Patent Publication Number: US-2012031498-A1

Title: Water supply system and method

Description:
The present invention is related to, and claims priority from, patent application No. GB0724477.5 filed by the present applicant in Great Britain on 17 Dec. 2007. 
     FIELD OF THE INVENTION 
     The present invention relates to a system and method for supplying hot and cold water for domestic, commercial or industrial use, and more specifically for such a system including means for saving on the use of water and energy. 
     BACKGROUND OF THE INVENTION 
     In a domestic, commercial or industrial environment, there are hot and cold water pipes supplying water to the various users or faucets there. 
     A problem in such prior art systems is the waste of water while waiting for the hot water to arrive. This water is wasting away. The waste is estimated at about 10 liters (about 2.2 British gallons). If water is temporarily turned off, it may take time and some adjustments to later regain the water supply at the desired flow rate and temperature. To avoid bothering with these burdens, people taking a shower often leave the water running for the whole duration, thus wasting water unnecessarily. 
     Despite such precautions, variations in water temperature do occur, due to changes in water pressure and use of water by other users in the house, depletion of hot water in the water tank, etc. 
     Another problem in prior art water supply systems relates to water freezing in the pipes in cold weather. This may cause a stoppage in the water supply, as the ice thus formed prevents water from flowing in the pipe. Moreover, the extreme forces related to water freezing can damage the pipe. 
     Popper et al., U.S. Pat. No. 6,895,985—Smart device and system for improved domestic use and saving of water, presents a system for providing a user with water at a desired temperature, using means to allow circulation of the hot water into the cold water pipe. Thus, while waiting for the hot water to arrive at the faucet, the water from the hot water pipe is circulated onto the cold water pipe. 
     Still, various problems remain, which are solved with the present disclosure, which also presents improvements in Popper. 
     SUMMARY OF THE INVENTION 
     The present invention is described generally with reference to the following innovative aspects: 
     1. A system for supplying hot water to an apartment/house, to all or part of the users, while recycling water from the hot water pipe into the cold water pipe. The system may also be used in commercial or industrial establishments.
 
2. A method for supplying hot water, while managing micro valves in the faucet, water circulation and/or heating in the water tank.
 
Automatic water circulation may also be used to prevent water from freezing in the pipes.
 
3. A new micro valve including three valves activated electronically, and easily installable in standard diameter faucets
 
4. Human-machine interface, using effective means for allowing the user to control the water temperature and flow rate, as well as various additional parameters.
 
5. A device for mixing fluids from a plurality of sources. For example, people may desire to use either potable water or sea water, then to mix hot and cold water. Various materials may also be mixed.
 
6. Protecting users from burns due to exposure to hot water—New safety standards demand to limit the temperature of the hot water supply, to protect users from accidental burns if exposed to hot water only, for example Israeli standard No. 5463 and Australian standard No. 4032.2. The temperature of hot water supply should be limited to a predetermined value, for example 45 degrees Celsius.
 
7. Operating panel with advanced display means, including for example VGA or video or television display for viewing TV or movies or other info while in the shower.
 
A multi-functional display may be used both to control the water supply and subsequently to present other information.
 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  illustrates a prior art system for supplying hot and cold water 
         FIG. 2  illustrates a system for saving water by circulating hot water into the cold water pipe 
         FIG. 3  illustrates a multi-faucet distributed system for saving water by circulating hot water into the cold water pipe 
         FIG. 4  illustrates a multi-faucet centralized system for saving water by circulating hot water into the cold water pipe 
         FIG. 5  illustrates the propagation of hot water front toward the faucet in the circulation mode of operation 
         FIG. 6  details a method of operation of the system 
         FIG. 7  illustrates the water temperature at the faucet during the circulation stage 
         FIG. 8  details the water circulation stopping process 
         FIG. 9  illustrates one embodiment of a faucet 
         FIG. 10  illustrates two cross-sectional longitudinal views of another embodiment of the new faucet 
         FIG. 11  details a new valve structure 
         FIG. 12  illustrates a functional cross-sectional view of a preferred embodiment of the new micro valve, detailing the cold and hot water inlets 
         FIG. 13  illustrates a functional cross-sectional view of a device for mixing fluids from a plurality of sources 
         FIG. 14  illustrates two cross-sectional longitudinal views of yet another embodiment of the new valve 
         FIG. 15  illustrates a top view of the faucet 
         FIG. 16  illustrates one embodiment of a human-machine interface 
         FIG. 17  illustrates another embodiment of a control panel 
         FIG. 18  illustrates yet another embodiment of the control panel 
         FIG. 19  illustrates yet another embodiment of the control panel 
         FIG. 20  illustrates a system for delivering hot water at a safe temperature. 
         FIG. 21  details another embodiment of a new valve structure 
     
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     The description generally details the seven innovative aspects of the invention, although the various aspects of the invention are interrelated in one innovative concept. 
     1. System for Supplying Hot and Cold Water to Users in a Domestic, Commercial or Industrial Establishment 
       FIG. 1  presents a functional description of a prior art system for supplying hot and cold water. 
     Water from a water supply inlet to the house  11  is supplied as cold water, through a cold water supply pipe  12  and its ramifications, to all the users in the house. 
     There is also cold water supply through pipe  13  for the hot water subsystem, using the water tank  21  to heat the water. The hot water is supplied to users in the house through hot water supply pipe  22  and its ramifications. 
     The present invention may be used where there is no water tank  21 , for example using an in-line heater, such as manufactured by Atmor Ltd. 
     Various water heating means may be used, for example using solar energy, gas heating, etc. 
     Each user may have a hot/cold water faucet  3 . 
     At the faucet  3 , there is a cold water inlet  31  with a cold water valve  32  controlling the supply of cold water, and a hot water inlet  33  with a hot water valve  34 . Water is supplied to users through a water outlet  35 . Usually, the valves  32  and  34  are mechanically controlled by the user. 
       FIG. 2  illustrates a system for saving water by circulating water from the hot water pipe into the cold water pipe. 
     In this embodiment, the valves  32 ,  34  and  36  are electrically controlled. The new faucet has also an outlet valve  36 . When valve  36  is closed and both valves  32 ,  34  are open, then circulation is possible, wherein water from the hot water pipe can flow into the cold water pipe. 
     A circulating pump  41  pushes water along the closed circuit comprising the water tank  21 , hot water supply pipe  22 , valves  34  and  32 , cold water supply pipe  12 , pump  41  and back to the tank  21 . See direction of circulation water flow  44 . 
     A unidirectional valve  115  may be installed at the mains supply entrance to the house. The valve allows water to flow into the house water system, but prevents water from flowing back out of the house. If such a valve is installed, suitable means for releasing excess water pressure should be provided (otherwise expanding water may exert a very large pressure, which may cause damage to the installation). 
     A temperature sensor  452  measures the water temperature in the faucet, in case only one temperature sensor is used. Preferably sensor  452  is located in the mixing chamber in the faucet, to measure the temperature of the output water. 
     If one temperature sensor is used in the system—this is the output sensor  452  ( FIG. 9 ), at the output of the faucet or in the mixing chamber. If two sensors are used, then the second sensor is that at the hot water inlet, sensor  45 ; If three sensors are used, then the third sensor is the temperature sensor  451  at the cold water inlet. 
     Using more than one sensor allows the controller to measure the temperature of hot and cold water supplied to the faucet, in addition to the temperature of the output (supplied) water. This info may be advantageously used by the control algorithm. 
     For controlling the temperature of the delivered water, only one sensor in the mixing chamber is enough. This is the preferred embodiment where a cost effective solution is desired. 
     In a preferred embodiment, the software calculates a temperature gradient vs. time, also using the rate of flow, to better control the supply of water, to achieve a regulated supply of controlled temperature and flow rate. 
     The faucet control unit  42  controls the operation of the valves  32 ,  34 ,  36  and the circulation pump  41 . 
     Optionally, it also controls the hot water tank  21 , to heat the water when necessary. 
     The circulating pump  41  is preferably mounted in the cold water pipe  13 , so it will not have to endure high operating temperatures as may be expected in the hot water pipe  22 . 
     In a preferred embodiment, where only one temperature sensor is used, then it is the sensor  452  in the mixing chamber, see  FIG. 10 . 
     In another preferred embodiment, the only temperature sensor being used is the sensor  452  at the output  35  of the faucet (at the water supply to user), see  FIG. 9 . 
       FIG. 3  illustrates a multi-faucet distributed system for saving water by circulating hot water into the cold water pipe. 
     There are faucet control units  42 , each controls the operation of valves  32 ,  34 ,  36  for one faucet  3 . 
     The operation of the faucet is according to input commands from user  425 . The unit further includes display means  426  for presenting information to the user regarding the water temperature and other parameters. Other indicator means may be used in lieu of or in addition to the display means  426 , for example audio indicator means. 
     In this distributed system, a request to activate the circulation pump  41  is transferred to another unit  42  through a communication channel  48 , the process is repeated until the request reaches one of the units  42  which actually controls the pump  41  and optionally the heating in the tank  21 , responsive to hot water requests from all the units  42 . 
     Preferably, each controller in a faucet has the capability to communicate with other such units and to control the pump  41  and the heating unit in the tank  21 . 
     The controlled in each faucet may include bi-directional communication links with other faucets, to transfer commands and status info between the units. The controller may use existing integrated circuit controllers which connect to each other automatically, recognize the topology of a network and transfer information between the nodes of the network. 
     The communication channel  48  may be implemented using radio frequency (RF) communications, wired links, ultrasound, infrared and/or other communication means. 
     The water temperature in the tank  21  may be measured using a temperature sensor  215  (or several sensors) mounted there. The result may be transferred to a unit  42 , and from it—to the rest of the units  42 . 
     The info regarding the tank water temperature may be used in the control method/algorithm to better control the circulation and the supply of hot water to the users. 
     Optional: the water temperature may be displayed on the faucet display. 
     For example: When the temperature of hot water is high, a lower circulation speed may be used, so the faucet will not be suddenly awash in very hot water. When the hot water temperature drops below a threshold, heating may be activated. The threshold may depend on expected hot water use: if a heavy usage is expected, the water may be kept at a higher temperature. 
     There may be variations in water temperature in the tank; using readings from several sensors, a better estimate of the total quantity of hot water is achieved. For example, the average of the various readings may be computed, or a weighed average, to assign the correct importance to each sensor. 
     It is possible to install a plurality of temperature sensors in the tank, for example at the top, middle and bottom of the tank. Other means may be used to measure the temperature of water in the tank, for example water circulation in the tank. 
     A plurality of such sensors may better evaluate the remaining hot water in the tank, to warn of an imminent shortage of hot water. 
     In another embodiment, readings from only one temperature sensor vs time may be used, with a suitable method/algorithm, to evaluate the remaining hot water in the tank and to warn of an imminent shortage of hot water. 
     Optionally, the units  42  also control the hot water tank  21 , to heat the water when necessary. 
       FIG. 4  illustrates a multi-faucet centralized system for saving water by circulating hot water into the cold water pipe. 
     The faucet control units  42 , each controls the operation of valves  32 ,  34 ,  36  for one faucet  3 . 
     There is a channel for input commands from user  425 , and display means  426 . 
     In this embodiment, there are three temperature sensors  45 ,  451  and  452  (see  FIG. 9 ) attached to the hot water inlet  33 , cold water inlet  31  and water outlet  35 , respectively. 
     It is important for the sensor  452  to have a fast response and measure the temperature in the water. 
     A request to activate the circulation pump  41 , from the unit  42 , is transferred to a central computer  49 . 
     Other units  42  can also transfer their requests to the computer  49 . 
     The computer  49  controls the pump  41  and optionally the heating in the tank  21 , responsive to hot water requests from all the units  42 . 
     The water temperature in the tank  21  may be measured using a temperature sensor  215  (or a plurality of sensors) and an optional prediction algorithm. The result is transferred to the computer  49  for better control of the system. 
     The prediction algorithm/method may use temperature readings as a function of time, and information about the rate of flow of water, to estimate the temperature of water in the tank and/or the amount of available hot water. 
     Optionally, the computer  49  also controls the hot water tank  21 , to heat the water when necessary. 
     2. Method for Supplying Hot Water, while Managing Micro Valves and/or Water Circulation 
       FIG. 5  illustrates the propagation of hot water front toward the faucet in the circulation mode of operation, in a time-location graph, for various values of the Time parameter. 
     Initially, at time to, the water throughout the pipes is at a low temperature (the ambient temperature); only the water near the hot pipe  22  are hot. 
     When the circulation is activated, a hot water front advances toward the faucet  3  and the cold water pipe  12 , as illustrated with temperature profiles at consecutive time periods t 0 , t 1 , t 2 , t 3  . . . . 
     At time t 5 , the hot wave arrives at the faucet, with the temperature of the water there being just the desired temperature Tdes. Circulation is stopped at that moment, and water can be supplied to the user. 
     Method of Operation to Supply Hot Water to User 
       FIG. 6  details a method of operation of the system, including: 
     1. accept user&#39;s order to supply hot water  51 
 
2. activate circulation: close valve  36 , open valves  32  and  34 , activate the circulation pump  41   52 
 
3. stop circulation when temperature at faucet reaches the desired value  53 
 
4. start supplying water at the faucet, to the user  54 
 
     Water supply starts either when ready, or only after a prompt from the user, see notes below. 
     5. supply water at faucet, while controlling the delivered water parameters  55 
 
6. Check: to stop the water supply?  56  if not—goto (5)
 
There may be various criteria for stopping the water supply, see notes below.
 
7. stop the water supply  57 
 
**End of method**
 
     Notes 
     1. There are three possible embodiments for starting to supply water to the user in the above method, step (4):
         a. As soon as water at the desired temperature is available at the faucet, the system will start the water flow out of the faucet, to the user;   b. When water is available at the desired temperature, the system will activate a READY indicator; the user may press a button to start the water supply when so desired. The READY indicator may be visual, audible or using other means.   c. Water now—the system performs circulation all the time, or intermittently as the need be, to keep hot water close at hand at the faucet. When the user requires hot water, the system may respond immediately.       

     If there are several faucets requiring immediate response, then the system may perform circulation to bring hot water to the first faucet, then circulation to bring hot water to the second, third, etc. 
     When the system senses (using temperature sensors) that the water at some faucet gets cold, circulation is again initiated to bring hot water to that faucet, by opening the first and second valves there. 
     2. The faucet may have one of the methods in (1) embodied therein, or the method may be programmed by the user—one user may prefer to activate the water supply as soon as possible, another may prefer to activate it at the right time.
 
3. There are various criteria for deciding when to stop the water supply in step (6), for example:
         a. The system detects the hot water supply is expected to be depleted soon therefore the desired temperature cannot be maintained for long; a suitable indication is issued, to warn the user to hurry and finish before water gets cold. Preferably, the system may include a display to indicate the time remaining for washing, using a countdown method for example:
 
9 minutes to finish, 8 minutes, 7, 6 . . . .
       

     In time, the system learns the characteristics of water supply and use, and may use the measured time variables to estimate the remaining hot water supply.
         b. The water is stopped immediately when the user so commands the system.   c. Pre-programmed mode—the system is programmed in advance to supply water for a predefined time period. When the time period ends, the water is closed. Preferably, a warning is given to user that the water will be shut up. The warning may precede the action by a predefined time interval, for example one minute, 5 minutes, etc.   d. any combination of the above (a to c).       

     This mode may be practical for hotels or where there is a water shortage and it is required to save on water. This mode is optional and should be used with caution, so as not to irritate customers by its application when not really necessary or justified. 
     4. In a preferred embodiment, when there is circulation, then all the users are shut off—there is no water supply to any user. Water supply to users only commences when circulation stops.
 
5. Close the water supply if the temperature is too high, to protect the user from possible injury.
 
Method for Preventing Water from Freezing in Pipes
 
     The method may use the system with water temperature measurement and water circulation as detailed in the present disclosure, in its various structures. 
     Additional temperature sensors may be installed in the water pipes in locations prone to freezing, these being connected to controller means or other automatic decision means. The method includes: 
     1. Measuring the water temperature in a plurality of locations in the water pipes of a domestic, industrial or commercial establishment. The temperature readings are transferred to a controller, computer or other automatic decision means.
 
2. If there is an imminent danger of water freezing apparent in the temperature readings from a specific location, water circulation is activated in that specific location.
 
     Optionally, heating is also applied. Often, just causing a movement in the water will suffice to prevent from freezing, even if the temperature is close to freezing point. Automatic water circulation means may also be used responsive to a low water temperature or to a dangerous rate of descent of the temperature, to prevent water from freezing in the pipes. 
     The water circulation may be applied selectively, to locations prone to freezing, for example using the valves as detailed in this application to form a water circulation loop while preventing water from flowing out. 
     **End of method** 
     Note: This is also a novel system feature: the system structure as detailed in this disclosure, with additional temperature sensors being installed in the water pipes in locations prone to freezing, with the additional proviso that these locations are within the domestic water system, that is a circulation pump can be activated to circulate the water in these locations. Additional water loops may be created in difficult locations, k as will be apparent to a person skilled in the art. This structure allows to fight/prevent water freezing using circulation in the pipes. 
       FIG. 7  illustrates the water temperature at the faucet during the circulation stage: 
     stage A—water temperature is that of cold water, the hot water front did not arrive at the faucet yet
 
stage B—water temperature is rising
 
stage C—circulation is slowed down or stopped, temperature is rising at a slower rate
 
stage D—circulation stopped, water delivery at constant temperature to user
 
     This shows the importance of stopping the circulation on time, so as not to exceed the desired temperature. 
     Method for Stopping the Water Circulation 
       FIG. 8  details the water circulation stopping process, comprising: 
     1. measure the water temperature  531  using the temperature sensor  45  in the faucet if two temperature sensors are used in the faucet (one at the hot water inlet, the other at the cold water inlet), then their readings may be advantageously used to better measure the temperature gradient in time and space. 
     The system may display the time remaining until water is ready and available to the user, for example based on prior experience. The system may measure the time required until hot water arrive to each faucet. When a user requires hot water, this value may be presented. 
     2. compute t(exp), the expected time for water to reach the desired  532  temperature. In a first embodiment, first order estimation: compute the rate of temperature change over time, dT/dt=delta(Temperature)/delta(time)—this is the slope of the graph T=f(time) in  FIG. 5 . 
     In other embodiments, higher derivatives of the T=f(time) function may also be used. This may achieve better performance, since the graph T=f(time) may not be linear. 
     3. time to stop circulation?  533   
     In a simple embodiment, check whether water at faucet reached the desired temperature, then it is time to stop the circulation. 
     In a more advanced embodiment, there is a parameter in the system, t(stop)=the time required to stop the water circulation, taking into consideration the inertia of the moving (flowing) mass of water and the response time of the circulation pump and the valves. 
     When the Expected time t(exp) equals the stopping time t(stop), it is time to stop the circulation. 
     the goal is to stop the circulation in time, so that the water temperature at the faucet  3  will not exceed the desired temperature. 
     4. stop the water circulation  534   
     Preferably, the circulation is stopped abruptly, to allow the use of a simple, low cost circulation pump and simple control means. A simple ON/OFF control is used. 
     In another embodiment, the circulation is not stopped abruptly, as this may cause excess pressure in the pipes and on the system components. If necessary, the circulation pump and/or the circulation valves  32 ,  34  are so activated as to gradually stop the circulation, at a desired rate according to engineering considerations. 
     Another consideration is the temperature rate of change, dT/dt. If the rate is high, stopping the circulation suddenly may cause an error in the faucet temperature—a small error or variation in the timing causes a large error in temperature. Gradually slowing down the rate of circulation gives better control over the final water temperature at the faucet when the circulation stops. Preferably, the system uses a circulation pump  41  of a type which allows water to flow therethrough when the pump is not activated. 
     This is an important functional and engineering consideration, as it will allow cold water to flow into the tank and thence to supply hot water even when the pump is not activated—the system working in the usual way. This is the mode of operation after hot water reaches the faucet and circulation is no longer necessary. 
     One preferred embodiment for the circulation pump  41  is a centrifugal pump. 
     Method for Stopping the Circulation 
     a. The circulation pump  41  is deactivated
 
b. after a time delay—close the valves  32  and  34  to gradually stop the water circulation. In another embodiment, it may be desirable to optimize the use of energy (to save energy). In this case, valves activation (opening and closing valves) is minimized. For example, to stop circulation—stop the circulating pump and wait for water to stop moving, without changing the settings of the valves.
 
     Then set the valves to the desired setting to supply water to the outlet, at the desired flow and temperature as in (c). The point is not to close the valves, in order to save energy. 
     c. after a time delay—adjust the valves  32  and  34  to the desired output flow and temperature
 
d. open the output valve  36 , only after the valves  32  and  34  settle at their desired settings and (optionally) after the user approves to open the water supply.
 
**End of method**
 
     In another embodiment of the Method, circulation is stopped by deactivating the pump  41 ; the valves  32  and  34  are then directly set to the desired output flow and temperature, skipping the step (b) of closing them. 
     In a preferred embodiment, valves  32  and  34  can be continuously adjusted, whereas valve  36  is ON/OFF (ON to supply water to user, OFF for water circulation). In another preferred embodiment, valves  32  and  34  are adjusted almost continuously, that is in fine steps, using a stepper motor for each valve, for example. 
     Method for Taking into Account Prior Orders and Also Occasional Users 
     The method comprises: 
     a. taking orders, learning habits of use of hot water
 
b. activating the heater in the hot water tank to heat the water as required (optional). Various means may be used to heat the water: solar energy, gas, electricity or a combination thereof.
 
c. hot water supply, stage  1 —preparation
         opening circulation valves in the faucet and then activating the circulation pump, where desired   stopping the circulation   Optional: activating a READY indicator, when hot water at the desired temperature are available for immediate use.
 
d. hot water supply, stage  2 —delivery
   adjusting circulation valves to required rate of outflow and temperature   opening the output valve   continuous, automatic adjustment of the valves to keep flow at desired rate and temperature, despite disturbances in the system—changes in water pressure, use of water by other customers, changes in hot/cold water temperature, etc.   changing flow parameters as requested by customer: flow rate, temperature   stopping the water delivery (closing the faucet). optionally, a display or an audio warning may be presented before water supply begins.
 
**End of method**
       

     3. New Micro Valve 
       FIG. 9  illustrates one embodiment of a faucet  3 . 
     The control unit (not shown) is connected to, and controls the operation of, the cold water valve  32 , hot water valve  34  and output water valve  36 . 
     The control unit also receives signals indicative of the measured temperature from the temperature sensors  45 ,  451  and  452 . 
     Preferably, the sensor  45  is immersed in water, to achieve a fast response and to measure the temperature in the water, preferably the incoming hot water; a sensor mounted in the structure of the faucet itself may not be satisfactory, as it may have a time delay in the measurement. 
     The other sensors  451 ,  452  may also be immersed in water. 
     The cold water inlet  31  and hot water inlet  33  each has a thread  312  and  332 , respectively to connect to the cold and hot water pipes. Other connecting means may be used rather than a threaded pipe, for example a snap-on connection. 
     Water is supplied through the water outlet  35 . 
     Optionally, an electricity generator  356  may be mounted at the water outlet  35  or in another location in the faucet, to convert water flow energy into electrical energy. The energy thus generated is used at the faucet to supply it with electrical energy. The energy thus generated may be used to charge secondary batteries there, which are the source of the unit  42  and the other electronic means there. 
     Other energy generation means may be used, for example based on Peltier effect (hot/cold water temperature differential) or other type of generator. 
     Alternately, low voltage wiring within the walls may be used to supply each faucet with electrical energy. If such wiring is used, it may also be used to transfer info from the sensors, as well as various data and commands between the components of the system. A low voltage is preferable as it may not pose a danger to users, in case of malfunction. 
     In a preferred embodiment, the only temperature sensor being used is the sensor  452  at the output  35  of the faucet (at the water supply to user). 
     In a preferred embodiment, the valves  32  and  34  have a variable rate of flow, which may be controllable by the control unit through control signals. The output valve  36  is preferably of a ON/OFF type—it is turned OFF when the faucet is not used or during water circulation; it is turned ON to supply water to the user. 
     The valves  32 ,  34  are further detailed with reference to  FIGS. 10-13 ; the valve  36  may be installed at the water outlet  35  of the unit in  FIG. 10 . 
     The valves  32 ,  34  may be implemented as two plungers working into the mixing chamber  366 . 
     The valve unit may include one to three temperature sensors. 
     The valve unit may include various sensors, besides the temperature sensors. These sensors may include pressure, water flow rate, etc. 
     In a preferred embodiment, a micro valve unit includes the valves  32  and  34 , for controlling the cold and hot water inflow, see  FIGS. 10 and 14 . 
     Preferably, the unit in  FIGS. 10 and 14  does not include the valve  36 , which is attached at the output of the unit there. 
     Preferably, the unit has a standard diameter, to fit in existing faucet infrastructure, for example a battery faucet, a wall-mount faucet or a deck-mounted faucet: 
     Option A: the diameter of the unit is about 35 mm (millimeters).
 
Option B: the diameter is about 25 mm
 
Option C: the diameter is about 20 mm
 
Option D: the diameter is in the range of about 25 to 35 mm
 
Option E: the diameter is in the range of about 15 to 25 mm
 
Other standard diameter values may be used.
 
       FIG. 10  illustrates two cross-sectional longitudinal views of a preferred embodiment of the new micro valve, detailing the cold water inlet  31  and hot water inlet  33 , and the water outlet  35 . 
     The hot water valve  34  is shown in its fully closed state, and the cold water valve  32  is shown in its fully opened state. 
     A temperature sensor  452  may be mounted at the output of the device. The device uses plunger means  327 ,  347  and electrical motors  324  and  344  with optional transmission means  325  and  345  to control the water flow, see also  FIG. 11 . 
     A novel feature of this structure is the use of plungers with a mixing chamber  366 . 
       FIG. 11  details an exploded view of a valve structure. This valve may be used for example in the faucet structures of  FIG. 9 ,  10  or  12 . 
     The electrical motor  324  acts upon the transmission means (gear)  325  to rotate the part with inner thread  326 . This rotation causes the plunger  327  to move up (to open the valve) or down (to close it). 
     Also shown are the cold water inlet  31  (in this example; the same structure may be implemented for the hot water), and the valve outlet  316  toward the mixing chamber  366 , see  FIG. 12 . 
     The electrical motor  324  may be pulse activated as illustrated with the graph of Vm vs. time. The duty cycle of the voltage may change. The polarity may be reversed to reverse the direction of movement. In another embodiment, a stepper motor may be used. 
     The gear ratio of the gear between motor  324  and plunger  327  may be so devised as to minimise the mechanical energy required to move the plunger  327 . As illustrated in the graph there, there may be an optimal gear ratio (OGR) for maximal performance, where there is optimal matching between the impedance of the source and the load, also taking into account the water pressure in inlet  31 . 
     A possible problem with this embodiment is the water pressure in inlet  31 , which opposes a down movement of plunger  327 , thus causing a waste of energy. A possible solution may be a loaded spring to always push the plunger  327  down, to counter the force of the water pressure; the motor  324  then only has to provide the differential force (a lower value force) to move the plunger  327  up or down. Another solution is illustrated in  FIG. 21 , which details an embodiment wherein the water flows in the opposite direction, from 316 toward  31 ; in this case, water pressure will not oppose the closing of the valve. 
       FIG. 12  illustrates a functional cross-sectional view of a preferred embodiment of the new micro valve, detailing the cold water inlet  31  and hot water inlet  33 , and the water outlet  35 . 
     In one embodiment, there are the temperature sensors (TS) located as illustrated: TS  451  near the cold water inlet  31 , TS  452  in the mixing chamber  366  and TS  45  located near the hot water inlet  33 . The sensors are connected to the controller  42 . In another embodiment, only the sensor  452  is used. 
     The electrical motor  324  acts upon the optional transmission means (gear)  325  to move the plunger  327  which controls the cold water supply from the cold water inlet  31 . 
     Similarly, the electrical motor  344  acts upon the optional transmission means  345  to move the plunger  347  which controls the hot water supply from the hot water inlet  33 . 
     Water from the hot and cold inlets will mix in the mixing chamber  366 , the result being water at the desired temperature which flows out outlet  35 . 
     Flow to the outlet  35  is controlled by means  357  comprising water flow control means as known in the art. The means  357  is moved by the actuator means  354 . In a preferred embodiment, means  357  has only two positions, ON or OFF. A suitable embodiment for the actuator  354  may be an electrical solenoid. A possible ON/OFF valve may use a membrane valve. 
       FIG. 13  illustrates a functional cross-sectional view of a device for mixing fluids from a plurality of sources. For example, people may desire to use either potable water or sea water, then to mix hot and cold water. 
     In this embodiment, hot water may use a fast heater on the pipe, such as that manufactured by Atmor(tm). The device may also find applications in mixing liquids in industry, or to mix gases. 
     For example, a sea water (cold) inlet  318  and (hot) inlet  338 , with plungers  3272  and  3472  controlling the inflow of fluids to mixing chamber  3662 ; a third unit with plungers  3273  and  3473 , with the fluids being mixed in mixing chamber  3663 . 
     The output flow may be controlled with the plunger  3476  at the outlet of the device, as illustrated. 
     The device in  FIG. 13  is stackable; more units may be used to allow a multitude of liquids and/or gases to be mixed in a plurality of mixing chambers along a processing path. 
       FIG. 14  illustrates two cross-sectional longitudinal views of yet another embodiment of the new micro valve detailing the cold water inlet  31  and hot water inlet  33 . 
     Also illustrated is the mixing chamber  366 , where hot water is mixed with cold water when water is supplied to the user through the water outlet  35 . 
     In this figure, the hot water valve plunger  347  is shown in its fully closed state, and the cold water valve plunger  327  is shown in its fully opened state. Also illustrated are the temperature sensors  45 ,  451 ,  453  for the hot and cold water inlets, and the mixing chamber respectively. 
       FIG. 15  illustrates a bottom view of the faucet, illustrating the cold water inlet  31 , the hot water inlet  33  and the water outlet  35 . 
     4. Human-Machine Interface 
       FIG. 16  illustrates one embodiment of a human-machine interface, more specifically a control and display panel usable for the unit  42  for controlling a hot/cold water tap or faucet. 
     The panel may include a temperature readout  402 , and hot and cold water selection buttons  406  and  408 . 
     If cold water is desired, pressing button  406  opens the cold water inlet valve. If hot water is desired, pressing button  408  will activate the cycling mechanism followed by the water delivery mechanism as detailed elsewhere in the present disclosure. 
     The temperature of hot water may be set using the function selection mechanism  410  and optional buttons. 
     Optional buttons may include:
         A function selection mechanism  410  for selecting between different functions such as “temperature”, “time”, “flow”, etc. Each function selected may be indicated by appropriate indicators:  422 ,  432 ,  444  respectively.   “Up” and “Down” buttons  440  and  442  used for changing up and down (setting) the value of a chosen function.   A timer  430  for setting a desired water use time, a “time” indicator  432 , memory means  434  for storing set temperatures and/or times, and outlet selection buttons  452  and  454  for selecting one of two outlets.       

       FIG. 17  illustrates another embodiment of the control panel. 
     The panel includes a temperature readout  402 , Ready indicator  450 , hot water selection button  408  to supply water at a desired temperature, and cold water button  406  for selecting cold water. 
     A stop button  460  may be used to immediately stop the water flow if activated. 
     The programmed buttons  461 ,  462 ,  463 ,  464 ,  465 , etc.—each will supply water with pre-programmed parameters including for example temperature, flow rate, time of operation (optional—if to shut up the faucet automatically), etc. 
     Thus, each user may program a button (or several buttons) with the programs they may use. The faucet is thus personalized for each user. 
     A programming area  469  includes various buttons to program the faucet, for immediate or delayed delivery. 
     The panel includes a temperature readout  402 , Ready indicator  450 , hot water selection button  408  to supply water at a desired temperature, and cold water 
       FIG. 18  illustrates yet another embodiment of the control panel, using a control lever  471  with a rotary joint  472 . 
     Moving the lever Left-Right controls the temperature—more hot to the right. 
     Moving the lever Up-Down controls the water flow, from fully stopped (down) to full rate flow (up). 
       FIG. 19  illustrates yet another embodiment of the control panel, using two rotary controls: A temperature control knob  473  sets the temperature to a desired value; a flow control knob  474  controls the rate of flow of supplied water. Push buttons may be used to replace the knob  474 . 
     Method of Operation 
     a. the user selects a desired temperature using knob  473 
 
b. the system activates water circulation, until hot water is ready at the faucet
 
c. the system sets the READY indicator  422 , to signal that hot water is available.
 
d. When the flow knob  474  is rotated clockwise, water begins to flow.
 
The control input  474  may be a knob to be rotated, or push buttons to be pressed.
 
**End of method**
 
6. Protecting Users from Burns Due to Exposure to Hot Water
 
       FIG. 20  illustrates a system for overall control of the temperature of the hot water supply to an apartment or house. New safety standards demand to limit the temperature of the hot water supply, to protect users from accidental burns if exposed to hot water only. The temperature of hot water supply should be limited to a predetermined value, for example 45 degrees Celsius. 
     The structure in  FIG. 20  may be used to achieve compliance with such safety standards. 
       FIG. 20  illustrates a system for limiting the maximum temperature of hot water supplied to a house or apartment. 
     It is possible to limit the temperature of the water tank to, for example, 40 or 45 degrees Celsius; however, this results in much less hot water than a tank with water at 80 to 90 degrees Celsius. If the water are heated to a higher temperature, then the heat capacity is increased, more water may be used before the supply ends. (Of course the temperature may be reduced for economy reasons where less use is to be expected). 
     If the water in the tank are heated to a higher temperature, however, there is the danger of a user&#39;s injury, in case of exposure to hot water. 
     And, indeed, there are now safety standards which limit the maximum temperature of hot water supplied to an apartment, to prevent such dangers. 
     The novel approach taken in the present invention is to heat the water in the tank  21  to a higher temperature, to increase the heat capacity of the system. At the same time, limiting the maximum temperature of water supplied to the apartment by mixing with cold water, in such a proportion of hot/cold water as to ensure the temperature of hot water to the apartment is kept within safe margins. 
     As illustrated in  FIG. 20 , the valves  32  and  34  are electrically controlled. The valves  32  and  34  control the rate of flow of hold and hot water, respectively. The temperature of the water, preferably in a mixing chamber, is measured with temperature sensor  452 . 
     The valves  32  and  34  are so controlled as to achieve a desired temperature at the output of the system in pipe  22 . Pipe  22  is the hot water supply to the apartment. 
     Either a circulating pump  41  in the cold water, or a circulating pump  416  in the hot water, may be used. 
     7. Operating Panel with Advanced Display Means 
     A novel operating panel may include advanced display means, including for example VGA or video or television display for viewing TV or movies or other info while in the shower. For example, the program means  469  in  FIG. 17  may include video display means such as a LCD device, having a dual use—both to control the hot/cold water supply, and to view a TV program, an alarm/monitoring camera, etc. 
     A multi-functional display may be used both to control the water supply and subsequently to present other information. The display may include a touch screen, to be also used for inputting data and/or commands. Preferably, the display should be resistant to water and vapors. 
     It will be recognized that the foregoing is but one example of an apparatus and method within the scope of the present invention and that various modifications will occur to those skilled in the art upon reading the disclosure set forth hereinbefore.