EP2730853B1

EP2730853B1 - Thermal storage with external instant heater

Info

Publication number: EP2730853B1
Application number: EP13191637.1A
Authority: EP
Inventors: Nicholas Julian Jan Francis Macphail
Original assignee: Individual
Current assignee: Individual
Priority date: 2012-11-08
Filing date: 2013-11-05
Publication date: 2017-08-30
Anticipated expiration: 2033-11-05
Also published as: GB201220094D0; EP2730853A1; GB2507756A; GB2507756B

Description

I, NICHOLAS JULIAN JAN FRANCIS MACPHAIL, a British subject of Mas des Sables, Grandes Rocques, Guernsey of the Channel Islands do hereby declare the invention for which we pray that a patent may be granted to me and the method by which it is to be performed to be particularly described in and by the following statement:-
THIS INVENTION RELATES TO USE OF THERMAL STORAGE WITH FLOW BOILERS
It is known from Patent No GB 2266762 and Patent No GB 2423569 that thermal storage with heating means can be used together with a mains water heating heat exchanger as a mains water flow heating means can be used to improve the domestic hot water flow rate of a "combi" boiler. It is further known from Patent No GB 2266762 and Patent No GB 2423569 that thermal storage can be used to store intermittent energy input from, for example, off peak electricity supply, solar thermal, wind or photovoltaic generated electricity. Thermal storage can be used as a buffer for air source heat pumps, CHP and similar devices to prevent short cycling wear and inefficiency. They also enable smaller heating units to be used so that the base loads can be met by the heat generator with the thermal store being additionally deployed to meet peak loads. This type of thermal storage boiler by its ability to accept intermittent heat input and store it until output is required (often at night when "green" inputs e.g. solar may have ceased) enables and encourages uptake of "green" inputs from solar and other "responsible" sources. Thermal storage also helps electricity companies to "load level" and "load match" making more efficient use of generating and distribution plant.
In current forms that use intermittent off peak electricity the thermal store is heated with electricity using one or more immersion heaters.
A disadvantage of immersion heaters is that a plurality of joints is generally needed leading to a plurality of large tappings being required in the thermal store with an attendant increase in production cost and risk of leaks both from the joints at the tappings and from the immersion heaters themselves. They need replacing as their life is not infinite. To replace an immersion heater would be a fairly simple fast process but for the need to drain the large thermal store. This process of draining down and refilling the thermal store can take several hours. This can involve long delays if the store has to be cooled to a safe temperature before draining down can be carried out. This means that the simple replacement of a failed immersion heater component can take a long time and thus be extremely costly in labour.
Patent No GB 2423569 teaches that using a three port valve and pump on the return of the heating and domestic hot water heat exchanger circuit of a thermal storage combination boiler extends the life of the pump and motorised three port valve by subjecting them to the cooler return water. Because the three port valve and pump are both naturally and, without complex electronics, actuated for the provision of domestic hot water throughout the year, the build up of plated out detritus on the rubbing surfaces of the components that causes premature failure by seizure is prevented. Also the pump and three port valve location on the heating and domestic hot water return enables the flow to the heating to be taken from lower down the thermal store than the flow to the domestic hot water heat exchanger effectively leaving a reserve of thermal energy for domestic hot water production.
Flow boilers are non storage electric boilers that have the advantage of being extremely cheap in manufacture compared to direct combustion boilers. However, as they have no thermal storage their heat output ceases the moment they are turned off. This makes them suitable solely for connection to the peak rate twenty four hour electricity supply as connection to an interruptible off peak supply would leave the householder without heat shortly after the off peak supply is shut off. Flow boilers alone do not offer the load levelling and load predicting advantages to the generating companies that electric thermal storage boilers do and so are not normally allowed to be connected to an off peak supply or benefit from its cheaper running cost.
"Flow boilers" have the added disadvantage of needing a dedicated pump providing continuous flow while they are producing heat to ensure sufficient dissipation of the heat they produce to the heating and/or domestic hot water system to which they are connected. This is to prevent their very small water content rising in temperature too fast for their thermostatic control to safely and effectively regulate.
It is the object of the present invention to overcome the disadvantages of the prior art of immersion heaters being fitted directly into a thermal storage boiler/combi boiler and to overcome the disadvantages of flow boilers lacking thermal storage and requiring a separate dedicated pump. The present invention may be used with Patent No GB 2423569 for extending the component life and of automatic pump and motorised valve "exercising" and permitting different flow tapping positions in the thermal store.
GB2352805 (Gledhill Water Storage Limited) discloses a hot water system. The system comprises a thermal storage tank and a primary water circuit heated by a gas or an oil fired boiler. The hot water system is also provided with an additional electric water heating means.
According to the present invention there is provided a heating arrangement according to claim 1.
Although the present invention is described for clarity as an electric thermal storage combi boiler having a pump and controls separate from the flow boiler it should be understood that the pump and/or controls may be integral to the flow boiler or not and the flow boiler may be integral with the thermal store or not.
Although the present invention is described for clarity as an electric thermal storage combi boiler having the pump integral with the controls, it should be understood that the pump may instead be integral with the flow boiler or separate from both the flow boiler and the controls.
Although the present invention is described as having a flow boiler as a heat source the term flow boiler should be taken to mean any electrical heat producing means that can be fitted externally to the thermal store ideally enabling it to be isolated either by valves or by pipe freezing for its speedy replacement and/or servicing. Alternatively the term flow boiler may be interpreted as meaning a non-storage electrical boiler.
Although the block diagram and description refers to the controls either in or on the thermal store casing or remotely located with the flow boiler this does not preclude some or all the controls being with one or the other or located separately from both.
Although the pump is shown upstream of the flow boiler in the direction of flow of the heat exchange medium, it may alternatively be located downstream of the flow boiler.
Expansion system, safety system, heating circuit and filling means have been omitted for clarity.
The invention will now be described by example with reference to the following drawings wherein
Drawing 1 is a diagrammatic illustration of the preferred form of the present invention with its components spaced apart for clarity.
Drawing 2 is a diagrammatic illustration of the preferred form of the invention in Drawing 1 with the flow boiler mounted in or on the casing of the thermal store with the major components shown in block form for clarity.
Drawing 3 is a diagrammatic illustration of a further form of the present invention showing the flow boiler and controls remote to the thermal store.
Drawing 4 is a diagrammatic illustration of a further form of the present invention showing the thermal store with the flow boiler remote from the thermal store but with the controls mounted in or on the thermal store casing.
Referring firstly to Drawing 1 there is shown a thermal store 1 with a standby/stand alone immersion heater 3 within it. Assuming the thermal store temperature control (not shown) is calling for heat and the central heating controls (not shown) are calling for heat the pump 6 causes water in the thermal store 1 to flow through flow pipe 8 around the central heating circuit (not shown) to the heating return pipe 7 then through the three port valve 18 pump 6 and through the flow boiler 2 where the water is heated before returning via common return pipe 13 to the thermal store 1. When the thermal store 1 and/or flow boiler 2 temperature control (not shown) is satisfied the heating element/s (not shown) in the flow boiler 2 is/are turned off. If the central heating control (not shown) is still calling for heat the pump 6 continues to run and the three port valve 18 remains open to the central heating circuit (not shown). If there is a central heating demand but controls such as thermostatic radiator valves (not shown) reduce the flow around the central heating circuit (not shown) the automatic bypass valve 19 will be opened proportionally to maintain its set differential pressure and flow around the central heating circuit (not shown) and or through the bypass valve 19 via the three port valve 18, pump 6, flow boiler 2 and common return 13 to the thermal store 1. This maintains a flow through the flow boiler in the event of such other controls limiting the flow through the heating circuit (not shown). When there is a demand for domestic hot water, the cold mains water enters via cold mains water inlet 14 through flow sensor 4 which may measure flow by paddle switch, temperature differential switching or temperature drop switching or other flow sensing means. On sensing flow the motorised valve 18 closes the port to the central heating return pipe 7 and opens the port to domestic hot water heat exchanger 5 return pipe 12 and actuates the pump 6. The pump 6 now draws water from the domestic hot water flow pipe 9 advantageously sited higher in the thermal store 1 then the heating circuit flow pipe 8 to maintain a reserve of thermal energy dedicated to domestic hot water supply. The water drawn from the thermal store 1 now flows through the primary side of the heat exchanger 5 through the motorised valve 18, pump 6, flow boiler 2 and common return pipe 13 to the thermal store 1. Thus if there is a demand for central heating or domestic hot water the pump 6 runs and the flow of water is maintained through the flow boiler 2 to allow any heat it produces to be transferred to the thermal store.
Should there be a demand for heat from the thermal store 1 and the flow boiler 2 temperature controls (not shown) but no demand from either the central heating or domestic hot water control the thermal store 1 and/or flow boiler 2 temperature control/s (not shown) will actuate the three port valve 18 to open the port to the domestic hot water return pipe 12, close the port to the central heating return 7 and actuate the pump 6 to maintain a flow of water from the thermal store 1 through domestic hot water flow pipe 9, domestic hot water heat exchanger 5, domestic hot water return pipe 12, three port valve 18, pump 6, flow boiler 2 and common return pipe 13 to return the water so circulated heated by the flow boiler 2 to the thermal store 1. Whether there is central demand, domestic hot water demand or neither a flow of water is maintained through the flow boiler 2 to dissipate its heat whenever its controls (not shown) demand. When there is no demand for heat from any of the controls (not shown) the motorised valve 18 is unactuated and the circulating pump 6 and flow boiler 2 are disabled.
The immersion heater 3 (if fitted) enables the standby or stand alone production of heat in the water in the thermal store 1 to enable the production of heated domestic hot water and some heating in the event of flow boiler 2 malfunction or servicing. It may be alternatively wired to 24 hour supply to provide a boost input if needed. The thermostatic mixing valve 10 mixes cold water from the mains 14 with hot water from the domestic hot water heat exchanger 5 to the thermostatically regulate hot water exiting from the taps via hot water outlet 11.
The automatic air vent 15 enables venting of air during initial filling and the small amounts of air and/or reaction gases that separate from the circulating water in normal system use.
The dotted box 16 surrounding the control and heat exchange items in Drawing 1 is to simplify the box layouts in Drawings 2, 3 and 4 and contains the same components within the box shown in Drawing 1.
The thermal store 1 may be conveniently formed from metal or composites and may utilise commercially available cylinder/s.
The flow boiler 2, immersion heater 3, flow sensor 4, heat exchanger 5, pump 6, thermostatic mixing valve 10, automatic air vent 15, motorised valve 18 and automatic bypass valve 19 may all be conveniently standard commercially available items or may be specially fabricated according to need.
The skilled reader will appreciate that, if no suitable flow is established through a flow boiler, the flow boiler can overheat very rapidly, causing malfunction and/or damage. The arrangement of a heating system in accordance with the present invention allows both the heating and hot water circuits to include the flow boiler, to ensure that there is a flow of water through the flow boiler whenever there is a demand for hot water or heating. A permanent flow path through the flow boiler is thereby established, by which is meant a flow path that permanently includes the flow boiler whenever water is drawn from the thermal store. The skilled reader will appreciate how this will help to ensure that the likelihood of overheating at the flow boiler is minimised.
In the description above, a single three-port valve is used to control whether the flow from the thermal store is directed through the hot water circuit and the heating circuit. However, this need not be the case. In other embodiments, respective valves may be provided, one as part of the hot water circuit and the other as part of the heating circuit. The control of these valves may be coordinated to ensure that the flow from the thermal store is directed through either the heating circuit or the hot water circuit, as required. Each of these valves may be a two-port valve, a three-port valve, or be of any other suitable design.
In the examples above, a single pump is provided, on pipework that is common to both the heating and hot water circuits. Again, this need not be the case, and respective first and second pumps may be provided, one as part of the hot water circuit and the other as part of the heating circuit. The skilled reader will understand how these pumps may be controlled during the operation of the system.
In the description above, the flow boiler is provided as part of a common return, i.e. pipework that carries flow back to the thermal store after having passed through the wet central heating circuit or through the heat exchanger for providing domestic hot water. However, it is envisaged that the flow boiler may be provided on a common flow pipe, i.e. a pipe that carries flow to the wet central heating circuit or to the heat exchanger for providing domestic hot water from the thermal store. In other words, the flow boiler may be either upstream or downstream of the wet central heating system and the heat exchanger for the domestic hot water. Indeed, a common pump and/or three-port valve may also be either upstream or downstream of the wet central heating system and the heat exchanger for the domestic hot water.
When used in this specification and claims, the terms "comprises" and "comprising" and variations thereof mean that the specified features, steps or integers are included. The terms are not to be interpreted to exclude the presence of other features, steps or components.

Claims

A heating arrangement comprising:
a heat exchange medium filled thermal store (1) for the supply of thermal energy from the thermal store (1) to a wet central heating system and/or to a heat exchanger (5) for providing domestic hot water;

at least one electrical electric flow boiler (2) fitted externally to the thermal store (1) providing heat energy to the thermal store (1) to provide heat energy to the said thermal store (1);

at least one circulating pump (6), controls and pipework to form a thermal storage combination boiler, wherein

the heating arrangement comprises a central heating circuit through which heat exchange medium may flow from the thermal store (1) to supply thermal energy to the wet central heating system;

the heating arrangement comprises a hot water circuit through which heat exchange medium may flow from the thermal store (1) to supply thermal energy to the heat exchanger (5); and
both the central heating circuit and the hot water circuit include the flow boiler (2), and the pipework forms at least one permanent flow path for the heat energy from the flow boiler (2) to enable the flow boiler to dissipate its generated heat via the permanent flow path to the said thermal store (1) and/or heat exchanger (5) and/or heating system, wherein the electric flow boiler(2) is positioned on a common return pipe (13) from the central heating circuit and the hot water circuit to the thermal store (1), or wherein the electric flow boiler (2) is positioned on a common flow pipe (13) leading from the thermal store (1) to the central heating circuit and the hot water circuit.
A heating arrangement according to claim 1, wherein both the central heating circuit and the hot water circuit include the circulating pump (6).
A heating arrangement according to any preceding claim, further comprising a valve (18) to switch between the central heating circuit and the hot water circuit.
A heating arrangement according to claim 3, wherein the valve (18) is a three-port motorised valve.
A heating arrangement according to any one of claims 1 to 4, comprising respective first and second valves, the first valve being located on the central heating circuit and the second valve being located on the hot water circuit.
A heating arrangement according to claim 5, wherein each of the first and second valves is a two port valve or a three-port valve.
A heating arrangement according to any preceding claim wherein the thermal store (1) is fitted with standby or stand-alone immersion heater/s (3).
A heating arrangement according to any preceding claim wherein the said thermal store (1) is fitted with provision for accepting additional heat input/s.
A heating arrangement according to any preceding claim wherein the electrical heat producing means (2) is the main source of thermal input for the thermal store (1).
A heating arrangement according to any one of claims 1 to 9 wherein the electrical flow boiler (2) is the sole source of thermal input for the thermal store (1).