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1. (WO2018162731) A DOMESTIC HOT WATER INSTALLATION
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Title of Invention:

"A domestic hot water installation"

Technical Field:

This invention relates to a domestic hot water installation. More specifically, this invention relates to a domestic hot water installation with a hot water cylinder, an external heating circuit and a controller.

Background Art:

Domestic hot water installations are used to provide the hot water requirements for taps, showers and baths in a household. Generally speaking, the domestic hot water installations comprise a hot water cylinder, one or more heating coils to heat the hot water in the hot water cylinder, and a controller to operate the one or more heating coils. Although simple to operate, there are problems with the known hot water installations. Perhaps most importantly, the known hot water installations are notoriously inefficient to operate. This is due in part to the fact that it is very difficult for an operator of the hot water installation to gauge at any given moment in time, the precise volume of hot water available for use in the hot water cylinder. As a consequence, in order to ensure that there is sufficient hot water available for use, the operator of the domestic hot water installation will typically operate the heating coil for far in excess of the time that is necessary to provide the required amount of water. This will ensure that they don't run out of hot water mid-way through a shower. However, it also represents a substantial waste of resources and increases the cost of operating the domestic hot water installation.

Various devices have been proposed to address some of this waste. For example, it is known for various domestic hot water installations to have, in addition to an on/off switch connected to their immersion, a shower/bath switch connected to the immersion. In addition to turning the immersion on, the operator selects either a bath or a shower and the immersion coil is operated to provide enough hot water for a shower or a bath. However, the volume of water is fixed by the manufacturer and what is sufficient for a

normal shower will be inadequate for a power shower. Furthermore, the electric immersion heater may still be left on for well in excess of the amount of time necessary as there is nothing to indicate, other than past experience using trial and error, whether or not enough water will have been heated to the correct temperature.

Japanese Patent Application Publication No. JPS6082744A in the name of Matsushita discloses a hot water tank that may be heated overnight with a display for displaying the quantity of remaining hot water in the tank. US Patent Application Publication No. US2016/0258635 in the name of Zemach discloses an interactive learning water heating scheduler with a display for displaying the quantity of remaining hot water. Although each has their own place and market, it is believed that neither of these devices allows the operator to control an external heating circuit in a sufficiently measured way to deliver a desired volume of hot water and it is understood that the known devices may result in superfluous operation of heating elements by the operator to ensure that they have sufficient hot water for their needs. Furthermore, none of the devices allows the operator to accurately order a discrete volume of water required by the operator.

It is an object of the present invention to provide a domestic hot water installation that overcomes at least some of the problems with the known domestic hot water installations and that provides a useful alternative choice to the consumer.

Summary of Invention:

According to the invention there is provided a domestic hot water installation comprising:

a hot water cylinder;

an external heating circuit;

a controller comprising a processor, an accessible memory for storage of a domestic hot water profile, and control means to operate the external heating circuit in accordance with the domestic hot water profile;

means to measure the volume of hot water delivered into the hot water cylinder; means to measure the volume of hot water drawn from the hot water cylinder;

the controller, in communication with the means to measure the volume of hot water being delivered into the hot water cylinder and the means to measure the volume of hot water drawn from the hot water cylinder, having means to determine the current volume of available hot water in the hot water cylinder; and

the controller having a graphical user interface (GUI) having displayed thereon the current volume of available hot water in the hot water cylinder.

By having such a domestic hot water installation, the operator of the domestic hot water installation will know with a reasonable degree of accuracy the amount of hot water available to them in the cylinder at a given moment in time. In this way, once an adequate amount of water has been provided for their needs, it will not be necessary to continue to operate the heating circuit and waste resources unnecessarily. The operator can ensure that the external heating circuit is turned off once adequate water is available to them and this will reduce the cost of operation of the domestic hot water installation.

In one embodiment of the invention there is provided a domestic hot water installation in which the controller has stored in accessible memory the volume of water required for at least one of a shower and a bath and the GUI comprises an indicator of whether the current volume of available hot water is equal to or greater than the volume of water required for a shower and or a bath. In this way, the operator will know in an intuitive way whether or not there is sufficient water at their disposal to carry out a desired act. For example, if the operator wishes to know if there is enough water available for them to have a shower, all they have to do is look at the GUI which will display this information to them. This will prevent the operator from operating the heating circuit unnecessarily or carrying out the desired act of taking a shower when there is inadequate hot water in the hot water cylinder for them to do so.

In one embodiment of the invention there is provided a domestic hot water installation in which the GUI has an indicator of whether the current volume of available hot water is equal to or greater than an integer multiple of the volume of water required for a shower and or a bath. Again, this will be useful as the operator will know if multiple showers are required (for example for a family or a number of co-habitants) whether or not there is sufficient water for their needs.

In one embodiment of the invention there is provided a domestic hot water installation in which the indicator comprises a pictogram of a shower and or a bath. This is seen as a simply way of illustrating, in an intuitive way to the operator, whether or not there is sufficient water for their purposes.

In one embodiment of the invention there is provided a domestic hot water installation in which the indicator comprises a numerical value. A numerical value may be used in addition to or instead of the pictogram and is also seen as a useful way to indicate to the operator whether or not there is sufficient water at their disposal.

In one embodiment of the invention there is provided a domestic hot water installation in which the accessible memory is programmable and the volume of water required for a shower and or a bath stored in memory is programmable by a domestic hot water installation user. This is seen as a particularly preferred embodiment of the present invention. By having the volume of water required for a shower or a bath programmable by the user, installations with different configurations and different personal preferences can be taken into account. This will ensure that adequate hot water is supplied and that there is not needless waste in an installation. For example, one installation may have a standard shower and another installation may have a power shower. The installation with the power shower will use more hot water for a shower of the same duration. Similarly, one user may spend five minutes showering whereas another user may spend ten minutes showering. By having an installation as described, the amount of water suitable for the individual user and installation can be provided and the user will know when there is adequate hot water for their specific requirements. In order to know the desired volume of water required for a shower or bath initially, the operator may order a full tank of hot water. They may then run the shower or the bath and see, on the controller, how much hot water is remaining in the tank after they have run the shower or the bath. From this, they will be able to tell the amount of water used and they can use this as the amount required for a bath or shower, as appropriate, in the future.

In one embodiment of the invention there is provided a domestic hot water installation in which the GUI has displayed thereon the volume of water used the previous time that there was a draw of water from the hot water cylinder. This is seen as a useful aspect of the present invention that will enable the user to regulate the hot water installation to provide the correct amount of hot water. The user may, for example, believe that they need 50 litres of water for their shower in the morning before work. However, over time, the user may notice from inspection of the GUI that they only use on average 35-40 litres of hot water each morning for their morning shower, thereby wasting 10-15 litres of hot water unnecessarily each morning. The user may thereafter change their profile so that the amount of water heated for the shower is set to 40 litres, thereby reducing waste and cost of operation of the installation.

In one embodiment of the invention there is provided a domestic hot water installation in which the GUI has a selectable icon representative of a first fixed volume of water that if selected by a user, will cause the controller to operate the external heating circuit to provide that first fixed volume of water in the hot water cylinder. This is seen as a particularly simple configuration of hot water installation. In this way, the operator of the hot water installation may "press" a certain icon and the desired amount of water will be provided to them. For example, the icon may be representative of a volume of water necessary to take a shower (i.e. 50 litres). If the user wishes to take a shower, rather than turning on the heating circuit for an arbitrary period of time based on their experience, they may simply press the icon and external heating circuit will be operated until the fixed amount of water is provided in the hot water cylinder.

In one embodiment of the invention there is provided a domestic hot water installation in which the GUI has a second selectable icon representative of a second fixed volume of water that if selected by a user, will cause the controller to operate the external heating circuit to provide that second fixed volume of water in the hot water cylinder. In this way, there may be a separate icon for a bath and a shower or for a quick shower and a long shower. Similarly, more than two selectable icons could be provided.

In one embodiment of the invention there is provided a domestic hot water installation in which on the first or second selectable icon being selected multiple times, this will cause the controller to operate the external heating circuit to provide the first or second fixed volume of water that multiple number of times. In this way, if the operator wishes to provide sufficient hot water in the household so that each of the occupants can have a shower, they may do so. For example, there may be three adults sharing a house, all of which require hot water for a shower in the morning before they go to work. The operator may select three showers by "depressing" the shower icon three times. This may be done in advance and the record stored in memory to be repeated at a given time each day, i.e. to ensure that there is sufficient hot water for three showers at 7am each morning.

In one embodiment of the invention there is provided a domestic hot water installation in which the GUI has a selectable icon to cancel the ordered volume of water.

In one embodiment of the invention there is provided a domestic hot water installation in which the first fixed volume of water and the second fixed volume of water are programmable in accessible memory. This is seen as a particularly preferred embodiment of the invention. By allowing the first and second volume of water to be programmable in accessible memory, the volume of water can be determined based on the users requirements and the configuration of the installation. This will lead to a more effective and efficient use of the resources available in the household and will avoid u n n ecessa ry waste .

In one embodiment of the invention there is provided a domestic hot water installation in which the GUI has a graphical representation of a hot water cylinder and in which the controller indicates on the graphical representation of the hot water cylinder the volume of hot water in the hot water cylinder. This is seen as a useful intuitive way for the user to know how much hot water is available to them at a given moment in time.

In one embodiment of the invention there is provided a domestic hot water installation in which the GUI has a timer clock indicative of the amount of time left required to operate the external heating circuit to provide the volume of water required for a shower or a bath. Once the boiler or other external heating circuit is up to speed, the amount of time that it takes to heat water in the external heating circuit for the hot water cylinder will be known with a reasonable degree of accuracy. From this, the amount of time left to provide the required amount of water will be known and this can be displayed to the

operator so that they know when they will be in a position to take their shower or bath in comfort.

In one embodiment of the invention there is provided a domestic hot water installation in which the GUI has a timer clock indicative of the amount of time left required to operate the external heating circuit to provide the volume of water ordered by a domestic hot water installation user.

In one embodiment of the invention there is provided a domestic hot water installation in which there is provided a hot water loss profile constant stored in memory, and in which there is provided:

means to measure the volume of hot water lost from the hot water cylinder over time; and

the controller, in communication with the means to measure the volume of hot water lost from the hot water cylinder over time, having means to determine the current volume of available hot water in the hot water cylinder.

In this way, the amount of hot water that is lost due to heat loss will also be known. This is advantageous because if the hot water ordered from a previous session is not used in its entirety, it will remain in the hot water cylinder and cool over time. If by the time the user wishes to have another shower there is still some hot water in the cylinder, less hot water will have to be heated up for their needs in the current session due to the amount that is left over from the previous session. Similarly, if there is a gap in the time that the user uses an ordered amount of hot water, the natural heat loss may mean that there is insufficient hot water for their requirements and the external heating circuit will be operated in order to "top-up" the amount of hot water in the hot water cylinder.

Brief Description of the Drawings:

The invention will now be more clearly understood from the following description of some embodiments thereof given by way of example only with reference to the accompanying drawings, in which:-

Figure 1 is a diagrammatic representation of a hot water installation according to the invention;

Figure 2 is a diagrammatic representation of an alternative hot water installation according to the invention; and

Figures 3 to 8 are views of a graphical user interface used in the hot water installation according to the invention.

Detailed Description of the Drawings:

Referring to Figure 1 , there is shown a domestic hot water installation according to the invention, indicated generally by the reference numeral 1 , comprising a hot water cylinder 3, an external heating circuit 5 comprising a boiler 7 and a heat exchanger 9, and a network of pipes 1 1 (a)-1 1 (d) connecting the hot water cylinder 3 to the heat exchanger 9 and the boiler 7 to the heat exchanger 9. The boiler 7 is connected to the primary side 13 of the heat exchanger 9 and the hot water cylinder is connected to the secondary side 15 of the heat exchanger.

A first pump 17 is provided to deliver heating fluid from the boiler 7 along a flow pipe 1 1 (c) to a flow port 19 of the primary side 13 of the heat exchanger 9. The heating fluid passes through the primary side 13 of the heat exchanger before exiting through a return port 21 of the primary side of the heat exchanger, along the return pipe 1 1 (d) and back to the boiler 7. The first pump 17 is a variable speed pump.

A second pump 23 is provided to deliver water from a point adjacent the base of the hot water cylinder 3 along a flow pipe 1 1 (a) to a flow port 25 of the secondary side 15 of the heat exchanger 9. The water passes through the secondary side 15 of the heat exchanger before exiting through a return port 27 of the secondary side of the heat exchanger, along a return pipe 1 1 (b) and back to the hot water cylinder 3 to a point adjacent the top of the hot water cylinder. The second pump 23 is also a variable speed pump.

In the embodiment shown, there are provided three temperature sensors including a first temperature sensor 29 located adjacent the flow port 25 of the secondary side of the heat exchanger, a second temperature sensor 31 located adjacent to the return port 27 of the secondary side of the heat exchanger and a third temperature sensor 33 located adjacent to the flow port 19 of the primary side of the heat exchanger. The first temperature sensor 29 could be located anywhere along the pipework 1 1 (a), the second temperature sensor 31 could be located anywhere along the pipework 1 1 (b) and the third temperature sensor 33 could be located remote from the heat exchanger along the pipework 1 1 (c). There is provided a temperature and flow sensor 34 located on a hot water outlet pipe 45 that is used to deliver hot water from the cylinder to one or more outlets in the household. The temperature and flow sensor 34 is operable to detect both the temperature and the volume of hot water flowing out of the hot water cylinder.

In addition to the foregoing, there is provided a controller 35 in communication with each of the first pump 17, the second pump 23, the three temperature sensors 29, 31 , 33, the temperature and flow sensor 34 and the boiler 7. The communication links between the controller 35 and the pumps 17, 23, the boiler 7, the temperature and flow sensor 34 and the temperature sensors 29, 31 , 33, are illustrated by way of dashed lines 37(a)-37(g). The temperature sensors 29, 31 , 33 and the temperature and flow sensor 34 communicate the temperature of the fluid or water passing thereby back to the controller 35 over communication links 37(c), 37(d), 37(e) and 37(g) and the controller sends control instructions to operate the pumps 17, 23 over communication links 37(a), 37(b) and control instructions to the boiler 7 over communication link 37(f). The communication links 37(a)-37(g) could be provided by wired and/or wireless links. The controller 35 comprises a processor 39 for processing the data received from the temperature sensors and the temperature and flow sensor, an accessible memory 41 for storage of a domestic hot water installation operating program/hot water profile, and means 43 to operate the first and second pumps 17, 23 and the boiler 7 in accordance with the domestic hot water installation operating program.

In use, in order to heat water in the heating circuit and provide the heated water to the hot water cylinder, pump 23 is initially turned off. The boiler 7 and pump 17 is turned on and the temperature of the heating fluid from the boiler is monitored by temperature sensor 33. Once the temperature of the heating fluid from the boiler 7 gets "up to

temperature", typically in the region of 60-70°C or above, the second pump, 23 is turned on while the first pump 17 circulates heating fluid through the primary side 13 of the heat exchanger and the second pump 23 circulates water from the hot water cylinder 3 through the secondary side 15 of the heat exchanger. The heating fluid circulating in the primary side 13 of the heat exchanger heats the water in the secondary side 15 of the heat exchanger and the heated water in the secondary side 15 returns to the hot water cylinder 3.

The speed of the pump 23 is controlled to ensure that the water remains in the secondary side 13 for a period of time sufficient to heat the water to the desired set temperature, which may, for example, be of the order of 60°C. In this way, cooler water is gradually fed from the bottom of the hot water cylinder through the heat exchanger where it is heated and then returned to the top of the hot water cylinder from where it may be drawn through pipework 45 for use in a shower, bath, sink or the like. Advantageously, the temperature of the water entering and exiting the secondary side 15 of the heat exchanger is known and the temperature of the heating fluid is known. This allows for a very accurate and controlled method of heating the hot water and delivering water at a known temperature to the hot water cylinder. The speed of the pump 17 may also be regulated to ensure that the heating fluid does not remain in the heat exchanger for too long, which may result in too great a drop in the temperature of the heating fluid before it is returned to the boiler. If the temperature of the returning heating fluid is too low, this may lead to decreased boiler efficiency and the the creation of sulphurous acid and or other harmful corrosive agents in the flue gases of an oil boiler which can damage the boiler and the flue exhaust. If desired, a further temperature sensor in communication with the controller 35 may be provided at the return port 21 of the primary side of the heat exchanger to monitor the temperature of the heating fluid returning to the boiler and the controller may operate the pump 17 according, in part, to the output of this additional temperature sensor.

The controller 35 operates the pump 23 in accordance with a domestic hot water profile. For example, the domestic hot water profile may call for 50 litres of water at approximately 60°C for a shower. The controller 35 will operate the pump 23 to provide 50 litres of water at 60°C before shutting the pump 23 off. The controller 35 will know the precise amount of hot water delivered into the tank from the manner in which it has

operated the pump 23 however if desired, a dedicated flow meter (not shown) on the return pipe 1 1 (b) returning the hot water to the hot water cylinder could be provided. If a dedicated flow meter were provided, this flow meter would be in communication with the controller to indicate to the controller the volume of hot water that has been delivered into the hot water cylinder. Due to the stratification of water in the hot water cylinder, there will effectively be a cool layer at the bottom of the tank and a hot layer of 50 litres of hot water at 60°C at the top of the tank (there will in fact be a boundary layer of mixed temperature water therebetween but for the purposes of this specification, we will describe the invention as though there is an abrupt differentiation between the two layers). As hot water is drawn out of the tank along pipe 45 to the shower, the water is replaced in the hot water cylinder by cold water entering in through inlet pipe 47 at the bottom of the hot water cylinder. When all the hot water at 60°C has been drained from the hot water cylinder, there will only be cold water left in the tank which will be drawn once the hot water has been drained.

In use, a hot water loss profile constant may be set by the operator (it may also have been preset in a factory mode setting) based on the configuration of the hot water cylinder and or the domestic hot water installation. The hot water loss profile constant will form part of the hot water loss profile that the controller will use to determine the amount of hot water in the cylinder at a given time. For example, the hot water loss constant may indicate that the hot water cylinder will lose 2 litres of hot water per hour. After the boiler 7 and the pumps 17, 23 have been operated to fill the hot water cylinder with a predetermined amount of water, for example, 50 liters, the controller will know that at that moment in time, there is 50 litres of hot water at 60°C in the hot water cylinder. The controller will periodically calculate the temperature and volume of water in the hot water cylinder. If the water is left to cool in the hot water cylinder for an hour, the controller will calculate that there is 48 litres of hot water remaining. If the water is left to cool for three hours, the controller will calculate that there is 44 litres of hot water remaining in the hot water cylinder 3. If the controller detects that a person has started to draw water from the hot water cylinder, the controller will turn the boiler 7 and pumps 17, 23 on to provide sufficient water to bring the volume of hot water back up to 50 litres originally ordered.

As water is drawn from the hot water cylinder, the temperature and flow sensor 34 will be able to measure the actual temperature of the water being drawn from the hot water cylinder and the amount of water that is being drawn from the hot water cylinder. In this way, the controller will know with a good degree of certainty the amount of hot water available in the hot water cylinder.

According to one embodiment of the invention, the controller can use information from past measurements to refine the calculations. For example, the controller may determine that during the summer months, when the ambient temperature is higher, the losses are lower and the hot water loss profile should in fact be closer to 1.5 litres per hour. Similarly, during the winter months, when the ambient temperatures are lower, the losses are higher and the hot water loss profile should in fact be closer to 2.5 litres per hour. The controller can use this information to refine the amount of water that it calculates is still in the hot water cylinder and can use the information to determine how long the pumps and the boiler will have to be run to top up the hot water cylinder.

It is envisaged that the controller could have a temperature sensor to gauge the ambient temperature or indeed the temperature sensor may use the temperature of the water passing into the heat exchanger from the hot water cylinder through port 25 or the temperature of the water passing into the hot water cylinder through pipe 47 (using an additional temperature sensor not illustrated in the drawings) to provide an indication of the ambient temperature. Furthermore, the information of the temperature of the water passing into the heat exchanger from the hot water cylinder may be useful as it can have a bearing on the heat loss profile of the hot water cylinder. For example, if the cold water in the hot water cylinder is at 10°C, this will cool the hot water above it in the cylinder faster than if there was cool water at 20°C in the hot water cylinder. This information can be used to accurately predict the amount of hot water remaining in the hot water cylinder. Importantly, if desired, the controller can iteratively improve the monitoring and calculation of the amount of hot water available in the hot water cylinder through past measurements.

It will be understood that the configuration of external heating circuit is not intended necessarily to be limiting unless otherwise specified in the claims and other configurations of external heating circuits may be provided to good effect. For example, a heat pump may be used instead of the boiler 7. If a heat pump is used, the heat pump will be provided with a pump capable of being operated to perform the duties of the pump 17 and the pump 17 could be omitted or considered to be provided by way of the pump in the heat pump.

Referring to Figure 2, there is shown an alternative configuration of domestic hot water installation, indicated generally by the reference numeral 101 , where like parts have been given the same reference numeral as before. The domestic hot water installation 101 differs from the installation 1 in that there is provided an alternative external heating circuit 103 that may be used to perform the method according to the invention. The external heating circuit comprises an electrical heater, such as a Willis-type heater having a flow port 25 and a return port 27. Water enters the flow port and is heated by an electrical element before passing out the return port and returning to the hot water cylinder. The amount of hot water and the temperature of the hot water transferred back to the hot water cylinder will be controlled in main part by the controller 35, the pump 23 and the temperature sensor 31. The controller 35 is capable of operating the heater 103.

Referring now to Figures 3 to 8 inclusive, there are shown a number of diagrammatic representations of the graphical user interface of the controller 35 according to the invention, indicated generally by the reference numeral 300. Referring first of all to Figure 3, the graphical user interface comprises a screen 301 and a plurality of buttons including a toggle button 303, an up button 305 and a down button 307. The configuration of the buttons and the screen including their relative positioning is not intended to be limiting and is shown for illustrative purposes only. The screen is divided into two distinct sections 301 (a) and 301 (b). In section 301 (a), the amount of available hot water currently stored in the cylinder is shown along with the time remaining in order to provide the desired amount of water into the hot water cylinder. In this case, the amount of water ordered was 50 litres, the amount set by the operator to provide a shower. Accordingly, the time shown remaining on the counter is zero. In section 301 (b), there is shown a pictogram 309 of a shower and a pictogram 31 1 of a bath. The user will have set in advance the volume of water required to provide a shower (e.g. 50 litres) and a bath (e.g. 100 litres) in their installation. Beside each of the pictograms 309, 31 1 is an indication of the number of showers and/or baths that can be provided with the current volume of hot water. It can be seen that there is a "X1 " beside the shower symbol

indicating that there is sufficient hot water to provide a shower in the hot water installation and an "X0" beside the bath symbol indicating that there is insufficient water to provide a bath.

Referring specifically to Figure 4, there is shown an alternative configuration of the GUI, indicated generally by the reference numeral 400 and where like parts have been given the same reference numeral as before. It will be understood that the volume of water available in the hot water cylinder, as illustrated in panel 301 (a) is now at 100 litres. Accordingly, in panel 301 (b), there is a "X2" beside the shower pictogram 309 and a "X1 " beside the bath pictogram 31 1 , indicating that there is sufficient water in the hot water cylinder for two showers or for one bath.

Referring now to Figure 5, there is shown an alternative configuration of the GUI, indicated generally by the reference numeral 500 and where like parts have been given the same reference numeral as before. In Figure 5, there is shown a diagrammatic representation of the GUI before there is sufficient water for either a bath or a shower. It will be seen that in panel 301 (a), the available volume is set to 35 litres. If the amount of water required for a shower is set to 50 litres, there is still 15 litres required before there is sufficient hot water in the hot water tank. Assuming that the external heating circuit is able to provide 5 litres of hot water per minute at the desired temperature of 60°C, the time remaining will show "3:00" indicating that there will be sufficient hot water in three minutes time. It can be seen that in panel 301 (a), there is an "X0" beside both the shower pictogram and the bath pictogram 31 1.

Referring now to Figure 6, there is shown an alternative screen of the GUI, indicated generally by the reference numeral 600, where like parts have been given the same reference numeral as before. In screen panel 301 (a) there is now provided the ordered volume (i.e. 150 litres), the current available volume (i.e. 105 litres) and the time remaining to provide that volume (i.e. 4 minutes 30 seconds assuming a rate of 10 litres of hot water being provided per minute). In panel 301 (b), there is shown a graphical representation of the hot water cylinder. Importantly, the GUI can also show the volume ordered numerically, (i.e. 150 litres), the remaining amount to be delivered (i.e. 45litres, not shown) and the delivered amount (i.e. 105 litres). The delivered amount may be shown in red on the pictorial representation of the cylinder in panel 301 (b) while at the same time the remaining amount to be delivered may be shown in yellow with the spare capacity shown in green. Other colours or indeed shading schemes could be provided to differentiate between the three amounts on the GUI. In panel 301 (b) as shown, the capacity of the hot water cylinder is divided into discrete segments and the segments are used to represent the volume of hot water in the cylinder. Each of the shaded segments represents 25 litres of hot water in the cylinder. Once another 20 litres of hot water is added to the hot water cylinder, a further segment will be shown shaded. In the embodiment shown, the graphical representation of the cylinder is shown heating from the top down in the same manner that a hot water cylinder is heated using an external heating circuit. However, this may be counter-intuitive for the user and the graphical representation of the cylinder could be shown being heated from the bottom up for ease of understanding.

Referring now to Figure 7, there is shown an alternative screen of the GUI, indicated generally by the reference numeral 700, where like parts have been given the same reference numeral as before. This is a configuration screen for the operator of the domestic hot water installation. The screen 301 presents six different configurable options for the user and each option will lead to a further screen with one or more configurable options. The six options shown are the set temperature 701 , the set volume 1 703, the set volume 2 705, the program schedule 707, the set loss constant 709 and the set clock 71 1. The list of options may be scrolled through using the up and down arrows 305, 307 and selected using the toggle button 303. It is envisaged that the currently selected option will be highlighted or an indicator will be provided beside the currently selected option. Alternatively, a pointer device or a touch screen may be provided.

If option 701 is selected, the user will have the option of setting the hot water temperature provided by the controller and the heating circuit. For example, the operator may choose that they wish the water to remain in the secondary side of the heat exchanger until the water temperature is at 60°C. If option 703 is selected, the user will be able to set the volume of water for a first activity, for example a shower, as will be described in more detail with reference to Figure 8 below. If option 705 is selected, the user will be able to set the volume of water for a second activity, for example a bath. If option 707 is selected, the user will be able to set a program schedule for the household.

This may comprise the volume of water that they require each day of the week and the times of the day/night that they need those volumes of water. For example, the user may set that they require enough hot water for three showers every Monday, Tuesday, Wednesday, Thursday and Friday morning at 7am, that they require enough hot water for two showers on Friday night at 8pm, and that they require enough water for two showers on Saturday morning at 9am and a bath on Sunday evening at 6pm. This may be programmed in and the controller will operate the heating circuit to provide that water.

If option 709 is selected, the loss constant for the hot water installation can be set. As described above, this will depend in large part on the installation and over time, the controller may determine with great accuracy what the loss constant for the installation is and may vary it over time. If option 71 1 is selected, the clock of the system can be set.

Referring now to Figure 8, there is shown an alternative screen of the GUI, indicated generally by the reference numeral 800, where like parts have been given the same reference numeral as before. The screen 800 is the screen that is shown if the option 703 was selected from screen 700. The operator will be able to increase or decrease the volume of water required for set volume 1 (i.e. a shower) and confirm the value. It may be determined that the operator uses more or less than the set amount over time by displaying the amount used to the user or by monitoring the amount used and periodically setting the amount based on actual usage. This will provide the user with greater control over the system, avoiding waste and improving efficiency.

It is envisaged that an order screen may also be provided, similar to screen 300 in Figure 3. In the order screen, the operator will be able to select the shower icon 309 and press it once for one showers volume of water, twice for two showers volume of water and so on. In other words, the user will be able to order the amount of water required by simply pressing on the symbol of the water that they require. If they press the shower symbol once, they will effectively be ordering 50 litres (or whatever amount the shower has been set to) using the controller.

It will be understood that various modifications could be made to the foregoing embodiments without departing from the scope of the appended claims. For example, alternative heating arrangements could be provided. The hot water cylinder may have a coil including, but not limited to, a solar coil therein or a heating coil from the boiler. One or more additional temperature sensors and/or flow meters may be provided to monitor the flow and temperature of the liquids in the system to carefully monitor the temperature of the water and accurately predict the temperature and volume of the hot water in the hot water cylinder at a given moment in time. Additional or less buttons could be provided on the GUI of the controller. Indeed, the GUI may have no distinct buttons as a touch screen may be provided in which case certain parts of the screen will represent the buttons. Indeed, the controller may have a communication interface accessible through a wired or wireless link and no buttons on the actual GUI per se. Indeed, the controller may be provided with voice activation capabilities whereby the user can operate the controller using voice.

Another aspect of the present invention is the ability of the operator to control the domestic hot water installation remotely. In other words, the operator can access the control when not in the vicinity of the controller and cause the controller to operate the external heating circuit in order to deliver the desired amount of hot water. It is envisaged that the controller will be accessible via a communication module (not shown) which may be accessible through the internet and the operator will have an "App" on a mobile phone, smart phone or the like or another interface such as a web interface that is accessible on a computing device and will allow the controller to receive instructions to operate the external heating circuit or provide information on the amount of hot water available at a given point in time. Indeed, it is envisaged that programming of the controller and in particular the times of operation, the heating profile, the water requirement of the household could be managed through the App or other interface.

In this specification the terms "comprise, comprises, comprised and comprising" and the terms "include, includes, included and including" are all deemed totally interchangeable and should be afforded the widest possible interpretation.

The invention is not limited to the embodiments hereinbefore described but may be varied in both construction and detail within the scope of the appended claims.