Water Heating System

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.

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.

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.

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.