JPS6316656B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a control device for a hot water storage type electric water heater that uses late-night electricity, and calculates the required energization time to the heating element from the amount of heat held by the remaining hot water in the hot water storage tank. The purpose is to reduce heat loss after boiling by controlling the start time of energization to the heating element so that the boiling occurs at the same time as the end of the energization time of late-night electricity.

Figure 1 shows the main power supply circuit of a conventional hot water storage type electric water heater that uses late-night electricity. In the figure, 1 is a power source, and 2 is a time switch for late-night power, and the power-on period is generally from 11:00 PM to 7:00 AM the next morning.

3 is a heating element, and its heating element capacity is set in advance so that it has the ability to boil water at around 8°C, which corresponds to winter water temperature, to 85°C within the late-night electricity supply time frame. 4 is an automatic temperature regulator, which has a normally closed contact and opens when the water temperature in the hot water storage tank reaches 85°C.

Next, the function and operation will be explained. When the time to start supplying late-night power comes, the contact of the time switch 2 is closed and the supply of electricity to the heating element 3 is started. When the temperature of the hot water in the hot water storage tank reaches 85° C., the contacts of the automatic temperature controller 4 are opened and the electricity to the heating element 3 is stopped.

In this way, all the stored hot water is boiled to 85℃ every morning.

However, the amount of hot water used is not always the same.
It varies from day to day and largely from season to season. In particular, whether or not a person takes a bath is a factor that greatly influences the amount of hot water used, and on days when a person does not take a bath, more than half of the stored hot water may remain.

Therefore, even though the hot water will reach boiling point in a short time if there is residual hot water, power supply to the heating elements 3 is started all at once at the time when the late-night power supply is applied. As a result, the power load is concentrated immediately after the power supply starts, making it impossible to equalize the power load, which is the original purpose of late-night power, and resulting in poor power transmission efficiency. This method has the disadvantage that hot water is left unused for a long time and heat loss due to natural heat radiation increases.

In addition, some conventional electric water heaters have a method of detecting the amount of remaining hot water and delaying the start time of energizing the heating element. It was a step-by-step measurement that involved lining up multiple temperature sensors such as thermometers and thermistors to detect temperature changes at specific locations.

For this reason, it was not possible to measure the amount of remaining hot water with high accuracy, and it was only used as reference data for the next boiling.

The present invention aims to solve these drawbacks by accurately detecting the amount of heat remaining in the hot water storage tank, calculating the required energization time to the heating element, and calculating the required energization time at the end of the late-night power supply. The purpose is to control the start time of energizing the heating element so that it can be extinguished.

Hereinafter, one embodiment of the present invention will be described with reference to the drawings. FIG. 2 is a structural sectional view of the hot water storage type electric water heater, FIG. 3 is a control block diagram, and FIGS. 4 and 5 are temperature distribution diagrams inside the hot water storage tank.

In FIG. 2, 11 is a hot water storage tank, and 12 is a hot water storage tank 1 for measuring the temperature of hot water in the hot water storage tank 11.
1 is a temperature detector provided at the lower part of 1, 13 is a water supply pipe, 14 is a hot water supply pipe, and 15 is a faucet provided at the tip of this hot water supply pipe. Reference numeral 16 denotes a circulation pump as a stirring device, which is installed in the middle of a communication pipe 17 whose one end is connected to the lower part of the hot water storage tank 11 and the other end is connected to the middle of the hot water supply pipe 14. Water is routed to the connection part with the hot water pipe 14.
In FIG. 3, 20 is a residual water heat quantity detection means; 21
is a calculation means A, 22 which calculates the amount of heat to be heated from the amount of heat of the remaining water detected by the amount of heat of the remaining water detected by the amount of heat of the remaining water detection means 20;
is a calculation means B that calculates the required energization time for the heating element 3 from the amount of heat to be heated determined by the calculation means A21;
This is a timer device for controlling the start time of energization to the heating element 3 so that the required energization time determined in step 2 can be obtained.

Next, a method of detecting the amount of heat of the remaining water by the remaining water heat amount detection means 20 will be explained with reference to FIGS. 4 and 5.

As shown in FIG. 2, it is assumed that the hot water storage tank 11 is initially filled with hot water at T ₁ [°C].

FIG. 4 shows the temperature distribution inside the hot water storage tank 11 after hot water of V ₁ [] is taken out from the faucet 15 and used in this state. That is, water at t [°C] flows into the lower part 11a of the hot water storage tank from the water supply pipe 13 in an amount equal to the amount of hot water used V ₁ [], and hot water at T ₁ [°C] flows into the upper part 11b of the hot water storage tank at V ₂ []
It remains. In this state, when the circulation pump 16 is operated with the faucet 15 closed, water in the lower part 11a of the hot water storage tank flows from the upper part 11b of the hot water storage tank through the communication pipe 17, and
Because the water tank is stirred, the temperature of the water gradually averages out.

FIG. 5 shows the temperature distribution of the hot water temperature in the hot water storage tank 11 averaged in this way, and the average temperature is T ₂ [°C].

Next, we will explain how to calculate the heat value of the remaining hot water. The tank capacity of the hot water storage tank 11 is V[] (eigenvalue V=V ₁ +V ₂ )
Then, the temperature measured by the temperature detector 12 installed at the lower part 11a of the hot water storage tank before the operation of the circulation pump 16 is t [°C], and the temperature measured after the operation of the circulation pump 16 is
Since T ₂ [℃], the residual water heat amount C [Kcal] can be calculated as follows.

C=V×(T ₂ −t) [Kcal] Next, the calculating means A21 calculates the amount of heat to be heated by the heating element 3. Now, if the required boiling temperature is T [°C], the heating The amount of heat to be consumed Cin [Kcal]
can be determined by Cin=V(T-t)-C [Kcal]. Further, the calculation means B22 calculates the required energization time H from the value of the amount of heat Cin to be heated, and calculates the rated power consumption W of the heating element 3.
Assuming [kw/hr], the required energization time H can be found as follows: H=Cin/W×860 [hr]. Then, the timer device 23 counts the time and starts energizing the heating element 3 when the remaining time until the end of the energization of the late-night power matches the required energization time determined by the calculation means B22.

As described above, the present invention calculates the amount of heat to be heated by detecting the amount of heat remaining in the hot water, calculates the required energization time to the heating element from this amount of heat, and further calculates the amount of time required for energizing the heating element by using the late-night power supply. By controlling the start time of energization to match the end of the energization time period, the time the heated hot water is left unused is shortened, and heat loss due to natural heat radiation from the hot water storage tank is reduced, reducing maintenance costs. In addition to being cheaper, power is applied during the latter half of the late-night power supply period depending on the amount of remaining hot water, which alleviates the peak power load during the first half of the power supply period, improving power transmission efficiency.

In addition, the remaining hot water heat amount is calculated by stirring the hot water storage tank to average the hot water temperature, detecting the temperature at that time and the temperature before averaging, and calculating the remaining hot water heat amount from these detected temperatures and the tank capacity. Since the calculation is performed, the heat value of the remaining hot water can be detected with high precision as a continuous value, and the required time for energizing the heating element can also be accurately calculated.

[Brief explanation of the drawing]

Fig. 1 is a main power supply circuit diagram of a conventional hot water storage type water heater, Fig. 2 is a structural sectional view of a hot water storage type electric water heater showing an embodiment of the present invention, Fig. 3 is a control block diagram thereof, and Fig. 4 FIG. 5 is a temperature distribution diagram inside the hot water storage tank. 3 is a heating element, 11 is a hot water storage tank,
12 is a temperature detector, 16 is a circulation pump (stirring device), 20 is residual water heat detection means, 21 is calculation means A, 22 is calculation means B, and 23 is a timer device.

Claims (1)

[Claims] 1 It has a stirring device that stirs the inside of the hot water storage tank to average the temperature of the hot water, and a temperature detector that detects the temperature of the lower part of the hot water storage tank, and detects the temperature of the lower part of the hot water storage tank before and after the operation of the stirring device. Then, there is a residual water heat amount detection means that calculates the residual water heat amount from these detected temperatures and tank capacity, and a residual water heat amount detection means that calculates the amount of heat to be heated from the residual water heat amount detected by this residual water heat amount detection means, and from this amount of heat to be heated. A calculation means for calculating the required energization time to the heating element, and a timer device for controlling the start time of energization to the heating element so that the required energization time calculated by the calculation means is obtained at the end time of the late-night power supply. A control device for a hot water storage type electric water heater.