US20120164592A1 - Water Heating System - Google Patents

Water Heating System Download PDF

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Publication number
US20120164592A1
US20120164592A1 US13/394,378 US201013394378A US2012164592A1 US 20120164592 A1 US20120164592 A1 US 20120164592A1 US 201013394378 A US201013394378 A US 201013394378A US 2012164592 A1 US2012164592 A1 US 2012164592A1
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tank
water
temperature
heaters
comparison
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Israel Maoz
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    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F24—HEATING; RANGES; VENTILATING
    • F24H—FLUID HEATERS, e.g. WATER OR AIR HEATERS, HAVING HEAT-GENERATING MEANS, e.g. HEAT PUMPS, IN GENERAL
    • F24H9/00—Details
    • F24H9/20—Arrangement or mounting of control or safety devices
    • F24H9/2007—Arrangement or mounting of control or safety devices for water heaters
    • F24H9/2014—Arrangement or mounting of control or safety devices for water heaters using electrical energy supply
    • F24H9/2021—Storage heaters
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F24—HEATING; RANGES; VENTILATING
    • F24D—DOMESTIC- OR SPACE-HEATING SYSTEMS, e.g. CENTRAL HEATING SYSTEMS; DOMESTIC HOT-WATER SUPPLY SYSTEMS; ELEMENTS OR COMPONENTS THEREFOR
    • F24D19/00—Details
    • F24D19/10—Arrangement or mounting of control or safety devices
    • F24D19/1006—Arrangement or mounting of control or safety devices for water heating systems
    • F24D19/1051—Arrangement or mounting of control or safety devices for water heating systems for domestic hot water
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F24—HEATING; RANGES; VENTILATING
    • F24H—FLUID HEATERS, e.g. WATER OR AIR HEATERS, HAVING HEAT-GENERATING MEANS, e.g. HEAT PUMPS, IN GENERAL
    • F24H15/00—Control of fluid heaters
    • F24H15/10—Control of fluid heaters characterised by the purpose of the control
    • F24H15/144—Measuring or calculating energy consumption
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F24—HEATING; RANGES; VENTILATING
    • F24H—FLUID HEATERS, e.g. WATER OR AIR HEATERS, HAVING HEAT-GENERATING MEANS, e.g. HEAT PUMPS, IN GENERAL
    • F24H15/00—Control of fluid heaters
    • F24H15/10—Control of fluid heaters characterised by the purpose of the control
    • F24H15/172—Scheduling based on user demand, e.g. determining starting point of heating
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F24—HEATING; RANGES; VENTILATING
    • F24H—FLUID HEATERS, e.g. WATER OR AIR HEATERS, HAVING HEAT-GENERATING MEANS, e.g. HEAT PUMPS, IN GENERAL
    • F24H15/00—Control of fluid heaters
    • F24H15/10—Control of fluid heaters characterised by the purpose of the control
    • F24H15/174—Supplying heated water with desired temperature or desired range of temperature
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F24—HEATING; RANGES; VENTILATING
    • F24H—FLUID HEATERS, e.g. WATER OR AIR HEATERS, HAVING HEAT-GENERATING MEANS, e.g. HEAT PUMPS, IN GENERAL
    • F24H15/00—Control of fluid heaters
    • F24H15/20—Control of fluid heaters characterised by control inputs
    • F24H15/212—Temperature of the water
    • F24H15/215—Temperature of the water before heating
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F24—HEATING; RANGES; VENTILATING
    • F24H—FLUID HEATERS, e.g. WATER OR AIR HEATERS, HAVING HEAT-GENERATING MEANS, e.g. HEAT PUMPS, IN GENERAL
    • F24H15/00—Control of fluid heaters
    • F24H15/20—Control of fluid heaters characterised by control inputs
    • F24H15/212—Temperature of the water
    • F24H15/223—Temperature of the water in the water storage tank
    • F24H15/225—Temperature of the water in the water storage tank at different heights of the tank
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F24—HEATING; RANGES; VENTILATING
    • F24H—FLUID HEATERS, e.g. WATER OR AIR HEATERS, HAVING HEAT-GENERATING MEANS, e.g. HEAT PUMPS, IN GENERAL
    • F24H15/00—Control of fluid heaters
    • F24H15/20—Control of fluid heaters characterised by control inputs
    • F24H15/238—Flow rate
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F24—HEATING; RANGES; VENTILATING
    • F24H—FLUID HEATERS, e.g. WATER OR AIR HEATERS, HAVING HEAT-GENERATING MEANS, e.g. HEAT PUMPS, IN GENERAL
    • F24H15/00—Control of fluid heaters
    • F24H15/30—Control of fluid heaters characterised by control outputs; characterised by the components to be controlled
    • F24H15/305—Control of valves
    • F24H15/31—Control of valves of valves having only one inlet port and one outlet port, e.g. flow rate regulating valves
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F24—HEATING; RANGES; VENTILATING
    • F24H—FLUID HEATERS, e.g. WATER OR AIR HEATERS, HAVING HEAT-GENERATING MEANS, e.g. HEAT PUMPS, IN GENERAL
    • F24H15/00—Control of fluid heaters
    • F24H15/30—Control of fluid heaters characterised by control outputs; characterised by the components to be controlled
    • F24H15/335—Control of pumps, e.g. on-off control
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F24—HEATING; RANGES; VENTILATING
    • F24H—FLUID HEATERS, e.g. WATER OR AIR HEATERS, HAVING HEAT-GENERATING MEANS, e.g. HEAT PUMPS, IN GENERAL
    • F24H15/00—Control of fluid heaters
    • F24H15/30—Control of fluid heaters characterised by control outputs; characterised by the components to be controlled
    • F24H15/355—Control of heat-generating means in heaters
    • F24H15/37—Control of heat-generating means in heaters of electric heaters
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F24—HEATING; RANGES; VENTILATING
    • F24H—FLUID HEATERS, e.g. WATER OR AIR HEATERS, HAVING HEAT-GENERATING MEANS, e.g. HEAT PUMPS, IN GENERAL
    • F24H15/00—Control of fluid heaters
    • F24H15/30—Control of fluid heaters characterised by control outputs; characterised by the components to be controlled
    • F24H15/395—Information to users, e.g. alarms
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F24—HEATING; RANGES; VENTILATING
    • F24H—FLUID HEATERS, e.g. WATER OR AIR HEATERS, HAVING HEAT-GENERATING MEANS, e.g. HEAT PUMPS, IN GENERAL
    • F24H15/00—Control of fluid heaters
    • F24H15/40—Control of fluid heaters characterised by the type of controllers
    • F24H15/414—Control of fluid heaters characterised by the type of controllers using electronic processing, e.g. computer-based
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F24—HEATING; RANGES; VENTILATING
    • F24H—FLUID HEATERS, e.g. WATER OR AIR HEATERS, HAVING HEAT-GENERATING MEANS, e.g. HEAT PUMPS, IN GENERAL
    • F24H15/00—Control of fluid heaters
    • F24H15/40—Control of fluid heaters characterised by the type of controllers
    • F24H15/414—Control of fluid heaters characterised by the type of controllers using electronic processing, e.g. computer-based
    • F24H15/45—Control of fluid heaters characterised by the type of controllers using electronic processing, e.g. computer-based remotely accessible
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F24—HEATING; RANGES; VENTILATING
    • F24H—FLUID HEATERS, e.g. WATER OR AIR HEATERS, HAVING HEAT-GENERATING MEANS, e.g. HEAT PUMPS, IN GENERAL
    • F24H9/00—Details
    • F24H9/20—Arrangement or mounting of control or safety devices
    • F24H9/2007—Arrangement or mounting of control or safety devices for water heaters
    • F24H9/2035—Arrangement or mounting of control or safety devices for water heaters using fluid fuel

Definitions

  • the present invention relates generally to water heating, and specifically to heating of water within a tank.
  • a hot water tank is typically used in a household, as part of the water supply of the household, for supplying hot water for showering, washing, and other domestic uses.
  • a hot water tank may also be used in commercial and industrial applications, in a similar configuration, or optionally modified configurations, to that used in a household.
  • the hot water tank typically receives water from a cold water supply, and heats the received cold water.
  • Japanese Patent Application 58-130932 to Kubota et al., whose disclosure is incorporated herein by reference, is claimed to relate to a hot water storage-type water heater such as an electrical storage-type water heater.
  • Japanese Patent Application 2006-046713 to Satou et al. whose disclosure is incorporated herein by reference, is claimed to display an amount of mixed warm water from a hot water storage tank when the water is being used.
  • An embodiment of the present invention provides a method, including:
  • making the determination includes evaluating a heat loss factor of a temperature drop from the hot water tank to a water outlet supplying the user, and incorporating the heat loss factor in the determination.
  • making the determination includes measuring a temperature of a cold water supply to the user, and incorporating the temperature in the determination.
  • making the determination includes making an evaluation if the mixed water is to be heated, and in response to the evaluation presenting a query to the user whether the mixed water is to be heated. Activating the heater may be in response to a positive response to the query.
  • activating the heater includes determining that a volume of water to be delivered to the user is less than or equal to a capacity of the hot water tank and that an effective temperature of water from the hot water tank is less than the target temperature.
  • activating the heater includes determining that a volume of water to be delivered to the user is equal to a capacity of the hot water tank and that the volume of water is at a maximum operating temperature of the tank.
  • activating the heater includes determining that a volume of water to be delivered to the user is greater than or equal to a capacity of the hot water tank, and is less than a maximum volume of water to be delivered to the user at the target temperature.
  • making the determination includes determining that a maximum heat capacity of water in the tank is insufficient for satisfying the instruction, and in response determining a length of time required to heat water entering the tank.
  • apparatus including:
  • control unit which is configured:
  • the first vertical array of heaters are located according to a first vertical distribution and the second vertical array of sensors are located according to a second vertical distribution.
  • the second vertical distribution may be equal to the first vertical distribution.
  • the first vertical array includes three heaters and the second vertical array includes three sensors, and the three heaters divide the hot water tank into three equal volumes.
  • the second vertical distribution may be different from the first vertical distribution.
  • control unit is configured to activate the at least one of the heaters in response to evaluating a heat loss factor of a temperature drop from the hot water tank to a water outlet supplying the user.
  • control unit is configured to activate the at least one of the heaters in response to measuring a temperature of a cold water supply to the user.
  • control unit is configured to activate the at least one of the heaters in response to receiving a positive response to a query to the user whether water within the hot water tank is to be heated.
  • the instruction is indicative of a temperature and a volume of the supply of water.
  • control unit is configured to activate the at least one of the heaters in response to analyzing sequentially heat contents of respective sections of the tank defined by the first vertical array.
  • the first vertical array defines respective sections of the tank, and the control unit is configured to activate the at least one of the heaters in response to maintaining that no given section is heated to a first temperature that is higher than a second temperature of a further section above the given section.
  • the instruction includes determining that a maximum heat capacity of water in the tank is insufficient for satisfying the instruction, and in response determining a length of time required to heat water entering the tank.
  • apparatus including:
  • control unit which is configured to receive an instruction from a user of the hot water tank indicating a target temperature and a duration of a supply of water
  • a method including:
  • a method including:
  • control unit which is configured to receive a first instruction from a first user of the hot water tank indicating a first requirement of a first supply of water
  • a method including:
  • FIG. 1 is a schematic illustration of the operation of a water heating system, according to an embodiment of the present invention
  • FIGS. 2A , 2 B, and 3 are respectively first, second and third block diagrams illustrating the components of the system of FIG. 1 , according to an embodiment of the present invention
  • FIG. 4 is a flow chart describing steps that are implemented in operation of the system of FIG. 1 , according to an embodiment of the present invention:
  • FIGS. 5A , 5 B, and 6 are respectively first, second and third block diagrams illustrating the components of an alternative water heating system, according to an embodiment of the present invention
  • FIGS. 8A-8N illustrate a flow chart followed by a processing unit in making its decisions in steps of the flow chart of FIG. 7 , according to an embodiment of the present invention.
  • Embodiments of the present invention seek to provide methods and apparatus for efficient heating of hot water in a water supply system.
  • the water supply system comprises a hot water tank and a cold water supply. Water from the tank and from the cold water supply may be mixed by a user to generate water for the user.
  • the user is able to input, as instructions giving user requirements, a target (user) temperature for supply of the water.
  • the system calculates, typically immediately, one or more temperatures to which water in the tank is to be heated to supply the requirements, and activates one or more heaters to heat the water to the calculated temperatures.
  • a display unit provides indications to the user how much water (mixed) is immediately available, or whether water in the tank needs to be heated to satisfy the user requirements.
  • the instructions comprise a required duration of supply of the water, and the required duration may be incorporated into the calculation of the one or more temperatures.
  • the water in the tank is immediately mixed by the pump.
  • water in a hot water tank stratifies so that a hot water layer is above a cold water layer.
  • the mixing causes the different temperature water layers to homogenize, so that all the water in the tank is at one temperature.
  • a control unit measures the temperature, and determines if the mixed water (in the tank) will satisfy the user instructions, typically after being heated, or typically after being mixed with water from the cold water supply.
  • the alternative embodiment comprises an array of heaters deployed vertically, and an array of temperature sensors that are also deployed vertically.
  • the control unit measures the water temperatures in the stratified sections of the tank, and determines if one or more of the heaters in the tank are to be activated to satisfy the user requirements.
  • the heaters are activated in such a way so that the stratification is typically maintained.
  • FIG. 1 is a schematic illustration of the operation of a water heating system 20 , according to an embodiment of the present invention.
  • system 20 is shown, by way of example, to be used to heat water for a shower 22 in a dwelling.
  • embodiments of the present invention are not limited to such a use, but rather may be used wherever a partially or completely heated water supply is operative.
  • System 20 comprises a hot water storage tank 24 , wherein water that is to be used in the shower is stored.
  • Tank 24 is connected by piping 25 to a mixing faucet 26 and a shower head 28 within the shower, and the faucet is operated by a user (not shown) of the shower to control the flow of water to the shower head.
  • System 20 also comprises a control unit 30 , which enables the user to operate the system.
  • Control unit 30 allows the user to input data to the system via a data input device 32 , which is assumed herein, by way of example, to comprises a keypad, although the data input device may use any other convenient mechanism, such as a touchpad and/or switches, to input data.
  • Control unit 30 also comprises a data output device 34 , which provides output information to the user of system 20 .
  • Data output device 34 is assumed herein, by way of example, to comprise an LCD (liquid crystal display) screen so that the device is also referred to herein as display 34 .
  • the device may comprise another type of visual display, and/or an auditory output device, and those having ordinary skill in the art will be able to adapt the description, mutatis mutandis, for output devices other than an LCD.
  • system 20 The elements of system 20 , and their method of operation, are described in more detail below with respect to FIGS. 2A , 2 B, and 3 .
  • FIGS. 2A , 2 B, and 3 are respectively first, second and third block diagrams illustrating the components of system 20 , according to an embodiment of the present invention.
  • control unit 30 comprises a processing unit 102 , which operates system 20 , and which typically comprises a processor 103 coupled to a memory 105 , wherein are stored operating instructions for the processor.
  • Processing unit 102 may be implemented from “off-the-shelf” components, custom-built components, or a combination of off-the-shelf and custom-built components.
  • processing unit 102 may comprise a field programmable gate array (FPGA) and/or an application specific integrated circuit (ASIC).
  • Memory 105 typically comprises volatile and/or non-volatile memories.
  • unit 102 comprises an M91-2-UN2 unit produced by Unitronics Inc, of Quincy, Mass.
  • a power supply 104 in control unit 30 supplies power to processing unit 102 , to data input device 32 , to data output device 34 , to transceiver 110 , and to other elements of system 20 , such as valves 118 , 129 , 131 , and a pump 127 , described further below.
  • the power supply may be battery and/or line operated.
  • a cold water temperature sensor 112 is typically connected to pipe 113 , so as to provide a measure of the temperature of the cold water supply to unit 30 .
  • Cold water sensor 112 may comprise a thermistor, or any other convenient temperature measuring device having a characteristic from which unit 30 is able to derive the temperature of the cold water supply.
  • sensor 112 comprises a multiplicity of generally similar temperature sensors respectively connected to different locations of the cold water supply. Such embodiments may be implemented in the case of, for example, a residence where the temperature within the residence may be higher than the temperature of the external water supply to the residence. Typically, in the case of a plurality of temperature sensors, the lowest temperature reading of the sensors is used by control unit 30 as a cold water temperature value Tc in any calculations involving Tc. Cold water temperature Tc, and calculations involving the cold water temperature, are described further below.
  • more than one water heating system 20 may be installed, for example in a building comprising a group of apartments. In such an installation it will be appreciated that, since the multiple systems are fed by a common cold water supply, a single sensor 112 may be used for the multiple water heating systems.
  • a heater 120 is installed in tank 24 .
  • the heater may be switched on or off, under control of unit 30 , by a heater switch 124 .
  • Heater 120 typically comprises an electrical resistor which is connected, via switch 124 , to the line supply. Alternatively, heater 120 may generate its heat non-electrically. For example, the heater may be operated by gas. While heater 120 typically comprises one heating element, it may comprise two or more separate elements.
  • a tank water temperature sensor 114 is also installed close to the bottom of tank 24 , to provide a measure of the temperature of water at the tank bottom to unit 30 .
  • Tank water sensor 114 is typically similar to sensor 112 , described above.
  • the hot water outlet from tank 24 comprises an outlet pipe 111 that is connected to the upper internal surface of the tank, so that hot water from the tank exits from an upper portion of the tank.
  • a hot water outlet valve 118 controlled to be open or closed by unit 30 , is connected in pipe 111 . After valve 118 pipe 111 is connected to a hot water inlet of mixing faucet 26 .
  • a pump 127 controlled by unit 30 , connects, via a coupling pipe 128 , inlet pipe 113 and outlet pipe 111 .
  • pipe 128 is implemented to connect to the inlet pipe and the outlet pipe below valve 129 and valve 118 respectively.
  • Activation of pump 127 by unit 30 initiates transfer of water between the inlet and outlet pipes. If the pump is deactivated by unit 30 , the pump acts to prevent water transfer between the inlet and outlet pipes.
  • a pipe 113 A connects the cold water supply to a cold water inlet of mixing faucet 26 .
  • pipe 113 A there is an on/off valve 131 , the state of the valve being controlled by unit 30 .
  • a flow sensor 130 is connected in the outlet of mixing faucet 26 .
  • Sensor 130 provides signals to unit 30 enabling the unit to calculate a rate of flow of water from the faucet.
  • FIG. 2B schematically illustrates processing unit 102 in more detail.
  • unit 102 comprises processor 103 and memory 105 .
  • Memory 105 comprises a number of modules, as listed below. The modules may be implemented in software, hardware, or a combination of software and hardware.
  • Module 513 enables the processor to calculate a time period (length of time) Ma within which mixed water is available to the system user.
  • a maximum-time module 514 enables the processor to calculate a maximum time period (length of time) Mm for which mixed water is available to the system user.
  • a required-(tank) temperature module 515 enables the processor to calculate a required temperature Tr of water in tank 24 , that is needed in order to meet user requirements (required-time).
  • a difference-time module 516 enables the processor to calculate a difference between a required-time which is greater than the maximum-time and the maximum-time.
  • An optional flow rate module 517 for calculating a faucet flow rate is provided.
  • a real time clock module 519 that provides time signals to the processor.
  • memory 105 typically comprises a general memory region 520 that processor 103 is able to use during operation of system 20 .
  • Region 520 is typically used, inter alia, to store system parameters, such as the volume of tank 24 , a set point temperature and the like, that are used by the processor in performing its calculations.
  • FIG. 4 is a flow chart describing steps that are implemented in operation of system 20 , according to an embodiment of the present invention. Except where otherwise indicated, the following description of the flow chart assumes an embodiment wherein flow sensor 130 and flow rate module 517 are not present, and that the flow rate from faucet 26 is Fr.
  • a system installation step 600 operational parameters of the system are input to unit 30 , which typically stores the parameters in memory region 520 .
  • a technician typically performs step 600 using data input device 32 , although any other convenient method for inputting the parameters, such as via transceiver 110 , may be used.
  • Parameters which are stored in step 600 comprise:
  • T faucet is the temperature of the water at the hot water inlet of the faucet
  • T tank is the temperature of the water exiting from tank 24 .
  • a user step 601 the user inputs a user desired target temperature, Tu, using input device 32 .
  • the value of Tu input by the user is typically confirmed by display 34 .
  • processing unit 102 samples signals from sensor 112 , and converts the signals to a cold water temperature value, Tc.
  • Tc is the temperature of the cold water inlet to faucet 26 and to tank 24 .
  • the sampling is typically performed in response to the start of operations of the user in step 601 , and may also be performed at other times, continuously or intermittently, during operation of system 20 .
  • processing unit 102 sends signals for closing valves 118 and 129 . Once the valves have closed, the processing unit sends a signal to activate pump 127 for its set time of operation Po, using real time clock module 519 .
  • pump 127 acts as a water mixing pump, extracting warm water from the upper outlet of tank 24 and injecting it via pipe 113 B into the lower part of the tank, so that water that is initially at different temperatures in the tank is mixed.
  • the processing unit sends a signal to deactivate the pump, so that the pump acts to prevent water traversing coupling pipe 128 ; the processing unit also sends signals for opening valves 118 and 129 .
  • processing unit 102 determines a measured actual temperature Tt of the mixed water in tank 24 by sampling signals from sensor 114 .
  • the processing unit converts temperature Tt to an effective temperature Te at the hot water inlet of faucet 26 , using the heat loss factor Lr, according to equation (2):
  • a first comparison 605 the processing unit compares Te(Tt ⁇ Lr) and Tu. If Te ⁇ Tu, processing unit continues to a display step 608 . If Te ⁇ Tu, the processing unit continues to a calculation step 606 .
  • calculation step 606 the processing unit uses available-time module 513 to calculate an available time interval (length of time) Ma during which mixed water may exit from faucet 26 at temperature Tu.
  • the calculation performed with the module is based on the law of conservation of energy, and uses equation (3):
  • a data output step 607 the processing unit presents the value calculated in step 606 on display 34 .
  • display 34 shows, on instructions from the processing unit, that there is no mixed water presently available, at Tu, from faucet 26 .
  • processing unit 102 uses display 34 to query if the user wants to heat the water in tank 24 . If the return from the query is negative, i.e., the water is not to be heated in the tank, the process illustrated by the flow chart ends.
  • processing unit 102 uses maximum-time module 514 to calculate a maximum time interval (length of time), Mm, during which the user could receive mixed water at temperature Tu from faucet 26 .
  • Mm maximum time interval
  • the calculation is based on assuming that all the water in tank 24 is raised to the maximum set temperature Ts of the tank.
  • the processing unit and the maximum-time module use equation (4) to calculate Mm:
  • a user step 611 the user inputs, to processing unit 102 , a length of time required, Mr, for mixed water at temperature Tu (the user required temperature) to be received from faucet 26 .
  • the user operates input device 32 to provide the value of Mr to the processing unit.
  • the input is echoed on display 34 .
  • processing unit 102 compares Mr and Mm. If Mr ⁇ Mm, i.e. the user required time is less than or equal to the maximum time that water at the user desired temperature Tu can be provided, so that the system is able to satisfy the user instruction, the flow chart continues to a required temperature calculation step 613 . If Mr>Mm, i.e. the user required time is more than the maximum time that water can be provided, so that the system is unable to satisfy the instruction from the user within one cycle of heating, i.e., heating to the set point temperature Ts, the flow chart continues to a heating step 617 .
  • processing unit 102 uses required-temperature module 515 to determine the required temperature Tr to which the water in tank 24 is to be heated.
  • Module 515 stores a number of conditions which the processing unit applies.
  • a first condition applies if the volume of water to be delivered from faucet 26 is less than or equal to the tank capacity Ct, but the effective temperature Te of the water from the tank is less than the user desired temperature Tu. If this condition is true, then the processing unit sets Te to be at least equal to Tu.
  • Te is assumed to be set equal to Tu. It will be understood that in this case no cold water is required to be mixed at faucet 26 , so that typically processing unit 102 sets valve 131 closed.
  • a third condition applies if the volume of water to be delivered from faucet 26 is greater than or equal to the capacity of the tank (to deliver water at the user desired temperature Tu), corresponding to
  • Mr ⁇ Fr ⁇ Tu Ct ⁇ Tr ⁇ Lr+ ( Mr ⁇ Fr ⁇ Ct ) Tc (6)
  • equation (6) the left side of the equation is an expression for the total heat energy in the mixed water.
  • the first term is an expression for the heat energy from the tank, and the second term is an expression for the heat energy from the cold water.
  • Tr Mr ⁇ Fr ⁇ ( Tu - Tc ) + Ct ⁇ Tc Ct ⁇ Lr ( 7 )
  • processing unit 102 sends a signal to switch 124 to activate heater 120 , and the processing unit also monitors the tank temperature Tt with sensor 114 .
  • the heater is activated and the temperature in the tank is monitored until the required temperature Tr is reached.
  • Tr is derived from step 613 .
  • display 34 provides an indication that the tank is being heated, the value of Tr, and/or an estimate of the length of time needed to reach temperature Tr.
  • a display step 616 once temperature Tr has been reached, display 34 indicates to the user that the water in tank 24 has been sufficiently heated to satisfy the user's requirements, i.e., that there is sufficient hot water for faucet 26 to supply water to the user at temperature Tu for a time Mr.
  • the flow chart then ends.
  • heating step 617 (which, as stated above, is implemented if in comparison 612 Mr>Mm), processing unit 102 sends a signal to switch 124 to activate heater 120 , and the processing unit also monitors the tank temperature Tt with sensor 114 . The heater is activated and the temperature in the tank is monitored until the set point temperature Ts is reached. Ts is derived from general memory 520 . Typically, display 34 provides an indication that the tank is being heated, the value of Ts, and/or an estimate of the length of time needed to reach temperature Ts using a process similar to that described below for evaluating a required heating time Mh.
  • a deactivation step 618 the processing unit sends a signal to switch 124 to deactivate the heater once the set point temperature Ts is reached.
  • processing unit 102 continues to monitor the tank temperature, so that if the tank temperature falls below Ts before a use of water from the tank, the processing unit may reactivate the heater.
  • processing unit 102 uses heating-time module 518 to calculate a required heating-time Mh for activation of heater 120 .
  • Heating-time Mh is the time needed, beyond the one cycle of heating as denoted in steps 617 and 618 , for meeting the difference-time Md.
  • Heating-time Mh applies if the user requirements lead to exceeding a maximum heat capacity, Ct ⁇ Ts, of the tank, so that cold water incoming to the tank requires heating.
  • the calculated heating-time (Mh) is stored in memory unit 105 .
  • the calculation of the heating time is based on the law of conservation of energy, and uses equation (9):
  • Vd is a volume of water to be heated, calculated below in equation (10),
  • ⁇ t is a difference in temperature, calculated below in equation (11), and
  • Pt is a power of heater 120 .
  • Vd The required volume of water that needs heating, Vd, is determined by comparing the amount of heating required to meet the difference-time Md with the amount of heating required to meet the maximum-time Mm.
  • Vd may be calculated by equation (10):
  • Vd Ct ⁇ Md Mm ( 10 )
  • ⁇ t is the difference between the set point temperature Ts and the cold water inlet temperature Tc, and is defined by equation 11:
  • processing unit 102 uses equation (12) to evaluate Mh.
  • processing unit 102 monitors the temperature of the water in the bottom of the tank, Tt, and when it is less than the set point temperature Ts, it activates the heater.
  • the heater is activated continuously or discontinuously, for a total time Mh as measured by R.T.C module 519 , according to the flow of water out of (and the corresponding flow of cold water into) tank 24 .
  • processing unit 102 stops the activation of the heater once heating-time Mh is achieved.
  • the processing unit then continues to display step 616 , described above, and then ends.
  • the above description of the flow chart assumes that flow sensor 130 is not present. Those having ordinary skill in the art will be able to adapt the description, mutatis mutandis, for embodiments where sensor 130 and flow rate module 517 are present.
  • the sensor provides, in real time, values to the processing unit of the flow rates from faucet 26 .
  • the processing unit may use these values to derive information useful to the user, and provide this information on display 34 .
  • the sensor also provides an indication to processing unit 102 that the flow rate is different from Fr.
  • Such a difference typically a reduction in flow rate from faucet 26 , typically leads to a different value for the (required) time Mr, the available time Ma, and the maximum time Mm.
  • example 2 the conditions of example 2 (presented above with reference to step 613 ) may apply, and the user may operate faucet 26 at a flow rate of Fr (2.5 gpm) for 9 minutes, then adjust the faucet so the flow rate is only 1.5 gpm.
  • display 34 may show a time period (length of time) for which water at temperature Tu is available. Initially this will be 33 minutes. After 9 minutes (determined by module 519 ) the available time is 24 minutes at 2.5 gpm, but the processing unit may calculate a new available time, based on the reduced measured flow of 1.5 gpm, equal to 40 minutes and show this time on display 34 .
  • FIGS. 5A , 5 B, and 6 are respectively first, second and third block diagrams illustrating the components of a water heating system 300 , according to an alternative embodiment of the present invention. Apart from the differences described below, the operation of system 300 is generally similar to that of system 20 ( FIGS. 1 , 2 A, 2 B, and 3 ), and elements indicated by the same reference numerals in both systems 20 and 300 are generally similar in construction and in operation.
  • memory 105 does not comprise required-temperature module 515 .
  • memory 105 comprises further modules, as listed below.
  • the modules may be implemented in software, hardware, or a combination of software and hardware.
  • system 300 there is no pump 128 , and there is no connecting pipe 128 between cold water inlet pipe 113 and outlet pipe 111 . There is no valve 129 in the cold water inlet pipe, although in some embodiments of system 300 valve 118 is present (with a different function, as explained below, from the function in system 20 ).
  • tank 24 in addition to heater 120 and its associated switch 124 , there are two more heaters 321 , 322 , with respective associated switches 325 , 326 . Heaters 321 , 322 , and switches 325 , 326 are typically similar in construction and function to heater 120 and switch 124 , described above. As shown in FIG. 5A , all heater switches are under control of processing unit 102 .
  • tank 24 has two extra temperature sensors 315 , 316 , respectively approximately level with heaters 321 , 322 .
  • the tank may optionally have a further temperature sensor 317 located close to the top of the tank. All sensors are typically generally the same in function and construction. Sensors 315 , 316 , and 317 are assumed to provide respective temperature measurement T 2 , T 3 , and T 4 .
  • FIG. 5A illustrates that all temperature sensors provide their temperature related signals to unit 102 .
  • heater 120 and sensor 114 are located close to the bottom of tank 24 .
  • heater 321 and sensor 315 are located approximately one third of the way up the tank, and heater 322 and sensor 316 are located approximately two thirds of the way up the tank.
  • the heaters are deployed in the tank in a heater vertical array, and the sensors are deployed in a sensor vertical array.
  • the heater vertical array and the sensor vertical array have substantially the same vertical distribution, i.e., the vertical location of the elements of the arrays are substantially the same, so that there are three heaters and three sensors which effectively divide the tank into three approximately equal volumetric sections V 1 , V 2 , and V 3 .
  • embodiments of the present invention provide a method for calculating and implementing respective required temperatures Tr 1 , Tr 2 , and Tr 3 of sections V 1 , V 2 , and V 3 .
  • embodiments of the present invention comprise other arrays of heaters and arrays of sensors, such as 2, 4, or more heaters and 2, 4, or more sensors. While typically there may be equal numbers of heaters and sensors, this is not a requirement for embodiments of the invention, and the numbers may be different. For example, there may be three heaters and four sensors, and values from the sensors may be interpolated to determine the temperatures of the strata defined by the heaters.
  • FIG. 7 is a flow chart describing steps that are implemented in operation of system 300 , according to an embodiment of the present invention. Except where otherwise indicated, the following description of the flow chart assumes an embodiment wherein flow sensor 130 and flow rate module 517 are not present and that the flow rate from faucet 26 is Fr, wherein valve 118 is not present, and wherein sensor 317 is not present.
  • a system installation step 900 is substantially the same as installation step 600 described above, except that there is no measurement of the time of operation, Po, of pump 127 .
  • a user step 901 and a cold water temperature measuring step 902 are substantially the same as respective steps 601 , 602 , described above, providing a user required temperature Tu and a cold water inlet temperature Tc, described above.
  • processing unit 102 samples signals from sensors 114 , 315 , 316 , and converts the signals to temperatures T 1 , T 2 , T 3 of respective sections V 1 , V 2 , and V 3 .
  • the sampling is typically performed in response to the start of operations of the user in step 901 , and may also be performed at other times, continuously or intermittently, during operation of system 20 .
  • the processing unit converts temperatures T 1 , T 2 , T 3 to respective effective temperatures T 1 e, T 2 e, T 3 e at the hot water inlet of faucet 26 , using the heat loss factor Lr, according to equation (13):
  • n 1, 2, or 3.
  • a first comparison 904 the processing unit compares the values of T 1 e, T 2 e, T3 e with Tu. If all of T 1 e, T 2 e, T 3 e are less than Tu, i.e., if T 1 e ⁇ Tu AND T 2 e ⁇ Tu AND T 3 e ⁇ Tu, the processing unit continues to a display step 909 . Otherwise, the processing unit continues to an average temperature step 905 .
  • the processing unit uses average-temperature module 711 to calculate an average effective temperature Ta of sections of tank 24 that have effective temperatures greater than Tu.
  • the average calculated is assumed to comprise an arithmetic mean. However, other averages, such as a geometric mean or a harmonic mean may be used.
  • T 3 e and T 2 e may both be greater than Tu, but T 1 e may be less than Tu.
  • the processing unit calculates Ta as
  • a hot water volume step 906 the processing unit uses currently-available-volume module 712 to calculate an available volume Ca of hot water, i.e., the volume of hot water in tank 24 that has an effective temperature greater than or equal to Tu.
  • Ca may be 1/3Ct, 2/3C t or Ct, according to whether only section V 3 , sections V 3 and V 2 , or all sections V 3 , V 2 , and V 1 have effective temperatures greater than or equal to Tu.
  • processing unit 102 uses the results from steps 905 and 906 to calculate a time period (length of time) Ma that mixed water at temperature Tu may be provided from faucet 26 .
  • Equation (14) which has the same structure as equation (6), applies:
  • Equation (14) rearranges to an equation (15) for Ma:
  • Step 906 calculates the available volume of water Ca as 2/3Ct, i.e., 50 gallons. Using these figures, equation (15) becomes:
  • display unit 34 shows the available time, Ma, that tank 24 can deliver water, so that the temperature at faucet 26 is Tu.
  • T 1 e, T 2 e, T 3 e are less than Tu
  • the processing unit continues to display step 909 .
  • processing unit 102 uses display 34 to ask if the user wants to heat the water in tank 24 . If the return from the second comparison is negative, i.e., the water is not to be heated in the tank, the process illustrated by the flow chart ends.
  • Step 911 is substantially the same as step 610 , so that the processing unit assumes that all the water in tank 24 is raised to the maximum set temperature Ts of the tank, and uses equation (4) to calculate Mm.
  • a user step 912 is substantially the same as user step 611 .
  • the user operates input device 32 to provide processing unit 102 with a length of time required, Mr, for mixed water at temperature Tu.
  • a third comparison 913 processing unit 102 compares Mr and Mm. (Comparison 913 is generally the same as comparison 612 .) If Mr ⁇ Mm the flow chart continues to a required temperature calculation step 914 . If Mr>Mm the flow chart continues to an activation step 918 .
  • step 914 the processing unit, using required-temperature module 715 , decides which heaters, 120 , 321 , and/or 322 are to be activated, and to what temperatures, as measured by sensors 114 , 315 , and 316 , sections V 1 , V 2 , and/or V 3 are to be raised.
  • the required temperatures of sections V 1 , V 2 , and V 3 are respectively termed Tr 1 , Tr 2 , and Tr 3 .
  • FIGS. 8A-8N illustrate a flow chart followed by processing unit 102 in implementing step 914 and an activation step 915 described below, according to an embodiment of the present invention.
  • the decisions are based on the processing unit analyzing the heat content of the water in the sections of the tank in a sequential manner, starting from an analysis of the top third of the tank, and applying the law of conservation of energy to determine to what temperature different sections of the tank are to be heated. If the processing unit determines that the top third of the tank is not able to meet the required Mr, the unit then analyzes the top two sections. Similarly, if processing unit 102 determines that the top two thirds of the tank are not able to meet the required Mr, the unit analyzes all three sections.
  • a comparison which is identified by a numeral without a letter suffix typically refers to a comparison made by the processing unit to evaluate if a given section of the tank is able to supply the needed value of Mr. If the comparison is valid, subsequent steps are identified by the comparison numeral with a letter appended.
  • unit 102 first calculates a value for Tr 3 in a step 802 A:
  • Tr ⁇ ⁇ 3 Mr ⁇ Fr ⁇ ( Tu - Tc ) + ( 1 / 3 ) ⁇ Ct ⁇ Tc ( 1 / 3 ) ⁇ Ct ⁇ Lr
  • Comparison 806 checks if the expression
  • Comparison 808 checks if the expression
  • step 810 A heater 322 is activated until Tr 3 ⁇ Tu/Lr and heater 321 is also activated until Tr 2 ⁇ Tu/Lr. If the expression of comparison 810 is not valid, unit 102 continues to a comparison 812 .
  • step 812 A heater 321 is activated until Tr 2 ⁇ Tu/Lr. If the comparison 812 is not valid, unit 102 continues to a comparison 814 .
  • unit 102 calculates a value for Tr 3 in a step 814 A:
  • Tr ⁇ ⁇ 2 , 3 Mr ⁇ Fr ⁇ ( Tu - Tc ) + ( 2 / 3 ) ⁇ Ct ⁇ Tc ( 1 / 3 ) ⁇ Ct ⁇ Lr .
  • Comparison 816 checks if the expression
  • Tr ⁇ ⁇ 3 Mr ⁇ Fr ⁇ ( Tu - Tc ) + ( 1 / 3 ) ⁇ Ct ⁇ Tc ( 1 / 3 ) ⁇ Ct ⁇ Lr ,
  • Tr 3 ⁇ T 3 ⁇ 2Tu/Lr ⁇ T 2 ⁇ T 1 is valid.
  • unit 102 calculates a value for Tr 3 in a step 818 A:
  • Tr ⁇ ⁇ 3 Mr ⁇ Fr ⁇ ( Tu - Tc ) + ( 1 / 3 ) ⁇ Ct ⁇ Tc ( 1 / 3 ) ⁇ Ct ⁇ Lr ,
  • a comparison 818 B the unit checks if Tr 3 ⁇ T 3 ⁇ Tu/Lr ⁇ T 1 is valid. If comparison 818 B is valid then in a step 818 C heater 322 is activated until Tr 3 is reached. If comparison 818 B is not valid, then unit 102 calculates the value of Tr 2 , 3 according to the value given above for step 814 D, and proceeds to a comparison 818 E. In comparison 818 E the processing unit checks if 2Tr 2 , 3 ⁇ T 3 ⁇ T 2 ⁇ Tu/Lr ⁇ T 1 is valid. If the comparison is valid, then in an activation step 818 F heaters 322 and 321 are activated until Tr 2 , 3 is reached. If comparison 818 E is invalid, then in an activation step 818 G heater 120 is activated until Tr 1 ⁇ Tu/Lr.
  • comparison 818 is invalid, processing unit 102 continues to a comparison 820 .
  • Comparison 820 checks if the expression
  • Comparison 820 D checks if 2Tr 2 , 3 ⁇ T 3 ⁇ T 2 ⁇ 3Tu/Lr ⁇ T 3 ⁇ T 2 ⁇ T 1 is valid. If the comparison is valid, then heaters 322 and 321 are activated until Tr 2 , 3 is reached. If the comparison is invalid, then heaters 322 , 321 , and 120 are activated until Tr 3 ⁇ Tu/Lr, Tr 2 ⁇ Tu/Lr, and Tr 1 ⁇ Tu/Lr.
  • comparison 820 is invalid, processing unit 102 continues to a comparison 822 .
  • Comparison 822 D checks if 2Tr 2 , 3 ⁇ T 3 ⁇ T 2 ⁇ 2Tu/Lr ⁇ T 2 ⁇ T 1 is valid. If the comparison is valid, then in an activation step 822 E heaters 322 and 321 are activated until Tr 2 , 3 is reached. If the comparison is invalid, then in an activation step 822 F heaters 321 and 120 are activated until Tr 2 ⁇ Tu/Lr and Tr 1 ⁇ Tu/Lr.
  • comparison 822 is invalid, processing unit 102 continues to a comparison 824 .
  • Comparison 824 checks if the expression
  • Comparison 824 D checks if 2Tr 2 , 3 ⁇ T 3 ⁇ T 2 ⁇ Tu/Lr ⁇ T 1 is valid. If the comparison is valid, then in an activation step 824 E heaters 322 and 321 are activated until Tr 2 , 3 is reached. If the comparison is invalid, then in an activation step 824 F heater 120 is activated until Tr 1 ⁇ Tu/Lr.
  • comparison 824 is invalid, processing unit 102 continues to a comparison 826 .
  • Comparison 826 checks if the expression
  • step 826 A the processing unit calculates Tr 2 , 3 according to the expression given above for step 814 D, and proceeds to a comparison 826 B.
  • Comparison 826 B checks if 2Tr 2 , 3 ⁇ T 3 ⁇ T 2 ⁇ 3Tu/Lr ⁇ T 3 ⁇ T 2 ⁇ T 1 is valid. If the comparison is valid, then in an activation step 826 C heaters 322 and 321 are activated until Tr 2 , 3 is reached. If the comparison is invalid, then in an activation step 826 D heaters 322 , 321 , and 120 are activated until Tr 3 ⁇ Tu/Lr, Tr 2 ⁇ Tu/Lr, and Tr 1 ⁇ Tu/Lr.
  • comparison 826 is invalid, processing unit 102 continues to a comparison 828 .
  • Comparison 828 checks if the expression
  • step 828 A the processing unit calculates Tr 2 , 3 according to the expression given above for step 814 D, and proceeds to a comparison 828 B.
  • Comparison 828 B checks if 2Tr 2 , 3 ⁇ T 3 ⁇ T 2 ⁇ 2Tu/Lr ⁇ T 2 ⁇ T 1 is valid. If the comparison is valid, then in an activation step 828 C heaters 322 and 321 are activated until Tr 2 , 3 is reached. If the comparison is invalid, then in an activation step 828 D heaters 321 and 120 are activated until Tr 2 ⁇ Tu/Lr and Tr 1 ⁇ Tu/Lr.
  • comparison 828 is invalid, processing unit 102 continues to a comparison 830 .
  • Comparison 830 checks if the expression
  • step 830 A the processing unit calculates Tr 2 , 3 according to the expression given above for step 814 D, and proceeds to a comparison 830 B.
  • Comparison 830 B checks if 2Tr 2 , 3 ⁇ T 3 ⁇ T 2 ⁇ 2Tu/Lr ⁇ T 1 is valid. If the comparison is valid, then in an activation step 830 C heaters 322 and 321 are activated until Tr 2 , 3 is reached. If the comparison is invalid, then in an activation step 830 D heater 120 is activated until Tr 1 ⁇ Tu/Lr.
  • comparison 830 is invalid, processing unit 102 continues to a comparison 832 .
  • Comparison 832 checks if the expression
  • comparison 832 is invalid, processing unit 102 continues to a comparison 834 .
  • Comparison 834 checks if the expression
  • comparison 834 is not valid, the processing unit continues to a comparison 836 .
  • Comparison 836 checks if the expression
  • comparison 836 is not valid, the processing unit continues to a comparison 838 .
  • Comparison 838 checks if the expression
  • Comparison 840 checks if the expression
  • Comparison 842 checks if the expression
  • Comparison 844 checks if (Mm>Mr>Ct/Fr). If the comparison is valid, then in a step 844 A the processing unit calculates an average temperature Tr to which all three sections of the tank may be raised.
  • the average temperature for all three sections is also herein referred to as Avg.(Tr 1 , Tr 2 , Tr 3 ), but should not be confused as being determined by taking the average of the temperatures sampled by the temperature sensors.
  • a Tr is given by:
  • a comparison 844 B the processing unit checks if the comparison (T 3 ⁇ Tr and T 2 ⁇ Tr and T 1 ⁇ Tr) is valid. If it is, then in an activation step 844 C heaters 322 , 321 , and 120 are activated until T 3 ⁇ Tr, T 2 ⁇ Tr, and T 1 ⁇ Tr. If comparison 844 B is invalid, unit 102 proceeds to a comparison 844 D: (T 3 >Tr and T 2 ⁇ Tr and T 1 ⁇ Tr).
  • step 844 E the processing unit calculates an average temperature for the lower two sections of the tank in a step 844 E.
  • the average temperature for the lower two sections is also referred to as Avg.(Tr 1 , Tr 2 ), and should not be confused as being determined from the average of the temperatures sampled by the lower two sensors.
  • Avg.(Tr 1 , Tr 2 ) is calculated according to the expression:
  • Tr ⁇ ⁇ 1 , Tr ⁇ ⁇ 2 Tr - T ⁇ ⁇ 3 - Tr 2 ,
  • Tr is as calculated in step 844 A.
  • unit 102 checks in a comparison 844 F if Avg.(Tr 1 , Tr 2 )>T 2 . If the comparison is valid, then in an activation step 844 G unit 102 activates heater 321 until T 2 ⁇ Avg.(Tr 1 , Tr 2 ), and activates heater 120 until T 1 ⁇ Avg.(Tr 1 , Tr 2 ). If comparison 844 F is not valid, then in an activation step 844 H unit 102 activates heater 120 until T 1 ⁇ 2 Avg.(Tr 1 , Tr 2 ) ⁇ T 2 .
  • unit 102 may operate valve 118 to prevent water from exiting the tank.
  • flow sensor 130 and flow rate module 517 are present in system 300 . If so, the sensor and module function substantially as described above for system 20 , enabling, for example, a real time display of a period for which water at temperature Tu is available.
  • step 915 heaters 120 , 321 , and/or 322 are activated as determined in the flow chart of FIGS. 8A-8N .
  • a deactivation step 916 when the conditions determined in the flow chart of FIGS. 8A-8N have been met, heaters that have been activated in step 915 are deactivated.
  • a display step 917 once the temperatures determined in step 914 have been reached, display 34 indicates to the user that the water in tank 24 has been sufficiently heated to satisfy the user's requirements, i.e., that there is sufficient hot water for faucet 26 to supply water to the user at temperature Te (Tu ⁇ Lr) for a required time Mr.
  • the flow chart then ends.
  • steps 918 , 919 , 920 , 921 , 922 , 923 and 924 are generally similar respectively to steps 617 , 618 , 619 , 620 , 621 , 622 , and 623 ( FIG. 4 ).
  • step 918 depending on the difference between Mr and Mm, one or more of heaters 120 , 321 , and 322 are activated.
  • steps 923 and 924 depending on the value of Mh (determined in step 922 ) heaters 120 , 321 , and/or 322 are activated and deactivated according to whether T 1 ⁇ Ts and/or T 2 ⁇ Ts and/or T 3 ⁇ Ts.
  • the embodiments described above have considered one user using a water supply system.
  • the water supply system may be configured, mutatis mutandis, to be used by two or more users, where there is a common time period wherein the two or more users use the system simultaneously.
  • such a configuration typically requires replication of shower 22 , and elements within the shower comprising faucet 26 , control unit 30 , data input device 32 , data output device 34 , and incorporation of flow sensor 130 .
  • the multiple control units are configured to communicate with each other.
  • items of the water supply system are differentiated by appending a letter to the identifying numeral of the item, for example, shower 22 A, shower 22 B, . . . .
  • a user A may at 9 a.m. require a supply of water at 105° F. for 20 minutes in a shower 22 A
  • a user B may at 9:10 a.m. require a supply of water at 98° F. for 15 minutes in a shower 22 B.
  • Both users input their requirements into their respective control units 30 A, 30 B, and begin to use their faucets 26 A, 26 B so as to receive hot water simultaneously from 9:10 a.m.
  • respective control units 30 A and 30 B communicate between themselves, and with sensors 130 A and 130 B, in order to determine requirements of user A, user B, and amounts of water that have been used by each user. From the determinations, the control units are able to perform substantially the same processes described above with respect to the flow chart of FIG. 7 .
  • a single control unit 30 S having a functionality generally similar to control unit 30 , may be coupled to a group of showers 22 A, 22 B, . . . , and single control unit 30 S may be typically further configured to be accessible to users A, B, . . . .
  • the requirements of each user may be entered into the single control unit, typically, but not necessarily, by the users themselves operating the unit.
  • Control unit 30 S may be configured to accept differentiating identifying data, that differentiates between the requirements of the different users, that is entered into the control unit via a data input device 32 S.
  • the differentiating identifying data typically comprises an identifier of respective users A, B, . . . , and/or an identifier of respective showers 22 A, 22 B, . . . . From the requirements, control unit 30 S is able to perform substantially the same processes described above with respect to the flow chart of FIG. 7 .
  • system 20 may be configured to operate with multiple communicating control units, or with a single control unit that differentiates between requirements of different users.
  • the one or more control units operating the reconfigured system are typically configured to mix the water in hot water tank 24 , using pump 127 , when a first user starts to operate the reconfigured system, and not to mix the water until the first user's requirements have been met.
  • the one or more control units add the new requirements to those already input for the first user, without further mixing of the water in tank 24 .
  • the one or more control units determine whether or not the new requirements can be met from the water in tank 24 , and provide corresponding outputs to the one or more second users.
  • the outputs provided typically comprise respective available times for the one or more second users, or that a given requirement cannot be met.
  • the one or more control units may be configured to calculate a required heating time, using a method generally similar to that described above with reference to equations (9) and (12), and display such a time to users whose requirements cannot be met.

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CN102498350A (zh) 2012-06-13
IL218264A (en) 2015-08-31
IL218264A0 (en) 2012-04-30

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