JPH0322552B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a control device for an electric water heater that uses late-night electricity.

[Conventional technology]

A conventional electric water heater of this type had a configuration as shown in FIG.

In the figure, 1 is a hot water storage tank, and a heating element 2 is attached to the lower part of the tank.

3 is a thermostat for controlling the boiling temperature, and is attached to the lower outer wall surface of the hot water storage tank 1.

Reference numeral 4 denotes a faucet for taking out hot water that has boiled up in the hot water storage tank 1. When the faucet 4 is opened, hot water in the hot water storage tank 1 is supplied under pressure from a water source connected to a water supply pipe 5.

Figure 5 shows the electrical circuit diagram of the conventional example.
7 is a power supply, and 7 is a time switch for setting the midnight power supply time.

Next, to explain the operation of the above configuration, the heating element capacity is set so that the heating element 2 boils water from approximately 8°C to the target temperature of 85°C within 8 hours during the late-night power supply period. ing.

In addition, the thermostat 3 having a normally closed contact point is
When the water in the hot water storage tank 1 reaches 85°C, a contact is opened to stop energizing the heating element 2, and the hot water storage tank 1 is filled with hot water at 85°C every morning.

[Problem that the invention seeks to solve]

However, the amount of hot water used is not always the same.
It changes greatly from day to day, depending on the season, and also due to changes in family structure.

The above-mentioned conventional electric water heaters, which always boil water at a constant temperature such as 85 degrees Celsius, require setting the boiling temperature every day to keep up with these changes in the amount of heat required, which is cumbersome to operate. It is becoming more and more common for people not to operate the device after doing so.

Therefore, it has become common to use the remaining hot water, which means that the boiled high-temperature water is left unused for a long time, increasing the loss of natural heat radiation from the hot water storage tank. There was a problem.

This invention attempts to solve these conventional problems.It boils only the appropriate amount of hot water according to past boiling results, the water supply temperature, and the state of the remaining hot water, and also turns on electricity to the heating element at the appropriate time. The object of the present invention is to obtain a control device for an electric water heater that reduces natural heat radiation loss.

[Means for solving problems]

The electric water heater control device according to the present invention includes temperature sensors that detect the water supply temperature, the upper temperature of the hot water storage tank, and the boiling temperature, a flow rate sensor that detects the amount of hot water used, and a boiling target based on past boiling results. A boiling target setting means that sets the applied electric energy and the boiling target temperature, calculates the electric energy for the remaining hot water from the detected value of each sensor, calculates the net energization time to the heating element based on the value, Calculating means calculates the start time of energization to the heating element so that boiling ends in the latter half of the late-night power supply period from the net energization time, and a calculation means that starts energization of the heating element at the calculated energization start time. , a control means for controlling the electricity supply to the heating element to be stopped when the boiling target temperature is reached, and a storage means for storing the electricity supply time for the heating element and the water temperature at the time when the electricity supply to the heating element is stopped. It is something that

[Effect]

In this invention, control is performed to boil only the appropriate amount of hot water based on the amount of hot water expected to be used the next day based on past results of hot water usage, the temperature of the supplied water, and the amount of hot water remaining in the hot water storage tank. The net energization time is calculated and the energization is controlled to start at a predetermined time.

〔Example〕

FIG. 1 is an overall configuration diagram of an embodiment of a control device for an electric water heater according to the present invention.

As is clear from FIG. 1, in this embodiment, a water temperature sensor 8 and a flow rate sensor 9 are installed in the middle of the water supply pipe 5, and a boiling water temperature sensor 10 and an upper temperature sensor 11 are installed at the bottom and top of the hot water storage tank 1. Based on the detection signals of the flow rate sensor 9, water temperature sensor 8, and upper temperature sensor 11, the calculation means 16 first calculates the amount of electricity equivalent to the heat amount of the remaining water, and then the boiling target setting means 13
sets the amount of applied power and boiling temperature that are expected to be required the next day based on past results of the amount of hot water used, and then only the appropriate amount of hot water is boiled based on the amount of power for the remaining hot water and the results of the boiling target setting means 13. Calculate the net energization time for the heating element 2, calculate the time from when the time switch 7 is turned on to energize the heating element 2 based on the result, and calculate the net energization time for the heating element 2 based on the result.
is controlled by the control means 17, and after the completion of boiling, the water temperature detected by the water temperature sensor 10, the net energization time to the heating element 2, and the amount of remaining water detected by the flow rate sensor 9 are controlled by the control means 17. is configured to be stored in the storage means 18.

FIG. 2 is a circuit diagram showing the electrical connections of the embodiment of FIG. 1.

In the figure, 19 is a microcomputer in the control circuit, including a CPU 20, a memory 21, and an input circuit 2.
2. It has an output circuit 23. The heating element control circuit 24 includes a resistor 25, a transistor 26, and a relay 2.
7 and 28.

The energizing coil 27a of the relay 27 is connected between the positive terminal +V and the GND terminal via a transistor 26, and the base of the transistor 26 is connected to the output circuit 23 via a resistor 25.

The contact 27b of the relay 27 is connected to the relay 28.
The energizing coil 28a and the power source 29 are connected in series. The contact 28b of the relay 28 is
The heating element 2 and the power source 6 are connected in series.

29, 30, 31 are each temperature sensor 8, 10,
11 is a resistor connected in series; 32 is an analog multiplexer into which the detection outputs of the temperature sensors 8, 10, and 11 are input; 33 is an A/D converter that converts the outputs into digital; 34 is the flow rate sensor 9; It is a pulse counter into which a detection output is input, and its output and the output of the A/D converter 33 are applied to the input circuit 22.

Next, the operation of the above embodiment will be explained with reference to FIG.

Figure 3 shows the memory 2 of the microcomputer 19.
1 is a flowchart showing heating element control stored in FIG. First, when the power is turned on, initial setting of the target applied power P and target temperature T for boiling starts at step 35 shown in FIG.

Next, in step 36, the applied power amount correction coefficient α is set. As initial values, P=4.4×8, T=85°C, and α=1.0 are given, respectively. In step 37, the water temperature _Tw is read, in step 38 the remaining hot water temperature _Tz is read, and in step 39 the remaining hot water amount _Vz is read. Further, in step 40, the remaining hot water amount _Vz is stored in the memory 21.

Next, in step 41, the electric energy _Kz for the remaining hot water is determined.

K _z =V _z ×(T _z −T _w )/860×η Here, η indicates heating efficiency.

Next, in step 42, the target applied power amount P for boiling is
The net energization time H _a for energizing the heating element 2 is determined from the amount of electricity K _z corresponding to the remaining hot water.

_Ha = P-K _z /W W is the power consumption of the heating element 2. In step 43, the net energization time H _a required for boiling determined in step 42 is allocated to which time slot in the late-night power supply period, that is, in what hours after the time switch 7 is turned on, energization is started. This is what we are looking for.

H=8-H _a Step 44 is to check whether time switch 7 is turned on.
At step 45, the elapse of the energization start time H is checked. When time H has elapsed, energization to the heating element 2 is started at step 46, and it is determined at step 47 whether or not the water temperature has reached the target temperature T. If the determined results are equal, turn off the heating element 2 in step 49.
However, if the target temperature has not yet been reached, it is checked in step 48 whether time switch 7 has been turned off. If the result is ON, step 47 is executed, and if OFF, step 49 is executed. step
At step 50, the net energization time and the boiling water temperature up to the point of completion of boiling are stored in the memory 21.

Next, in step 51, the net energization times H _a1 , H _a2 . . . H _ao ,
Boiling water temperature T ₁ , T ₂ ...T _o , remaining water amount V _z1 , V _z2 ...
Read V _zo and calculate the net energization time H _a1 for the past n days,
In step 52, the average power consumption P _av is determined from H _a2 . . . H _ao .

In step 53, the residual hot water amounts V _z1 , V _{z2 . . .} It is determined in step 54 whether or not it is longer than m days, and if it is longer than m days, the applied power correction coefficient α is negatively modified (for example, α=α−0.1) in step 55.

Also, if the amount of remaining hot water is less than the standard remaining hot water V _B ,
It is determined in step 56 whether or not the number of days with low power consumption is m or more consecutive days, and if it is m or more, the applied power amount correction coefficient α is modified in a positive manner (for example, α=α+0.1) in step 57.

The correction coefficient α obtained here is used in step 58 to set the target applied power amount P for boiling. That is, P=P _av ×α Next, in step 59, the maximum value T _nax of the hot water temperatures T ₁ , T _{2 .} . . T _o read in step 51 is selected, and
In step 59, the target boiling temperature T for the next day is determined.

〔Effect of the invention〕

As described above, according to this invention, the next day's boiling temperature is predicted based on the past amount of hot water used, and the system is configured to boil only the appropriate amount of hot water based on the water temperature and the state of the remaining hot water in the hot water storage tank. The system can automatically predict the appropriate amount of hot water to match the rhythm of the day, reducing the amount of remaining hot water and lowering maintenance costs. Furthermore, since it is possible to predict the energization time, a peak shift effect can be expected.

[Brief explanation of drawings]

FIG. 1 is an overall configuration diagram showing one embodiment of a control device for an electric water heater according to the present invention, FIG. 2 is a circuit diagram showing its electrical connections, and FIG. 3 is a flowchart showing its operation. 4 and 5 show a conventional hot water storage type electric water heater, FIG. 4 is a schematic structural diagram thereof, and FIG. 5 is a main electric circuit diagram. In the figure, 8, 10, 11 are temperature sensors, 9 is a flow rate sensor, 13 is a boiling target setting means, 16
is a calculation means, 17 is a control means, 18 is a storage means,
19 is a microcomputer, and 24 is a heating element control circuit. Note that the same reference numerals in the figures indicate the same or corresponding parts.

Claims (1)

[Scope of Claims] 1. An electric water heater that uses late-night electricity includes a water temperature sensor that detects the temperature of water supplied to a hot water storage tank, an upper temperature sensor that detects the temperature of the upper part of the hot water storage tank, and a flow rate sensor that detects the amount of hot water used. , a water temperature sensor that detects the boiling temperature in the hot water storage tank, a boiling target setting means that sets the boiling target applied power amount and temperature from the past boiling time and boiling water temperature, and detection of each of the above sensors. Calculating the amount of electricity equivalent to the heat value of the remaining hot water from the value, and calculating the net energization time to the heating element based on the amount of electricity for the remaining hot water and the target applied amount of electricity set by the boiling target setting means, calculation means for calculating the start time of energization to the heating element so that heating ends in the latter half of the late-night power supply period from the net energization time; and energization to the heating element when the energization start time calculated by the calculation means is reached. a control means for controlling to stop energizing the heating element when the water temperature reaches the temperature set by the boiling target setting means; and a control means for controlling the energization time at the time when the energization to the heating element is stopped; A control device for an electric water heater, comprising a storage means for storing water temperature.