Methods and systems and apparatus to support reduced energy and water usage

Abstract

A water heating system includes a hot water outlet valve 358, mains cold water inlet valve 356, electric heater 326, water tank 342, manifold (364, figure 7) and controller 340. The electric heater co

Description

Technical field The present disclosure variously relates to methods and systems, for installations including an in-building hot water supply system, that support reduced energy and water usage. Background The UK has a large number of small, 2 -3 bedroom or less, properties with gas-fired central heating, and most of these properties use what are known as combination boilers, in which the boiler acts as an instantaneous hot water heater, and as a boiler for central heating (space heating). Combination boilers are popular because they combine a small form factor, provide a more or less immediate source of "unlimited" hot water (with 20 to 35kW output), and do not require hot water storage. Such boilers can be purchased from reputable manufactures relatively inexpensively. The small form factor and the ability to do without a hot water storage tank mean that it is generally possible to accommodate such a boiler even in a small flat or house - often wall-mounted in the kitchen, and to install a new boiler with one man day's work. It is therefore possible to get a new combi gas boiler installed inexpensively. With the imminent ban on new gas boilers, alternative heat sources will need to be provided in place of gas combi boilers. In addition, previously fitted combi boilers will eventually need to be replaced with some alternative. Combination boilers generally have dimensions of from about 70cm to 200cm in height, from 420cm to 150cm in width and from 20cm to 100cm in depth, with an average internal combination boiler for a small to medium size house being about 75cm in height, 45cm in width and 50cm in depth, although, of course, those dimensions vary according to manufacturer and rated power of the boiler. With growing concerns over the environmental impact of energy consumption, there has been a recent growing interest in the use of heat pump technologies as a way of providing domestic heated water. A heat pump is a device that transfers thermal energy from a source of heat to a thermal reservoir. Although a heat pump requires electricity to accomplish the work of transferring thermal energy from the heat source to the thermal reservoir, it is generally more efficient than electrical resistance heaters (electrical heating elements) as it typically has a coefficient of performance of at least 3 or 4. This means under equal electricity usage 3 or 4 times the amount of heat can be provided to users via heat pumps compared to electrical resistance heaters. The heat transfer medium that carries the thermal energy is known as a refrigerant. Thermal energy from the air (e.g. outside air, or air from a hot room in the house) or a ground source (e.g. ground loop or water filled borehole) is extracted by a receiving heat exchanger and transferred to a contained refrigerant. The now higher energy refrigerant is compressed, causing it to raise temperature considerably, where this now hot refrigerant exchanges thermal energy via a heat exchanger to a heating water loop. In the context of heated water provision, heat extracted by the heat pump can be transferred to water in an insulated tank that acts as a thermal energy storage, and the heated water may be used at a later time when needed. The heated water may be diverted to one or more water outlets, e.g. a tap, a shower, a radiator, as required. However, a heat pump generally requires more time compared to electrical resistance heaters to get water up to the desired temperature. An important component of domestic energy consumption stems from use of domestic hot water, both in terms of the volume of hot water used, and in terms of energy wastage through overheating of domestic hot water. Hot water wastage is also, of course, a significant contributor to the more general problem of water wastage, which also needs to be addressed if mankind is going to have a sustainable future. Both the known combi boiler, and any replacement therefore, requires that water, both cold and hot, be directed through appropriate flow paths (which in some cases may be a common flow path), to appropriate destinations, such as another component of the water provisioning system, or to an outlet. The movement of water flow is controlled by a manifold. Essentially, a manifold is a pipe-like fitting or similar device that connects multiple inputs or outputs for fluids. Since different households, workplaces and commercial spaces have different requirements and preferences for heated water usage, new ways of heated water provision are desirable in order to enable heat pumps to be a practical alternative to electrical heaters. Summary The invention provides a domestic hot water provisioning system, as claimed in claim 1. Brief description of the drawings Embodiments of various aspects of the disclosure will now be described by way of example only, with reference to the accompanying drawings, in which: Figure 1 is schematic system overview of an exemplary water provision system; Figure 2 is a schematic drawing of part of an in-building water supply installation, showing components and flow paths; Figure 3 shows a schematic cut-away front elevation of the interior of an enclosure having a domestic hot water provisioning system; Figure 4 shows a schematic cross-sectional side elevation of the enclosure of Figure 3; Figure 5 shows a schematic cross-sectional side elevation similar to that of Figure 4, but at a different point of the enclosure of Figure 3; Figure 6 shows a schematic view of the electrical heater shown in Figure 2; Figure 7 shows a perspective view of the manifold used in the enclosure of Figure 3; Figure 8 shows a front elevational view of the manifold of Figure 7; Figure 9 shows a rear elevational view of the manifold of Figure 7; and Figure 10 shows a part cross-sectional view on line A-A of Figure 8. Detailed description In addressing domestic energy consumption, it is important to consider the energy used in providing hot water, and this means taking account not just of the temperature of the water that is supplied or stored, but also the volume of hot water used. In many countries and regions that are perceived to have ample fresh water, little attention was historically paid to the amount of water used by households, and that lack of attention was largely reflected in the configuration of water supply systems and the flow rates of water outlets. It was not uncommon for bath taps to flow more than 15 litres per minute, kitchen taps with flow rates or 12 litres per minute or more, and even basin taps with flow rates of 10 litres per minute or more. Shower outlets might flow more than 15 litres per minute, about 2 / 3 of which would typically come from the hot supply. Cold and heated water may be provided by a centralized water provision system to a plurality of water outlets, including taps, showers, radiators, etc., for a building in a domestic or commercial setting. An exemplary water provision system is shown in Fig. 1. In this schematic system, the water provision system 100 comprises a control module 110, which may include one or more Machine Learning Algorithms 120. The control module 110 is communicatively coupled to, and configured to control, various elements of the water provision system, including flow control 130 for example in the form of one or more valves arranged to control the flow of water internal and external to the system, a (ground source or air source) heat pump 140 configured to extract heat from the surroundings and deposit the extracted heat in a thermal energy storage 150 to be used to heat water, and one or more electric heating elements 160 configured to directly heat cold water to a desired temperature by controlling the amount of energy supplied to the electric heating elements 160. Heated water, whether heated by the thermal energy storage 150 or heated by the electric heating elements 160, is then directed to one or more water outlets as and when needed. In the embodiments, the heat pump 140 extracts heat from the surroundings into a thermal energy storage medium within the thermal energy storage 150. The thermal energy storage medium may in addition be heated by other sources. The thermal energy storage medium is heated until it reaches a desired operation temperature, then cold water e.g. from the mains can be heated by the thermal energy storage medium to the desired temperature. The heated water may then be supplied to various water outlets in the system. In the present schematic system, the control module 110 is configured to receive input from a plurality of sensors 170-1, 170-2, 170-3,..., 170-n. The plurality of sensors 170-1, 170-2, 170-3, ..., 170-n may for example include one or more air temperature sensors disposed indoor and / or outdoor, one or more water temperature sensors, one or more water pressure sensors, one or more timers, one or more motion sensors, and may include other sensors not directly linked to the water provision system 100 such as a GPS signal receiver, calendar, weather forecasting app on e.g. a smartphone carried by an occupant and in communication with the control module via a communication channel. The control module 110 is configured, in the present embodiment, to use the received input to perform a variety of control functions, for example controlling the flow of water through the flow control 130 to the thermal energy storage 150 or electric heating elements 160 to heat water. A dotted line 180 Illustrates schematically an enclosure within which the components described above, other than the sensors 170-1, 170-2,170-3,..., 170-n may be located. While a heat pump is generally more energy efficient for heating water compared to an electrical resistance heater, a heat pump requires time to start up as it performs various checks and cycles before reaching a normal operation state, and time to transfer sufficient amount of thermal energy into a thermal energy storage medium before reaching the desired operation temperature. On the other hand, an electrical resistance heater is generally able to provide heat more immediately. Thus, a heat pump can take longer to heat the same amount of water to the same temperature compared to an electrical resistance heater. Figure 2 shows, schematically, a heating system 300, showing some of the components that may be used in a system similar to that described above with reference to Figure 1 and flow paths between the components. As shown, heating system 300 includes a mains inlet of cold water 302 and a domestic hot water outlet 304, such as a tap or shower outlet and a domestic hot water heating appliance 310, such as a radiator. The system 300 further includes a heat pump 306, which may typically have a heating capacity of 3-12 kW, a heat exchanger 308, and a thermal storage appliance 342, such as a relatively small water tank holding approximately 15 litres of water. These components are connected by water flow pipes, with flow transducers, temperature transducers and valves that control the water flows though the pipes in a manner to be described below. The flow transducers and temperature transducers are all connected via signal lines to provide signals to a system controller 340, which controls the valves in order to control the system to operate in one of several operating modes as will be described below. One, some or all of the flow transducers may be replaced by pressure transducers that determine the pressure of the fluid in order to be able to determine the flow rate. The controller 340 may be similar to the control module 110 described above with reference to Figure 1 and may include a Machine Learning Algorithms 120. Leading from the mains cold water inlet 302 via an inlet valve 356 a first flow path 312 leads to a first inlet HX1 of the heat exchanger 308. A temperature transducer TT01 and a flow transducer FT01 measure the temperature and the flow rate of the cold water at the mains cold water inlet 302. A temperature transducer TT02 and a flow transducer FT03 measure the temperature and the flow rate at the first inlet HX1 to the heat exchanger 308. A second flow path 314 leads from the first flow path 312 near the mains cold water inlet 302 towards a outlet valve 358 leading to the domestic hot water outlet 304. A first motorised valve MV01 is positioned in the second flow path 314 to regulate the water flow within the second flow path 314. A flow transducer FT02 measures the flow rate of the cold water passing through the first motorised valve MV01, from which it is selectively combined with water leaving a motorised three-way valve MV03 as will be further described below, towards the domestic hot water outlet 304 adjacent which a temperature transducer TT07 measures the temperature of the water leading to the domestic hot water outlet 304. A first part 316a of a third flow path 316 leads from the first flow path 312 nearer to the heat exchanger 308 than the second flow path 314. A second motorised valve MV02 is positioned in the first part 316a of the third flow path 316 to regulate the water flow within the first part 316a of the third flow path 316 leading to a lower part of the thermal storage appliance 342. A temperature transducerTT11 measures the temperature of the water at the lower part of the thermal storage appliance 342 and another temperature transducer TT10 measure the temperature of the water at an upper part of the thermal storage appliance 342. A second part 316b of the third flow path 316 leads from the upper part of the thermal storage appliance 342 to a second inlet B of a motorised three-way valve MV03, with a temperature transducer TT05 measuring the temperature of the water in the second part 316b of the third flow path 316. A return flow path 318 is provided to return water from an outlet of the motorised valve MV02 in the first part 316a of the third flow path 316 to an inlet of the motorised valve MV02 via a circulation pump 320 and a non-return valve 322. The heat exchanger 308 has a first outlet HX2 which is connecter to receive the water having entered the heat exchanger via first inlet HX1. A fourth flow path 324 leads from the first outlet HX2 of the heat exchanger to a first inlet A of the motorised three-way valve MV03, via an electric heater 326. A temperature transducer TT03 measures the temperature of the water leaving the first outlet HX2 of the heat exchanger 308 and a temperature transducer TT04 measures the temperature of the water leaving the electrical heater 326 and entering the first inlet A of the motorised three-way valve MV03. A fifth flow path 328 leads from the outlet AB of the motorised three-way valve MV03 towards the domestic hot water outlet 304, and combines with the first flow path 314 prior to reaching the domestic hot water outlet 304. A temperature transducer TT06 measures the temperature of the water leaving the outlet AB of the motorised three-way valve MV03 prior to being combined with water from the second flow path 314 and a temperature transducer TT07 measures the temperature of the water after it has been combined with water from the second flow path 314 as it enters the domestic hot water outlet 304. On theother sideof the heat exchanger 308 from the first inlet HX1 and the first outlet HX2 are second inlet HX3 and second outlet HX4. The second inlet HX3 is fed by a sixth flow path 330 leading from an outlet of the heat pump 306 via a motorised three-way valve MV04, with a temperature of transducer TT08 measuring the temperature of the water at the second inlet HX3 of the heat exchanger 308. A seventh flow path 332 is coupled between the second outlet HX4 of the heat exchanger 308 via outlet valve 350 and an inlet of the heat pump 306. As shown, the heat pump 306 includes a heat exchanger 334 and a circulating pump 336 to heat water received at the inlet and to output the heated water to the outlet. A temperature transducer TT09 measures the temperature of the water leaving the heat exchanger 308 and being passed into the inlet of the heat pump 306. Thus, the motorised three-way valve MV04 has a first inlet A coupled to the outlet of the heat pump 306 via an inlet valve 354, an outlet AB coupled to the second inlet HX3 of the heat exchanger 308. A second outlet B of the motorised three-way valve MV04 leads via an outlet valve 352 to an inlet of the domestic hot water heating appliance 310, whose outlet leads to the seventh flow path 332 via inlet valve 360. A dotted line labelled 344 illustrates all the components of the system that can be included in a housing that may be made of a similar size and shape as to replace a combination boiler, although it will be appreciated by people skilled in the art that in some circumstances, the components may be otherwise arranged, inside or outside such a housing, which may not be needed at all in some circumstances. In particular, for example temperature transducer TT09 may be located within the housing 344 nearer the heat exchanger 308 or outside the housing 344 nearer the domestic hot water heating appliance 310. Others of the temperature and flow transducers, such as, for example, flow transducer FT01 and / or temperature transducer TT01 may similarly be positioned inside or outside the housing, as desired. The inlet and outlet valves 350, 352, 354, 356, 358 and 360 are located on the periphery of the housing to provide all the necessary inlet and outlet connections. The heating system 300 may be operated in a number of modes of operation, which will now be briefly described. Although there are a number of differing operating modes, several may be interrelated and used in combination or separately. The modes are: Heat Exchanger Charging Mode in which the heat exchanger 308 is used to heat water that is used to fill (or charge) the thermal storage appliance 342; Electric Heater Charging Mode in which the electric heater 326 is used to heat water that is used to charge the thermal storage appliance 342; Initial Hot Water Mode, in which hot water provided to the domestic hot water outlet 304 is provided either by the thermal energy storage appliance 342, if it is charged with hot water, or is heated by the electric heater 326, or a combination of both, as required; Mixed Water Mode to decrease temperature of water from Mode 3 is mixed with cold water from the mains cold water inlet 302 to reduce the temperature of the water being provided to the domestic hot water outlet 304; Steady State Mode in which the heat pump 306 is used to heat water from the cold water from the mains cold water inlet 302 at the heat exchanger and to provide the heated water, optionally further heated by the electric heater 326, and mixed with cold water from the mains cold water inlet 302 to reduce the temperature of the water being provided to the domestic hot water outlet 304; Combined Mode, which is a combination of the Initial Hot Water Mode and the Steady State Mode; Heat Pump Defrost Mode; House Heating Mode; and Overall Mode, which is a combination of the Combined Mode and the House Heating Mode. In the Heat Pump Charging Mode the thermal storage appliance 342 is charged with hot water provided from the heat exchanger 308. In this mode of operation, the second motorised valve MV02 is closed and the circulation pump 320 in the return flow path 318 is turned on so that water is pumped from the thermal storage appliance 342 via the circulation pump 320, the non-return valve 322 and the first flow path 312 to the first inlet HX1 of the heat exchanger 308. Since the water is being pumped from the first part 316a of the third flow path 316 into the first flow path 312, water from the domestic cold water inlet 302 does not affect the flow. The water is heated in the heat exchanger 308 and is passed from the first outlet HX2 through fourth flow path 324 via the electric heater 326, which in this mode is turned off, to the motorised valve MV03 which is controlled to direct the water from port A to port B, so that the water returns to the thermal storage appliance 342. It will be apparent that the water can be so looped around more than once, if desired, until the water at the thermal storage appliance 342 reaches a predetermined temperature, as measured by temperature transducer TT10 or temperature transducer TT04. In order to provide the heat exchanger 308 with hot water from the heat pump, the motorized valve MV04 is controlled so that water in the sixth flow path 330 from the heat pump 306 passes through port A to port AB of the motorized valve MV04 and hence to the second inlet HX3 of the heat exchanger 308. The water then returns from second outlet HX4 of the heat exchanger 308 to the heat pump 306. In this mode the heat pump power is modulated to transfer heat to the circulating hot water loop, charging the thermal energy storage appliance 342, for example a 15 litre tank, with continued operation of the circulation pump 320 on the hot water side. An example case would be if the circulation pump 320 runs at 6L / min, and the heat pump 306 is modulated to heat the water in the hot water loop to 55°C at the heat exchanger 308, the circulation pump 320 would run for approximately 6 minutes to charge the water in the thermal energy storage appliance 342 to 55°C in 2 passes through the loop. In the Electric Heater Charging Mode the thermal storage appliance 342 is charged with hot water heated by the electric heater 326. In this mode, similarly to the first mode, the second motorised valve MV02 is closed and the circulation pump 320 in the return flow path 318 is turned on so that water is pumped from the thermal storage appliance via the circulation pump 320, the non-return valve 322 and the first flow path 312 to the first inlet HX1 of the heat exchanger 308. The heat pump does not provide thermal energy to the heat exchanger in this mode, so the water is passed from the first outlet HX2 of the heat exchanger through fourth flow path 324 to the electric heater 326, which in this mode is actively controlled to heat the water. The hot water is then passed to the motorised valve MV03 which is controlled to direct the water from port A to port B, so that the hot water returns to the thermal storage appliance 342. It will be apparent that the water can be so looped around more than once, if desired, until the water at the thermal storage appliance 342 reaches a predetermined temperature, as measured by temperature transducer TT10 or temperature transducerTT04. In this mode the electric heater power is modulated to heat the circulating water on the hot water side to the desired temperature. An example case would be if the circulation pump 320 runs at 5L / min, and the electric heater 326 is modulated to heat the water in the hot water loop to 55°C as measured at temperature transducer TT04, the circulation pump 320 would run for 6 minutes to charge the water in the thermal energy storage appliance 342 to 55°C in 2 passes. The controller can therefore select which charging mode to use to charge the thermal energy storage appliance. This may depend on whether the heat pump is available and active. If it is active and hot fluid is already available at the heat exchanger then the Heat Pump Charging mode can be selected. If the heat pump is already active but motorised valve MV04 is not allowing the hot fluid to pass thorough to the heat exchanger, then the Heat Pump Charging mode may still be selected and the motorised valve MV04 is controlled, as mentioned above, so that the hot fluid passes from port A to port AB and hence to the second inlet HX3 of the heat exchanger. On the other hand, if the heat pump is not active, and given that, as described above, it takes some time for it to start to produce hot fluid, then the controller may select the Electric Heater Charging mode, so as to use the electric heater to heat the water to charge the thermal energy storage appliance. In the Initial Hot Water Mode hot water is provided to the domestic hot water outlet 304 either by the thermal energy storage appliance 342, if it is charged with hot water, or is heated by the electric heater 326, or a combination of both. If the thermal energy storage appliance 342 is charged full of hot water, then that can be used in preference to using the electric heater 326 to heat the water. To use hot water from the thermal energy storage appliance 342, the motorised valve is MV02 is open, so that the third flow path 316 is used to take cold water from the mains cold water inlet 302 to displace hot water from the thermal storage appliance 342. The hot water from the thermal storage appliance 342 passes through motorised valve MV03 from port B to port AB. As the temperature of the water from the thermal energy storage appliance 342 reduces (due to mixing with the cold water from the mains cold water inlet 302), the motorised valve MV03 is controlled to gradually open the pathway from port A to port AB, while gradually closing the pathway from port B to port AB. The flow rates across ports A-AB and ports B-AB are configured to be inversely proportional so that the flow of water out from port AB into the fifth flow path 328 leading to the domestic hot water outlet 304 remains constant. This is regulated according to the temperature sensed at temperature transducer TT06 depending on whether the sensed temperature is less than a desired temperature at temperature transducer TT06. Thus, if the temperature at temperature transducer TT06 is less than the desired temperature, the proportion of valve port B allowing fluid flow to port AB can be reduced from 100% to allow flow through port A, whilst reducing flow from port B. The now reduced flow from port B is therefore mixed with coming from port A. The water passing through port A of motorised valve MV03 comes from the fourth flow path 324 and via the electric heater 326 where it is heated, as necessary, to provide the hot water at port AB at the desired temperature, as sensed at temperature transducer TT06. Water in the fourth flow path 324 comes through the heat exchanger 308, having reached it via the first flow path 312 from the mains cold water inlet 302. This mode of operation relies on the thermal energy storage appliance 342 being pre-charged, for example by either of the first or second modes of operation. Typically, the water in the thermal energy storage appliance 342 is charged to 1.25 times the desired temperature as sensed at temperature transducer TT07 measured as temperatures at temperature transducers TT11 and TT10. When there is a secondary hot water demand of flow, as measured at flow transducer FT01, water flows through the third flow path 316 and into the thermal energy storage appliance 342. The thermal energy storage appliance 342 may be a stratified tank holding 15L, where 15L of water entering at a temperature measured by temperature transducer TT01, will displace 15L of preheated water. The depletion of the tank is measured by the read temperature at temperature transducers TT10 and TT11, and by knowing amount of water that has passed through the tank: V=t*(Q@ FT01-Q@ FT03-Q@ FT02) Where V is the depletion of the tank; t is time; Q@FT01 is the flow measured at flow transducer FT01; Q@FT02 is the flow measured at flow transducer FT02; and Q@FT03 is the flow measured at flow transducer FT03. As the water flows out of the tank and into port B of motorised valve MV03, if for whatever reason the temperature at temperature transducer TT05 is less than the desired temperature at temperature transducer TT07, the electric heater 326 can be used to top up the temperature of the water passing through the fourth flow path 324, where motorised valve MV03 is controlled to at least partially open port A to allow a at least a proportion of the flow measured at flow transducer FT01 through the fourth flow path 324 to the electric heater 326, where the bypassed proportion of flow of at flow transducer FT03 can be heated from the temperature at temperature transducer TT03 to a temperature at temperature transducer TT04 by controlling the electric heater 326. This is a useful mode to use when the heat pump 306 is not operational, or not yet fully operational, when it is not providing hot fluid to the heat exchanger 308. Of course, as the heat pump heats up, the fluid will start to get hotter, and may be provided to the heat exchanger 308, so that the water passing through it may start to increase in temperature, as measured by temperature transducer TT03, so that the heating provided by the electric heater 326 may be controlled to produce the appropriate desired temperature. In the Mixed Water Mode the temperature of the hot water from the thermal energy storage appliance 342 and / or from the electric heater 326 (provided as per the Initial Hot Water Mode mode of operation described above) or from the heat exchanger 308 if that is producing hot water as per the Steady State mode, is mixed with cold water from the mains cold water inlet 302 to reduce the temperature of the water being provided to the domestic hot water outlet 304. In this Mixed Water mode, whether the hot water leaving the port AB of the motorised three-way valve MV03 is provided via the heat exchanger 308 via the fourth flow path 324 (whether or not that water is heated by the electrical heater 326) or from the thermal storage appliance 342, the temperature of the hot water leaving the port AB of the motorised three-way valve MV03 is measured using the temperature transducer TT06. The temperature is signalled to the system controller 340 (not shown in Figures 4 to 12). The controller 340 then determines whether the temperature at temperature transducer TT06 is higher than the desired temperature for the hot water to be available at the domestic hot water outlet 304. If it is higher, then cold water from the second flow path 314 is mixed into the hot water leaving the port AB of the motorised three-way valve MV03 into the fifth flow path 328 by opening the motorised valve MV01 to allow cold water from the mains cold water inlet 302 to flow through the second flow path 314 to the fifth flow path 328. The amount by which the motorised valve MV01 is opened will depend on the temperature of the cold water from the mains inlet 302 as measured by the temperature transducer TT01 and the flow rate of the cold water from the mains inlet 302 as measured by the flow transducer FT01 to produce the desired flow rate as measure by flow transducer FT02 in the second flow path 314 leading to the fifth flow path 328 so that the cold water from the second flow path 314 mixes with the hot water in the fifth flow path 328 to produce the desired temperature for the water to be available at the domestic hot water outlet 304, as measured by the temperature transducer TT07. A suitable control program executed by the controller will modulate this mixing in normal operation, preventing any overshoot from the desired temperature at the domestic hot water outlet 304. This firstly acts as a safety feature to prevent scalding of a user who doesn't have temperature safety valves installed on taps or faucets in the home. Secondly, the mixing allows the thermal storage appliance 342 to be charged to a higher temperature than that of the desired outlet temperature, so that when the system is run in a mode of operation where the thermal storage appliance 342 provides the hot water to be used from the domestic hot water outlet 304, the higher temperature water is mixed down with cold water from the mains cold water inlet, thereby producing a slower drain on the thermal storage appliance 342 and giving it a proportionally higher effective volume. After the Initial Hot Water mode of operation, in which the hot water is initially provided by the thermal energy storage appliance 342 of from the electric heater 326 (or a combination of both), once the heat pump has reached full operation and is providing hot fluid to the heat exchanger 308, the Steady State mode of operation may be instituted. In this Steady State Mode the motorised valve MV02 is shut so that there is no flow through the third flow path 316 and the thermal energy storage appliance 342. The electric heater 326 is active and controllable by the controller. The mixing control as described above with reference to the fourth mode is also active. Thus, motorised valve MV04 is controlled to pass water from port A to port AB. In this mode the heat pump 306 is actively providing heated fluid via the sixth flow path 330 and the motorised valve MV04 set to pass the fluid from port A to port AB to the heat exchanger 308 at a temperature determined by the measured flow rate of secondary hot water demand and set hot water temperature as measured a temperature transducer TT07. The water flow passing through the heat exchanger 308 is heated by the heat exchanger to a temperature measured by temperature transducer TT03. Thus, the flow measured at flow transducer FT03, the temperature measured by temperature transducer TT02, and the temperature measured by temperature transducer TT03 can be used to determine the amount of energy provided by the heat pump and subsequently provide feedback to the heat pump for power output adjustments. If the temperature measured by temperature transducer TT03 is determined to be less than the desired temperature at temperature transducer TT07, the electric heater 326 is controlled to heat the water to top the temperature of the water to the required temperature as measured at the temperature transducer TT04. It will be apparent that since the water is passing through the motorised valve MV03 from port A to port AB, the temperature measured by temperature transducer TT04 will be the same as the temperature at temperature transducerTT06. If the temperature measured by temperature transducer TT06 is greater than desired temperature at temperature transducer TT07, cold water can be mixed with the hot water described for the fourth mode of operation, in which the temperature of the hot water is mixed with cold water from the mains cold water inlet 302 to reduce the temperature of the water being provided to the domestic hot water outlet 304. The Combined mode of operation is, essentially, a combination of the Initial Hot Water and the Steady State modes. The hot water is provided from the heat exchanger 308 or from the thermal storage appliance 342. The electric heater 326 can be used to top up the water temperature from the heat exchanger 308, if the water temperature measured at temperature transducer TT06 is lower than the desired water temperature at temperature transducer TT07. On the other hand, if the water temperature measured at temperature transducer TT06 is higher than the desired water temperature at temperature transducer TT07 cold water from the mains cold water inlet 302 via the second flow path 314 can be mixed into the hot water to reduce its temperature to the desired temperature. There are occasions, in inclement weather, when the heat pump is at risk of freezing up. In such circumstances, whether to defrost a frozen heat pump, or to try to prevent the heat pump freezing if it is known that the temperature is likely to fall to below freezing, the controller may control the system to bring the Heat Pump Defrost Mode into operation. In this Heat Pump Defrost mode of operation the second motorised valve MV02 is closed and the circulation pump 320 in the return flow path 318 is turned on so that water is pumped from the thermal storage appliance 342 via the circulation pump 320, the non-return valve 322 and the first flow path 312 to the first inlet HX1 of the heat exchanger 308. Since the water is being pumped from the first part 316a of the third flow path 316 into the first flow path 312, water from the domestic cold water inlet 302 does not affect the flow. The water is passed from the first outlet HX2 through fourth flow path 324 via the electric heater 326 to the motorised valve MV03 which is controlled to direct the water from port A to port B, so that the water returns to the thermal storage appliance 342 and may circulate around again. The water entering at the first inlet HX1 of the heat exchanger 308 is controlled to be hot, either from the thermal storage apparatus, or, more likely, from being heated by the electric heater 326, or a combination of both, depending on the extent to which the thermal storage medium is charged with hot water. In this Heat Pump Defrost mode the electric heater is active and is modulated to transfer heat to the circulating hot water loop, passing through the thermal energy storage appliance 342. The motorized valve MV04 is controlled so that water in the sixth flow path 330 from the heat pump 306 passes through port A to port AB of the motorized valve MV04 and hence to the second inlet HX3 of the heat exchanger 308. The water then returns from second outlet HX4 of the heat exchanger 308 to the heat pump 306. As the water passes from the second inlet HX3 to second outlet HX4 of the heat exchanger 308 it is heated by heat exchange with the hot water entering through the first inlet HX1 of the heat exchanger 308 to the first outlet HX1, as described above. The heated water returned to the heat pump 306 is then able to provide thermal energy to the refrigerant loop at the heat pump 306, which in turn is being circulated via the heat pump's compressor. The now hot refrigerant is then able to defrost the evaporator coils. The House Heating Mode assumes that no hot water is required at the domestic hot water outlet 304 (or any other hot water outlet, and this House Heating mode is therefore focussed exclusively on providing hot fluid, which may be water, for heating the domestic dwelling or other building, either through the use of radiators or a hot water underfloor heating system. In this House Heating mode, the heat pump is actively producing hot water which is directed through the motorised valve MV04 controlled to pass the hot water from port A to port B so that the hot water passes to the domestic hot water heating appliance 310, whose outlet leads back to the heat pump 306. The Overall Mode, which is a combination of the Combined Mode and the House Heating Mode is, therefore, a combination of the Initial Hot Water, Steady State and eighth House Heating modes so that all the various modes discussed above can be combined, as required. In this case, the electric heater 326 is active and modulable and all four motorised valves MV01, MV02, MV03 and MV04 are active and modulable. In this Overall mode the Heat Pump 306 can provide both heating (as per the House Heating mode discussed above) and thermal energy to heat or preheat hot water at the heat exchanger 308. As described above in relation to the Combination mode, the hot water is provided from the heat exchanger 308 or from the thermal storage appliance 342. The electric heater 326 can be used to top up the water temperature from the heat exchanger 308, if the water temperature measured at temperature transducer TT06 is lower than the desired water temperature at temperature transducer TT07. On the other hand, if the water temperature measured at temperature transducer TT06 is higher than the desired water temperature at temperature transducer TT07 cold water from the mains cold water inlet 302 via the second flow path 314 can be mixed into the hot water to reduce its temperature to the desired temperature. An important application of the heating system according to the disclosure is as a means to enable a heat pump to be used as a practical contributor to the space heating and hot water requirements of a dwelling that was previously provide with a gas-fired combination boiler (or which might otherwise have such a boiler installed). It will be appreciated that it will often be convenient both to provide an enclosure both for aesthetics and safety, just as is the case conventionally with combi boilers. Moreover, preferably any such enclosure will be dimensioned to fit within a form factor enabling direct replacement of a combi boiler - which are typically wall mounted, often in a kitchen where they co-exist with kitchen cabinets. Based on the form of a generally rectangular cuboid (although of course, for aesthetics, ergonomics, or safety, curved surfaces may be used for any or all of the surfaces of the container) with a height, width and depth, suitable sizes may be found in the approximate ranges: height 650mm to 800mm; width 350mm to 550mm; depth 260mm to 420mm; for example, 800 mm high, by 500mm wide, and 400mm deep. One notable distinction of heating systems according to the disclosure with respect to gas combi boilers is that while the enclosures of the latter generally have to be made of non-combustible materials - such as steel, due to the presence of a hot combustion chamber, the internal temperatures of the enclosures of the present heating system will generally be considerably less than 100 Celsius, typically less than 70 Celsius, and often less than 60 Celsius. So, it becomes possible to use flammable materials such wood, bamboo, or even paper, in fabricating an enclosure for the heating system. The lack of combustion also opens up the possibility to install the enclosures in locations that would generally never be considered as suitable for the installation of gas combi boilers - and of course, unlike a gas combi boiler, heating systems according to the disclosure, do not require a flue for exhaust gases. So, for example, it becomes possible to configure an enclosure for installation beneath a kitchen worktop, and even to make use of the notorious dead spot represented by an under-counter corner. For installation in such a location the enclosure could actually be integrated into an under-counter cupboard - preferably through a collaboration with a manufacturer of kitchen cabinets. But greatest flexibility for deployment would be retained by having an enclosure that effectively sits behind some form of cabinet, the cabinet being configured to allow access to the enclosure. As mentioned above, most of the components of the system, excluding the heat pump 306, the domestic hot water outlet 304 and the domestic hot water heating appliance 310 are generally included within the enclosure (or housing) 344 that may be made of a similar size and shape as to replace a combination boiler. The enclosure 344 may include insulating material to mitigate against heat loss and it will be apparent that the differing operating modes, may be used in combination or separately, as desired and controlled by the controller. The enclosure 344 is shown in Figures 3-5, which show, schematically, interior views of various components in the enclosure 344. As illustrated, elements that are shown in Figure 2 have the same reference numerals. However, it will be apparent that not all the elements shown in Figure 2 are illustrated in Figures 3-5. Nevertheless, Figures 3-5 show other elements, which are not illustrated in Figure 2, as will be further described below. Thus, Figure 3 is a cut-away front elevational view of the enclosure 344 showing the controller 340 and the inlet and outlet valves 350, 352, 354, 356, 358 and 360. There can also be seen in Figure 3 a metal enclosure 362 for various electrical circuits of the system, a manifold 364 for directing, as necessary, water between the various inlet and outlet valves 350, 352, 354,356,358 and 360, and a pressure switch 370 for measuring cold water pressure in order to turn the electric heater 326 off if the water pressure is too low. Figure 3 shows a metal enclosure 362 for various electrical circuits of the system, a manifold 364 for directing, as necessary, water between the various inlet and outlet valves 350, 352, 354, 356, 358 and 360. Figure 3 further shows a power supply 374, a power supply cable 378, electric breakers 372, such as miniature circuit breakers (MCBs), cable terminals 368 to which an external electrical mains supply is to be connected, controller 340, the electric heater 326, and the additional bracket 348 (mentioned above). Figure 3 also shows the second part 316b of the third flow path 316, fifth flow path 328, an expansion vessel 346, which is coupled to the thermal storage appliance 342 (not shown). In addition, Figure 3 shows the heat exchanger 308, the temperature transducers TT04, TT05 and TT06, as well as the motorised three-way valve MV03, which are described above with reference to Figure 2. There is also shown insulating foam material 366 (shown with diagonal cross hatching), which is positioned around the various components and coupling, and is configured in a predetermined shape in order to allow the components and couplings to be located therein. The insulating foam material 366 may be made up of several parts which may fit together and around the various components and couplings, as desired. Figure 4 shows the motorised valves MV01, MV02 and MV04 and the electric heater 326. Figure 4 also shows the expansion vessel 346, which is coupled to the thermal storage appliance 342 (not shown), power supply 374, electric breakers 372, and the additional bracket 348 used for installation of the inlet and outlet valves 350, 352, 354, 356, 358 and 360 prior to installation of the enclosure 344. Also shown in Figure 4 is a bracket 380 which is used to mount the enclosure 344 to a structure, such as a wall. There are also illustrated in Figure 4, the manifold 364, the non-return valve 322, which is inserted in the manifold 364 and various parts of the insulating foam material 366. Figure 5 shows the thermal storage appliance 342, the heat exchanger 308, together with first inlet HX1 and second inlet HX3, the additional bracket 348, the power supply 374, electric breakers 372, cable terminals 368 and the power supply cable 378. There are also illustrated in Figure 5 various parts of the insulating foam material 366. It will be appreciated that while specific components and sensors are shown, any appropriate architecture may be employed. Figure 6 shows a schematic view of the electrical heater 326 and controller 340 shown and described above. Figure 6 does not show the fourth flow path 324, but only the electrical connections. In this embodiment, three electrical heating elements 610, 620, 630 are connected in parallel to a power source (not shown), with a respective semiconductor switching element 615, 625, 635 connected in series with each of the heating elements 610, 620, 630. It will be appreciated, however, that any number of electrical heating elements 610, 620, 630 more than one may be used, and, similarly, there may be any number more than one of the semiconductor switching elements 615, 625, 635. There may also be more than one of the semiconductor switching elements 615, 625, 635 connected in parallel with each of the electrical heating elements 610, 620, 630, so that any one of the semiconductor switching elements 615, 625, 635 that are connected in parallel may be selected to activate the respective electrical heating element 610, 620, 630. The power source may be a three phase power source, with each heating element connected to a different phase. The semiconductor switching element 615, 625, 635, although shown as a silicon controlled rectifier, may be any appropriate solid state device, such as a diode, a Silicon-controlled rectifier (SCR), a thyristor, a gate turn-off thyristor, a triac, a bipolar junction transistor (BJT), a power MOSFET, an Insulated-gate bipolar transistor (IGBT), a MOS-controlled thyristor (MCT), or an integrated gate-commutated thyristor (IGCT). Figures 7, 8, 9 and 10 show perspective, front, rear and part-sectional views of the manifold 364. As can be seen in Figures 7 and 9, the semiconductor switching elements 615, 625, 635 are mounted on the manifold 364. The manifold 364 is made of a heat conducting material, which may be metal or plastic or any combination of metal and plastic. As described above, the manifold directs, as necessary, water between the various inlet and outlet valves 350, 352, 354, 356, 358 and 360, which are connected to various inlets and outlets of the manifold 364. Figures 8 and 10 show the inlets and outlets of the manifold 364. The inlets and outlets are arranged in a line and comprise, starting from the top in Figure 8, first outlet 655, which is connected to first motorised valve MV01, first inlet 660 connected to mains cold water inlet 302, second outlet 665 connected to the first inlet HX1 of the heat exchanger 308, second inlet 670 connected to circulating pump 320, and third outlet 675 connected to second motorised valve MV02. Figure 10 shows the inlets and outlets with pipe end fittings connected to the respective inlets and outlets. The manifold 364 has a number of selectable internal flowpaths between the inlets and outlets to direct water according to the operating mode that is selected. Each of the internal flowpaths therefore corresponds to an operating mode. Each of the internal flowpaths also has an associated temperature profile, which is known based on previous measurements and stored. Therefore, by knowing which operating mode is selected, the controller will know the temperature profile of the corresponding internal flowpath within the manifold. The controller 340 is connected to the manifold 364 to provide signals between the controller 340 and the manifold 364 to allow the controller to control the manifold 364 to select the particular internal flowpath corresponding to the desired operating mode. The semiconductor switching element 615, 625, 635 are controlled by the controller 340 to control the semiconductor switching elements 615, 625, 635 to control the electrical heating elements 610, 620, 630 of the electrical heater 326. The semiconductor switching element 615, 625, 635, being mounted on the manifold 364, are therefore exposed to heat conducted through the walls of the manifold 364 corresponding to the temperature profile of the internal flowpath corresponding to the selected operating mode. Since the semiconductor switching element 615, 625, 635 can get hot when in operation, it is desirable to cool them, when possible. Therefore, the controller 340 can select one or more of the semiconductor switching element 615, 625, 635 that are adjacent a cool or cold part of the internal flowpath corresponding to the selected operating mode, so that the selected semiconductor switching element(s) 615, 625, 635 is / are cooled by the manifold. The cool or cold path of the internal flowpath therefore provides a heatsink for the semiconductor switching element, whereby surplus heat from the semiconductor switching element is conveyed to the fluid in the internal flowpath to cool the semiconductor switching element. Of course, this only applies if less than full heating is required from the electrical heater 326. Furthermore, it is also possible for the controller 340 to select the one or more semiconductor switching elements 615, 625, 635 based on a history of their use, that the controller 340 has available, for example due to the controller 340 updating a memory each time each semiconductor switching element 615, 625, 635 is active. The controller 340 can then use this knowledge to select, if possible, particular semiconductor switching elements 615, 625, 635 so as to balance the overall use of all of the semiconductor switching elements 615, 625, 635. The selection of the one or more semiconductor switching elements 615, 625, 635 may additionally or alternatively be based, at least in part, on an estimated or detected temperature of one or more previously selected semiconductor switching elements 615, 625, 635, so that, if it is detected that they are, or are likely to become, overheated, a different one or more semiconductor switching elements 615, 625, 635 may be selected so as to try to reduce the likelihood of overheating. It may also be based on an estimated or measured temperature of the internal flowpath corresponding to a selected operating mode so that the one or more semiconductor switching elements 615, 625, 635 can be selected to be adjacent an internal flowpath that provides good, or optimum, cooling. Similarly, the controller 340 can select the one or more semiconductor switching elements 615, 625, 635 based on a history of the use of the different heating elements 610, 620, 630. Again, the controller 340 may have such a history available, for example due to the controller 340 updating a memory each time each heating element 610, 620, 630 is active. The controller 340 can then use this knowledge to select, if possible, particular semiconductor switching elements 615,625, 635 so as to balance the overall use of all of the heating elements 610, 620, 630. The manifold is also provided with several (for example, three) flow sensors 680,681, 682, which are used to measure flows within the manifold. Having the flow sensors mounted on the manifold itself to measure flow at the inlets and outlets enables the controller to detect real time variations in the flows so as to be able to adjust the flows within the system based on the variations. For example, if the flow from the mains cold water inlet increases, then heating may need to increase to compensate, and vice versa. Similarly, if a flow at an outlet is found to reduce or increase, then heating may be decreased or increased to maintain the same temperature, or an inlet flow rate may be increased or reduced to maintain the same flow. Similarly, as shown in Figures 9 and 10, the manifold may be provided with several temperature sensors 650, 651, 652 (for example, three) to measure the temperature of the liquid flow in one or more of the internal flowpaths. It is known to use small temperature sensing devices located in a specific flow path in order to provide temperature values to try to mitigate the effects of temperature lag. However we have found that such lag can also be compensated for by integrating the temperature sensors and the manifold, which also provides good thermal performance and ease of assembly. It will be appreciated that because the manifold is made of heat conducting material, heat may pass between different flow paths, thereby affecting the temperature of liquids therein. Surprisingly, therefore, providing one or more temperature sensors on the manifold itself can provide more accurate measurements of the temperatures of the liquids in different flowpaths in different modes of operation. By having the temperature sensors integrated with the manifold, assembly is simplified and space within the enclosure is increased since separate temperatures sensors are no longer needed so that other components (such as the th thermal storage appliance) may, potentially be increased in size. The use of the flow sensors and / or the temperature sensors provides better thermal and / or flow response times because the sensors are integrated into the manifold so that changes, as well as the final temperatures and / or flow rates, may be detected allowing the controller to adjust the system as necessary. By having sensors on the inlets as well as the outlets, the output can be predicted based on the inlet temperature and / or flow rate and also based on historical usage data so that valves can be controlled to start moving in advance by using the predicted temperatures and / or flow rates. For example, the Machine Learning Algorithm 120 of the controller 340 may be trained using detected inlet and outlet temperatures and / or flow rates in different operating modes so as to be able to predict an output temperature and / or flow rate based on a detected inlet temperature and / or flow rate for a particular operating mode. Furthermore, the predicted output temperatures may be adjusted based on other parameters of the particular selected operating mode the system is operating in and / or on operating conditions. For example, the parameter may be based on previous operating modes (for example, if an immediately previous operating mode was similar to the current operating mode, then the internal flow path may be similar, i.e. may have some path elements in common), or previous temperatures or flow rates, or length of time for which the operating mode (or a previous operating mode) is / was in operation. Adjusting a component, such as a valve, based on a predicted outlet temperature and / or predicted outlet flow rate based on a detected inlet temperature and / or detected inlet flow 5 rate enables the controller to control the components (such as valves) in advance of the liquid actually passing through the outlet so that the user experiences better and more responsive hot water provision. The above embodiment is to be understood as an illustrative example. Further embodiments, aspects or examples are envisaged. It is to be understood that any feature 10 described in relation to any one embodiment, aspect or example may be used alone, or in combination with other features described, and may also be used in combination with one or more features of any other of the embodiments, aspects or examples, or any combination of any other of the embodiments, aspects or examples. Furthermore, equivalents and modifications not described above may also be employed without departing from the scope 15 of the invention, which is defined in the accompanying claims.

Claims

1. A domestic hot water provisioning system comprising:a cold water inlet valve for receiving cold water from a mains supply;5 a hot water outlet valve connected for providing hot water on demand to a domestichot water outlet activated by a user;an electric heater located in a first flowpath between the cold water inlet valve and the hot water outlet valve for selectively heating water, the electric heater comprising a plurality of heating elements coupled in parallel, each heating element being coupled in series 10 to a semiconductor switching element for selectively switching the respective heating element to a power source;a thermal storage appliance located in a second flowpath between the cold water inlet valve and the hot water outlet valve for storing water that may be heated;a first valve located in the first flowpath between the electric heater and the hot water 15 outlet valve and in the second flowpath between the thermal storage device and the hot water outlet valve;a second valve located in the second flowpath between the cold water inlet valve and the thermal storage appliance;a manifold comprising a plurality of selectable internal flowpaths between inlets and 20 outlets of the manifold, an inlet of the manifold being coupled to the cold water inlet valve, a first outlet of the manifold being coupled to the first flowpath leading to the electric heater and a second outlet of the manifold being coupled to the second valve, wherein each of the semiconductor switching elements is mounted on the manifold adjacent a predetermined one of the internal flowpaths; and25 a controller coupled to the first valve, to the electric heater via each of thesemiconductor switching elements, and to the manifold for selecting the internal flowpaths through the manifold, the controller controlling operation of the hot water provisioning system in one or more selected operating modes including:a charging mode for charging the thermal storage appliance with hot water;30 anda hot water provisioning mode for providing hot water to the hot water outlet valve from the thermal storage appliance, if the thermal storage appliance has sufficient heat stored therein, or from the electric heater, if the thermal storage appliance does not have sufficient heat stored therein;wherein the controller selects one or more semiconductor switching elements to activate so that the respective one or more heating elements receive power from the power source based on the amount of heating required from the electric heater.5 2. A domestic hot water provisioning system according to claim 1, further comprising:a hot fluid inlet valve for receiving hot fluid from a hot fluid source;a return fluid outlet valve for returning fluid to the hot fluid source;a heat exchanger in the first flowpath between the cold water inlet valve and the electric heater, the heat exchanger having a water inlet connected to receive cold water from10 the cold water inlet valve via the first flowpath, a water outlet connected to output water to the electric heater via the first flowpath, a fluid inlet connected to the hot fluid inlet valve and a fluid outlet connected to the return fluid outlet valve, the heat exchanger selectively heating water between the water inlet and the water outlet using thermal exchange with a hot fluid between the fluid inlet and the fluid outlet;15 wherein the controller is further coupled to the heat exchanger;and wherein the hot water provisioning mode provides hot water to the hot water outlet valve from the heat exchanger, if the heat exchanger is receiving hot fluid from the hot fluid inlet valve.20 3. A domestic hot water provisioning system according to claim 2, wherein:the first flowpath comprises a first flow pipe between the cold water inlet valve and the water inlet of the heat exchanger, a second flow pipe between the water outlet of the heat exchanger and the electric heater, a third flow pipe between the electric heater and the first valve, and a fourth flow pipe between the first valve and the hot water outlet valve; the 25 second flowpath comprises a fifth flow pipe between the cold water inlet valve and the fourth flow pipe;a sixth flow pipe between the thermal storage appliance and the first valve.

4. A domestic hot water provisioning system according to claim 3, wherein the heat 30 exchanger, the electric heater, the thermal storage appliance,, the first, second, third, fourth, fifth and sixth flow pipes, and the controller are mounted within an enclosure comprising an insulating foam material, wherein the cold water inlet valve, the hot water outlet valve, the hot fluid inlet valve, and the return fluid outlet valve are provided at a periphery of the enclosure.

5. A domestic hot water provisioning system according to claim 4, wherein the enclosure has maximum dimensions of 90cm, preferably about 75cm, in height, 60cm, preferably about 45cm, in width and 60cm preferably about 50cm, in depth.

56. A domestic hot water provisioning system according to any one of claims 2 to 5, further comprising a hot fluid source having an outlet coupled to the hot fluid inlet valve and an inlet coupled to the return fluid outlet valve.10 7. A domestic hot water provisioning system according to claim 6, wherein the hot fluidsource is a heat pump.

8. A domestic hot water provisioning system according to claim 7, wherein the heat pump is an air source heat pump.

159. A domestic hot water provisioning system according to any preceding claim, wherein the selection of the one or more semiconductor switching elements is based on a history of use of each of the heating elements so as to try to balance the overall use of each of the heating elements.O 2010. A domestic hot water provisioning system according to any preceding claim, wherein the selection of the one or more semiconductor switching elements is based on a history of use of each of the semiconductor switching elements so as to try to balance the overall use of each of the semiconductor switching elements.2511. A domestic hot water provisioning system according to any preceding claim, wherein the selection of the one or more semiconductor switching elements is repeated so as to cycle the use of the semiconductor switching elements based on the history of use of each of the semiconductor switching elements and / or a detected temperature of one or more previously30 selected semiconductor switching elements so as to try to balance the overall use of each of the heating elements.

12. A domestic hot water provisioning system according to according to any preceding claim, wherein the controller controls the manifold to select an internal flowpathcorresponding to a particular selected operating mode of the hot water provisioning system, each operating mode having an associated known temperature profile of the corresponding internal flowpath within the manifold, and the selection of the one or more semiconductor switching elements is based on the particular selected operating mode, whose corresponding5 internal flowpath has a temperature profilethat provides cooling for the one or more selected semiconductor switching elements located adjacent the corresponding internal flowpath.

13. A domestic hot water provisioning system according to claim 12, wherein the selection of the one or more semiconductor switching elements is repeated so as to cycle the 10 use of the semiconductor switching elements based on a selected operating mode whose corresponding internal flowpath has a temperature profile that provides cooling for the one or more selected semiconductor switching elements located adjacent the corresponding internal flowpath so as to try to balance the overall use of each of the heating elements.15 14. A domestic hot water provisioning system according to any preceding claim, whereinthe electric heater is coupled to a multi-phase power source, a different one of the heating elements being coupled to receive a different phase of power.

15. A domestic hot water provisioning system according to any preceding claim, wherein 20 the manifold is made of a heat conducting material.

16. A domestic hot water provisioning system according to any preceding claim, wherein the semiconductor switching elements comprise solid state devices.25 17. A domestic hot water provisioning system according to claim 16, wherein the solidstate devices comprise any one or more of a diode, a Silicon-controlled rectifier (SCR), a thyristor, a gate turn-off thyristor, a triac, a bipolar junction transistor (BJT), a power MOSFET, an Insulated-gate bipolar transistor (IGBT), a MOS-controlled thyristor (MCT), or an integrated gate-commutated thyristor (IGCT).

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