Adapter for hot water cylinder

Abstract

An adapter 1 for connecting a hot water cylinder 45 to a heat source, the adapter configured to be secured at the top of the cylinder. The adapter includes a heat exchanger 3 having a first inlet 10 f

Description

The present invention relates to an adapter for a hot water cylinder, and particularly an adapter for connecting a hot water cylinder to a heat source such as a heat pump. As background, in some countries including the UK, there are a large number of properties with hot water cylinders for storing and providing hot water on demand to the occupants. Such properties tend to be houses or commercial buildings with sufficient space to accommodate the hot water cylinder, which should be of a size capable of providing sufficient hot water for the occupants. For example, for a family of four or five people, the hot water cylinder may have a capacity of 200 - 300 litres. Larger hot water cylinders are available for dwellings with multiple bathrooms, higher occupancy or larger office premises. Hot water cylinders are often hidden from view and may be accommodated, for example, in a kitchen or bedroom cupboard, or in a basement or attic. The hot water may be used for heating the property as well as providing hot water on demand for washing, bathing, etc. Commonly used hot water cylinders may be of the direct type, such as cylinders which include an immersion heater and run on electricity, or may be of the indirect type, such as those where the water is heated indirectly by means of a gas fired boiler, for example. Both direct and indirect hot water cylinders are relatively expensive to purchase and require expert installation. Due to the recent increase in prices for domestic energy and the current movement towards renewable energy sources, an increasing number of homeowners and owners of commercial properties are opting to install heat pumps to provide hot water for washing and heating in place of gas fired boilers and / or immersion heaters. Heat pumps require time to power up and start to heat water and are therefore not able to provide hot water on demand. A hot water cylinder for storing the water heated using the heat pump is required in order to ensure that hot water is available when required by the occupants. Unfortunately, commonly used direct and indirect hot water cylinders are not suitable for use with a heat pump. Direct hot water cylinders rely on the immersion coil to heat the water and do not have heat exchangers. Commonly used indirect hot water cylinders do have heat exchangers, however these are very inefficient when used with heat pumps. This is because heat pumps work with lower flow temperatures than the commonly used indirect hot water cylinders do. In order to improve efficiency, save energy costs and avoid long cylinder reheat times, hot water cylinders suitable for use with a heat pump have now been developed. These hot water cylinders include heat exchangers having a larger coil size than those of the commonly used indirect hot water cylinders. The larger coil provides a larger surface area which helps transfer heat to the water to be heated. However, it is necessary for the existing hot water cylinder to be removed and the new heat pump compatible cylinder to be installed. As many of the hot water cylinders which would need to be removed are quite new, and as new hot water cylinders often cost several hundred pounds or more, this process can be expensive for the homeowner, as well as being wasteful. Furthermore, to remove and replace the hot water cylinder an installation expert will be required for approximately 2 days, thereby adding to the cost and leaving the homeowner without heating or hot water for the duration of the hot water cylinder replacement. In view of the above, there exists a need to adapt the commonly used hot water cylinders so that they are suitable for use with a heat pump. According to a first aspect there is provided an adapter for connecting a hot water cylinder to a heat source, wherein the adapter is configured to be secured to the exterior of a hot water cylinder at the top of the hot water cylinder, and wherein the adapter comprises: a heat exchanger having a first inlet for receiving hot working fluid from a heat source and a first outlet for returning the cooled working fluid to the heat source after the working fluid has passed through the heat exchanger, and having a second inlet for receiving water for heating from the hot water cylinder and a second outlet for returning the heated water to the hot water cylinder after the water from the hot water cylinder has passed through the heat exchanger; a pump for pumping water from the hot water cylinder through the heat exchanger and back to the hot water cylinder; a fluid path arranged to allow hot water to flow out from the top of the hot water cylinder through the adapter to a hot water pipe, the fluid path being a hot water outlet from the hot water cylinder; and a tube in fluid communication with the second outlet of the heat exchanger, the tube being configured to extend into the interior of the hot water cylinder when the adapter is secured to the hot water cylinder. The adapter may include one or more temperature sensors. A temperature sensor may be located at the first inlet of the heat exchanger. A temperature sensor may be located at the first outlet of the heat exchanger. By providing a temperature sensor at the first inlet and a temperature sensor at the first outlet of the heat exchanger, the temperature of the working fluid entering the heat exchanger can be monitored and the difference in temperature between the working fluid entering the heat exchanger and leaving the heat exchanger can be monitored. A flow sensor may also be provided to monitor the flow rate of the working fluid passing through the heat exchanger. A temperature sensor may be located at the second inlet of the heat exchanger and may monitor the temperature of the water from the cylinder entering the heat exchanger. A temperature sensor may be located at the second outlet of the heat exchanger and may monitor the temperature of the water being returned to the cylinder from the heat exchanger. A flow sensor may also be provided to monitor the flow rate of the water passing through the heat exchanger. The adapter may achieve a flow rate of up to 20 litres of water per minute through the heat exchanger. A temperature sensor may be located in the hot water outlet from the hot water cylinder. A flow sensor may be provided in the hot water outlet from the hot water cylinder. The adapter may include a processor. The processor may comprise a memory operatively coupled to the processor. The memory may store information and instructions for the processor. The processor may be configured to receive information from one or more sensors including one or more of the temperature sensors and / or flow sensors mentioned above. The processor may store this information in the memory. The processor may be configured to control the operation of the pump. The processor may be configured to switch on the pump when the heat source is active. The processor may be configured to receive information from a temperature sensor located at the first inlet of the heat exchanger and to switch on the pump when a target temperature is detected. The pump may be controlled by the processor in order to control the flow rate of water through the heat exchanger. The processor and pump may be provided with a 24 Volts DC power source to provide power in a safe manner. The adapter may include a housing. The housing may be made from any suitable material. A plastic material, for example expanded polypropylene (EPP), may be used. The housing may be of cylindrical form. The housing may have a diameter substantially greater than its height. The housing may have a diameter of 400mm, a maximum height of 271mmand a minimum height of 213mm. Alternatively other shapes may be used, such as a cuboid, for example. The housing may contain and support within it the heat exchanger and the pump. The housing may further contain one or more temperature sensors and may further contain the processor. The housing may be configured to provide insulation to the heat exchanger and the pump. The housing may be formed from a plurality of sections which may be fitted together during assembly. One or more of the sections may be detachable to provide access to the components located in the housing for maintenance, repair or replacement purposes. One or more of the sections may be rotatable with respect to the other sections to aid installation. The hot water outlet may be provided in a different section to the heat exchanger and pump such that the hot water outlet may be rotated with respect to the heat exchanger and pump and their inlets and outlets. This may aid installation of the adapter. The heat source may be a heat pump, for example. The heat exchanger may be a plate heat exchanger, for example. The adapter may include support means for supporting the adapter on the top of a hot water cylinder. The support means may be height adjustable. The support means may comprise a height adjustable ring stand. The height adjustable ring stand may be telescopic. The height adjustable ring stand may comprise at least two rings. The rings may be sized such that one ring is slidable within another ring. The rings may have different diameters such that one ring is able to fit concentrically within another ring. Each of the rings may have an inward facing surface and an outward facing surface. The inner ring (the ring having the smaller diameter) may have at least one protruding element extending in a radial direction outwardly from its outward facing surface. The outer ring may have a slotted hole extending across at least a part of the width of the ring for receiving the protruding element. The slotted hole may extend in a direction parallel to the width of the ring or at an angle to this direction. The adapter may be fixed to the innermost ring. The housing of the adapter may be configured to be attached to the innermost ring. The bottom section or part of the housing may be sized to fit within the innermost ring. The section or part of the housing adjacent to the bottom section or part may be sized so that it is too large to fit within the innermost ring. The housing may be sized such that its bottom section or part fits within the innermost ring and the section or part of the housing adjacent to the bottom section or part sits on the top of the innermost ring. The outer ring or rings may be adjusted by moving an outer ring relative to an inner ring such that the protruding element of the inner ring slides in the slotted hole of the outer ring. In this manner, an outer ring may slide relative to an inner ring between an extended position and a collapsed position. If the slotted holes extend in a direction parallel to the width of the ring, then the outer ring may be slid along the width direction relative to the inner ring. If the slotted holes extend in a direction at an angle to the width direction of the ring, then the outer ring will need to be rotated in order to move relative to the inner ring. By extending and collapsing the rings relative to each other the height of the support means can be adjusted. This permits the support means to stably support the adapter on a variety of hot water cylinders, regardless of their diameter or their shape. For example, if the adapter is to be fitted to a hot water cylinder having a substantially flat top, then the support means may be adjusted to be in a substantially collapsed position. This represents generally the minimum height of the support means. If the adapter is to be fitted to a hot water cylinder having a rounded top, then the support means may be fully extended (which represents the maximum height of the support means) or, depending upon the end shape of the cylinder and its size, the support means may be adjusted to be in a position between fully collapsed and fully extended where the support means stably rests on the top of the hot water cylinder. The protruding element may be a fixing element such as a screw, bolt or similar. Preferably at least two protruding elements and two slotted holes are provided. The two protruding elements may be positioned diametrically opposite each other. The two slotted holes may be positioned diametrically opposite each other. Three or more protruding element and slotted hole pairs may be provided. The protruding elements / slotted hole pairs may be positioned equidistantly from each other, for example they may be positioned equidistantly around the circumference of a ring. The adapter may comprise an arrangement configured to be fitted to the top of a hot water cylinder. The arrangement may be further configured to provide a hot water outlet from the hot water cylinder and may be configured to accommodate the tube. The arrangement may include a hollow body configured to accommodate the tube within the hollow body. The hollow body may be configured to accommodate the tube concentrically within the hollow body. The hollow body may comprise a first part and a second part, the second part being configured to be accommodated at least partially within the first part. The hollow body may include a connector arranged to fit the outlet at the top of the hot water cylinder. For example, the hot water cylinder may have a 22mm compression outlet and the connector may be arranged to fit this outlet. The connector may include at least one O ring. The O ring may allow the sealing of the hot water cylinder at the top whilst providing a hot water outlet via the hollow body from the hot water cylinder. The O ring may be arranged on the second part of the hollow body. At least one further O ring may be provided on the second part of the hollow body, the further O ring being arranged to be accommodated within the first part of the hollow body when the second part of the hollow body is accommodated at least partially within the first part of the hollow body. The further O ring may provide a seal between the interior of the first part of the hollow body and the exterior of the second part of the hollow body. The tube may be arranged to extend through the hollow body and into the interior of the hot water cylinder. The hollow body may have three holes through which liquid may pass in order to enter or exit the hollow body. The hollow body may be substantially a "T" shaped junction. The first part may have three holes and the second part may have two holes. The interior of the second part may be substantially funnel shaped. The hollow body may be configured such that the tube extends through the hollow interior of the hollow body and the hollow interior of the hollow body forms the hot water outlet of the hot water cylinder. In use, the hollow body may befitted to the top of a hot water cylinder and hot water from the heat exchanger may flow via the tube into the hot water cylinder and hot water from the hot water cylinder may flow via the hollow interior of the hollow body to the hot water pipe. The cross sectional area of the tube is preferably substantially smaller than the cross sectional area of the hollow interior of the hollow body, such that the flow of hot water from the cylinder through the hollow body is not significantly obstructed by the tube. For example, the internal diameter of the brass tube (cylinder connection) is 17mm, the external diameter of the stainless steel tube is 11.884mm while the internal diameter thereof is 10mm. This gives a total cross-sectional area of the stainless steel tube equalling 110.92mm2, while the brass cross sectional area (internal) is 226.98mm2. Thus 48.9% of hole area is blocked by the dip tube, while the resistance is minimised by the fact that this is only over a short span before widening out (approximately 38mm). The O ring of the connector is preferably arranged to permit the hollow body to rotate when the arrangement is secured to the top of the hot water cylinder. This allows the hot water outlet to be positioned at a desired angle when the hollow body is fixed to the hot water cylinder, and enables the hot water outlet to be connected to the existing domestic hot water pipes. The brass body rotates as a whole block, so it can rotate relative to the cylinder (taking the hot outlet pipe with it) and it can rotate relative to the EPP layer above that contains the plate heat exchanger (this allows heat pump pipework to be sited on a different wall than the HW pipework if required). Rotation can happen at any point up to when the pipework is connected to the existing system pipework, and therefore fixed in position. It can be rotated after mounting onto the cylinder. The first and second part of the brass body are threaded together by the manufacturer and then remain together, this was so that it was possible to manufacture. A retaining plate may be provided to secure the hollow body after it has been rotated to the desired position and to prevent further rotation of the hollow body. The retaining plate is to ensure that the ring stands have been adjusted correctly. After mounting the brass block to the cylinder, the lower level of EPP and ring stand is dropped over the top &hot pipe outlet made into the brass block. The retaining plate is then inserted into the brass block and the ring stand adjusted upwards until the plate is under tension. This ensures that the block &pipework is supported and the position of the EPP is in the optimum position for the next EPP layer to be fully supported. The hollow body may be made from any suitable material, such as a metal, for example stainless steel or brass. The tube may be configured to be fixed to the interior of the hollow body. The tube may be configured to be fixed to the upper part of the hollow body. The tube may extend through the hollow body and may protrude from the lower part of the hollow body such that, when the hollow body is fitted to the top of a hot water cylinder, the tube extends into the interior of the hot water cylinder. The tube may be made from any suitable material, for example from a metal such as stainless steel. The tube may have a range of suitable diameters. The tube may be extensible. The tube may be telescopic. The tube may comprise at least two portions. The at least two portions may be configured to be joined together. A first tube portion may be configured to be fixed to the hollow body. The first tube portion may have a first end configured to be fixed to the upper part of the hollow body, for example, the first end may include a thread. The first tube portion may have a second end configured to be attached to a first end of a second tube portion (an extension portion). For example the second end of the first tube portion and the first end of the second tube portion may have complementary threads to enable the first and second tube portions to be assembled together, in order to form a longer tube. A third tube portion (a further extension portion) may optionally be provided. The third tube portion may be configured to be attached to the second tube portion, for example using complementary threads. If a longer tube is desired, further tube portions may be provided. The tube portions may be joined together in ways other than by provided complementary threads, for example by using a push fit fitting, retractable detents, friction fitting or other means of attachment. By joining several tube portions together a tube of a desired length may be formed. The length of tube required may depend upon the size of the hot water cylinder and / or the desired position of the end of the tube in the hot water cylinder. The tube may have a diffuser at or near to the end of the tube remote from the heat exchanger. In this case, one end (the proximal end) of the tube may be configured to be fixed to the hollow body and the other end (the distal end) of the tube may include a diffuser. If the tube comprises two portions, then the diffuser may be included at the second end (the distal end) of the second portion. If the tube comprises three portions, then the diffuser may be included at the distal end of the third portion, and so on. The diffuser may be formed integrally with the tube portion, or may alternatively be one or more separate parts configured to be attached to the distal end of the tube. The diffuser may be tubular and have the same or similar diameter as the tube. Alternatively, the diffuser may have an oval, rectangular or other cross section. The diffuser may have a cross sectional area or a diameter significantly greater than that of the tube. The diffuser may be a radial diffuser. The diffuser may be a pipe or tube having slots or outlets formed therein. The diffuser may have at least one outlet located proximally of the distal end of the diffuser. Preferably the diffuser has at least two outlets located proximally of the distal end of the diffuser. The outlets may be located at or about the same distance from the distal end of the diffuser and may be spaced from each other around the exterior of the diffuser. The spacing between outlets may be equidistant. Where the diffuser has a circular cross section, the outlets may be located around the circumference of the diffuser. The spacing between outlets may be equidistant. The outlets may alternatively or additionally be located at a different distance from the distal end of the diffuser. The outlets may be located at or about the same point on the circumference or exterior of the diffuser or may be located at different positions around the circumference or exterior of the diffuser. The distal end of the diffuser may be closed such that the heated water may only exit the diffuser via the outlets. Preferably the diffuser comprises a first group of outlets located at or about the same distance from the distal end of the diffuser and spaced around the exterior of the diffuser. The spacing between these outlets may be equidistant. The diffuser preferably further comprises a second group of outlets located closer to the distal end of the diffuser than the first group of outlets and spaced around the exterior of the diffuser. The diffuser may further comprise a third group of outlets located closer to the distal end of the diffuser than the first group of outlets and the second group of outlets and spaced around the exterior of the diffuser. The diffuser may comprise fourth and further groups of outlets as desired. Using a diffuser can slow down the speed of the hot water from the heat exchanger entering the hot water cylinder and can influence the direction in which the incoming hot water flows. This can reduce turbulence caused by the hot water entering the hot water cylinder. The hotter water in the cylinder will rise to the top of the hot water cylinder whilst the colder water will sink to the bottom of the cylinder. As hot water is taken from the top of the cylinder for direct use in the house or workplace, it is advantageous to reduce turbulence in order to ensure that the hotter water remains at the top of the hot water cylinder and does not mix with the colder water below. The diffuser may be configured such that hot water exiting the diffuser travels in a substantially horizontal direction. Alternatively the diffuser may be configured, for example by shaping the outlets of the diffuser, such that the hot water exiting the diffuser travels at an angle to the horizontal direction. Such an angle may, for example, be in the range of approximately 0-30 degrees from the horizontal. The diffuser may have the form of a hollow pipe or tube having a central bore and several groups of outlets spaced along its length. The central bore of the diffuser may have a constant cross sectional area along the length of the diffuser. Alternatively the central bore of the diffuser may have a cross sectional area that varies gradually along the length of the diffuser. The tube is preferably of a length such that the diffuser, when the tube is fixed to the top of a hot water cylinder, is positioned at a depth such that the diffuser is level with, or below, the control thermostat in the hot water cylinder. This may reduce the impact on the hot water in the upper part of the hot water cylinder when the control thermostat triggers a demand for the water in the hot water cylinder to be heated, as only minimal mixing is likely to occur in the region of the hot water cylinder above the diffuser. When the control thermostat triggers a demand for the water in the hot water cylinder to be heated, the heat source may be switched on. Once the heat source has warmed up and its working fluid reaches a sufficient temperature to heat the water in the hot water cylinder via the heat exchanger, this can be detected by the temperature sensor located at the first inlet of the heat exchanger and the processor may then switch on the pump so that colder water may be pumped from the bottom of the hot water cylinder through the heat exchanger before being returned to the hot water cylinder after heating. According to another aspect of the invention, there is also provided a cylinder adapted for connection to a heat pump, the cylinder comprising an adapter as according to any of the first to eighth aspects disclosed herein. According to a second aspect there is provided an adapter for connecting a hot water cylinder to a heat source, wherein the adapter comprises: a heat exchanger having a first inlet for receiving hot working fluid from a heat source and a first outlet for returning the cooled working fluid to the heat source after the working fluid has passed through the heat exchanger, and having a second inlet for receiving water for heating from the hot water cylinder and a second outlet for returning the heated water to the hot water cylinder after the water from the hot water cylinder has passed through the heat exchanger; a pump for pumping water from the hot water cylinder through the heat exchanger and back to the hot water cylinder; and support means configured to support the adapter on the exterior of a hot water cylinder at the top of the hot water cylinder, the support means being height adjustable. The support means may comprise at least two rings connected to each other, the rings having different diameters such that one ring is able to fit concentrically within another ring, the rings being telescopically slidable with respect to each other such that the height of the support means is adjustable by moving one ring relative to another ring. By extending and collapsing the rings relative to each other the height of the support means can be adjusted to allow the support means to stably support the adapter on a variety of hot water cylinders, regardless of their diameter or their shape. For example, if the adapter is to be fitted to a hot water cylinder having a substantially flat top, then the support means may be adjusted to be in a substantially collapsed position. This represents generally the minimum height of the support means. If the adapter is to be fitted to a hot water cylinder having a rounded top, then the support means may be partially or fully extended in order that the bottom ring may fit around the domed top of the hot water cylinder and the top ring can support the adapter above the top of the hot water cylinder. One of the rings may have at least one protruding element extending along a radial direction towards another ring. The other ring may have a slotted hole extending across at least a part of the width of the ring for receiving the protruding element. For example, the inner ring (the ring having the smaller diameter) may have at least one protruding element extending in a radial direction outwardly from its outward facing surface and the outer ring may have a slotted hole extending across at least a part of the width of the ring for receiving the protruding element. The slotted hole may extend in a direction parallel to the width of the ring or at an angle to this direction. The height of the support means may be adjusted by moving an outer ring relative to an inner ring such that a protruding element of one of the rings slides in the slotted hole of the other ring. For example, the height of the support means may be adjusted by moving an outer ring relative to an inner ring such that the protruding element of the inner ring slides in the slotted hole of the outer ring. In this manner, an outer ring may slide relative to an inner ring between an extended position and a collapsed position. If the slotted holes extend in a direction parallel to the width of the ring, then the outer ring may be slid along the width direction relative to the inner ring. If the slotted holes extend in a direction at an angle to the width direction of the ring, then the outer ring will need to be rotated in order to move relative to the inner ring. The protruding element may be a fixing element such as a screw, bolt or similar. Preferably at least two protruding elements and two slotted holes are provided. The two protruding elements may be positioned diametrically opposite each other. The two slotted holes may be positioned diametrically opposite each other. Three or more protruding element and slotted hole pairs may be provided. The protruding elements / slotted hole pairs may be positioned equidistantly from each other, for example they may be positioned equidistantly around the circumference of a ring. The adapter may be formed integrally with the support means. Alternatively the adapter may be configured to be attached to the support means. The adapter may be configured to be detachably attached to the support means. The adapter may be fixed to one of the rings, for example the innermost ring. The bottom part of the adapter may be sized to fit within the innermost ring. The part of the adapter adjacent to the bottom part may be sized so that it is too large to fit within the innermost ring. The adapter may be sized such that its bottom part fits within the innermost ring and the part of the adapter adjacent to the bottom part sits on the top of the innermost ring. The adapter may include further features as described above with respect to the first aspect. According to a third aspect there is provided an adapter for connecting a hot water cylinder to a heat source, wherein the adapter comprises: a housing containing and supporting within it a heat exchanger and a pump, the heat exchanger having a first inlet for receiving hot working fluid from a heat source and a first outlet for returning the cooled working fluid to the heat source after the working fluid has passed through the heat exchanger, and having a second inlet for receiving water for heating from the hot water cylinder and a second outlet for returning the heated water to the hot water cylinder after the water from the hot water cylinder has passed through the heat exchanger, and the pump being arranged to pump water from the hot water cylinder through the heat exchanger and back to the hot water cylinder, the housing further accommodating a hot water outlet from the hot water cylinder; and the adapter further comprising a tube in fluid communication with the second outlet of the heat exchanger, the tube extending outside of the housing. The housing may include support means for supporting the housing on the top of a hot water cylinder. The support means may be height adjustable. The housing may be made from any suitable material. A plastic material, for example expanded polypropylene (EPP), may be used. The housing may be of cylindrical form. The housing may have a diameter substantially greater than its height. Alternatively other shapes may be used, such as a cuboid, for example. The housing may have a diameter of 400mm, a maximum height of 271 and a minimum height of 213mm. The housing may be formed from a plurality of sections which may be fitted together during assembly. One or more of the sections may be detachable to provide access to the components located in the housing for maintenance, repair or replacement purposes. One or more of the sections may be rotatable with respect to the other sections to aid installation. The hot water outlet may be provided in a different section to the heat exchanger and pump such that the hot water outlet may be rotated with respect to the heat exchanger and pump and their inlets and outlets. This may aid installation of the adapter. The housing may further contain one or more temperature sensors and may further contain a processor. The housing may be configured to provide insulation to the heat exchanger and the pump. The housing may be formed integrally with the support means. Alternatively the housing of the adapter may be configured to be attached to the support means. The housing may be configured to be detachably attached to the support means. The support means may be telescopic. The support means may comprise a height adjustable ring stand. The height adjustable ring stand may be telescopic. The height adjustable ring stand may comprise at least two rings. The rings may be sized such that one ring is slidable within another ring. The rings may have different diameters such that one ring is able to fit concentrically within another ring. Each of the rings may have an inward facing surface and an outward facing surface. One of the rings may have at least one protruding element extending in a radial direction towards another ring. The other ring may have a slotted hole extending across at least a part of the width of the ring for receiving the protruding element. For example, the inner ring (the ring having the smaller diameter) may have at least one protruding element extending in a radial direction outwardly from its outward facing surface and the outer ring may have a slotted hole extending across at least a part of the width of the ring for receiving the protruding element. The slotted hole may extend in a direction parallel to the width of the ring or at an angle to this direction. The housing of the adapter may be configured to be attached to one of the rings. The bottom section or part of the housing may be sized to fit within the innermost ring. The section or part of the housing adjacent to the bottom section or part of the housing may be sized so that it is too large to fit within the innermost ring. The housing may be sized such that its bottom section or part fits within the innermost ring and the section or part of the housing adjacent to the bottom section or part sits on the top of the innermost ring. The outer ring or rings may be adjusted by moving an outer ring relative to an inner ring such that a protruding element of one of the rings slides in the slotted hole of the other ring. In this manner, an outer ring may slide relative to an inner ring between an extended position and a collapsed position. If the slotted holes extend in a direction parallel to the width of the ring, then the outer ring may be slid along the width direction relative to the inner ring. If the slotted holes extend in a direction at an angle to the width direction of the ring, then the outer ring will need to be rotated in order to move relative to the inner ring. By extending and collapsing the rings relative to each other, the height of the support means can be adjusted. This permits the support means to stably support the adapter on a variety of hot water cylinders, regardless of their diameter or their shape. For example, if the adapter is to be fitted to a hot water cylinder having a substantially flat top, then the support means may be adjusted to be in a substantially collapsed position. This represents generally the minimum height of the support means. If the adapter is to be fitted to a hot water cylinder having a rounded top, then the support means may be fully extended (which represents the maximum height of the support means) or, depending upon the end shape of the cylinder and its size, the support means may be adjusted to be in a position between fully collapsed and fully extended where the support means stably rests on the top of the hot water cylinder. The protruding element may be a fixing element such as a screw, bolt or similar. Preferably at least two protruding elements and two slotted holes are provided. The two protruding elements may be positioned diametrically opposite each other. The two slotted holes may be positioned diametrically opposite each other. Three or more protruding element and slotted hole pairs may be provided. The protruding elements / slotted hole pairs may be positioned equidistantly from each other, for example they may be positioned equidistantly around the circumference of a ring. The adapter may further comprise an arrangement configured to be fitted to the top of a hot water cylinder, the arrangement comprising a hollow body, the hollow body being configured to accommodate at least part of the tube within the hollow body and the hollow body being configured to provide a fluid path being a hot water outlet from the hot water cylinder, the housing being configured to accommodate the hollow body. The adapter may include further features as described above with respect to the first or second aspect. According to a fourth aspect there is provided an adapter for connecting a hot water cylinder to a heat source, wherein the adapter comprises: a housing containing and supporting within it a heat exchanger and a pump, the heat exchanger having a first inlet for receiving hot working fluid from a heat source and a first outlet for returning the cooled working fluid to the heat source after the working fluid has passed through the heat exchanger, and having a second inlet for receiving water for heating from the hot water cylinder and a second outlet for returning the heated water to the hot water cylinder after the water from the hot water cylinder has passed through the heat exchanger, and the pump being arranged to pump water from the hot water cylinder through the heat exchanger and back to the hot water cylinder, the housing further accommodating a hot water outlet from the hot water cylinder; and wherein the housing comprises at least two sections and at least one of the sections is rotatable with respect to the other section or sections. The hot water outlet may be provided in a different section of the housing to the heat exchanger and pump such that the hot water outlet may be rotated with respect to the heat exchanger and pump. This may aid installation of the adapter, as the hot water outlet may be rotated to align with existing hot water pipes in a building by rotating the section of the housing in which the hot water outlet is accommodated without rotating the heat exchanger and pump and their inlets and outlets. The housing may be made from any suitable material. A plastic material, for example expanded polypropylene (EPP), may be used. The housing may be of cylindrical form. The housing may have a diameter substantially greater than its height. The housing may have a diameter of 400mm, a maximum height of 271mm and a minimum height of 213mm. Alternatively other shapes may be used, such as a cuboid, for example. One or more of the sections may be detachable to provide access to the components located in the housing for maintenance, repair or replacement purposes. The housing may further contain one or more temperature sensors and may further contain a processor. The housing may be configured to provide insulation to the heat exchanger and the pump. The housing may comprise support means for supporting the housing on the top of a hot water cylinder. The support means may be as described above. The adapter may further comprise a tube in fluid communication with the second outlet of the heat exchanger, the tube extending outside of the housing. The tube may be as described above. The adapter may include further features as described above. According to a fifth aspect there is provided an adapter for connecting a hot water cylinder to a heat source, wherein the adapter comprises: a heat exchanger having a first inlet for receiving hot working fluid from a heat source and a first outlet for returning the cooled working fluid to the heat source after the working fluid has passed through the heat exchanger, and having a second inlet for receiving water for heating from the hot water cylinder and a second outlet for returning the heated water to the hot water cylinder after the water from the hot water cylinder has passed through the heat exchanger; a pump for pumping water from the hot water cylinder through the heat exchanger and back to the hot water cylinder; and a tube in fluid communication with the second outlet of the heat exchanger, the tube being extensible, the tube comprising at least two portions being a first tube portion and at least one extension portion for extending the length of the tube. The at least two portions may be separate elements configured to be joined together. The tube may be telescopic. One of the portions of the tube may be slidable within the other portion of the tube. Alternatively the first tube portion may have an end configured to be attached to an end of the extension portion. For example, the end of the first tube portion remote from the heat exchanger and a first end of the extension portion may have complementary threads to enable the first tube portion and the extension portion to be assembled together, in order to form a longer tube. A further extension portion may optionally be provided. The further extension portion may be configured to be attached to the second end of the extension portion, for example using complementary threads. If a longer tube is desired, further extension portions may be provided. The portions of the tube may be joined together in ways other than by providing complementary threads, for example by using a push fit fitting, retractable detents, friction fitting or other means of attachment. By joining several tube portions together a tube of a desired length may be formed. The length of tube required may depend upon the size of the hot water cylinder and / or the desired position of the end of the tube in the hot water cylinder. The tube may be made from any suitable material, for example from a metal such as stainless steel. The adapter may further comprise an arrangement configured to be fitted to the top of a hot water cylinder, the arrangement comprising a hollow body, the hollow body being configured to accommodate at least part of the first tube portion within the hollow body. The hollow body may be configured to provide a fluid path being a hot water outlet from the hot water cylinder. The adapter may further comprise a housing containing and supporting within it the heat exchanger and the pump. At least part of the hollow body may be accommodated in the housing. The housing may comprise a plurality of sections. At least one section may be rotatable with respect to the other section or sections. The hot water outlet may be provided in a different section to the heat exchanger and pump such that the hot water outlet may be rotated with respect to the heat exchanger and pump. The tube may have a diffuser. The diffuser is preferably located at or near to the end of the tube. The extension portion may include a diffuser. Alternatively a separate diffuser portion may be provided at the end of the tube remote from the heat exchanger. The tube may comprise a first tube portion, at least one extension portion and a diffuser portion. The diffuser portion may be configured to be attached to the second end of an extension portion. The diffuser may have further features as described above or below. Using a diffuser can slow down the speed of the hot water from the heat exchanger entering the hot water cylinder and can influence the direction in which the incoming hot water flows. This can reduce turbulence caused by the hot water entering the hot water cylinder. The hotter water in the cylinder will rise to the top of the hot water cylinder whilst the colder water will sink to the bottom of the cylinder. As hot water is taken from the top of the cylinder for direct use in the house or workplace, it is advantageous to reduce turbulence in order to ensure that the hotter water remains at the top of the hot water cylinder and does not mix with the colder water below. The tube is preferably of a length such that the diffuser, when the tube is fixed to the top of a hot water cylinder, is positioned at a depth such that the diffuser is level with, or below, the control thermostat in the hot water cylinder. This may reduce the impact on the hot water in the upper part of the hot water cylinder when the control thermostat triggers a demand for the water in the hot water cylinder to be heated, as only minimal mixing is likely to occur in the region of the hot water cylinder above the diffuser. The tube may include several extension portions in order to ensure that the tube is long enough to extend to a depth at the level of, or below, the control thermostat in the hot water cylinder. The extension portions may include a range of lengths, for example 100mm, 200mm, 300mm, 400mm and 500mm portions. Alternatively, each extension portion may be of a similar length and may be, for example, in the range of 100 to 500mm long. The extension portions may be in the range of 250 to 350mm long. The extension portions may be approximately 300mm long. By using extension portions, a standard tube arrangement may be used for a variety of different hot water cylinders, and the tube can be configured to be a suitable length for a particular hot water cylinder by including one or more extension portions as desired. The adapter may include further features as described above. According to a sixth aspect there is provided an adapter for connecting a hot water cylinder to a heat source, wherein the adapter comprises: a heat exchanger having a first inlet for receiving hot working fluid from a heat source and a first outlet for returning the cooled working fluid to the heat source after the working fluid has passed through the heat exchanger, and having a second inlet for receiving water for heating from the hot water cylinder and a second outlet for returning the heated water to the hot water cylinder after the water from the hot water cylinder has passed through the heat exchanger; a pump for pumping water from the hot water cylinder through the heat exchanger and back to the hot water cylinder; and a tube having a proximal end in fluid communication with the second outlet of the heat exchanger, and wherein the tube comprises a diffuser at or near to its distal end. The diffuser may be formed integrally with the tube portion, or may alternatively be one or more separate parts configured to be attached to the distal end of the tube. The diffuser may be tubular and have the same or similar diameter as the tube. Alternatively, the diffuser may have an oval, rectangular or other cross section. The diffuser may have a cross-sectional area or a diameter significantly greater than that of the tube. The diffuser may be a radial diffuser. The diffuser may be a pipe or tube having slots or outlets formed therein. The diffuser may have at least one outlet located proximally of the distal end of the diffuser. Preferably the diffuser has at least two outlets located proximally of the distal end of the diffuser. The outlets may be located at or about the same distance from the distal end of the diffuser. The outlets may be spaced from each other around the exterior of the diffuser. The spacing between outlets may be equidistant. Where the diffuser has a circular cross section, the outlets may be located around the circumference of the diffuser. The spacing between outlets may be equidistant. The outlets may alternatively or additionally be located at a different distance from the distal end of the diffuser. The outlets may be located at or about the same point on the circumference or exterior of the diffuser or may be located at different positions around the circumference or exterior of the diffuser. The distal end of the diffuser may be closed such that the heated water may only exit the diffuser via the outlets. Preferably the diffuser comprises a first group of outlets located at or about the same distance from the distal end of the diffuser. The outlets of the first group may be spaced from each other around the exterior of the diffuser. The spacing between these outlets may be equidistant. The diffuser preferably further comprises a second group of outlets located closer to the distal end of the diffuser from the first group of outlets. The outlets of the second group may be spaced from each other in a manner similar to the outlets of the first group. The diffuser may further comprise a third group of outlets located closer to the distal end of the diffuser from the first group of outlets and the second group of outlets. The outlets of the third group may be spaced from each other in a manner similar to the outlets of the first group and the second group. The diffuser may comprise fourth and further groups of outlets as desired. The diffuser may be configured such that hot water exiting the diffuser travels in a substantially horizontal direction. Alternatively, the diffuser may be configured, for example by shaping the outlets of the diffuser, such that the hot water exiting the diffuser travels at an angle to the horizontal direction. Such an angle may, for example, be in the range of approximately 0-30 degrees from the horizontal. The diffuser may have the form of a hollow pipe or tube having a bore and several groups of outlets spaced along its length. The bore of the diffuser may have a constant cross-sectional area along the length of the diffuser. Alternatively the bore of the diffuser may have a cross sectional area that varies along the length of the diffuser. The cross sectional area of the bore may decrease from the first group of outlets located furthest from the distal end of the diffuser to the last group of outlets located closest to the distal end of the diffuser. The adapter may include further features as described above. According to a seventh aspect there is provided an adapter for connecting a hot water cylinder to a heat source, wherein the adapter comprises: a heat exchanger having a first inlet for receiving hot working fluid from a heat source and a first outlet for returning the cooled working fluid to the heat source after the working fluid has passed through the heat exchanger, and having a second inlet for receiving water for heating from the hot water cylinder and a second outlet for returning the heated water to the hot water cylinder after the water from the hot water cylinder has passed through the heat exchanger; a pump for pumping water from the hot water cylinder through the heat exchanger and back to the hot water cylinder; and an arrangement configured to be fitted to the top of a hot water cylinder, the arrangement comprising a hot water outlet from the hot water cylinder and a tube in fluid communication with the second outlet of the heat exchanger, the tube being configured to extend into the interior of the hot water cylinder when the adapter is secured to the hot water cylinder to thereby return the heated water to the hot water cylinder. The arrangement may include a connector arranged to fit into the outlet at the top of the hot water cylinder. For example, the hot water cylinder may have a 22mm compression outlet and the connector may be arranged to fit this outlet. The connector may comprise at least one O ring configured to seal the hot water cylinder at the top of the cylinder whilst providing a hot water outlet from the hot water cylinder via the arrangement. The O ring may permit rotation of the arrangement when the arrangement is fitted to the top of the hot water cylinder such that the arrangement may be rotated into a desired position after the arrangement is fixed to the hot water cylinder. The arrangement may include a hollow body. The hollow body may be configured to accommodate at least part of the tube. The hollow body may be configured to accommodate at least part of the tube concentrically within the hollow body. The hollow body may be configured such that the hollow interior of the hollow body forms the hot water outlet of the hot water cylinder. The tube may be arranged to extend through the hollow body and to protrude from the hollow body such that, when the arrangement is fitted to the top of the hot water cylinder, the tube extends into the interior of the hot water cylinder. The connector may be provided on the hollow body. The O ring may be provided on the exterior of the hollow body. The O ring may allow the sealing of the hot water cylinder at the top of the cylinder whilst providing a hot water outlet via the hollow body from the hot water cylinder. The O ring is preferably arranged to permit the hollow body to rotate when it is secured to the top of the hot water cylinder. This allows the hot water outlet to be rotated into a desired position after the hollow body is secured to the hot water cylinder, in order to enable the hot water outlet to be more easily connected to the existing domestic hot water pipes. A retaining plate may be provided to secure the hollow body after it has been rotated to the desired position and to prevent further rotation of the hollow body. The hollow body may be made from any suitable material, such as a metal, for example stainless steel or brass. The hollow body may comprise a first part and a second part, the second part being configured to be accommodated at least partially within the first part. The O ring may be arranged on the second part of the hollow body. At least one further O ring may be provided on the second part of the hollow body, the further O ring being arranged to be accommodated within the first part of the hollow body when the second part of the hollow body is accommodated at least partially within the first part of the hollow body. The further O ring may provide a seal between the interior of the first part of the hollow body and the exterior of the second part of the hollow body. The hollow body may have three holes through which liquid may pass in order to enter or exit the hollow body. The hollow body may be substantially a "T" shaped junction. The first part of the hollow body may have three holes and the second part of the hollow body may have two holes. The interior of the second part may be substantially funnel shaped. In use, the hollow body may be fitted to the top of a hot water cylinder and hot water from the heat exchanger may flow via the tube into the hot water cylinder and hot water from the hot water cylinder may flow via the hollow interior of the hollow body to a domestic hot water pipe. The cross sectional area of the tube is preferably substantially smaller than the cross sectional area of the hollow interior of the hollow body, such that the flow of hot water from the hot water cylinder through the hollow body is not significantly obstructed by the tube. The adapter may include further features as described above. According to an eighth aspect there is provided an adapter for connecting a hot water cylinder to a heat source, wherein the adapter comprises: a heat exchanger having a first inlet for receiving hot working fluid from a heat source and a first outlet for returning the cooled working fluid to the heat source after the working fluid has passed through the heat exchanger, and having a second inlet for receiving water for heating from the hot water cylinder and a second outlet for returning the heated water to the hot water cylinder after the water from the hot water cylinder has passed through the heat exchanger; a pump for pumping water from the hot water cylinder through the heat exchanger and back to the hot water cylinder; a temperature sensor arranged to detect the temperature of the working fluid from the heat source entering the first inlet of the heat exchanger; and a processor for controlling the pump and for detecting a state of operation of the heat source, the processor being configured to receive and use the temperature data from the temperature sensor to determine whether the heat source is active, and wherein the processor switches on the pump if it determines that the heat source is active. The processor may include a memory operatively coupled to the processor. The memory may store information and instructions for the processor. The processor may be configured to receive data from the temperature sensor and to compare the received temperature data with prestored temperature data and to switch on the pump if the received temperature data indicates that the temperature of the working fluid entering the first inlet of the heat exchanger is at least a predetermined temperature. A temperature sensor may be located at the first outlet of the heat exchanger. By providing a temperature sensor at the first inlet and a temperature sensor at the first outlet of the heat exchanger, the temperature of the working fluid entering the heat exchanger can be monitored and the difference in temperature between the working fluid entering the heat exchanger and leaving the heat exchanger can be monitored. The processor may be configured to receive information from further sensors including further temperature sensors and / or flow sensors as mentioned above. The processor may store this information in the memory. The pump may be controlled by the processor in order to control the flow rate of water through the heat exchanger. The processor and pump may be provided with a 24 Volts DC power source to provide power in a safe manner. A flow rate sensor may be provided at the hot water outlet of the hot water cylinder. The processor may receive and store information from the flow rate sensor. The processor may use this information to determine demand for domestic hot water at particular times of day. The processor may be provided with a machine learning algorithm and may be configured to use the machine learning algorithm to predict time periods when hot water usage is likely to be high. This information may be used in deciding when the heat source should be activated. The present invention will now be described by way of example only with reference to the following drawings: Figure 1 shows a side view of a cross section of an adapter in accordance with the present invention, the adapter being secured to the exterior of a hot water cylinder. Figure 2 shows an isometric view of the side and underside of an adapter in accordance with the present invention. Figure 3 shows a plan view of the adapter of figure 2, the top part of the housing of the adapter having been removed. Figure 4 shows an isometric view of the top and side of the adapter of figures 2 and 3, the top part of the housing of the adapter having been removed. Figure 5 shows an isometric view of an adapter in accordance with the present invention, the housing of the adapter being partially removed. Figures 6a - 6g show a support means for the adapter. Figure 6a is a plan view of the support means. Figure 6b shows an isometric view of the support means collapsed to its minimum height. Figure 6c shows an isometric view of the support means extended to its maximum height. Figure 6e shows an isometric view of a support means in position on a first type of cylinder and figure 6d shows the cross-sectional view of the cylinder and support means through line AA of figure 6e. Figure 6g shows an isometric view of a support means in position on a second type of cylinder and figure 6f shows the cross-sectional view of the cylinder and support means through line BB of figure 6g. Figures 7a - 7d show an arrangement of the adapter configured to be fitted to the top of a hot water cylinder. The arrangement includes a hollow body and, in figures 7a - 7d, a tube is present in the hollow body. Figure 7a shows a cross-sectional view of the arrangement, along its longitudinal length. Figure 7b shows an isometric view of the arrangement, when no retaining plate is present. Figure 7c shows the isometric view of figure 7b, when the retaining plate is present. Figure 7d shows an exploded view of the components and outlets of the arrangement. Figure 8a shows an isometric view of a disassembled tube of the adapter. Figure 8b shows a side view of an assembled tube of the adapter. Figure 9 shows a schematic diagram of a hot water cylinder including the tube and diffuser of the adapter. Figure 1 shows an adapter 1 mounted onto the top of a hot water cylinder 2. The hot water cylinder 2 may supply domestic hot water and may be of a direct or indirect type. The hot water cylinder in this figure is not one specifically designed to be used with a heat pump. The adapter 1 is configured to allow the cylinder to be connected to a heat source such as a heat pump. The cylinder 2 has a cold water inlet 22 at the bottom of the cylinder for receiving cold water to fill the cylinder. The cold water may come directly from the mains or via a cold water tank. The cylinder 2 has a control thermostat 20 for controlling the temperature of the hot water in the cylinder. In this cylinder 2, the thermostat 20 is located approximately at half the depth of the cylinder, but the thermostat could alternatively be located closer to the bottom or top of the cylinder. The cylinder has a jacket or lagging 45 to thermally insulate the cylinder. The cylinder 2 has an outlet hole 26 at the top of the cylinder, and an outlet fitting 25 is fitted into the hole 26. The outlet fitting 25 is connected to the adapter 1, and may be, for example, a 22mm compression outlet. The adapter 1 includes an arrangement 44 comprising a hollow body 15 connected to the outlet fitting 25, the hollow body defining a fluid path 27 which serves as the hot water outlet from the cylinder. The hollow body includes or is in fluid connection with a hot water outlet pipe 16 for connecting the cylinder hot water outlet to the domestic hot water pipes in a building. The adapter also includes a heat exchanger 3, a pump 4, a tube 5 and a housing 6. The heat exchanger in this example is a plate heat exchanger, but other types of heat exchangers might be used instead. The heat exchanger has a first inlet 10 for receiving hot working fluid from a heat pump (not shown) and a first outlet 11 (see figure 2) for returning the cooled working fluid to the heat pump after the working fluid has passed through the heat exchanger. A pipe 21 branches off from the cold water inlet 22 of the cylinder 2 and feeds cold water from the bottom of the cylinder to a second inlet 12 of the heat exchanger 3. The cold water is heated in the heat exchanger 3 by the working fluid from the heat pump and the heated water then exits the heat exchanger 3 via a second outlet 13. Tube 5 is in fluid communication with the second outlet 13 of the heat exchanger 3 and the heated water is returned to the cylinder 2 via the tube 5. The pump 4 has an inlet 24 and an outlet 23 and circulates water from the bottom of the hot water cylinder 2 via pipe 21 through the heat exchanger 3 and back to the cylinder 2 via the tube 5. In this example, the housing 6 comprises several sections. The sections may be detachable from each other. The hollow body 15 and hot water outlet pipe 16 are housed in a first section 7 of the housing. The heat exchanger 3 and pump 4 are housed in a second section 8 of the housing. A cover 9 is provided to protect the heat exchanger and pump whilst allowing easy access to them for maintenance purposes. In this example, the first section 7 of the housing is rotatable with respect to the second section 8 of the housing. This enables the hot water outlet pipe 16 to be rotated to an optimal position for connection to the hot water system of the building without affecting the position of the inlets and outlets of the heat exchanger. In this example, the adapter 1 includes support means 14 for supporting the adapter on the top of a hot water cylinder 2. The support means of this example are height adjustable to enable the support means to stably support the adapter on a variety of hot water cylinders, regardless of their diameter or their shape. In this example, the hot water cylinder has a relatively flat top, but other cylinders, such as shown in figure 9 for example, may have a more rounded top. By providing a height adjustable support means, this support means may be used with a wide variety of cylinders. In this example, the heated water exiting the second outlet 13 of the heat exchanger passes through the pump inlet 24, the pump 4 and the pump outlet 23 and into the tube 5. The tube 5 extends through the hollow body 15, through the outlet fitting 25 of the cylinder 2 and into the interior of the cylinder. This allows the heated water from the heat exchanger 3 to be returned to the cylinder 2. The tube 5 is accommodated within the fluid path 27 defined by the hollow body 15, and preferably has a cross sectional area that is relatively small compared to the cross sectional area of the fluid path 27 and the outlet fitting 25 of the cylinder 2 such that the hot water outflow from the cylinder to the hot water system of the building is not significantly impeded. This in turn ensures that the pressure loss in the hot water system of the building due to use of the adapter 1 is minimised. Turning now to figure 9, which shows a schematic diagram of a hot water cylinder 2 with an adapter (not shown for clarity) fitted to the top of the hot water cylinder, it can be seen that the water in the hot water cylinder becomes stratified, according to its temperature. As colder water is denser than warmer water, the colder water in the cylinder will be found at the bottom of the cylinder and the warmest water will be found at the top of the cylinder, in the absence of any active mixing of the water in the cylinder. Colder water is taken from the bottom of the cylinder through the cold water inlet 22 and is pumped by the pump 4 via the pipe 21 to the heat exchanger 3 located within the adapter 1. Heated water is returned to the cylinder from the adapter 1 via the tube 5. The hotter water at the top of the cylinder is the water which will be taken from the cylinder for use when a hot water outlet, such as a tap, is operated in the building. It is therefore desirable to ensure that the hotter water near the top of the cylinder is not disturbed by the water returned to the cylinder via the tube 5. In order to minimise turbulence in the hotter water near the top of the cylinder and to prevent this water mixing with colder water in the cylinder, which would impact the temperature of the hot water running from the taps in the building, the tube 5 is configured to extend a substantial way into the cylinder. In the example shown in figure 9, the tube 5 extends past the middle of the cylinder. The tube may alternatively extend substantially to or slightly short of the middle of the cylinder, or may extend deeper into the cylinder. The tube preferably extends into the cylinder deep enough that there is generally a sufficient amount of relatively undisturbed hot water available to the user whilst the pump 4 is in operation. The tube 5 preferably extends such that it is level with, or below, the control thermostat 20 in the cylinder. In order to accommodate different sizes of cylinder, the tube 5 may include one or more extension portions 17. By providing extension portions one design of tube 5 may be used for a variety of cylinders, regardless of their size. This is advantageous as the same adapter can be used for a variety of cylinders, and the tube length can be adapted to the cylinder by using the extension portions until the tube 5 is of a desired length. In order to further reduce turbulence and reduce mixing of warmer and colder water in the cylinder, the tube 5 may include a diffuser 18. The diffuser 18 is preferably located at the end of the tube 5 within the cylinder (ie the distal end of the tube 5 furthest from the adapter 1). The diffuser 18 is preferably positioned such that it is level with, or below, the control thermostat 20 of the cylinder 2. In this example, the diffuser 18 has a plurality of outlets 19 located circumferentially around the diffuser and along the length of the diffuser. This creates a diffusion zone 29 in the cylinder around the diffuser. Above the diffusion zone 29, in the hotter water zone 28, there is relatively little turbulence and mixing of water. Below the diffusion zone 29, in the cooler water zone 30, there may be some turbulence and mixing of water but this will not significantly affect the hotter water zone 28. The diffuser may be designed to lessen the turbulence caused by the returning water as much as possible. Turning back to figure 2, this shows an exterior view of the side and underside of the adapter 1. The components of the adapter are housed in the housing 6. The housing 6 includes a first section 7, a second section 8 and a cover 9. The first inlet 10 of the heat exchanger and the first outlet 11 of the heat exchanger, as well as the heat exchanger 3 itself, are located in the second section 8 of the housing 6. The first inlet 10 receives hot working fluid from the heat pump and the cooled working fluid is returned to the heat pump via first outlet 11. The second section of the housing 6 also houses the second inlet 12 to the heat exchanger. The first section 7 of the housing 6 houses the hot water outlet pipe 16 through which hot water exiting the cylinder flows and which, in use, is to be connected to the hot water system of the building. The first section 7 and the second section 8 of the housing 6 are rotatable with respect to each other about their longitudinal axis. This allows the hot water outlet pipe 16 to be rotated to a position convenient for connecting to the hot water system of the building without affecting the position of the inlets and outlets of the heat exchanger, thereby reducing the need for complex pipework which in turn requires additional space to accommodate. The housing 6 is supported by support means 14. In this example the support means 14 is a ring stand which is connected to the lower part of the housing 6. The tube 5 extends from the bottom of the housing 6 and, when the adapter is fitted to a hot water cylinder, will extend into the interior of the hot water cylinder. The adapter includes a connector 31 for connecting the adapter to the hot water cylinder. For example, the hot water cylinder may be fitted with an outlet fitting 25 such as a 22mm compression outlet and the connector 31 may be configured for use with such an outlet. Figure 3 is a plan view of the adapter of figure 2, with the cover 9 removed. The heat exchanger 3, its first inlet 10 from the heat pump and its first outlet 11 to the heat pump can be seen as well as circulation pump 4 and processor enclosure 32. These components of the adapter are housed in the second section 8 of the housing 6. The pump inlet 23 and pump outlet 24 can also be seen. The pump inlet 23 is in fluid communication with the second outlet 13 of the heat exchanger 3 and the pump outlet 24 is in fluid communication with the tube 5. In use, water heated by the heat exchanger 3 exits the heat exchanger via the second outlet 13 and passes through the pump 4 to the tube 5. The tube 5 extends through hollow body 15 and returns the heated water to the hot water cylinder 2. The hot water outlet pipe 16 can also be seen in figure 3. In this example, the hot water outlet pipe 16 is shown as being rotationally positioned between the first inlet 10 and the first outlet 11 of the heat exchanger, but, as explained previously, the hot water outlet pipe 16 is able to be rotated to any suitable position with respect to the first inlet 10 and first outlet 11. In this example, temperature sensors 33 and 34 are provided in the adapter. Temperature sensor 33 is attached to the first outlet 11 of the heat exchanger, and temperature sensor 34 is attached to the first inlet 10 of the heat exchanger 3. The temperature sensors may be, for example, clip on sensors configured to be attached to the inlet and outlet pipes. The temperature sensors 33, 34 may detect and monitor the temperature of the working fluid entering and exiting the heat exchanger 3. Further temperature sensors (not shown) may be located at the second inlet 12 of the heat exchanger to monitor the temperature of the water from the cylinder entering the heat exchanger, and / or at the second outlet 13 of the heat exchanger to monitor the temperature of the water being returned to the cylinder from the heat exchanger. Optionally, flow sensors (not shown) may be provided to monitor the flow rate of the working fluid passing through the heat exchanger and / or the flow rate of the water passing through the heat exchanger. A temperature sensor (not shown) and / or a flow sensor (not shown) may additionally be provided in the hot water outlet pipe 16 to monitor the temperature and / or flow rate of the hot water exiting the cylinder. Figure 4 is an isometric view of the adapter of figure 2, with the cover 9 of the housing 6 removed. In this example, the housing 6 has a further section 35 which is detachable to allow easy access to the pump 4 for maintenance purposes. In this example, the housing supports and houses the components of the adapter and provides insulation to the heat exchanger, pump and pipework. Figure 5 shows an isometric view of an adapter similar to those already described. In this figure, for clarity the housing is not shown except for the first section 7 of the housing 6. The adapter includes a heat exchanger 3 being a plate heat exchanger. The heat exchanger has a first inlet 10 for receiving hot working fluid from the heat pump and a first outlet 11 for returning cooled working fluid to the heat pump. The heat exchanger has a second inlet 12 for receiving colder water from the bottom of the cylinder and a second outlet 13 through which the heated water exits the heat exchanger. The heated water then passes through circulation pump 4 and is returned to the cylinder via tube 5. The first section 7 of the housing accommodates the hollow body 15 and the hot water outlet pipe 16. The hollow body 15 and the hot water outlet pipe 16 may be rotated with the first section of the housing 7 with respect to the heat exchanger 3, pump 4 and the inlets and outlets of the heat exchanger 3. Figures 6a to 6g show an example of a support means 14 for supporting the adapter on the top of a hot water cylinder. In this example, the support means is a height adjustable ring stand comprising two rings 36, 37. The inner ring 36 has a smaller diameter than the outer ring 37 and is configured to fit within the outer ring 37. The inner ring has three protrusions 38, 39, 40 located substantially equidistantly around the outside of the ring. In this example the rings 36, 37 are of similar width. The outer ring 37 has three slotted holes 41, 42, 43 located substantially equidistantly around the ring. In this example, the slotted holes extend at an angle across a substantial part of the width of the outer ring 37. The protrusions 38, 39, 40 are all located near one edge of the ring and each protrusion is configured to extend into a slotted hole. As can be seen in figures 6b and 6c, the rings 36, 37 may be rotated relative to each other to adjust the height of the support means 14 between a minimum height configuration where the inner ring 36 is positioned substantially within the outer ring 37 as shown in figure 6b and a maximum height configuration where the inner ring 36 extends outside of the outer ring 37 as far as the protrusion and slotted hole arrangement will permit as shown in figure 6c. The height of the support means may be fixed at the minimum height, the maximum height or at any desired height in between the maximum and minimum heights, in order to accommodate the shape of the cylinder. For example, to fix the height of the support means a nut or cap may be used to fix each protrusion in the desired position within its associated slotted hole. Figures 6d to 6g show how the support means may be used on different cylinder types. In the example shown in figures 6d and 6e, the cylinder 2a has a substantially flat top and the support means is used in its minimum height configuration. In the example shown in figures 6f and 6g, the cylinder 2b has a dome top and the support means is used in its maximum height configuration in order to stably support the adapter on the hot water cylinder 2b. The support means may be integrally formed with the housing (not shown in figures 6a to 6g) or the housing may be configured to be attached to the support means. Figure 7a shows a cross-sectional view of an arrangement 44 configured to be fitted to the top of the hot water cylinder 2. The arrangement 44 includes a hollow body 15 having a first part 46 and a second part 47. The second part 47 of the hollow body is fixed to the first part 46 so that the first and second parts are joined together. In this example, the upper exterior portion 48 of the second part 47 has a male thread and the lower interior portion 49 of the first part 46 has a female thread, the male and female threads being configured such that the first and second parts 46, 47 can be screwed together to form the hollow body 15. The hollow body 15 defines a fluid path 27, the fluid path 27 being the hollow interior of the hollow body. The fluid path 27 is the outlet from the cylinder to the hot water system. One or more seals, for example O-rings 50, may be provided to prevent fluid leakage from the hollow body 15. A tube 5 is accommodated within the hollow body 15 as can be seen in figures 7a-7d. The first part 46 of the hollow body has a female thread located in its upper interior portion 51 and the tube 5 has a male thread located at its upper end 52, the male and female threads being configured such that the tube 5 and the first part 46 of the hollow body can be screwed together. This permits the tube 5 to be fixed in position in the interior of the hollow body 15. The tube 5 extends from the upper interior portion 51 of the first part 46 of the hollow body, through the hollow interior of the first and second parts 46, 47 of the hollow body, and the lower end 53 of the tube 5 extends outside of the hollow body. When the tube 5 is positioned within the fluid path 27 in the interior of the hollow body, there is sufficient space to allow hot water to exit the cylinder, without a significant loss of pressure. The lower exterior portion 55 of the second part 47 of the hollow body 15 includes a connector 31 configured to fit into the outlet fitting 25 of the cylinder. The connector 31 includes one or more O-rings 56 configured to fit into the outlet fitting 25 of the cylinder to seal the hot water outlet of the cylinder whilst permitting rotation of the hollow body about its longitudinal axis when the hollow body is fitted into the outlet fitting 25 of the cylinder. This allows the hot water outlet pipe 16, which is connected to the hollow body, to rotate with the hollow body about the longitudinal axis of the hollow body in order to be positioned optimally for connection to the hot water system of the building after the adapter is fitted to the cylinder. The cross-sectional area of the tube 5 is sufficiently small with respect to the cross sectional area of the fluid path 27 at its narrowest point (ie where the hollow body is fitted into the outlet fitting 25 of the cylinder) such that the flow of hot water exiting the hot water cylinder through the hollow body 15 is not significantly obstructed by the tube 5. The top of the tube 5 is in fluid communication with a pipe 56 which is connected to the top of the hollow body 15. The pipe 56 is in fluid communication with the second outlet 13 of the heat exchanger 3. The pipe 56 and the hot water outlet pipe 16 are each connected to a different outlet of the first part 46 of the hollow body 15. The pipe 56 and the hot water outlet pipe 16 of this example include push fit adapters for easy removal, servicing and installation of the components of the adapter. The arrangement 44 includes a retaining plate 57 for registering the position of the hollow body 15 in the adapter. The hollow body includes retaining holes 59 for receiving retaining pins 58 used to keep the pipe 56 and the hot water outlet pipe 16 in position. When the adapter 1 is fitted to the top of a hot water cylinder 2, the tube 5 extends into the interior of the hot water cylinder. The tube 5 is in fluid communication with the second outlet 13 of the heat exchanger 3 and returns the heated water back to the cylinder. The tube has an internal diameter of approximately 10mm. The lower end 53 of the tube 5 has a thread for receiving tube extension portions 17 as explained with reference to figures 8a and 8b. Figure 8a shows the tube 5 of the adapter 1. The upper end 52 of the tube 5 has a male thread for use in fixing the tube 5 in position within the hollow body 15 as explained with reference to figures 7a-7d. The lower end 53 of the tube 5 is configured to attach to an extension portion 17 to extend the length of the tube. In this example, the lower end of the tube 5 has a male thread and one end (the upper end) 60 of the extension portion 17 has a female thread, the threads being configured to allow the lower end of the tube 5 to be screwed into the end 60 of the extension portion 17. The extension portion 17 has a male thread at its other end (the lower end) 61 to allow the other end 61 of the extension portion to be fixed to a further extension portion 17 if desired. In this manner one or more extension portions may be attached to the tube 5 to extend the length of the tube 5. The extension portions in this example each have the same length, but different extension portions may have different lengths if desired. The extension portions in this example have a length of 300mm, but one or more different lengths may be used. The extension portions 17 in this example have a greater cross-sectional area than that of the tube 5, which may help in slowing the speed of the heated water being returned to the cylinder. Using one or more extension portions allows the tube to be used with a variety of different cylinders, regardless of their size. If a cylinder is very tall, then more extension portions can be used until the tube 5 is at the required depth in the cylinder. As can be seen in Figure 8b, the tube 5 in this example has been extended by using two extension portions 17 which are connected together at 54 and a diffuser 18. The diffuser 18 is at the very end of the extended tube and includes a plurality of outlets 19. The diffuser helps to reduce turbulence in the cylinder when the hot water is returned to the cylinder. By using a diffuser and by returning the hot water to the cylinder at a reasonable depth, the hot water at the top of the cylinder is not disturbed thus enabling hot water at a desired temperature to be provided to users even when the water in the cylinder is being heated. As previously explained with respect to figure 9, it is desirable to provide the diffuser at a similar level to, or below, the control thermostat of the cylinder. The above embodiments are to be understood as illustrative examples. Further embodiments, aspects or examples are envisaged. It is to be understood that any feature described in relation to any one embodiment, aspect or example may be used alone, or in combination with other features described, and may also be used in combination with one or more features of any other of the embodiments, aspects or examples, or any combination of any other of the embodiments, aspects or examples. Furthermore, equivalents and modifications not described above may also be employed without departing from the scope of the invention, which is defined in the accompanying claims.

Claims

1. An adapter for connecting a hot water cylinder to a heat source, wherein the adapter is configured to be secured to the exterior of a hot water cylinder at the top of the hot water cylinder, and wherein the adapter comprises:a heat exchanger having a first inlet for receiving hot working fluid from a heat source and a first outlet for returning the cooled working fluid to the heat source after the working fluid has passed through the heat exchanger, and having a second inlet for receiving water for heating from the hot water cylinder and a second outlet for returning the heated water to the hot water cylinder after the water from the hot water cylinder has passed through the heat exchanger;a pump for pumping water from the hot water cylinder through the heat exchanger and back to the hot water cylinder;a fluid path arranged to allow hot water to flow out from the top of the hot water cylinder through the adapter to a hot water pipe, the fluid path being a hot water outlet from the hot water cylinder; anda tube in fluid communication with the second outlet of the heat exchanger, the tube being configured to extend into the interior of the hot water cylinder when the adapter is secured to the hot water cylinder.

2. An adapter according to claim 1, wherein the adapter further comprises an arrangement configured to be fitted to the top of a hot water cylinder, the arrangement being further configured to provide the fluid path being a hot water outlet from the hot water cylinder and the arrangement being configured to accommodate the tube.

3. An adapter according to claim 2, wherein the arrangement comprises a hollow body, the hollow body being configured to accommodate the tube within the hollow body.

4. An adapter according to claim 2 or claim 3, wherein the hollow body comprises a first part and a second part, the second part being configured to be accommodated at least partially within the first part.

5. An adapter according to claim 3 or claim 4, wherein the hollow body comprises at least one O ring being arranged to permit the hollow body to rotate when it is secured to the top of thehot water cylinder such that the hot water outlet is rotatable to a desired position when the hollow body is fixed to the hot water cylinder.

6. An adapter according to any of the preceding claims wherein the adapter comprises height adjustable support means for supporting the adapter on the top of a hot water cylinder.

7. An adapter according to claim 6 wherein the support means comprises at least two rings connected to each other, the rings having different diameters such that one ring is able to fit concentrically within another ring, the rings being telescopically slidable with respect to each other such that the height of the support means is adjustable by moving one ring relative to another ring.

8. An adapter according to any of the preceding claims wherein the tube is extensible.

9. An adapter according to claim 8 wherein the tube comprises at least two portions configured to be joined together.

10. An adapter according to claim 8 or claim 9 wherein the tube comprises a diffuser located at or near to the end of the tube remote from the heat exchanger.

11. An adapter according to any of the preceding claims wherein the adapter comprises a processor configured to control the operation of the pump, the processor being configured to switch on the pump when the heat source is active.

12. An adapter according to any of the preceding claims wherein the adapter comprises a temperature sensor located at the first inlet of the heat exchanger.

13. An adapter according to any of the preceding claims wherein the adapter comprises a housing, the housing containing and supporting within it the heat exchanger and the pump.

14. An adapter according to claim 13 wherein the housing comprises a plurality of sections, at least one section being rotatable with respect to the other section or sections, the hot water outlet being provided in a different section to the heat exchanger and pump such that the hot water outlet may be rotated with respect to the heat exchanger and pump.

15. An adapter according to any of the preceding claims wherein the heat exchanger is a plateheat exchanger.5 16. A cylinder adapted for connection to a heat pump, the cylinder comprising an adapteraccording to any of the preceding claims.10s

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