JP3233478B2 - Hot water storage type electric water heater control device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention controls the opening / closing of a heater relay having an opening / closing contact disposed in an energizing path between a heater and a power supply by an ON command and an OFF command from a heater power control means. The present invention relates to a control device for a hot water storage electric water heater.

[0002]

2. Description of the Related Art FIG. 7A is a schematic view of a main part of an energization circuit of a conventional control device of a hot water storage type electric water heater in which one heater H is disposed in a hot water storage tank. For the relays and switches, only the configuration of the contacts is shown. When the heater power supply control means (not shown) gives an ON command to the heater relay in accordance with a predetermined operation mode, the open / close contact of the heater relay HR closes, and power is supplied to the heater H.
When an off command is given to the heater relay HR from the heater power supply control means, the open / close contact is opened and power supply to the heater H is stopped. When the temperature of the hot water in the hot water storage tank reaches a preset upper limit temperature, the over-elevation thermoswitch TSW opens a normally closed contact and stops energizing the heater H. The over-elevated thermoswitch TSW is not controlled by the heater energization control means, and it is common to manually close the normally closed contact after the contact is opened.

FIG. 7B is a schematic view of a main part of an energization circuit of a conventional control device of a hot water storage type electric water heater of a type in which two heaters H1 and H2 are arranged at a lower portion and an upper portion inside a hot water storage tank. FIG. Normally, the switching type first heater relay HR1 is switched to the side for energizing the lower heater H1, and the opening and closing of the opening and closing contact of the second heater relay HR2 is controlled by the output from the heater energization control means. . When additional heating is required, the contact point of the first heater relay HR1 is switched to the side to energize the upper heater H2 by the output from the heater energization control means, and energization to the upper heater H2 is executed. After the reheating, the first heater relay HR1 is switched to the side for energizing the lower heater H1.

[0004]

SUMMARY OF THE INVENTION Heater relays HR, H
Since the switching frequency of R1 and HR2 is high, there is a high possibility that a malfunction occurs due to wear and fusion of the switching contacts, disconnection of the exciting coil, and the like. When an operation abnormality occurs in the heater relay in the conventional device, the following problem occurs. First, when an operation abnormality (OFF abnormality) in which the contact point of the heater relay is kept closed, energization to the heater is continued despite the OFF instruction from the heater energization control means.
Even if the power supply to the heater is continued, the temperature of the hot water is set to a predetermined temperature by the end time of the midnight power.
If the temperature does not rise to the upper limit temperature of TSW1 and TSW2, energization of the heater will be started at the same time as energization of midnight power on the next day. Then, when the temperature of the hot water in the hot water storage tank rises to a predetermined upper limit temperature of the overheating thermoswitch, the overheating thermoswitch operates to open its normally closed contact, and the power supply to the heater is stopped. After the normally closed contact of the thermostat switch is opened, the heater cannot be energized thereafter unless the thermostat switch is manually reset. Further, when an operation abnormality (on abnormality) occurs in which the contact point of the heater relay remains open, the heater is not energized in spite of an ON command from the heater energization control means, and the hot water is heated. You can't do that. Regardless of the operation abnormality, the user of the water heater or the person who repairs it does not immediately know where the cause of the hot water does not boil, and until he notices that there is an abnormality in the heater relay. There was a problem that took a long time.

An object of the present invention is to provide a control device for a hot water storage type electric water heater which can automatically detect the occurrence of an abnormality in a heater relay.

Another object of the present invention is to provide a control device for a hot water storage type electric water heater which can automatically detect the occurrence of an abnormality in a heater relay and display the occurrence of the abnormality.

Still another object of the present invention is to automatically detect the occurrence of an abnormality in the heater relay and display the occurrence of the abnormality, and to operate the water heater until repair is performed. An object of the present invention is to provide a control device for an electric water heater.

[0008]

SUMMARY OF THE INVENTION The present invention provides a heater relay having an open / close contact disposed in a current path between a heater and a power supply, and an on / off command for controlling the opening / closing of the open / close contact of the heater relay. Control of a hot water storage type electric water heater comprising a heater energization control means to be generated, and an over-elevation thermoswitch in which a normally closed contact is arranged in an energizing path and opens the normally closed contact when the temperature of hot water in the hot water storage tank reaches an upper limit temperature. Equipment is targeted for improvement.

According to the first aspect of the present invention, the power supply detecting means for detecting whether or not power is supplied to the heater, and the power supply detecting means for outputting power to the heater after the heater energizing control means outputs an OFF command. A relay abnormality determining means for outputting an OFF abnormality detection signal indicating that an OFF abnormality has occurred in the heater relay when the supply is detected, and an abnormality display driven by the OFF abnormality detection signal to display the abnormality of the heater relay Means are provided. The relay abnormality determination means has practical value even if it is possible to determine the OFF abnormality. This is because most of the relay operation abnormality belongs to the OFF abnormality.

The power supply detecting means may have any configuration as long as it can detect that power is being supplied to the heater. For example, a voltage detection circuit may be provided in parallel with the heater, and the presence or absence of power supply may be detected based on the presence or absence of a voltage applied to the heater. May be detected. Further, the heater energization control means turns on and off the heater relay in accordance with a predetermined control mode such as a shift control mode that shifts the energization start time to the heater so that the hot water is heated at the end time of the specific power time zone such as midnight power. Any command may be output as long as it outputs a command. In the specification of the present application, the OFF abnormality refers to an operation abnormality in which the open / close contact of the heater relay cannot be opened while being closed, and the ON abnormality refers to an operation abnormality in which the open / close contact of the heater relay cannot be closed while being opened.

According to the second aspect of the present invention, when the power supply detecting means does not detect the supply of power to the heater after the heater energization control means outputs the ON command to the relay abnormality determining means, an ON abnormality occurs in the heater relay. A function to output an ON abnormality detection signal indicating that the

According to the third aspect of the present invention, the abnormality display means is provided on an input panel for inputting control conditions such as the heating temperature to the heater power supply control means.

According to the fourth aspect of the present invention, the normally-closed contact arranged on the current-carrying path is driven by the OFF-abnormality detection signal, and is reset when the supply of power from the power supply to the current-carrying path is stopped. A relay is further provided.

According to a fifth aspect of the present invention, there is further provided an ON abnormality auxiliary relay which is driven by the ON abnormality detection signal, closes the normally open contact connected in parallel with the switching contact of the heater relay, and is reset by the OFF command.

As in the sixth aspect of the present invention, the present invention can naturally be applied to a case where a plurality of heaters are arranged in a hot water storage tank. In that case, a power supply detection unit and a relay abnormality determination unit are provided for a plurality of heater relays provided for each of the heaters. In this case, the power supply detection unit and the relay abnormality determination unit may be provided for each heater, but a common power supply detection unit and a relay abnormality determination unit may be provided for a plurality of heaters.

[0016]

When the heater relay is turned off, the switching contact of the relay does not open even if an off command is output from the heater energization control means. Therefore, the power supply detection means detects the supply of power to the heater. Become. Therefore, according to the first aspect of the present invention, when the power supply detection means detects the supply of power to the heater even after the heater energization control means outputs the OFF command, the relay abnormality determination means generates an OFF abnormality. Is determined. The OFF abnormality detection signal output from the relay abnormality determination unit drives the abnormality display unit to indicate the occurrence of the abnormality, and thus can promptly deal with the repair of the water heater.

According to the second aspect of the present invention, the relay abnormality judging means also detects the ON abnormality of the heater relay. As a result, all abnormalities assumed in the relay can be detected.

If an abnormality display means is provided on the input panel for inputting control conditions such as the heating temperature to the heater energization control means, it is possible to easily confirm the occurrence of an abnormality.

According to the fourth aspect of the present invention, if an OFF abnormality auxiliary relay which is driven by an OFF abnormality detection signal and opens a normally closed contact disposed in the current path is provided, an over-abnormality relay is detected after the occurrence of the OFF abnormality is detected. The power supply to the heater can be stopped without operating the elevation thermoswitch. When the power supply from the power supply to the power supply path is stopped, the auxiliary relay at the time of the abnormal OFF is reset and closes the contact. Therefore, at the next specific power supply start time, energization of the heater is started, and the OFF abnormality auxiliary relay is driven by the output of the OFF abnormality detection signal from the relay abnormality determination means to open a contact and stop energization. In this case, the shift control cannot be performed, but the operation state of the water heater can be maintained until the replacement of the heater relay is completed.

According to a fifth aspect of the present invention, when a relay for turning on an abnormal condition is provided which is driven by an on abnormality detecting signal and closes a normally open contact connected in parallel with the open / close contact of the heater relay, the heater relay has an abnormal abnormality. Is generated, the heater can be energized. The auxiliary relay for abnormal ON state is reset by the OFF command, so that the power supply to the heater can be stopped without activating the thermostat switch. Thereafter, the energization is controlled using the next ON abnormality detection signal as an ON command. Therefore, in this case, the shift control is performed, and the operation state of the water heater can be maintained until the replacement and repair of the heater relay is completed.

According to a sixth aspect of the present invention, when the power supply detecting means and the relay abnormality determining means are provided for the heater relay used for controlling the energization of the plurality of heaters disposed in the hot water storage tank, Product reliability can be greatly increased.

[0022]

Embodiments of the present invention will be described below in detail with reference to the drawings. FIG. 1 shows an embodiment of a control device for a hot water storage type electric water heater according to the present invention. This embodiment is a schematic configuration diagram of an embodiment in which the present invention is applied to an electric water heater of a type in which one heater H is disposed in a hot water storage tank (not shown).
In FIG. 1, only the contacts of the relays RH, SR1, SR2 and the over-elevated thermoswitch TSW are shown, and a drive circuit or a drive mechanism is not shown.
In the figure, reference numeral 1 denotes a power supply for supplying midnight power,
Is a heater energization control unit that receives signals from the temperature setting unit 3 and the water temperature detection unit 4 and outputs an ON command and an OFF command to a heater relay HR for controlling energization to the heater H. Although the set temperature setting means 3 is for setting the boiling temperature, a setting means for setting the amount of hot water can be provided instead of the temperature setting means.
Water temperature detecting means 4 includes a temperature sensor for measuring the temperature of the water supplied to the hot water storage tank and the temperature of the hot water, and a temperature sensor for detecting the amount of remaining hot water in the hot water storage tank. The configuration of the heater power supply control means is arbitrary, but here, for example, the required power supply time is calculated based on the set temperature, the water temperature, and the remaining hot water amount, and the heater power is supplied to the heater so that the hot water is boiled by the end of the midnight power supply. The shift control for controlling the energization is performed. The off command is output when the hot water temperature detected by the temperature sensor reaches a preset temperature. Note that an off command can be output using a timer regardless of the hot water temperature.

In an energizing path for supplying electric power from the power source 1 to the heater H, an open / close contact of a heater relay HR controlled to be opened / closed by an output of the heater energization control means 2 and a normally closed contact of an OFF abnormality auxiliary relay SR1 are provided. , Thermostat switch TSW
And a power supply detecting means 5 are provided. The normally open contact of the auxiliary relay SR2 for ON abnormality is connected in parallel to the open / close contact of the heater relay HR. Since the heater relay HR frequently opens and closes the on-off contact, a relatively expensive relay having a low failure rate and a long contact life is used as the heater relay HR. On the other hand, since the auxiliary relays SR1 and SR2 are hardly opened and closed, a relatively inexpensive relay having a short contact life can be used. Of course, as these auxiliary relays SR1 and SR2, expensive relays may be used similarly to the heater relay HR.

The power supply detecting means 5 detects whether or not power is being supplied from the power supply 1 to the heater.
The detection result is input to the relay abnormality determination means 6. As the power supply detecting means 5, for example, as shown in FIG. 2, a heater voltage detecting circuit 5 'connected in parallel to the heater H can be used. FIG. 3 shows an example of a circuit configuration of the heater voltage detection circuit 5 '. In this circuit, a varistor B for protecting the circuit from abnormally high voltage and a series circuit including a resistor R2 and a diode D2 are connected in parallel to both ends of the heater H, respectively. The photodiode D1 is connected in anti-parallel to the diode D2. Therefore, when AC is supplied to the heater H from the power supply through the heater relay HR, the photodiode D is generated by one half-wave of AC.
1 flashes. This blinking is received by the phototransistor TR, the transistor TR is turned on and off, and the transistor T
When R is turned on, the potential at the connection point between the resistor R1 and the capacitor C grounded by the transistor TR, that is, 0 V is input to the input terminal of the relay abnormality determination means 6.
When the transistor TR is turned off, the capacitor C is charged from the control power supply (not shown) to the voltage of the control power supply through the resistor R1, and the voltage of the control power supply, for example, 5V, is input to the input terminal of the relay abnormality determination means 6. The relay abnormality determining means 6 determines that a voltage is applied to the heater H when the voltage of the input terminal is 0 V, that is, that power is supplied to the heater H, and that a voltage of 5 V is input to the input terminal. No voltage is applied to the heater H, that is, the heater H
Is determined to have no power supply. When such a heater voltage detection circuit 5 'is used, the relay abnormality determination means 6 has a determination period having a cycle longer than the cycle of the AC voltage applied to the heater H, and the input terminal is connected to the input terminal during this determination period. If a voltage of 5 V is input even once, it is configured to determine that power has been supplied.

In this example, the power supply detecting means 5 is constituted by the heater voltage detecting circuit 5 '. However, a current detecting means such as a current transformer is arranged on an energizing path to the heater H to supply the current to the heater H. The presence or absence of power supply may be determined by detecting.

The relay abnormality judging means 6 receives the output of the heater energization control means and the output of the power supply detecting means 5 and determines whether or not an operation abnormality has occurred in the heater relay. Specifically, the relay abnormality determining means 6 determines whether the heater relay is off or on. From the viewpoint of practicality, it is sufficient that at least the off abnormality can be determined. The heater abnormality determination unit 6 determines that an OFF abnormality has occurred when a signal for detecting the supply of electric power is input from the power supply detection unit 5 after the heater ON / OFF control unit 2 outputs an OFF command. When a signal for detecting that power is not supplied to the heater H is input from the power supply detection unit 5 after the ON command is output from the control unit 2, it is determined that an ON abnormality has occurred. I have.

The relay abnormality judging means 6 outputs a drive signal to the abnormality display means 7 and outputs a drive signal to the OFF abnormality auxiliary relay SR1 or the ON abnormality auxiliary relay SR2 when judging the operation abnormality. And power supply 1
Is reset when the supply of the late-night power from is terminated. Specifically, when the relay abnormality determination means 6 determines that an OFF abnormality has occurred, the relay abnormality determination means 6 outputs an OFF abnormality detection signal, and the OFF abnormality auxiliary relay SR1 is driven by this signal to open the normally closed contact. Therefore, an OFF abnormality occurs and the heater relay HR
Is not turned off, the normally-closed contact of the auxiliary relay SR1 for turning off is opened, the supply of power to the heater H is stopped, and the hot water heating operation is stopped. The OFF abnormality auxiliary relay SR1 is configured to be reset when the midnight power supply is stopped, so that the normally closed contact is closed. Therefore, at the same time that the start time of the midnight power of the next day arrives, power supply to the heater H is started regardless of the ON command from the heater power supply control means 2. When the OFF abnormality detection signal is output from the relay abnormality determination means 6, the normally closed contact of the OFF abnormality auxiliary relay SR1 is opened, and the supply of power to the heater H is stopped. Thereafter, this operation is repeated. According to this embodiment, since the abnormality display means 7 can continue the operation of the water heater until the repair requested by the user based on the abnormality occurrence display is completed, no inconvenience occurs even if the repair cannot be performed immediately. .

When it is determined that an ON abnormality has occurred, the relay abnormality determining means 6 outputs a drive signal for closing the normally open contact to the auxiliary relay SR2 for ON abnormality. Therefore, when an ON abnormality occurs and the heater relay HR does not turn ON, the ON abnormality auxiliary relay SR2 closes and power is supplied to the heater H. ON abnormality auxiliary relay SR
The relay 2 is reset by an off command output from the heater energization control means 2 to open a contact. The contact of SR2 is opened, and the power supply to the heater H is stopped. Thereafter, the operation of the water heater is continued until the repair is completed, with the ON abnormality detection signal output by the relay abnormality determining means 6 as an ON command.

It is to be noted that the operation of the water heater can be maintained by using the auxiliary relay SR1 at the time of abnormal ON and the auxiliary relay SR2 at the time of abnormal OFF. This is because a command is output.

The abnormality display means 7 displays an abnormality of the heater relay by using at least one of various display means such as sound and image. For example, if this abnormality display means 7 is used for an input panel on which the temperature setting means 3 is arranged, the user of the water heater can easily know the occurrence of the abnormality.

FIG. 4 is a flowchart showing an algorithm of software used when the relay abnormality judging means 6 of the above embodiment is realized using a microcomputer. In step ST41, data indicating whether or not a voltage is applied to the heater from the heater voltage detection circuit shown in FIGS. 2 and 3 is input. And step ST
At 42, it is determined whether or not a voltage is applied. If no voltage is applied to the heater, the process proceeds to step 43. In step 43, it is determined whether or not an ON command has been output from the heater power supply control means 2. If an ON command has not been output, normal processing is executed in step ST44. Normally, there is no need to do anything during normal operation.However, for example, when displaying the presence or absence of an abnormality in the heater relay by displaying an image, it is necessary to supply data indicating that the operation is normal to the image display means. Become. If the ON command has been issued, the process proceeds to step ST45, and the process at the time of abnormality is performed. The process at the time of abnormality is a process of supplying an ON abnormality detection signal to the abnormality display means 7 and the auxiliary relay SR2 at the time of abnormality. When it is determined in step ST42 that a voltage is applied to the heater H,
The process proceeds to step ST46, and in step ST46, it is determined whether or not an off command is output from the heater power supply control means 2. If it is determined in step ST46 that there is no output of the off command, the process proceeds to step ST47, and if it is determined that there is an output of the off command, the process proceeds to step ST48. In step ST48, an OFF abnormality detection signal is output to the abnormality display means 7 and the OFF abnormality auxiliary relay SR1.
Note that not only the relay abnormality determination means 6 but also the control means for the heater energization control means 2 and the abnormality display means 7 can be realized using a microcomputer. Since this point is already known, the description is omitted.

In the above-mentioned embodiment, the auxiliary relay S
R2 and an auxiliary relay SR1 for OFF state are provided, so that the water heater can be operated even after the heater relay HR becomes abnormal. However, only the abnormality display means 7 is provided.
After determining the abnormality of the heater relay, only the occurrence of the abnormality may be displayed. In addition, since the operation abnormality of the heater relay is almost the OFF abnormality, in practice, it is sufficient that at least the OFF abnormality can be detected. In this case, the auxiliary relay SR2 for ON abnormality may be removed from the embodiment. However, even in this case, it is preferable that the relay abnormality determination unit 6 detects an ON abnormality and the abnormality display unit 7 displays the occurrence of the ON abnormality by the ON abnormality detection signal.

FIG. 5 shows a circuit configuration of a main part of an embodiment in which the present invention is applied to a control device of a so-called two-heater type hot water storage type electric water heater in which heaters are respectively arranged at a lower portion and an upper portion in a hot water storage tank. Is shown. The difference from the conventional apparatus shown in FIG. 7B is that the switching type heater relay HR1 for connecting the power supply path to the lower heater H1 and the power supply path to the upper heater H2 to the power supply AC is not used. In addition, heater relays HR2 and HR
3 and the provision of auxiliary relays SR11 and SR12 at the time of OFF abnormality, and a heater voltage detection circuit 5 'as power supply detection means for detecting whether or not power is supplied to each of the heaters H1 and H2 is provided in each energizing path. It is a point. Here, the heater relays HR2 and HR3 are opened / closed for energizing the lower heater H1 and the upper heater H2 and switching between the upper heater and the lower heater. The OFF relays SR11 and SR12 at the time of OFF abnormality have normally closed contacts,
When an OFF abnormality detection signal is output from a relay abnormality determination unit (not shown) that determines an operation abnormality of each heater relay with the output of the heater voltage detection circuit 5 'as an input, the operation is performed to open the normally closed contact. A relay abnormality determination unit (not shown) may be provided for each heater voltage detection circuit, or one relay abnormality determination unit may determine abnormality of two heater relays.

In the two-heater type control device, it is preferable to avoid a situation in which the two heaters are energized simultaneously. Further, the two-heater type control device has a feature that even if it is impossible to supply power to one of the heaters, the minimum required hot water can be secured by supplying power to the other heater. Therefore, when an OFF abnormality occurs in one of the heater relays, the energization to the subsequent heaters is stopped entirely or the energization to a heater that is energized through the heater relay in which the OFF abnormality occurs is prevented. To In order to completely block the energization of each heater, for example, the output of the OFF abnormality detection signal is stored in a memory backed up by a backup power supply, or stored in a non-volatile memory that does not require a backup power supply. The auxiliary relays SR11 and SR11 for OFF abnormality are stored each time the power supply is performed at midnight.
Control may be performed so as to open the twelve contacts. This control can be performed by the relay abnormality determination means. Even in the case where the energization of a heater that is energized through the heater relay in which an abnormality has occurred is blocked, the generation of the OFF abnormality detection signal is similarly stored in the memory, and the supply of the power for the next and subsequent nights is performed based on the storage. The control may be performed such that the contact point of the auxiliary relay SR at the time of the abnormal OFF in the energized path where the abnormal OFF occurs is opened each time the abnormal state occurs.

If an ON abnormality has occurred in one of the current paths, it is only necessary to perform temporary boiling using the other heater, so that it is possible to energize the heater in the current path in which the ON abnormality has occurred. No need to do. For this reason, in this embodiment, no auxiliary relay for ON abnormality is provided for the heater relay. It is needless to say that an ON abnormality auxiliary relay may be provided in the same manner as in the embodiment of FIG.

FIG. 6 is a flowchart showing an algorithm of software used when the relay abnormality judging means is realized using a microcomputer in the embodiment of FIG. Steps ST61 to ST68 in FIG. 6 are directed to the upper heater H2.
9 to ST76 are for the lower heater H1. These steps correspond to step ST in FIG.
41 to ST48, the description is omitted.

[0037]

According to the first aspect of the present invention, the relay abnormality judging means judges the occurrence of the OFF abnormality and drives the abnormality display means based on the OFF abnormality detection signal to display the occurrence of the abnormality. There is an advantage that can deal with the repair of the vessel.

According to the second aspect of the present invention, since the relay abnormality determination means also detects the ON abnormality of the heater relay, all possible abnormalities can be detected.

According to the third aspect of the present invention, since the abnormality display means is provided on the input panel for inputting control conditions such as the heating temperature to the heater energization control means, the occurrence of an abnormality can be easily confirmed.

According to the fourth aspect of the present invention, when an auxiliary relay for turning off is provided which opens the normally closed contact disposed on the conduction path by being driven by the turning-off detection signal, an excessive rise occurs after the occurrence of the turning-off abnormality is detected. Without activating the thermo switch,
Power supply to the heater can be stopped. Although shift control cannot be performed, there is an advantage that the operating state of the water heater can be maintained until replacement and repair of the heater relay is completed.

According to the fifth aspect of the present invention, even if an abnormality occurs in the heater relay, the heater can be energized, and the hot water can be supplied until the shift control is performed and the replacement of the heater relay is completed. There is an advantage that the operation state of the vessel can be maintained.

When the power supply detecting means and the relay abnormality determining means are provided for the heater relay used for energizing the plurality of heaters, the reliability of the product of the water heater is greatly improved. be able to.

[Brief description of the drawings]

FIG. 1 is a diagram showing a schematic structure of an embodiment of a control device for a hot-water storage type electric water heater according to the present invention.

FIG. 2 is a circuit diagram for explaining an example of a power supply detection unit used in the embodiment of FIG.

FIG. 3 is a circuit diagram showing an example of a heater voltage detection circuit used as power supply detection means.

FIG. 4 is a flowchart showing an example of a software algorithm when the relay abnormality determination means used in the embodiment of FIG. 1 is realized using a microcomputer.

FIG. 5 is a circuit diagram showing a main part of an embodiment in which the present invention is applied to a control device of a two-heater type hot water storage type electric water heater.

FIG. 6 is a flowchart showing an example of a software algorithm when the relay abnormality determination means used in the embodiment of FIG. 5 is realized using a microcomputer.

FIGS. 7A and 7B are circuit diagrams used to explain the problems of the conventional control device for a hot water storage type water heater.

[Explanation of symbols]

 1 Power supply 2 Heater energization control means 3 Temperature setting means 4 Water temperature detection means 5 Power supply detection means 6 Relay abnormality judgment means 7 Abnormality display means H Heater HR Heater relay TSW Excessive rise thermo switch SR1 Off abnormality auxiliary relay SR2 On abnormality Auxiliary relay

Claims (6)

(57) [Claims] 1. A heater relay having an open / close contact disposed in an energization path between a heater and a power supply, and a heater energization control means for generating an ON command and an OFF command for controlling opening / closing of the open / close contact of the heater relay. A control device for a hot-water storage type electric water heater comprising: a normally-closed contact disposed in the current path, and an over-elevation thermoswitch that opens the normally-closed contact when the temperature of hot water in the hot-water storage tank reaches an upper limit temperature. Power supply detection means for detecting whether or not power is supplied to the heater; and the power supply detection means detects supply of power to the heater after the heater energization control means outputs the off command. Relay abnormality determination means for outputting an OFF abnormality detection signal indicating that an OFF abnormality has occurred in the heater relay; and the heater driven by the OFF abnormality detection signal. A control device for a hot-water storage type electric water heater, comprising: abnormality display means for displaying an abnormality of a relay. 2. The relay abnormality judging means according to claim 1, wherein said heater supply relay detects an ON abnormality in said heater relay when said power supply detecting means does not detect supply of electric power to said heater after said heater energization control means outputs said ON command. The hot water storage type electric water heater according to claim 1, further comprising a function of outputting an ON abnormality detection signal indicating that the operation is being performed, wherein the abnormality display means is also driven by the ON abnormality detection signal. Control device. 3. The control device for a hot-water storage type electric water heater according to claim 2, wherein said abnormality display means is provided on an input panel for inputting control conditions such as a boiling temperature to said heater power supply control means. 4. An OFF abnormality assisting device which is driven by the OFF abnormality detection signal to open a normally closed contact arranged in the current path and is reset when power supply from the power supply to the current path is stopped. 4. The hot water storage type electric water heater control device according to claim 1, further comprising a relay. 5. An on-abnormal auxiliary relay which is driven by the on-abnormality detection signal, closes a normally-open contact connected in parallel with the on-off contact of the heater relay, and is reset by the off command. The control device for a hot-water storage type electric water heater according to 2, 3, or 4. 6. A plurality of heaters are arranged in the hot water storage tank, and the power supply detecting means and the relay abnormality determining means are provided for a plurality of heater relays provided in each of the heaters. The control device for a hot-water storage type electric water heater according to claim 1, 2 or 3.