JPH06317354A - Electric water-heater - Google Patents

Abstract

PURPOSE:To obtain an electric water-heater having a system wherein a no-water heating preventing function operates normally even when the water heaters are connected in series for the use or when a solar-heat water heater or the like is connected thereto for the use. CONSTITUTION:This electric water heater is so constructed that electrification of an electric heater 2 is stopped on the basis of judgement of a state of no- water heating when both rise rates of temperature computed on the basis of two kinds of sensor outputs of a temperature sensor THC for control disposed in the vicinity of the electric heater 2 in the lower part of a hot water storage tank 1 and of a temperature sensor TH1 (TH2, TH3) for detecting the quantity of residual hot water which is positioned in the upper part of the tank are reference values or above.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an electric water heater provided in a general house or the like, and more particularly to a hot water storage type electric water heater having an emptying prevention function.

[0002]

2. Description of the Related Art As an electric water heater installed in a general house, a hot water storage tank having a water supply port at the bottom and a hot water outlet at the top, and an electric heater attached to the bottom of the tank are provided. There is a hot water storage type water heater having a structure in which water stored in a hot water storage tank is heated by a heater, and the convection of water caused by this heating raises the entire water in the tank to a boiling temperature.

Further, this kind of electric water heater usually has an emptying prevention function. As a method for preventing the air-drying, conventionally, a temperature sensor is arranged in the vicinity of the electric heater, the temperature rise (change) per unit time is calculated from the sensor output, and the temperature rise value is equal to or higher than the reference value. A system has been proposed in which the electric power to the electric heater is stopped when the temperature becomes low to prevent the heater from being damaged (for example, JP-A-2-130343).

[0004]

According to the above-mentioned proposed technique, when the electric water heater (one hot water storage tank) is used alone, the emptying prevention function normally operates. When the electric water heaters are connected in series and used, or when other water heaters such as a solar water heater are connected and used, the emptying prevention function may malfunction.

That is, according to the proposed technique, the reference value when the power supply to the heater is stopped is normally the normal temperature rise rate dT ₁ when water is present in the tank, and the empty value as shown in FIG. The value is set to a value between the temperature rise rate dT ₂ and the temperature rise rate dT ₃ when the hot water flows into the hot water supply port of the hot water storage tank. As shown in the figure, the temperature rise rate dT ₂ at the time of emptying may be higher, and in such a case, there is water in the hot water storage tank If it is determined that there is such a malfunction, a malfunction occurs such that power supply to the heater is stopped.

The present invention has been made in view of such circumstances, and an object thereof is to connect a water heater in series or to use a solar water heater or the like. Even so, it is to provide an electric water heater with a system in which the emptying prevention function operates normally.

[0007]

A structure for achieving the above object will be described with reference to FIG. 1 corresponding to an embodiment. The electric water heater of the present invention is arranged in the vicinity of the electric heater 2. Control temperature sensor TH _C , and remaining hot water amount detection temperature sensor TH ₁ (TH
₂ ), TH ₃ ) from each output, the calculation means 3 for obtaining the temperature change (increase) per unit time, and the electric heater when the calculated values based on the outputs of these two types of sensors both exceed the reference value. It is characterized by the fact that the control means 4 for stopping the energization of 2 is provided.

[0008]

[Function] First, when empty, water is present in the hot water storage tank 1.
Therefore, the convection of the air heated by the heater 2
The temperature inside the tank is almost uniform. On the other hand, hot water storage
When tank 1 is full of water,
When hot water flows into the tank from the water supply port 1a, the water at the bottom of the tank
The temperature rises rapidly, but the sensor TH for detecting the amount of remaining hot water ₁~ T
H₃The upper part of the tank 1 where the
No change appears. Therefore, in the present invention, such a phenomenon
Using the temperature sensor at the bottom of the tank (for control) TH
_CAnd the temperature sensor at the top (for residual hot water detection) TH₁(TH₂, TH₃)of
The rate of temperature rise based on the outputs of the two types of sensors is both below the reference value.
Only when it is above, it is judged that it is empty.

[0009]

1 is a block diagram of an embodiment of the present invention. The hot water tank 1 has a water inlet 1a at the bottom and a tap 1 at the top.
b are provided respectively. An electric heater 2 is mounted below the hot water storage tank 1.

Further, the hot water storage tank 1 is provided with residual hot water sensors (temperature sensors) TH ₁ , TH ₂ , TH ₃ for detecting the amount of hot water remaining from the upper portion in units of 50 liters up to 150 liters. Further, in the hot water storage tank 1, control sensor in the vicinity of the heater 2 (temperature sensor) TH _C are arranged, these sensors TH _C, the detection output of the TH ₁ to TH ₃ is input to the arithmetic unit 3 It

The calculation unit 3 obtains a temperature change (rate of increase) per unit time for each sensor based on the output of each sensor, and outputs each calculated value to the control unit 4.
The control unit 4 compares each input calculation value with the reference value (see FIG. 2 above), and only when the calculation values based on all the sensor outputs are equal to or larger than the reference value When it is determined that the electric heater 2 is present, the power supply to the electric heater 2 is stopped, and a drive command signal is output to an alarm buzzer, an abnormality display lamp (not shown), or the like.

Each function of the arithmetic unit 3 and the control unit 4 may be achieved by a single dedicated controller, but in consideration of operability in use and cost.
It is preferable to add those functions to a remote controller (not shown) of the electric water heater itself, and to display that fact on a remote controller when empty.

Here, in the above embodiment, all sensor outputs of the _three remaining hot water sensors TH ₁ , TH ₂ , TH ₃ are used to prevent emptying, but the present invention is not limited to this. It is also possible to represent one residual hot water sensor, for example, the residual hot water sensor (for 50 liters) TH ₁ at the top of the tank, and use the sensor outputs of the residual hot water sensor TH ₁ and the control sensor TH _C. Even if the number of remaining hot water sensors is one or more, the present invention can be implemented as long as there are two types of sensor outputs, that is, the remaining hot water sensor in the upper tank and the control temperature sensor in the lower tank. is there.

[0014]

As described above, according to the electric water heater of the present invention, the temperature sensor for control disposed near the electric heater in the lower part of the hot water storage tank and the temperature sensor for detecting the amount of remaining hot water located in the upper part of the tank. Since the empty state is judged when both the temperature increase rates calculated based on the outputs of the two types of sensors are above the reference value, only the temperature around the heater, that is, the lower part of the tank rises partially and rapidly. However, the air-drying prevention function does not work, so even when using water heaters connected in series or when connecting other water heaters such as solar water heaters, The blanking prevention function does not malfunction.

[Brief description of drawings]

FIG. 1 is a configuration diagram of an embodiment of the present invention.

FIG. 2 is a graph showing a temperature change in the vicinity of the heater of the hot water storage tank.

[Explanation of symbols]

1 ... ・ Hot water storage tank 1a ・ ・ ・ ・ Hot water supply port 1b ・ ・ ・ ・ Hot water outlet 2 ・ ・ ・ ・ Electric heater 3 ・ ・ ・ ・ ・ ・ Calculation unit 4 ・ ・ ・ ・ ・ ・ Control unit TH ₁ , TH ₂ , TH ₃・ ・ ・ ・ Remaining hot water sensor (temperature sensor) TH _C・ ・ ・ ・ Control sensor (temperature sensor)

Claims (1)

[Claims] 1. A hot water storage tank having a water supply port at the bottom and a hot water outlet at the top, and an electric heater arranged at the bottom of the hot water storage tank, and for detecting the amount of remaining hot water at the top of the tank. In the water heater in which the temperature sensor is arranged, the temperature change per unit time from the control temperature sensor arranged in the vicinity of the electric heater and each output of this sensor and the remaining hot water amount detection temperature sensor. An electric water heater, which is provided with a calculating means for obtaining the electric current and a control means for stopping energization to the electric heater when the calculated values based on the outputs of these two types of sensors are both equal to or larger than a reference value. .