GB2507756A - A thermal store in combination with an electrical heater, particularly an electrical flow boiler - Google Patents

Abstract

An electrical heater 2 is arranged to supply thermal energy to a thermal store 1. Preferably the electrical heater is an electrical flow boiler and the thermal store is a hot water tank. A domestic hot water and central heating system may comprise the hot water tank and electrical flow boiler in addition to a heat exchanger 5, a three-way valve 18, a mains water supply 14 and a pump 6. The heat exchanger is preferably arranged to heat the mains water by thermal exchange with the heated water from the tank in co-operation with a flow sensor 4 and thermostatic mixing valve 10 to provide domestic hot water. The three-way valve is preferably arranged to direct water to the electrical flow boiler from at least one of the heat exchanger or the tank. Where water is delivered to the electrical flow boiler from the tank, the water is preferably first passed through a central heating system via flow and return pipes 8,7. The boiler can be provided outside the thermal store or within the thermal store (figure 2). The system disclosed permits use of a flow boiler with an interruptible off-peak electricity supply because of the thermal store.

Description

THE USE OF THERMAL STORAGE WITH FLOW BOILERS

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 Application 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 Application 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 usc 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 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 takc a long time and thus bc extremely costly in labour.

Patent Application No GB 2423569 tcachcs that using a thrcc port valve and pump on thc return of the heating and domestic hot water heat exchanger circuit of a thermal storage combination boiler cxtcnds thc life of the pump and motorised thrcc port valve by subjccting 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 prcdicting 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 while incorporating the advantages of Patent Application No GB 2423569 extending the component life and of automatic pump and motorised valve "exercising" and permitting different flow tapping positions in the thermal store that are part of the features of Patent Application No GB 2423569.

According to the present invention there is provided a heat exchange medium filled thermal store for the supply of thermal energy from the said thermal store to a heat exchanger for providing domestic hot water and/or providing thermal energy to a wet central heating system, said thermal store having at least one electric flow boiler providing heat energy to the said thermal store, said thermal store, said heat exchanger and said flow boiler being provided with at least one circulating pump, controls and pipework to form a thermal storage combination boiler or by omitting the said heat exchanger a thermal storage boiler; the said thermal storage combination boiler/boiler, having its heating system pump, controls, pipework and heat exchanger forming at least one permanent flow path for the heat energy from the said flow boiler to enable the said flow boiler to dissipate its generated heat via the said permanent flow path to the said thermal store and/or heat exchanger and/or heating system; the said thermal store additionally being optionally fitted with standby or stand-alone immersion heater/s and or provision for accepting additional heat input/s.

Although the present invention is described for clarity having the controls, pump and three port motorised valve configured as in Patent Application No GB 2423569 to take advantage of the features of that Patent it should be understood that other control and flow boiler configurations can be substituted where circumstances dictate.

Although the present invention describes for clarity an electric thermal storage combi boiler having a flow boiler mounted integrally on or in the outer casing of the said electric thermal storage eombi boiler that is the preferred form of the present invention it should be understood that the electric thermal storage eombi boiler may be substituted by a thermal storage boiler only form having no integral domestic hot water producing means.

Although the present invention describes for clarity an electric thermal storage eombi boiler having a flow boiler mounted integrally on or in the outer casing of the said electric thermal storage combi boiler that is the preferred form of the present invention it should be understood that the said flow boiler may be a plurality of flow boilers and may be fitted remotely to the said thermal storage boiler/combi boiler.

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 invcntion is described as having a flow boilcr as a hcat sourcc thc 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.

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 before the flow boiler it may alternatively be located after 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 lisa 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 ifirther form of the present invention showing the flow boiler and controls remote to the thermal store.

Drawing 4 is a diagrammatic illustration of a ifirther form of thc prcscnt 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 easing.

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 I and/or flow boiler 2 temperature control (not shown) is satisficd thc heating elcmcnt!s (not shown) in the flow boiler 2 is/arc 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) rcduce the flow around thc ccntral hcating circuit (not shown) thc 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 mcasure flow by paddle switch, tcmpcraturc differcntial switching or tempcraturc drop switching or other flow sensing means. On sensing flow the motorised valve 1 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 domcstic hot water flow pipc 9 advantageously sited higher in thc thcrmal store 1 then thc 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 I now flows through the primary side of the licat 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

S

thermal store I through domestic hot water flow pipe 9, domestic hot water heat exchanger 5, domestic hot watcr 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 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 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 I 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.