and executing the non-heating continuous circulation process is greater than the flow rate detected by the water flow sensor when determining that the heating is not unavailable and executing the heating circulation process.

When the control unit determines that the heating is not possible during the heating circulation process, it cannot execute hot water supply operation even if it determines that use of the hot water tap has started. In other words, under conditions in which heating is not possible, rapid detection of use of the hot water tap does not lead to improved comfort and convenience for the user. For this reason, when the control unit determines that the heating is not possible and executes the non-heating continuous circulation process, it increases the flow rate of hot water circulating through the circulation path, thereby suppressing the deterioration of anti-freeze performance in a heating not possible state, which ultimately leads to improved convenience for the user.

The hot water heater with instant hot water function of the present invention is a hot water heater with instant hot water function that is provided in the hot water supply system with instant hot water function of the present invention, and is characterized in that it is equipped with a heat exchanger, heating means, a water supply pipe, a hot water outlet pipe, a circulation pump, a water volume sensor, and a control unit, and the circulation pump is provided in the water supply pipe or the hot water outlet pipe, and the junction, hot water tap, hot water distribution pipe, and return pipe are installed outside the hot water heater with instant hot water function.

The hot water heater with instant hot water function of the present invention can achieve the same effects as the hot water supply system with instant hot water function of the present invention.

The hot water supply system with instant hot water function and hot water heater with instant hot water function of the present invention can quickly determine when the hot water tap has started to be used, and if the temperature of the hot water in the circulation path is low, it can be quickly heated and dispensed from the hot water tap, thereby improving the comfort and convenience of the user.

FIG. 1 is a schematic diagram of a hot water supply system with an instant hot water function according to an embodiment of the present invention. FIG. 2 is a flowchart of an execution program for the instant hot water operation and the freeze prevention operation in the hot water supply system with the instant hot water function of the embodiment. FIG. 3 is a flowchart of an execution program for the instant hot water operation and the freeze prevention operation in the hot water supply system with the instant hot water function of the embodiment. FIG. 4 is a flowchart of an execution program for the instant hot water operation and the freeze prevention operation in the hot water supply system with the instant hot water function of the embodiment. FIG. 5 is a flowchart of a hot water tap use determination program in the hot water supply system with an instant hot water function of the embodiment. FIG. 6 is a flowchart relating to a modified hot water supply system with an instant hot water function, in which step S150 in FIG. 4 is replaced with steps S151 to S153.

The following describes an embodiment of the present invention with reference to the drawings.

(Example)
As shown in FIG. 1, a hot water supply system 100 with an instant hot water function of the embodiment (hereinafter simply referred to as "hot water supply system 100") is an example of a hot water supply system with an instant hot water function of the present invention.

The embodiment of the water heater 1 with an instant hot water function (hereinafter simply referred to as "water heater 1") provided in the hot water supply system 100 is an example of a water heater with an instant hot water function of the present invention.

The hot water supply system 100 includes a hot water heater 1 having a housing 9, a heat exchanger 4, a combustion device 3, a gas supply pipe 30, a water supply pipe 10, a hot water outlet pipe 20, a circulation pump 5, a water volume sensor 70, and a control unit C1, and a junction section 50, a hot water tap 6, a hot water distribution pipe 60, and a return pipe 65 that are installed outside the hot water heater 1. The combustion device 3 is an example of the "heating means" of the present invention.

The hot water supply system 100 is installed in a house, facility, etc. The water heater 1 is a device that is mainly installed outdoors in a house, etc., and supplies high-temperature hot water to a hot water tap 6 installed in a kitchen, bathroom, etc.

<General configuration of water heater>
In the water heater 1, the housing 9 is substantially box-shaped and houses the heat exchanger 4, the combustion device 3, and the control unit C1. The housing 9 also houses the gas supply pipe 30, the water supply pipe 10, and the hot water outlet pipe 20, with their lower ends protruding downward from the bottom wall of the housing 9, and houses the gas supply pipe 30, the water supply pipe 10, and the hot water outlet pipe 20 except for their lower ends, as well as the circulation pump 5 and the water volume sensor 70.

A low-sensitivity thermistor 79 is provided on the bottom wall of the housing 9. The temperature-sensing portion of the low-sensitivity thermistor 79 is exposed to the outside of the housing 9. The low-sensitivity thermistor 79 detects the ambient temperature outside the water heater 1 and transmits it to the control unit C1.

The control unit C1 is an electronic circuit unit that includes a CPU (not shown), a memory unit C1M composed of memory elements such as ROM and RAM, an interface circuit that transmits and receives signals to and from the controlled object, and a power supply circuit that controls the power supply to the controlled object.

The memory unit C1M stores various programs and setting information for operating the water heater 1. The memory unit C1M also appropriately stores various information acquired by the control unit C1 during operation of the water heater 1.

The programs stored in the memory unit C1M include the "program for executing instant hot water operation and anti-freeze operation" shown in Figures 2 to 4, and the "program for determining whether or not the hot water tap is in use" shown in Figure 5.

A remote control 90 is connected to the control unit C1. The remote control 90 is installed near the hot water tap 6 in the kitchen, bathroom, etc.

The remote control 90 receives operation inputs such as starting and stopping the water heater 1, giving instructions for instant hot water operation, and inputting various setting information such as the target hot water temperature, through an operation section having multiple buttons, and transmits these to the control section C1.

The remote control 90 is also controlled by the control unit C1 to appropriately display the operating status of the water heater 1, various setting information, error messages, etc. on a display unit such as an LCD display.

The combustion device 3 has a combustion chamber 3C, a combustion fan 3F, and a burner 3B. The combustion chamber 3C is located in the middle of the housing 9 in the vertical direction. The combustion fan 3F is located below the combustion chamber 3C and supplies combustion air to the combustion chamber 3C. The flame port of the burner 3B is located within the combustion chamber 3C.

Fuel gas such as city gas or propane gas is supplied to the lower end of the gas supply pipe 30 from an external gas supply source (not shown). A main gas solenoid valve 30V and a gas proportional valve 30P are provided in the gas supply pipe 30. The gas supply pipe 30 branches into multiple pipes downstream of the gas proportional valve 30P, and each branch pipe is provided with a switching gas solenoid valve 31V.

The burner 3B is ignited by an igniter 3G that operates under the control of the control unit C1. The burner 3B discharges fuel gas supplied by the gas supply pipe 30 from the flame port, burns it, and generates high-temperature gas, which is the combustion exhaust gas.

The heat exchanger 4 is located at the top of the housing 9. The heat exchanger 4 has a can body 40C and a heat transfer tube 41.

The can body 40C is connected at its lower end to the upper end of the box-shaped body that defines the combustion chamber 3C, thereby communicating with the combustion chamber 3C. The can body 40C has an exhaust port 49. The exhaust port 49 opens at the upper end of the front surface of the can body 40C and is exposed to the outside of the housing 9. The high-temperature gas generated by the burner 3B rises inside the can body 40C and is discharged to the outside of the housing 9 via the exhaust port 49.

Although the illustration is simplified, the heat transfer tube 41 meanders, including multiple straight sections located inside the can body 40C and multiple folded sections that fold back in an arc shape outside the can body 40C to connect the straight sections. Multiple heat transfer fins 42 are joined to each straight section of the heat transfer tube 41. The internal space of the heat transfer tube 41 forms the internal flow path 4A of the heat exchanger 4.

The combustion device 3 heats the heat transfer tube 41 of the heat exchanger 4 with the high-temperature gas generated by the burner 3B. The heat exchanger 4 exchanges heat between the water passing through the internal flow path 4A and the high-temperature gas generated by the burner 3B, converting the water passing through the internal flow path 4A into hot water.

A bimetal switch 45 is provided at the folded portion of the heat transfer tube 41 to prevent the heat exchanger 4 from running dry.

Above the flame port of the burner 3B in the combustion chamber 3C, there is a temperature fuse 33 to prevent overheating, and a flame rod 34 and an electrode 35 to detect the flame of the burner 3B.

The control unit C1 grasps the state of the combustion device 3 based on the state of the temperature fuse 33 and the detection results of the frame rod 34 and the electrode 35, and can determine whether the combustion device 3 is in a heating disabled state in which it cannot heat the heat exchanger 4.

Specific examples of heating impossible states include a state in which the burner 3B cannot be ignited due to a malfunction of the igniter 3G, a state in which the burner 3B cannot continue proper combustion due to a malfunction of the main gas solenoid valve 30V, the gas proportional valve 30P or the switching gas solenoid valve 31V, and a state in which the burner 3B cannot continue proper combustion due to a malfunction of the combustion fan 3F.

A water filter/drain plug 19 is provided at the lower end of the water supply pipe 10, which is located outside the water heater 1. The upstream end 10U of the water supply pipe 10 is the lower end of the lower end of the water supply pipe 10. The upstream end 10U of the water supply pipe 10 is connected to the junction 50.

Unheated water is supplied to the water supply pipe 10 from an external water supply source (not shown) via a water inlet pipe 55, a check valve 56, and a junction 50. Water supplied from the water supply source passes through the junction 50 upstream of the water supply pipe 10.

An expansion valve 55W is provided downstream of the check valve 56 in the water inlet pipe 55. The expansion valve 55W absorbs the increase in pressure in the water inlet pipe 55 and the junction 50.

The downstream end 10D of the water supply pipe 10 is connected to the inlet of the heat transfer pipe 41 of the heat exchanger 4. The water supply pipe 10 guides water supplied from an external water supply source to the internal flow path 4A.

The portion of the water supply pipe 10 located inside the housing 9 is provided with a check valve 11, a bypass pipe 15, a circulation pump 5, a water volume sensor 70, a water supply thermistor 71, and a water volume servo 13 with a water stop function.

The upstream end of the bypass pipe 15 is connected upstream of the check valve 11 in the water supply pipe 10. The downstream end of the bypass pipe 15 is connected downstream of the check valve 11 in the water supply pipe 10.

The circulation pump 5 is provided in the water supply pipe 10 by being located midway through the bypass pipe 15. When the circulation pump 5 is operated, it pressure-feeds hot water that is upstream of the check valve 11 in the water supply pipe 10 to downstream of the check valve 11 in the water supply pipe 10.

In this embodiment, the circulation pump 5 has a DC motor and a drive circuit that drives the DC motor. The drive circuit precisely controls the DC motor to rotate at the desired rotation speed by adjusting the voltage and current.

The water volume sensor 70 is located downstream of the check valve 11, bypass pipe 15, and circulation pump 5 in the water supply pipe 10, and detects the flow rate of hot and cold water.

Although the illustration is simplified, the water volume sensor 70 has a housing with a mounting portion for mounting it midway along the water supply pipe 10, a flow passage formed in the housing, and an impeller disposed in the flow passage.

The impeller can rotate around an axis parallel to the extension direction of the water supply pipe 10, and has blades that extend in a spiral shape around the axis. The number of revolutions per unit time (seconds) of the impeller increases in proportion to the flow rate of hot water flowing through the water supply pipe 10.

Although not shown in the figure, the water level sensor 70 has a magnet attached to the outer periphery of the impeller and a magnet sensor attached to a location close to the inner wall surface of the flow passage in the housing. The internal contacts of the magnet sensor are disconnected while the magnet is separated during one rotation of the impeller, and switch to a connected state only when the magnet is closest to the magnet, transmitting a single pulse signal.

Therefore, the signal (number of pulses/second) emitted by the water volume sensor 70 increases in proportion to the flow rate of hot and cold water flowing through the water supply pipe 10. The control unit C1 obtains the flow rate of hot and cold water detected by the water volume sensor 70 from the pulse signal (number of pulses/second) emitted by the water volume sensor 70.

The water supply thermistor 71 is located downstream of the water volume sensor 70 in the water supply pipe 10. The temperature sensing part of the water supply thermistor 71 is located inside the water supply pipe 10. The water supply thermistor 71 detects the temperature of the hot water flowing through the water supply pipe 10 and transmits it to the control unit C1.

The water volume servo 13 with water stop function is located downstream of the water supply thermistor 71 in the water supply pipe 10. The water volume servo 13 with water stop function controls the flow rate of hot water flowing through the water supply pipe 10. The water volume servo 13 with water stop function is also capable of stopping the flow of hot water through the water supply pipe 10.

The upstream end 20U of the hot water outlet pipe 20 is connected to the outlet of the heat transfer pipe 41 of the heat exchanger 4. A water hammer buffer valve 29 and an overpressure relief valve 28 are provided at the lower end of the hot water outlet pipe 20, which is located outside the hot water heater 1. The downstream end 20D of the hot water outlet pipe 20 is the lower end of the lower end of the hot water outlet pipe 20. The hot water outlet pipe 20 sends hot water that has passed through the internal flow path 4A to the outside of the hot water heater 1.

The portion of the hot water outlet pipe 20 located inside the housing 9 is provided with a heater 80 and a hot water outlet thermistor 72.

The heater 80 is in close contact with the outer surface of the hot water outlet pipe 20. When electricity is applied to the heater 80, it generates heat and heats the hot water outlet pipe 20 and the hot water inside the hot water outlet pipe 20.

The hot water outlet thermistor 72 is located downstream of the heater 80 in the hot water outlet pipe 20. The temperature-sensing part of the hot water outlet thermistor 72 is located inside the hot water outlet pipe 20. The hot water outlet thermistor 72 detects the temperature of the hot water flowing inside the hot water outlet pipe 20 and transmits it to the control unit C1.

The middle part of the hot water outlet pipe 20 and the middle part of the water supply pipe 10 are connected by a thin fixed bypass pipe 21. The fixed bypass pipe 21 is a pipe for performing so-called bypass mixing, which mixes a portion of the low-temperature hot water flowing through the water supply pipe 10 with the high-temperature hot water heated by the heat exchanger 4.

The upstream end 60U of the hot water distribution pipe 60 is connected to the downstream end 20D of the hot water outlet pipe 20. The downstream end 60D of the hot water distribution pipe 60 is connected to the branch section 63. The hot water distribution pipe 60 supplies the hot water sent out from the hot water outlet pipe 20 to the hot water tap 6 via the branch section 63.

The upstream end 65U of the return pipe 65 is connected to the branch section 63. The downstream end 65D of the return pipe 65 is connected to the junction section 50. The return pipe 65 is provided with a check valve 66. The return pipe 65 returns hot water from the hot water flow pipe 60 to the junction section 50.

The circulation path 7 is formed by the junction 50, the water supply pipe 10, the internal flow path 4A, the hot water outlet pipe 20, the hot water distribution pipe 60, and the return pipe 65. The circulation pump 5 circulates the hot water within the circulation path 7 by operating under the control of the control unit C1.

<Hot water supply operation, instant hot water operation and freeze prevention operation>
The control unit C1 goes into a standby state when the start-up operation of the water heater 1 is performed on the remote control 90, and simultaneously executes the "execution program for instant hot water operation and anti-freeze operation" shown in Figures 2 to 4 and the "use determination program for the hot water tap" shown in Figure 5. This enables the control unit C1 to execute the hot water operation, instant hot water operation, and anti-freeze operation.

As shown in FIG. 5, the hot water supply operation is an operation in which, when the flow rate detected by the water volume sensor 70 reaches or exceeds a predetermined usage judgment flow rate, the circulation pump 5 is stopped and the combustion device 3 is operated to supply hot water from the hot water tap 6.

As shown in FIG. 2, the instant hot water operation is an operation in which, when an instant hot water operation command is received, the circulation pump 5 and the combustion device 3 are operated continuously or intermittently to maintain the hot water in the circulation path 7 at or above a predetermined first temperature.

As shown in Figures 2 to 4, the freeze prevention operation is an operation in which, when the ambient temperature falls below a predetermined second temperature (the ambient temperature outside the water heater 1 detected by the low-sensitivity thermistor 79 is below 3°C), at least the circulation pump 5 of the circulation pump 5 and the combustion device 3 is operated continuously or intermittently to prevent the hot water in the circulation path 7 from freezing.

<Execution program for instant hot water operation and anti-freeze operation>
When the control unit C1 starts the "execution program for instant hot water operation and freeze prevention operation" shown in Figures 2 to 4, it determines in step S101 whether or not an instant hot water operation command has been issued by operating the remote control 90.

If step S101 is "Yes", the control unit C1 proceeds to step S103. On the other hand, if step S101 is "No", the control unit C1 proceeds to step S102 and determines whether the ambient temperature outside the water heater 1 detected by the low-sensitivity thermistor 79 is less than 3°C. Step S102 is a step for determining the conditions for starting anti-freeze operation. 3°C is an example of the "predetermined second temperature" of the present invention.

If the answer is "No" in step S102, the control unit C1 repeats steps S101 and S102. On the other hand, if the answer is "Yes" in step S102, the control unit C1 determines that the conditions for starting anti-freeze operation are met, and proceeds to step S111 shown in FIG. 3.

When the process moves from step S101 to step S103 shown in FIG. 2, the control unit C1 starts the instant hot water operation. Next, the control unit C1 moves to step S104 and sets the first circulation flow rate CF1 = 8 (L/min).

The first circulation flow rate CF1 is the flow rate detected by the water volume sensor 70 when the circulation pump 5 is operating during instant hot water operation. 8 (L/min) is an example of the "predetermined first target flow rate" of the present invention.

Next, the control unit C1 proceeds to step S105, and starts instant hot water combustion using the burner 3B of the combustion device 3 to instantly heat the hot water, and activates the circulation pump 5. This causes hot water to circulate in the circulation path 7, and the circulating hot water is heated in the internal flow path 4A of the heat exchanger 4. The control unit C1 also starts timing the instant hot water pump ON timer.

At this time, the control unit C1 controls the DC motor of the circulation pump 5 to rotate at a desired rotation speed via the drive circuit of the circulation pump 5 so that the first circulation flow rate CF1 becomes the predetermined first target flow rate of 8 (L/min). In addition, when the flow rate detected by the water volume sensor 70 becomes larger or smaller than the first circulation flow rate CF1, the control unit C1 feedback controls the DC motor of the circulation pump 5 to maintain the state of the first circulation flow rate CF1 = 8 (L/min).

The length of the hot water flow pipe 60 and the return pipe 65 varies depending on the installation conditions, such as the relative positions of the hot water heater 1 and the hot water tap 6 installed in a house, etc. Therefore, the flow resistance of the circulation path 7 also varies depending on the installation conditions, and the rotation speed of the DC motor of the circulation pump 5, which sets the first circulation flow rate CF1 = 8 (L/min), also varies depending on the installation conditions.

Next, the control unit C1 proceeds to step S106 and determines whether the temperature of the hot water in the water supply pipe 10 detected by the water supply thermistor 71 is greater than the circulation stop temperature, or whether the instant hot water pump ON timer has elapsed a predetermined time. The circulation stop temperature is determined according to the target hot water temperature set by operating the remote control 90.

If step S106 is "No," i.e., if the temperature of the hot water in the water supply pipe 10 detected by the water supply thermistor 71 is below the circulation stop temperature and the instant hot water pump ON timer has not elapsed the specified time, the control unit C1 repeats step S106.

On the other hand, if step S106 is "Yes," i.e., if the temperature of hot water in the water supply pipe 10 detected by the water supply thermistor 71 is higher than the circulation stop temperature, or if the instant hot water pump ON timer has elapsed a predetermined time, the control unit C1 proceeds to step S107.

When the control unit C1 proceeds to step S107, it stops the instant hot water combustion by the burner 3B of the combustion device 3 and stops the circulation pump 5 as an instant hot water interval. This prevents the hot water in the circulation path 7 from becoming too high above the target hot water temperature. The control unit C1 also starts timing the interval timer.

Next, the control unit C1 proceeds to step S108 and determines whether the temperature of the hot water in the hot water outlet pipe 20 detected by the hot water outlet thermistor 72 is lower than the circulation start temperature, or whether the interval timer has elapsed a predetermined time. The circulation start temperature is determined according to the target hot water supply temperature set by operating the remote control 90, and is lower than the circulation stop temperature. The circulation start temperature is an example of the "predetermined first temperature" of the present invention.

If step S108 returns "No," i.e., if the temperature of the hot water in the hot water outlet pipe 20 detected by the hot water outlet thermistor 72 is equal to or higher than the circulation start temperature, and the interval timer has not yet reached the predetermined time, the control unit C1 repeats step S108.

On the other hand, if step S108 returns "Yes," i.e., if the temperature of the hot water in the hot water outlet pipe 20 detected by the hot water outlet thermistor 72 is lower than the circulation start temperature, or if the interval timer has elapsed a predetermined time, the control unit C1 repeats steps S105 to S108.

The control unit C1 judges whether or not an instruction to stop the instant hot water operation has been given simultaneously while steps S103 to S108 are being executed. If the control unit C1 judges that an instruction to stop the instant hot water operation has been given, it stops the instant hot water operation and returns to step S101. At this time, if steps S105 and S106 are being executed, it stops the instant hot water combustion in the burner 3B and stops the circulation pump 5.

When the process moves from step S102 to step S111 shown in FIG. 3, the control unit C1 starts anti-freeze operation. In this embodiment, the anti-freeze operation includes a non-heated intermittent circulation process shown in steps S113 to S120, a non-heated continuous circulation process shown in steps S131 to S135 in FIG. 4, and a heated circulation process shown in steps S141 to S146.

The non-heated intermittent circulation process is a process in which the circulation pump 5 is operated intermittently while the combustion device 3 is stopped. The non-heated continuous circulation process is a process in which the circulation pump 5 is operated continuously while the combustion device 3 is stopped. The heated circulation process is a process in which the circulation pump 5 and the combustion device 3 are operated continuously.

Next, the control unit C1 proceeds to step S112 shown in FIG. 3 and sets the second circulation flow rate CF2 to 2 (L/min). The control unit C1 sets the second circulation flow rate CF2 to be smaller than the first circulation flow rate CF1.

The second circulation flow rate CF2 is the flow rate detected by the water volume sensor 70 when the circulation pump 5 is operating during anti-freeze operation. 2 (L/min) is an example of the "predetermined second target flow rate" of the present invention.

Next, the control unit C1 proceeds to step S113 and starts the non-heating intermittent circulation process. The control unit C1 then proceeds to step S114 and operates the circulation pump 5 while keeping the burner 3B of the combustion device 3 stopped. This causes hot water to circulate within the circulation path 7. The control unit C1 also starts counting the timer that determines the ON time when the circulation pump 5 is operated intermittently.

At this time, the control unit C1 controls the DC motor of the circulation pump 5 to rotate at a desired rotation speed via the drive circuit of the circulation pump 5 so that the second circulation flow rate CF2 becomes the predetermined second target flow rate of 2 (L/min). In addition, when the flow rate detected by the water volume sensor 70 becomes larger or smaller than the second circulation flow rate CF2, the control unit C1 feedback controls the DC motor of the circulation pump 5 to maintain the state of the second circulation flow rate CF2 = 2 (L/min).

The control unit C1 controls the circulation pump 5 in the non-heated intermittent circulation process so that the second circulation flow rate CF2 is smaller than the first circulation flow rate CF1. More specifically, the control unit C1 controls the circulation pump 5 so that the second circulation flow rate CF2 is a predetermined second target flow rate (2 L/min) that is significantly smaller than the first target flow rate (8 L/min).

Next, the control unit C1 proceeds to step S115 and determines whether or not the circulation path 7 is in a state where hot water cannot circulate. A circulation path 7 is in a state where the hot water distribution pipe 60 or the return pipe 65 is blocked, or the circulation pump 5 has broken down, for example. The control unit C1 can determine that the circulation path 7 is in a state where the water volume sensor 70 cannot detect the flow rate even though the circulation pump 5 is operating, or when error information is transmitted from the drive circuit of the circulation pump 5.

If the answer is "Yes" in step S115, the control unit C1 proceeds to step S123. The processing of steps S123 to S126 will be described later. On the other hand, if the answer is "No" in step S115, the control unit C1 proceeds to step S116.

When the control unit C1 proceeds to step S116, it determines whether the ambient temperature outside the water heater 1 detected by the low-sensitivity thermistor 79 is less than -3°C, or whether the temperature of the hot water in the hot water outlet pipe 20 detected by the hot water outlet thermistor 72 is less than 3°C. Step S116 is a step for determining the conditions for transitioning from the non-heated intermittent circulation process to the non-heated continuous circulation process.

If step S116 is "Yes", that is, if the ambient temperature outside the water heater 1 detected by the low sensitivity thermistor 79 is less than -3°C, or if the temperature of the hot water in the hot water outlet pipe 20 detected by the outlet thermistor 72 is less than 3°C, the control unit C1 proceeds to step S131 shown in FIG. 4. The processing from step S131 onwards will be described later. On the other hand, if step S116 is "No", that is, if the ambient temperature outside the water heater 1 detected by the low sensitivity thermistor 79 is -3°C or higher and the temperature of the hot water in the hot water outlet pipe 20 detected by the outlet thermistor 72 is 3°C or higher, the control unit C1 proceeds to step S117.

When the control unit C1 proceeds to step S117, it determines whether the timer has reached the first time T1. If the answer is "No" in step S117, the control unit C1 repeats steps S115 to S117. On the other hand, if the answer is "Yes" in step S117, the control unit C1 proceeds to step S118.

When the control unit C1 proceeds to step S118, it stops the circulation pump 5. This stops hot and cold water from circulating in the circulation path 7. The control unit C1 also starts counting the timer that determines the OFF time when the circulation pump 5 is operated intermittently.

Next, the control unit C1 proceeds to step S119 and determines whether the ambient temperature outside the water heater 1 detected by the low-sensitivity thermistor 79 is 6°C or higher. Step S119 is a step for determining the conditions for ending the freeze prevention operation.

If the answer is "Yes" in step S119, the control unit C1 ends the freeze prevention operation and proceeds to step S101 shown in FIG. 2 and enters a standby state. On the other hand, if the answer is "No" in step S119, the control unit C1 proceeds to step S120.

When the control unit C1 proceeds to step S120, it determines whether the timer has reached the second time T2. If the answer is "No" in step S120, the control unit C1 repeats steps S119 and S120. On the other hand, if the answer is "Yes" in step S120, the control unit C1 repeats steps S114 to S120.

In other words, the control unit C1 operates the circulation pump 5 intermittently by repeatedly operating the circulation pump 5 for a first time T1 and then stopping it for a second time T2 in steps S114 to S120.

When the process moves from step S116 to step S131 shown in FIG. 4, the control unit C1 starts the non-heating continuous circulation process. Then, the control unit C1 moves to step S132, and the burner 3B of the combustion device 3 is stopped and the circulation pump 5 is kept operating. This allows hot water to continue circulating in the circulation path 7.

In this case, the control unit C1 also feedback controls the circulation pump 5 so that the second circulation flow rate CF2 becomes the predetermined second target flow rate of 2 (L/min).

The control unit C1 controls the circulation pump 5 so that the second circulation flow rate CF2 is smaller than the first circulation flow rate CF1, even in the non-heated continuous circulation process, more specifically so that the second circulation flow rate CF2 is a predetermined second target flow rate (2 L/min) that is significantly smaller than the first target flow rate (8 L/min).

However, as described below, when the control unit C1 changes the second circulation flow rate CF2 to 8 (L/min) in step S150 and then returns to step S131 to resume the non-heated continuous circulation process, the control unit C1 controls the circulation pump 5 to set the second circulation flow rate CF2 to 8 (L/min).

When the process moves from step S132 to step S133, the control unit C1 judges whether or not circulation is not possible. If the answer is "Yes" at step S133, the control unit C1 moves to step S123 shown in FIG. 3. The processing of steps S123 to S126 will be described later. On the other hand, if the answer is "No" at step S133 shown in FIG. 4, the control unit C1 moves to step S134.

When the control unit C1 proceeds to step S134, it determines whether the ambient temperature outside the water heater 1 detected by the low-temperature thermistor 79 is equal to or higher than 0°C. Step S134 is a step for determining the conditions for returning from the non-heated continuous circulation process to the non-heated intermittent circulation process.

If the answer is "Yes" in step S134, the control unit C1 proceeds to step S112 shown in FIG. 3 and starts the non-heated intermittent circulation process. If the second circulation flow rate CF2 was changed to 8 (L/min) in step S150 shown in FIG. 4, the second circulation flow rate CF2 is returned to 2 (L/min) in step S112 shown in FIG. 3. On the other hand, if the answer is "No" in step S134 shown in FIG. 4, the control unit C1 proceeds to step S135.

When the control unit C1 proceeds to step S135, it determines whether the temperature of the hot water in the hot water outlet pipe 20 detected by the hot water outlet thermistor 72 is less than 3°C. Step S135 is a step for determining the conditions for transitioning from the non-heating continuous circulation process to the heating circulation process.

If the answer is "No" in step S135, the control unit C1 repeats steps S133 to S135. On the other hand, if the answer is "Yes" in step S135, the control unit C1 proceeds to step S141.

When the control unit C1 proceeds to step S141, it starts the heating circulation process. Then, the control unit C1 proceeds to step S142, where it starts anti-freeze combustion using the burner 3B of the combustion device 3 and keeps the circulation pump 5 running. This keeps the hot water circulating in the circulation path 7, and the circulating hot water is heated in the internal flow path 4A of the heat exchanger 4.

In this case, the control unit C1 also feedback controls the circulation pump 5 so that the second circulation flow rate CF2 becomes the predetermined second target flow rate of 2 (L/min).

The control unit C1 controls the circulation pump 5 so that the second circulation flow rate CF2 is smaller than the first circulation flow rate CF1, more specifically, so that the second circulation flow rate CF2 is a predetermined second target flow rate (2 L/min) that is significantly smaller than the first target flow rate (8 L/min), even during the heating circulation process.

However, as described below, the control unit C1 changes the second circulation flow rate CF2 to 8 (L/min) in step S150, returns to step S131 to resume the non-heated continuous circulation process, and then controls the circulation pump 5 to set the second circulation flow rate CF2 to 8 (L/min) when transitioning to the heated circulation process.

When the process moves from step S142 to step S143, the control unit C1 judges whether or not circulation is not possible. If the answer is "Yes" at step S143, the control unit C1 moves to step S123 shown in FIG. 3. The processing of steps S123 to S126 will be described later. On the other hand, if the answer is "No" at step S143 shown in FIG. 4, the control unit C1 moves to step S144.

When the control unit C1 proceeds to step S144, it determines the state of the combustion device 3 based on the state of the temperature fuse 33 and the detection results of the frame rod 34 and the electrode 35, and determines whether the combustion device 3 is in a heating disabled state in which it cannot heat the heat exchanger 4.

If the answer is "Yes" in step S144, the control unit C1 proceeds to step S149. The processing of steps S149 and S150 will be described later. On the other hand, if the answer is "No" in step S144, the control unit C1 proceeds to step S145.

When the control unit C1 proceeds to step S145, it determines whether the temperature of the hot water in the water supply pipe 10 detected by the water supply thermistor 71 is greater than 15°C. Step S145 is a step for determining the conditions for returning from the heating circulation process to the non-heating intermittent circulation process.

If the answer is "Yes" in step S145, the control unit C1 proceeds to step S146 and stops anti-freeze combustion by the burner 3B of the combustion device 3. Next, the control unit C1 proceeds to step S112 shown in FIG. 3 and starts the non-heated intermittent circulation process. If the second circulation flow rate CF2 was changed to 8 (L/min) in step S150 shown in FIG. 4, it is returned to 2 (L/min) in step S112 shown in FIG. 3. On the other hand, if the answer is "No" in step S145, the control unit C1 repeats steps S143 to S145.

When the process moves from step S144 to step S149, the control unit C1 stops the freeze prevention combustion by the burner 3B of the combustion device 3. Next, the control unit C1 moves to step S150, sets the second circulation flow rate CF2 = 8 (L/min), and then returns to step S131.

In other words, when the control unit C1 determines in step S144 of the heating circulation process that the heating is not possible, it returns to step S131 via steps S149 and S150 to execute the non-heating continuous circulation process. Then, the control unit C1 controls the circulation pump 5 so that the flow rate (8 L/min) detected by the water volume sensor 70 when it determines that the heating is not possible and executes the non-heating continuous circulation process via steps S149 and S150 is significantly greater than the flow rate (2 L/min) detected by the water volume sensor 70 when it determines that the heating is not possible and executes the heating circulation process without going through steps S149 and S150.

When the process moves from step S115 shown in FIG. 3, step S133 shown in FIG. 4, or step S143 shown in FIG. 4 to step S123 shown in FIG. 3, the control unit C1 stops the circulation pump 5 and stops the operation of circulating hot and cold water in the circulation path 7, since hot and cold water does not circulate in the circulation path 7 even if the circulation pump 5 is operating.

Next, the control unit C1 proceeds to step S124 and energizes the heater 80. In other words, the control unit C1 heats the hot water outlet pipe 20 and the hot water stagnating in the hot water outlet pipe 20 using the heater 80, and transfers the heat upstream and downstream of the hot water outlet pipe 20, while also heating the air in the housing 9, thereby preventing freezing at least inside the water heater 1.

Next, the control unit C1 proceeds to step S125 and determines whether the ambient temperature outside the water heater 1 detected by the low sensitivity thermistor 79 is 6°C or higher. If the answer is "No" in step S125, the control unit C1 repeats step S125. On the other hand, if the answer is "Yes" in step S125, the control unit C1 determines that the possibility of freezing inside the water heater 1 has decreased, proceeds to step S126, and stops applying electricity to the heater 80. The control unit C1 then proceeds to step S101 shown in FIG. 2 and enters a standby state.

<Hot water tap usage determination program>
When the control unit C1 starts the "hot water tap use determination program" shown in FIG. 5, it determines in step S201 whether or not the instant hot water operation is in progress and whether or not the circulation pump 5 is operating.

If the answer is "Yes" in step S201, i.e., if the instant hot water operation is in progress and the circulation pump 5 is operating, the process proceeds to step S202. Then, the control unit C1 sets the predetermined usage determination flow rate to 10 (L/min), and then proceeds to step S206.

The use judgment flow rate (10 L/min) during instant hot water operation and while the circulation pump 5 is operating is a value set based on the first target flow rate (8 L/min) and is a value greater than the first target flow rate (8 L/min). More specifically, the use judgment flow rate (10 L/min) during instant hot water operation and while the circulation pump 5 is operating is a value obtained by adding the first judgment threshold (2 L/min), which is set based on the first target flow rate (8 L/min), to the first target flow rate (8 L/min). In this embodiment, the first judgment threshold (2 L/min) is 1/4 of the first target flow rate (8 L/min).

On the other hand, if the answer is "No" in step S201, the control unit C1 proceeds to step S203 and determines whether or not freeze prevention operation is in progress and whether or not the circulation pump 5 is operating.

If the answer is "Yes" in step S203, i.e., if anti-freeze operation is in progress and the circulation pump 5 is operating, the process proceeds to step S204. Then, the control unit C1 sets the predetermined usage determination flow rate to 2.5 (L/min), and then proceeds to step S206.

The use judgment flow rate (2.5 L/min) during freeze prevention operation and while the circulation pump 5 is operating is a value set based on the second target flow rate (2 L/min), and is a value smaller than the use judgment flow rate (10 L/min) during instant hot water operation and while the circulation pump 5 is operating, and larger than the second target flow rate (2 L/min). More specifically, the use judgment flow rate (2.5 L/min) during freeze prevention operation and while the circulation pump 5 is operating is a value obtained by adding a second judgment threshold (0.5 L/min) set based on the second target flow rate (2 L/min) to the second target flow rate (2.5 L/min). In this embodiment, the second judgment threshold (0.5 L/min) is 1/4 of the second target flow rate (2 L/min). The second judgment threshold (0.5 L/min) is smaller than the first judgment threshold (2 L/min).

On the other hand, if the answer is "No" in step S203, the control unit C1 proceeds to step S205, determines that the circulation pump 5 is stopped, sets the predetermined usage determination flow rate to 1.5 (L/min), and then proceeds to step S206.

The usage judgment flow rate (1.5 L/min) when the circulation pump 5 is stopped is smaller than the usage judgment flow rate (2.5 L/min) during anti-freeze operation and when the circulation pump 5 is operating, and is slightly larger than the minimum detection flow rate of the water volume sensor 70.

When the process proceeds from step S202, step S204, or step S205 to step S206, the control unit C1 determines whether the flow rate detected by the water volume sensor 70 is equal to or greater than a predetermined usage determination flow rate.

If the answer is "No" in step S206, the control unit C1 repeats steps S201 to S206. On the other hand, if the answer is "Yes" in step S206, the control unit C1 determines that the hot water tap 6 has started to be used, and proceeds to step S211 to start hot water supply operation.

At this time, in the "execution program for instant hot water operation and anti-freeze operation" shown in Figures 2 to 4, the control unit C1 ends the instant hot water operation if it is in the instant hot water operation, and ends the anti-freeze operation if it is in the anti-freeze operation, and then proceeds to step S101 shown in Figure 2 and enters a standby state.

Next, the control unit C1 proceeds to step S212 shown in FIG. 5, where it starts hot water combustion using the burner 3B of the combustion device 3, and stops the circulation pump 5 if it is operating. This causes the hot water tap 6 to dispense hot water.

At this time, if the unit is in instant hot water operation, the hot water maintained at or above the circulation start temperature in the circulation path 7 is immediately dispensed from the hot water tap 6. If the unit is in standby or freeze prevention operation, the hot water that is quickly heated in the heat exchanger 4 is dispensed from the hot water tap 6.

Next, the control unit C1 proceeds to step S213 and determines whether the flow rate detected by the water flow sensor 70 is less than the predetermined extinguishing judgment flow rate. The predetermined extinguishing judgment flow rate is less than the usage judgment flow rate (1.5 L/min) when the circulation pump 5 is stopped.

If step S213 is "No", the control unit C1 repeats step S213. On the other hand, if step S213 is "Yes", the control unit C1 determines that use of the hot water tap 6 has ended, and proceeds to step S214 to stop hot water combustion by the burner 3B of the combustion device 3 and end the hot water supply operation. After that, the control unit C1 returns to step S201.

<Action and effect>
In the hot water supply system 100 of the embodiment, the control unit C1 controls the circulation pump 5 so that the second circulation flow rate CF2 related to the anti-freeze operation is smaller than the first circulation flow rate CF1 related to the instant hot water operation, as shown in step S104 of Figure 2 and step S112 of Figure 3.

Specifically, the control unit C1 controls the circulation pump 5 so that the first circulation flow rate CF1 = 8 (L/min) and the second circulation flow rate CF2 = 2 (L/min).

With this configuration, the control unit C1 can set the use determination flow rate for determining whether use of the hot water tap 6 has started while the circulation pump 5 is operating during freeze prevention operation to a value smaller than the use determination flow rate for determining whether use of the hot water tap 6 has started while the circulation pump 5 is operating during instant hot water operation, as shown in steps S202 and S204 of FIG. 5.

Specifically, the usage judgment flow rate (2.5 L/min) during freeze prevention operation and while the circulation pump 5 is operating is significantly smaller than the usage judgment flow rate (10 L/min) during instant hot water operation and while the circulation pump 5 is operating.

As a result, the control unit C1 can quickly determine that use of the hot water tap 6 has begun while the circulation pump 5 is operating during anti-freeze operation, and can quickly heat the cold hot water in the circulation path 7 and supply it from the hot water tap 6.

Note that while it is difficult for the control unit C1 to quickly determine that use of the hot water tap 6 has begun while the circulation pump 5 is operating during instant hot water operation, the hot water in the circulation path 7 is maintained at or above the circulation start temperature, so low-temperature hot water is not dispensed from the hot water tap 6.

The hot water supply system 100 of the embodiment therefore quickly determines that use of the hot water tap 6 has begun, and if the temperature of the hot water in the circulation path 7 is low, it quickly heats it and supplies it from the hot water tap 6, thereby improving the comfort and convenience of the user. The same is true of the hot water heater 1 of the embodiment provided in the hot water supply system 100.

In addition, the hot water supply system 100 and the hot water heater 1 can reduce energy consumption and noise caused by the operation of the circulation pump 5 during anti-freeze operation.

Furthermore, in the hot water supply system 100 and the hot water heater 1, the control unit C1 can control the circulation pump 5 so that the first circulation flow rate CF1 becomes a predetermined first target flow rate (8 L/min) as shown in steps S104 and S105 of Fig. 2, and so that the second circulation flow rate CF2 becomes a predetermined second target flow rate (2 L/min) that is significantly smaller than the first target flow rate (8 L/min) as shown in steps S112 and S114 of Fig. 3 and S132 and S142 of Fig. 4. The use judgment flow rate (10 L/min) during the instant hot water operation and while the circulation pump 5 is operating is a value that is set based on the first target flow rate (8 L/min) and is a value larger than the first target flow rate (8 L/min). In addition, the use judgment flow rate (2.5 L/min) during freeze prevention operation and while the circulation pump 5 is operating is a value that is set based on the second target flow rate (2 L/min), and is smaller than the use judgment flow rate (10 L/min) during instant hot water operation and while the circulation pump 5 is operating, and is larger than the second target flow rate (2 L/min). With this configuration, the control unit C1 can quickly determine that use of the hot water tap 6 has started, and if the temperature of the hot water in the circulation path 7 is low, it can quickly heat the water and supply it from the hot water tap 6 with high reliability, thereby enabling the user's comfort and convenience to be improved with high reliability.

In addition, in the hot water supply system 100 and the hot water heater 1, the freeze prevention operation includes a non-heating continuous circulation process shown in steps S131 to S135 in FIG. 4 and a heating circulation process shown in steps S141 to S146. When the control unit C1 determines that the heating is not possible in step S144 of the heating circulation process, it returns to step S131 via steps S149 and S150 to execute the non-heating continuous circulation process. Then, the control unit C1 controls the circulation pump 5 so that the flow rate (8 L/min) detected by the water volume sensor 70 when determining that the heating is not possible and executing the non-heating continuous circulation process via steps S149 and S150 is significantly larger than the flow rate (2 L/min) detected by the water volume sensor 70 when determining that the heating is not possible and executing the heating circulation process via steps S149 and S150. Here, when the control unit C1 determines that the heating is not possible in the heating circulation process, it cannot execute the hot water supply operation even if it determines that the use of the hot water tap 6 has started. In other words, under conditions where heating is not possible, rapid detection of the use of the hot water tap 6 does not improve the comfort and convenience of the user. Therefore, when the control unit C1 determines that heating is not possible and executes the non-heating continuous circulation process, it increases the flow rate of hot water circulating through the circulation path 7, thereby suppressing the deterioration of anti-freeze performance in a heating-not possible state, which ultimately leads to improved convenience for the user.

Although the present invention has been described above with reference to examples, it goes without saying that the present invention is not limited to the above examples and can be modified as appropriate without departing from the spirit of the invention.

(Modification)
In the hot water supply system with instant hot water function of the modified example, step S150 in Fig. 4 related to hot water supply system 100 of the embodiment is changed to steps S151 to S153 shown in Fig. 6. The other configurations of the hot water supply system with instant hot water function of the modified example are the same as those of hot water supply system 100 of the embodiment.

In the modified example, when the control unit C1 moves from step S149 to step S151, it energizes the heater 80 and operates the circulation pump 5. In other words, the control unit C1 heats the hot water flowing through the hot water outlet pipe 20 and the hot water outlet pipe 20 with the heater 80, and circulates the heated hot water in the circulation path 7, thereby preventing the hot water in the circulation path 7 from freezing.

Next, the control unit C1 proceeds to step S152 and determines whether the ambient temperature outside the water heater 1 detected by the low sensitivity thermistor 79 is 6°C or higher. If the answer is "No" in step S152, the control unit C1 repeats step S152. On the other hand, if the answer is "Yes" in step S152, the control unit C1 determines that the possibility of the hot water in the circulation path 7 freezing has decreased and proceeds to step S153, where it stops applying electricity to the heater 80 and stops the circulation pump 5. The control unit C1 then proceeds to step S101 shown in FIG. 2 and enters a standby state.

Like the hot water supply system 100 of the embodiment, the modified hot water supply system with instant hot water function can quickly determine when the use of the hot water tap 6 has started, and if the temperature of the hot water in the circulation path 7 is low, it can quickly heat it and supply hot water from the hot water tap 6, thereby improving the comfort and convenience of the user.

In the embodiment, the circulation pump 5 is provided in the water supply pipe 10, but the present invention is not limited to this configuration. For example, a configuration in which the circulation pump is provided in the outlet pipe is also included in the hot water supply system with instant hot water function of the present invention. Also included in the hot water supply system with instant hot water function of the present invention is a configuration in which the circulation pump is provided in the hot water supply pipe or return pipe outside the hot water heater with instant hot water function. Furthermore, the hot water supply system with instant hot water function of the present invention is also a configuration in which the hot water heater with instant hot water function has a junction, a downstream portion of the return pipe that connects to the junction, and a circulation pump provided in the downstream portion of the return pipe.

In the embodiment, the water volume sensor 70 is provided in the water supply pipe 10, but the present invention is not limited to this configuration, and the water volume sensor may be provided in the tap pipe. Also, in the embodiment, the water volume sensor 70 has an impeller that can rotate around an axis parallel to the extension direction of the water supply pipe 10, but the present invention is not limited to this configuration. For example, the water volume sensor may have an impeller that can rotate around an axis perpendicular to the extension direction of the water supply pipe or the tap pipe. Also, the water volume sensor is not limited to the impeller type, and may be various types of flow meters such as a float type, ultrasonic type, or electromagnetic type.

In the embodiment, the circulation pump 5 is provided in the water supply pipe 10 by being located midway through the bypass pipe 15, but the present invention is not limited to this configuration. For example, the present invention also includes a configuration in which the bypass pipe 15 in the embodiment is eliminated and the circulation pump 5 is provided directly in the water supply pipe 10 or the hot water outlet pipe 20.

In the embodiment, the heating means is a combustion device 3, but the present invention is not limited to this configuration. For example, the heating means may be an electric heater.

In the embodiment, the low-sensitivity thermistor 79 detects the ambient temperature outside the water heater 1, but the present invention is not limited to this configuration. For example, the ambient temperature may be detected by a temperature sensor provided in the air supply path for supplying air from outside the water heater 1 to the combustion fan 3F in the housing 9.

In the embodiment, the control unit C1 controls the circulation pump 5 so that the second circulation flow rate CF2 is smaller than the first circulation flow rate CF1 by feedback-controlling the DC motor of the circulation pump 5 based on the detection result of the water volume sensor 70, but the present invention is not limited to this configuration. For example, the present invention also includes a configuration in which a trial run is performed during installation and construction of the hot water supply system with instant hot water function of the present invention, the control unit operates a circulation pump having a DC motor to circulate hot water in the circulation path, stores the rotation speed of the DC motor when the first circulation flow rate becomes a predetermined first target flow rate, and stores the rotation speed of the DC motor when the second circulation flow rate becomes a predetermined second target flow rate, and controls the circulation pump so that the second circulation flow rate is smaller than the first circulation flow rate based on the stored rotation speed. In addition, the present invention also includes a configuration in which the circulation pump has an AC motor, and the control unit applies 100% voltage to the AC motor when operating the circulation pump in instant hot water operation, and applies 50% voltage to the AC motor when operating the circulation pump in anti-freeze operation, thereby controlling the circulation pump so that the second circulation flow rate is smaller than the first circulation flow rate.

In the embodiment, the use judgment flow rate during instant hot water operation and while the circulation pump 5 is operating is 10 (L/min), and the use judgment flow rate during freeze prevention operation and while the circulation pump 5 is operating is 2.5 (L/min), but the present invention is not limited to this configuration. For example, the use judgment flow rate during instant hot water operation and while the circulation pump 5 is operating is a value set based on the first target flow rate (8 L/min) and can be changed to a value larger than the first target flow rate (≠ 10 L/min). In addition, the use judgment flow rate during freeze prevention operation and while the circulation pump 5 is operating is a value set based on the second target flow rate (2 L/min), and can be changed to a value smaller than the use judgment flow rate during instant hot water operation and while the circulation pump 5 is operating and larger than the second target flow rate (≠ 2.5 L/min).

In the embodiment, the use judgment flow rate (10 L/min) during instant hot water operation and while the circulation pump 5 is operating is a value obtained by adding a first judgment threshold (2 L/min) set based on the first target flow rate (8 L/min) to the first target flow rate (8 L/min), and the first judgment threshold (2 L/min) is 1/4 of the first target flow rate (8 L/min), but the present invention is not limited to this configuration. For example, the first judgment threshold can be set by adding, subtracting, subtracting, dividing, etc. the first target flow rate.

In the embodiment, the use judgment flow rate (2.5 L/min) during anti-freeze operation and while the circulation pump 5 is operating is a value obtained by adding a second judgment threshold (0.5 L/min) set based on the second target flow rate (2 L/min) to the second target flow rate (2.5 L/min), and the second judgment threshold (0.5 L/min) is 1/4 of the second target flow rate (2 L/min), but the present invention is not limited to this configuration. For example, the second judgment threshold can be set by adding, subtracting, subtracting, dividing, etc. the second target flow rate. The second judgment threshold may be equal to the first judgment threshold.

In the embodiment, if the control unit C1 determines in step S144 of the heating circulation process that the heating is not possible, it changes the second circulation flow rate CF2 to 8 (L/min) in step S150, but the present invention is not limited to this configuration. For example, the control unit C1 may change the second circulation flow rate CF2 in step S150 to a value greater than 2 (L/min) and different from 8 (L/min).

The present invention can be used, for example, in hot water systems that include a water heater with a hot water supply function and an instant hot water function, a water heater with a hot water supply function, an instant hot water function, and a bath reheating function, and a hot water heater with a hot water supply function, an instant hot water function, and a heating function that circulates hot water between the hot water supply function and the heating device.

100...Hot water supply system with instant hot water function 1...Hot water heater with instant hot water function 4A...Internal flow path 4...Heat exchanger 3...Heating means (combustion device)
10...Water supply pipe 20...Hot water outlet pipe 50...Confluence section 6...Hot water tap 60...Hot water distribution pipe 65...Return pipe 5...Circulation pump 70...Water volume sensor C1...Control section 7...Circulation path CF1...First circulation flow rate CF2...Second circulation flow rate

Claims (4)

A heat exchanger having an internal flow path;
A heating means for heating the heat exchanger;
A water supply pipe that guides water supplied from an external water supply source to the internal flow path;
A hot water outlet pipe that delivers hot water that has passed through the internal flow path;
a confluence portion through which water supplied from the water supply source passes upstream of the water supply pipe;
A hot water tap and
a hot water distribution pipe that supplies the hot water sent from the hot water outlet pipe to the hot water tap;
A return pipe for returning hot water from the hot water distribution pipe to the junction;
A circulation pump provided in the water supply pipe, the hot water outlet pipe, the hot water distribution pipe, or the return pipe;
A water flow sensor provided in the water supply pipe, the hot water outlet pipe, or the hot water distribution pipe to detect a flow rate of hot water;
A control unit;
Equipped with
A circulation path is formed by the junction, the water supply pipe, the internal flow path, the hot water outlet pipe, the hot water distribution pipe, and the return pipe,
The circulation pump circulates hot and cold water within the circulation path,
When the flow rate detected by the water volume sensor becomes equal to or greater than a predetermined use determination flow rate, the control unit stops the circulation pump and operates the heating means to supply hot water from the hot water tap,
When an instant hot water operation command is received, the control unit continuously or intermittently operates the circulation pump and the heating means to perform instant hot water operation to maintain the hot water in the circulation path at a predetermined first temperature or higher,
The control unit is configured to perform a freeze prevention operation to prevent freezing of hot water in the circulation path by continuously or intermittently operating at least the circulation pump of the circulation pump and the heating means when the ambient temperature becomes lower than a predetermined second temperature.
The control unit controls the circulation pump so that the second circulation flow rate, which is the flow rate detected by the water volume sensor when the circulation pump is operating during the anti-freeze operation, is smaller than the first circulation flow rate, which is the flow rate detected by the water volume sensor when the circulation pump is operating during the instant hot water operation. the control unit is capable of controlling the circulation pump so that the first circulation flow rate becomes a predetermined first target flow rate and so that the second circulation flow rate becomes a predetermined second target flow rate that is smaller than the first target flow rate;
The use determination flow rate during the instant hot water operation and the operation of the circulation pump is a value set based on the first target flow rate and is a value greater than the first target flow rate,
A hot water supply system with instant hot water function as described in claim 1, wherein the usage judgment flow rate during the anti-freeze operation and when the circulation pump is operating is a value set based on the second target flow rate, and is smaller than the usage judgment flow rate during the instant hot water operation and when the circulation pump is operating, and is greater than the second target flow rate. The freeze prevention operation includes a non-heating continuous circulation step of continuously operating the circulation pump while the heating means is stopped;
A heating and circulating step of continuously operating the circulation pump and the heating means,
The control unit is configured to be able to determine whether or not the heating means is in a heating disabled state in which the heating means cannot heat the heat exchanger,
When the control unit determines that the heating is not possible in the heating circulation step, the control unit executes the non-heating continuous circulation step,
The hot water supply system with instant hot water function as described in claim 1, wherein the control unit controls the circulation pump so that the flow rate detected by the water volume sensor when it is determined that the heating is not possible and the non-heating continuous circulation process is executed is greater than the flow rate detected by the water volume sensor when it is determined that the heating is not possible and the heating circulation process is executed. A hot water heater with an instant hot water function provided in the hot water supply system with an instant hot water function according to any one of claims 1 to 3,
the heat exchanger, the heating means, the water supply pipe, the hot water outlet pipe, the circulation pump, the water volume sensor, and the control unit;
The circulation pump is provided in the water supply pipe or the hot water outlet pipe,
A hot water heater with an instant hot water function, characterized in that the junction, the hot water tap, the hot water distribution pipe, and the return pipe are installed outside the hot water heater with an instant hot water function.

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