GB2265211A

GB2265211A - A panel heater with a heating element embeded in a fire retardant matrix

Info

Publication number: GB2265211A
Application number: GB9305734A
Authority: GB
Inventors: Francis John Mcgorry
Original assignee: Individual
Current assignee: Individual
Priority date: 1992-03-20
Filing date: 1993-03-19
Publication date: 1993-09-22
Also published as: GB9305734D0

Abstract

A panel heater (1) comprises a slab shaped body member (2) formed by a shell (3) having a main heat exchange surface (5). A heating element (10) is embedded in a matrix (14) of fire retardant material within the shell (3). The matrix (14) may be a mix of sand, cement and polymers. An insulating panel (23) may be located within the shell (3) between the heating element (10) and the bottom surface (6). The element (10) may be an electric element with cables (19) delivering electrical power thereto. The heating element (10) and matrix (14) may be mounted within a sheet metal housing within the shell (3) and the shell may be made of a polyester resin reinforced with glass fibre. <IMAGE>

Description

"A panel heater" The present invention relates to a panel heater and in particular, though not limited to a panel heater in the form of a tile or slab for mounting on a wall, floor, ceiling or the like, and which is particularly suitable for forming part of the floor of a pig farrowing unit.

Under floor heating is commonly used for space heating, for example, heating a room of a house, office or the like, heating a pig farrowing unit and for other space heating purposes. Such underfloor heating, may comprise a floor slab, or a floor panel in which a water heat exchanger is embedded.

Generally, the water heat exchanger comprises a plurality of spaced apart parallel conduits located in the floor slab through which hot water is passed for heating the floor. Such underfloor heating suffers from major disadvantages, in particular, subsequent maintenance is particularly difficult and in many cases, almost impossible. For example, should a leak or other similar type fault develop in the heat exchanger, in general, it is necessary to excavate part or all of the floor slab to locate the damaged or faulty part of the heat exchanger. In many cases, to rectify a faulty heat exchanger, it is necessary to remove the entire heat exchanger from the floor slab for repair or replacement. Accordingly, significant portions if not the entire floor slab have to be excavated for replacing the heat exchanger.This, thus, subsequently requires the pouring of a fresh floor slab after the heat exchanger has being replaced or repaired. Heated panels within which an electrical heating element is located are also known for space heating In general, such panel heaters are of fibre glass material which is a relatively flammable material. Should a fault develop in the electrical heating element, or indeed, should the electrical heating element overheat, the fibre glass is likely to catch fire with serious consequences.

There is therefore a need for a panel heater suitable for space heating, which may be located on a floor, wall, ceiling or the like, and indeed, there is a need for a panel heater for other heating purposes.

The present invention is directed towards providing such a panel heater.

According to the invention there is provided a panel heater comprising a body member of slab like shape, the body member comprising a shell having an outer major surface forming a heat exchange surface for transferring heat from the body member, and a heating means mounted within the body member in the shell for heating the body member, the heating means being embedded in a layer formed by a matrix of fire retardant material.

Preferably, the material of the matrix is an electrically insulating material. Advantageously, the material of the matrix is of relatively high thermal capacity. Preferably, the material of the matrix is a mixture of sand, cement and a polymer.

In another embodiment of the invention, the polymer is an organic polymer.

In one embodiment of the invention the matrix is moulded within the shell.

In a further embodiment of the invention the heating means lies in a plane substantially parallel to the major surface of the body member, the heating means defining an area which is just less than the area of the heat exchange surface of the body member.

In one embodiment of the invention the heating means comprises an electrical heating element.

Advantageously, the heating element comprises an elongated resistance wire arranged in zig-zag formation and defining a plane substantially parallel to the major surface of the body member. Preferably, a plurality of spaced apart bollards are provided within the body member for supporting the heating element in zig-zag formation. Advantageously, the bollards are secured to the shell.

In one embodiment of the invention communicating means are provided through the shell for accommodating a power supply cable to the heating element.

Preferably, the communicating means extends through a minor surface of the body member.

In another embodiment of the invention an insulating panel of heat insulating material is located in the body member, the insulating panel being arranged so that the heating means lies between the insulating panel and the heat exchange surface. Preferably, the insulating panel is located within the shell and is spaced apart from the heating means. Advantageously, the insulating panel is substantially parallel to the heat exchange surface of the body member. Preferably, the area of the insulating panel is just less than the area of the heat exchange surface of the body member.

In a further embodiment of the invention the shell is of resin material. Preferably, the resin material is polyester resin. Advantageously, the resin material is reinforced. Preferably, the resin material is reinforced with a glass fibre mat.

In one embodiment of the invention the shell completely surrounds the body member, the heating means being completely encased by the shell.

In an alternative embodiment of the invention the heating means is mounted in a housing, the housing defining a hollow interior region for accommodating the heating means and the matrix, the housing being mounted in the body member within the shell.

Preferably, the housing is of sheet metal material.

Advantageously, the housing defines a pair of major surfaces, and the area of the respective major surfaces is just less than the area of the major surface of the body member.

In one embodiment of the invention the major surfaces of the housing are parallel to the heat exchange surface.

In another embodiment of the invention the communicating means extends through the housing for accommodating a power supply cable to the heating means In a preferred form the body member is in the form of a tile or slab.

The invention will be more clearly understood from the following description of some preferred embodiments thereof given by way of example only with reference to the accompanying drawings, in which: Fig. 1 is a perspective view of a panel heater according to the invention, Fig. 2 is a cut away perspective view of the panel heater of Fig. 1, Fig. 3 is a cut away cross-sectional perspective view of portion of the panel heater of Fig. 1, Fig. 4 is a perspective view of a mould for forming the panel heater of Fig. 1, Fig. 5 is a perspective view of the mould of Fig.

4 illustrating the panel heater being formed therein, Fig. 6 is a cross-sectional view of the mould of Fig. 4 illustrating the panel heater of Fig. 1 formed therein, Fig. 7 is a cut away perspective view similar to Fig. 2 of a panel heater according to another embodiment of the invention, and Fig. 8 is an exploded perspective view of a detail of the panel heater of Fig. 7.

Referring to the drawings and initially to Figs. 1 to 6 there is illustrated a panel heater according to the invention indicated generally by reference numeral 1.

The panel heater l is particularly suitable as a floor slab or tile, wall tile, or ceiling tile for space heating, and the panel heater l is particularly suitable for forming part or all of a floor of a pig farrowing unit. Needless to say, the panel heater 1 may also be used for other purposes, for example, under mattress heating, or the panel heater 1 may be placed resting on a floor for an individual to place their feet on for heating.

The panel heater 1 comprises a slab like body member 2 which is formed by a shell 3 of polyester resin material reinforced with glass fibre as will be described below. The shell 3 extends completely around the body member 2. The shell 3 forms a pair of opposite major surfaces of the body member 2, namely, a top surface 5 and a bottom surface 6 joined by a minor surface, namely, side surfaces 7 extending around the body member 2. The top major surface 5 forms a heat exchange surface from which heat is transferred from the body member 2 to a room or the like. A gel coat 9 as will be described below extends over the top major surface 5 and the minor side surfaces 7 to provide a top smooth wear resistant surface finish.

Heating means for heating the body member 2 comprises an electrical heating element 10 formed by an elongated electrical resistance wire 11 of 0.5 mm diameter and of 10.2 ohms resistance per meter arranged in zig-zag formation and embedded in a matrix 14 in the shell 3. The resistance wire 11 is electrically insulated by an insulating sleeve (not shown) and is supported in zig-zag formation on bollards 15 which are secured to the shell 3 as will be described below. The heating element 10 lies in a plane which is substantially parallel to the top heat exchange surface 5 and is spaced apart therefrom and defines an area, which is just less than the area of the top surface 5. In this embodiment of the invention the heating element is suitable for powering by a 220 volt, 50 Hz AC mains supply. When connected to such a mains supply, the heating element delivers 215 watts.The matrix 14 is of a fire retardant material to prevent burning of the body member 2 in the event of a fault in the heating element 10. In this case, the matrix 14 comprises a mixture of sand, cement and polymers. As well as having fire retardant properties, the matrix 14 is also electrically insulating, and has a relatively high thermal capacity.

Communicating means comprising a grommet 18 extends through the shell 3 for accommodating power supply cables 19 to the heating element 10. Switch means comprising a thermostatically controlled switch 20 is embedded in the matrix 14 and is responsive to the temperature of the body member 2, and switches one of the cables 19 to avoid overheating of the body member 2. Such thermostatically controlled switches will be well known to those skilled in the aft.

An insulating panel 23 of heat insulating material, namely, expanded polyurethane material is located in the body member 2 within the shell 3 for reducing the passage of heat from the heating element 10 to the bottom surface 6 so that more heat is available for heat transfer from the top surface 5. The insulating panel 23 is spaced apart from the bottom surface 6, and is also spaced apart from the heating element 10 and is arranged so that the heating element 10 lies between the top surface 5 and the insulating panel 23.

Portion 25 of the shell 3 extends between the insulating panel 23 and the matrix 14. The insulating panel 23 lies in a plane parallel to the top and bottom surfaces 5 and 6 and is of area just less than the top surface 5.

In use, the panel heater 1 is mounted on a floor, wall or ceiling with the bottom surface 6 abutting the floor, wall or ceiling. The panel heater I may rest on the floor, ox may be secured by suitable adhesive, grouting or the like. Needless to say, where the panel heater 1 is secured to the wall or a ceiling, in general, it would be secured by a suitable adhesive or grouting. Alternatively, the panel heater 1 may be mounted on a floor, wall or ceiling using suitable mounting brackets. The panel heater 1 may be surface mounted, or recessed as desired. The top heat exchange surface 5 is exposed to the room so that heat from the heating element 10 is transferred through the heat exchange surface 5 to the room.Where the panel heater 1 is used in the floor of a pig farrowing unit, it is envisaged that it will be recessed into the floor, for example, into a slatted floor and the top heat exchange surface 5 will coincide and be aligned with the top surface of the slatted floor of the farrowing unit. The cables 19 are connected to a suitable electrical 220 volts, 50 Hz AC mains supply.

It is envisaged in certain cases that a plurality of panel heaters 1 according to the invention abutting each others minor side surface 7 may be provided. In which case, suitable cables would be provided extending between the panel heaters 1 for connecting the panel heaters 1 to a suitable power supply source.

It is also envisaged that a floor, wall or ceiling may be tiled with a mix of the panel heaters 1 in the form of tiles and other non-heated tiles, in which case the panel heater tiles would, in general, be interspersed between the other non-heated tiles.

In general, where the panel heater 1 is for use in a pig farrowing or rearing unit, it is envisaged that the heating element 10 will be chosen to provide a surf ace temperature of approximately 350C on the top heat exchange surface 5. Needless to say, the heating element 10 may be chosen to provide a temperature of the top heat exchange surface 5 of any desired temperature, however, in general, it is envisaged that the maximum operating temperature of the top heat exchange surface 5 would not exceed 400C.

Indeed, the panel heater 1 may be put to many other uses besides tiling a floor, wall, ceiling or the like. The panel heater 1 may be used for forming a floor, wall, ceiling or the like of an incubator, and as mentioned above, may form portion of the floor of a pig rearing and/or pig farrowing unit.

Returning now to Figs. 4 to 6 the construction of the panel heater 1 will be described. The panel heater 1 is moulded in a mould 30 which comprises a base 31 and side and end walls 32 and 33, respectively, extending upwardly from the base 31. An inner surface 34 of the base 31 and side and end walls 32 and 33 defines a hollow interior region 35 which defines the panel heater 1. The inner surface 34 of the base 31 forms the top heat exchange surface 5 of the panel heater 1, while the inner surface 34 of the side and end walls 32 and 33 forms the minor side surfaces 7 of the panel heater 1. An opening 36 in one of the side walls 32 locates the grommet 18 which extends through the shell 3 during casting of the panel heater 1.

The panel heater 1 is formed in the mould 30 as follows. With the grommet 18 located in the opening 36 and extending into the hollow interior region 35 of the mould 30 a layer 40 of polyester resin gel coating is brushed onto the inner surface 34 of the base 31 and side and end walls 32 and 33 of the mould 30 to a depth of approximately 1 mm to form the gel coat 9.

The gel coat layer 40 is allowed to dry. A mat 41 of glass fibre material is placed over the dry gel coat layer 40 and extends upwardly adjacent the portions of the gel coat layer 40 forming the side surfaces 7 of the panel heater 1. A layer 42 of polyester resin is applied with a roller over the mat 41 to a depth of approximately 3 mm and is allowed to cure to a relatively tacky state. The bollards 15 are then pressed onto the layer 42 at the appropriate locations to support the resistance wire 11 of the heating element 10 in zig-zag formation. The layer 42 is then allowed to cure thereby securing the bollards 15 to the layer 42. The resistance wire 11 is passed around the bollards 15 in zig-zag formation as illustrated in Fig. 5.The thermostatically controlled switch 20 is placed on the layer 42 adjacent the grommet 18 and one end of the resistance wire is connected to one terminal (not shown) of the switch 20. The cables 19 are passed through the grommet 18, and one of the cables 19 is secured to the other terminal (not shown) of the switch 20, while the other of the cables 19 is secured by a crimp connector (not shown) to the other end of the resistance wire 11. When passing the resistance wires 11 around the bollards 15 the resistance wire 11 is located on the bollards 15 approximately half way between the ends of the bollards 15 so that the resistance wire 11 is spaced apart from the portion of the shell 3 forming the top surface 5 and the portion 25 of the shell 3 intermediate the insulating panel 23 and the matrix 14.The matrix 14 of sand, cement and polymers is mixed and poured into the portion of the shell formed by the layer 42. The matrix 14 is poured to a depth of approximately 10 mm, and the matrix 14 is allowed to cure. In this way the minimum depth of matrix material 1 between the resistance wire 11 and the polyester resin shell 3 is at least 3 mm. The bollards 15 are arranged so that the minimum thickness of matrix material ld between the resistance wire 11 and the polyester shell 3 is not less than 10 mm extending in a sideward and endward direction. A mat 43 of glass fibre is placed over the cured matrix 14.

A layer 44 of polyester resin is rolled over the mat 43 to a depth of approximately 3 mm to form the portion 25 of the shell 3. While the layer 44 is still wet the insulating panel 23 is centrally located and placed on the layer 44 of polyester resin. Any voids between the insulating panel 23 and the portions of the layer 44 which form the side surfaces 7 are filled with polyester resin. A mat 46 of glass fibre material is placed over the insulating panel 23, and a further layer 47 of polyester resin is applied with a roller over the mat 46 and the insulating panel 23 to a depth of approximately 3 mm.

The mould 30 is placed on a level surface and the polyester resin is allowed to cure. The surface of the layer 47 forms the bottom surface 6 of the panel heater 1.

In certain cases, the mould 14 may be placed on a vibrating table and vibrated to ensure that the bottom surface 6 formed by the layer 47 is level and relatively smooth.

In this embodiment of the invention the matrix is formed by a sand, cement and polymers mix which is sold under the trade name Larcem 200 which is manufactured and sold by the Larcem group of Belfast, Northern Ireland. The manufacturers instructions are followed in the preparation, pouring and curing of the matrix 14.

Referring now to Figs. 7 and 8, there is illustrated a panel heater 50 according to another embodiment of the invention. The panel heater 50 is substantially similar to the panel heater 1 and similar components are identified by the same reference numeral. The main difference between the panel heater 50 and the panel heater 1 is that the heating element 10 and the matrix 14 are encased in a housing 51 of the sheet metal material. The housing 51 comprises a base 52 and side and end walls 53 and 54 extending upwardly from the base 52 and defining with the base 52 a hollow interior region 55. A lid 56 also of sheet metal material having a downwardly extending lip 57 which extends around the periphery thereof closes the hollow interior region 55 of the housing 51. The lid 56 is secured to the side and end walls 53 and 54 by spot welding the lip 57 to side and end walls 53 and 54.The bollards 15 are located within the hollow interior region 55 and are secured to the base 52 by rivets or other suitable securing means. An opening 58 in one of the side walls 53 engages the grommet 18 for accommodating the cables 19 into the hollow interior region 55 to the heating element 10. The thermostatically controlled switch 20 is mounted within the hollow interior region 55 and is connected to one end of the resistance wire 11 and to one of the cables 19 in similar fashion as in the case of the panel heater 1. The housing 51 is located within a shell 3 of the body member 2 intermediate the top heat exchange surface 5 and the insulating panel 23 and is spaced apart from and parallel to both. The major area of the housing 51 is just less than the area of the top heat exchanger surface 5.

The construction of the panel heater 50 is substantially similar to the construction of the panel heater 1 with the exception that the housing 51 with the heating element 10 and matrix 14 therein is first assembled. With the bollards 15 secured in the desired locations to the base 52, the resistance wire 11 is passed around the bollards 15 half way between their ends so that the resistance wire 11 is spaced apart from the base 52 and the lid 56. Needless to say, the resistance wire 11 is also spaced apart from the side and end walls 53 and 54. The thermostatically controlled switch 20 is placed in the housing 51 and is connected to one end of the resistance wire 11 and to one of the cables 19. The other cable 19 is connected to the other end of the resistance wire 11.The matrix of sand, cement and polymers is mixed and poured into the hollow interior region 55 of the housing 51 and allowed to cure. The lid 56 is placed over the side and end walls 53 and 54 and secured by spot welding the lip 57 to the side and end walls 53 and 54.

The panel heater 50 is formed in a mould similar to the mould 30, and while the layer 42 is still wet, the assembled housing 51 is placed on the layer 42 with the base 52 resting on the layer 42. As the housing is being placed on the layer 42 the cables 19 are passed through the grommet 18 and the grommet 18 is aligned with and inserted into the opening 58 in the housing 51. The housing 51 is centrally located on the layer 42, and voids between the housing 51 and the portion of the layer 42 which extends up the side and end walls 32 and 33 of the mould 30 are filled with polyester resin which is allowed to partly cure. The mat 43 is placed over the housing 51, and the next layer 44 of polyester resin is then applied with a roller to a depth of 3 mm as described with reference to the panel heater 1. The remainder of the construction of the panel heater 50 is identical to that of the panel heater 1.

Use of the panel heater 50 is similar to that of the panel heater 1.

While the panel heaters have been described as comprising an insulating panel of heat insulating material, in certain cases, it is envisaged that the insulating panel may be dispensed with.

While the heating means has been described as comprising an electrically powered heating element, in certain cases, it is envisaged that other types of heating means may be provided, and where the heating means is provided by an electrical heating element, other suitable arrangements of electrical heating elements may be used besides a resistance wire arranged in zig-zag formation. While the heating element has been described as being suitable for powering by a 220 volt 50 Hz power supply, the heating element may be suitable for powering by a power supply of any desired voltage, frequency, and indeed, in certain cases, it is envisaged that the heating element may be suitable for powering by a direct current supply.In certain cases, it is envisaged that the heating element may be suitable for powering by a relatively low voltage power supply, either AC or DC for safety purposes, for example a 24 volt power supply or less.

While the material of the shell of the body member of the panel heaters has been described as being polyester resin material reinforced with glass fibre matting, the shell may be of any other suitable material. It is also envisaged that the matrix may be of any other suitable fire retardant material, and may or may not have relatively high thermal capacity, and may or may not be of an electrically insulating material. It is envisaged that where the matrix comprises a mixture of sand, cement and polymers, the polymers may be organic polymers. Indeed, in certain cases, the polymers may be omitted, and in which cases the matrix would be of sand and cement only. While the layers of polyester resin forming the shell have been described as being of specific thicknesses, the layers of resin may be of any desired thickness, and will largely depend on the overall size of the panel heater.Additionally, the matrix may be of any suitable or desired depth. However, it is important that it should be of sufficient depth that the electrical resistance wires 11 are completely surrounded and encased in the matrix material. It is preferable that the minimum thickness or depth of matrix material surrounding the electrical resistance wire and between the electrical resistance wire and the shell should not be less than 3 mm, and, and preferably, should not be less than 4 mm. It is preferable that the depth of the matrix material should not be less than 8 mm, and preferably, should be approximately 10 mm.

It is also envisaged that the matrix of sand and cement, or sand, cement and polymers may be precast with the heating element encased therein, and the precast matrix would then be placed in the shell during construction of the shell, in similar fashion as the housing is placed in the shell.

While the resistance wire has been described as being of a particular diameter and resistance value, the resistance wire may be of any other suitable diameter, and resistance value. The diameter of the wire and its resistance value will largely depend on the power output required from the panel heater, the length of the wire, and the type of power supply source to which the panel heater is to be connected. However, it is important that the depth of the matrix material, and the arrangement of the bollards should be chosen bearing in mind the diameter of the electrical resistance wire, and the minimum depth or thickness of matrix material discussed above which should surround the resistance wire.

While a particular shape and construction of panel heater has been described, the panel heater may be of any other suitable desired shape and construction.

Needless to say, the panel heater may be formed by other methods besides that described.

Claims

1. A panel heater comprising a body member of slab like shape, the body member comprising a shell having an outer major surface forming a heat exchange surface for transferring heat from the body member, and a heating means mounted within the body member in the shell for heating the body member, the heating means being embedded in a layer formed by a matrix of fire retardant material.

2. A panel heater as claimed in Claim 1 in which the material of the matrix is an electrically insulating material.

3. A panel heater as claimed in Claim 1 or 2 in which the material of the matrix is of relatively high thermal capacity.

4. A panel heater as claimed in any preceding claim in which the material of the matrix is a mixture of sand, cement and a polymer.

5. A panel heater as claimed in Claim 4 in which the polymer is an organic polymer.

6. A panel heater as claimed in any preceding claim in which the matrix is moulded within the shell.

7. A panel heater as claimed in any preceding claim in which the heating means lies in a plane substantially parallel to the major surface of the body member, the heating means defining an area which is just less than the area of the heat exchange surface of the body member.

8. A panel heater as claimed in any preceding claim in which the heating means comprises an electrical heating element.

9. A panel heater as claimed in Claim 8 in which the heating element comprises an elongated resistance wire arranged in zig-zag formation and defining a plane substantially parallel to the major surface of the body member.

10. A panel heater as claimed in Claim 9 in which a plurality of spaced apart bollards are provided within the body member for supporting the heating element in zig-zag formation.

11. A panel heater as claimed in Claim 10 in which the bollards are secured to the shell.

12. A panel heater as claimed in any of Claims 8 to 11 in which communicating means are provided through the shell for accommodating a power supply cable to the heating element.

13. A panel heater as claimed in Claim 12 in which the communicating means extends through a minor surface of the body member.

14. A panel heater as claimed in any preceding claim in which an insulating panel of heat insulating material is located in the body member, the insulating panel being arranged so that the heating means lies between the insulating panel and the heat exchange surface.

15. A panel heater as claimed in Claim 14 in which the insulating panel is located within the shell and is spaced apart from the heating means.

16. A panel heater as claimed in Claim 14 or 15 in which the insulating panel is substantially parallel to the heat exchange surface of the body member.

17. A panel heater as claimed in any of Claims 14 to 16 in which the area of the insulating panel is just less than the area of the heat exchange surface of the body member.

18. A panel heater as claimed in any preceding claim in which the shell is of resin material.

19. A panel heater as claimed in Claim 18 in which the resin material is polyester resin.

20. A panel heater as claimed in Claim 18 or 19 in which the resin material is reinforced.

21. A panel heater as claimed in Claim 20 in which the resin material is reinforced with a glass fibre mat.

22. A panel heater as claimed in any preceding claim in which the shell completely surrounds the body member, the heating means being completely encased by the shell.

23. A panel heater as claimed in any preceding claim in which the heating means is mounted in a housing, the housing defining a hollow interior region for accommodating the heating means and the matrix, the housing being mounted in the body member within the shell.

24. A panel heater as claimed in Claim 23 in which the housing is of sheet metal material.

25. A panel heater as claimed in Claim 23 or 24 in which the housing defines a pair of major surfaces, and the area of the respective major surfaces is just less than the area of the major surface of the body member.

26. A panel heater as claimed in Claim 25 in which the major surfaces of the housing are parallel to the heat exchange surface.

27. A panel heater as claimed in any of Claims 23 to 26 in which the communicating means extends through the housing for accommodating a power supply cable to the heating means.

28. A panel heater as claimed in any preceding claim in which the body member is in the form of a tile or slab.

29. A panel heater substantially as described herein with reference to and as illustrated in Figs. 1 to 6 of the accompanying drawings.

30. A panel heater substantially as described herein with reference to and as illustrated in Figs. 7 and 8 of the accompanying drawings.