Water heating system

Abstract

A heating system comprises a heat pump for providing heat to a tank for containing heated water, a tank for containing heated water, a first heat exchanger arranged externally to the tank for transferring heat from the heat pump to water from the tank, and a second heat exchanger for transferring heat from water from the tank to an air flow or to a space heating system. Conduits may provide one or more flow paths from the first heat exchanger to the tank. The heating system is arranged to transfer heat to and from air being ventilated from a building, thereby recovering heat energy that would otherwise be exhausted.

Description

[0001] WATER HEATING SYSTEM

[0002] The present invention relates to a system for heating water, in particular having a heat pump as a heat source and a plate heat exchanger to transfer heat from the heat pump to potable water, with a view to improving efficiency of the heating system.

[0003] Conventional integrated heat pump water cylinders, with a heat pump included within a water cylinder assembly, may be slow to attain a useful temperature. In such systems, a condenser coil typically is wrapped around the inner tank liner within which the potable water is stored. This gradually heats all of the water within the cylinder.

[0004] There is a need for improvements in systems for heating water.

[0005] According to a first aspect there is provided a heating system comprising: an integrated heat pump water tank with a heat pump for providing heat and a tank for containing heated water; a first heat exchanger arranged externally to the tank for transferring heat from the heat pump to water from the tank; a second heat exchanger for transferring heat from water from the tank to a space heating system; and conduits providing one or more flow paths from the first heat exchanger to the tank.

[0006] By virtue of the first and second heat exchangers hot water and space heating can be provided rapidly and efficiently.

[0007] The flow paths from the first heat exchanger to the tank may include a heat mode junction, the heat mode junction having an upper return branch providing a flow path to a top of the tank and a lower return branch providing a flow path to a bottom of the tank. This can enable a heating mode for providing hot water in response to an urgent hot water demand, for instance to be drawn off for use immediately or in the near future. This can enable an alternative or additional heating mode for efficient but slow heating of the water in response to a non-urgent hot water demand.

[0008] The second heat exchanger may be a conduit in thermal contact with heated water inside the tank. The second heat exchanger may be a heat exchange coil for immersion in heated water in the tank. The second heat exchanger may be for transferring heat from water held in the tank to a space heating system. This can be particularly convenient for installation and integration with a space heating system. The tank may further comprise an electrical immersion heating element. This can enable operational resilience. The electrical immersion heating element may be arranged near the second heat exchanger and / or beneath the second heat exchanger. The second heat exchanger may be arranged inside the tank or at a tank wall. The second heat exchanger may be formed of a conduit for only one forced flow. The conduit may be arranged such that heat is transferred across conduit walls from an environment that is not subject to a forced flow.

[0009] For configurational flexibility the second heat exchanger may be arranged externally to the tank. The second heat exchanger may be a plate heat exchanger. The second heat exchanger may be for transferring heat from water drawn from the tank to a space heating system. The second heat exchanger may provide conduits for two forced flows with the conduits arranged such that heat is transferred across conduit walls from one of the flows to the other flow. This can enable rapid provision of heat from the heat pump to a space heating system.

[0010] The flow paths from the first heat exchanger to the tank may further include a space heating junction. The space heating junction may have a space heating branch providing a flow path to the second heat exchanger and a bypass branch providing a flow path bypassing the second heat exchanger.

[0011] The heating system may comprise a first three-port valve at the heat mode junction. The heating system may comprise a second three-port valve at the space heating junction. The first and / or second three-port valve is preferably controllable by a controller. The first and / or second three-port valve may be electronically controllable.

[0012] The heating system may comprise a pump in the space heating branch, preferably a variable speed pump.

[0013] The heating system may further comprise a non-return valve arranged to prevent water flow from an upper portion of the tank to a lower portion of the tank via the conduits. The heating system may comprise a non-return valve in a conduit providing a flow path from a bottom part of the tank to the first heat exchanger. The heating system may comprise a non-return valve in the space heating branch.

[0014] The heat mode junction may be upstream of the space heating junction. The space heating branch may feed into the lower return branch.

[0015] The space heating junction may be upstream of the heat mode junction. The space heating branch may feed into the bypass branch upstream of the heat mode junction. The space heating branch may feed into the lower return branch. The space heating branch may feed into a conduit providing a flow path from a bottom part of the tank to the first heat exchanger.

[0016] The space heating junction may be upstream of the heat mode junction with the space heating branch comprising a pump, preferably a variable speed pump, and optionally a non-return valve, and with the space heating branch feeding into a conduit providing a flow path from a bottom part of the tank to the first heat exchanger.

[0017] The heating system may comprise a first and second blanked port for receiving a conduit to provide the space heating branch with the second heat exchanger and a pump and optionally a non-return valve.

[0018] The heating system may further comprise a thermal sensor arranged to sense a temperature distribution in the tank. The thermal sensor is preferably an array of temperature sensors arranged to sense temperatures at different heights of the tank.

[0019] The tank may further comprise an electrical immersion heating element arranged in the tank. The electrical immersion heating element is preferably arranged in an upper portion of the tank.

[0020] The heat pump and the tank and optionally the first heat exchanger may be contained in a common housing or share a common fascia or may be fixedly attached to one another. The heat pump may be arranged above the tank in use. The integrated heat pump water tank may be modular with a heat pump module and a tank module. The integrated heat pump water tank may comprise the first heat exchanger, and optionally the second heat exchanger. The heat pump and the first heat exchanger may be contained in a common housing or share a common fascia or may be fixedly attached to one another. The heat pump and the second heat exchanger may be contained in a common housing or share a common fascia or may be fixedly attached to one another. The integrated heat pump water tank may comprise the pump or pumps, the three-way valve or three-way valves, the heat exchanger or heat exchanger, the non-return valve or valves, the thermal sensor and / or a portion of the conduits. The pump or pumps, the three-way valve or three-way valves, the heat exchanger or heat exchanger, the non-return valve or valves, the thermal sensor, and / or a portion of the conduits may be attached to the integrated heat pump water tank. The pump or pumps, the three-way valve or three-way valves, the heat exchanger or heat exchanger, the non-return valve or valves, the thermal sensor, and / or a portion of the conduits may be connected to the integrated heat pump water tank without the integrated heat pump water tank bearing these components.

[0021] The conduits may provide a flow path from a portion of the tank via the first heat exchanger back to the tank. The conduits may provide a flow path external to the tank. A pump, preferably a variable speed pump, may be arranged to pump water through the conduits. The conduits may provide a flow path external to the tank from a lower portion of the tank to the first heat exchanger. The heating system may further comprise a third heat exchanger for transferring heat from heat from water from the tank to the space heating system. The second heat exchanger may be a conduit in thermal contact with heated water inside the tank. The third heat exchanger may be arranged externally to the tank. The third heat exchanger may be a plate heat exchanger The first three-port valve at the heat mode junction may be controllable to block flow from the first heat exchanger to the heat mode junction. The third heat exchanger may permit both a rapid space heating mode and a slower heating mode using energy already buffered in the heating system.

[0022] The space heating system may comprise an electric heater.

[0023] The second heat exchanger may be located in a central or lower portion of the tank. This may improve the efficiency of the heating system by providing heat to the space heating system at a lower temperature, thereby allowing the heat pump to operate at a higher coefficient of performance as it delivers heat at a lower temperature. This can enable establishment of an upper zone in the tank with hotter water for drawing off e.g. for domestic hot water supply; and a lower zone beneath the upper zone, also with hot water but at a lower temperature, for supply of heat to the space heating system.

[0024] The second heat exchanger may be located within the tank such that a volume in the tank at or above the second heat exchanger (or above a lower end of the second heat exchanger) is at least the volume of the largest expected hot water draw event. This may ensure that the second heat exchanger remains surrounded by cooler water, maximising the rate of heat transfer from the second heat exchanger to the water in the tank.

[0025] The largest expected hot water draw event may be the volume of water drawn from the tank in a single, continuous discharge, or may be the volume of water drawn over a series of successive discharges. In the latter instance, the volume and frequency of the discharges may be sufficiently high to remove a significant quantity of heat from the tank that cannot be quickly replenished by a heat source, leading to a reduction in the amount of energy stored in the tank.

[0026] A bypass valve may be coupled between the space heating system and the second heat exchanger. The bypass valve may be arranged to prevent the heat transfer fluid from flowing between the space heating system and the second heat exchanger when the space heating system is used with an electric heater. This may increase the efficiency of the heating system by reducing unnecessary heat transfer.

[0027] The system may comprise a controller configured to select a flow path in dependence on a heat demand. The controller may be configured to provide a flow path to the space heating branch in response to a space heating demand. The controller may be configured to provide a flow path to the upper return branch in response to an urgent hot water demand. The controller may be configured to provide a flow path to the lower return branch in response to a non-urgent hot water demand. The controller may be configured to actuate flow in the second heat exchanger.

[0028] The controller may be configured to provide a flow path in dependence on a temperature distribution in the tank.

[0029] The controller may be configured to control one or more pumps, one or more three-way valves, the heat pump, and / or one or more electrical immersion heating elements. The controller may be configured to receive input from a thermal sensor.

[0030] The controller may be configured to control the electrical immersion heating elements to ensure the second heat exchanger is able to deliver heat to the space heating system. The thermal sensor may provide information to the controller to determine the location of a thermocline within the tank, and the controller may further control the power sent to one or more electrical immersion heating elements to control the location of the thermocline.

[0031] The system may further comprise a ventilation system configured to route air to and from the heat pump. The controller may be configured to select an airflow path in the ventilation system in dependence on one or more temperature sensors and / or humidity sensors in the ventilation system. The ventilation system preferably comprises air conduits to one or more rooms in a home. The ventilation system may comprise one or more air conduits to a building exterior. The ventilation system preferably comprises means of causing air flow in the air conduits.

[0032] The system may further comprise an external heat exchanger arranged outside a building. The controller may be configured to provide heat to the external heat exchanger in dependence on a demand for air conditioning.

[0033] The conduits providing one or more flow paths from the first heat exchanger to the tank may be substantially inside the tank, preferably for immersion in water in the tank. Advantageously this may reduce the complexity of the integrated heat pump hot water tank and may reduce the chance of leaks occurring from the hot water tank. The conduits providing one or more flow paths from the first heat exchanger to the tank may be substantially outside the tank. Advantageously this may permit ease of access to the conduits and ease of repair and adaptation. The conduits providing one or more flow paths from the tank to the first heat exchanger may be substantially inside the tank, preferably for immersion in water in the tank. The conduits providing one or more flow paths from the tank to the first heat exchanger may be substantially outside the tank. The system may comprise a further heat exchanger for transferring heat from water from the tank to an air flow. The system may comprise conduits providing one or more flow paths from the first heat exchanger to an air conditioning junction. The air conditioning junction may have an air conditioning branch providing a flow path to the second heat exchanger. The air conditioning junction may have a bypass branch providing a flow path returning water to the tank.

[0034] The system may further comprise a space heating system for providing space heating. The controller may be configured to control the space heating system in dependence on a demand for space heating. The space heating system may comprise a conduit providing a flow path for a heat transfer fluid for transporting heat, a pump (preferably a variable speed pump) for pumping heat transfer fluid in the conduit, and a number of space heating elements such as radiators or underfloor heating conduits for providing space heating to a user. The space heating system may comprise a heat source junction. The heat source junction may have a first branch providing a flow path to the second heat exchanger and a second branch bypassing the second heat exchanger. The space heating system may further comprise a three-port valve at the heat source junction. The controller may be configured to control the pump, preferably to cause the pump to pump, to stop the pump from pumping, or to modify a pump rate of the pump. The controller may be configured to control the three-port valve at the heat source junction.

[0035] The space heating system may comprise an electric heater. The electric heater may be arranged to heat the heat transfer fluid. The electric heater may be in a flow path for a heat transfer fluid of the space heating system. The electric heater may be arranged downstream of the pump and / or downstream of the second heat exchanger. The electric heater may be arranged away from the hot water tank, for instance integrated into the space heating system flow path near a location where heat is transferred to the space. The controller may be configured to control the electric heater.

[0036] According to another aspect there is provided a heating system comprising: an integrated heat pump water tank with a heat pump for providing heat and a tank for containing heated water; a first heat exchanger arranged externally to the tank for transferring heat from the heat pump to water from the tank; conduits providing flow paths from the first heat exchanger to the tank, the flow paths including: a heat mode junction, the heat mode junction having an upper return branch providing a flow path to a top of the tank and a lower return branch providing a flow path to a bottom of the tank; and a space heating junction having a space heating branch for providing a flow path to the second heat exchanger and a bypass branch providing a flow path for bypassing the second heat exchanger; a first blanked port and a second blanked port for receiving a conduit to provide the space heating branch with a second heat exchanger and a pump and optionally a non-return valve.

[0037] The second heat exchanger is preferably a plate heat exchanger, preferably for transferring heat from water from the tank to a space heating system, preferably for arrangement external to the tank.

[0038] The first blanked port may cap the space heating branch. The second blanked port may be for feeding the space heating branch into a conduit providing a flow path from a bottom part of the tank to the first heat exchanger.

[0039] According to another aspect there is provided a heating system comprising: a heat pump for providing heat to a tank for containing heated water; a tank for containing heated water; a first heat exchanger arranged externally to the tank for transferring heat from the heat pump to water from the tank; and a second heat exchanger for transferring heat from water from the tank to an air flow.

[0040] The air flow may be an exchange between air within a building, and air external to the building. The air flow may be external air entering the building, or internal air leaving the building. The heating system therefore exchanges heat with an airflow moving between the inside and outside of a building.

[0041] By virtue of the first and second heat exchangers hot water and space heating or cooling can be provided rapidly and efficiently.

[0042] The system may comprise conduits providing one or more flow paths from the tank to the first heat exchanger and to an air conditioning junction. The air conditioning junction may have an air conditioning branch providing a flow path to the second heat exchanger. The air conditioning junction may have a bypass branch providing a flow path returning water to the tank.

[0043] For providing cooled air from the heat pump to the interior the second heat exchanger may be arranged to transfer excess heat to a flow of exhaust air to the outside of a building. For providing space heating the second heat exchanger may be arranged to transfer heat to a flow of intake air to the interior of a building.

[0044] For providing cooling and heating to the interior the system may further comprise a third heat exchanger for transferring heat from water from the tank to an air flow. The second heat exchanger may be arranged to transfer excess heat to a flow of exhaust air to an exterior of a building and the third heat exchanger may be arranged to transfer heat to a flow of intake air to an interior of a building.

[0045] For avoidance of thermal losses the system may comprise a heat recovery system with a heat recovery heat exchanger for transferring heat between a flow of exhaust air to an exterior of a building and a flow of intake air to an interior of a building.

[0046] For efficient use of airflow conduits the heat recovery system may comprise a bypass duct for diverting intake air from an exterior of the building to the heat pump.

[0047] The heat recovery system may further comprise an air duct arranged to provide air from an interior of the building to the heat pump. The heat recovery system may be configured to sense an interior space with a high air temperature and / or a high air humidity. The heat recovery system may be configured to provide air from an interior space with high air temperature and / or air humidity to the heat pump. The heat recovery system may be configured to provide air from a kitchen and / or a bathroom to the heat pump.

[0048] For efficient use of airflow conduits the system may further comprise an air duct arranged to provide air from the heat pump to an interior of the building. The system may further comprise an air duct arranged to provide air from the heat pump to a junction in a flow of exhaust air from the heat recovery heat exchanger to an exterior of a building.

[0049] For efficient control of an operation mode the system may comprise means for selecting a flow path for water from the tank. The means for selecting a flow path for water from the tank may be one or more pumps in one or more sections or branches of the flow path. The means for selecting a flow path for water from the tank may be one or more valves at one or more junctions of the flow path.

[0050] For efficient control of an operation mode the system may comprise means for selecting an air flow path to and from the heat pump. The means for selecting an air flow path to and from the heat pump may be one or more fans in one or more sections or branches of the air flow path. The means for selecting an air flow path to and from the heat pump may be one or more diverters at one or more junctions of the air flow path. The heat recovery heat exchanger may be a Mechanically Ventilated Heat Recovery (MVHR) device. This device may comprise a primary and secondary side in which heat transfer occurs between the two sides. Each side of the MVHR may comprises at least one conduit arranged to carry airflow through the MVHR.

[0051] The MVHR may further comprise a plenum comprising a plurality of apertures, each aperture configured to connect to a duct for carrying airflow. This may allow the MVHR to intake and exhaust air from a number of different sources.

[0052] The choice of source for intake air to the MVHR may be determined in part on the calculated enthalpy of the intake air. The enthalpy may be calculated by determining the temperature, humidity and / or pressure of the air.

[0053] The system may be configured to provide heat to an interior space. The system may be configured to remove heat from an interior space. Advantageously this may provide greater flexibility of the system as it can be used both to cool and heat a heated space.

[0054] The system may be configured to transfer heat removed from an interior space to water from the tank. Advantageously this increases the overall efficiency of the system by increasing the quantity of heat retained in the system and minimising heat lost to the atmosphere. The system may be configured to transfer heat removed from an interior space to a flow of exhaust air to the outside of a building.

[0055] The heat pump and tank for containing heated water may be an integrated heat pump as aforementioned. This may make the system more compact and convenient to install in a building.

[0056] The system or components or features of the system may be as aforementioned.

[0057] According to another aspect there is provided a controller for a system as aforementioned. The controller may be configured to control the means for selecting a flow path for water from the tank. The controller may be configured to control the means for selecting an air flow path to and from the heat pump.

[0058] According to another aspect there is provided a heating system comprising: an integrated heat pump water tank with a heat pump for providing heat and a tank for containing heated water; a first heat exchanger arranged at or in the tank for transferring heat from the heat pump to water in the tank; and a second heat exchanger for transferring heat from water from the tank to a space heating system.

[0059] Advantageously this may simplify the system and may reduce the number of potential leak points in the tank for containing heated water. The first heat exchanger may be arranged at a wall of the tank and / or inside the tank. The first heat exchanger is conduit in thermal contact with heated water inside the tank.

[0060] The heating system or components or features of the heating system may be as aforementioned.

[0061] According to another aspect there is provided a heating system comprising: a heat pump for providing heat to a tank for containing heated water; a tank for containing heated water; a first heat exchanger (optionally arranged externally to the tank) for transferring heat from the heat pump to water from the tank; and a second heat exchanger for transferring heat from water from the tank to an air flow or to a space heating system. The system may comprise conduits providing one or more flow paths from the first heat exchanger to the tank. The system may comprise conduits providing one or more flow paths from the first heat exchanger to the second heat exchanger. The system may comprise one or more further heat exchangers.

[0062] The heating system or components or features of the heating system may be as aforementioned.

[0063] According to an aspect described herein, there is provided a heating system, preferably a potable water heating system, comprising one of more of following features:

[0064] • a heat-pump

[0065] • a tank for containing heated water

[0066] • a first heat exchanger, preferably a plate heat exchanger

[0067] • one or more circulation pumps, preferably variable speed pump(s)

[0068] • an alternate flow path downstream of the heat exchanger

[0069] • one or more configurable three-port valves (e.g. T valves) arranged to provide an alternate flow path downstream of the first heat exchanger

[0070] • a heat recovery heat exchanger for transferring heat between two airflows

[0071] The heating system or features of the heating system may further be as aforementioned.

[0072] Any apparatus feature as described herein may also be provided as a method feature, and vice versa.

[0073] Any feature in one aspect of the invention may be applied to other aspects of the invention, in any appropriate combination. In particular, method aspects may be applied to apparatus aspects, and vice versa. Furthermore, any, some and / or all features in one aspect can be applied to any, some and / or all features in any other aspect, in any appropriate combination. It should also be appreciated that particular combinations of the various features described and defined in any aspects of the invention can be implemented and / or supplied and / or used independently.

[0074] These and other aspects of the present invention will become apparent from the following exemplary embodiments that are described with reference to the following figures in which:

[0075] Figure 1 is a schematic of a heating system for use with a space heating system;

[0076] Figure 2 is a schematic of another heating system for use with a space heating system;

[0077] Figure 3 is a schematic of another heating system for use with a space heating system;

[0078] Figure 4 is a schematic of a heating system including a controller and sensors;

[0079] Figure 5 is a schematic of another heating system for use with a space heating system;

[0080] Figure 6 is a schematic of a heating system for retrofit to form the heating system of Figure 5;

[0081] Figure 7 is a schematic of a heating system including a controller and sensors;

[0082] Figure 8 is a schematic of a heating system including a controller and sensors;

[0083] Figure 9 is a schematic of a heating system including a controller and sensors;

[0084] Figure 10 is a schematic of a heating system including a controller and sensors;

[0085] Figure 11 is a schematic of a heating system for use with a space heating system;

[0086] Figure 12a is a heating system comprising a hot water tank, a mechanically ventilated heat recovery device, and other periphery devices;

[0087] Figure 12b is the heating system of figure 12a in another configuration;

[0088] Figure 13 is another heating system comprising a hot water tank, a mechanically ventilated heat recovery device, and other periphery devices;

[0089] Figure 14a is a schematic of a heating system for use with a space heating system;

[0090] Figure 14b is another view of the heating system of figure 14b;

[0091] Figure 15 is a view of some of the details of the heating system of figure 14b;

[0092] Figure 16 is another view of some of the details of the heating system of figure 14b; and

[0093] Figure 17 is a schematic of a heating system for use with a space heating system. Figure 1 shows a heating system 300 with an integrated heat pump water tank. A heat pump 12 is included within the water cylinder assembly. The heat pump 12 is arranged above the tank 2 in use. The tank 2 has a cold water inlet 4 for introducing water and a hot water outlet 6 for drawing off hot water. The heat pump 12 has an air intake 11 and an air outlet 15.

[0094] Heat is provided from the heat pump 12 to water in the tank 2. For this purpose cold water is drawn from the bottom of the tank 2 by a pump 8 and passed through a first heat exchanger 10 and returned to the tank 2. The first heat exchanger 10 is external to the tank, and is for instance a plate heat exchanger. The first heat exchanger 10 receives heat from the heat pump 12 and provides heat to the water drawn from the tank 2. In some scenarios the first heat exchanger can instead receive heat from the water drawn from the tank 2 and provide it to the heat pump 12, for instance for defrosting the heat pump.

[0095] A heating mode junction with a three-port valve 20 is arranged downstream of the first heat exchanger 10. The first three-port valve 20 can direct the flow either to an upper return branch 3 to the top of the tank 2, or to a lower return branch 5 to a bottom region of the tank 2. This can permit different heating schemes depending on availability of heat and hot water to be provided. For instance, a portion of water can be heated to a high temperature with a relatively low flow rate through the first heat exchanger returned to the top of the tank for providing hot water in response to an urgent hot water demand, for instance to be drawn off for use immediately or in the near future. Alternatively or in addition the bulk of the water can undergo more efficient gradual heating with higher flow rates and return to the bottom of the tank 2. Returning water to the bottom of the tank can enable particularly efficient but slow heating of the water in response to a non-urgent hot water demand, whereas returning water to the top of the tank can enable more rapid but less efficient heating of the water in response to a nonurgent hot water demand.

[0096] A second heat exchanger, in the illustrated example a heat exchange coil 340, is immersed in the tank 2. The heat exchange coil 340 can receive heat from the water in the tank and provide it to an external space heating system 110. For efficient heat transfer the heat transfer fluid from the space heating system enters the heat exchange coil 340 at a lower end and flows out of the heat exchange coil 340 at an upper end. In some examples the heat exchange coil 340 is not immersed in the tank 2, but instead is mounted external to the tank but coiled around a tank wall and in sufficiently close contact with the tank to permit heat transfer.

[0097] The space heating system 110 generally includes a circuit of heat transfer fluid for transporting heat, a pump for pumping heat transfer fluid in the circuit, and a number of elements such as radiators or underfloor heating conduits for providing space heating to a user, for instance in a dwelling. A controller can switch the pump in the space heating system on or off in order to enable or suspend space heating. The controller can increase flow rate in the space heating system, for instance to increase heat transfer efficiency or for rapid space heating.

[0098] A thermal sensor 14 is arranged to sense a temperature distribution in the tank 2. This can permit determination of the quantity of thermal energy stored in the tank. A controller can use this information for nuanced control of how heat is provided to the tank, and whether heat is available for space heating, for drawing off hot water, for both, or for neither. The thermal sensor 14 is typically an array of temperature sensors arranged to sense temperatures at different heights of the tank. This can enable particularly efficient and favourable resolution of temperature distribution in the tank. The thermal sensor 14 may for instance be fixed to an outer surface of the tank or immersed inside the tank. An array of temperature sensors may be arrayed at different heights along the tank, e.g. vertically along the wall of the water tank or inside the tank, such that the array of sensors detects the temperature of the water in the tank at a plurality of heights. This may be used to determine a heat profile characterising how the temperature of the water in the water tank varies with height. The vertical temperature distribution is particularly informative, as due to thermal stratification in the tank horizontal temperature distributions are typically less significant. Other means of determining a temperature distribution of water in the tank may be used alternatively or additionally. For instance, the thermal sensor 14 may include as few as one temperature sensor and inference of a temperature distribution from a model of temperature distribution in the tank. Inferring a temperature distribution from a model of temperature in a tank can be improved with measurements such as a flow rate measurement of water into and / or out of the tank and temperature data from outside the tank, such as at a cold inlet and at a hot inlet. Other means of determining a temperature distribution of water in the tank may include thermal imaging or density sensing or other suitable techniques.

[0099] The first heat exchanger 10 and the heat pump 12 are arranged in a heat pump unit 13 above the tank 2. This is particularly convenient as it can permit particularly compact integration of the heat pump with the first heat exchanger 10 and the tank 2. This is discussed in more depth below. In other examples the three-port valve 20 is arranged with the heat pump 12 above the tank 2, with or without the first heat exchanger 10.

[0100] An electrical immersion heating element 22 is provided in the tank (also referred to as electrical immersion heater). The heating element 22 is a simple resistive heater that can increase the temperature of the water in the tank when provided with electrical power. The heating element 22 can rapidly heat a portion of water in the tank to a high temperature to provide immediate hot water in situations where the heat pump is unable to satisfy a heat demand. The heating element 22 is near the heat exchange coil 340 and beneath it, so that it can heat a portion of the water in the tank in the region of the heat exchange coil 340 to a relatively high temperature for rapid availability of heat for space heating. Use of the heating element 22 as heat source is generally less efficient than use of the heat pump, but it can enable flexibility in situations where not enough heat is available in the tank to satisfy a space heating demand, possibly due to a concurrent hot water demand.

[0101] A baffle 16 is arranged inside the tank 2. The baffle 16 is arranged to promote stratification in the tank 2. The baffle 16 has apertures to permit flow across it, but it also includes portions to deflect flow and inhibit excessive mixing within the tank. A typical baffle 16 is plate-shaped and extends over a horizontal cross section area of the tank 2, but many suitable geometries and arrangements are conceivable; for example a baffle may extend over only a portion of a horizontal cross section area of the tank 2 and may be formed elsewise than a horizontal plate. In the illustrated example the baffle 16 is arranged in a lower region of the tank, generally around a middle height of the tank 2 or in a lower half of the tank, but it can also be provided elsewhere in the tank 2. Fluid flows into and out of the tank can cause undesired convective flows inside the tank, and the baffle can serve to obstruct and reduce such convection. Hence the baffle is typically provided between a section of the tank where in-and outflows are expected and a region of a tank where thermal stratification is to be promoted. Inclusion of a baffle 16 can improve performance of the heating system by virtue of promoting stratification. A baffle can be included in any of the examples described and illustrated herein. Two or more baffles may be included in a tank at different heights.

[0102] In many conventional integrated heat pump water cylinders heat is provided to the water by other means, for example by a heating coil immersed into the tank or arranged around the tank wall for a separate circuit of heat transfer fluid. The system where water is drawn from the tank and heated external to the tank provides a number of advantages. The heat exchanger has a relatively low thermal mass, so it can enable particularly a fast response for provision of hot water. External heating can also be more versatile and convenient as components can be accessed, maintained, and adjusted to a user’s requirements more easily. In some examples a tank has an immersed heat exchange coil that was originally intended for providing heat to the tank. By repurposing the immersed heat exchange coil for space heating instead of for providing heat to the tank efficient use of such a tank can be enabled.

[0103] In an example the heat pump 12 provides heat transfer fluid to the first heat exchanger 10 at approximately 65 °C, and the water in the tank 2 is to be heated to a temperature suitable for use, e.g. 62 °C (typically above 50 °C to minimise the risk of exposure to Legionella or other pathogens, and below 70 °C to minimise the risk of scalding). An optional non-return valve 18 may be arranged in the water flow path to prevent water flow from the upper portion of the tank back to the lower portion of the tank via the conduit. This can help prevent unintended flows due to hydrostatic equilibrium under the influence of heat loss of the water outside the tank.

[0104] The conduit for drawing water from the bottom of the tank 2 is typically outside the tank 2, and outside the thermal insulation around the tank 2. Such conduits may have their own thermal insulation. In some examples the conduit may be embedded in the thermal insulation around the tank 2.

[0105] In the illustrated examples the heat pump 12 is arranged above the tank. This is particularly convenient as it can permit particularly compact integration of the heat pump with the tank, avoiding an increase of footprint in side-by-side arrangements or weightbearing elements if the (heavy) tank is above the heat pump.

[0106] Figure 2 shows another heating system 50 with an integrated heat pump water tank, where the second heat exchanger is external to the tank instead of immersed in the tank. The heating system 50 includes many of the same features as the heating system 300 discussed with reference to Figure 1. Instead of the second heat exchanger being a heat exchange coil 340 immersed in the tank 2, in the heating system 50 the second heat exchanger is a heat exchanger such as a plate heat exchanger arranged external to the tank.

[0107] In the heating system 50 a heat pump 12 is included within the water cylinder assembly. The heat pump 12 is arranged above the tank 2 in use. The tank 2 has a cold water inlet 4 for introducing water and a hot water outlet 6 for drawing off hot water. The heat pump 12 has an air intake 11 and an air outlet 15.

[0108] Heat is provided from the heat pump 12 to water of the tank 2. For this purpose cold water is drawn from the bottom of the tank 2 by a pump 8 and passed through a first heat exchanger 10 and returned to the tank 2. The first heat exchanger 10 is external to the tank, and is for instance a plate heat exchanger. The first heat exchanger 10 receives heat from the heat pump 12 and provides heat to the water drawn from the tank 2. In some scenarios the first heat exchanger can instead receive heat from the water drawn from the tank 2 and provide it to the heat pump 12, for instance for defrosting the heat pump.

[0109] A heating mode junction with a first three-port valve 20 is arranged downstream of the first heat exchanger 10. The first three-port valve 20 can direct the flow either to an upper return branch 3 to the top of the tank 2, or to a lower return branch 5 to a bottom region of the tank 2. This can permit different heating schemes depending on availability of heat and hot water to be provided. For instance, a portion of water can be heated to a high temperature with a relatively low flow rate through the first heat exchanger returned to the top of the tank for providing hot water to be drawn off for use immediately or in the near future. Alternatively or in addition the bulk of the water can undergo more efficient gradual heating with higher flow rates and return to the bottom of the tank 2. Returning water to the bottom of the tank can enable particularly efficient but slow heating of the water, whereas returning water to the top of the tank can enable more rapid but less efficient heating of the water.

[0110] A space heating junction with the second three-port valve 30 is arranged in the upper return branch 3 downstream of the first heat exchanger 10. The second three-port valve 30 can divert the water to a space heating branch 7 with a second heat exchanger 40, or it can permit the water to continue on to a bypass branch 9 bypassing the second heat exchanger 40 and instead completing the flow path to the top of the tank 2.

[0111] The second heat exchanger 40, for instance a plate heat exchanger, is arranged external to the tank. At the second heat exchanger 40 heat is received from the water from the tank and provided to a space heating system 110. In some scenarios the second heat exchanger 40 can instead receive heat from the space heating system 110 and provide it to the water drawn from the tank 2.

[0112] The system where water is drawn from the tank and heated external to the tank provides a number of advantages; for example tank manufacture is straightforward because all the tank needs is suitable ports for connection to conduits, and not a heating coil arranged inside the tank. In unvented hot water cylinders for containing mains pressurised water, where the tank must be manufactured to withstand the pressure and temperature conditions, it can be especially convenient to enable straightforward manufacture.

[0113] Figure 3 shows a heating system 100 that is a variant of the heating system 50 described with reference to Figure 2. In this variant, the space heating junction with the second three-port valve 30 is arranged downstream of the first heat exchanger 10 and upstream of the heating mode junction with the first three-port valve 20. The second three-port valve 30 can direct the water either to a second heat exchanger 40 or to a bypass conduit 9 bypassing the second heat exchanger 40 and instead directing the water to the heating mode junction with a first three-port valve 20.

[0114] An example of a space heating system 110 is illustrated in more detail, with a circuit 112 of heat transfer fluid for transporting heat, a pump 114 for pumping heat transfer fluid in the circuit 112, and a number of elements 116 such as radiators or underfloor heating conduits for providing space heating to a user, for instance in a dwelling. In some scenarios the second heat exchanger 40 can instead receive heat from the space heating system 110 and provide it to the water drawn from the tank 2. The heating mode junction with the first three-port valve 20 is arranged downstream of the space heating junction with the second three-port valve 30. The first three-port valve 20 can direct the flow either to the upper return branch 3 to the top of the tank 2, or to the lower return branch 5 to a bottom region of the tank 2. This can permit different heating schemes depending on availability of heat and hot water to be provided. For instance, a portion of water can be heated to a high temperature with a relatively low flow rate through the first heat exchanger returned to the top of the tank for providing hot water to be drawn off for use immediately or in the near future. Alternatively or in addition the bulk of the water can undergo more efficient gradual heating with higher flow rates and return to the bottom of the tank 2. Returning water to the bottom of the tank can enable particularly efficient but slow heating of the water, whereas returning water to the top of the tank can enable more rapid but less efficient heating of the water.

[0115] An optional electrical immersion heating element 22 may be provided for instance in an upper region of the tank. The heating element 22 can rapidly heat a portion of water in the tank to a high temperature to provide immediate hot water in situations where the heat pump is unable to satisfy a heat demand. The heating element 22 is provided in an upper portion of the tank 2 so that it can heat a relatively small portion of the water in the tank to a relatively high temperature for rapid availability. Use of the heating element 22 as heat source is generally less efficient than use of the heat pump.

[0116] Figure 4 shows the heating system 300 with a controller 200 and a thermal sensor 14, with dashed lines indicating communication between the controller and other components of the heating system. Communication may be via a physical connection, e.g. with a wire carrying an electrical signal, or it may be via a contactless or wireless communication. Power may be suitably provided to the components.

[0117] The controller 200 may control the heat pump 12, or it may liaise with a separate heat pump controller to coordinate control of the heat pump 12. The controller 200 may control the pump 8 drawing water from the tank switching on or off as well as in the case of a variable speed pump controlling the pump rate. The controller 200 may control the three-port valve 20 to select between different flow paths in order to provide a fast heating mode or an energy efficient heating mode. The controller 200 may control the space heating system 110, for instance switching a pump for heat transfer fluid in the space heating system 110 on or off, or adjusting flow rate to modulate the heat transfer rate to the space heating system. The controller 200 may control the heating element 22.

[0118] The controller 200 can determine a heat availability in the tank from the thermal sensor 14. In response to a user demand for hot water or space heating (e.g. scheduled, predicted or ad hoc) the controller can determine heat availability and establish flow in a suitable flow path to achieve a desired heating result (e.g. space heating, quick immediate heating, or gradual efficient heating). In the example illustrated in figure 4 for instance, the controller 200 can, can take one of several possible responses including:

[0119] • actuate the pump 8, the heat pump 12, and the first three-port valve to enable flow in the upper return branch to provide a portion of heated water rapidly to the top of the tank;

[0120] • actuate the pump 8, the heat pump 12, and the first three-port valve to enable flow in the lower return branch to for gradually heating the bulk of the water in the tank;

[0121] • actuate the heating element 22 to provide a portion of heated water rapidly to the second heat exchanger 340 for space heating; and

[0122] • actuate the space heating system 110 to enable provision of space heating.

[0123] Sensors are also generally provided in the heating system for monitoring properties of the system. Data from sensors including the thermal sensor may be transmitted to the controller. The controller may be configured to determine a temperature profile of the tank 2 from the temperature sensor data. The controller may thus determine whether there is sufficient hot water in the tank 2 to satisfy a user hot water demand or heat demand.

[0124] While the examples described above include one or two three-port valves for selection of a flow path, alternative arrangements can be used in place of a three-port valve for selection of a flow path, for instance by way of pumps in a branch that can be activated or switched off for selection of one or the other branch.

[0125] Figure 5 shows a heating system 400 with two pumps 8, 408 for selection of a flow path. The heating system 400 includes many of the same features as the heating system 100 discussed with reference to Figure 3. Instead of the space heating branch being actuated by setting of the second three-port valve 30, a second pump 408 is included, namely in the space heating branch 7.

[0126] In this system the space heating junction is arranged downstream of the first heat exchanger 10 and upstream of the heating mode junction. A pump 408 is arranged in the space heating branch 7, in the illustrated example between the space heating junction and the second heat exchanger 40. The space heating branch 9 feeds into the conduit upstream of the first heat exchanger 10.

[0127] While the pumps 8, 408 may be able prevent flow when they are switched off, it may be beneficial to include one or more non-return valve as well to prevent unintended flows under the influence of one or the other pump 8, 408. A non-return valve 418 is shown in the space heating branch 7, in the illustrated example downstream of the second heat exchanger 40. The non-return valve 418 can prevent water from flowing into the space heating branch 7 when the pump 8 is drawing water from the bottom of the tank. Another non-return valve 18 is shown in the conduit drawing water from the tank to further prevent water from being pumped into the bottom of the tank by the pump 408. A non-return valve (not shown) can be included in the bypass branch 9 to prevent water from being pumped into the bypass branch 9 under the influence of the pump 408.

[0128] In this heating system, in a first mode the pump 8 draws water from the bottom of the tank, provides it to the first heat exchanger. The second pump 408 is off and water is prevented from entering the space heating branch 7. Instead the water flows to the heating mode junction, where suitable actuation of the first three-port valve 20 permits selection of the upper or lower return branch. In this mode the heat pump provides heat to heat water in the tank.

[0129] In a second mode the pump 8 is off and water is prevented from being drawn from the bottom of the tank. Instead the second pump 408 is on, and the water circulates in a loop from the first heat exchanger 10 to the second heat exchanger 40 and back to the first heat exchanger 10. In this mode heat from the heat pump is provided to the space heating system.

[0130] The heating system 400 can be particularly convenient for retrofitting.

[0131] Figure 6 shows a heating system with two blocked ports 420 where the space heating branch 7 can be conveniently attached to form the heating system 400 described with reference to Figure 5. This can permit the system to be adapted for provision of heat to a space heating system at a later date.

[0132] Figure 7 shows the heating system 400 described with reference to Figure 5 in more detail including the controller 200 with dashed lines indicating communication links (described with reference to Figure 4) and the space heating system 110 (described with reference to Figure 3). In addition to components described above, the illustrated example includes:

[0133] • a ventilation system 1115 that is controlled by the controller 200 to manage air circulation to and from the heat pump;

[0134] • an outdoor heat exchanger 118 that is outside a building external wall 120 and connected to the space heating system via a controllable valve 122; opening a flow path to the outdoor heat exchanger 118 can facilitates thermal dissipation outdoors where extended air conditioning is required;

[0135] The ventilation system 1115 is such that it can route, under the control of the controller, air flows to and from the heat pump as follows: • air intake can be routed from a room with high enthalpy (i.e. a shower room) where a temperature and or humidity sensor indicates an air extraction requirement which can provide useful thermal energy to the heat pump;

[0136] • air intake can be routed from outdoors when there is no available thermal energy to scavenge from within the home;

[0137] • the outlet air flow can be routed to rooms in the home for space cooling; or

[0138] • the outlet air flow can be routed to the outdoors when no space cooling is required.

[0139] Figure 8 shows the heating system 300 described with reference to Figure 1 in more detail including the controller 200 and the space heating system 110 and other components described above.

[0140] Figure 9 shows a heating system 500 including many of the same feature as the heating system 300 discussed with reference to figure 3. The heating system 500 comprises a third heat exchanger 502 mounted externally to the tank 2 and configured to exchange heat between the first heat exchanger 10 and the space heating system 110. The space heating system 110 fluid circuit typically operates at a lower temperature (e.g. 30, 40, 45°C) than the temperature of the hot water in the tank 2 (50°C or more, to prevent Legionella or similar bacterial growth). In some circumstances a larger temperature difference (AT) exists between the heat transfer fluid in the space heating system and the heat pump than between the water from the tank and the heat pump. At the heat exchanger a larger temperature difference can permit more effective heat transfer. In order to take advantage of the lower temperature at the space heating system the example illustrated in Figure 9 includes a second heat exchanger immersed in the tank as described with reference to Figure 1 , as well as a third heat exchanger 502 external to the tank.

[0141] The third heat exchanger 502 is arranged to take heat directly from the first heat exchanger 10 and exchange it with the space heating system 110 fluid circuit. This can permit faster heat transfer at the third heat exchanger 502 than at the second heat exchanger 304.

[0142] The third heat exchanger 502 is similar to the second heat exchanger 40 described with reference to Figure 5. A pump 506 is provided in the space heating branch 7 to pump water from the tank into the third heat exchanger 502. No three-port valve is included at the space heating junction, as instead the pump 506 can be used to control flow to the space heating branch 7. The three-port valve 20 at the heating mode junction can optionally be controlled to block flow from the first heat exchanger 10 to the heating mode junction. The space heating branch 7 feeds back into a conduit providing a flow path from a bottom part of the tank to the first heat exchanger. In a rapid space heating mode, the water from the tank is circulated from the first heat exchanger 10 to the third heat exchanger and back to the first heat exchanger 10.

[0143] In this configuration, the space heating system can include a heat source junction with a three- port valve 504. The heat source junction provides a flow path to the second heat exchanger 304 and a bypass flow path bypassing the second heat exchanger 304. The controller 200 may be used to control the flow of fluid between the heat exchange coil 340, the second heat exchanger 502 and the space heating system 110. When rapid heating is required by the space heating system 110, the third three-port valve 504 connects the third heat exchanger 502 to the space heating system 110, bypassing the heat exchange coil 340. This allows heat to be exchanged from the heat pump 12 to the space heating system 110.

[0144] The third three-port valve 504 also allows the heating system 500 to operate in the same manner as the heating system 300 by connecting the heat exchange coil 340 to the space heating system 110, thereby transferring heat from the water in the tank 2 to the space heating system 110.

[0145] The third pump 506 and third three-port valve 504 are controlled by the controller 200 to control the flow of heat from the first heat exchanger 10 to the tank or space heating system 110. As with the first pump 8, the third pump 506 may be controlled by the controller 200 by switching the pump on and off or by varying the speed of the pump, thereby altering the flowrate of the water passing through the pump.

[0146] As shown in Figure 10, the heating system 500 may further include a heater 508 installed inline with the space heating system 110. The heater 508 is installed downstream from the second heat exchanger 40. The heater 508 is electrically powered and configured to provide heat to the space heating system 110 when demand is required. The heater 508 is controlled by the controller 200 and may be operated to supplement heat from the heat pump 12 or as an instantaneous heat source to provide heat to the space heating system 110 to cover any period between the heat pump 12 starting and providing heat. As there is likely to be a period of time between a heat demand and the heat pump 12 providing heat to the space heating system, the heater 508 can be operated to bridge this gap by providing an instantaneous heat input to the space heating system. It will be appreciated that a heater 508 may be included in the space heating system in any of the examples described above. In the example illustrated in Figure 10 the heating mode junction and upper return branch described above are omitted. Actuation of the space heating branch 7 by the three-port valve 30 causes the water from the tank to circulate from the first heat exchanger 10 to the second heat exchanger 40 and back to the first heat exchanger 10. A different variant of the integrated heat pump hot water tank 600 is shown in Figure 11 . The heat pump 12 is shown expanded into some of its constituent components, namely the compressor 12.1 and the evaporator and fan unit 12.3.

[0147] In the integrated heat pump hot water tank 600, the heat pump condenser 12.2 is a coil wrapped around the outside surface of the tank 2 and thermally conductive with the tank 2. This may be achieved for instance by forming the condenser 12.2 coil to be in contact with the external surface of the tank 2 (and thus underneath any insulation covering the tank). The condenser 12.2 is wrapped around a substantial portion of the height of the tank 2 to maximise the possible heat transfer between the two bodies. The condenser 12.2 therefore forms a coil shape that wraps around the tank 2 whilst extending along the height of the tank 2.

[0148] By wrapping the condenser 12.2 around the external surface of the tank 2, heat may be transferred from the heat pump 12 to the water in the tank 2 without the need for an additional aperture in the tank 2. This reduces the complexity of the integrated heat pump hot water tank 600 compared to a traditional hot water tank and reduces possible failure points e.g. a leak around a pipe passing through an aperture in the tank 2. This may also allow for easier integration of a heat pump 12 with a tank 2 as there is no longer a requirement for the condenser and apertures through the tank 2 to be substantially aligned.

[0149] The condenser 12.2 may be formed from a material with a high thermal conduction coefficient, for instance copper, thereby maximising the amount of heat transfer between the condenser 12.2 and the tank 2.

[0150] The variant of the integrated heat pump hot water tank 600 includes a heat exchange coil 340, immersed in the tank 2 for receiving heat from the water in the tank and providing it to an external space heating system 110, as described e.g. with reference to the heating systems 300 described herein. A heating element 22 is illustrated near the heat exchange coil 340 and beneath it, so that it can heat a portion of the water in the tank in the region of the heat exchange coil 340 to a relatively high temperature for rapid availability of heat for space heating. The controller and other features of the heating systems described elsewhere may be included with and adapted for the integrated heat pump hot water tank 600.

[0151] Figures 12a and 12b shows a heating system 700 comprising a tank 2 and a mechanically ventilated heat recovery system (MVHR) 710.

[0152] In modern buildings with well-sealed rooms to reduce heat losses, air can become stale due to it not being replenished regularly. The stale air may contain useful heat however (or may be usefully cold in warmer climes) and simply replacing the air wastes the useful heat. To this end, an MVHR 710 is an air-air heat exchanger that allows the heat transfer to occur from stale or used air (also referred to as exhaust air) being removed from an interior of a building to fresh air (also referred to as intake air) entering the interior of the building, thereby recovering some of the heat from the stale air.

[0153] The MVHR 710 comprises a heat exchanger arranged in a housing arranged to provide heat transfer between a primary and secondary airflow. The primary side of the MVHR 710 features an (outdoors) air intake duct 720 which draws fresh air into the primary side of the MVHR 710 heat exchanger. After passing through the MVHR 710, the air drawn into the intake duct 720 exits though an indoors release duct 750 into a building interior.

[0154] The secondary side of the MVHR 710 features an indoors intake duct 740 which draws used or stale air from an indoors space into the secondary side of the MVHR 710. The airflow through the secondary side of the MVHR 710 exchanges heat with airflow through the primary side of the MVHR 710 and then exits the MVHR 710 through an exhaust duct 730.

[0155] The intake duct 720 to the primary side of the MVHR 710 features a T-piece which connects the air intake duct 720 to the air intake 11 of the heat pump 12. A first diverter 722 permits selection of whether the air intake 11 of the heat pump draws air from the outside or from an indoors space. The first diverter 722 may be a physically moveable connection that joins together different ducts or may be a valve whose position is used to connect different ducts.

[0156] The first diverter 722 sits between a junction (the T-piece) in the intake duct 720, the heat pump unit 13, and a duct open to an indoors space (for instance a room in a domestic dwelling). The heat pump unit 13 is connected to the first diverter 722 by ducting 724.

[0157] The air outlet 15 of the heat pump 12 connects to the exhaust duct 730 of the secondary side of the MVHR 710 by way of a T-piece (the letter ‘A’ in Figures 12a and 12b denotes ducts that are connected). A second diverter 752 permits selection of whether the air outlet 15 of the heat pump discharges air to the outside or to an indoors space.

[0158] The second diverter 752 sits between a junction (the T-piece) in the exhaust duct 730, the heat pump unit 13, and the indoors release duct 750. The second diverter 752 may be a physically moveable connection that joins together different ducts or may be a valve whose position is used to connect different ducts. The air intake 11 of the heat pump unit 13 is connected to the second diverter 722 by ducting 754.

[0159] A first water-air heat exchanger 756 is mounted in the indoors release duct 750 and is configured to exchange heat between the air leaving the primary side of the MVHR 710 and a water flow. The water-air heat exchanger 756 may comprise a coiled or serpentine pipe exposed to the airflow in the indoors release duct 750 with water pumped through the pipe to exchange heat with the air leaving the MVHR 710. In Figures 12a and 12b, both lines labelled ‘F2’ are connected, as are both lines labelled ‘R2’. The water side of the first water-air heat exchanger 756 is connected to the first heat exchanger 10 via a first MVHR duct heat exchanger pump 770.

[0160] A second water-air heat exchanger 732 is mounted in the exhaust duct 730 downstream of the MVHR 710 and is as described with reference to the first water-air heat exchanger 756. The second water-air heat exchanger 732 is configured to exchange heat between the air leaving the secondary side of the MVHR 710 and a water flow. In Figures 12a and 12b, both lines labelled ‘FT are connected, as are both lines labelled ‘RT. The second heat exchanger 732 is also connected to the first heat exchanger 10 by a second MVHR duct heat exchanger pump 760.

[0161] The primary and secondary side of the MVHR 710 may feature more than a single intake and exhaust as shown. For instance, the MVHR 710 may have a plenum at the entry and exit at any side of its heat exchanger allowing air to be drawn or exhausted to multiple sources. The plenum may split into a plurality of ducts, with each duct optionally using a valve and / or inline fan to direct air from or to the MVHR 710 according to need.

[0162] From the tank 2 conduits provide a flow path from the tank 2 to the first heat exchanger 10 and onward to a first air conditioning junction 772. The first air conditioning junction 772 has a first air conditioning branch providing a flow path to a second air conditioning junction 762; and a bypass branch providing a flow path bypassing the second air conditioning junction 762, and instead returning the water to the tank 2. The second air conditioning junction 762 has a second air conditioning branch providing a flow path to the first water-air heat exchanger 756; and a third air conditioning branch providing a flow path to the second water-air heat exchanger 732.

[0163] In the state shown in Figure 12a the heating system 700 is operating in a space heating or water heating mode.

[0164] In the space heating mode, the second MVHR duct heat exchanger pump 760 is turned off and the first MVHR duct heat exchanger pump 770 turned on to move water from the first heat exchanger 10 to the first water-air heat exchanger 752. Fresh air flows into the intake duct 720 and is split; a portion passing into the MVHR 710 and the remainder passing into the heat pump unit 13 as the first diverter 722 is in a first position connecting the intake duct 720 to the heat pump unit 13.

[0165] Heat is extracted from the air entering the heat pump unit 13 by the heat pump 12 and transferred to the first water-air heat exchanger 752 via the first heat exchanger 10 and the first MVHR duct heat exchanger pump 770. The cooled air exiting the heat pump unit 13 is then transferred to the exhaust duct 730 via the second diverter 752 and exhausted away from the indoors space.

[0166] Simultaneously, stale or used air is extracted from the indoors space via the indoors intake duct 740, passes through the MVHR 710 and exits through the exhaust duct 730. As the stale air passes through the MVHR 710 it transfers heat to the portion of fresh air passing through the primary side of the MVHR 710.

[0167] In the water heating mode, air passes primarily through the heat pump unit 13 (due to forced ventilation from the fan unit 12.3 in the heat pump unit 13) and is exhausted into the exhaust duct 730. In this operation mode the heat pump unit 13 takes heat from the air entering the intake duct 720 and transfers the heat to water in the tank 2 by way of the first heat exchanger 10 and the flow path drawing water from the tank 2 to and returning it back to the tank 2 under the influence of a suitable pump 8. Provisions for heat transfer from the heat pump to the water in the tank may be as discussed above with reference to figures 1-11. The heat pump unit 13 exhausts the cooled air through the exhaust duct 730.

[0168] In another mode of operation the heat pump recovers heat from warm air from a building. Instead of drawing in air from outside to the heat pump, warm air from the inside of the building is drawn in. This can permit more efficient heat recovery than with the MVHR unit in some scenarios. For instance it can be particularly useful for recovering heat from warm moist air from a bathroom or kitchen.

[0169] In this operation mode, instead of drawing air to the heat pump from outside, air is drawn from a duct open to an indoors (heated) space by way of the first diverter 722 (with the first diverter 722 in the configuration shown in Figure 12b). Air is again discharged from the heat pump 12 to the exhaust duct 730 by way of the second diverter 752 (with the second diverter 752 in the configuration shown in Figure 12a). The heat pump draws heat from the air and provides heat to the first heat exchanger. The first MVHR duct heat exchanger pump 770 is active and circulates water in a loop through the first water-air heat exchanger 756 and the first heat exchanger 10. The pump 8 is off and water is prevented from being drawn from the bottom of the tank. The first water-air heat exchanger 756 provides heat to air passing through the indoors release duct 750 into a building interior. By recovering heat from air not at the MVHR 710 but at the heat pump 12 more effective use of heat can be achieved, as the heat pump can operate with a higher coefficient of performance compared to the MVHR 710.

[0170] In the state shown in Figure 12b the heating system 700 is operating in a space cooling mode and the first and second diverters 722 752 have moved to their second positions. In brief, air is drawn to the heat pump and cooled, and the cooled air is provided to the indoors space. The heat obtained at the heat pump can be transferred to the water tank or to exhaust air leaving the building by way of the second water-air heat exchanger 732 in the exhaust duct 730 of the MVHR 710.

[0171] When operating in a cooling capacity, as a preference heat produced by the heat pump unit 13 in cooling incoming air to the indoors space is transferred to the water in the tank 2 rather than simply exhausting the heat to the atmosphere. In this mixed heating-cooling mode, stale or used air flows from the indoors space into the indoors intake duct 740, through the MVHR 710 and into the exhaust duct 730 as usual.

[0172] Fresh incoming air from the intake duct 720 is entirely channelled through the MVHR 710 due to the position of the first diverter 722. Heat transfers from the hotter fresh air to the cooler stale air in the MVHR 710.

[0173] For a greater cooling effect air is drawn from indoors to the heat pump unit 13, cooled, and then released back to the indoors space via the indoors release duct 750. This recirculation can permit achievement of lower temperature in the indoors space. In an alternative, air is at least partially drawn from the outside via the intake duct 720 to the heat pump unit 13, cooled, and then released back to the indoors space via the indoors release duct 750. This can permit higher efficiency of heat transfer at the heat pump.

[0174] The heat pump unit 13 cools the air before discharging it into the indoors space through the ducting 750. Heat taken from cooling the air is discharged into the water in the tank 2. Once the water in the tank 2 has become saturated with heat (i.e. the temperature of the water has reached a threshold limit) any further heat drawn by the heat pump is exhausted to the outside. For this purpose the first MVHR duct heat exchanger pump 760 is turned on to move water from the first heat exchanger 10 to the second water-air heat exchanger 732. Stale or used air being exhausted from the MVHR 710 is heated as it passes through the second water-air heat exchanger 732, cooling the fluid in the second water-air heat exchanger 732. The heat removed from the air is therefore discharged to the outside.

[0175] While not illustrated, suitable fans are included (for instance mounted within the ducts) and can be controlled to provide a desired airflow in the branches to and from the MVHR 710 and the heat pump unit 12. The system may include several branches in the airflow ducts providing airflow to and from e.g. different rooms. The room from which air is being drawn to the MVHR 710 or the heat pump unit 12 may be chosen depending on the measured heat and humidity of the room. For instance air may be extracted from a kitchen or bathroom due to its high temperature and humidity, thereby maximising the amount of enthalpy in the air and thus enabling particularly effective operation of e.g. the heat pump unit 12. The duct branches may therefore further comprise temperature and / or humidity sensors to detect the properties of the airflow, or these sensors may be located in rooms within a building. Airflow may then be directed to and from selected rooms by valves or diverters or control of individual fans in the airflow paths.

[0176] The MVHR 710 may further feature an in-built fan (not shown) or plurality of fans to move air through the ducts connected to the MVHR 710. The ducts themselves may have inline fans to control the airflow through the MVHR 710.

[0177] Figure 13 shows a variant of the heating system 700 of Figures 12a and 12b. In the heating system 790 only the second water-air heat exchanger 732 is provided, such that a cooling mode of operation can be provided. In this system 790 heating is provided otherwise (e.g. with one of the heating arrangements described with reference to Figures 1-11 ; not illustrated in Figure 13). In another example only the first water-air heat exchanger 756 is provided, such that heat can be provided to the air flow for space heating.

[0178] In the heating system 790 conduits provide a flow path from the tank 2 to the first heat exchanger 10 and onward to an air conditioning junction 762. The air conditioning junction 762 has an air conditioning branch providing a flow path to the water-air heat exchanger 732; and a bypass branch providing a flow path bypassing the water-air heat exchanger 732, and instead returning the water to the tank 2.

[0179] In the examples illustrated in Figures 12a, 12b and 13 selection of a desired flow path for the water from the tank is by way of activation of the first MVHR duct heat exchanger pump 770 or the second MVHR duct heat exchanger pump 760 or the pump 8 for tank heating. It will be appreciated that selection of a desired flow path for water from the tank - be it circulation to the tank or circulation to one of the water-air heat exchangers - can instead be achieved by suitable valves at the path junctions, e.g. diverter valves or three way valves.

[0180] Whilst Figures 12a, 12b and 13 show an integrated heat pump unit 13 and tank 2, it will be understood that the units need not be integrated for use with the MVHR 710. For instance, the heat pump unit 13 could be mounted separately to the tank 2 and still transfer heat to the water from the tank 2 and the water-air heat exchangers 732 752 by the use of refrigerant or water coolant pipes. This may allow for more optimal positioning of the heat pump unit 13 and tank 2 depending on the routing of the ducts connected to the MVHR 710.

[0181] While not illustrated, the systems 700, 790 may include space heating features as described above with reference to Figures 1-11 , for instance for selection of a space heating branch for water from the tank, or an immersed coil 340, and / or tank water heating scheme features such as a lower return branch for efficient gradual heating in the water tank and an upper return branch for rapid heating in the top of the water tank. Another integrated heat pump hot water tank 800 is shown in Figures 14a, 14b, 15, and 16. Figure 14a shows a view of the integrated heat pump hot water tank 800 with the housing in place, with ports for connections labelled. Figure 14b shows a view of the internal components of the integrated heat pump hot water tank 800. Figure 15 shows details of some of the internal components at the top of the tank. Figure 16 shows some of the internal components of the integrated heat pump hot water tank 800. The integrated heat pump hot water tank 800 generally includes many of the features described above, and like features are indicated with like reference numbers.

[0182] In this variant, the heat pump unit 13 interfaces with the tank 2 through a single flange 830. The flange 830 mounts to the top of the tank 2 with a plurality of fixings (e.g. screws or bolts) around its perimeter with a gasket between the flange 830 and the tank 2 to prevent water leaks. The flange 830 has two apertures through its thickness through which a heat pump feed pipe 840 and return pipe 850 are affixed. The flange 830 may be formed as a single body with the feed and return pipes thereby further reducing the risk of water leaks. The heat pump unit 13 may mount to the flange 830 (and in turn the tank 2) or may be separately mounted to the tank 2 to form an integrated unit.

[0183] The heat pump feed pipe 840 and return pipe 850 depend from the flange into the tank. The heat pump feed pipe 840 and return pipe 850 are substantially inside the tank. It will be appreciated that in the examples described with reference to Figures 1-13 the conduits for drawing water from the tank to the first heat exchanger 10 and returning the water back to the tank are indicated outside the tank, but generally the conduits can be arranged inside or outside the tank.

[0184] In the illustrated example a valve 810 is provided at the junction between the upper return branch 3 to the tank and the lower return branch 5 to the tank. The valve 810 is a bi-state flow valve 810 that routes water either to the upper return branch 3 or to the tank and the lower return branch 5 depending on the flow rate at the valve 810. This valve 810 permits passive control of the flow at the junction. By suitable control of the pump rate the valve enables selection of the appropriate flow path to the top or bottom of the tank. This valve 810 is particularly convenient in the configuration where the conduits are immersed inside the tank, and electronic control of a valve at the junction could be more challenging than when the conduits are arranged outside the tank.

[0185] At a low water flowrate through the valve 810, the valve is in a first configuration and water is discharged to a first outlet, namely to the upper return branch 3. The upper return branch 3 discharges water through a diffuser 820 to reduce the amount of mixing between the water in the tank 2 and the water entering the tank via the upper return branch 3. If the flowrate of water through the bi-state flow valve 810 is increased beyond a threshold limit, the valve takes on a second configuration in which the first outlet is blocked and instead a second outlet is opened, the second outlet discharging to the lower return branch 5. This can be achieved with a suitably moveable shuttle inside the valve 810 for instance. All water flowing into the valve then exits through the return pipe 850 which discharges water into the base of the tank 2 via a second diffuser 860.

[0186] By using a flange 830, the pipework between the heat pump unit 13 and the tank 2 is kept internal, cleaning up the exterior of the tank 2. The integrated heat pump hot water tank 800 may therefore be less prone to leaks and easier to install.

[0187] The illustrated integrated heat pump hot water tank 800 is configured for use e.g. in the heating system illustrated in Figure 1 , but can be adapted for use in the other heating systems described above.

[0188] In the illustrated examples the first heat exchanger 10 is arranged with the heat pump 12 above the tank 2. This is particularly convenient as it can permit particularly compact integration of the heat pump with the heat exchanger. In other examples the second heat exchanger 40, and optionally one or both of the three-port valves, may be arranged with the heat pump 12 above the tank 2, with or without the first heat exchanger 10.

[0189] In the illustrated examples the lower return branch provides a flow path to a bottom region of the tank 2, but in other examples the lower return branch can provide a flow path to a central region of the tank 2 instead. It will be understood that a number of return branches may be included for providing hot water to different regions of the tank for a nuanced heating strategy.

[0190] In the illustrated examples the pump 8 is provided between the first heat exchanger 10 and the bottom of the tank. Conceivably the pump 8 may be arranged downstream of the first heat exchanger 10 and before the three port valves 20, 30, though this is less preferred as operating the pump at the higher temperature downstream of the heat exchanger can be less favourable.

[0191] In the illustrated examples the heat pump 12 and the first heat exchanger 10 are shown in the heat pump unit 13. Other components described above are illustrated outside the heat pump unit 13 for ease of presentation, but may be included in the heat pump unit or in the tank unit or in a common unit containing the heat pump and the tank. This includes the second heat exchanger, pumps, three-port valves, non-return valves and at least a portion of the conduits connecting the components. The components describe above may be fixed to the heat pump unit or the tank unit or to a common unit containing the heat pump and the tank for ease of access to the components. Some of the components described above may be provided in connection with the integrated heat pump water tank, but not necessarily attached to or mounted on or in the integrated heat pump water tank.

[0192] In the illustrated examples a heat mode junction with an upper return branch and a lower return branch is shown and described. In other examples, the heat mode junction is omitted, and a flow path for returning water to the tank is provided such that water can only be returned to one region of the tank. In such examples the flow can be returned to the bottom of the tank for most efficient water heating; or to a central region of the tank; or to the top of the tank for top- down heating. As the heat mode junction is omitted the first three-port valve at the heat mode junction is also omitted. In such examples the second heat exchanger may be provided as described above.

[0193] While not specifically shown in some of the figures, the heating system generally includes a controller for controlling the heating system.

[0194] In some examples the integrated heat pump water tank includes two modular units: a tank unit 19 including the tank 2 and a heat pump unit 13 including the heat pump 12. The tank unit and the heat pump unit are modular and can be conjoined and detached and exchanged for other modules. The tank unit and the heat pump unit together can form an integrated heat pump water tank. Further components may be included to form a heating system, for instance external conduits and other fluid handling components (e.g. pump, non-return valve, 3-way valve). The heat pump unit can include one or more of the heat exchangers. The tank unit and the heat pump unit can each include suitable ports e.g. for connection of the conduits for fluids to and from the units as well as suitable electrical connectors for receiving power and data connectors for receiving and sending data.

[0195] In conventional integrated heat pump water cylinders typically a condenser coil is wrapped around the inner tank liner for transferring heat from the heat pump to the tank. Because the condenser coil is thus embedded in the tank structure it cannot easily be removed from the tank without substantial damage and repairs required. In practice this means that if for instance a home requires a larger tank then the whole conventional integrated heat pump water cylinder is replaced, even if the heat pump would still be able to meet the demands and only replacement of the tank would be necessary. A modular heat pump water tank with a tank unit including the tank 2 and a heat pump unit including the heat pump 12 can overcome these issues.

[0196] The modular heat pump water tank can include a number of features to facilitate joining and detaching of the heat pump unit to and from the tank unit. A mounting guide can ensure that the heat pump unit is mounted on the tank unit with the correct positioning and orientation. This can prevent applying unintended loads on the tank unit, which could damage the tank unit. A mounting guide can be provided at the tank unit, but it may alternatively be provided at the heat pump unit, or a set of mating mounting guides may be provided at both the tank unit and the heat pump unit.

[0197] An attachment means can ensure that the heat pump unit is fixedly attached to the tank unit. This can prevent the units from shifting e.g. under vibrations during operation. A wide variety of attachment means can be used, e.g. holes to be aligned for receiving a bolt and fixing with a nut or a thread embedded in a hole, or clamps for arranging and tightening. The attachment means is releasable so that the units can be dismounted from one another. In an example the heat pump unit and / or the tank unit includes a frame structure to which components are mounted. The frame structure can conveniently be used for attachment of the modules to one another. An attachment means can be provided at the tank unit, but it may alternatively be provided at the heat pump unit, or a set of cooperating attachment means may be provided at both the tank unit and the heat pump unit.

[0198] A module sensor can sense whether or not a heat pump unit is attached to the tank unit. This can enable a controller to verify presence or absence of a heat pump unit at a tank unit. A wide variety of sensor types can be used for the module sensor, e.g. a mass sensor, an optical sensor or a proximity sensor, amongst others. In addition to merely sensing presence or absence of a mounted unit, a module recognition component can be provided for identifying characteristics of a module (capacity, performance, etc) by suitable means, as part of the module sensor or separately.

[0199] In use a heat pump unit can be mounted and attached to a tank unit, and then suitable connections can be provided. In some examples a common fascia or housing can accommodate both the tank unit and the heat pump unit. This can conceal the modular nature of the integrated heat pump water tank and permit integrated presentation of the heat pump water tank.

[0200] Ports of the tank 2 for connecting the tank 2 to the heat exchanger 10 can be capped so that the tank 2 can operate in the absence of a heat pump unit same as a conventional hot water boiler. The tank can include for example an electrical heating element for operation in the absence of heat from the heat pump. A tank unit can thus heat, store and provide hot water in the absence of a heat pump unit. By virtue of the modularity a heat pump unit can be installed at a later date with ease and at lower cost as the tank unit need not be replaced. By virtue of the integration of the heat pump unit and the tank unit into a common assembly a particularly compact heating system can be provided. Further, by virtue of the modularity if an installed heat pump unit becomes damaged or suffers performance problems then the heat pump unit can be removed and replaced with a new heat pump unit with ease and at lower cost as the tank unit need not be replaced. If the replacement is not immediate then the tank unit can continue to perform to avoid inconvenience to a user. The modular units can be transported separately for greater convenience and conveniently installed on site as they are already adapted to cooperate.

[0201] Figure 17 shows an embodiment of a space heating system 900 broadly corresponding to the heating system 300, with the exception of a heat exchange coil 340-2 for providing heat to the space heating system 110, and a coil bypass valve 342.

[0202] In the space heating system 900 the heat exchange coil 340-2 is located in a lower section of the tank with the upper coil end at approximately mid-height of the tank 2. The heat exchange coil 340-2 is largely as described with reference to the heat exchange coil 340 in that its purpose is to provide heat to the space heating system 110.

[0203] Space heating systems typically operate at lower temperatures than hot water draw off, for instance around 45°C compared with around 60°C. Heat pumps also operate at a higher coefficient of performance when delivering heat at a lower temperature. By situating the heat exchange coil 340-2 in a lower section of the tank where the fluid in the tank 2 is at a lower temperature, it is possible to increase the performance of the heating system 900.

[0204] The location of the heat exchange coil 340-2 within the tank 2 depends on the size of the tank and the largest expected hot water draw event (e.g. a bath, or several showers in a short period of time). As a hot water draw event occurs hot water is drawn from the tank 2 and cold water is replenished at the bottom of the tank, and the thermocline in the tank rises in height (the thermocline being the zone in the tank where there is a transition from colder to hotter water across a steep gradient). It is usually convenient to operate the tank such that the largest expected hot water draw event could be accommodated, and maintain that quantity of water hot. This defines the portion of the tank that is usually kept hot, and this portion of the tank can also fairly reliably provide heat to the space heating system. The heat exchange coil 340- 2 may therefore advantageously be positioned such that it is within the volume that is usually kept hot to accommodate the largest expected hot water draw event. The heat exchange coil 340-2 is conveniently provided at the bottom part of that volume, e.g. such that a bottom end of the heat exchange coil 340-2 is at a level above which is provided a volume that can satisfy the largest expected hot water draw event. For instance in a 180-litre tank with a largest expected hot water draw event of 90 litres the bottom end of the heat exchange coil 340-2 is arranged near the middle of the tank. This arrangement of the heat exchange coil 340-2 can help ensure that the tank is at most times capable of delivering heat to the heat exchange coil 340-2 and the space heating system 110. In another arrangement the heat exchange coil 340-2 may be provided beneath a volume that can satisfy the largest expected hot water draw event, e.g. such that a top end of the heat exchange coil 340-2 is at a level above which is provided a volume that can satisfy the largest expected hot water draw event. This can be beneficial if the temperature at which the region of the heat exchange coil 340-2 is maintained for space heating, for instance around 45°C, is considered too low to satisfy a hot water draw event. With such an arrangement for instance in a 180-litre tank with a largest expected hot water draw event of 90 litres the top end of the heat exchange coil 340-2 is provided near the middle of the tank.

[0205] The coil bypass valve 342 is a 3-port valve that may be installed inline between the space heating system 110 and the heat exchange coil 340-2 if the heating system 900 is also fitted with a heater 508 inline with the space heating system 110. The third port of the coil bypass valve 342 is connected to the outlet from the heat exchange coil 340-2, such that the coil bypass valve 342 either routes return heat transfer fluid from the space heating system 110 through the heat exchange coil 340-2 or bypasses the heat exchange coil 340-2 and returns the heat transfer fluid to the inlet of the space heating system 110.

[0206] When the heater 508 is turned on, the heat transfer fluid in the space heating system 110 is heated directly rather than transferring heat from the tank 2. To prevent this heat input from being transferred to the fluid in the tank 2, the coil bypass valve 342 is controlled to bypass the heat exchange coil 340-2, meaning that heat transfer fluid flowing from the space heating system 110 is passed back into the space heating system 110 without passing through the heat exchange coil 340-2. When the heater 508 is turned off, the coil bypass valve 342 can be controlled to connect the space heating system 110 to the heat exchange coil 340-2, allowing heat to flow from the tank 2 to the space heating system 110.

[0207] The embodiment shown also features a second heater 22-2 that is immersed in the fluid in the tank 2. The second heater 22-2 is located in an upper section of the tank 2 and above the heat exchange coil 340-2 such that it can directly heat the water above the heat exchange coil 340- 2.

[0208] The thermal sensor 14 provides information on the distribution of heat in the tank to ensure that the heat exchange coil 340-2 is able to provide heat to the space heating system 110. The thermal sensor 14 can track the location of the thermocline in the tank 2 and ensure that it does not reach the bottom of the heat exchange coil 340-2. The heaters 22 and 22-2 can be controlled as appropriate to increase the temperature of the water in the tank and ensure that the heat exchange coil 340-2 remains able to provide heat to the space heating system 110.

[0209] It will be appreciated that various aspects described above can be suitably combined. While a plate heat exchanger is described in the examples above, it will be appreciated that other types of heat exchangers may be used instead, such as a shell and tube heat exchanger.

[0210] The tank is typically an unvented tank for containing mains pressurised water; a water cylinder is an example of such a tank. A pressurised tank can distribute hot water throughout a building without needing any pumps. A water cylinder is a tank in the form of a cylinder with domed ends. This form is favourable for stress distribution and particularly well suited for a tank for containing pressurised water.

[0211] The heat pump is typically an air source heat pump, but in some examples it may be a geothermal heat pump or other type of heat pump.

[0212] An upper portion of the tank as referred to herein is preferably above a lower portion of the tank, with the tank in such orientation as it is intended to be installed for use. An upper portion of the tank may include a top of the tank and a central region of the tank. A lower portion of the tank as referred to herein is preferably below an upper portion of the tank, with the tank in such orientation as it is intended to be installed for use. A lower portion of the tank typically includes a bottom of the tank but may in some instances include e.g. a central region of the tank instead or in addition. An intermediate portion of the tank as referred to herein is preferably above a lower portion of the tank and below an upper portion of the tank, with the tank in such orientation as it is intended to be installed for use. An intermediate portion of the tank typically includes a central region of the tank. In some examples an upper portion of the tank may be at, near, above or below a lower portion of the tank. Where the terms ‘above’ and ‘below’ are used herein, these are meant with the heating system in such orientation as it is intended to be installed for use.

[0213] Where the top of the tank is referred to herein (e.g. for drawing hot water from, for providing heated water to), it should be appreciated that this may include near the top of the tank, a top portion of the tank, a top half, third or quarter of the tank (by volume or by height), with the tank in such orientation as it is intended to be installed for use. Where the bottom of the tank is described (e.g. for letting in cold water, for pumping water to be heated from), it should be appreciated that this may include near the bottom of the tank, a bottom portion of the tank, or a bottom half, third or quarter of the tank (by volume or by height), with the tank in such orientation as it is intended to be installed for use. Where the central region of the tank is referred to herein, it should be appreciated that this may include regions of the tank between the top of the tank and the bottom of the tank, for instance a middle half, third or quarter of the tank (by volume or by height). Where water from the tank is referred to, this includes both water inside the tank and water drawn from the tank, e.g. in a fluid circuit external to the tank. This is typically potable water that is suitable for provision of hot water to a user.

[0214] Various other modifications will be apparent to those skilled in the art. For example, while the detailed description has considered a vessel such as a hot water tank, the disclosures herein could similarly be used with other fluids that are heated or other water vessels which are not tanks.

[0215] It will be understood that the present invention has been described above purely by way of example, and modifications of detail can be made within the scope of the invention. Reference numerals appearing in the claims are by way of illustration only and shall have no limiting effect on the scope of the claims.

[0216] The term ‘comprising’ as used herein preferably means ‘including’ or ‘consisting at least in part of’.

Claims

Claims1. A heating system comprising: an integrated heat pump water tank with a heat pump for providing heat and a tank for containing heated water; a first heat exchanger arranged externally to the tank for transferring heat from the heat pump to water from the tank; a second heat exchanger for transferring heat from water from the tank to a space heating system; and conduits providing one or more flow paths from the first heat exchanger to the tank.

2. A heating system according to Claim 1 , wherein the flow paths from the first heat exchanger to the tank include a heat mode junction, the heat mode junction having an upper return branch providing a flow path to a top of the tank and a lower return branch providing a flow path to a bottom of the tank.

3. A heating system according to Claim 1 or 2, wherein the second heat exchanger is a conduit in thermal contact with heated water inside the tank, preferably a heat exchange coil for immersion in heated water in the tank.

4. A heating system according to Claim 1 or 2, wherein the second heat exchanger is arranged externally to the tank, preferably wherein the second heat exchanger is a plate heat exchanger.

5. A heating system according to Claim 4, wherein the flow paths from the first heat exchanger to the tank further include a space heating junction, the space heating junction having a space heating branch providing a flow path to the second heat exchanger and a bypass branch providing a flow path bypassing the second heat exchanger.

6. A heating system according to Claim 2 or Claim 4 or 5 when dependant on Claim 2, comprising a first three-port valve at the heat mode junction.

7. A heating system according to Claim 5 or 6, comprising a second three-port valve at the space heating junction.

8. A heating system according to any one of Claims 5 to 7, comprising a pump in the space heating branch, preferably a variable speed pump.

9. A heating system according to Claim 8, further comprising a non-return valve arranged to prevent water flow from an upper portion of the tank to a lower portion of the tank via the conduits.

10. A heating system according to any of Claims 5 to 9 when dependent on Claim 2, wherein the heat mode junction is upstream of the space heating junction.

11. A heating system according to Claim 10, wherein the space heating branch feeds into the lower return branch.

12. A heating system according to any of Claims 5 to 9 when dependent on Claim 2, wherein the space heating junction is upstream of the heat mode junction.

13. A heating system according to Claim 12, wherein the space heating branch feeds into the bypass branch upstream of the heat mode junction or into the lower return branch.

14. A heating system according to Claim 12, wherein the space heating branch feeds into a conduit providing a flow path from a bottom part of the tank to the first heat exchanger.

15. A heating system according to any preceding claim further comprising a thermal sensor arranged to sense a temperature distribution in the tank, preferably an array of temperature sensors arranged to sense temperatures at different heights of the tank.

16. A heating system according to any preceding claim, wherein the tank comprises an electrical immersion heating element arranged in the tank, preferably in an upper portion of the tank.

17. A heating system according to any preceding claim, wherein the conduits provide a flow path external to the tank from a portion of the tank to the first heat exchanger; and a pump, preferably a variable speed pump, is arranged to pump water through the conduits.

18. A heating system according to any preceding claim, wherein the integrated heat pump water tank comprises the first heat exchanger, and optionally the second heat exchanger.

19. A heating system according to any preceding claim, further comprising a third heat exchanger for transferring heat from water the tank to the space heating system, preferably wherein the third heat exchanger is a plate heat exchanger.

20. A system comprising a heating system according to any preceding claim and a controller configured to select a flow path in dependence on a heat demand.

21. A system according to Claim 20 when dependent on Claim 5, wherein the controller is configured to provide a flow path to the space heating branch in response to a space heating demand.

22. A system according to Claim 20 or 21 when dependent on Claim 3, wherein the controller is configured to provide a flow path to the upper return branch in response to an urgent hot water demand.

23. A system according to any one of Claims 20 to 22 when dependent on Claim 3, wherein the controller is configured to provide a flow path to the lower return branch in response to a non-urgent hot water demand.

24. A system according to any one of Claims 20 to 23, wherein the controller is configured to provide a flow path in dependence on a temperature distribution in the tank.

25. A system according to any one of Claims 20 to 24, further comprising a ventilation system configured to route air to and from the heat pump, wherein the controller is configured to select an air flow path in the ventilation system in dependence on one or more temperature sensors and / or humidity sensors in the ventilation system.

26. A system according to any one of Claims 20 to 25, further comprising an external heat exchanger arranged outside a building, wherein the controller is configured to provide heat to the external heat exchanger in dependence on a demand for air conditioning.

27. A system according to any one of Claims 20 to 26 when dependent on Claim 19, further comprising a space heating system with a heat source junction having a first branch providing a flow path to the second heat exchanger, and a second branch bypassing the second heat exchanger.

28. A system according to Claim 27, further comprising a three-port valve at the heat source junction.

29. A system according to Claim 28, wherein the controller is further configured to control the three-port valve at the heat source junction.

30. A system according to any one of Claims 20 to 29, further comprising a space heating system with an electric heater in a flow path for a heat transfer fluid of the space heating system.31 . A system according to Claim 30, wherein the electric heater is located downstream of the second heat exchanger.

32. A system according to Claim 30 or 31 , wherein the electric heater is located away from the hot water tank, preferably near the location where heat is transferred to the space.

33. A system according to any one of Claims 30 to 32, further comprising a bypass valve coupled between the space heating system and the second heat exchanger.

34. A system according to any preceding claim, wherein the second heat exchanger is located in a central or lower portion of the tank.

35. A system according to any one of Claims 20 to 34 when dependent on Claim 16, wherein the controller is configured to control the electrical immersion heating element to control the location of a thermocline within the tank.

36. A system according to any preceding claim, wherein the second heat exchanger is located within the tank such that a volume on the tank at or above the second heat exchanger is at least the volume of the largest expected draw event.

37. A system according to any preceding claim, wherein the second heat exchanger is for transferring heat from water from the tank to an air flow.

38. A heating system comprising: a heat pump for providing heat to a tank for containing heated water; a tank for containing heated water; a first heat exchanger arranged externally to the tank for transferring heat from the heat pump to water from the tank; and a second heat exchanger for transferring heat from water from the tank to an air flow.

39. A system according to Claim 37 or 38 comprising conduits providing one or more flow paths from the tank to the first heat exchanger and to an air conditioning junction, the air conditioning junction having an air conditioning branch providing a flow path to the second heat exchanger and a bypass branch providing a flow path returning water to the tank.

40. A system according to any of Claims 37 to 39, wherein the second heat exchanger is arranged to transfer excess heat to a flow of exhaust air to the outside of a building; and / or to transfer heat to a flow of intake air to the interior of a building.

41. A system according to any one of Claims 37 to 40, further comprising a third heat exchanger for transferring heat from water from the tank to an air flow.

42. A system according to Claim 41 , wherein the second heat exchanger is arranged to transfer excess heat to a flow of exhaust air to an exterior of a building and the third heat exchanger is arranged to transfer heat to a flow of intake air to an interior of a building.

43. A system according to any one of Claims 37 to 42, further comprising a heat recovery system with a heat recovery heat exchanger for transferring heat between a flow of exhaust air to an exterior of a building and a flow of intake air to an interior of a building.

44. A system according to Claim 43, wherein the heat recovery system comprises a bypass duct for diverting intake air from an exterior of the building to the heat pump.

45. A system according to any one of Claims 43 to 44, further comprising an air duct arranged to provide air from an interior of the building to the heat pump.

46. A system according to Claim 45, configured to sense an interior space with a high air temperature and / or a high air humidity and to provide air from an interior space with high air temperature and / or air humidity to the heat pump.

47. A system according to Claim 45 or 46, configured to provide air from a kitchen and / or a bathroom to the heat pump.

48. A system according to any one of Claims 43 to 47, further comprising an air duct arranged to provide air from the heat pump to an interior of the building.

49. A system according to any one of Claims 37 to 48, further comprising an air duct arranged to provide air from the heat pump to a junction in a flow of exhaust air from the heat recovery heat exchanger to an exterior of a building.

50. A system according to any one of Claims 37 to 49, comprising means for selecting a flow path for water from the tank.

51. A system according to Claim 50, wherein the means for selecting a flow path for water from the tank is one or more pumps in one or more sections or branches of the flow path; and / or one or more valves at one or more junctions of the flow path.

52. A system according to any one of Claims 37 to 51 , comprising means for selecting an air flow path to and from the heat pump.

53. A system according to Claim 52, wherein the means for selecting an air flow path to and from the heat pump is one or more fans in one or more sections or branches of the air flow path; and / or one or more diverters at one or more junctions of the air flow path.

54. A controller for a system according to any one of Claims 50 to 53, configured to control the means for selecting a flow path for water from the tank and / or the means for selecting an air flow path to and from the heat pump.

55. A heating system comprising: an integrated heat pump water tank with a heat pump for providing heat and a tank for containing heated water; a first heat exchanger arranged at or in the tank for transferring heat from the heat pump to water in the tank; and a second heat exchanger for transferring heat from water from the tank to a space heating system.

56. A heating system according to Claim 55, wherein the first heat exchanger is arranged at a wall of the tank and / or inside the tank.

57. A heating system according to Claim 55 or 56, wherein the first heat exchanger is a conduit in thermal contact with heated water inside the tank.

58. A heating system according to any one of Claims 55 to 57, wherein the second heat exchanger is a conduit in thermal contact with heated water inside the tank, preferably a heat exchange coil for immersion in heated water in the tank.

59. The heating system of any one of Claims 57 to 58, wherein the conduits providing one or more flow paths from the first heat exchanger to the tank are substantially inside the tank, preferably for immersion in water in the tank.

60. A heating system according to any one of Claims 55 to 59, further comprising a third heat exchanger for transferring heat from water from the tank to the space heating system, preferably wherein the third heat exchanger is a plate heat exchanger.

61. A heating system according to any previous claim, wherein the first heat exchanger is arranged to transfer heat with the tank by conduction though an outer surface of the tank.

62. A heating system according to Claim 61 , wherein the first heat exchanger comprises a coil wrapped around the tank.

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