WO2011030188A2

WO2011030188A2 - Water saving system to be used in water heaters for hot water supply

Info

Publication number: WO2011030188A2
Application number: PCT/IB2009/055660
Authority: WO
Inventors: Vítor António FERREIRA DA COSTA
Original assignee: Universidade De Aveiro
Priority date: 2009-09-08
Filing date: 2009-12-10
Publication date: 2011-03-17
Also published as: PT104738B; PT104738A; WO2011030188A3

Abstract

Present invention refers to a water saving system to be used in water heaters, composed by two water selection systems (24) and (25), and by one accumulation reservoir (1), thus allowing water savings in water heaters for hot water supply. Proposed system operates automatically, as function of the pressure and temperature at some particular points of the system. The main objective of the proposed system is to guarantee that, under normal use conditions, only hot water, above a given selected temperature, leaves the water heater. If, during the initial period of functioning of the water heater there is no hot water at its outlet, the outlet water current is directed towards the accumulation reservoir. The so accumulated water under pressure is later used as cold water to feed the water heater. Present invention belongs to the water heaters industry for hot water supply, which can be used for domestic or industrial use, the water heating being made using any heat source like fuel burning, hot gases, or electric resistances.

Description

Title of Invention: WATER SAVING SYSTEM TO BE USED IN

WATER HEATERS FOR HOT WATER SUPPLY

Field of the invention

[1] Present invention refers to a water saving system to be installed in water heaters for hot water supply, allowing water savings in domestic or industrial installations, which is composed by two water selection systems and by one accumulation reservoir.

System operates in an automatic way, as function of the pressure and temperature at some particular points of the system.

[2] Present invention belongs to the water heaters industry for hot water supply, which can be used for domestic or industrial use, the water heating being made using any heat source like fuel burning, hot gases, or electric resistances.

Background of the invention

[3] Water heaters for hot water supply present the problem of do not release hot water at their outlet during the initial periods of functioning. Due to that, the water reaching the valves or points of hot water use does not meet the user temperature requirements, and it is thus potable water that is usually discharged into the sewage system.

[4] If the water heaters for hot water supply include the proposed system, with the water saving function, only hot water that meets the temperature requirements of the users leaves the water heater, the proposed system thus promoting potable water savings in domestic or industrial installations.

[5] During the initial phases of functioning of a water heater for hot water supply, when it is cold or partially cold, and filled with cold or partially cold water, and while no hot water exists at its outlet, the cold or partially cold water leaving it is directed towards the accumulation reservoir, where it remains accumulated under pressure, and thus this cold or partially cold water is not discharged into the sewage system.

[6] The so accumulated water under pressure is later used as cold water to feed the water heater, and it is thus water to be re-used to feed the system that originates its own accumulation.

[7] The time period needed for the existence of hot water at the outlet of the water

heater, when it starts its functioning, depends on the mass of the system, on the amount of water contained in it, on the mass flow rate of water crossing it, and of the heating power available, and it thus varies from one case to the other, but it is essentially a well defined characteristic of each particular water heater. The size, or capacity, of the accumulation reservoir of the proposed system is thus dependent on the amount of cold or partially cold water that was discharged into the sewage system if the proposed water saving system was not used.

[8] Due to that, an opportunity exists for water saving systems to be incorporated into water heaters for hot water supply, allowing the accumulation of the cold or partially cold water that, during some periods of time, leaves the water heater, which is usually discharged into the sewage system but that with the proposed system is accumulated under pressure and later used as cold water to feed the same water heater.

[9] Additionally, opportunities exist also for water saving systems to be used associated with the mixing valves or systems using hot water, in the case when no hot water is guaranteed at the inlet of such systems. However, the nature of these systems is different from the one of the here proposed system, its main objective being the guarantee that at the water heater outlet only hot water exists, which temperature requirements meet the requirements of the users at the valves and some other hot water utilization points.

[10] The proposed system operates automatically, as function of the pressure and temperature at some particular points of the system, and its operation does not require any human action. During the initial phase of functioning of the water heater, when the cold or partially cold water does not meet the temperature requirements of the users and is being directed towards the accumulation reservoir, no water exists leaving the water heater as a whole, but only an internal water circulation exists from the inlet towards the accumulation reservoir.

[11] The here proposed system can be incorporated into new water heaters for hot water supply, but it can also be incorporated without major difficulties into existing water heaters for hot water supply.

Previous related works

[12] Up to now some systems have been proposed with the same main objective of water savings during the initial periods of functioning of the water heaters, when no hot water is being released by such systems. Some of them are referred below by chronological order:

[13] Some systems include an electrically driven water recirculating pump, which directs the cold or partially cold water from the outlet of the water heater to its inlet. Such systems are very good in what concerns its main objective of water saving, by they require invariably an electrically driven water recirculating pump, and the electrical energy to drive it.

[14] US4737615 refers to an energy saving system for an electrical water heater, the proposed system consisting essentially of alternatives for command and control of the electrical heater elements.

[15] Another possibility is the use of electrically operated auxiliary heating elements, which are invoked during the initial functioning period of the water heater, when no hot water is available at the outlet of the water heater, in order to supply the additional heating needed to have the required hot water that was not sufficiently heated by the base water heater.

[16] Systems proposed in PT104037, PCT/IB2009/005378, and PT104138 have the same main objective as the present invention: the water savings during the initial periods when no hot water is available. They are, however, systems to be used in mixing valves using the hot water coming from the water heaters used for hot water supply, the here proposed system being to be incorporated in the water heaters for hot water supply, in order to guarantee that the water leaving the water heater meets the temperature requirements of the users .

[17] No purely mechanical systems, or others that do not require any additional energy source, like the present invention, are know, to promote the water savings in water heaters for hot water supply.

Figures description

[18] Figure 1 and Figure la - schematic representation of the proposed system, the

numbers referring to:

1 - Accumulation reservoir

2 - Check valve

3 - Heating zone of the water heater for hot water supply

4 - Piston

5 - Spring

6 - Perforated disk, which is crossed by element (7)

7 - Mechanical element that abuts rod (9), spring (10) and piston (4)

8 - Dilatable bulb (receiving the signal from the dilatable bulb (12))

9 - Rod of the dilatable bulb (8)

10 - Spring

11 - Chanel for information transfer between bulb (12) and bulb (8)

12 - Dilatable bulb

13 - Dilatable bulb

14 - Rod of dilatable bulb (13)

15 - Perforated piston

16 - Rod linking perforated piston (15) to piston (17)

17 - Piston

18 - Spring

19 - Piston

20 - Spring

21 - Check valve

22 - Inlet of cold water into the water heater, coming from the main cold water dis- tribution system

23 - Outlet of the water heater for hot water supply

24 - Water selection system

25 - Water selection system

[19] The accumulation system schematically represented in Figs, la and lb can be placed where more convenient, but it must be placed as close as possible of the heating zone (3) of the water heater for hot water supply.

[20] The proposed system can be incorporated without major problems into existing water heaters, the main changes being that the cold water inlet into the water heater must be replaced by the water selection system (24), and the outlet of the water heater must be replaced by the water selection system (25).

General Description of the Invention

[21] The here proposed system, which is to be installed into water heaters for hot water supply, is composed by the two water selection systems (24) and (25), and by one accumulation reservoir (1), where water is to be accumulated under pressure.

[22] Water selection system (25) is composed by the dilatable bulb (13), the rod (14) which moves to the right when dilatable bulb (13) increases its length, by the perforated piston (15), by piston (17), by rod (16) linking pistons (15) and (17), and by spring (18). This water selection system (25) comprises also the pressure sensor device at the outlet (23) and it is composed by piston (19), the spring (20) and the check valve (21). The dilatable bulb (12), even if installed in the water selection system (25), makes use of its dilatable action over dilatable bulb (8) of the water selection system (24), the signal of bulb (12) being transmitted to bulb (8) through the transfer channel (11), in the form of an increase or decrease of the volume of fluid contained into the dilatable bulb, this fluid filling also the transfer channel (11), which results in an increase or decrease of volume, respectively, on the dilatable bulb (8).

[23] Water selection system (25) evaluates the temperature of the water leaving the

heating zone (3) of the water heater, this evaluation being made by dilatable bulb (13), as well as pressure in the accumulation reservoir (1), and directs the water to the outlet (23) of the water heater if this outlet temperature is above the required value, as the set formed by pistons (15) and (17) and rod (16) moves to the right, or if the pressure in the accumulation reservoir is such that it indicates that the accumulation reservoir (1) is filled with water, or, on the contrary, directs the water towards the accumulation reservoir (1).

[24] Water selection system (25) includes a device that senses the pressure at the outlet (23), and if pressure there is high enough this means that outlet (23) is closed, no hot water demands exist by the devices using hot water, and in that case no water is sent to the accumulation reservoir (1). [25] Water selection system (24) is composed by the dilatable bulb (8), by piston (4), by spring (5), by perforated disk (6), by rod (9), by spring (10) and by the linking mechanical element (7).

[26] Water selection system (24), through dilatable bulbs (12) and (8), which are linked through the signal transfer channel (11), evaluates the temperature of the water leaving the heating zone (3) of the water heater, as well as the pressure of the water in the accumulation reservoir (1), and opens the inlet of the cold water coming from the main cold water distribution system (22) if the water at the outlet of the heating zone (3) is not sufficiently hot or if the pressure in the accumulation reservoir (1) indicates that it is not filled with water. On the contrary, if the water leaving the heating zone (3) is sufficiently hot and if the pressure in the accumulation reservoir (1) indicates that it is charged with water, the water selection system (24) acts such that the inlet (22) of the cold water coming from the main cold water distribution system is closed and allows flow of the water contained into the accumulation reservoir (1) towards the inlet of the heating zone (3) of the water heater.

[27] The different modes of operation of the water selection system (25) can be described as:

1. When the temperature of the water at the outlet of the heating zone (3) is not high enough, accumulation reservoir (1) is not fully charged with water, and the outlet (23) is open such that the pressure at outlet (23) acting over piston (19) is not high enough such that passage to the accumulation reservoir (1) is not closed, the water leaving the heating zone (3) is directed towards the accumulation reservoir (1).

2. When the temperature of the water at the outlet of the heating zone (3) is not sufficiently high, the accumulation reservoir (1) is not completely charged with water, and outlet (23) is closed, what means that no hot water demands exist by the users, in a way such that the pressure of the water searching the outlet (23) acting over piston (19) moves it to close the passage towards the accumulation reservoir (1), there is no hot water exit through outlet (23) as well as there is no water passage towards the accumulation reservoir (1), and thus there is no any water current coming from the heating zone (3).

3. When the temperature of the water at the outlet of the heating zone (3) is not sufficiently high, the accumulation reservoir (1) is completely charged with water, and the outlet (23) is open such that the pressure at outlet (23) acting over piston (19) is such that passage towards accumulation reservoir (1) is not closed, the cold or partially cold water leaving the heating zone (3) is not directed towards the accumulation reservoir (1) but towards the outlet (23) as the pressure at the accumulation reservoir (1) acts over piston (17) and it is forced to move to the right, the same happening with the perforated piston (15), thus leaving free the passage of water from the heating zone (3) to the outlet (23). Under these conditions, temperature of the water at the outlet (23) can be lower than that required by the users, but in this case the accumulation reservoir (1) is completely charged with water and no more water accumulation is possible.

4. When the temperature of the water at the outlet of the heating zone (3) is not sufficiently high, the accumulation reservoir (1) is completely charged with water, and outlet (23) is closed, thus meaning that no water demands exist by the users, such that the pressure at outlet (23) acting over piston (19) leads it to close the passage towards accumulation reservoir (1), no water exit through outlet (23) exists as well as water passage towards accumulation reservoir (1), and no any water current exists leaving the heating zone (3).

5. When the temperature of water at the outlet of the heating zone (3) is sufficiently high, dilatable bulb (13) displaces rod (14) to the right, and this rod forces the perforated piston (15) to the right in order to open the passage of the water from the heating zone (3) towards the outlet (23). If the outlet (23) is open, the hot water leaving the heating zone (3) is directed towards outlet (23) and then from there to the hot water users.

6. When the temperature of the water at outlet of the heating zone (3) is sufficiently high, dilatable bulb (13) displaces rod (14) to the right, and this rod (14) pushes the perforated piston (15) to the right, thus opening the passage of water from the heating zone (3) towards outlet (23). If the outlet (23) is closed, no water can flow from the heating zone (3) to the outlet (23), and in this case no water is being directed to the accumulation reservoir as the pressure at the outlet (23) is such that the piston (19) promotes the closure of any eventual hot water passage from the heating zone (3) to the accumulation reservoir (1).

[28] The different modes of functioning of the water selection system (24) can be

described as:

1. When the temperature of the water at the outlet of the heating zone (3) is not sufficiently high, bulb (12) and consequently bulb (8) do not increase in length, spring (10) forces element (7) to the left, which forces piston (4) to the left no matter water the pressure in the accumulation reservoir (1) is, thus promoting the inlet of cold water (22) coming from the main cold water distribution system in to the system.

2. When the temperature of the water at the outlet of the heating zone (3) is sufficiently high, bulb (12) and consequently bulb (8) increase in length, against action of spring (10), and element (7) is forced to displace to the right. Under these conditions, if the accumulation reservoir (1) is not completely charged with water spring (5) forces piston (4) to the left, thus promoting the opening of the inlet of the cold water (22) coming from the main cold water distribution system into the system.

3. When the temperature of the water at the outlet of the heating zone (3) is suf- ficiently high, bulb (12) and consequently bulb (8) increase in length, against action of spring (10), and the element (7) is forced to move to the right. Under these conditions, if the accumulation reservoir (1) is completely charged with water the pressure in the accumulation reservoir forces piston (4) to move to the right, against action of spring (5), thus promoting the closure of the inlet of the cold water (22) coming from the main cold water distribution system into the system. Under these conditions, as the accumulation reservoir (1) is charged with water, water contained in it is directed towards the inlet of the heating zone (3), this water current passing through the check valve (2). This is the phase corresponding to the use of the water accumulated under pressure into the accumulation reservoir (1).

[29] No conditions exist corresponding to exit of water from the accumulation reservoir (1) towards the inlet of the heating zone (3), and the water leaving the heating zone (3) being directed towards the accumulation reservoir (1), as due to the existing losses and pressure drops water does not return to a point from where it comes, unless some external energy is added to it, what is not the case.

[30] As described, system operates automatically, without any human action, in function of temperature and pressure evaluated at some particular points of the system, in order to obtain the pursued water saving function.

[31] As described, proposed system does not require any additional energy source,

electrical, mechanical or other, and it functions on the basis of temperature and pressure of water at some particular points of the system

[32] Capacity of the accumulation reservoir (1) of the proposed system depends on the volume of water that was lost if the proposed system was not used, potable water that was thus directly discharged into the sewage system, as it does not meet the temperature requirements of the hot water users.

Detailed Description of the Invention

[33] Using Figs, la and lb as reference, it is now described the proposed invention, where the relevant elements composing it are represented.

[34] The temperature sensor elements, evaluating the water temperature at the outlet (3) of the heating zone, are the dilatable bulbs (12) and (13). Dilatable bulb (13) acts directly over rod (14), but dilatable bulb (12) communicates its action to dilatable bulb (8) through the signal transfer channel (11), dilatable bulb (8) acting directly over rod (9).

[35] Water selection system (25) functions in the following way:

[36] When the temperature of the water at the outlet of the heating zone (3) is not sufficiently high, accumulation reservoir (1) is not completely charged with water, and outlet (23) is open, such that the pressure at outlet (23) acting over piston (19) is not high enough to move it to close the water passage towards the accumulation reservoir (1), the set formed by pistons (15) and (17) and by rod (16) is displaced to the left by action of the spring (18), and the water leaving the heating zone (3) is directed towards the accumulation reservoir (1). This is the phase corresponding to the accumulation of the water that does not meet the users' requirements, and that was discharged into the sewage system if a system with the water saving function was not used.

[37] When the temperature of the water at the outlet of the heating zone (3) is not sufficiently high, accumulation reservoir (1) is not completely charged with water, and the outlet (23) is closed, thus meaning that no hot water demands exist from the users, such that the pressure at the outlet (23) acts over piston (19) and forces it to close the water passage to the accumulation reservoir (1), no water exit exists at the outlet (23) as well as no water passage exists towards the accumulation reservoir (1), and no any water current is leaving the heating zone (3).

[38] When the temperature of the water at the outlet of the heating zone (3) is not sufficiently high, the accumulation reservoir (1) is completely charged with water, and outlet (23) is open, such that pressure at the outlet (23) acting over piston (19) is not high enough to force it to close the water passage towards the accumulation reservoir (1), the cold or partially cold water leaving the heating zone (3) is not directed to the accumulation reservoir (1) but to the outlet (23) as the pressure in the accumulation reservoir (1) acts over piston (17) and forces it to move to the right, the same happening with the perforated piston (15), thus remaining free the passage of water from the heating zone (3) to the outlet (23). Under these conditions, water temperature at the outlet (23) can be lower than that required by the hot water users, but in this situation the accumulation reservoir (1) is completely charged with water and it cannot receive more water inside it.

[39] When the temperature of the water at the outlet of the heating zone (3) is not sufficiently high, the accumulation reservoir (1) is completely charged with water, and outlet (23) is closed, thus meaning that no hot water demands exist from the users, pressure at the outlet (23) acts over piston (19) and it closes the water passage towards the accumulation reservoir (1), there is no water exit through outlet (23) as well as there is no water passage towards accumulation reservoir (1), and thus there is no any water current leaving the heating zone (3).

[40] When the temperature of the water at the outlet of the heating zone (3) is sufficiently high, dilatable bulb (13) displaces rod (14) to the right, and thus pushes the perforated piston (15) to the right in order to open the passage of water from the heating zone (3) towards the outlet (23) through the free space on the left of the perforated piston (15). If the outlet (23) is open the water coming from the heating zone (3) flows towards outlet (23) and then from there to the hot water users. This situation corresponds to the normal use of the water heater for hot water supply incorporating the proposed system with the water saving function. [41] When the temperature of the water at the outlet of the heating zone (3) is sufficiently high, dilatable bulb (13) displaces rod (14) to the right, and it pushes perforated piston (15) to the right in such a way that it opens the passage of water from the heating zone (3) towards the outlet (23). If the outlet (23) is closed, there is no water passage from the heating zone (3) towards the outlet (23), and in this case no water is send to the accumulation reservoir (1) as the pressure at the outlet (23) is high enough to move piston (19) to the left which promotes the closure on any eventual passage of water from the heating zone (3) towards the accumulation reservoir (1).

[42] Sub-system composed by piston (19) and by spring (20) acts such that it closes the passage of water from the outlet of the heating zone (3) to the accumulation reservoir (1) if the outlet (23) is closed, and allows the water passage from the outlet of the heating zone (3) towards the accumulation reservoir (1) if the outlet (23) is open.

[43] The check valve (21) guarantees that the water contained into the accumulation

reservoir (1) is never directly discharged to the outlet (3) of the heating zone, but always discharged over the water selection system (24).

[44] The water selection system (24) functions in the following way:

[45] When the temperature of the water at the outlet of the heating zone (3) is not sufficiently high, bulb (12) and consequently also bulb (8) do not increase in length, spring (10) forces element (7) to the left, which forces piston (4) to the left no matter what the pressure inside the accumulation reservoir (1) is, thus promoting the inlet of cold water (22) coming from the main cold water distribution system into the system. No conditions exist corresponding to the exit of water from the accumulation reservoir (1) towards the inlet of the heating zone (3), and the water leaving the heating zone (3) being directed towards the accumulation reservoir (1), as due to the existing losses and pressure drops water does not return to a point from where it comes, unless some external energy is added to it, what is not the case.

[46] When the temperature of the water at the outlet of the heating zone (3) is sufficiently high, bulb (13) and also consequently bulb (8) increase in length, against action of spring (10), and element (7) is forced to move to the right. Under these conditions, if the accumulation reservoir (1) is not completely charged with water, spring (5) forces the piston (4) to the left, thus promoting the opening of the cold water inlet (22) coming from the main cold water distribution system into the system. Under these conditions no cold water (22) is directed towards the accumulation reservoir (1) as it is completely charged with water, and no more water can be contained inside it.

[47] When the temperature of the water at the outlet of the heating zone (3) is sufficiently high, bulb (13) and also consequently bulb (8) increase in length, against the action of spring (10), and element (7) is forced to move to the right. Under these conditions, if the accumulation reservoir is completely charged with water pressure inside it forces piston (4) to move to the right, against action of spring (5), thus promoting the closure of cold water inlet (22) coming from the main cold water distribution system into the system. Under these conditions, as accumulation reservoir (1) is charged with water, the water contained in it is not directed towards the inlet of the heating zone (3), this water passing through check valve (2). Under these functioning conditions water contained under pressure into the accumulation reservoir (1) is being used to feed the water heater, and this water was sent before to the accumulation reservoir (1) when the temperature of the water at the outlet of the heating zone (3) was not that required by the hot water users, and it is thus in this phase that the water saving function is accomplished by the proposed system.

[48] Check valve (2) guarantees that the cold water (22) coming from the main cold water distribution system cannot flow directly into the accumulation reservoir (1), the water to be sent to the accumulation reservoir being only the water leaving the heating zone (3) that does not meet the temperature requirements of the hot water users.

[49] System operates without any human action, and it functions automatically in function of the temperatures and pressures at some particular points of the system. The so evaluated temperatures result in actions over the dilatable bulbs (12), (8) and (13). By their own turn, the so evaluated pressures act over the pistons (4), (17) and (19).

[50] The proposed system do not need any additional energy source, electrical, mechanical or other, the system functioning only on the basis of the temperatures and pressures taken at some particular points of the system.

[51] Capacity of the accumulation reservoir (1) of the proposed system is obtained from the volume of cold or partially cold water that, if the system with the water saving function was not used, was discharged by the water heater at a temperature below the temperature requirements of the hot water users, thus being potable water usually discharged into the sewage system.

[52] The proposed system can be implemented without problems into new or existing water heaters, where the water heating can be made by fuel burning, use of hot gases, or using electrical resistances. If the system is to be used in existing water heaters, it is only needed to substitute the cold water inlet on the water heater by the water selection system (24), and to substitute the outlet of the water heater by the water selection system (25).

Claims

[Claim 1] Water saving system to be used in water heaters and boilers for hot water supply, comprising one accumulation reservoir (1), where water is accumulated under pressure; by a first water selection system (24) which evaluates the temperature of the water leaving the heating zone (3) of the water heater or boiler, through dilatable bulbs (12) and (8), linked through the signal transfer channel (11), as well as the pressure within the accumulation reservoir (1), and opens the cold water inlet (22) coming from the main cold water distribution system if the temperature of the water leaving the heating zone (3) is not sufficiently hot or if the pressure in the accumulation reservoir (1) indicates that it is not completely charged with water, and when the water at the exit of the heating zone (3) is sufficiently hot and if the pressure in the accumulation reservoir (1) indicates that it is completely charged with water, the water selection system (24) acts such that it closes the inlet (22) of the cold water coming from the main cold water distribution system into the system and allows flow of the water contained in the accumulation reservoir (1) towards the inlet of the heating zone (3) of the water heater or boiler;

a second water selection system (25) which evaluates the temperature of the water leaving the heating zone (3) of the water heater or boiler through the dilatable bulb (13), as well as the pressure in the accumulation reservoir (1), and directs the water towards the outlet (23) of the water heater or boiler if the exit temperature is equal or higher than the required value, or directs the water to the accumulation reservoir (1) if the pressure within the accumulation reservoir (1) indicates that it is not completely charged with water.

[Claim 2] System according to claim 1, wherein the water selection system

(24) is composed by the dilatable bulb (8), by piston (4), by spring (5), by perforated disk (6), by rod (9), by spring (10), by the element of mechanical link (7), and by the check valve (2), wherein the dilatable bulb (8) installed in the water selection system (24) receives the signal coming from the dilatable bulb (12), which is installed in the water selection system (25).

[Claim 3] System according to claim 1, wherein the water selection system

(25) is composed by the dilatable bulb (13), by rod (14) which moves to the right when dilatable bulb (13) swells, by perforated piston (15), by piston (17), by rod (16) linking pistons (15) and (17), and by spring (18), wherein the water selection system (25) further includes the pressure sensor at the outlet (23) composed by piston (19), by spring (20) and by the check valve (21), and by the dilatable bulb (12), installed into the water selection system (25) which will act onto the dilatable bulb (8) of the water selection system (24), the signal of bulb (12) being transmitted through the signal transfer channel (11) such that its action is exerted over the dilatable bulb (8).

System according to the previous claims wherein the dilatable bulb (12) transmits a signal, through transfer channel (11), in the form of an increase or decrease of volume of the fluid contained in the dilatable bulb, the same fluid filling also the signal transfer channel (11), thus resulting in an increase or decrease in the volume, respectively, on the dilatable bulb (8).

System according to the previous claims, wherein it directs the cold or partially cold water leaving the heating zone (3) to the accumulation reservoir (1) provided that it is not completely charged with water and has additional capacity to accumulate such cold or partially cold water.

System according to the previous claims, wherein it operates automatically, depending on the temperatures and pressures evaluated at some particular points of the system, and does not require any additional operation of the hot water users.

System according to the previous claims, wherein it is implemented in new water heaters or boilers for hot water supply, as well as in existing water heaters for hot water supply.

System according to the previous claims wherein it does not need any additional energy source, either electrical, mechanical or another, functioning only based on the temperature and pressure values automatically taken at some particular points of the system under operation.

System according to claims 1 to 4, wherein the water selection system (25), when the temperature of the water leaving the heating zone (3) is not sufficiently high, the accumulation reservoir (1) is not completely charged with water, and the outlet (23) is open such that the pressure at the outlet (23) acting over piston (19) does not close the water passage towards the accu- mulation reservoir (1), thus allowing that the water leaving the heating zone (3) is directed towards the accumulation reservoir (1).

System according to claims 1 to 4, wherein the water selection system (25), when the temperature of the water leaving the heating zone (3) is not sufficiently high, accumulation reservoir (1) is not completely charged with water, and outlet (23) is closed, thus meaning that there are no hot water demands by the hot water users, such that the pressure at the outlet (23) acting over piston (19) makes it close the passage to the accumulation reservoir (1), such that there is no water exiting through outlet (23) as well as there is no water passage to the accumulation reservoir (1), thus avoiding that any water current is crossing the heating zone (3).

System according to claims 1 to 4, wherein the water selection system (25), when the temperature of the water leaving the heating zone (3) is not sufficiently high, the accumulation reservoir (1) is completely charged with water, and the outlet (23) is open such that the pressure at the outlet (23) acting over piston (19) is such that it does not close water passage to the accumulation reservoir (1), avoids the cold or partially cold water coming from the heating zone (3) to be directed to the accumulation reservoir (1) but it flows to the outlet (23), wherein the pressure in the accumulation reservoir acting over piston (17) and forcing it to move to the right, the same occurring with the perforated piston (15), thus allowing the water passage from the outlet of the heating zone (3) towards the outlet (23), the temperature of the water at the outlet (23) being in such conditions able to be lower than that required by the hot water users, but in this situation the accumulation reservoir (1) is completely charged with water and no more water can be sent to it.

System according to claims 1 to 4, wherein the water selection system (25), when the temperature of the water leaving the outlet of the heating zone (3) is not sufficiently high, the accumulation reservoir (1) is completely charged with water, and the outlet (23) is closed, thus meaning that no hot water demands exist from hot water users, the pressure at the outlet (23) acting over piston (19) such that it closes the water passage to the accumulation reservoir (1), and there is no water leaving through outlet (23) as well as there is no water passage to the accumulation reservoir (1), and no water current coming from the heating zone (3).

[Claim 13] System according to claims 1 to 4, wherein the water selection system (25), when the temperature of the water at the outlet of the heating zone (3) is sufficiently high, the dilatable bulb (13) displaces rod (14) to the right, and this rod pushes the perforated piston (15) to the right, thus leaving the water passage free from the heating zone (3) towards the outlet (23) if outlet (23) is open, and allows that the water leaving the heating zone (3) flows to the outlet (23) and therefrom to the hot water users.

[Claim 14] System according to claims 1 to 4, wherein the water selection system (25), when the temperature of the water leaving the heating zone (3) is sufficiently high, dilatable bulb (13) displaces rod (14) to the right, and this one pushes the perforated piston (15) to the right such that it leaves the passage of water free to flow from heating zone (3) towards the outlet (23), and if the outlet (23) is closed, there is no water passage from heating zone (3) to the outlet (23), and in this case there is no water flowing towards the accumulation reservoir as the pressure at outlet (23) is such that piston (19) causes the closing of an eventual hot water passage from the heating zone (3) to the accumulation reservoir (1).

[Claim 15] System according to claims 1 to 4, wherein the water selection system (24) promotes the inlet of cold water (22) coming from the main cold water distribution system into the system, when the temperature of the water leaving the heating zone (3) is not sufficiently high, bulb (12) and, consequently, bulb (8) do not swell, spring (10) forces element (7) to the left, which forces piston (4) to the left no matter what the pressure into the accumulation reservoir (1) is.

[Claim 16] System according to claims 1 to 4, wherein the water selection system (24) promotes opening of the inlet of the cold water (22) coming from the main cold water distribution system into the system, when the temperature of the water leaving heating zone (3) is sufficiently high, bulb (12) and, consequently, bulb (8) swell, against action of spring (10), and element (7) is forced to move to the right, and under such conditions, if the accumulation reservoir (1) is not fully charged with water, spring (5) forces piston (4) to the left, thus allowing inlet of cold water (22) coming from the main cod water distribution system into the system.

[Claim 17] System according to claims 1 to 4, wherein the water selection system (24), when the temperature of the water leaving the heating zone (3) is sufficiently high, bulb (12) and, consequently, bulb (8) swell, against action of spring (10), and element (7) is forced to move to the right, and under such conditions, if the accumulation reservoir is completely charged with water, the pressure in the accumulation reservoir forces piston (4) to move to the right, against action of spring (5), thus closing the inlet of the cold water (22) coming from the main cold water distribution system into the system, and the water contained into the accumulation reservoir (1) is directed towards the inlet of the heating zone (3), this water flow crossing the check valve (2), thus promoting the use of the water accumulated under pressure into the accumulation reservoir (1).