EP0920597B1

EP0920597B1 - An electric water heater

Info

Publication number: EP0920597B1
Application number: EP98924551A
Authority: EP
Inventors: Ilan Paz
Original assignee: S F M Sophisticated Water Meters Ltd
Current assignee: S F M Sophisticated Water Meters Ltd
Priority date: 1997-06-12
Filing date: 1998-06-12
Publication date: 2002-03-06
Anticipated expiration: 2018-06-12
Also published as: IL121064A; IL121064A0; TR199900292T1; AU7672998A; BR9805991A; DE69804074D1; WO1998057100A1; EP0920597A1

Description

Technical Field

The present invention relates to an energy-saving, water heating and storage tank. More particularly, the invention provides an energy-efficient hot water tank, the water therein being heatable either by solar energy, a fossil fuel burner, electrical energy, or a combination of same.

Background Art

Water heaters are widely used in industry and homes, their tank storage capacity being related to the intended use of the water. The most widely used hot water tanks serve a single residence. The capacity of tanks for domestic use in the U.S.A. ranges from 75 to 450 liters (20 to 120 gallons); in Israel, their typical capacity is from 120 to 200 liters. Smaller, electrically heated tanks serving only part of a single residence such as, for example, the kitchen, are made in sizes as small as 30 liters.

All hot water storage tanks are insulated to retain heat from the time of its application until the hot water is required. Present insulation methods are unsatisfactory when heat preservation is required overnight, for example, when water heated by solar energy is required for an early morning shower. Hot water tanks which are exposed to the elements during the winter months tend to lose heat during even shorter periods. This problem can be alleviated by the use of thick insulation; commercially-available water heaters in the U.S.A. use a foam insulation having a thickness of 38 mm. However, the use of thick, high-quality insulation is expensive and also increases the cost of the outer steel tank cover; it may also cause difficulties when the tank needs to be moved through, or installed, in a restricted space.

Furthermore, users of domestic hot water systems have almost no means of knowing how much hot water, if any, is available for use. The water storage tank is usually completely closed, covered with heat insulation material, and often installed in a hard-to-reach location. The common practice is to open a hot water tap, run off all the water contained in the piping leading from the tank, and hand test the water temperature. This method is slow, wasteful and still leaves the user in doubt regarding the quantity of hot water available. Many users switch on the electric heater some time before requiring hot water "just to be sure;" considerable electricity is wasted thereby, either because sufficient hot water is already available, or because the water was cold and a short heating time did not suffice to provide the user's requirements.

Even when the user knows that the tank does not presently hold sufficient hot water to meet his immediate requirements, energizing the heating element will be useless if he is unable to wait until the water is heated. Most hot water tanks need electrical heating for 2-3 hours to obtain even a small quantity of hot water for showering. Such a long wait can be very inconvenient to the user. Long heating times result from the combination of a heating element which is limited to 2000-3000 watts and an arrangement whereby all the water contained in the tank is heated simultaneously.

An energy-saving, water heating and storage tank is disclosed in patent document LU-A-39 847. This water heating and storage tank contains an electric heating element and an outer, an intermediate, and an inner chamber which are series-connected and substantially concentric. Furthermore, it comprises a separate storage chamber in the top section of the tank.

Disclosure of the Invention

It is therefore one of the objects of the present invention to obviate the disadvantages of prior art electric water heaters and to provide a water heating tank with a superior insulation system.

It is a second object of the present invention to provide quick heating of a limited volume of water in a full-sized tank of the type used in private homes.

It is a third object of the present invention to provide a hot water tank offering the user the option of substantially equalizing the temperatures at different tank locations, as is required for some industrial purposes.

A fourth object of the present invention is to provide indicator means for a hot water tank, to give the user information regarding the amount and availability of stored hot water.

The present invention achieves the above objectives by providing an energy-saving, water heating and storage tank containing an electric heating element, said tank comprising a casing including an outer wall, a top and a base, and further including internal divider walls forming outer, intermediate and inner series-connected, substantially concentric chambers, said electric heating element being located in said inner chamber; said tank further comprising a water inlet port near the lower level of said outer chamber and a said inner chamber being sealed at its top and having said water outlet port existing therefrom.

Description of Preferred Embodiments

In a preferred embodiment of the present invention, there is provided a water heating and storage tank further comprising a circulation pump, a manually operable pump control switch and a piping circuit, for allowing the selective, fast circulation of water in series through all three of said chambers.

In another embodiment of the present invention, there is provided a water heating and storage tank further including at least one heat sensor connected to said tank and a display connected to said sensor, indicating the temperature of the water within the tank chamber to which said sensor is attached.

In a further embodiment of the invention, there is provided a water heating and storage tank further including programmable electronic controls for receiving information from at least one heat sensor and controlling said electric heater element, and an automatically operated switch connected to said circulation pump. Such an arrangement may be used to limit the maximum temperature anywhere in the tank to a given selected temperature, for example, to 40°C. Such a temperature limitation has several useful applications, such as preventing discomfort to a user caused by very hot water; saving electricity, when the intention is to use water at the indicated temperature, for example, for bathing; meeting industrial processing needs, and allowing the use of such water on the Jewish Sabbath, the water heater of said embodiment being controllable to meet such a requirement.

It will be realized that the novel hot water tank of the present invention also saves energy by storing the hottest water in the central portion of the tank, from whence it is supplied for consumption. Radial direction heat losses from the central chamber are recovered by the volume of the intermediate chamber; a similar effect occurs between the intermediate and outer chambers. The central chamber of the tank holds enough water for a shower, and can be electrically heated from room temperature in about 20 minutes.

The invention will now be described in connection with certain preferred embodiments with reference to the following illustrative figures so that it may be more fully understood.

With specific reference now to the figures in detail, it is stressed that the particulars shown are by way of example and for purposes of illustrative discussion of the preferred embodiments of the present invention only, and are presented in the cause of providing what is believed to be the most useful and readily understood description of the principles and conceptual aspects of the invention. In this regard, no attempt is made to show structural details of the invention in more detail than is necessary for a fundamental understanding of the invention.

Brief Description of the Drawings

In the drawings:

Fig.1: is a vertical, sectional view of a preferred embodiment of a hot water tank according to the invention;
Fig. 2: is a sectional, diagramatic view of an embodiment of the hot water tank provided with a circulation pump;
Fig. 3: is a sectional, diagramatic view of an embodiment of the hot water tank provided with a heat sensor;
Fig. 4: is a horizontal, cross-sectional view of an embodiment of the invention including a flow diverter;
Fig. 5: is a diagramatic view of an automatic control for the hot water tank, and
Fig. 6: is a vertical, cross-sectional, detailed view of a hot water tank base.

There is seen in Fig. 1 an energy-saving, water heating and storage tank 10 containing an electric heater element 12. The tank 10 has a pressure-resistant casing including an outer wall 14, a top 16 and a base 18.

Internal divider walls

20, 22 form outer chamber 24, intermediate chamber 26 and inner chamber 28, which are series-connected and substantially concentric.

Preferably, internal divider walls 20 comprise a first, hollow cylinder 30 having an open top and a lower flange 32 sealed against the tank casing; a second, inner, hollow cylinder 34, spaced concentrically to and partially overlapping first hollow cylinder 30, having an open base 36 and being sealed to top 16.

The electric heating element 12 is located, as shown, in inner chamber 28, water being admitted via inlet port 38 near the lowest level of outer chamber 24. Hot water is supplied at outlet port 40, situated near the upper level of inner chamber 28.

Advantageously,

divider walls

20, 22 are glass-lined, to prevent rusting and to increase the heat insulation properties of the tank, A safety thermostat 42 shuts off electric power when the heated water reaches the set temperature.

The tank 10 is shown surrounded by a thin layer of low-cost heat insulation 44, such as, for example, rock wool. The casing top 16 is preferably covered by a thicker layer of insulation 46.

With reference to the rest of the figures, similar reference numerals have been used to identify similar parts.

Referring now to Fig. 2, there is seen a water heating and storage tank 48 similar to that described above with reference to Fig. 1, but further provided with a circulation pump 50, a manually-operatable pump control switch 52 and an insulated piping circuit 54, for the selective allowance of fast water circulation in series through all three

tank chambers

24, 26, 28. Piping circuit 54 includes the pump 50 and preferably a one-way valve 56 for preventing incoming cold water from entering outlet port 40 or hot water supply pipe 57. A pressure release valve is connected to casing top 16.

The operation of the circulation pump 50 substantially equalizes the water temperature in all three

chambers

24, 26, 28. For example, if the water in inner chamber 28 is too hot for comfortable bathing, the circulation pump 50 may be operated and will mix the water, thus rectifying the matter.

Fig. 3 illustrates a further embodiment of a water heating and storage tank 58, also similar to that described above with reference to Fig. 1, but further including four

heat sensors

60, 62, 64, 66. Sensors 60-66 suitably comprise temperature sensors, and are attached to water inlet 38, outer casing top 16; and the upper extremity 76 and lower extremity 78 of inner chamber 28.

A signal conditioner 70 amplifies and processes the signals produced by sensors 60-66 as needed. The signals are then transferred to a microcomputer chip 72 for further processing including analogue-digital conversion, computation of temperature and conversion of calculated values, and finally arrive at digital output display 74.

Fig. 4 is a detailed view of a further embodiment of a water heating and storage tank 82. The tank 82 is provided with a flow diverter element 84 adjacent to the inlet port 38. The diverter element 84 directs incoming water into a horizontal, circular flow pattern, thereby reducing undesired mixing of incoming cold water with stored warmer water in the upper part of outer chamber 24.

Fig. 5 illustrates further control means for a water heating and storage tank of the type described above with reference to Fig. 3. User-programmable electronic control 86 receives information from the four heat sensors 60-66 and also from user-operable keyboard 88. Control 86 includes

automatic switches

90, 92, the first automatic switch 90 controlling electric heater element 12 and the second automatic switch 92 operating circulation pump 50. The user-operable keyboard 88 is used to instruct a microcomputer chip 72 regarding future requirements for hot water, its temperature quantity and mixing, if any. Display panel 94 gives status information.

Fig. 6 depicts details of a water heating and storage tank 96 similar to that described above with reference to Fig. 1, wherein a part of the tank base 98 is removable for purposes of cleaning and maintenance. A flexible seal element 100 ensures leak-free re-closure. Precipitated salts and other solid particulates 102 accumulating in the lower part of tank 96 can thus be readily removed.

Claims

An energy-saving, water heating and storage tank (10) containing an electric heating element (12), said tank comprising:

a casing including an outer wall (14), a top (16) and a base (18), and further including internal divider walls (20, 22) forming outer (24), intermediate (26) and inner (28) series-connected, substantially concentric chambers, said electric heating element (12) being located in said inner chamber (28);

said tank further comprising a water inlet port (38) near the lower level of said outer chamber (24), said inner chamber being sealed at its top and having said water outlet port (40) exiting therefrom.
A water heating and storage tank according to claim 1, wherein said internal divider walls comprise a first hollow cylinder (30) having an open top and a lower flange (32) sealed against said tank casing, and an inner second hollow cylinder (34), spaced concentrically to and partially overlapping said first hollow cylinder (30), having an open base and being sealed to said tank top (16).
A water heating and storage tank according to claim 1, further provided with a circulation pump (50), a manually-operable pump control switch (52) and a piping circuit (54), for the selective allowance of fast water circulation in series through all three of said chambers (24, 26, 28).
A water heating and storage tank according to claim 1, further provided with at least one heat sensor (60, 62, 64, 68) connected to said tank and a display (74) connected to said sensor, indicating the temperature of the water within the tank chamber to which said sensor is attached.
A water heating and storage tank according to claim 1, further provided with a flow diverter element (84) adjacent said inlet port (38), said diverter element (84) directing incoming water into a horizontal, circular flow pattern.
A water heating and storage tank according to claim 4, further provided with programmable electronic controls (86) receiving information from said at least one heat sensor (60, 62, 64, 68) and from a user-operable keyboard (88), for controlling both said electric heater element (12) and a circulation pump (50) provided with an automatically-operated switch (90, reap. 92).
A water heating and storage tank according to claim 1, wherein said tank base (98) is removable for purposes of cleaning and maintenance.