JP7803306B2 - Hot water system - Google Patents

Description

This disclosure relates to a hot water supply system, and more specifically to a hot water supply system equipped with a storage tank-type hot water heater.

Patent Document 1 below discloses a heat source device as a hot water supply system. This heat source device is configured so that the set temperature of the hot water supplied to the hot water tap (hereinafter referred to as the "hot water set temperature") can be changed not only by operating a remote control installed inside the home, but also by remote control from an external communication terminal located outside the home.

Japanese Patent Application Laid-Open No. 2016-8723

In the above-mentioned patent document 1, the bather can set the bathroom priority mode using the remote control, which prohibits the hot water temperature setting from being changed using an external communication terminal. This prevents the user from taking a shower or other bath at an unintended temperature.

However, if the bathroom priority mode is temporarily disabled and then forgotten to be enabled, it becomes possible to change the hot water temperature setting via remote control from an external communications terminal. In this case, the user may not be aware that the hot water temperature has been changed, and as a result, there is a risk that the user may end up bathing in water at an unintended temperature.

This disclosure has been made to solve the above-mentioned problems. The purpose of this disclosure is to provide a hot water supply system that allows the user to recognize changes to the hot water supply temperature setting, even if the change is made by remote control from an external communication terminal outside the home.

The hot water supply system of the present disclosure comprises a hot water supply means for supplying hot water into the home, a remote control placed within the home for notifying the hot water supply means of its set hot water temperature and operating status, and a communication means capable of communicating with an external communication terminal outside the home; when the hot water supply set temperature is changed from the external communication terminal, if the hot water supply function of the hot water supply means is in use, the system waits until the hot water supply function is no longer in use, and when the hot water supply function is no longer in use, the remote control notifies the user of the change in the hot water supply set temperature that was made while the hot water supply function was in use, and changes the actual hot water supply temperature of the hot water supply means .

According to the present disclosure, even if the hot water supply temperature setting is changed by remote control from an external communication terminal, the change in the hot water supply temperature setting is notified by the remote control, allowing users in the home to be aware of the change in the hot water supply temperature setting.

1 is a schematic diagram showing an example of the configuration of a hot water supply system according to a first embodiment. 10 is a flowchart for explaining an operation when a hot water supply setting temperature is changed from an external communication terminal in the first embodiment.

Embodiments of the present disclosure will be described below with reference to the drawings. Note that common elements in each drawing will be assigned the same reference numerals, and duplicate explanations will be omitted.

Embodiment 1.
FIG. 1 is a schematic diagram showing an example of the configuration of a hot water supply system according to a first embodiment. The hot water supply system 1 includes a storage type hot water heater 2. The storage type hot water heater 2 includes a heat pump unit (hereinafter referred to as an "HP unit") 3 that utilizes a heat pump cycle, and a tank unit 4. The storage type hot water heater 2 also includes a kitchen remote control 50 installed in the kitchen of the home, and a bathroom remote control 61 installed in the bathroom 6 of the home in which a bathtub 60 is located. The HP unit 3 and the tank unit 4 are connected via an HP supply pipe 11, an HP return pipe 12, and electrical wiring (not shown). The HP unit 3 and the tank unit 4 constitute hot water supply means having a hot water supply function for supplying hot water to the home.

The HP unit 3 functions as a heating means for heating low-temperature water guided from a hot water storage tank 41 (described below) provided in the tank unit 4. The HP unit 3 includes a refrigerant circuit in which a compressor 31, a water-refrigerant heat exchanger 32, an expansion valve 33, and an air heat exchanger 34 are connected in a ring shape by refrigerant circulation piping 35, and this refrigerant circuit forms a heat pump cycle. The water-refrigerant heat exchanger 32 exchanges heat between the refrigerant flowing through the refrigerant circulation piping 35 and the low-temperature water guided from the tank unit 4.

The tank unit 4 contains the following components and piping: a hot water storage tank 41, a pressure reducing valve 42, a heat source pump P1, a bath heat exchanger 43, a bath circulation pump P2, a bath return temperature sensor S1, a bath supply temperature sensor S2, a water flow detection sensor S3, a water level sensor S4, a general hot water supply mixing valve 44, a bath mixing valve 45, a bath solenoid valve 46, a bath flow rate sensor S5, a hot water tap 47, and a general hot water supply flow rate sensor S6. The tank unit 4 also includes a first water supply pipe 51a (9a), a second water supply pipe 51b, a third water supply pipe 51c, a water outlet pipe 52, a first bypass pipe 53a, a second bypass pipe 53b, a hot water inlet pipe 54a, a hot water outlet pipe 54b, a booster heating connection pipe 54c, a heat recovery connection pipe 54d, a hot water supply pipe 55, a first hot water supply pipe 55a, a second hot water supply pipe 55b, a hot water supply pipe 56, a bath supply pipe 57, and a bath return pipe 58.

The hot water storage tank 41 stores hot water. The hot water storage tank 41 is provided with a water inlet 41a, a water outlet 41b, a hot water inlet 41c, a hot water inlet 41d, and a heat recovery outlet 41e. A third water supply pipe 51c is connected to the water inlet 41a located at the bottom of the hot water storage tank 41. Water supplied from a water source such as a tap is adjusted to a predetermined pressure by a pressure reducing valve 42 and flows into the hot water storage tank 41 through the third water supply pipe 51c. A hot water supply pipe 55 and a hot water delivery pipe 56 are connected to the hot water inlet 41d located at the top of the hot water storage tank 41 to supply hot water stored in the hot water storage tank 41 to the outside of the hot water storage type water heater 2 (bathroom 6). Hot water stored in the hot water storage tank 41 flows into the hot water storage tank 41 through the hot water inlet 41d, where high-temperature water heated by the HP unit 3 flows in, and low-temperature water from the third water supply pipe 51c flows in through the water inlet 41a, creating a temperature difference between the top and bottom. Multiple hot water temperature sensors 411, 412 are attached at different heights to the surface of the hot water storage tank 41. The control unit 40, described below, detects the temperature distribution of the hot water in the hot water storage tank 41 using the hot water temperature sensors 411, 412 to determine the amount of hot water remaining in the hot water storage tank 41, and then controls the start and stop of the hot water boiling operation in the hot water storage tank 41 by the HP unit 3.

The heat source pump P1 is a pump for circulating hot water through the various pipes described above within the tank unit 4, and is installed on the HP supply pipe 11.

The bath heat exchanger 43 is a heat exchanger that uses high-temperature hot water supplied from the hot water storage tank 41 and the HP unit 3 to heat the water to be heated (such as bath water or heating water) on the secondary side. In this embodiment, the secondary side configuration of the bath heat exchanger 43 is described using the bath supply pipe 57 and bath return pipe 58, which circulate the hot water in the bathtub 60 of the bathroom 6, as an example. The bath heat exchanger 43 is installed midway between the bath supply pipe 57 and the bath return pipe 58. A bath circulation pump P2, a bath return temperature sensor S1, a bath supply temperature sensor S2, a water flow detection sensor S3, and a water level sensor S4 are installed midway between the bath supply pipe 57 and the bath return pipe 58. The bath circulation pump P2 is a pump that circulates bath water. The bath return temperature sensor S1 detects the temperature of the bathwater leaving the bathtub 60. The bath supply temperature sensor S2 detects the temperature of the hot water after heat exchange that leaves the bath heat exchanger 43. The water flow detection sensor S3 determines whether the hot water is circulating. The water level sensor S4 detects the water level in the bathtub 60. The bathtub 60, bath return pipe 58, and bath supply pipe 57 form a circulation circuit, and this circulation circuit is referred to as the "bath circulation circuit."

One end of the first water supply pipe 51a is connected to a water source such as a tap, and the other end of the first water supply pipe 51a is connected to the second water supply pipe 51b and the third water supply pipe 51c via the pressure reducing valve 42, forming a "water supply pipeline." The second water supply pipe 51b branches off midway and is connected to the general hot water supply mixing valve 44 and the bath mixing valve 45, respectively. The hot water supply pipe 55 also branches off midway and is connected to the general hot water supply mixing valve 44 and the bath mixing valve 45, respectively. A bath solenoid valve 46 and a bath flow sensor S5 are provided midway along the second hot water supply pipe 55b. The bath solenoid valve 46 opens and closes the second hot water supply pipe 55b. The bath flow sensor S5 detects the flow rate of hot water passing through the second hot water supply pipe 55b.

The general hot water supply mixing valve 44 and the bath mixing valve 45 adjust the flow rate ratio between high-temperature hot water supplied from the hot water supply pipe 55 and low-temperature water supplied from the second water supply pipe 51b to generate hot water at the general hot water supply temperature set or changed by the user via the kitchen remote control 50, bathroom remote control 61, or external communication terminal 70, and supply the hot water to the first hot water supply pipe 55a and the second hot water supply pipe 55b, respectively. The hot water adjusted by the general hot water supply mixing valve 44 is supplied to the user's shower 63, faucet, or other faucet (not shown) via the first hot water supply pipe 55a, the hot water tap 47, and the external hot water supply pipe 62. The general hot water supply flow rate at this time can be detected by the general hot water supply flow sensor S6 installed on the first hot water supply pipe 55a. When there is a general hot water supply flow rate, it is determined that general hot water is being supplied and the hot water supply function is in use. Meanwhile, hot water adjusted to the set temperature by the bath mixing valve 45 is supplied to the bathtub 60 from the second hot water supply pipe 55b via the bath solenoid valve 46, the bath flow sensor S5, the bath supply pipe 57, and the bath return pipe 58. The bath hot water supply flow rate at this time can be detected by the bath flow sensor S5. When there is a bath hot water supply flow rate, it is determined that bath hot water is being supplied and the hot water supply function is being used.

The tank unit 4 has a built-in control unit 40. The operation of the various components, valves, pumps, etc. provided in the HP unit 3 and tank unit 4 is controlled by the control unit 40, which is electrically connected to them.

The control unit 40, the kitchen remote control 50, and the bathroom remote control 61 are connected to each other so that they can communicate with each other. Each remote control 50, 61 is equipped with a display 50a, 61a that displays information such as the status of the hot water supply system 1, as well as controls such as switches operated by the user, a speaker, a microphone, and other components (not shown). Each remote control 50, 61 also has a volume control function. The bathtub stopper 60a installed in the bathtub 60 is electrically connected to the control unit 40. This allows the control unit 40 to check the open/closed state of the bathtub stopper 60a and issue instructions to open or close it. The control unit 40 is also connected to an external communication device 7, enabling communication via an external line. The external line is, for example, an Internet line via a broadband router in the home. For external line communication, the control unit 40 is connected to a cloud server (not shown) to send and receive information such as whether or not the hot water storage type hot water heater 2 is providing general hot water, the general hot water setting temperature, whether or not the bath water heater is providing hot water, the bath water setting temperature, and the identification information (ID) of the operator of the external communication terminal 70.

Each function of the control unit 40 may be realized by multiple devices working together, or by a single device. Furthermore, at least some of the functions of the control unit 40 may be implemented on a server or the like on an external network.

Next, the operation of the hot water supply system 1 will be described. First, the bath filling process will be described. Bath filling is started by the user operating the bathroom remote control 61. When bath filling begins, the bathtub 60 is supplied with the amount of hot water set at the hot water supply temperature setting. After the set amount of hot water has been supplied, automatic bath operation continues, maintaining a constant bathtub 60 temperature. Automatic bath operation operates the bath circulation pump P2 at regular intervals (for example, 10 minutes) to circulate the water from the bathtub 60 through the bath circulation circuit. At this time, the bathtub water temperature is detected by the bath return temperature sensor S1. If the bathtub temperature is lower than the set temperature, reheating of the bathtub water begins, and if the bathtub temperature rises to the set temperature, reheating is stopped. Automatic bath operation can be stopped manually by the user when exiting the bath, or it will continue to operate until the set time has elapsed.

Figure 2 is a flowchart showing the operation when the hot water supply setting temperature is changed from the external communication terminal 70.

In step S1, the external communication terminal 70 checks whether the general hot water supply temperature setting or the bath hot water supply temperature setting has been changed. If the general hot water supply temperature setting or the bath hot water supply temperature setting has been changed, the process proceeds to step S2; if there has been no change, the process waits in step S1. Note that in step S1, a limit may be placed on the range of temperature setting changes made from the external communication terminal 70. This is to ensure that the temperature change range does not cause discomfort to home hot water users, even if they do not notice the setting change made from the external communication terminal 70. In other words, the process may be configured to proceed to step S2 if the change in the hot water supply temperature setting from the external communication terminal 70 exceeds a predetermined upper limit or falls below a predetermined lower limit.

In step S2, it is confirmed whether the hot water function is being used. In step S1, when the general hot water setting temperature is changed using the external communication terminal 70, it is determined that the hot water function is being used if the general hot water flow rate is present. In step S1, when the bath hot water setting temperature is changed, it is determined that the hot water function is being used if the bath hot water flow rate is present. If the hot water function is not being used, proceed to step S3. If the hot water function is being used, step S2 waits until the hot water function is no longer in use, thereby deferring (prohibiting) the change to the actual hot water temperature. This is to prevent users of the hot water function in the home from bathing in water at an unintended hot water temperature if the hot water setting temperature is changed while the hot water function is in use. Note that in step S2, if the hot water function is being used, it waits until the hot water heater is no longer in use. However, if the hot water function is being used, this routine may be temporarily terminated without changing the hot water setting temperature.

In step S3, the kitchen remote control 50 and bathroom remote control 61 notify the user that the hot water temperature setting has been changed. By providing text guidance on the display units 50a and 61a of the remote controls 50 and 61, as well as sound and voice alerts, the user in the home can be made aware that the hot water temperature setting has been changed. Once the alert is complete, the process proceeds to step S4. When issuing an alert via the remote controls 50 and 61, the operator of the external communication terminal 70 may be managed using an ID (identification information) or the like, and the ID information may be transmitted to the remote controls 50 and 61. The content of the alert on the remote controls 50 and 61 may be changed based on the ID information. In other words, the content of the alert may be changed depending on the operator of the change. For example, by providing a voice alert indicating that the operation was performed by a user name registered in the ID information, the operator of the external communication terminal 70 becomes clear, improving usability. Furthermore, the volume is set for each remote control 50, 61, and even if the remote controls 50, 61 are set to no volume, an alarm or voice can be emitted to notify the user that a remote operation has been performed, increasing the frequency with which the user notices and ensuring ease of use.

Furthermore, in step S3, when issuing an alert via remote controllers 50 and 61, an alert may be issued if the hot water temperature setting change is above a predetermined temperature (e.g., 60°C), but not if it is below the predetermined temperature. Alternatively, an alert may be issued if the hot water temperature setting change is below a predetermined value (e.g., 15°C), but not if it exceeds the predetermined temperature. This not only prevents excessive alerts due to setting changes and eliminates annoyance, but also makes it possible to alert users in the home to an extremely high or low setting that would cause discomfort if the user were not aware of the setting change, by issuing an alert.

Furthermore, in step S3, the time period during which the notification is made may be limited. For example, sound or audio notification from the remote control 50, 61 may be prohibited (no notification sound is emitted) between 11pm and 7am, which is the time period during which people typically go to bed at night. This prevents the remote control 50, 61 from suddenly emitting a notification sound while the user is asleep at night, which may cause suspicion, surprise, or disturbance to the user's sleep.

Furthermore, in step S3, the control unit 40 may be provided with an alarm switching means that can set whether or not to issue an audio alarm in response to a setting change from the external communication terminal 70. This is because, for example, if a person lives alone, the person who changes the settings from the external communication terminal 70 and the person who uses the hot water supply are the same person, so an alarm sound is unnecessary, and by setting the alarm sound to not be issued, it is possible to prevent the annoyance of the alarm.

In step S4, the hot water supply setting temperature is updated. If the general hot water supply setting temperature is changed in step S1, the general hot water supply setting temperature is updated, and if the bath hot water supply setting temperature is changed, the bath hot water supply setting temperature is updated. Then, proceed to step S5.

In step S5, it is confirmed whether the hot water supply function is being used. When it is determined in step S1 that an operation to change the general hot water supply setting temperature has been performed, if there is a general hot water supply flow rate, it is determined that the hot water supply function is being used. When it is determined in step S1 that an operation to change the bath hot water supply setting temperature has been performed, if there is a bath hot water supply flow rate, it is determined that the hot water supply function is being used. If the hot water supply function is being used, proceed to step S6; if the hot water supply function is not being used, it waits in step S5 until it is determined that the hot water supply function is being used.

In step S6, the remote controller 50, 61 notifies the user that the hot water supply temperature setting has changed. In addition to text guidance on the display 50a, 61a of the remote controller 50, 61, the notification is made by sound and voice, allowing the user who starts using the hot water supply function to be aware that the hot water supply temperature setting has changed. Although the notification is made by the remote controller 50, 61 in step S3, in consideration of the possibility that the user may not be near the remote controller 50, 61 at the time of the notification or may forget, the change can be re-notified when the hot water supply function is started, ensuring that the user is aware of the change in the hot water supply temperature setting and improving usability. In particular, when using the hot water supply function, the user is inside the home, and the re-notification by the remote controller 50, 61 installed inside the home ensures that the user is aware of the change, which is effective.

As explained above, according to this embodiment, when the hot water supply temperature setting for general hot water supply or hot water filling is changed from the remote external communication terminal 70, the change is notified via the remote controllers 50, 61, allowing the user to be aware that the hot water supply temperature setting has changed, thereby providing a user-friendly hot water supply system 1.

In the flowchart shown in FIG. 2, the use of the hot water supply function when the bath hot water supply temperature setting is changed is determined based on the presence or absence of the bath hot water supply flow rate. However, this may also include the use of the hot water supply function during automatic bath operation. In other words, the use of the hot water supply function may be determined during automatic bath operation. While this embodiment illustrates the change of the general hot water supply temperature setting and the change of the bath hot water supply temperature setting, an audible alert may also be issued when the bath hot water volume setting is changed from the external communication terminal 70. The "alert sound" for a normal setting change on the remote control may be different from the "alert sound" for a setting change from the external communication terminal 70. For example, when a setting change is made from the remote control 50 or 61, the alert may be "The hot water supply temperature has been changed to 42 degrees," whereas when a setting change is made from the external communication terminal 70, the alert may be "The hot water supply temperature has been changed to 42 degrees from the outside (from the external communication terminal 70)." This allows the user to more easily recognize (understand) that a change has been made from the external communication terminal 70. Furthermore, a unique "alert sound" may be played before the "change notification" only when the setting is changed from the external communication terminal 70. For example, when the setting is changed from the remote controllers 50 and 61, the notification may say "The hot water supply temperature has been changed to 42 degrees," whereas when the setting is changed from the external communication terminal 70, the notification may say "Beep, the hot water supply temperature has been changed to 42 degrees." This allows the user to more easily understand that the change has been made from the external communication terminal 70.

The above describes an exemplary embodiment of the hot water supply system of the present disclosure, but as mentioned above, the present disclosure is not limited to the above embodiment.

Note that two or more of the features of the above-described embodiments that can be combined may be combined. The various aspects of this disclosure are summarized below as appendices.

(Appendix 1)
A hot water supply means for supplying hot water to the house;
a remote controller that is placed in the home and that notifies the hot water supply setting temperature and the operating state of the hot water supply means;
A communication means capable of communicating with an external communication terminal outside the home;
a control unit that notifies the user of a change in the hot water supply temperature setting via the remote controller when the hot water supply temperature setting is changed by operating the external communication terminal.
(Appendix 2)
A hot water supply system as described in Appendix 1, in which the control unit changes the actual hot water supply temperature of the hot water supply means after the notification is completed by the remote control when the hot water supply set temperature is changed by operating the external communication terminal.
(Appendix 3)
The hot water supply system according to claim 1 or 2, wherein the control unit prohibits a change in the hot water supply setting temperature when the hot water supply function of the hot water supply means is in use.
(Appendix 4)
A hot water supply system as described in any one of Appendix 1 to Appendix 3, wherein when starting to use the hot water supply function of the hot water supply means, if the hot water supply setting temperature has changed since the last time the hot water supply function was used, the control unit notifies the user via the remote control that there has been a change since the last time the hot water supply function was used.
(Appendix 5)
The hot water supply system according to any one of claims 1 to 4, wherein the control unit changes the content of the notification on the remote control depending on the source of the change operation when the hot water supply setting temperature is changed.
(Appendix 6)
6. The hot water supply system according to claim 1, wherein the remote controller is capable of setting a volume.
The control unit issues a notification with sound even when the volume setting of the remote control is set to no volume.
(Appendix 7)
A hot water supply system as described in any one of Appendix 1 to Appendix 6, wherein the control unit emits an alarm sound from the remote control only when the value of the hot water supply setting temperature to be changed exceeds a predetermined upper limit value when the hot water supply setting temperature is changed from the external communication terminal.
(Appendix 8)
A hot water supply system as described in any one of Appendix 1 to Appendix 6, wherein the control unit emits an alarm sound from the remote control only when the value of the hot water supply setting temperature to be changed falls below a predetermined lower limit value when the hot water supply setting temperature is changed from the external communication terminal.
(Appendix 9)
The hot water supply system according to any one of claims 1 to 8, wherein the control unit prohibits the remote controller from making an alarm sound during a predetermined time period at night.
(Appendix 10)
The hot water supply system according to any one of claims 1 to 9, wherein the control unit includes an alarm switching means that can set whether or not to issue an alarm sound.

1...Hot water supply system, 11...HP forward piping, 12...HP return piping, 2...Hot water storage type hot water heater, 3...Heat pump unit, 31...Compressor, 32...Water-refrigerant heat exchanger, 33...Expansion valve, 34...Air heat exchanger, 35...Refrigerant circulation piping, 4...Tank unit, 40...Control unit, 41...Hot water storage tank, 41a...Water inlet, 41b...Water outlet, 41c...Hot water inlet, 4 1d...hot water inlet outlet, 41e...heat recovery outlet, 42...pressure reducing valve, 43...bath heat exchanger, 44...general hot water mixing valve, 45...bath mixing valve, 46...bath solenoid valve, 47...hot water tap, 48a...three-way valve, 48b...heat recovery switching valve, 49...four-way valve, 50...kitchen remote control, 50a...display unit, 51a...first water supply pipe, 51b...second water supply pipe, 51c...third water supply pipe Piping, 52...water outlet piping, 53a...first bypass piping, 53b...second bypass piping, 54a...hot water inlet piping, 54b...hot water outlet piping, 54c...reheating connection piping, 54d...heat recovery connection piping, 55a...first hot water supply piping, 55b...second hot water supply piping, 56...hot water supply piping, 57...bathroom supply piping, 58...bathroom return piping, 6...bathroom, 60...bathtub, 60a...bathtub stopper, 61...bathroom remote control, 61a...display, 62...external hot water supply piping, 63...shower, 7...external communication device, 70...external communication terminal, P1...heat source pump, P2...bathroom circulation pump, S1...bathroom return temperature sensor, S2...bathroom supply temperature sensor, S3...water flow detection sensor, S4...water level sensor, S5...bathroom flow rate sensor, S6...general hot water supply flow rate sensor

Claims (10)

A hot water supply means for supplying hot water to the house;
a remote controller that is placed in the home and that notifies the hot water supply setting temperature and the operating state of the hot water supply means;
A communication means capable of communicating with an external communication terminal outside the home;
A hot water supply system comprising: a control unit that, when the hot water supply setting temperature is changed by operating the external communication terminal, if the hot water supply function of the hot water supply means is in use, waits until the hot water supply function is no longer in use, and when the hot water supply function is no longer in use, notifies the remote control of the change in the hot water supply setting temperature that was made while the hot water supply function was in use, and changes the actual hot water supply temperature of the hot water supply means. The hot water supply system according to claim 1 , wherein the control unit changes the actual hot water supply temperature of the hot water supply means after the notification is completed by the remote controller. 2. The hot water supply system according to claim 1 , wherein the control unit prohibits a change in the actual hot water temperature of the hot water supply unit when the hot water supply function of the hot water supply unit is in use. The hot water supply system of claim 1, wherein when the hot water supply function of the hot water supply means is started, if the hot water supply setting temperature has changed since the last time the hot water supply function was used, the control unit notifies the user via the remote control that a change has occurred since the last time the hot water supply function was used. The hot water supply system of claim 1, wherein the control unit changes the content of the notification on the remote control when the hot water supply set temperature is changed depending on the source of the change operation. 2. The hot water supply system according to claim 1 , wherein the remote controller is capable of setting a volume,
The control unit issues a notification with sound even when the volume setting of the remote control is set to no volume. The hot water supply system of claim 1, wherein the control unit emits an alarm sound from the remote control only when the value of the hot water supply setting temperature to be changed exceeds a predetermined upper limit value when the hot water supply setting temperature is changed from the external communication terminal. The hot water supply system of claim 1, wherein the control unit emits an alarm sound from the remote control only when the hot water supply setting temperature is changed from the external communication terminal and the value of the changed hot water supply setting temperature falls below a predetermined lower limit value. The hot water supply system according to claim 1 , wherein the control unit prohibits the remote controller from making an alarm sound during a predetermined time period at night. The hot water supply system according to claim 1 , wherein the control unit includes an alarm switching unit that can set whether or not to issue an alarm sound.