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 enabling efficiency of the heating system.

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. In an alternative approach, cold water may be drawn from the bottom of the cylinder by a pump and passed through a plate heat exchanger and returned to the top of the tank to rapidly inject hot water into the top of the cylinder.

One or more pumps may be used upstream or downstream of the plate heat exchanger in conjunction with check valves, flow switches or multi-port solenoid valves to allow the flow path back to the tank to either go directly to the top, delivering maximum temperature/reheat performance or to the bottom of the tank to attain maximum system efficiency.

In general, having potable water in the heating system will gradually cause a build up of scale (e.g. limescale) within the heating system, particularly at its hottest points, such as in the heat exchanger. Scale forming in the heat exchanger may lead to a reduction in performance by reducing the heat transfer rate across the heat exchanger. It is therefore necessary to periodically descale the heating system and the heat exchanger in particular. The use of a plate heat exchanger introduces a challenge when servicing the product. In a system comprising a heat pump to heat the potable water, the heat is provided from the heat pump to the plate heat exchanger typically by way of a heat transfer fluid such as a high-pressure refrigerant. In order to service and/or descale the plate heat exchanger a technician may be required to de-gas the plate heat exchanger, dismantle the unit and manually clean the system before reassembly and refill, which is a time-consuming process. Moreover, refrigerants are controlled substances which are problematic when allowed to leak into the atmosphere. In the case of R143a refrigerant, when allowed to escape, this substance has a global warming potential which is >1400 times that of CO2. Other refrigerants and heat transfer fluid also pose challenges, for example, propane (R-290) is a flammable substance, which poses safety risks, and degassing a system which uses CO2 as the refrigerant involves working with systems at hazardous pressures.

There is a need for a system for heating water that can be descaled more safely, more simply and in a more environmentally friendly manner. There is also a need for a system for heating water that can avoid heat losses.

Integration

According to a first aspect there is provided an integrated heat pump water tank comprising: a heat pump for providing heat; a tank for containing heated water; a heat exchanger (preferably arranged externally to the tank) for transferring heat from the heat pump to water from the tank; a conduit providing a flow path (preferably external to the tank) from a portion of the tank via the heat exchanger back to the tank; a pump arranged to pump water through the conduit. By providing at least the heat pump and the tank in an integrated heat pump water tank compactness and ease of installation can be enabled. Versatile heating of the tank and use of the heat pump can be enabled by a heat exchanger arranged externally to the tank for transferring heat from the heat pump to water from the tank, a conduit providing a flow path external to the tank from a portion of the tank via the heat exchanger back to the tank and a pump arranged to pump water through the conduit.

The heat pump and the tank are preferably contained in a common housing or share a common fascia or are fixedly attached to one another. The pump is preferably a variable speed pump. The tank may be arranged to bear at least partially the heat pump. A tank wall or a housing of the tank may be adjoined to a housing of components of the heat pump. At least a condenser of the heat pump may be mounted to the tank. A condenser of the heat pump is preferably provided external to the tank. One or more of: a compressor of the heat pump; an expander of the heat pump; and an evaporator of the heat pump may further be mounted to the tank. At least a condenser of the heat pump and the tank may be contained in a common housing or share a common fascia or be fixedly attached to one another. One or more of: a compressor of the heat pump; an expander of the heat pump; and an evaporator of the heat pump may further be contained in the common housing or share the common fascia or be fixedly attached to the tank. At least a portion of the heat pump and the tank are contained in a common housing or share a common fascia or are fixedly attached to one another.

The conduit may provide a flow path (preferably external to the tank) from a lower portion of the tank to an upper portion of the tank via the heat exchanger. The conduit may provide a flow path (preferably external to the tank) from a lower portion of the tank back to the lower portion of the tank via the heat exchanger. A first branch of the conduit may provide a first flow path from the heat exchanger to an upper portion of the tank and a second branch of the conduit may provide a second flow path from the heat exchanger to an intermediate or lower portion of the tank. The conduit may further comprise a valve arrangement arranged in the flow path for selection of the first branch of the conduit or the second branch of the conduit. For compactness the heat pump may be arranged above the tank in use. The heat pump preferably has a substantially similar or smaller footprint than the tank unit. The heat pump and the tank may be mounted to a common frame.

For compactness and ease of installation the heat pump unit preferably comprises the heat exchanger. For compactness and versatility the heat exchanger may be a plate heat exchanger.

For ease of assembly the heat pump unit and/or the tank unit may comprise one or more mounting guides for positioning and orienting the heat pump to the tank. For ease of assembly the heat pump and/or the tank may comprise one or more attachment means for fixing the heat pump and the tank to one another. For ease of assembly the heat pump and/or the tank unit may comprise one or more sensors for sensing presence or absence of a heat pump at a tank.

The conduit may further comprise a non-return valve arranged to prevent water flow from an upper portion of the tank a lower portion of the tank via the conduit. The integrated heat pump water tank may form part of a heating system as aforementioned.

The integrated heat pump water tank may comprise a descaling system wherein the conduit provides a descaling flow path arranged to carry descaling fluid to the plate heat exchanger and to carry descaling fluid away from the plate heat exchanger, wherein the descaling flow path includes the pump.

According to another aspect there is provided a modular (and/or integrated) heat pump water tank comprising: a tank unit including a tank for containing heated water; a heat pump unit including a heat pump for providing heat to the tank; and a heat exchanger (preferably arranged externally to the tank unit) for transferring heat from the heat pump to water from the tank.

Preferably the tank unit and the heat pump unit are modular. Modularity can enable replacement of one of the units while the other unit can remain installed and used further. Preferably the tank unit and the heat pump unit are adapted for mounting to one another to form an integrated heat pump water tank. The integrated heat pump water tank may be as aforementioned.

For modularity the heat pump unit and the tank unit are preferably reversibly attachable to one another and/or detachable without damage. The heat pump unit and the tank unit may be contained in a common housing or share a common fascia or be fixedly attached to one another. The heat pump unit and the tank unit may be shaped to fit one another. The tank unit may be adapted to bear at least partially the heat pump unit. A tank wall or a housing of the tank unit may be adapted to receive a housing of the heat pump unit or components of the heat pump unit. The heat pump unit may include at least a condenser of the heat pump. The heat pump unit may include one or more of a compressor of the heat pump; an expander of the heat pump; and an evaporator of the heat pump.

For compactness and convenient load distribution the heat pump unit may be arranged above the tank unit in use. The heat pump unit preferably has a substantially similar or smaller footprint than the tank unit. The heat pump unit and/or the tank unit may include a frame or a housing. A frame or housing can serve for attachment of the units to one another and also for attachment of component parts within a unit.

For compactness and ease of installation the heat pump unit preferably comprises the heat exchanger. For compactness and versatility the heat exchanger may be a plate heat exchanger.

For ease of assembly the heat pump unit and/or the tank unit may comprise one or more mounting guides for positioning and orienting the heat pump unit to the tank unit. For ease of assembly the heat pump unit and/or the tank unit may comprise one or more attachment means for fixing the heat pump unit and the tank unit to one another. For ease of assembly the heat pump unit and/or the tank unit may comprise one or more module sensors for sensing presence or absence of a heat pump unit at a tank unit. For ease of configuration and control the heat pump unit and/or the tank unit may comprise one or more module recognition components for providing characteristics to an associated tank unit or heat pump unit and/or identifying characteristics of an associated tank unit or heat pump unit.

The modular integrated heat pump water tank may further comprise a conduit providing a flow path (preferably external to the tank) from a lower portion of the tank to an upper portion of the tank via the heat exchanger. The modular integrated heat pump water tank may further comprise a conduit providing a flow path (preferably external to the tank) from a lower portion of the tank back to the lower portion of the tank via the heat exchanger. The modular integrated heat pump water tank may further comprise a conduit providing a flow path (preferably external to the tank) from the tank (preferably from a lower portion of the tank) to the heat exchanger and back to the tank (preferably to a lower portion of the tank, optionally with a second branch to an upper portion of the tank). The modular integrated heat pump water tank may further comprise a pump arranged in the flow path to pump fluid along the conduit. The pump is preferably a variable speed pump. For compactness and ease of installation the heat pump unit may comprise the pump. The modular integrated heat pump water tank may further comprise a valve arrangement arranged in the flow path for selection of a first branch of the conduit or a second branch of the conduit. The modular integrated heat pump water tank may further comprise a non-return valve arranged in the conduit to prevent water flow from an upper portion of the tank a lower portion of the tank via the conduit. The modular integrated heat pump water tank may be an integrated heat pump water tank as aforementioned. The modular integrated heat pump water tank may form part of a heating system as aforementioned.

According to another aspect there is provided a kit of parts for a modular integrated heat pump water tank, the kit of parts comprising: a tank unit including a tank for containing heated water; a heat pump unit including a heat pump for providing heat to the tank; and a heat exchanger (preferably for arrangement externally to the tank unit) for transferring heat from the heat pump to water from the tank; wherein the tank unit and the heat pump unit are reversibly attachable to one another to form a modular integrated heat pump water tank. Modularity can enable replacement of one of the units while the other unit can remain installed and used further.

For compactness and convenient load distribution the heat pump unit and/or the tank unit may be adapted for arranging the heat pump unit above the tank unit in use.

For compactness and ease of installation the heat pump unit preferably comprises the heat exchanger. For compactness and versatility the heat exchanger may be a plate heat exchanger.

For ease of assembly the heat pump unit and/or the tank unit may comprise one or more mounting guides for positioning and orienting the heat pump unit to the tank unit. For ease of assembly the heat pump unit and/or the tank unit may comprise one or more attachment means for fixing the heat pump unit and the tank unit to one another. For ease of assembly the heat pump unit and/or the tank unit may comprise one or more module sensors for sensing presence or absence of a heat pump unit at a tank unit. For ease of configuration and control the heat pump unit and/or the tank unit may comprise one or more module recognition components for providing characteristics to an associated tank unit or heat pump unit and/or identifying characteristics of an associated tank unit or heat pump unit.

The kit of parts may further comprise a conduit for providing a flow path (preferably external to the tank) from a lower portion of the tank to an upper portion of the tank via the heat exchanger. The kit of parts may further comprise a conduit for providing a flow path (preferably external to the tank) from a lower portion of the tank back to the lower portion of the tank via the heat exchanger. The kit of parts may further comprise a conduit for providing a flow path (preferably external to the tank) from the tank (preferably from a lower portion of the tank) to the heat exchanger and back to the tank (preferably to a lower portion of the tank, optionally with a second branch to an upper portion of the tank). The kit of parts may further comprise a pump arranged in the flow path to pump fluid along the conduit. The pump is preferably a variable speed pump. The kit of parts may further comprise a valve arrangement arranged in the flow path for selection of a first branch of the conduit or a second branch of the conduit).

The kit of parts may further comprise a non-return valve arranged in the conduit to prevent water flow from an upper portion of the tank a lower portion of the tank via the conduit. The kit of parts may be for a modular integrated heat pump water tank as aforementioned. The kit of parts may be for an integrated heat pump water tank as aforementioned. The kit of parts may be for a heating system as aforementioned.

Non-return valve

According to another aspect there is provided a heating system comprising: a heat pump for providing heat; a tank for containing heated water; a heat exchanger arranged externally to the tank for transferring heat from the heat pump to water from the tank; a conduit providing a flow path external to the tank from a lower portion of the tank to an upper portion of the tank via the heat exchanger; a pump arranged to pump water through the conduit from the lower portion of the tank to the upper portion of the tank via the heat exchanger; and a non-return valve arranged in the conduit to prevent water flow from the upper portion of the tank the lower portion of the tank via the conduit. By inclusion of a non-return valve heat losses can be reduced.

The tank and the heat pump may be an integrated heat pump water tank (optionally a cylinder). This can provide a particularly compact heating system. The tank is preferably for containing pressurised heated water. The tank and the heat pump may be a modular integrated heat pump water tank. The tank and the heat pump may be a modular heat pump water tank.

The non-return valve may be arranged downstream of the pump, and preferably upstream of the heat exchanger. For efficiency the non-return valve may be a swing valve.

The non-return valve is preferably to prevent water flow from the upper portion of the tank the lower portion of the tank via the conduit when the pump is inactive. The non-return valve is preferably to prevent thermal gradient driven flow in the conduit.

The heat exchanger may be a plate heat exchanger. A plate heat exchanger can enable particularly compact and effective heat transfer. For compactness and avoidance of heat losses the heat exchanger may be arranged at the heat pump. For compactness the heat pump may be arranged above the tank. The heat exchanger may be arranged above the tank. The heat exchanger may be arranged external to a thermal insulation of the tank.

For adaptability to heating requirements and heat availability, a first branch of the conduit may provide a first flow path from the heat exchanger to an upper portion of the tank and a second branch of the conduit may provide a second flow path from the heat exchanger to an intermediate or lower portion of the tank. A valve arrangement may be provided for selection of the first or second flow path.

The pump may be a variable speed pump. A variable speed pump can enable versatility and different modes of operation. The pump may be arranged upstream of the heat exchanger.

The conduit preferably provides a flow path from the bottom of the tank to an upper portion of the tank via the heat exchanger. The conduit is preferably arranged external to a thermal insulation of the tank.

The heating system may further comprise one or more sensors for sensing a temperature of the heating system. The heating system may comprise an array of temperature sensors for sensing temperatures at different locations in the tank.

The heating system may further comprise a controller configured to control the pump to continue pumping after the heat pump is switched off. The controller may be configured to control the heat pump to switch off.

According to another aspect there is provided a heating system comprising: a heat pump for providing heat; a tank for containing heated water; a heat exchanger arranged externally to the tank for transferring heat from the heat pump to water from the tank; a conduit providing a flow path external to the tank from a lower portion of the tank to an upper portion of the tank via the heat exchanger; a pump arranged to pump water through the conduit from the lower portion of the tank to the upper portion of the tank via the heat exchanger; and a controller configured to control the pump to continue pumping after the heat pump is switched off. By controlling the pump to continue pumping after the heat pump is switched off heat losses can be reduced.

For system simplicity the controller may be configured to control the pump to continue pumping for a pre-determined period after the heat pump is switched off. The pre-determined period may be at least 3 seconds, preferably at least 5 seconds, further preferably at least 10 seconds, yet further preferably in the range of 10-30 seconds or around 15 seconds.

For robust avoidance of heat losses the controller may be configured to control the pump to continue pumping after the heat pump is switched off until a pre-determined temperature is sensed in water between the heat exchanger and an outlet of the conduit at the upper portion of the tank.

The tank and the heat pump may be an integrated heat pump water tank (optionally a cylinder). The tank and the heat pump may be a modular integrated heat pump water tank. The heat exchanger may be a plate heat exchanger. The heat exchanger and/or the conduit may be arranged external to a thermal insulation of the tank. A first branch of the conduit may provide a first flow path from the heat exchanger to an upper portion of the tank and a second branch of the conduit may provide a second flow path from the heat exchanger to an intermediate portion of the tank. A valve arrangement may be provided for selection of the first or second flow path.

The heating system may further comprise one or more sensors for sensing a temperature of the heating system, preferably an array of temperature sensors for sensing temperatures at different locations in the tank.

The heating system, the heat pump, the tank, the heat exchanger, the conduit, the pump and/or the controller may be as aforementioned.

Descaling

According to a further aspect there is provided a heating system comprising: a plate heat exchanger having a first side for connection to a heat pump and a second side for receiving fluid to be heated; a pump arranged to pump fluid through the second side of the plate heat exchanger; a first flow path arranged to carry water to be heated from a water source to the second side of the plate heat exchanger and to carry heated water away from the second side of the plate heat exchanger; and a second flow path arranged to carry descaling fluid to the second side of the plate heat exchanger and to carry descaling fluid away from the second side of the plate heat exchanger, wherein the first flow path and the second flow path include the pump.

By providing a second flow path in the heating system for descaling fluid which is different than the first flow path (for example, in that it originates from and ends at a different location to the first flow path) but which nevertheless includes the plate heat exchanger and pump lying on the first flow path, the plate heat exchanger may be descaled without having to dismantle the plate heat exchanger. This is particularly advantageous since it is potentially difficult and time-consuming to safely dismantle the plate heat exchanger, especially if the heat source connected to the plate heat exchanger is a heat pump since the refrigerant may be a controlled substance and/or delivered at high pressure. The plate heat exchanger can be descaled reusing the same pump which pumps the (potable) water through the plate heat exchanger for heating avoiding the need for additional pumps to deliver the descaling fluid.

For simple delivery of the descaling fluid to the heating system, the second flow path may comprise a descaling fluid reservoir. For effective delivery to the plate heat exchanger and removal of the descaling fluid from the plate heat exchanger, the second flow path may be arranged to carry descaling fluid from the descaling fluid reservoir to the plate heat exchanger and away from the plate heat exchanger.

The descaling fluid reservoir may be for containing a descaling acid for dissolving calcium carbonate. The descaling fluid may be a descaling acid for dissolving calcium carbonate.

To provide a system in which descaling fluid may be continuously circulated thereby to reduce wastage of descaling fluid, the second flow path is preferably a loop. The second flow path may be arranged to carry descaling fluid from a descaling fluid reservoir to the second side of the plate heat exchanger and to carry descaling fluid from the second side of the plate heat exchanger back to the descaling fluid reservoir.

The pump may be arranged downstream of a junction of the first flow path with the second flow path. The pump may be arranged upstream of the plate heat exchanger.

To provide a system with greater flexibility, for example to store hot water for later use, the first flow path may be arranged to carry water to be heated from a vessel and return heated water to the vessel.

For yet greater flexibility, the first flow path may comprise a first return pipe for returning heated water to the vessel at a first height and a second return pipe for returning heated water the vessel at a second height. This may allow heated water to be provided to a lower portion of the vessel for gradual heating of the water in the vessel, or to a higher portion of the vessel for immediate use.

For ease of control of the system, the first return pipe may include the pump, and the second return pipe may include a further pump. The location to which water is returned may then be controlled by switching the pumps on and off appropriately.

To provide a simple system and for ease of manufacture, the heating system may comprise: a first three port junction arranged upstream of the pump and the plate heat exchanger to receive fluid from the first flow path at a first junction port and from the second flow path at a second junction port and to direct fluid to the pump and plate heat exchanger from a third junction port; and a second three port junction arranged downstream of the pump and the plate heat exchanger to receive fluid from the plate heat exchanger at a first junction port and to direct fluid onward to the first flow path from a second junction port and to the second flow path from a third junction port.

To prevent intermixing of descaling fluid and potable water, the heating system may further comprise a valve arrangement for isolating the second flow path from the first flow path. For simplicity, the valve arrangement may comprise manually actuatable valves.

For ease of control, the valve arrangement may comprise electronically actuatable valves.

T o provide a simple way to switch between use of first and second flow paths and for isolating potable water from the descaling fluid, the valve arrangement may comprise: a first three port valve arranged upstream of the pump and the plate heat exchanger; and a second three port valve arranged downstream of the pump and the plate heat exchanger.

For effective heating of potable water or descaling fluid for different use requirements, the pump may be a variable speed pump.

For more effective control of the heating system, the heating system may further comprise: one or more sensors for sensing one or more of: a temperature of the heating system, preferably a temperature of water in a water vessel; a flow rate of the heating system, preferably a flow rate of water through the plate heat exchanger; a heat flow of the heating system, preferably a heat flow from the first side of the plate heat exchanger to the second side of the plate heat exchanger; and a heat transfer rate of the heating system, preferably a heat transfer rate from the first side of the plate heat exchanger to the second side of the plate heat exchanger.

For improved control, the heating system may further comprise: a controller for controlling the heating system.

For fast and/or automated control, the controller may be configured to control the valve arrangement.

For effective control, the controller may be configured to determine a heat transfer rate of the heating system.

For improving overall heating system efficiency by determining when descaling is required, the controller may be configured to determine a scale condition of the heating system.

For improved usability, the controller may be configured to generate an alert related to a scale condition of the heating system.

For effective descaling performance, the controller may be configured to control the heating system according to a descaling programme.

To provide an effective descaling programme, the descaling programme may comprise one or more of: a descaling schedule (for example, when and how long a descaling process might run); a pump operating condition (for example, how fast a pump should run, or a desired fluid flow rate through the pump); a heat pump operating condition (for example, at what temperature and/or pressure to deliver a refrigerant to the plate heat exchanger to achieve a desired heating of descaling fluid); and a valve arrangement configuration (for example, a valve arrangement configuration or sequence of valve actuations to switch between water heating mode and a descaling mode, for example to achieve a valve arrangement configuration which opens the second flow path to permit descaling fluid to flow through the plate heat exchanger and optionally closes the first flow path to isolate the potable water from the descaling fluid, or vice versa).

To provide a more flexible and space-efficient system, the second flow path and/or the descaling fluid reservoir may be retrofittable and/or detachably attachable to the heating system.

The heating system may be as aforementioned. The heating system may include a modular (and/or integrated) heat pump water tank as aforementioned.

According to another aspect there is provided a method of descaling a heating system, the method comprising: forming a fluid circuit to connect a plate heat exchanger and a pump to a water source and a descaling fluid reservoir; controlling the fluid circuit to isolate the water source from the descaling fluid reservoir; and controlling the pump to pump descaling fluid from the descaling fluid reservoir through the plate heat exchanger.

For effective descaling of the heating system, the method may further comprise controlling a heat pump to heat the descaling fluid via the plate heat exchanger, preferably to between 50°C and 70°C.

For effective descaling of the heating system, the descaling fluid may be pumped through the plate heat exchanger for between 20 minutes and one hour.

According to an aspect described herein, a kit of parts may be provided comprising: a heating system comprising a plate heat exchanger and pump arranged in fluid communication with each other; a first three port valve arranged upstream of the plate heat exchanger and the pump; and a second three port valve arranged downstream of the plate heat exchanger and the pump, wherein each of the first three port valve and the second three port valve has a blanked port for receiving a retrofittable descaling system. Preferably, the descaling system comprising a descaling fluid reservoir and a conduit for connecting the descaling fluid reservoir to the blanked port of the first three port valve, optionally comprising a further conduit for connecting the descaling fluid reservoir to the blanked port of the second three port valve.

The kit of parts may be for a heating system as aforementioned. 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:

• a heat-pump

• a tank for containing heated water

• a heat exchanger, preferably a plate heat exchanger

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

• an alternate flow path through the heat exchanger

• one or more configurable three port valves (e.g. T valves) arranged to provide an alternate flow path through the plate heat exchanger

• a vessel of descaling fluid within the alternate flow path

• a descaling system comprising a vessel of descaling fluid and the alternate flow path

• a descaling system that is fitted during routine servicing of the heating system

• a descaling system that is integrated within the heating system

• a descaling system that is controlled electronically/automatically to descale the heat exchanger on a periodic basis

• a descaling system that is controlled electronically/automatically to descale the heat exchanger on the basis of an inferred scale build up

• a heating system wherein the presence of scale build up is inferred automatically through detection of a reduction in heat transfer rate through the heat exchanger

• a heating system wherein a heat flow sensor comprising inlet and outlet temperature sensors is used to infer the heat transfer rate through the heat exchanger

• a heating system wherein a heat transfer rate is inferred via one or more temperature sensors located within a hot water tank

• a heating system wherein a requirement to descale the potable water heating system is flagged to a technician

• a heating system wherein the detection of a need to descale the potable water heating system sets in course an automated sequence of valve actions, pump circulation and heat pump operations to effect a descaling process

The heating system may further be as aforementioned.

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

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.

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:

Figure 1 is a schematic of a heating system at a first time;

Figure 2 is a schematic of the heating system of Figure 1 at a second time;

Figure 3 is a schematic of the heating system of Figure 1 at a third time;

Figure 4 is a schematic of the heating system of Figure 1 at a fourth time;

Figure 5 is a schematic of a heating system including a check valve;

Figure 6 is a schematic of the heating system of Figure 5 at a first time;

Figure 7 is a schematic of the heating system of Figure 5 at a second time;

Figure 8 is a schematic of the heating system of Figure 5 at a third time;

Figure 9 is a schematic of another heating system including a check valve;

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

Figure 11 is a schematic of another heating system including a check valve;

Figure 12 is a schematic of another heating system;

Figure 13 is a schematic of modules of a heating system;

Figure 14 is a schematic of a prior art heating system;

Figure 15 is a schematic of a heating system including a descaling system according to a first example;

Figure 16 is a schematic of a heating system adapted to receive a descaling system according to a second example;

Figure 17 is a schematic of a variant heating system including a descaling system according to a third example; and Figure 18 is a schematic of a heating system including a descaling system according to a fourth example.

Figure 1 shows a heating system 50 with an integrated heat pump water tank (in the form of a cylinder). 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. Cold water is drawn from the bottom of the tank 2 by a pump 8 and passed through a plate heat exchanger 10 and onward to the top of the tank 2. The plate heat exchanger 10 receives heat from the heat pump 12 so as to heat the water drawn from the tank 2. Hot water is thus returned to the tank 2.

In an example, the heat source, in this case a heat pump 12, is 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).

In the illustrated example a thermocline 14 is formed between the hot and cold portions. Ideally the hot and cold portions in the tank have relatively uniform temperatures and are separated by a narrow thermocline. The thermocline 14 is schematically indicated with a line in the figures, but it will be appreciated that the thermocline may be more or less narrow, and the upper and lower regions may each have a more or less uniform temperature. An array of temperature sensors (not shown) can permit observation of the thermocline.

It has been observed that in use of the heating system 50 some unexpected heat losses can occur and cause a noticeable effect. It is an aim of the present invention to address the root causes and prevent certain behaviour in the heating system and to reduce heat losses.

In figure 1 the heating system 50 is shown at a first time. At this time heat is provided from the heat pump 12 to heat water in the tank 2. A quantity of hot water is available in an upper portion of the tank 2, and the remainder of the tank 2 is cold(er) water. The pump 8 pumps water out from the bottom of the tank 2 to the plate heat exchanger 10 and back to the top of the tank 2. At the plate heat exchanger 10 the water receives heat from the heat pump 12.

Figure 2 shows the heating system 50 at a second time after a quantity of water has been pumped to the heat exchanger 10, heated, and returned to the tank 2. The thermocline 14 has moved downward, and the tank 2 holds more hot water and less cold(er) water. At this time the system controller has determined that sufficient hot water is stored, and the pump 2 has been switched off and heat transfer at the plate heat exchanger 10 has been suspended. Residual water remains in the conduit leading from the bottom of the tank 2 to a plate heat exchanger 10 and back to the tank 2. In the segment between the plate heat exchanger 10 and the upper part of the tank 2 the water in the conduit is still hot, and in the segment between the plate heat exchanger 10 and the lower part of the tank 2 the water in the conduit is still cold. For illustration purposes cold water is indicated with shading in Figure 2.

Figure 3 shows the heating system 50 at a third time, after the pump 2 has been switched off for a time, with no user draw events having occurred. When the pump 2 is switched off, the water in the conduit flows so as to return to a hydrostatic equilibrium. The cold water is denser than the hot water in the conduit and extends to a level higher than the top of the tank 2. To reach a hydrostatic equilibrium the water in the conduit flows back, drawing hot water from the upper part of the tank 2 into the conduit and returning cold water from the conduit back to the bottom of the tank 2. This water flow in the conduit is indicated by arrows in Figure 3. If water in the tank were uniformly hot above the thermocline and uniformly cold below the thermocline, if no heat were gained or lost to the environment, and if flow resistances were negligible, then a hydrostatic equilibrium would be reached when the conduit is filled with hot (lighter) water above the level of the thermocline 14 in the tank 2, and cold (denser) water below that level. A significant part of the conduit may contain hot water in such an equilibrium arrangement.

The conduit is typically outside the tank 2, and outside the thermal insulation around the tank 2. Such conduits may have their own thermal insulation, but typically some heat losses to the environment occur at the conduit. While such heat losses may be relatively low, over time hot water stored in the conduit can cool down. As the water in the conduit cools down, it becomes denser. Heat loss from the water in the conduit to the environment is shown with arrows in Figure 3. Instead of reaching an equilibrium, heat losses at the conduit cause the water in the conduit to continue flowing from the upper part of the tank 2 to the bottom of the tank 2. The thermocline 14 in the tank 2 gradually moves upward (shown with an arrow in Figure 3) as backflow in the conduit gradually draws hot water from the top and returns cool water at the bottom.

Figure 4 shows the heating system 50 at a fourth time, after a period of equilibration. The thermocline 14 has moved upward, and the amount of hot water remaining available for use is reduced. Eventually a heating cycle as shown in Figure 1 must be started again in order to restore the quantity of stored hot water to the desired amount.

In the illustrated example the heat exchanger is arranged above the tank. This is particularly convenient as it can permit particularly compact integration of the heat exchanger with the heat pump, avoiding an increase of footprint in side-by-side arrangements or weightbearing elements if the (heavy) tank is above the heat pump. Consequently heating generally occurs above the level of a thermocline such that a column of colder water can be formed in the conduit above the level of the thermocline under the influence of the pump. It should however be appreciated that a similar backflow in the conduit is eventually observed in other configurations where the heat exchanger is arranged elsewhere, e.g. such that heating occurs at or below the level of a thermocline. Considering for instance an example where the heat exchanger happens to be arranged at the level of a thermocline: immediately after the pump is switched off the water in the conduit and tank is already in a hydrostatic equilibrium and no flow arises immediately. Gradually the heated water in the upper portion of the conduit cools down and becomes denser, causing a backflow in the conduit. Again, heat losses at the conduit cause the water in the conduit to continue flowing from the upper part of the tank 2 to the bottom of the tank 2 and the thermocline to move upward. Considering another example where the heat exchanger happens to be arranged near the bottom of the tank, and below the level of a thermocline: immediately after the pump is switched off the lower part of the conduit contains heated less dense water, causing a flow of denser cold water from the bottom of the tank into the conduit to reach a hydrostatic equilibrium. Gradually the heated water in the upper portion of the conduit cools off, becomes denser and sinks downward, causing a backflow in the conduit. The consequence is that hot water is continuously drawn into the conduit, cools, becomes denser and sinks downward, causing more hot water to be drawn in and the issue perpetuates itself. Again, heat losses at the conduit cause the water in the conduit to continue flowing from the upper part of the tank 2 to the bottom of the tank 2 and the thermocline to move upward. Regardless of where the heat exchanger is arranged a backflow in the conduit is eventually observed due to heat losses in the conduit.

The backflow of water described above is specific to a system where water is drawn from the tank and externally heated. In many conventional integrated heat pump water cylinders heat is provided to the water by other means, for example by a separate circuit of heating fluid (e.g. a heating coil immersed into the tank or arranged around the tank wall), so no such backflow issues can arise. The system where water is drawn from the tank and externally heated 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. External heating can also be more versatile and convenient as components can be accessed, maintained, and adjusted to a user’s requirements more easily.

The temperature distribution in the tank and the conduit, and hence the density distribution of the water, is often more complex than the discussed simplified example with 2 temperatures (‘hot’ and ‘cold’), but the same behaviour as described above is observed where heat loss occurs at the conduit. In some examples heat losses at the conduit may be negligible when the system is installed, but over time a thermal insulation may degrade and heat losses can increase.

Figure 5 shows a heating system 100 adapted so that backflow is prevented. A non-return valve 20 is included in the conduit between the pump 8 and the plate heat exchanger 10. Figures 6, 7 and 8 show the heating system 100 with a non-return valve 20 in use.

Figure 6 shows the heating system 100 at a first time, analogous to the heating system 50 shown in Figure 1. At this time heat is provided from the heat pump 12 to heat water in the tank 2. The pump 8 pumps water out from the bottom of the tank 2 to a plate heat exchanger 10 and back to the tank 2. At the plate heat exchanger 10 the water receives heat from the heat pump 12.

Figure 7 shows the heating system 100 at a second time after a quantity of water has been pumped to the heat exchanger 10 and returned heated to the tank 2, analogous to the heating system 50 shown in Figure 2. The thermocline 14 has moved downward, and the tank 2 holds more hot water and less cold water. At this time the system controller has determined that sufficient hot water is stored, and the heat pump 12 and the pump 2 have been switched off.

Figure 8 shows the heating system 100 at a third time, after the pump 2 has been switched off for a time, with no user draw events having occurred. When the pump 2 is switched off, the water in the conduit is prevented from flowing back by the non-return valve 20. Backflow in the conduit is prevented. At a fourth time after a period of equilibration the thermocline 14 remains at the same level, with usual conductive heat transfer dominating changes in thermocline rather than backflow in the conduits. The amount of hot water remaining available for use is substantially same. A longer period can pass before a new heating cycle as shown in Figure 6 needs to be started again in order to restore the quantity of stored hot water to the desired amount.

An example of a suitable non-return valve 20 is a swing valve. Swing valves are favourable as they are quite cheap and reliable. A wide variety of other non-return valves (also referred to as check valves) can be used, including lift valves, plate valves, ball valves, duckbill valves, and many others. The non-return valve 20 may be an electronically controllable valve, e.g. that is actuated to close the flow path by a controller at the same time as the pump is switched off. For the non-return valve 20 a low displacement pressure is preferred, so that inclusion of the non-return valve 20 does not significantly reduce flow or affect pumping performance.

In the illustrated example the non-return valve 20 is arranged between the pump 8 and the plate heat exchanger 10. In other examples the non-return valve can be arranged between the plate heat exchanger 10 and the top of the tank 2, or between the bottom of the tank 2 and the pump 8. The non-return valve 20 can be arranged at the outlet of the conduit into the top of the tank 2, or at the inlet of the conduit at the bottom of the tank 2.

The non-return valve 20 is arranged to prevent water flow from the upper portion of the tank to the lower portion of the tank via the conduit. Such a non-return valve provides different functionality than for instance a non-return valve to prevent water flow from the lower portion of the tank into the conduit, that is, preventing flow in the opposite flow direction. A non-return valve arranged to prevent flow into the conduit from the bottom of the tank can be used for other purposes. It cannot however prevent the issue with gradual thermal losses described above.

In the examples described above the water is returned to the top of the tank 2 which is generally suitable for providing hot water to be drawn off for use immediately or in the near future. It will be understood that hot water may equally be provided to other regions of the tank for a nuanced heating strategy, for instance to the bottom of the tank or to a central region of the tank for gradual heating of all of the water in the tank.

Figure 9 shows another heating system 110 adapted so that backflow is prevented. A nonreturn valve 20 is provided analogous to the heating system 100 illustrated in Figure 5. Instead of a simple conduit to return hot water from the plate heat exchanger 10 to the top of the tank 2, the conduit from the plate heat exchanger 10 includes a three port valve 30 that can direct the flow either to a first conduit branch to the top of the tank 2, or to a second conduit branch to a central 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 hot water can be heated rapidly to a high temperature at the top of the tank, and separately more gradual heating of the bulk of the water can be achieved via the second conduit to the central region of the tank 2. Alternative valve arrangements can be used in place of a three port valve for selection of either the first or second branch of the conduit. In the illustrated example the second branch provides a flow path to a central region of the tank 2, but in other examples the second branch can provide a flow path to a bottom region of the tank 2 instead. Figure 11 illustrates an example where the second branch provides a flow path to a bottom region of the tank 2.

In the examples described above the pump 8 is provided between the plate heat exchanger and the bottom of the tank. Conceivably the pump 8 may be arranged between the plate heat exchanger and the top of the tank, though this is less preferred as operating the pump at the higher temperature downstream of the heat exchanger can be less favourable.

To avoid heat losses further, the heating system 100, 110 may be adapted to stagger the switching off of the heat pump 12 and the pump 8. If the heat pump 12 and the pump 8 are switched off at the same time, then the section of the conduit between the plate heat exchanger 10 and the top of the tank 2 contains hot water. This section may not be well thermally insulated, and by the time the next heating cycle starts this hot water may have lost a substantial amount of heat to the environment. Returning this portion of hot water to the tank rather than leaving it in the conduit can enable thermal efficiency. The duration the pump is required to operate following stop of the heat pump depends on factors such as volume of water in the conduit between the plate heat exchanger 10 and the top of the tank 2 and pump rate, as well as whether any residual heating occurs at the plate heat exchanger 10 after the heat pump 12 is stopped, which might cause a portion of cold water from downstream of the plate heat exchanger 10 to be acceptably heated too. A temperature sensor can be included at the outlet of the conduit, and once the sensor senses a temperature dropping beneath a threshold the pump 8 can be caused to stop. A suitable threshold depends on the desired storage temperature of the hot water, which may be user selectable. A fixed amount of time can be set for the pump 8 to continue pumping after the heat pump 12 has been stopped. Given the system is provided as an integrated system and retrofit is not the primary intended use, setting a fixed amount of time can be quite effective. In an example where the pump rate is in the region of 0.3 litres/minute and the conduit volume downstream of the heat exchanger is 0.075 litres, the controller controls the pump 8 to switch off 15 seconds after the heat pump 12 is switched off. In other examples a longer or shorter period may be suitable, for example: in the range of 10-20 seconds; or 3 seconds or more; or 5 seconds or more.

While not specifically shown in figures 1-9, the heating system 100, 110 generally includes a controller for controlling the heating system. Sensors are also generally provided in the heating system for monitoring properties of the system. Temperature sensors may be provided, e.g. on the tank 2 to sense one or more temperatures of the tank 2. Temperature sensors may be provided at different locations on the tank 2, preferably at different heights, to sense a distribution of temperatures at the tank 2. The temperature sensor data 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. Figure 10 shows the heating system 100 with a controller 40 as well as an array of temperature sensors 42, with dashed lines indicating communication between the controller and other components of the heating system.

The controller 40 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 40 may control the pump 8, including switching on or off as well as in the case of a variable speed pump controlling the pump rate. The controller 40 may control three port valves 30 to select between different flow paths e.g. in order to provide a fast heating mode or an energy efficient heating mode.

Integration

Figure 12 shows another heating system 60 with an integrated heat pump water tank, similar to the heating system 50 shown in Figures 1-4. Cold water is drawn from the bottom of the tank 2 by a pump 8 and passed through a plate heat exchanger 10. The plate heat exchanger 10 receives heat from the heat pump 12 so as to heat the water drawn from the tank 2. Hot water is thus returned to the tank 2. The heated water is not returned to the top of the tank 2, but instead to the bottom of the tank. Returning water to the bottom of the tank can enable particularly efficient but gradual heating of the water, whereas returning water to the top of the tank can enable more rapid but less efficient heating of the water. As the heated water is returned to the bottom of the tank, near the level where water is drawn off by the pump, no pressure difference between the inlet of the conduit and the outlet of the conduit develops as the water is heated, and no backflow is caused. Therefore no non-return valve is included in the illustrated heating system 60 (though a non-return valve may be included for other purposes).

In the examples illustrated in Figures 11 and 12 a baffle 16 is included 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 examples the baffle 16 is arranged at around one third or half the tank height, 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 at tank in- and outlets can cause 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, but inclusion of a baffle is optional. 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.

In some examples the integrated heat pump water tank includes two modular units: a tank unit including the tank 2 and a heat pump unit 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).

Figure 13 shows a tank unit 62 and a heat pump unit 72 that can together form a modular integrated heat pump water tank. The tank unit 62 includes the tank 2 and the heat pump unit 72 includes the heat pump 12. The heat pump unit 72 further includes the plate heat exchanger 10 as well as ports e.g. for connection of the conduits for fluids to and from the heat pump unit 72. The ports for conduits to the plate heat exchanger 10 are illustrated, but it will be appreciated that the heat pump unit 72 also includes other in- and outlets for fluids (notably to and from the heat pump 12) as well as suitable electrical connectors for receiving power and data connectors for receiving and sending data. Similarly the tank unit 62 includes suitable ports e.g. for connection of the conduits for fluids to and from the heat pump unit 72.

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 62 including the tank 2 and a heat pump unit 72 including the heat pump 12 can overcome these issues.

The illustrated modular heat pump water tank includes a number of features to facilitate joining and detaching of the heat pump unit 72 to and from the tank unit 62. A mounting guide 64 can ensure that the heat pump unit 72 is mounted on the tank unit 62 with the correct positioning and orientation. This can prevent applying unintended loads on the tank unit 62, which could damage the tank unit 62. In the illustrated example a mounting guide 64 is provided at the tank unit 62, but it may alternatively be provided at the heat pump unit 72, or a set of mating mounting guides may be provided at both the tank unit and the heat pump unit, as will be readily apparent.

An attachment means 66 can ensure that the heat pump unit 72 is fixedly attached to the tank unit 62. This can prevent the units from shifting e.g. under vibrations during operation. A wide variety of attachment means 66 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 66 is releasable so that the units can be dismounted from one another. In an example the heat pump unit 72 and/or the tank unit 62 includes a frame structure to which components are mounted. The frame structure can conveniently be used for attachment of the modules to one another. In the illustrated example an attachment means 66 is provided at the tank unit 62, but it may alternatively be provided at the heat pump unit 72, or a set of cooperating attachment means may be provided at both the tank unit and the heat pump unit.

A module sensor 68 can sense whether or not a heat pump unit 72 is attached to the tank unit 62. This can enable a controller to verify presence or absence of a heat pump unit 72 at a tank unit 62. A wide variety of sensor types can be used for the module sensor 68, 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.

In use a heat pump unit 72 can be mounted and attached to a tank unit 62, and then suitable connections can be provided. In the illustrated example fluid handling components 70 are provided including conduits in order to connect the tank 2 to the heat exchanger 10 and a pump 8 to form an operational integrated heat pump water tank as illustrated in Figure 12. The modular integrated heat pump water tank can also be adapted to provide the integrated heat pump water tank as illustrated in any of Figures 1 to 11 with suitable ports and connections.

In a variant the heat exchanger 10 is provided elsewhere than in the heat pump unit 72, for instance together with other fluid pumping components 70 not included in the heat pump unit 72 or the tank unit 62.

In a variant the pump 8 is provided in the heat pump unit 72.

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.

In the illustration the ports of the tank 2 for connecting the tank 2 to the heat exchanger 10 are shown as capped, and the tank 2 can operate in the absence of a heat pump unit 72 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 62 can thus heat, store and provide hot water in the absence of a heat pump unit 72. By virtue of the modularity a heat pump unit 72 can be installed at a later date with ease and at lower cost as the tank unit 62 need not be replaced. By virtue of the integration of the heat pump unit 72 and the tank unit 62 into a common assembly a particularly compact heating system can be provided. Further, by virtue of the modularity if an installed heat pump unit 72 becomes damaged or suffers performance problems then the heat pump unit 72 can be removed and replaced with a new heat pump unit 72 with ease and at lower cost as the tank unit 62 need not be replaced. If the replacement is not immediate then the tank unit 62 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.

Descaling

Figure 14 shows a heating system 1100 with a tank 2 having a cold water inlet 4 and a hot water outlet 6 for drawing off hot water. A pump 8 pumps water along a first flow path out from the bottom of the tank 2 to a plate heat exchanger 10 and back to the tank 2. The plate heat exchanger 10 receives heated heat transfer fluid (e.g. refrigerant) at a first side of the plate heat exchanger 10 from a heat pump 12 so as to heat the water drawn from the tank 2 which is provided to the second side of the plate heat exchanger 10. Hot water is thus returned to the tank 2. In the illustrated embodiment the water is returned to the top of the tank 2 which is generally suitable for providing hot water to be drawn off for use immediately or in the near future. It will be understood that hot water may equally be provided to other regions of the tank, for instance the bottom of the tank for gradual heating of all of the water in the tank.

The pump 8 is arranged downstream of the heat exchanger on the first flow path. In an alternative the pump 8 may be arranged upstream of the plate heat exchanger 10.

In an example, the heat source, in this case a heat pump 12, is 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).

Figure 15 shows a heating system 200 adapted so that the pump 8 may also pump descaling fluid along a second flow path to the plate heat exchanger 10 in order to descale the plate heat exchanger 10, in addition to pumping water to be heated through the plate heat exchanger 10 along the first flow path.

As before, the tank 2 has a cold water inlet 4 for mains water and a hot water outlet 6 for drawing off hot water. Along the first flow path, the pump 8, preferably a variable speed pump, pumps water from the tank 2 (typically from the bottom of the tank 2) to the second side of the plate heat exchanger 10 from where heated water is returned to the tank 2. The heat pump 12 provides heated heat transfer fluid (e.g. refrigerant) to a first side of the plate heat exchanger 10.

A descaling system is included for providing descaling fluid from a descaling fluid reservoir 114 or descaling fluid source or inlet to the plate heat exchanger 10. The descaling system provides a second flow path to take descaling fluid from the descaling fluid reservoir 114 to the plate exchanger and then away from the plate heat exchanger 10. The second flow path comprises the pump 8 and the plate heat exchanger 10 so that the descaling fluid can be pumped from the descaling fluid reservoir 114 through the plate heat exchanger 10 in order to descale it. The first flow path and the second flow path therefore coincide at least at the pump 8 and plate heat exchanger 10 so that the same pump 8 is used both for descaling and for water heating. Upstream and downstream of the pump and plate heat exchangers there are three port junctions to divert fluid to from the separate downstream parts of first and second flow paths to the pump 8 and plate heat exchanger 10 and then to divert flow of fluid back to the diverging upstream parts of the first and second flow paths.

In the illustrated embodiment the second flow path is a loop returning to the descaling fluid reservoir 114 once it has passed through the plate heat exchanger 10. This allows the descaling fluid to be circulated in the loop during descaling. This can allow the descaling fluid to be completely used up during a descaling process, i.e. by being circulated until the amount of the descaling agent (e.g. the acid) in the fluid has dropped to zero, or below a threshold level. It will be appreciated that the second flow path need not be a loop. For example, the descaling fluid reservoir 114 may be provided downstream of the pump 8 at the start of the second flow path, and the second flow path may end in an outlet at which descaling fluid which has passed through the plate heat exchanger 10 may be removed or drained from the system, rather than re- circulated.

The descaling fluid comprises a descaling agent which may be diluted by water. The descaling agent is generally acidic and may include any of (or a combination of) hydrochloric acid, acetic acid, citric acid, glycolic acid, formic acid, lactic acid, phosphoric acid, sulfamic acid or any other descaling agent in an appropriate concentration.

The descaling fluid reservoir 114 may be removable and replaceable so as to facilitate draining and/or replenishing of the descaling fluid once spent. The descaling fluid reservoir 114 alternatively may be a fixed part of the descaling system. The descaling fluid reservoir 114 may contain an inlet for replenishing the descaling fluid and an outlet for draining spent descaling fluid from the descaling fluid reservoir 114.

The heating system 200 is able to use either the first flow path to pump 8 water from the tank 2 to the plate heat exchanger 10 to heat potable water in the tank 2 (also referred to herein as a heating mode), or the second flow path to pump 8 descaling fluid from the descaling fluid reservoir 114 for descaling the plate heat exchanger 10 (also referred to herein as a descaling mode). The heating system 200 is able to switch between these different configurations and modes of operation. In a first configuration of heating system 200, the first flow path is available for the pump 8 to pump 8 water from the tank 2 to the plate heat exchanger 10 and return it to the tank 2; and the second flow path which includes the descaling fluid reservoir 114 is shut off. In this configuration, the descaling fluid reservoir 114 and the tank 2 are thus isolated from one another to prevent mixing of the descaling fluid and the potable water. In the context of the present disclosure, the first flow path is termed “open” in this configuration and the second flow path is termed “closed”.

In a second configuration of the heating system 200, the first flow path is shut off and the second flow path is available for the pump 8 to pump descaling fluid from the descaling fluid reservoir 114 to the plate heat exchanger 10 and away from the plate heat exchanger 10. Again in this configuration, the descaling fluid reservoir 114 and the tank 2 are isolated from one another thereby to prevent mixing of the descaling fluid and the potable water. In this configuration, the first flow path is “closed” and the second flow path is “open”.

The heating system 200 includes a valve arrangement configured to permit switching between the first configuration and the second configuration. In the illustrated embodiment, the valve arrangement includes a first three port valve 116 (also referred to as a “T-valve”) arranged upstream of the pump 8 and heat exchanger between the tank 2 and the pump 8; and a second three port valve 18 is arranged downstream of the plate heat exchanger 10 and the pump 8 between the plate heat exchanger 10 and the tank 2. The heating system 200 may switch between use of the first and second flow paths by actuation of the first and second three port valves 116, 18. It will be appreciated that other valve arrangements could achieve a similar effect, for example, an arrangement of (two port) isolation valves may be used to prevent flow of water into and out of the first and second flow paths in order to isolate them from one another.

In an exemplary alternative, the first three way valve 116 and the second three way valve 18 may be replaced by simple three port junctions or connectors to provide both the first flow path and second flow path but without the ability at the junction to isolate the paths from one another. A valve arrangement of isolation valves might then optionally be provided in the first and second paths to provide isolation of the two flow paths from one another.

The valves of the valve arrangement may be electronically or manually actuated. In one example, a user (for example, a technician) may manually actuate the valves in order to switch the heating system 200 from a heating mode to a descaling mode during maintenance. In another example, electronic valves may be actuated automatically by a controller of the heating system 200 (as described in more detail below) to switch between a heating mode and a descaling mode. In some examples a further ‘flushing’ mode of operation may be included, for use after a descaling mode and before a heating mode. In an example in the flushing mode the pump 8 pumps water from the tank 2 to the plate heat exchanger 10 but instead of returning it to the tank 2 it is diverted to the descaling fluid reservoir 114, or to a drain outlet (which may be controlled with a valve) e.g. suitably provided in the second flow path. Brief operation in such a flushing mode can prevent residual descaling fluid from reaching the tank.

Figure 16 shows a heating system 300 adapted to receive a retrofit or temporary descaling system. A first three port valve 116 is provided in the first flow path upstream of the plate heat exchanger 10 and the pump 8, and a second three port valve 18 is provided in the first flow path downstream of the plate heat exchanger 10 and the pump 8. The valves 116, 18 are configured so that the first flow path is open and the alternative ports from the valves are blanked at installation of the heating system 300. Other than the addition of the three port valves each having a blanked port, the heating system 300 of Figure 16 is similar to the heating system 1100 of Figure 14.

The descaling system may be provided separately and later attached to the system at the blanked ports of the three port valves with those ports unblanked to provide the second flow path. This descaling system may be fitted by a technician during maintenance or routine servicing of the heating system 300. Once the descaling system is fitted, the heating system 300 may then function in the same manner as described in relation to Figure 15.

Figure 17 shows a variant heating system 400 which uses two pumps 21 , 22 which may be used to draw potable water from the tank 2 and return it to the tank 2 at two different positions. As before, the plate heat exchanger 10 receives water from the bottom of the tank 2 to be heated. The heated water is returned to either a lower region of the tank 2 for efficiently heating the tank gradually; or to an upper region of the tank 2 for rapid delivery of a limited volume of hot water for immediate demand. Depending on which pump 21 , 22 is used to pump the water, the heated water is returned via a different return pipe to the tank 2 at a different height.

Upstream of the plate heat exchanger 10 a heated water return pipe divides into an upper return pipe 25 and a lower return pipe 27 at a three-way junction 29. The upper return pipe 25 returns heated water to an upper region of the tank 2 (for example at the top of the tank 2), and the lower return pipe 27 returns heated water to a lower region of the tank 2 (for example towards the bottom of the tank 2).

In the upper return pipe 25 an upper return pump 21 is arranged to pump water from the bottom of the tank 2, through the plate heat exchanger 10 and through the upper return pipe 25 to return heated water to the upper region of the tank 2. Upstream of the upper return pump 21 an optional check valve 24 is included arranged to assist in preventing flow of water from the upper region of the tank 2 back through the upper return pipe 25 towards the upper return pump. In the illustrated embodiment, the path taking water from the tank 2 and returning through the upper return pipe 25 corresponds to the first flow path described in relation to Figures 14-16. The upper return pipe 25 includes the second three port valve 18 connecting to the descaling loop.

In a descaling mode, the upper return pump 21 pumps descaling fluid from the descaling fluid reservoir 114 along a second flow path as previously described in relation to Figures 15 and 16.

In the lower return pipe 27 a lower return pump 22 is arranged to pump water from the bottom of the tank 2, through the plate heat exchanger 10 and through the lower return pipe 27 to return heated water to the lower region of the tank 2. Upstream of the lower return pump 22 an optional check valve 26 is included arranged to assist in preventing flow of water from the lower region of the tank 2 back through the lower return pipe 27 towards the lower return pump 22. In a descaling mode, the lower return pump 22 is switched off to prevent descaling fluid being drawn into the tank 2. A further stop valve (not shown) may also be provided in the lower return pipe 27 to further isolate the tank 2 from the second flow path in the descaling mode.

The skilled person will appreciate that alternative arrangements of upper and lower return pumps 21 , 22 and upper and lower return pipes 25, 27 are possible in combination with the descaling system. In an alternative, the lower return pump 22 may be responsible for circulating the descaling fluid, with the three port valve 18 connecting to the descaling system being provided in the lower return pipe 27 (as opposed the upper return pipe 25 in the illustrated embodiment). In a further alternative both the upper and lower return pipes 25, 27 may comprise a connection to the descaling system so that either or both pumps 21 , 22 could be used to pump descaling fluid through the plate heat exchanger 10 in a descaling mode.

In a further alternative arrangement return of heated water to the tank 2 at different heights using only one pump 8 is enabled. In an example, the heating system 200 of Figure 15 may be modified with a further three port valve provided downstream of the plate heat exchanger 10 to permit heated water onward either to return to the bottom of the tank 2 or to an upper portion of the tank 2 via upper and lower heated water return pipes. It will be appreciated that this further three port valve might be provided upstream or downstream of the second three port valve 18.

Figure 18 shows a heating system 500 as described in relation to Figures 15 and 16 including a controller 28 for controlling the heating system 500. Sensors 42 32 are also provided in the heating system 500 for monitoring properties of the system. It will be appreciated that a controller 28 is equally suitable for use with the heating system 400 of Figure 17 or any other heating system as described herein.

Temperature sensors such as the array of temperature sensors 42 illustrated in Figure 18 may be provided on the tank 2 to sense one or more temperatures of the tank 2. The temperature sensor data may be transmitted to the controller 28. The controller 28 may be configured to determine a temperature profile of the tank 2 from the temperature sensor data. The controller 28 may thus determine whether there is sufficient hot water in the tank 2 to satisfy a user hot water demand.

A heat flow sensor 32 is provided to detect a heat flow or heat transfer rate through the plate heat exchanger 10. The heat flow data may be transmitted to the controller 28. The heat flow sensor may comprise flow sensors for sensing a flow rate of water through the second side of the plate heat exchanger 10 and temperature sensors for sensing temperature of water before and after the plate heat exchanger 10 to determine a heat flow.

In some embodiments, the controller 28 is configured to determine a scale condition of the plate heat exchanger 10 in dependence on sensor data. In an example, the presence of scale build-up in the plate heat exchanger 10 may be inferred from a drop in the heat transfer rate detected by heat flow sensor 32. The heat transfer rate may also be determined by the controller 28 from temperature data from the tank 2 alone or in combination with data from other sensors in the heating system 500, and/or in combination with further data such as the operating conditions of the heating system 500, for example, pump speeds, heat pump operating conditions, ambient temperatures etc.

The controller 28 is configured to control the heat pump 12. The heat pump 12 may be controlled by the controller 28 in dependence on a user heating demand and/or sensor data from the sensors of the heating system 500 to provide appropriate heating to water from the tank 2 when the heating system 500 is in a heating mode. The controller 28 may also control the heat pump 12 to provide heat to the descaling fluid when the heating system 500 is in a descaling mode. The heat to be provided by the heat pump 12 to the descaling fluid during descaling may depend on the scale condition, for example, if a large amount of scale is determined to be present an increase in descaling fluid temperature may be advantageous to accelerate the descaling process.

The controller 28 may also control the three port valves 116, 18 to select between the first and second flow paths in order to place the system in heating mode or descaling mode. The controller 28 may automatically switch the heating system 500 between a heating mode and a descaling mode in dependence on a scale condition of the plate heat exchanger 10 or a descaling schedule, for example, a programmed time period in which descaling is to occur. In general, the controller 28 may control the valve arrangement of the heating system 500 in order to switch between the heating mode and the descaling mode. The controller 28 may also provide for a user to select whether to enter a descaling mode, for example by input via a user interface. The controller 28 may also be programmed by a user to enter a descaling mode according to a particular schedule or set of criteria such as a scale condition or change in heat transfer rate.

Alternatively, or additionally, the controller 28 can be configured to provide an indication or an alert to a user as to when descaling of the plate heat exchanger 10 is required or recommended. The indication or alert may be generated when a reduction in heat transfer rate from a reference heat transfer rate has reached a threshold value, or when a scale condition has been determined or detected. Alternatively, the indication or alert may be provided after a programmed time period since installation of the system or since the most recent service of the system. The user may then manually actuate the valves in the valve arrangement to switch between flow paths as appropriate in response to the indication or alert or operate the controller to electronically actuate the valves.

The controller 28 is configured to control the one or more pumps arranged in the heating system 500 for pumping water to and from the tank 2 and through the plate heat exchanger 10. It may switch the pump(s) on and off and/or adjust the speed of one or more variable speed pumps. The speed of the pump 8 may be adjusted in response to a hot water demand when the heating system 500 is in a heating mode. For example, in order to permit water being returned to the top of the tank 2 to receive sufficient heat to be immediately useful the pump 8 may pump the water at a relatively slow rate, e.g. 1-2 l/min. In embodiments in which water is being returned to the bottom of the tank 2, the water may be pumped at a higher rate, e.g. 15-20 l/min to heat the water in the tank 2 with high efficiency. The speed of the pump(s) may also be adjusted when the heating system 500 is in a descaling mode. The controller 28 may be configured to vary the speed of the pump 8 when pumping descaling fluid to the plate heat exchanger 10 in dependence on a descaling programme and/or a scale condition of the plate heat exchanger 10. For example, it may be advantageous to pump 8 descaling fluid through the plate heat exchanger 10 more slowly if there is a large build-up of scale.

When in a heating mode, the controller 28 controls the heat pump 12, the pump(s) and valve arrangements to open the first flow path and close the second flow path to provide a flow of water from the tank 2 through the plate heat exchanger 10 and to return hot water to the tank 2, thereby to heat water in the tank 2 according to a user heating demand or schedule while isolating the descaling fluid reservoir 114 from the tank 2. When the hot water system needs descaling, as determined by the controller 28 or by a user or technician, the valves in the valve arrangement are actuated (either by the controller 28 or manually by a user) to open the second flow path and close the first flow path, and flow is instead able to come from a descaling fluid reservoir 114 so that descaling fluid is pumped by the pump 8 through the plate heat exchanger 10. It is preferable that the pump(s) 8 are stopped while the valve arrangement moves between configurations to prevent mixing of potable water and descaling fluid.

During the descaling process, the heat pump 12 may be turned on to heat the descaling fluid as it passes through the plate heat exchanger 10. Heating the descaling fluid may help speed up descaling of the plate heat exchanger 10. For example, heating the descaling fluid may speed up the following chemical reactions of the descaling process:

CaCO ₃ (s) + 2H ⁺ (aq) Ca ²⁺ (aq) + CO ₂ (g) + H ₂ O(I)

MgCO ₃ (s) + 2H ⁺ (aq) Mg ²⁺ (aq) + CO ₂ (g) + H ₂ O(I)

The heat pump 12 may be controlled so that the descaling fluid attains a temperature of around 50 °C to 70 °C during a descaling process. Descaling fluid may be circulated through the system over a period of e.g. 20 minutes to one hour in order to achieve adequate descaling depending on the scale condition of the plate heat exchanger 10. Once the descaling process has completed, the pump 8 is stopped and the valves 116, 18 in the valve arrangement are actuated (either by the controller 28 or manually by a user) to close the second flow path and re-open the first flow path. When the pump 8 is then restarted, this will allow water to flow back through the first flow path with the descaling fluid reservoir 114 isolated from the tank 2.

If a flushing operation is included, e.g. after a descaling mode and before a heating mode, the controller 28 controls the heat pump 12, the pump(s) and valve arrangements to provide a flow of water from the tank 2 through the plate heat exchanger 10 and to the descaling fluid reservoir 114 or to a suitably included drain outlet, so as to prevent residual descaling fluid from reaching the tank.

The descaling fluid can be drained from the descaling fluid reservoir 114 or can be allowed to remain until the next descaling cycle is required depending on whether the used descaling fluid is still useful for further descaling. This may depend, for example, on the concentration of acid used in the descaling fluid, the volume of fluid, the length of time of the descaling process, the scale condition of the plate heat exchanger 10 and/or degree of contamination of scale or any other suitable criteria.

In some embodiments, the controller 28 is configured to determine a condition of the descaling fluid in dependence on sensor data. In an example, the efficacy of the descaling fluid may be inferred from an increase in the heat transfer rate at the plate heat exchanger 10 over the course of a descaling cycle. The heat transfer rate may be detected by the heat flow sensor 32 or elsewise as discussed above. The controller 28 can be configured to provide an indication or an alert to a user as to when descaling fluid should be replenished or replaced. The indication or alert may be generated when a descaling cycle fails to suitably affect a heat transfer rate, e.g. restore a reduced heat transfer rate to sufficient proximity to a reference heat transfer rate.

It will be appreciated that various aspects described above can be suitably combined. For example, a modular (and/or integrated) heat pump water tank may include descaling features, and a heating system with a non-return valve may include descaling features.

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.

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.

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.

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.

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).

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.

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.

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