GB2235280A - Thermal storage heaters - Google Patents

Abstract

A storage heater, providing heat by radiation, comprises an internal circuit for the passage of heated air. The heater comprises: a heat storage core 2, comprising heat storage rods 12 heated by resistance wiring 14, and an air space 6 around the rods, the air space forming an inner pathway of circuit; heat insulation 4 around the core; and outer pathways 8 adjacent outer walls 10 of the heater. A damper 16 is arranged at the top of the inner and outer pathways to control the communication therebetween. The damper may be movably supported on a support part by robust bi-metallic strips wound with heater wires to control the bending of the strips. The storage heater may be supplied in kit form for the purchaser to assemble and to this end the heat storage rods may comprise particulate material poured into tubes, or liftable core units. Further heat insulation may be selectively positioned in the outer pathways 8 to provide an even heat distribution. <IMAGE>

Description

STORAGE HEATER The invention relates to storage heaters, that is, heaters intended to store heat for a period of time prior to emitting it. Such heat is commonly produced using cheap rate electricity available at night, and is emitted during the day, when electricity is more expensive.

With existing storage heaters, air which has passed over the heated core within the storage heater, and has thereby gained heat, exits from the storage heater and mixes with the air in the room to be heated. The storage medium is generally made up of blocks. The warm air which exits from the storage heater commonly contains a small amount of burnt household dust. Existing storage heaters have fairly thin insulation around the core, so that a substantial proportion of the heat they emit is by radiation from the panels of the heater following the conduction of heat through the thin insulation. The user has no control over this heat emission.

In accordance with the present invention there is provided a storage heater having an electrically heated heat storage core; an inner pathway, alongside or within the heat storage core, for passage of a heat transfer fluid; heat insulation substantially enveloping the heat storage core and the inner pathway; an outer pathway, between an outer wall of the storage heater and the heat insulation, for passage of the heat transfer fluid; wherein the inner and outer pathways form a substantially closed circuit for the heat transfer fluid; and means for controlling the circulation of the heat transfer fluid in the circuit.

Preferably, the heat transfer fluid is air, although other gaseous or liquid media could be used.

Preferably, the insulating medium is sufficiently effective that the heat which passes through it from the inner pathway to thereby reach the outer pathway is less than, and preferably insubstantial compared with, the heat which may reach the outer pathway from the inner pathway by circulation. Thus, a storage heater in accordance with the present invention may be accurately controlled by a user during a heat release phase; and has little heat loss during a heat storage phase when circulation of heat transfer fluid does not take place.

The heat storage core may suitably comprise a fluent heat storage medium, that is, a heat storage medium that can be poured into place. Preferably, such a heat storage medium is particulate. For example, silica sand, quartz or magnesium oxide may be employed. Preferably, particulate material of at least two size grades is employed, the size grades being selected so that the interstices between the particles of the coarser grade may contain particles of a finer grade. Preferably, different grades are poured into the core sequentially, starting with coarser grade material and progressing to finer grade material. Preferably two size grades are employed, the first to be introduced suitably comprising coarse particles with a mean diameter of at least about 5mm and the second comprising fine particles with a mean diameter not exceeding about O.lmm.

Alternatively, and preferably, the heat storage core may suitably comprise a plurality of relative easilylifted heat storage core units, each suitably comprising at least one heat storage block and preferably a plurality of heat storage blocks, carried on a sheathed heating element. Suitably, on location of such a unit in place in the storage heater, an electrical connection is made, whereby the heating element may selectively be powered.

For example, terminal pins, suitably at the base of the unit, may engage contact pads, or in female contacts, carried by the base of the storage heater.

Preferably, each such heat storage core unit comprises a lifting handle which is preferably constituted by the sheathed heating element, which is of robust construction. Suitably, one or more heat storage blocks is engagable over the handle to cover it, once the unit has been located in the storage heater.

In a preferred construction a heat storage core unit as described above comprises two side-by-side heat storage rods each constituted by at least one heat storage block, and preferably a plurality of blocks, carried on a sheathed heating element, the element being, in its uppermost region, in the form of a looped lifting handle extending from one rod to the other, the handle being covered, in use, by a further block on the top of each of the rods.

The use of a fluent heat storage medium or of heat storage core units has the advantage that the purchaser may buy the storage heater in kit form, the relatively light storage heater body being separate from the heavy core components. He may then fit the storage heater in place, adjacent or on a wall, for example, and introduce the heat storage core into the storage heater. In the case of a fluent heat storage medium, the storage heater body is pre-wired. The purchaser simply pours the heat storage medium in place. When heat storage core units are used, the storage heater body and the units are both prewired and on location of the units in the storage heater body the required electrical connections are made to enable the storage heater to be used.

When the heat storage core employs a fluent heat storage medium, the heat storage core comprises a container to retain it. Suitably the container comprises a plurality of cylinders, for example stainless steel tubes.

Suitably, the storage heater is arranged upright, with the heat storage core and inner and outer pathways arranged substantially vertically. Suitably two outer pathways extend alongside the two large outer walls of such a storage heater. The heat transfer fluid may circulate by natural or forced convection. Preferably, however, it circulates by natural convection.

The insulating medium may, for example, be a refractory material, containing, for example, silica, quartz, lime, magnesia, calcium oxide, alumina etc.

Preferably, circulation of the heat transfer fluid in the circuit is controlled by a damper or dampers arranged to vary the cross-sectional area of the circuit for the heat transfer fluid at at least one point in the circuit.

Preferably a damper is arranged at the top and/or bottom of the storage heater, preferably at the top, to control whether or not the inner and outer pathways communicate in that region, at any given time; and preferably to control the cross-section of the circuit in that region. The damper may be under control of a person, either direct mechanical control or via an electrical control, and/or under the control of a thermostat, sensing the room temperature or a temperature associated with the storage heater, and/or under the control of a time clock.

Preferably, the damper control arrangement is arranged to permit the damper to open in the event of power failure so that the heat stored in the storage heater may be released.

Preferably the damper is so constructed as to be substantially resistant to degradation and/or distortion by heat. It may comprise a rigid cover part comprised by at least two parts arranged end-to-end, with an expansion joint therebetween. The cover part may have heat insulation beneath it. The damper may comprise a gasket formed by an insulating blanket around a rigid part which provides a support skirt or rim in the contact region of the damper, the rigid part being mounted to the cover part.

Preferably the damper is movably mounted to a damper support member of the heater. Preferably the damper and the damper support member form a removable/replaceable unit. On location of the unit the damper support member engages in place leaving the damper free to move.

Preferably the damper is mounted to the damper support member via bi-metallic strips, supporting respective ends of the damper. When the damper opens (i.e. moves to permit circulation) the strips are subject to hot heat transfer fluid which causes them to bend and move the damper towards or to its closing position. This acts to reduce or terminate the circulation of heat transfer fluid, which tends to cause the bi-metallic strips to cool and straighten, urging the damper open again. It will be appreciated that by means of this arrangement the damper has a temperature dependent "trimming" action.Each bimetallic strip may be wound with a heater element which is part of a heater control circuit, the supply of electricity to the heater elements being under the control of a thermostat sensing a temperature associated with the heater (for example the temperature in a said outer pathway) and/or a room thermostat and/or a time clock and/or an on-off switch.

Preferably, the storage heater comprises means for controlling the temperature of the heat storage core, such means not being under the control of the user, or else being under the coarse control of the user, enabling the user to select, for example, between a number of discrete settings, for example between a "normal" and a "superheat" setting. Preferably, such means comprises means for detecting a maximum normal operating temperature of the core, either directly or inferentially, and then terminating heating thereof on detection of said temperature; and similar means relating to a maximum "superheat" operating temperature of the core when such a "superheat" setting is available.There may be provided means for detecting a high temperature of the core, either directly or inferentially, indicative of abnormal operation, and for preventing further heating thereof on detection of said still higher temperature. Preferably, there are provided means for detecting a low temperature of the core, either directly or inferentially, to which temperature the core might fall during the period of normal rate electricity and for causing heating thereof, using normal rate electricity.

Proprietary thermostatic switches are available to perform these functions. The highest temperature switch is preferably a latching thermostatic switch.

Alternatively, for the highest temperature, fail-safe detection means could comprise a fusible link.

Preferably, the storage heater comprises means for providing the transfer of heat from the outer pathway to the outer wall of the storage heater which is relatively even, from top to bottom of the outer wall. Ordinarily, heat transfer would not be even because of the cooling of fluid which would take place as it passed along the outer pathway. This may be achieved by the provision of insulation on the inside surface of the outer wall, the insulation becoming thinner in the direction of flow, and preferably not being provided at the lower end of the outer pathway; and/or the heat insulation which substantially envelops the heat storage core and the inner pathway may vary in thickness, being thicker towards the top, so that heat conducted through this heat insulation is less towards the top than towards the bottom.Instead of using thicker/thinner insulation, insulation of higher/lower heat conductivity could be employed.

Although it is the intention to minimize the amount of heat conducted through the insulation and maximize the amount of heat carried by the heat transfer fluid, it will be appreciated that it will not be possible to eliminate the conducted heat altogether. As a result the lastmentioned method for providing a relatively even transfer of heat to the outer wall of the storage heater is desirable when means are present for providing a relatively even temperature distribution throughout the height of each outer wall when the damper is open and the heater is in heat output operation, so that the heat conducted through the heat insulation, when the damper is closed, does not cause the bottom of the outer walls to become substantially warmer than the top.

Preferably, the storage heater is of conventional shape, having two outer walls of large area. Suitably, an outer pathway is provided between the insulating medium and both such outer walls, suitably providing heat transfer to a large part of each outer wall.

The two outer walls of large area may be patterned, for example, fluted, or plain.

The invention will now be further described by way of example, with reference to the accompanying schematic drawings in which : Figure 1 is a cross section, in plan view, of a storage heater in accordance with the invention; Figure 2 is a cross section along the line A-A shown in Figure 1; Figure 3 is a cross section, in plan view, of a second embodiment of the invention; Figures 4 and 5 show further embodiments of the invention in vertical cross section; Figure 6 shows the mounting of a damper within a damper support member; Figures 7 and 8 are respective longitudinal and transverse cross sections through a damper; and Figures 9 and 10 show, in perspective and side view respectively, part of the core of a further embodiment of a storage heater.

The storage heater of Figures 1 and 2 comprises a heat storage core 2 and an insulating medium 4 enveloping it. A closed circuit for air within the storage heater comprises an inner pathway 6 within the heat storage core, the inner pathway 6 and core being bounded by heat insulation 4, and two outer pathways 8 between the heat insulation 4 and the flat, parallel outer walls 10 of the storage heater.

The heat storage core 2 comprises sixteen thin-walled stainless steel tubes 12, approximately 75mm in diameter, each containing an electrical heating element 14, namely an unsupported, coiled electrical resistance wire. Each tube further contains a heat storage medium constituted by relative coarse (approximately 8mm mean diameter) nonangular silica gravel and relatively fine (80Wm mean diameter) silica sand. The aggregate density of the heat storage medium is approximately 78% of the specific gravity of the material, the tubes having been filled by pouring in the coarse silica gravel first, then pouring in the silica sand.

The top and bottom of each tube may be stopped with an insulating plug or otherwise sealed.

The heat insulation in this embodiment is an amorphous silica insulation, available under the Trade Mark MYCROTHERM.

Air circulates in a closed circuit within the storage heater, the closed circuit being constituted by inner and outer pathways, those pathways communicating with one another at the top and bottom of the storage heater. At the top of the storage heater a damper schematically indicated as 16, described more fully later, is provided (Figure 2). The damper is located, and is of size, that it may engage right around the top of the heat insulation 4, thereby to control the circulation of the air. When raised it permits air to pass from the inner pathway to the outer pathway, and so circulate, at a rate dependent on the extent to which it has been raised.

In the embodiment of Figure 1 the tubes 12 are spaced from one another so that air rising within the first pathway 6 can collect heat from all around each tube. The embodiment of Figure 3 is similar to that of Figure 1, except that the tubes are welded together along their edges, to provide a more compact unit, albeit one with a slightly less efficient heat transfer within the core.

Further differences are that the external surfaces of the storage heater are fluted, whereby a plurality of narrow outer pathways are provided on each side of the storage heater, and that each electrical resistance wire is wound onto a flat, elongate former 17.

In the Figure 4 embodiment, the inner surface of each main outer wall of the storage heater carries layers 19 of fibrous silica/alumina insulation, having a layer lOmm thick at the top and 5mm thick in the middle region, but no insulation at the bottom. The purpose of these features is to ensure a relatively even temperature of each outer wall throughout its height when the air is circulating, despite the cooling of the air as it passes downwards between the layers of heat insulation and the outer walls.

The Figure 5 embodiment is similar to the Figure 4 embodiment except that the outer surface of each layer of heat insulation carries layers 20 of further fibrous silica/alumina heat insulation, having a layer lOmm thick at the bottom and 5mm thick in the middle region, but no insulation at the top. The embodiment of Figure 5 provides a relatively even heat distribution throughout the height of the outer walls, when the damper is open and the air is circulating, in the manner of the Figure 4 embodiment; and a more even distribution than the Figure 4 embodiment throughout the height of the outer walls, of heat which is conducted through the heat insulation layers when the damper is closed.

The damper 16 in each of the embodiments is mounted to a damper support member 30. The damper 16 and the damper support member form a damper unit which is removable from and locatable in the storace heater. The unit may be located in the storage heater by the provision of a ledge (not shown) within the storage heater on which the support member 30 rests. A top plate 30A may be located to close the top of the heater once the damper unit is in place. The support member 30 has a top wall 31 and a downwardly depending skirt comprised by respective side walls and end walls. The support member 30 is thus in the form of a hood, and within the hood, the damper 16 is movably located. The damper 16 is mounted to the underside of the top wall 31 by means of a pair of robust bi-metallic strips 32, 33.Each strip is rigidly mounted to the underside of the top wall 31, and is pivotally mounted at its other end to the damper 16. The bimetallic strip 32 is arranged to support one end of the damper 16, and the other bi-metallic strip 33 is arranged to support the other end of the damper. The outer surface of the support member 30 carries a heat insulating blanket 34, suitably of silica/alumina or fibreglass. The blanket 34 forms an insulating barrier within the upper part of the storage heater, whereby the top wall of the storage heater, indicated as 36 in Figure 4, does not become excessively hot to the touch even when hot air is circulating in the heater.

The damper itself is so constructed as to tolerate high temperatures and/or differential temperature effects, without degrading or distorting. The detailed construction is shown in Figures 7 and 8 but it should be noted that the through thickness of the damper is shown exaggeratedly large so that the various components can clearly be seen.The damper comprises the following components, described from top to bottom of the damper a compression plate 38 of a metallic material; a hood 39 of a metallic material having a top wall 40 and a downwardly depending skirt defined by a pa.r of longitudinal side walls 41 and a pair of end walls 42, the hood 39 being formed in three parts set in alignment with small gaps 43, 44 therebetween, these gaps serving as expansion joints; within the hood 39, three heat insulating layers 44; beneath the insulating layers, a support plate 46 of a metallic material, having a top wall and a downwardly depending skirt formed by a pair of longitudinal side walls and a pair of end walls, the skirt being wrapped in a heat insulating blanket, for example of silica/alumina or fibreglass; and a compression plate 48.

These parts are all secured together by three throughbolts 50, a respective bolt 50 passing through each component of the cover unit 39. Each bolt carries two star washers, one between the lower layer of insulation 45 and the support plate 46/blanket 47, and the other beneath the compression plate 48.

The mounting of the bolts 50 is such as to permit a certain degree of play, so that the components of the hood 39 can freely expand or contract. The parts of the damper which come into contact with the heat insulation 4 when the damper is closed, in order to stop air from passing from the inner pathway to the outer pathway, are indicated by the arrows B in Figures 7 and 8. Thus, the damper effectively provides a gasket formed by the insulating blanket and supported by the depending skirt provided by the support plate.

Each bi-metallic strip 32, 33 is wound with a heating element (not shown) in the form of a resistance wire. The heating elements may be arranged to be heated under the control of a time clock and/or thermostat, for example a room thermostat or thermostat associated with the storage heater, for example located in an outer pathway 8.

The operation of the damper will now be described.

When the heating elements are not powered the bimetallic strips are cold and thus straight. The damper is in its uppermost position and heat can escape from the inner pathway into the outer pathway. When the heater elements are switched on, they heat the bi-metallic strips which bend and lower the damper. Supply of electricity to the heater elements may be under the control of a radiator temperature thermostat located in one of the outer pathways 8. This thermostat can actuate a normally closed relay, so that when the thermostat operates, indicating a low temperature, the relay'opens, turning off the heater elements, so that the bi-metallic strips straighten and open the damper. A room thermostat and/or time clock and/or an ordinary switch can be placed in series with the radiator thermostat to give remote control.

When the damper opens the bi-metaltic strips will be heated to a certain extent by the hot air issuing from the inner pathway, although because of the insulation carried by the damper, they may not be heated substantially. The bi-metallic strips will however bend to an extent determined by the amount of heat which does pass to them, and thus tend to lower the damper once again. As the temperature in the core of the storage heater falls, the bi-metallic strips will tend to cool and straighten, so that the damper 16 is raised.

An advantage of arranging that the heater elements, when powered, cause the damper to close, is that in the event of a power cut, the bi-metallic strips will cool and straighten, lifting the damper, to allow the heat inside the storage heater to be used.

The core maximum temperature is controlled by a first core thermostat. Once the temperature of the core reaches a predetermined temperature for example 3500C, the core thermostat acts and causes termination of the supply of electricity to the core heater elements. Should the core temperature ever drop below a predetermined minimum temperature, for example 2000C, a second core thermostat acts and causes electricity to be supplied to the heater elements notwithstanding that cheap-rate electricity is not available.

In another preferred embodiment there is a similar arrangement but four temperature sensors are present in the core, the third being to switch off heating at "superheat" core temperature, for example 4000C, the user having the option of selecting 3500C (normal setting) or 4000C ("superheat" setting) as the maximum core temperature; and the fourth being a latching thermostat to terminate heating at a higher temperature, for example 4500C, indicative of abnormal operation, and to prevent further use of the heater until fault investigation and repair has been carried out.

Figures 9 and 10 show part of the core of a particularly preferred embodiment of the invention. In this embodiment, the core comprises twelve circularly cylindrical core rods 70, arranged as six units 72, each of two side-by-side core rods. Each unit 70 comprises a robust sheathed electrical core element 74, which extends from its first end 76, exposed beyond the lower end of one of the core rods 72, through that rod to the top end thereof, then down through the other rod, to be exposed beyond the lower end of that second rod, at its second end 78. The two exposed ends 76, 78 of the element 74, constitute terminals contacting with plated copper female contact pads 80, 82 at the base of the storage heater.

Each contact pad 80, 82 extends sufficiently to be contacted by the closer terminal of the adjacent core unit (e.g. pad 82 is contacted by the terminal 83 shown in dotted line in Figure 10). Beneath all of the contact pads is a layer of electrical insulation 84. It will be appreciated that by means of this arrangement a single serpentine current pathway is provided.

At the bottom of the unit 72, contacting a layer of heat insulation 85 at the bottom of both rods, is a steel plate 86 held in place by respective star washers 87 carried on the sheath of the element, adjacent respective ends thereof. The element is such that it provides useful heat only within the portion of each rod above the insulation layer 85.

Each rod 72 is constituted by four circularly cylindrical blocks 90 arranged end-to-end on the element.

The bottom three such blocks of each rod are identical with one another and each has a simple, narrow, axial, cylindrical bore 92 and is thereby engaged on the element, having been slid onto it before the securement of the plate 86. With the bottom three such blocks engaged on the element the uppermost part of the element constitutes an exposed loop or carrying handle 94, extending from one rod to another. On location of the uppermost block 96 of each rod, in end-to-end location with the next uppermost block, the loop or carrying handle 94 is covered, the respective uppermost block 96 having a slot 98 of width just greater than the diameter of the sheathed element, in a quadrant of the respective uppermost block.

The customer may thus purchase the storage heater as in a kit, comprising a lightweight body, damper unit, and (in this embodiment) six easily-lifted core units and twelve quadrant-slotted blocks 96, lifting each of the latter by means of the robust loop or carrying handle 94, which the element 74 provides when the uppermost blocks of the rods are absent. The customer may then locate the storage heater body in place and lower the six units into place, with the male contact members engaging in the contact pads at the base of the storage heater. The customer may then place the twelve quadrant-slotted blocks 96 of the rods in place at the top of the core units, to cover the looped parts of the elements. Finally, the top part of the storage heater, comprising the damper unit and a cover plate, may be located in place. The storage heater is then ready for use.

In this embodiment the material of the blocks is consolidated magnetite, available under the Trade Mark FEOLITE. The element has a coiled electrical resistance wire 99, of incallay within a robust, stainless steel tube. It is fabricated by a drawing process, in known manner.

The reader's attention is directed to all papers and documents which are filed concurrently with or previous to this specification and which are open to public inspection with this specification (including the priority document), and the contents of all such papers and documents are incorporated herein by reference.

All of the features disclosed in this specification (including any accompanying claims, abstract and drawings, , and/or all of the steps of any method or process so disclosed, may be combined in any combination, except combinations where at least some of such features and/or steps are mutually exclusive.

Each feature disclosed in this specification (including any accompanying claims, abstract and drawings), may be replaced by alternative features serving the same, equivalent or similar purpose, unless expressly stated otherwise. Thus, unless expressly stated otherwise, each feature disclosed is one example only of a generic series of equivalent or similar features.

The invention is not restricted to the details of the foregoing embodiment(s). The invention extends to any novel one, or any novel combination, of the features disclosed in this specification (including any accompanying claims, abstract and drawings), or to any novel one, or any novel combination, of the steps of any method or process so disclosed.

Claims (22)

1. A storage heater having an electrically heated heat storage core; an inner pathway, alongside or within the heat storage core, for passage of a heat transfer fluid; heat insulation substantially enveloping the heat storage core and the inner pathway; an outer pathway, between an outer wall of the storage heater and the heat insulation, for passage of the heat transfer fluid; wherein the inner and outer pathways form a substantially closed circuit for the heat transfer fluid; and means for controlling the circulation of the heat transfer fluid in the circuit.

2. A storage heater as claimed in Claim 1, wherein the heat storage core comprises a plurality of liftable heat storage core units, each comprising at least one heat storage block carried on a sheathed heating element.

3. A storage heater as claimed in Claim 2, wherein a said core unit comprises a lifting handle which is constituted by the sheathed heating element.

4. A storage heater as claimed in Claim 3, wherein a said core unit comprises two side-by-side heat storage rods each constituted by at least one block carried on the sheathed heating element, the sheathed heating element forming a loop extending between the rods, to thereby form the lifting handle.

5. A storage heater as claimed in Claim 3 or 4, wherein a said core unit comprises a heat storage block adapted to cover, at least partially, the handle, in use.

6. A storage heater as claimed in Claim 4, wherein each rod of a said core unit comprises a heat storage block adapted to cover a part of the handle, in use.

7. A storage heater as claimed in Claim 1, wherein the storage core comprises a fluent heat storage medium.

8. A storage heater as claimed in Claim 7, wherein the fluent heat storage medium is particulate and comprises at least two size grades such that interstices between the particles of the coarser grade may contain particles of the finer grade.

9. A storage heater as claimed in any preceding Claim, wherein the storage heater has two outer walls of large area and an outer pathway extends along each, whereby both walls are heat emitting in use.

10. A storage heater as claimed in any preceding Claim, wherein the means for controlling the circulation of the heat transfer fluid in the circuit comprises a damper arranged to vary the cross-sectional area at a point in the circuit.

11. A storage heater as claimed in Claim 10, wherein the damper is arranged to control the communication between the inner and outer pathways at their uppermost position.

12. A storage heater as claimed in any preceding Claim, wherein the means for controlling the circulation of the heat transfer fluid in the circuit is such as to be able to permit heat transfer fluid to circulate in the circuit in the event of electrical power failure.

13. A storage heater as claimed in Claim 10 or 11, wherein the damper is movably mounted to a damper support member of the heater by means of two bi-metallic strips which support respective ends of the damper.

14. A storage heater as claimed in Claim 13 wherein each bi-metallic strip is associated with a heater element which is part of a heater control circuit.

15. A storage heater as claimed in any preceding Claim, so constructed and/or adapted that the transfer of heat from an outer pathway to an outer wall of the storage heater is generally even from top to bottom of the outer wall.

16. A storage heater as claimed in Claim 15, wherein the generally even transfer of heat is achieved by providing non-uniform insulation in the outer pathway.

17. A kit for a storage heater as claimed in any preceding Claim, comprising a storage heater body, which is at least partly prewired, and separate core material or components.

18. A kit as claimed in Claim 17, when dependent upon Claims 1 to 6, comprising a storage heater body and a plurality of the said core units, the placement of the core units in the body completing the electrical wiring thereof.

19. A kit as claimed in Claim 18, wherein the wiring of the heater body is such that a terminal at the bottom of a heat storage rod engages an electrical contact at the bottom of the heater body which is also engaged by a terminal at the bottom of the adjacent heat storage rod of the adjacent core unit.

20. A core unit as claimed in any of Claims 2 to 6, per se.

21. A storage heater or kit therefor, substantially as hereinbefore described with reference to the accompanying drawings.

22. A core unit substantially as hereinbefore described with reference to the accompanying drawings.