GB2591127A

GB2591127A - Hot water apparatus and system

Info

Publication number: GB2591127A
Application number: GB2000711.8A
Authority: GB
Inventors: Mackle Gerard; Henderson Ian; Dolan Niall
Original assignee: WARMFLOW ENGINEERING Co Ltd
Current assignee: WARMFLOW ENGINEERING Co Ltd
Priority date: 2020-01-17
Filing date: 2020-01-17
Publication date: 2021-07-21
Anticipated expiration: 2040-01-17
Also published as: GB202000711D0; GB2591127B

Abstract

A hot water system suitable for use with a primary heat source 100 (e.g. heat pump), the system comprising a heat exchanger 1501 and an auxiliary heater 1502, wherein the auxiliary heater is configured to receive system water from a primary heat source and is in fluid communication with the heat exchanger. The heat exchanger is configured to receive cold domestic water which is heated by the system water received from the auxiliary heater to provide warm water via an outlet of the heat exchanger. The system may further comprise a header 130, a flow diverting valve 132 and a thermal store 140, the auxiliary heater being located externally of the thermal store. The outlet of the heat exchanger may be in fluid communication with a return diverting valve 160 and a circulator 190 to selectively return water to the header or the thermal store. The auxiliary heater is automatically selective when the water returning from the heat exchanger is insufficient to defrost the energy source. The heat exchanger may be a plate heat exchanger and the system may comprise an expansion vessel 220, a flow sensor 1511 and a temperature sensor.

Description

HOT WATER APPARATUS AND SYSTEM

The present application relates to a water heating system, and more particularly to a hot water supply apparatus for use in such a system.

Summary of the Invention

In accordance with an aspect the invention there is provided a hot water system suitable for use with a primary heat energy source, the system comprising a heat exchanger and an auxiliary heater, wherein the auxiliary heater is configured to receive system water from a primary heat energy source and is in fluid communication with the heat exchanger; wherein the heat exchanger is configured to receive cold domestic water from a cold domestic water inlet, whereby said cold water is conductively warmable by the system water received from the auxiliary heater to provide warm water via an outlet of the heat exchanger.

It will be understood that the term 'domestic' used herein not limit the use of the system and apparatus of the invention with dwelling houses, but rather should be understood to comprise any construction having a requirement for the supply of hot water supply and/or space heating.

Optionally, the system further includes a header.

Optionally, the system further includes a flow diverting valve.

Optionally, the system further includes a thermal store.

Optionally, the auxiliary heater is located externally of the thermal store.

Optionally, the auxiliary heater is located spaced apart from the thermal store.

Optionally, the auxiliary heater is configured for direct fluid communication with a primary heat energy source.

Optionally, the auxiliary heater is configured for indirect fluid communication with a primary heat energy source via one or more of the header, the flow diverting valve, or the thermal store.

Optionally, the system is configured for selective direct fluid communication between the auxiliary heater and a primary heat energy source, or indirect fluid communication between a primary heat energy source via one or more of the header, the flow diverting valve, the thermal store.

Optionally, the system comprises a controller to control the operation of the system and apparatus following inputs selectively set by a user, for example through a control interface, and/or optionally automatically following inputs from suitable sensors located where appropriate around the system, for example, but not limited to flow rate sensors, temperature sensors, valve position sensors, etc. Optionally, the auxiliary heater is operational to heat system water obtained directly or indirectly from a primary heat energy source in advance of entry into the heat exchanger.

Optionally, the auxiliary heater is operationally intermediate and in fluid communication with the primary heat energy source and the heat exchanger.

Optionally, the auxiliary heater is operationally intermediate and in fluid communication with the header and the heat exchanger.

Optionally, the auxiliary heater is operationally intermediate and in fluid communication with the flow diverting valve and the heat exchanger.

Optionally, the auxiliary heater is operationally intermediate and in fluid communication with the thermal store and the heat exchanger.

Optionally, the thermal store is configured to receive system water from the primary heat energy source via the header, and optionally via the flow diverting valve.

Optionally, the auxiliary heater is operational to heat the system water from the thermal store in advance of entry into the heat exchanger.

Optionally, operation of the auxiliary heater is automatically selective in the event that the system water from the thermal store has insufficient energy to heat the cold domestic water received by the heat exchanger.

Optionally, the heat exchanger includes an outlet that is in fluid communication with one or more diverting valves and a circulator, so that system water from the heat exchanger is selectively returnable to the header or to the thermal store.

Optionally, operation of the auxiliary heater is automatically selective in so that the event that system water returning from the heat exchanger is insufficient to defrost the energy source, the auxiliary heater additionally heats said system water prior to entry into the heat exchanger to a temperature sufficient to perform defrosting of the energy source.

Optionally, the heat exchanger is a plate heat exchanger.

Optionally, the auxiliary heater is an electric heater.

Optionally, the system further comprises one or more expansion vessels.

Optionally, the system comprises one or more flow sensors and/or temperature sensors.

Optionally, the system comprises a recirculating pump in fluid communication with outlet of the heat exchanger and the cold domestic water inlet.

Optionally, the system comprises one or more pressure reducing valves.

Optionally, the header is configured for fluid connection to a central heating system wherein system water from the header is provided as a direct central heating (CH) heat source.

Optionally, fluid connection of the header to a central heating system comprises one or more manifolds, valves, mixing valves or a mixture thereof Optionally, the central heating system comprises one or more central heating zones and/or underfloor heating systems.

In accordance with a second aspect of the invention, there is provided a hot water supply apparatus according to the system of the first aspect of the invention.

In accordance with an aspect of the invention the hot water system system is provided as a consumer apparatus.

In accordance with a further aspect of the invention there is provided domestic hot water system comprising a hot water supply apparatus suitable for use with a primary heat energy source, the apparatus comprising a controller, a header, a thermal store, a heat exchanger and an auxiliary heater, wherein the header is configured to receive system water from a primary heat energy source; wherein the header is fluid communication with the thermal store; wherein the thermal store is in fluid communication with the heat exchanger, wherein the heat exchanger configured to receive cold domestic water from a cold domestic water inlet whereby said cold water is conductively warmable by system water received from the thermal store to provide warm water for a user via an outlet of the heat exchanger, and wherein the auxiliary heater is provided intermediate and in fluid communication with the thermal store and the heat exchanger.

Optionally, the auxiliary heater is located externally of the thermal store.

Optionally, operation of the auxiliary heater is automatically selective in the event that system water returning from the heat exchanger is insufficient to defrost the energy source, whereby the auxiliary heater additionally heats said system water to a temperature sufficient to perform defrosting of the energy source.

Optionally, the heat exchanger is a plate heat exchanger.

Optionally, the auxiliary heater is an electric heater.

Optionally, the hot water supply apparatus further comprises one or more expansion vessels.

Optionally, the apparatus comprises one or more flow sensors and/or temperature sensors.

Optionally, the hot water supply apparatus comprises a recirculating pump in fluid communication with outlet of the heat exchanger and the cold domestic water inlet.

Optionally, the hot water supply apparatus comprises one or more pressure reducing valves.

Optionally, fluid connection of the header to a central heating system comprises one or more manifolds, valves, mixing valves or a mixture thereof.

Optionally, the central heating system comprises one or more central heating zones and/or underfloor heating systems.

In accordance with an aspect of the invention there is provided a method of augmenting the temperature of the system water in a domestic hot water apparatus or hot water system having a controller, a header, a thermal store and a heat exchanger, wherein the header is configured to receive system water from a primary heat energy source; wherein the header is fluid communication with the thermal store; wherein the thermal store is in fluid communication with the heat exchanger, the heat exchanger configured to receive cold domestic water from a cold domestic water inlet whereby said cold water is conductively warmable by system water received from the thermal store to provide a warm water for a user via an outlet of the heat exchanger; the method comprising the step of activating an auxiliary heater provided intermediate and in fluid communication with the thermal store and the heat exchanger.

Optionally, the step of activating the auxiliary heater is carried out automatically or selectively.

Various examples and aspects of the invention will now be described in detail with reference to the accompanying figures. Still other aspects, features, and advantages of the present invention are readily apparent from the entire description thereof, including the figures, which illustrate a number of exemplary aspects and implementations. The invention is also capable of other and different aspects and implementations, and its several details can be modified in various respects, all without departing from the present invention. Accordingly, the drawings and descriptions are to be regarded as illustrative in nature, and not as restrictive.

Furthermore, the terminology and phraseology used herein is solely used for descriptive purposes and should not be construed as limiting in scope. Likewise, the term "comprising" is considered synonymous with the terms "including" or "containing" for applicable legal purposes.

Any discussion of documents, acts, materials, devices, articles and the like is included in the specification solely for the purpose of providing a context for the present invention. It is not suggested or represented that any or all of these matters formed part of the prior art base or were common general knowledge in the field relevant to the present invention.

All singular forms of members, or any other components described herein are understood to include plural forms thereof and vice versa.

Features or integers of any aspect or example of the invention can be incorporated into any other aspect or example of the invention as appropriate and vice versa.

Brief description of the drawings

Figure 1 is a schematic circuit diagram showing a typical prior art domestic hot water and central heating system; Figure 2A is an exemplary schematic circuit diagram of an exemplary domestic hot water and central heating system and apparatus in accordance with the invention; Figure 2B is an exemplary schematic circuit diagram of an exemplary domestic hot water and central heating system and apparatus in accordance with the invention; and Figure 3 is an exemplary schematic illustration of a domestic hot water apparatus in accordance with the invention.

Detailed description

B

With reference to Figure 1, there is shown an exemplary, typical prior art domestic space heating and domestic hot water (DHW) system 1 associated with a primary energy (i.e. heat) source such as an air source heat pump 10 or other device, for example a source that may have a maximum output of less than 60 C during normal operation. The system includes an inlet 11 for system water from the energy source 10 to flow into the system, and an outlet 12 to return system water back to the energy source. A diverting valve 13 enables the system inlet water to be selectively piped to a buffer tank 14 or through a DHW storage tank 15.

When pumped to a DHW storage tank 15 from the diverting valve 13, the system inlet water conductively heats the water stored in the DHW tank 15 by means of a heat exchanger 16 to provide heated DHW, which can be drawn off by means of a DHW outlet 152 Typically, a DHW tank 15 is a stainless steel hot water cylinder having a cold domestic water inlet 151 and a DHW outlet 152. Within the DHW tank 15 the cold domestic water is conductively heated, in this case by the energy source water via a heat exchange means 16 as described above. The heated water of the DHW tank is stored in readiness for use as DHW. As the temperature of the system inlet water is typically much less than 600, the DHW heated by said water in the DHW tank 15 will be also be much less than 60C. Generally, the maximum achievable DHW flow temperature from a DHW tank is around 50-55C, however in order to meet the requirements for anti-Legionella control, the DHW tank must go through periodic heating cycles to raise the stored DHW temperature to above 60C in accordance with regulations. Accordingly, the DHW tank requires an auxiliary heating means 153 within said DHW tank to raise the DHW water to a useful DHW temperature, and to perform the cyclic heating to above 600. Generally, the auxiliary heating means 153 used to achieve this an electric heater, the use of which consumes significant electrical energy at great expense to the user.

Unvented DHW tanks have specific installation requirements which are not applicable to a DHW system and apparatus in accordance with the present invention.

From the heat exchanger 16, the now cooler system water is then returned to the energy source via the outlet 12. A system expansion vessel 22 may be provided in fluid communication with the outlet 12 of the system.

In an alternative mode, rather than being piped via the diverting valve 13 to the heat exchanger 16, the system inlet water may be piped to the buffer tank 14 which acts a thermal store for heated system water that can be called for during periods of lower output from the primary heat energy source 10, or as an energy reserve to assist with defrosting, for example if the primary heat energy source 10 is an air-source heat pump. A buffer tank 14 is required to assist defrosting of the energy source 10 in periods of cold temperatures and to reduce heat energy source cycling.

In this mode, whereby the system inlet water is held in the buffer tank 14, a circulating pump 19 distributes the system water from said buffer tank 14 through a central heating manifold 20 and optionally via a mixing valve 21 as a direct central heating (CH) source, for example to provide heating via radiators 17, or underfloor heating system 18. After use as a CH energy source, the now cooler system water is returned to the energy source 10 via the outlet 12 of the system. A system expansion vessel 22 may be also provided in fluid communication with the outlet 12 of the system.

It will be noted that the prior art system described above requires two tanks for storage and associated long runs of pipe work and a control means to correctly operate the anti-legionella cycling heating function.

With reference to Figure 2A and Figure 2B, there is shown an exemplary domestic and hot water supply circuit of a system 1 and apparatus 1A (Figure 3) in accordance with examples of the present invention, in which the primary energy source is shown, by way of example only, as an air source heat pump 100 (Figure 2A, 2B). It will be understood that any suitable primary energy source can be used in association with the invention, for example, but not limited to, air source heat pumps, ground source heat pumps, geothermal heat pumps, groundwater heat pumps, oil fired-boilers, gas-fired boilers, solar thermal sources, hot spring power, biomass boilers, exhaust air source heat pumps, etc. With reference to Figures 2A, 2B and 3, the system 1 and apparatus 1A includes an inlet 110 for system water from the energy source 100 to flow into the system, and an outlet 120 to return system water back to the energy source. The inlet 110 and outlet 120 are optionally the inlet and outlet of a header 103. The hot water supplied by the apparatus is particularly suitable for use in domestic hot water (DHW) supply and space heating.

It will be understood that the term 'domestic' does not limit the use of the apparatus and associated system with dwelling houses, but rather should be understood to comprise any construction having a requirement for the supply of hot water supply and/or space heating.

The system 1, and the apparatus 1A further includes a controller (not shown) to control the operation of the system and apparatus following inputs selectively set by a user, for example through a control interface, and/or automatically following inputs from suitable sensors located where appropriate around the system, for example, but not limited to, flow rate sensors, temperature sensors, valve position sensors, etc. In one example of operation, system water from the energy source 100 initially enters a header 130. Preferably, the header 130 is a low loss header. The system water in the header 130 can be utilized to provide a central heating (CH) source by being piped 131 to a central heating manifold 200 and/or a mixing valve 210 (Figure 2). From manifold 200 the system water is dispersed to one or more central heating zones 170 where radiators may be provided. From mixing valve 210 (Figure 2) the system water can be utilized to provide underfloor heating 180. In Figure 3, central heating zone 170 valves 171 are shown. As shown by way of example in Figure 2B, rather than first entering the header 130, system water from the energy source 100 may bypass the header 130, for example via a bypass duct 101, and be piped 131 directly to the central heating manifold 200 and/or mixing valve 210 to provide CH.

In one example, system water from the low loss header 130 can also be ducted, optionally via a flow diverting valve 132, to a buffer tank which acts as a thermal store, for example a vessel 140, where the water is held substantially at its source temperature, for example around 550. From the thermal store 140, the system water is piped to a heat exchanger 1501 where it is circulated to conductively heat water for a system 1500. At the heat exchanger 1501, cold domestic water from a cold domestic water inlet 1510 is conductively warmed by the circulating system water from the thermal store 140, and exits the heat exchanger via an outlet 1520 for use as DHW. The extent of the demand for DHW may be sensed, for example, by a flow sensor or meter 1511 in communication with the water flow from domestic water inlet 1510. An optional recirculating pump 1503 may be provided to recirculate unused DHW from outlet 1520 back to the heat exchanger 1501. Figure 3 additionally shows a DHW pressure reducing valve 1504 and a DHW expansion vessel 1505 which are not shown in the circuit diagrams of Figures 2A and 2B.

As noted above and as shown in Figure 2 and Figure 2A, the apparatus additionally comprises an auxiliary heater 1502 which is operational to heat system water obtained from the primary heat energy source 100 in advance of entry into the heat exchanger 1501.

The system water may be received at the auxiliary heater 1502 directly from the energy source 100, for example via conduit 102 shown for the purposes of clarity in Figure 2B only, or indirectly from the energy source via one or more of the header 130 and/or the flow diverting valve132 (for example via conduit 133 shown for the purposes of clarity in Figure 2B only), or the thermal store 140.

Optionally, the system is configured for selective direct fluid communication between the auxiliary heater 1502 and the primary heat energy source 100, or for indirect fluid communication between the primary heat energy source 100 via one or more of the header 130, the flow diverting valve 132, and/or the thermal store 140.

Operation of the auxiliary heater can be manually selective or automatically selective in the event that the system water from the energy source 100, received either directly or indirectly by the auxiliary heater 1502 as described above, has insufficient energy to heat the cold domestic water received by the heat exchanger 1501 to a desired level. Auxiliary heater 1502 is thus selectively or automatically operational to supplement the heat energy of the system water from the energy source 100 (either received directly from said energy source or, for example, as stored in the thermal store 140) in the event it has insufficient energy to meet DHW demand or to perform defrosting of the energy source, as described below.

Furthermore, if the energy source, for example a heat pump 100, is not performing correctly or to capacity, the auxiliary heater 130 is operational to raise the temperature of the system water received from said energy source, to meet a DHW demand.

The auxiliary heater 1502 is located intermediate the thermal store 140 and the heat exchanger 1501, and is in fluid communication with said thermal store and heat exchanger.

It should be noted that the auxiliary heater 1502 is external and/or spaced apart from the thermal store/buffer tank 140.

As the auxiliary heater 1502 is located externally of the thermal store/buffer tank 140, and as the system of the invention does not include a DHW tank, only that amount of water required by a DHW demand is heated, rather than heating all the water which would otherwise be stored in a DHW tank of a prior art system and apparatus. Accordingly, this arrangement reduces energy consumption in comparison to traditional apparatuses and systems having a DHW storage tank.

From an outlet 1506 of the plate heat exchanger 150, the now cooler system water can be returned to the energy source 10 via a diverting valve 160, circulator 190, and header 130, or can be selectively or automatically returned to the thermal store via flow diverting valve 132. When returned to the heat energy source 100, return system water is usable to defrost said energy source 100 during periods of low temperature. Where the heat energy of the system water returning from the heat exchanger 1501 is insufficient to defrost the heat energy source 100, the auxiliary heater 1502 is operational to additionally heat the system water to a temperature sufficient to perform defrosting.

Circulator 190 may be described as a hydraulic group circulator, and diverting valve 160 may be described as a hydraulic group diverting valve, the combined function of which is to modulate the flow of system water from the thermal store 140 to the heat exchanger 1501 via the auxiliary heater 1502. This operation allows the DHW temperature to be maintained.

Advantageously, as the system and apparatus in accordance with the present invention does not require a DHW storage tank, the requirement for performing periodic heating cycles to raise the temperature of stored DHW to above 60C in order to meet the requirements for anti-Legionella control is obviated. Additionally, the absence of a DHW storage tank means that an apparatus in accordance with the system can be made to a more compact size relative to prior art devices which require two storage cylinders, i.e. traditional two-cylinder installations having a buffer tank/storage tank 14 and a DHW storage tank 15, as shown in Figure 1.

To improve performance when starting from cold, diverting valve 132 may be selectively set to return the system water to the header 130 for a period of time, or until certain conditions are met, for example, a temperature condition.

Exemplary operation of the system and apparatus to produce DHW is summarized by the following steps: 1 A user pre-sets a desired DHW flow temperature via a user interface.

2 Heated system water is provided by the primary energy source 100 to the low loss header 130. Depending on the temperature of the system water, it may either be fed to the thermal store/buffer tank 140, or circulated back to the low loss header 130. This is controlled by the flow diverting valve 132.

3. DHW demand is detected by flow sensor 1511 of the inlet group.

4. The Hydraulic Group circulator 190 starts.

5. The Hydraulic Group return diverting valve 160 moves to a DHW position.

6. DHW flow temperature is measured, along with flow rate.

7. If there is insufficient energy in the heated system water to meet the DHW demand, auxiliary heater 1502 is activated to supplement the system water energy used for DHW production within the heat exchanger 1501.

8. The controller will determine whether to take energy from either the thermal store, directly from the energy source, or a mixture of both depending on the available energy from each. The available energy may be determined by temperature sensors located on these devices.

An example of operation of the apparatus to provide defrost assistance for the primary energy source, for example a heat pump 100, is summarized by the following steps: 1 The heat pump 100 generates a signal to the controller indicating that defrosting is required, or alternatively by means of temperature measurement, the controller is alerted that defrosting is required.

2 If the energy stored within the buffer tank/ thermal store 140 is insufficient to allow correct defrost operation, the auxiliary heater 1502 is activated to supplement the system water energy used for defrosting. Also, during this time the Hydraulic Group diverting valve 160 moves to a DHW position, and the Hydraulic Group circulator 190 starts to allow water heated by the auxiliary heater 1502 to flow into the buffer tank 140.

The operation of the device and system in central heating (CH) mode is summarized by the following steps: 1. A user pre-sets a desired CH flow temperature for one or more zones via a user interface.

2. Heated system water is provided by the primary energy source 100 to the thermal store/buffer tank 140.

3. Depending on the system requirements, appropriate central heating zone 170 valves are called to open.

4. The Hydraulic Group diverting valve 160 moves to a CH position, the circulator 190 operates.

5. Heated CH water is supplied to the appropriate CH circuits.

6. Central heating zones 170 may be controlled by internal or external controls.

Advantageously, the apparatus and system includes numerous functions and advantages, which are not limited to: (i) Acts as a buffer tank for system water (ii) Supplies instantaneous, hygienic DHW without the requirement for antilegionella function.

(iii) The capability to increase the DHW temperature if required to meet user requirements.

(iv) Takes advantage of electricity tariff reduction during certain working hours.

(v) Allows modular integration of expansion capacity for the system.

(vi) Allows the modulation of DHW temperature as required. (vii)Allows direct connection to a heat pump, or other system.

(viii) Is suitable for location external of a property.

(ix) Is suitable for location within a property.

(x) Contains typical components to allow connection to a zoned space heating system.

(xi) Has a lower predicted installation cost in comparison to a traditional two-cylinder installation.

Claims

CLAIMS1. A hot water system or apparatus suitable for use with a primary heat energy source, the system comprising a heat exchanger and an auxiliary heater, wherein the auxiliary heater is configured to receive system water from a primary heat energy source and is in fluid communication with the heat exchanger; wherein the heat exchanger is configured to receive cold domestic water from a cold domestic water inlet, whereby said cold water is conductively warmable by the system water received from the auxiliary heater to provide warm water via an outlet of the heat exchanger.
2. A hot water system or apparatus as claimed in claim 1, wherein the system further includes a header, a flow diverting valve and a thermal store.
3. A hot water system or apparatus as claimed in claim 2, wherein the auxiliary C\I heater is located externally of the thermal store, and optionally spaced apart from the thermal store.CD
4. A hot water system or apparatus as claimed in any preceding claim, wherein CO 20 the auxiliary heater is configured for direct fluid communication with a primary heat energy source.
5. A hot water system or apparatus as claimed in claim 2 or claim 3, wherein the auxiliary heater is configured for indirect fluid communication with a primary heat energy source via one or more of the header, the flow diverting valve, or the thermal store
6. A hot water system or apparatus as claimed in claim any one of claims 2 to 5, wherein the system is configured for selective direct fluid communication between the auxiliary heater and a primary heat energy source, or indirect fluid communication between a primary heat energy source via one or more of the header, the flow diverting valve, the thermal store.
7. A hot water system or apparatus as claimed in any preceding claim, wherein the system comprises a controller to control the operation of the system and apparatus following inputs selectively set by a user, for example through a control interface, and/or optionally automatically following inputs from suitable sensors located where appropriate around the system.
8. A hot water system or apparatus as claimed in any preceding claim, wherein the auxiliary heater is operational to heat system water obtained directly or indirectly from a primary heat energy source in advance of entry into the heat exchanger.
9. A hot water system or apparatus as claimed in any preceding claim, wherein the auxiliary heater is operationally intermediate and in fluid communication with the primary heat energy source and the heat exchanger.
10. A hot water system or apparatus as claimed in any preceding claim, wherein C\I the auxiliary heater is operationally intermediate and in fluid communication with the header and the heat exchanger.CO 20
11. A hot water system or apparatus as claimed in any one of claims 1 to 9, wherein the auxiliary heater is operationally intermediate and in fluid communication with the flow diverting valve and the heat exchanger.
12. A hot water system or apparatus as claimed in any one of claims 1 to 9, wherein the auxiliary heater is operationally intermediate and in fluid communication with the thermal store and the heat exchanger.
13. A hot water system or apparatus as claimed in any one of claims 2 to 12, wherein the thermal store is configured to receive system water from the primary heat energy source via the header, and optionally via the flow diverting valve.
14. A hot water system or apparatus as claimed in any one of claims 1 to 9, wherein the auxiliary heater is operational to heat the system water from the thermal store in advance of entry into the heat exchanger.
15. A hot water system or apparatus as claimed claim 14, wherein operation of the auxiliary heater is automatically selective in the event that the system water from the thermal store has insufficient energy to heat the cold domestic water received by the heat exchanger.
16. A hot water system or apparatus as claimed in any one of claims 2 to 15, wherein the heat exchanger includes an outlet that is in fluid communication with one or more diverting valves and a circulator, so that system water from the heat exchanger is selectively returnable to the header or to the thermal store.
17. A hot water system or apparatus as claimed in any preceding claim, wherein operation of the auxiliary heater is automatically selective in so that the event that system water returning from the heat exchanger is insufficient to defrost the energy source, the auxiliary heater additionally heats said system water prior to entry into the heat exchanger to a temperature sufficient to perform defrosting of the energy source. C\I
18. A domestic hot water system comprising a hot water supply apparatus suitable for use with a primary heat energy source, the hot water apparatus CO 20 comprising a controller, a header, a thermal store, a heat exchanger and an auxiliary heater, wherein the header is configured to receive system water from a primary heat energy source; wherein the header is fluid communication with the thermal store; wherein the thermal store is in fluid communication with the heat exchanger, wherein the heat exchanger configured to receive cold domestic water from a cold domestic water inlet whereby said cold water is conductively warmable by system water received from the thermal store to provide warm water for a user via an outlet of the heat exchanger, and wherein the auxiliary heater is provided intermediate and in fluid communication with the thermal store and the heat exchanger; and wherein the auxiliary heater is operational to heat the system water from the thermal store in advance of entry into the heat exchanger.
19. A domestic hot water system as claimed in claim 18, wherein the auxiliary heater is located externally of the thermal store.
20. A domestic hot water system as claimed in claim 18 or 19, wherein operation of the auxiliary heater is automatically selective in the event that the system water from the thermal store has insufficient energy to heat the cold domestic water received by the heat exchanger.
21. A domestic hot water system as claimed in any one of claims 18 to 20, wherein the heat exchanger includes an outlet that is in fluid communication with one or more diverting valves and a circulator, so that system water from the heat exchanger is selectively returnable to the header or to the thermal store.
22. A domestic hot water system as claimed in any one of claims claim 18 to 21, wherein operation of the auxiliary heater is automatically selective in the event that system water returning from the heat exchanger is insufficient to defrost the energy source, whereby the auxiliary heater additionally heats said system water to a temperature sufficient to perform defrosting of the energy source.
23. A hot water system or apparatus as claimed in any preceding claim, wherein the heat exchanger is a plate heat exchanger, and optionally wherein the auxiliary CO 20 heater is an electric heater.
24. A hot water system or apparatus as claimed in any preceding claim, further comprising one or more expansion vessels, one or more flow sensors and/or temperature sensors, and a recirculating pump in fluid communication with outlet of the heat exchanger and the cold domestic water inlet.
25. A method of augmenting the temperature of the system water in a domestic hot water apparatus or hot water system having a controller, a header, a thermal store and a heat exchanger, wherein the header is configured to receive system water from a primary heat energy source; wherein the header is fluid communication with the thermal store; wherein the thermal store is in fluid communication with the heat exchanger, the heat exchanger configured to receive cold domestic water from a cold domestic water inlet whereby said cold water is conductively warmable by system water received from the thermal store to provide a warm water for a user via an outlet of the heat exchanger the method comprising the step of activating an auxiliary heater provided intermediate and in fluid communication with the thermal store and the heat exchanger.