WO2013136323A1

WO2013136323A1 - A residential water heater and heating method

Info

Publication number: WO2013136323A1
Application number: PCT/IL2013/000030
Authority: WO
Inventors: Orna Victoria ZADEEK; Sion RAHIMI
Original assignee: Zadeek Orna Victoria; Rahimi Sion
Priority date: 2012-03-13
Filing date: 2013-03-11
Publication date: 2013-09-19
Also published as: IL218615A0

Abstract

A residential water heater comprising an insulated tank, for containing water to be heated; at least one partition of said tank, for dividing said tank into at least two sub-tanks, said division substantially not allowing water transition therebetween; an individual heating apparatus for each of said at least two sub-tanks; and a selecting mechanism for selecting one of said at least two sub-tanks as the current sub-tank for dispensing the heated water therefrom, thereby obtaining higher temperature of primary water to be dispensed from said tank at less power than heating an un-partitioned tank.

Description

A RESIDENTIAL WATER HEATER AND HEATING

METHOD

Field of the Invention

The present invention relates to the field of residential water heaters. More particularly, the invention relates to a method and apparatus for accelerating heating.

Background of the Invention

A conventional water heater, used particularly for body washing, includes a tank, a heating element, an inlet and an outlet. The volume thereof is a few dozens of liters, typically between 30 and 150 liters.

Upon use of removing heated water from the outlet of the tank, cold water must be inserted into the inlet of the tank for maintaining the water flow, since air holes block the water flow.

The insertion of cold water cools the heated water. Thus, 20 the water must be heated in advance before washing to a temperature above the comfort temperature.

Another problem is that substantially the entire volume of the tank must be heated in order to supply a small amount of heated water.

Selection of a small volume tank, e.g., 30 liters, provides heated water in a short period. However, this is a small amount. A large volume, e.g., 150 liters, is selected to allow several users to wash, one after the other. However this extends the period for providing heated water for use.

A known solution is providing an "accelerating sleeve", which is a sleeve surrounding the heating element. The sleeve gathers the heated water into a certain zone shaped like a sleeve having openings to a non-heated water zone. The outlet of the tank is disposed near the high openings of the sleeve.

However, the accelerating sleeve does not constitute a 10 real separation between the cold and the heated water. Also, after a period of minutes or hours the cold and the heated water mix.

All the methods described above have not yet provided satisfactory solutions to the long felt need of swift heating together with providing a large volume of heated water. It is an object of the present invention to provide a method and apparatus for providing swift heating together with providing a large volume of heated water.

It is an object of the present invention to provide a 20 solution to the above- mentioned and other problems of the prior art.

Other objects and advantages of the invention will become apparent as the description proceeds.

Summary of the Invention

In one aspect, the present invention IS directed to a residential water heater (10) comprising: an insulated (30) tank ( 16), for containing water to be heated;

at least one partition (60) of the tank (16), for dividing the tank (16) into at least two sub-tanks (5SA, 5SB, 5SC), the division substantially not allowing water transition therebetween;

an individual heating apparatus (26 A, 26B, 26C) for each of the at least two sub-tanks (5SA, 5 SB, 5SC); and

a selecting mechanism (20, 56A, 56B, 56C, 50) for selecting one of the at least two sub-tanks (5SA, 5SB, 5SC) as the current sub-tank for dispensing the heated water therefrom, thereby obtaining higher temperature of primary water to be dispensed from the tank (16) at less power than heating an un-partitioned tank.

The selecting mechanism (20, 56A, 56B, 56C, 50) may comprise: a temperature sensor (56A, 56B, 56C) of each of the at least two sub-tanks (5SA, 5SB, 5SC), for measuring temperature of each of the at least two sub- tanks (5SA, 5SB,5SC), thereby providing data for the selection.

The data for the selection of one of the at least two sub-tanks (5SA, 5 SB, 5SC) may comprise the sub-tank with the highest temperature measurement.

The residential water heater (10) may further comprise:

a first inlet (72), for receiving, from a water supply network, non-heated water into the tank (16);

a first outlet (22), for supplying heated water therefrom, for the dispensing, thereby the at least two sub-tanks (58 A, 58B, 58C) are used by a single first inlet pipe (42) and a single first outlet pipe (44).

The residential water heater (10) may further comprise: a first manifold (14), for distributing the non-heated water from the first inlet (72) into the at least two sub-tanks (58 A, 58B, 58C); and

a second manifold (20), for accumulating the heated water from the at least two sub-tanks (58A, 58B, 58C) into the first outlet (22), thereby providing the dispensing from the at least two sub-tanks (58A, 58B, 58C) by the first inlet pipe (42) and the first outlet pipe (44).

The selecting mechanism (20, 56 A, 56B, 56C, 50) may comprise:

a first water selector (20) for allowing flowing the water 25 from the first inlet (72) into the first outlet (22) through only one or more of the at least two sub-tanks (58A, 58B, 58C), thereby allowing avoiding provision of water to the outlet pipe (44) from a non- heated sub-tank (52B).

The heating apparatus (26A) may comprise a heating element.

The heating apparatus (26 A) may further comprise an accelerating sleeve (28A), thereby accelerating the heating in each of the sub-tanks ( 8A, 58B).

The heating apparatus (26 A) may comprise a closed water loop (42, 58 A, 46, 66) for flowing water contained in the one (58 A) of the at least two sub-tanks (58 A, 58B, 58C) through a solar collector (66) heating the water.

The residential water heater (10) may further comprise:

a second inlet (76), for receiving heated water into the tank (16) from the solar collector (66);

a second outlet (74), for transferring non-heated water to the solar collector (66), 20 thereby the at least two sub-tanks (58A, 58B, 58C) use a single second inlet pipe (48) and a single second outlet pipe (46).

The residential water heater (10) may further comprise:

a third manifold (54), for accumulating the heated water from the second inlet (76) into the at least two sub-tanks (58A, 58B, 58C);

a fourth manifold (70), for distributing the non-heated water from the at least two sub-tallks (58A, 58B, 58C) illto the second outlet (74); and

a second water selector (54) for allowing flowing the 5 water from the second inlet (76) into the second outlet (74) through one or more of the at least two sub-tanks (58A, 58B, 58C). thereby allowing using the solar collector (66) for heating only one of the at least two sub-tanks (58A, 58B, 58C) 10 without mixing non-heated water of other sub- tanks. The residential water heater (10) may further comprise:

a controller (50), for controlling at least one of the first water selector (20) and the heating apparatuses (26A, 15 26B, 26C).

The first water selector (20) and the heating apparatuses (26A, 26B,26C) may be controlled manually.

The first water selector (20) may comprise a plurality of faucets.

The first water selector (20) may comprise:

a plurality of inlets/outlets (32A, 32B, 32C);

one outlet/inlet (22); and

a rotatable block (34) comprising a gateway (40) allowing flow between the one of the inlets/outlets (32A, 32B, 32C) and the outlet/inlet (22).

In another aspect, the present invention is directed to a method for heating water, the method comprising the steps of: providing an insulated (30) tank (16) partitioned to a plurality of sub-tanks (58A, 58B, 58C);

selecting one of the at least two sub-tanks (58A, 58B, 58C) as the current tank from which heated water is to be dispensed;

heating water of the selected one of the at least two sub-tanks (58 A, 58B, 58C); and

dispensing water from the selected one of the at least two sub-tanks (58 A, 58B, 58C), thereby obtaining higher temperature of primary water to be dispensed from the tank (16) at less power than heating an un-partitioned tank..

The step of heating water of one of the at least two sub-tanks (58A, 58B, 58C) may comprise turning on a heating element disposed in the one of the at least two sub-tanks (58A, 58B, 58C).

The step of heating water of one of the at least two sub-tanks (58A, 58B, 58C) may comprise flowing water contained in the one (58 A) of the at least two sub- tanks (58 A, 8B, 58C) through a solar collector (66) in a closed loop.

The method for heating water may further comprise the step of:

measuring temperatures of each of the at least two sub-tanks (58A, 8B, 58C), thereby providing data for selecting the one of the at least two sub-tanks (58 A, 58B, 58C) to flow the water therethrough. The step of selecting the one of the at least two sub-tanks (58A, 58B, 58C) may comprise selecting the sub-tank having the highest temperature measurement.

The step of selecting the sub-tank having the highest 10 temperature measurement may comprise selecting another sub-tank upon exceeding a desired maximum temperature.

The method for heating water may further comprise the step of heating water of a sub-tank other than the selected one of the at least two sub-tanks (58A, 58B, 58C).

The reference numbers have been used to point out elements in the embodiments described and illustrated herein, in order to facilitate the understanding of the invention. They are meant to be merely illustrative, and not limiting. Also, the foregoing embodiments of the invention have been described and illustrated in conjunction with systems and methods thereof, which are meant to be merely illustrative, and not limiting.

Brief Description of the Drawings

Embodiments and features of the present invention are described herein in conjunction with the following drawings:

Fig. 1 is a perspective bottom view of a residential water heater, according to one embodiment of the present invention.

Fig. 2 is a cut sectional view of the selector of Fig. 1, according to one embodiment.

Fig. 3 depicts a prior art water heater, including a solar collector.

Fig. 4 is a perspective bottom View of a residential water heater, according to another embodiment of the present invention.

Fig. 5 is a sectional cut view from the top of the water heater of Fig. 4.

Fig. 6 depicts the water heater of Fig. 4 connected to a solar collector.

Fig. 7 depicts the water heater of Fig. 4 connected to solar collectors according to another embodiment.

It should be understood that the drawings are not necessarily drawn to scale. Detailed Description of Preferred Embodiments The present invention will be understood from the following detailed description of preferred embodiments, which are meant to be descriptive and not limiting. For the sake of brevity, some well-known features, methods, systems, procedures, components, circuits, and so on, are not described in detail.

The terms "inlet" and "outlet" relate herein to a tank. For example, an inlet inserts water into a tank.

A residential water heater 10 includes a main tank 16 including a plurality of sub- tanks 58A, 58B, 58C, etc. According to the example in the figures, tank 16 includes three separate sub-tanks 58A, 58B and 58C. Each of sub-tanks 58A, 58B and 58C has a separate inlet, a separate outlet, and a separate heating apparatus. Namely in the example of three sub-tanks, sub-tank 58A has an inlet 24 A, an outlet 18A, and a heating apparatus 26A; sub-tank 58B has an inlet 24B, an outlet 18B, and a heating apparatus 26B; and sub-tank 58C has an inlet 24C, an outlet 18C, and a heating apparatus 26 C.

Each of heating apparatuses 26A, 26B, and 26C may include a heating element, a thermostat, and a sleeve and a flange therefor.

Upon opening a tap in the house, an outlet pipe 44 receives heated water only from one of sub-tanks 58 A, 58B or 58C, thus from outlet 18 A, or 18B orl8C. Upon removal of water from one of sub-tanks 58 A, 58B or 58C only, that tank receives cold water from an inlet pipe 42 for complementing the dispense of water.

Thus, this flow of water from inlet pipe 42 to outlet pipe 44 is directed either through sub-tank 58A, or through sub-tank 58B or through sub-tank 58C. A water selector 20 directs the water either through sub-tank 58 A, or through sub-tank 58B or through sub-tank 58C.

According to the embodiment of Fig. 1 water selector 20 directs the water from one of outlets 18A, 18B or 18C towards outlet pipe 44. According to this embodiment inlet pipe 42 is connected to inlets 24A, 24B, and 24C via an inlet 72 directing to a manifold 14. However, only the tank that water selector 20 has directed the water from the outlet thereof, receives the cold water to the inlet thereof.

For example, if water selector 20 has directed the water 20 from outlet 18A towards outlet pipe 44, then inlet pipe 42 supplies cold water to inlets 24A, 24B, and 24C altogether via manifold 14; however, only sub-tank 58A receives the cold water, and this is via inlet 24A.

Thus, this embodiment includes manifold 14 for inserting water; and water selector 20 being another manifold, however allowing only one of outlets 18A, 18B or 18C release water out.

According to another embodiment (not shown), a water selector may direct incoming water from inlet pipe 42 only to one of inlets 24A, 24B, or 24C. According to this embodiment outlet pipe 44 may supply heated water to outlets 18A, 18B, 5 and 18C altogether via a manifold.

Thus, this embodiment includes the water selector being a manifold for inserting water, however allowing only one of inlets 24A, 24B or 24C insert water; and another manifold for taking water out.

The following description refers to the first embodiment, in which water selector 20 directs the water from one of outlets 18 A, 18B or 18C towards outlet pipe 44.

Fig. 2 is a cut sectional view of the selector of Fig. 1 according to one embodiment.

Water selector 20 provides a gateway 40 either between inlet 32A and outlet 22 thereof as shown in Fig. 2, or between inlet 32B and outlet 22 thereof, or between inlet 32C and outlet 22 thereof.

According to the example of Fig. 2, water selector 20 includes a rotatable block 34 including gateway 40. At the state shown in Fig. 2, block 34 blocks water flow between inlet 32B and outlet 22, and water flow between inlet 32C and outlet 22 (not shown). However, gateway 40 is disposed to allow water flow between inlet 32A and outlet 22.

Block 34 is rotatable about a hinge 38. The rotation may be mechanical or applied by a motor 36, which may be controlled by a controller 50.

According to another embodiment, water selector 20 may 5 constitute a separate faucet. Instead of the example of Fig. 2, a faucet receiving water from outlet 18A will be open, and the faucets receiving water from outlets 18B and 18C will be closed.

The control which of sub-tanks 58 A, 58B or 58C will supply the heated water to outlet pipe 44 may be supported by a temperature sensor 56A preferably attached to outlet 18A for sensing the water temperature of sub-tank 58 A; by a temperature sensor 56B preferably attached to outlet 18B for sensing the water temperature of sub-tank 58B; and by a temperature sensor 56C preferably attached to outlet 18C for sensing the water temperature of sub-tank 58C.

Preferably, a controller 50 receiving information from temperature sensors 56A, 56B and 56C via wiring 62, will activate motor 36 of selector 20, for supplying water of the 20 selected tank having the highest temperature.

Preferably, according to the same approach, controller 50 will select the appropriate heating apparatus, being either 26A, 26B or 26C, for heating the tank having already the highest temperature. Upon exceeding a desired maximum temperature, controller 50 may select another heating apparatus.

For example, if temperature sensor 56A measures 40 degrees C, sensor 56B measures 30 degrees C, sensor 56B measures 25 degrees C, then controller 50 will turn on heating apparatus 26A, which, according to the example, is the heating element within sub-tank 58 A. Upon exceeding 70 degrees C, controller 50 will turn off heating apparatus 26A, and turn on heating apparatus 26B.

According to another embodiment, the selection both of the sub-tank from which heated water is removed, and of the 10 sub-tank to be heated may be performed manually.

Tank 16 is advantaged of obtaining a high temperature of the selected sub-tank in a short period. However, all sub-tanks may dispense water. Thus, this advantage is for dispensing the primary water from tank 16, requiring less power than heating an un-partitioned tank, in which the heated and the non-heated water is mixed.

This is in contrast to the accelerating sleeve which must allow free transition between the heated and the non-heated volumes. The accelerating sleeve does not constitute a real 20 separation between the cold and the heated water, that after a period of minutes or hours the cold and the heated water mix.

Fig. 3 depicts a prior art water heater, including a solar collector.

A water heater which does not include solar heating includes inlet pipe 42 and outlet pipe 44, both being open loop pipes, since inlet pipe 42 supplies water from the water supply network, and outlet pipe 44 provides water to the tap.

A water heater which includes solar heating includes except for inlet pipe 42 and outlet pipe 44 being open loop pipes - as well an inlet pipe 48 and an outlet pipe 46, being closed loop pipes.

Relatively cold water exiting the bottom of the tank is inserted into the bottom of a solar collector 66 via outlet pipe 42. The water heated by the sun is raised within pipes in solar collector 66 and exit solar collector 66 at the top thereof. The heated water flows via inlet pipe 48 to solar inlet 12A of the tank disposed substantially at the top of the tank. This water circulation is a closed loop which can work without providing energy.

In contrast to the prior art tank of Fig. 3, water heater 10 of the present invention for solar heating includes one inlet and outlet for each of sub-tanks 58A, 58B and 58C, namely, solar inlet 12A and solar outlet 68A for sub-tank 58 A, solar inlet 12B and solar outlet 68B for sub-tank 58B, and solar inlet 12C and solar outlet 68C for sub-tank 58C.

Fig. 5 is a sectional cut view from the top of the water 25 heater of Fig. 4.

Sub-tanks 58A, 58B, and 58C are sub-tanks within a main tank 16 having a single insulating envelope 30. Partitions 60 screen sub-tanks one from the other, thus, each of sub-tanks 58 A, 58B and 58C may substantially be heated separately. Partitions 60 are preferably deployed vertically, such that the sub-tanks are disposed one beside the other and not one above the other, thus providing that each sub-tank has a sufficient length providing a vertical path for the heated water to raise therein.

Partitions 60 provide a division between the sub-tanks, substantially not allowing water transition therebetween.

However, according to one embodiment, partitions 60 need not separate the sub- tanks in a qualitative manner. The reason is that the volume of one tank may not be sufficient, thus the other sub-tanks may be used, and thus slight dripping of heat or even of water from one tank to another may not be regarded, according to one embodiment, as a real loss of energy.

According to the same approach, sub-tanks need not be heat insulated one from the other.

According to the same approach, according to one embodiment, lack of significant transition between the sub-tanks may be a sufficient requirement.

According to one embodiment, each of heating apparatuses 26A, 26B, and 26C may include a heating element which typically is of a resistive type, a thermostat, and a sleeve and a flange therefor. These are shown in Fig. 5 by accelerating sleeves 28 A, 28B and 28 C. An accelerating sleeve is a prior art sleeve which directs the heat produced by the heating element to a small volume within the tank.

According to the solar embodiment of Fig. 4, each of heating apparatuses 26A, 26B, and 26C may include a separate solar heating loop, part of which includes solar inlet 12A to sub-tank 58 A, solar inlet 12B to sub-tank 58B, and solar inlet 12C to sub-tank 58C.

Fig. 6 depicts the water heater of Fig. 4 connected to a 10 solar collector.

According to the above example that temperature sensor 56 A has measured 40 degrees C, sensor 56B has measured 30 degrees C, and sensor 56B has measured 25 degrees C, controller 50 will turn on heating apparatus 26A by opening the water loop of solar inlet 12 A. Upon the above example of then exceeding 70 degrees C, controller 50 will turn off heating apparatus 26 A by closing the water loop of solar inlet 12A, and turn on heating apparatus 26B by opening the water loop of solar inlet 12B.

Opening and closing the water loop may be accomplished by using another water selector 54. Thus, the water selector 20 selects the open loop from the three available, and water selector 54 selects the closed loop from the three available.

Water selector 54 may as well be controlled by controller 25 50. As described in Fig. 2, the control may be equal; meaning that upon selecting sub-tank 58A to supply water, sub-tank 58A preferably may also be selected for flowing heated water from solar collector 66 through sub-tank 58A.

Fig. 6 shows inlet pipe 48 of the closed loop extending from the top of solar collector 66 to an inlet of water selector 54; water selector 54 directs the heated water from solar collector 66 either to inlet pipe 64A for entering sub-tank 58 A, or to inlet pipe 64B for entering sub-tank 58B, or to inlet pipe 64C for entering sub- tank 58C.

Upon this entry of heated water from collector 66 into one of sub-tanks 58 A, 58B or 58C only, that tank pushes out the same amount of water via outlet pipe 46. Referring to Fig. 4, according to this embodiment, outlet pipe 46 pushes out relatively cold water from outlets 68A, 68B, and 68C altogether via a manifold 70. Outlet pipe 46 is connected to outlets 68A, 68B, and 68C via an outlet 74 via manifold 70. However, only the tank that water selector 54 has directed the water to the inlet thereof, pushes the cold water out of the outlet thereof.

Water selector 54 may be regarded as a manifold-like water selector 20, however allowing only the selected path. For example, if water selector 54 has directed the heated water from solar collector 66 to inlet pipe 64A for entering sub-tank 58A, then only sub-tank 58A pushes out water via outlet pipe 46. Outlet pipe 46 pushes out relatively cold water from all outlets 68A, 68B, and 68C altogether via manifold 70.

However, only sub -tank 58A pushes the cold water out, and this is via outlet 68 A.

Fig. 7 depicts the water heater of Fig. 4 connected to solar collectors, according to another embodiment.

The embodiment of Fig. 6 describes how a single solar collector 66 heats the water of any of sub-tanks 58A, 58B and 58C. According to the embodiment of Fig. 7, a separate solar collector may be associated with each of sub-tanks 58A, 58B and 58C. Thus, each sub-tank and each solar collector has a separate inlet piping and a separate outlet piping.

In the figures and/or description herein, the following reference numerals have been mentioned: numeral 10 denotes a residential water heater according to one embodiment of the present invention;

numerals 12 A, 12B, and 12C denote inlets to the water heater from a solar collector;

numeral 14 denotes a water manifold;

numeral 16 denotes a tank, including a plurality of sub-tanks;

numerals 18A, 18B, and 18C denote outlets of the open loop of the water heater, for supplying heated water;

numeral 20 denotes a water selector for supplying heated water to a tap used by a user; the water selector may be regarded as a manifold, however, allowing flow of only one of the paths;

numeral 22 denotes an outlet of a water selector;

numerals 24A, 24B, and 24C denote inlets of the open loop of the water heater, for supplying water from the water network to the water heater;

numerals 26A, 26B, and 26C denote heating apparatuses, each for a different tank; according to one embodiment, the heating apparatuses constitute heating elements; according to another embodiment, the heating apparatuses constitute different channels to the solar collector;

numerals 28A, 28B, and 28C denote accelerating sleeves;

numeral 30 denotes a shared heat insulation surrounding the plurality of the sub-tanks;

numerals 32A, 32B, and 32C denote outlets of the water selector, each for supplying heated water from another tank;

numeral 34 denotes a rotatable block of the water selector;

numeral 36 denotes a motor;

numeral 38 denotes a hinge; numeral 40 denotes a gateway within the water selector;

numeral 42 denotes an inlet pipe of the open loop, for supplying water to the water heater for the water network;

numeral 44 denotes an outlet pipe of the open loop, for providing heated water to the user;

numeral 46 denotes an outlet pipe of the closed loop, for providing relatively cold water to the solar collector;

numeral 48 denotes an inlet pipe of the closed loop, for providing water heated by the solar collector to the tank;

numeral 50 denotes a controller;

numeral 52 denotes a hollowed sealing rubber;

numeral 54 denotes a water selector, for selecting the closed loop, i.e., the tank which exchanges water with the solar collector; the water selector may be regarded as a manifold, however allowing flow of only one of the paths; numerals 56A, 56B, and 56C denote temperature sensors, each for measuring the temperature of one tank; typically each temperature sensor may be disposed on the outlet of the measured tank;

numerals 58A, 58B, and 8C denote water sub-tanks numeral 60 denotes a partition between two water sub-tanks; numeral 62 denotes electric wiring; numerals 64A, 64B, and 64C denote inlet pipes from the solar collector, each for a tank;

numeral 66 denotes a solar collector;

numerals 68A, 68B, and 68C denote outlets from the water sub-tanks to the solar collector;

numeral 70 denotes a manifold for unifying the outlets of the closed loop; numeral 72 denotes an inlet, via which the open loop inlet pipe inserts water to the sub-tanks;

numeral 74 denotes an inlet, via which the closed loop inlet pipe inserts water into the sub-tanks;

numeral 76 denotes an inlet into which the inlet pipe of the closed loop from the solar collector enters;

The foregoing description and illustrations of the embodiments of the invention has been presented for the purposes of illustration. It is not intended to be exhaustive or to limit the invention to the above description in any form.

Any term that has been defined above and used in the claims, should to be interpreted according to this definition.

The reference numbers in the claims are not a part of the claims, but rather used for facilitating the reading thereof.

These reference numbers should not be interpreted as limiting the claims in any form.

Claims

What is claimed is: CLAIMS

1. residential water heater (10) comprising:

- an insulated (30) tank (16), for containing water to be heated;

- at least one partition (60) of said tank (16), for dividing 10 said tank (16) into at least two sub-tanks (58 A, 58B, 58C), said division substantially not allowing water transition therebetween;

- an individual heating apparatus (26A, 26B, 26C) for each of said at least two sub-tanks (58A, 58B, 58C); and

- a selecting mechanism (20, 56A, 56B, 56C, 50) for selecting one of said at least two sub-tanks (58A, 58B, 58C) as the current sub-tank for dispensing the heated water therefrom,

thereby obtaining higher temperature of primary water to be dispensed from said tank (16) at less power than heating an un-partitioned tank.

2. A residential water heater (10) according to claim 1, wherein said selecting mechanism (20, 56A, 56B, 56C, 50) comprises:

- a temperature sensor (56A, 56B, 56C) of each of said at least two sub- tanks (58A, 58B, 58C), for measuring temperature of each of said at least two sub-tanks (58A, 58B, 58C), thereby providing data for said selection.

3. A residential water heater (10) according to claim 2, wherein said data for said selection of one of said at least two sub-tanks (58A, 58B, 58C) comprises which sub-tank has the highest temperature measurement.

4. A residential water heater ( 10) according to claim 1 , further comprising:

- a first inlet (72), for receiving, from a water supply network, non-heated water into said tank (16);

- a first outlet (22), for supplying heated water therefrom, for said dispensing, thereby said at least two sub-tanks (58 A, 58B, 58C) are 15 used by a single first inlet pipe (42) and a single first outlet pipe (44).

5. A residential water heater (10) according to claim 4, further comprising:

- a first manifold (14), for distributing said non-heated water from said first inlet (72) into said at least two sub-tanks (58A, 58B, 58C); and

- a second manifold (20), for accumulating said heated water from said at least two sub-tanks (58A, 58B, 58C) into said first outlet (22), thereby providing said dispensing from said at least two sub-tanks (58A, 58B, 58C) by said first inlet pipe (42) and said first outlet pipe (44).

6. A residential water heater (10) according to claim 4, wherein said selecting mechanism (20, 56A, 56B, 56C, 50) comprises:

- a first water selector (20) for allowing flowing said water from said first inlet (72) into said first outlet (22) through only one or more of said at least two sub-tanks (58A, 58B, 58C), thereby allowing avoiding provision of water to said outlet pipe (44) from a non-heated sub-tank (52B).

7. A residential water heater (10) according to claim 1, wherein said heating apparatus (26 A) comprises a heating element.

8. A residential water heater (10) according to claim 7, wherein said heating apparatus (26A) further comprises an accelerating sleeve (28A), thereby accelerating the heating in each of said sub-tanks (58 A, 58B).

9. A residential water heater (10) according to claim 1, wherein said heating apparatus (26A) comprises a closed water loop (42, 58A, 46, 66) for flowing water contained in said one (58A) of said at least two sub-tanks (58A, 58B, 58C) through a solar collector (66) heating said water.

10. A residential water heater ( 10) according to claim 9, further comprising:

- a second inlet (76), for receiving heated water into said tank (16) from said solar collector (66);

- a second outlet (74), for transferring non-heated water to said solar collector (66), thereby said at least two sub-tanks (58A, 58B, 58C) use a single second inlet pipe (48) and a single second outlet pipe (46).

11. A residential water heater (10) according to claim 10, further comprising:

- a third manifold (54), for accumulating said heated water from said second inlet (76) into said at least two sub-tanks (58A, 58B, 58C);

- a fourth manifold (70), for distributing said non-heated water from said at least two sub-tanks (58 A, 58B, 58C) into said second outlet (74); and

- a second water selector (54) for allowing flowing said water from said second inlet (76) into said second outlet (74) through one or more of said at least two sub-tanks (58A, 58B, 58C). thereby allowing using said solar collector (66) for heating only one of said at least two sub-tanks (58A, 58B, 58C) without mixing non-heated water of other sub-tanks.

12. A residential water heater (10) according to claim 1, further comprising:

- a controller (50), for controlling at least one of said first water selector (20) and said heating apparatuses (26A, 26B, 26C).

13. A residential water heater (10) according to claim 1, wherein said first water selector (20) and said heating apparatuses (26A, 26B, 26C) are controlled manually.

14. A residential water heater (10) according to claim 6, wherein said first water selector (20) comprises a plurality of faucets.

15. A residential water heater (10) according to claim 6, wherein said first water selector (20) comprises:

- a plurality of inlets/outlets (32A, 32B, 32C);

- one outlet/inlet (22); and

- a rotatable block (34) Comprising a gateway (40) allowing flow between said one of said inlets/outlets (32A, 32B, 32C) and said outlet/inlet (22).

16. A method for heating water, said method comprising the steps of:

- providing an insulated (30) tank (16) partitioned to a plurality of sub- tanks (58A, 58B, 58C);

- selecting one of said at least two sub-tanks (58 A, 58B, 58C) as the current tank from which heated water is to be dispensed;

- heating water of said selected one of said at least two sub-tanks (58 A, 58B, 58C); and

- dispensing water from said selected one of said at least two sub-tanks (58A, 58B, 58C), thereby obtaining higher temperature of primary water to be dispensed from said tank (16) at less power than heating an un-partitioned tank.

17. A method for heating water according to claim 16, wherein said step of heating water of one of said at least two sub-tanks (58A, 58B, 58C) comprises turning on a heating element disposed in said one of said at least two sub-tanks (58A, 58B, 58C).

18. A method for heating water according to claim 16, wherein said step of heating water of one of said at least two sub-tanks (58A, 58B, 58C) comprises flowing water contained in said one (58 A) of said at least two sub- tanks (58A, 58B, 15 58C) through a solar collector (66) in a closed loop.

19. A method for heating water according to claim 16, further comprising the step of:

- measuring temperature of each of said at least two sub-tanks (58A, 58B, 58C), thereby providing data for said selecting said one of said at least two sub- tanks (58 A, 58B, 58C) to flow said water therethrough.

20. A method for heating water according to claim 16, wherein said step of selecting said one of said at least two sub-tanks (58 A, 58B, 58C) comprises selecting the sub-tank having the highest temperature measurement.

21. A method for heating water according to claim 20, wherein said step of selecting the sub-tank having the highest temperature measurement comprises selecting another sub-tank upon exceeding a desired maximum temperature.

22. A method for heating water according to claim 16, further comprising the step of heating water of a sub-tank other than said selected one of said at least two sub-tanks (58A, 58B, 58C).