JPH0583823B2 - - Google Patents

Description

[Detailed Description of the Invention] [Field of Application of the Invention] The present invention relates to the control of an electric water heater, and involves controlling the heater by determining the boiling temperature that matches the amount of hot water used from the water supply temperature and the outside air temperature. This invention relates to a control device for an electric water heater that reduces residual hot water and reduces heat loss.

[Background of the invention]

As a means of reducing residual hot water and reducing heat loss, for example, as shown in Japanese Unexamined Patent Publication No. 130939/1983, the temperature of the supplied water is detected so that the amount of hot water supplied is constant throughout the year. Devices that control the boiling temperature are known.

This method has problems such as a large amount of remaining hot water in the summer when the amount of hot water supply is low, and a shortage of hot water in the winter, especially in cases where the amount of water is almost constant throughout the year, such as underground water. Ta.

[Purpose of the invention]

The present invention ameliorates such problems and, throughout the year,
An object of the present invention is to provide a control device for an electric water heater that can obtain a suitable boiling temperature.

[Summary of the invention]

As per JISC9219, typical electric water heaters are designed to store hot water in a hot water storage tank at a temperature higher than that used on a daily basis. For this reason, when using hot water, it is mixed with water to adjust the temperature before use. Therefore, the amount of hot water stored in the hot water storage tank is less than the amount of hot water actually used.

In addition, this type of electric water heater cannot adjust the amount of hot water it boils, and always boils the entire amount in the hot water storage tank. Therefore, the stored thermal energy can be adjusted by changing the boiling temperature.

In general, the amount of hot water used in households is lower in the summer than in the winter, as people often use water instead of hot water for cooking, cleaning, laundry, etc. It tends to decrease. Therefore, by detecting both the water supply temperature and the outdoor temperature, which has large seasonal variations, the necessary amount of hot water to be supplied commensurate with the amount used can be calculated, and an appropriate boiling temperature can be obtained.

Furthermore, by effectively utilizing the memory element, the number of expensive temperature sensors used can be minimized.

[Embodiments of the invention]

An embodiment of the present invention will be described below with reference to FIGS. 1 and 2.

1 is a hot water storage tank, and heater 2 is inserted inside.
Stores heated water. Hot water tank 1
At the top, there is a hot water outlet pipe 3 for supplying hot water.
A water supply pipe 4 for supplying water into the hot water storage tank 1 is attached to the lower part. Further, a heat insulating material 5 is attached to the outer surface of the hot water storage tank 1 for heat retention.

6 is a temperature sensor, which is influenced by the temperature of hot water in the hot water storage tank 1 near the upper part of the heater 2 due to heat conduction through the hot water storage tank 1, and due to convective heat transfer.
It is installed so that it is affected by the outside temperature.
Furthermore, the heat insulating material 5 is removed from the mounting portion of the temperature sensor 6, making it more susceptible to the influence of outside air temperature.

7 is a control device, and the internal structure of the control device will be explained with reference to FIG.

The comparator 8 compares the temperature detected by the temperature sensor 6 with the data in the lowest temperature storage element 9, updates the lowest temperature sequentially, and stores it in the lowest temperature storage element 9.

The hot water storage tank 1 is filled with hot water when boiling is completed, but by using hot water,
The water flowing in from the water supply pipe 4 sequentially pushes up the hot water from the bottom. Therefore, the data Tmin stored in the minimum temperature storage element 9 has the following meaning.

Tmin=α・Ta+βTw...(1) Here, Ta is the outside temperature and Tw is the water supply temperature. α and β are numerical values indicating the degree of influence of the outside air temperature and the water supply temperature, and are determined by heat conduction and convective heat transfer to the temperature sensor 6. In winter when the outside air temperature is lower than the water supply temperature, the water temperature in the hot water storage tank 1 is cooled by heat radiation and becomes lower than the water supply temperature.

10 is a calculator A that calculates the required amount of hot water at 45°C.
The required amount of hot water V ₄₅ is calculated using the following formula.

V ₄₅ = V ₀ + γ (To-Tmin) ...(2) Here, V ₀ is the standard amount of hot water, which determines the amount of hot water to be used in a day. Also, this value is 45℃
Since it is a value converted to the amount of hot water, it has a value larger than the capacity of the hot water storage tank. γ is a correction coefficient that determines the amount of change in hot water usage due to temperature change, and γ>1
To has the value of , To is the reference temperature, and V ₀ is the determined reference temperature. Therefore, the minimum temperature Tmin
The structure is such that the lower the value, the larger the V ₄₅ becomes.

11 is a calculator B that calculates the boiling temperature, and using the calculation result V ₄₅ of the calculator A ₁₀ and the minimum temperature Tmin, T=V ₄₅ × (45 − Tmin)/V + Tmin ... according to the formula (3) Calculate the boiling temperature T. V here
is the amount of hot water stored in the hot water storage tank 1.

The formula for calculating the boiling temperature Th of hot water of V necessary to obtain hot water V ₄₅ of 45℃ by mixing with water of temperature Tw is Th = V ₄₅ × (45 − Tw) / V + Tw ... (4) However, the calculation unit B11 calculates the boiling temperature T by using Tmin, which is affected by the outside air temperature Ta, instead of Tw in equation (4), so that T and
The difference in Tn is calculated from equations (3) and (4) as follows: T-Tn=(Tw-Tmin)( _V45 /V-1)...(5).

Here, V ₄₅ /V>1.

In winter when the outside air temperature Ta is lower than the water supply temperature Tw, Tw>Tmin, so T>Tn. In addition, in the summer when the outside air temperature Ta is higher than the water supply temperature Tw, Tw < Tmin, so
Conversely, T<Tn.

Reference numeral 12 denotes a heater controller, which energizes the heater 2 and stops energizing the heater 2 when the temperature detected by the temperature sensor 6 rises to the boiling temperature T, which is the calculation result of the calculator B11. be. In winter when the outside air temperature is low, the temperature sensor 6 detects a temperature lower than the hot water temperature in the hot water storage tank 1, so the temperature in the hot water storage tank 1 becomes higher than T, which is the calculation result of the calculator B11.

With the above structure, the amount of hot water that an electric water heater can store is
When converted to the amount of hot water at 45℃, as shown in Figure 3, it can be reduced in summer and increased in winter. The range of change in the amount of stored hot water with respect to temperature can be determined by γ in equation (2) and the degree of influence of the outside temperature and the internal temperature of the hot water storage tank 1 on the temperature sensor 6. Therefore,
By selecting these, the amount of hot water stored can be controlled in accordance with the amount of hot water actually used in the home, and an electric water heater with less residual hot water and less heat loss can be provided.

Moreover, the influence of the outside temperature is the lowest temperature memory element 9,
Arithmetic unit A10, arithmetic unit B11, heater controller 12
Since it acts on four stages, even a small degree of influence can be amplified and a large range of change can be obtained.

Furthermore, in this structure, since the outside air temperature, the water supply temperature, and the tank internal hot water temperature are detected by one temperature sensor 6, it can be manufactured at low cost.

〔Effect of the invention〕

According to the present invention, by detecting the outside temperature and effectively using a memory element, a control device can be provided at low cost that boils water appropriately depending on the season and reduces heat radiation loss due to residual hot water. effective.

[Brief explanation of the drawing]

FIG. 1 is a schematic configuration diagram of an embodiment of the present invention, FIG. 2 is a block diagram of a control device of an embodiment of the present invention, and FIG. 3 is a line showing annual changes in the amount of stored hot water. 2... Heater, 6... Temperature sensor, 9... Minimum temperature storage element, 10, 11... Arithmetic unit, 12...
Heater controller.

Claims (1)

[Claims] 1. In an electric water heater that uses late-night electricity to heat water in a hot water storage tank with a heater, the hot water storage tank has a position near the top of the heater that is thermally affected by both the hot water temperature inside the hot water storage tank and the outside air temperature. A temperature sensor for detecting both the temperature inside the tank and the outside temperature is installed, and a memory element is installed to sequentially update and store the lowest temperature detected by the temperature sensor, and the lowest temperature stored in the memory element is stored in one day. a calculator A that calculates the amount of hot water required for heating, a calculator B that calculates the boiling temperature from the calculation result obtained by the calculator A and the lowest temperature stored in the storage element, and a temperature detected by the temperature sensor. A control device for an electric water heater, comprising: a heater controller that stops energizing the heater when the boiling temperature calculated by a calculator B is reached;