GB2503925A - A firebox assembly for an efficient, wide, gas fireplace; with a recessed burner assembly, multiple baffles and an exhaust hood which can be fitted in situ - Google Patents

Abstract

An open front firebox 101 has a base; a top; a burner assembly (fig 6, 120) below; a hood 154 above; and a baffle assembly 168. The firebox is used in a gas fire having a width greater than 750mm and a net heat input under 7kW. The top of the firebox slopes downwards from the front to the rear. The burner assembly is located toward the rear of the firebox, where the base is raised. It comprises a burner tray with air gaps; a venturi; a burner pad (fig 5, 124) with a metal enclosure (fig 5, 134); an insulation pad; a fuel tray; and a burner box (fig 6, 122) housing controls and batteries. The pad is rectangular and has two rows of slots (fig 5, 132), one row having fewer slots, the two nearest the corners being removed. The hood has an inlet and a smaller outlet; it is installed through the open front of the firebox into an opening in the top after the firebox is fitted in an enclosure, which may be within a wall. The baffle assembly is fitted over the hood inlet and consists of two angled baffles 170.

Description

AGASFIRE

The invention relates to a gas fire, and particularly, but not exclusively to a wide open-fronted gas fire with improved efficiency.

There is a continuing desire to improve the efficiency of gas fires, both for economic and environmental reasons. Various approaches to improving efficiency are known, but many of these have associated drawbacks. For example, it is known to provide a glass panel across the front of the fire in front of the fuel bed, to reduce the amount of warm air from the room that is drawn into the fire during operation. One major drawback of this approach is that the aesthetics of the fire are severely compromised, and the fire loses its real fire' appearance.

Numerous different fire designs are available on the market today to cater for the different tastes and desires of customers. One popular design is referred to as hole-in-the-wall', letterbox' or slot-in' fires. These fifes do not fit into standard fireplace openings, but require a purpose made enclosure to be formed, typically of a width that is far greater than a standard fireplace. Within this sector, glass fronted fires dominate because of the problems associated with achieving any sort of efficiency with such a wide fireplace opening. While some open-fronted fifes are produced, efficiency levels are so low that they are seen as purely decorative features. These so-called Decorative Fires' would only be recognised as providing a 25% level of efficiency, and so cannot be regarded as heating appliances. The 25% efficiency rating comes from the SAP rating, as covered in the JfK government's. Standard Assessment Procedure for the Energy Rating of Dwellings.

Other types of open fronted fires can provide far higher efficiencies. Efficiencies up to 50% will have no efficiency classification, but Some open fronted fires can obtain efficiencies of between 50% and 70% (Class 2 efficiency) and, in some cases, even in excess of 70% (Class I efficiency). However, Class 1 efficiencies have typically only been achieved with wider letterbox style fires through the incorporation of a glass. -As such, a customer has to choose between the more realistic aesthetics of an open-fronted fire and the greater efficiency and heating capability of a glass fronted fife.

The present invention seeks to address this problem by providing a wide open-fronted fire with greatly improved efficiency, and ideally with an efficiency level close to that obtainable from glass-fronted alternatives.

Since letterbox style fires are likely to be chosen as a focal point of a room, the possibility of maintaining optimum aesthetics while also achieving a good level of efficiency and heat output from a fire of this type is highly desirable.

According to the present invention there is provided a gas fire according to the appended claim 1. The use of a hood improves the fire's ability to clear combustion products from the firebox, and. thereby allows more efficient operation. Firebox' is the term used to describe the chamberlenclosure where the combustion process takes place. In use, the firebox may be received in an enclosure formed in a building wall, or in am enclosure formed proud of a building wall, for example in a false chimney breast formed against an existing building wall.

This latter option would be of assistance where no chimney currently exists so a false chimney breast is constructed and the flue system is run up through the house.

Additional preferred features of the invention are recited in the associated dependent claims.

Preferably, a part of the top of the firebox is angled downwards from the open front towards the rear of the firebox, and/or the burner assembly is raised up and located towards the rear of the firebox. This reduces the effective height of the front opening of the firebox and assists in preventing the combustion products from spilling out of the front of the fire.

A small (e.g. 20-30mm high) ridge, for example formed of folded metal, or a strip of glass may be provided at the base of the firebox between the burner assembly and the front of the firebox to prevent fuel bed pieces falling out of the fire. Where a strip of glass is used, it could be made taller than the ridge, perhaps 30-50mm high or taller, to further reduce the firebox opening height, and thus further improve spillage performance and efficiency of the fire, without impeding the view of the fuel bed.

The burner assembly may comprise a burner tray with air gaps to allow air to flow around components of the burner assembly such as a burner/venturi, a burner pad and/or an insulation pad to: pre-heat air entering the fife. The burner assembly may further comprise a fuel tray through which air flows when entering the burner assembly, to further pre-heat the air.

Sides of the burner pad may be enclosed by metal strips to prevent or minimise leakage of fuel and air through the burner pad. Flame slots provided in the burner pad are preferably arranged so that no flames project at the front corners of the burner, where they would have low inertia.

For example, two rows of flame slots could be provided, with one row comprising fewer flame slots than the other such that no flame slots are provided adjacent to two corners of the burner The burner assembly may be housed together with controls and batteries for the fife in a burner box to avoid the need for separate housings and to simplif' installation of the fire.

The hood may be received through the open front of the firebox and installed in an opening formed in the top of the firebox, preferably after the firebox has been installed. The hood is preferably also removable in the same manner. This simplifies installation and servicing The hood may comprise an inlet, located adjacent to the top of the firebox, and an outlet which is smaller than the inlet, and located outside the firebox. Two end walls of the hood are preferably angled towards each other as they extend away from the inlet. The internal angle of each end wall is preferably between 500 and 600, for example 57°. The outlet of the hood is preferably located at the top of the hood in a wall of the hood which, in use, faces away from the front of the firebox to help prevent debris from falling into the firebox, and help to generate thermal lift.

The outlet is preferably angled and positioned forward of a rear wall of the firebox to provide a gap of at least 50mm between the outlet and the rear wall of an enclosure in which the fire is located. This protects against the outlet becoming blocked by debris.

The fire may ftirther comprise a baffle assembly, preferably formed as a separate unitary component, fitted in the firebox over the inlet of the hood. The baffle assembly preferably comprises two angled baffles. By forming the baffle assembly as a separate component it can be removed separately from the hood and applied in other configurations of the fire, for example if the hood were replaced with a canopy for connection to a flexible flue/liner.

The fire may further comprise liner panels within the firebox. The liner panels may be made of sheet metal or ceramic fibre or similar, and may be painted with a high temperature paint or finished in vitreous enamel material.

At least some of the liner panels may be received in channels provided within the firebox, and may be installed after all other installation requirements such as the hood and burner assembly.

This reduces the risk of damage to the liner panels. The baffle assembly may help to retain the liner panels in place within the firebox.

A further aspect of the present invention provides an open-fronted gas fire according to the appended claim 25. The fire may comprise any of the features referred to above. Open-fronted fires wider than around 750mm typically require a heat input well in excess of 7kW, and this has numerous disadvantages. I,

Most homes have so-called advantageous ventilation, essentially air gaps. For fires with up to 7kW net heat input, this advantageous ventilation typically provides sufficient air to ensure a gas fife burning within a chimney will clear its products of combustion into the flue. In other words, because of sufficient aft supply from the natural ventilation of the building, the combustion products pass up the chimney rather than spill into the room.

For fifes above 7kW net heat input, it is accepted that there is generally not sufficient natural ventilation in the property. Indeed, it is a requirement in some countries that any fire with a net heat input of greater than 7kW requires additional ventilation, for example in the form of an aft brick, to be provided.

In terms of efficiency, there is little point designing an efficient fife if it requires additional ventilation to be provided, since the additional aft drawn into the room from outside will lower the overall temperature and, thus, reduce the efficiency of the heating and increase running costs.

Furthermore, a fire with over 7kW net heat input will produce more products, and draw more air in through the additional ventilation, so typically needs a larger Class I chimney (minimum flue size of 7" (180mm) diameter or a standard 9" by 9" brick built chinmey) to allow them to clear the products of combustion. Typically, Class 1 chimneys are found only in older properties, with smaller Class 2 chimneys or flues (5" (130mm) diameter flue) now being the norm. By keeping the net heat input under 7kw, smaller, Class 2, chimneys will generally be sufficient to clear the combustion products from the fire.

The fire of the present invention has a front opening with a width of around 775mm, and a height of around 325mm. The size of the opening results in a lot of cold air entering the front of the firebox, and reducing the thermal lift generated by the flames of the fife. Previous fires of this type and size have countered this problem by using a relatively high net heat input, e.g. 8.2kw, to increase the inertia of, and thermal lift generated by, the flames. The new design had to ensure that the fire would still develop sufficient thermal lift to ensure it cleared its products of combustion within five minutes of lighting even when the net heat input was reduced to below 7 kW. The applicant is not aware of this having ever been achieved with an open fronted fire of this width/size. However, the fire of the present invention was able to meet the spillage requirements outlined above even when operating with a Class 2 chimney and a net heat input of 6.85Kw for a Natural Gas fuel supply. This low heat input avoids the need for additional ventilation, thus improving the potential efficiency of the fire.

The higher efficiency of the fire means that more heat can be provided at lower settings. This, combined with a lower heat input, reduces emissions from the fire.

The ability of the fire to operate with a Class 2 chimney was essential to achieving a verified efficiency rating. A first step in the standard assessment of a fife's efficiency is to operate the fife with a 5" (130mm) diameter flue, equivalent to a Class 2 flue/chimney, and then gradually restrict the flue to determine the point at which the combustion products start spilling into the room rather than clearing up the flue. This means that the products of combustion plus all the secondary air that could be drawn from the room by the fire must pass up the 5" (130mm) flue.

Decorative wide fronted fifes, with theft high heat input, will generally not clear their products when connected to a 5" (130mm) diameter flue. As such, it is not possible to asses and rate their efficiencies using the standard tests.

The invention thus provides a wide open-fronted fire to achieve levels of efficiency closer to those achievable by glass-fronted fires which, although inherently more efficient, have a number of drawbacks which make them less attractive to customers than open-fronted fires.

With glass-fronted fires a space has to bc left between the back of the plaster boarded wall and the glass panel of the fife to allow for the glass panel to be fittedlremoved. A gap also needs to be provided to ensure the fire has space enough to allow products of combustion to exhaust the fire and spill safely in blocked flue conditions. This is achieved by allowing a gap of around 50mm which allows the fires draft diverter to perform. The presence of a glass panel tends to distance the flames and fuel bed and this is worsened by the 50mm gap. As such, the flames of a glass-frontód fire can appear to be a long way from the front of the fire. The flames of a glass-fronted fife can be positioned relatively close to the glass to minimise this effect, but a space is still required to avoid marking of the glass panel, In contrast, the flames of an open-fronted fire will appear to be closer to the front of the fire, for greater aesthetic appeal, even if the fuel bed is actually located further back in the firebox.

As well as distancing the flames from the front of the fire, the required 50mm gap also reduces the maximum depth of a fuel bed for a given depth of fire. The construction of many homes means that the depth available for the installation of inset fires is limited. This effectively places an upper limit on the depth of the fire, which in turn limits important aspects like fuel bed depth.

The glass of a glass fronted fire contains the heat and allows the fire to operate efficiently, but reduces radiant heat output. To compensate for the loss of radiant heat output, glass fronted fires typically have to provide a convection aft gap around the outside surfaces of the firebox to provide greater convective heat output. This further reduces the effective fuel bed depth for a given fire/enclosure depth.

With the fire of the present invention, high levels of net efficiency (around 62.4%) have been achieved without the need for a convection air gap to be provided. This results in greater fuel bed depth for a given enclosure depth. The result is a larger amount of heat output, and a far greatet sensation of heat because there is no glass panel blocking the radiant heai output.

It is known that flue problems can become only apparent after the fire has been fitted. Since glass-fronted fires must be built-in, this presents a major problem. If, after installation, the fire has to be removed for any reason, the builder would have to deconstruct the builder's opening.

The fire of the present invention can be completely removed if necessary to correct any flue issues without causing damage to the builder's enclosure.

A better understanding of the present invention will be obtained from the following detailed description of a preferred embodiment thereof The description is given by way of example only and makes reference to the accompanying drawings in which: Figure 1 is a perspective view of a firebox from a known letterbox style fire; Figure 2 is a perspective view of the firebox from a fire according to the present invention; Figure 3 is a side view of the firebox of Figure 2; Figure 4 is a side view of a burner assembly from a fire according to the present invention; Figure 5 is a perspective view of a burner pad from a fife according to the present.

invention; Figures 6 and 6a are side views of a hood installed in a fire according to the present invention; Figure 7 is a perspective view of a front view of the hood shown in Figures 6 and 6a; Figures 8 and 8a are side views of a baffle assembly installed in a fire according to the present invention; Figure 9 is a side view of a restrictor installed in a fire according to the present invention; and Figure 10 is a side view of a canopy installed in a fire according to the present invention.

Figure 1 shows an example of a typical firebox for a wide (approximately 780mm) letterbox' style gas* fire. The term firebox' is used by the Industry to describe the chamber/enclosure where the combustion process takes place, where the flames bum, products exhaust, and from where the Fuel Bed emits heat.

The known firebox 1 of Figure 1 is essentially a rectangular box which is open at the front. The side walls 2,4 are essentially parallel, as are the top 6 and base 8. The top 6 of firebox I is almost entirely removed to provide an opernng 10 to allow combustionproducts out of the fife, and a further opening 12 is provided in the base of the firebox I to receive a recessed burner assembly.

The firebox is designed to be pushed or slid into a purpose made builder's opening/enclosure, typically raised off the floor to a minimum of 250mm.

Figures 2 and 3 show the firebox 101 of the present invention.

Similarly to the firebox 1 shown in Figure 1, the firebox 101 of the present invention has solid back and side walls 102,104, and an open front. In contrast to the known firebox 1 of Figure 1, a part of the top 106 of the firebox 101 is angled downwards towards the rear of the firebox 101 to reduce Ui effective height of the firebox, and to lower the position of the top opening 110.

A more steeply angled part 114 is included within the firebox 101 to increase the internal angle, as better seen in the end view of Figure 3.

The firebox base 108 is also gradually angled upward towards the rear of the firebox 101 such that an installed burner will sit around 12mm higher within the firebox 101 when received in the opening 112, placing it closer to the products outlet. The burner opening 112 is also positioned further back in the firebox 101 than the equivalent opening 12 in the known firebox 1 ofFigure I. Insulating liner panels 105,107 are included inside the firebox 101 to provide insulation for the firebox 101 and improve thermal lift of the fire. The use of liner panels, made of ceramic fibre -10-board or treated sheet steel with flanges to provide an insulating air gap or equivalent insulated materials to protect the metal firebox, is known. However, the liner panels have traditionally been glued into position within a firebox I, or held in place mechanically, e.g. using brackets.

With the present design, the more steeply angled part 114 of the firebox top 106 and the raised part of the flirebox base 108 have been stopped short of the sides 102,104 to provide side channels that will accept and locate the side liner panels 105. The rear liner panel 107, located against a rear wall of the firebox 101, is retained in place by the side liner panels 105, which can be easily slid in or out of the side channels if they need to be changed or replaced. The side liner panels 105 of the present invention are made of sheet metal and painted in a high temperature paint. The rear liner panel 107 tends to experience higher temperatures (being closer to the fuel bed) so is made of ceramic fibre or a similar insulating material.

The liner panels for fires of this type come in different finishes, for example plain black, buff, or realistic brick effects, and can be quite expensive. The liner panels are easily marked either during installation or servicing causing visually unacceptable damage. The fife of the present invention provides for easy fitting and/or changing of the liner panels 105,107, meaning that the potential for damage is minimised.

The end view of Figure 3 again shows the various features mentioned above, with the internal parts of the firebox shown in broken lines. In addition to the incorporation of angles in the top 106 and base 108 of the firebox 101, the overall height 118 of the firebox 101 was reduced by 12mm.

The various features described above serve to minimise the area of the firebo* 101 which is open to room air, and to locate the fuel bed and burner further back in the firebox 101 and * closer to the outlet. This all assists in minimising the chances of spillage, and improves clearance of the combustion products and efficiency of the fire.

The firebox base 108 also has a raised angled lip 116 near the front opening, to provide a small barrier to help prevent any loose fuel pieces, (coals/pebbles) falling out of the fire. Once again, the lip 116 is more clearly visible in the end view of Figure 3.

Finally, with reference to Figure 3, a small support bracket 118 is provided at the rear of the firebok, for reasons that will be explained later.

Figure 4 shows a side view of a burner assembly 120, housed within a burner box 122. The burner assembly comprises, among other things, a burner pad 124 positioned on top of a burner/venturi 126, both of which are housed within a burner tray 128. A three piece ceramic fibre matrix 130 is provided on top of the burner pad 124.

The burner pad 124 increases the temperature of the fuel bed, and the matrix 130 helps to increase the thermal lift of the products of combustion by intensi'ing the fuel bed glow' to compensate for the reduced heat input of the present invention. Typically, letterbox style fires have a flat base from which flames project, possibly with some decorative pebbles to create a fuel bed effect. Including a matrix 130 allows a larger fuel bed to be created so that more heat is stored by the material of the fuel bed when the fire is on. This is particularly important for open-fronted fires, because they cannot rely on the closed environment of a glass-fronted fire to retain the heat generated by combustion. The desire for maximum volume of material making up the fuel bed has to be balanced against the restriction that large volumes may cause to combustion.

The shape of the matrix 130 also orients a larger area of the fuel bed towards the opening at the front of the fire to maximise the amount of radiant heat being directed out into the room (as opposed to vertically upwards), and the addition of material, fuel effects (not shown) creating a fuel bed also helps to direct flames backwards, resulting in less chance of flames spilling forward into the room. * * -12-

The three piece matrix 130 could alternatively be formed as a single piece. However, with the elevated temperatures now achievable with gas fires, conflicting expansion rates can often not be adequately compensated by the properties of the materials used. As such, it is preferable to reduce the size of a matrix andlor cut the matrix through the higher temperature areas.

As the temperatures generated within gas fires continue to rise, new materials with improved temperature resistance are being trialled to replace the typical ceramic fibre materials currently used. These newer materials will likely comprise harder ceramic type, e.g. clay based, materials which are better able to withstand the temperatures generated within the fires.

The burner pad 124 is shown more clearly in Figure 5. It is 600mm wide and 10mm thick, made of ceramic fibre, and is quite porous. Although binders are used with the ceramic fibre these are reduced over time by the high temperatures that exist. Typically, this is not a problem because the gas/aft mixture will pass up through the slots 132 provided in the burner pad 124.

However, the presence of wood, pebble or coal decorative fuel effects can generate sufficient back-pressure to force the gas/air mixture through the material of the burner pad 124 itself. The inclusion of a matrix 130 in the present fire causes additional back-pressure and greater leakage through the burner pad 124. The leakage of unburned gasfair mixture through the burner pad 124 was contaminating the primary air drawn in at the burner venture, and affecting the combustion levels. The problem was overcome by providing a metal enclosure 134 for the burner pad 124. The metal enclosure 134 has a number of upper gaps 136 at the rear to increase the airflow to the rear of the burner pad 124 in use.

The burner pad 124 has two rows of burner slotted ports, or flame slots 132, through which the flames project. For burners of this type, the outermost front flame slots typically havea lower gas supply than the slots at the centre of the burner. The resulting flames, having less inertia, may not be drawn towards the products outlet as effectively as the other flames from the burner.

The flames from the outermost slots also have a lower temperature and are further away from -13-the greater temperature and thermal lift generated at the fire's centre. As such, the front flames from the outer edges of a wide burner can tend to spill.

The problems described above are more significant for wider burners, such as that used in the present invention, which is one reason why wide fires of this type typically require a high heat input in excess of 8kW net. To overcome the spillage problem and maximise efficiency, it was found necessary to remove the front outer/corner flame slots. The positions 138 normally occupied by the outermost front flame slots are shown in broken lines in Figure 5.

Returning to Figure 4, the burner assembly 120 of the cunent fife is sunk into the burner box 122. This, together with the width of the burner assembly 120 and the inclusion of a three tier raised matrix 130, meant that it was necessary to maximise airflow to the burner venturi 126, and to the rear of the matrix 130 for the rear flames to ensure complete combustion. The burner tray 128 therefore provides a gap below the burner. Front and rear inlet 140 and outlet 142 air slots cut into the front and rear the burner tray 128 to allow a flow of air to be drawn down under the burner to supply air through slots in the matrix 130 for the rear flames.

A gap is provided between the front of the burner box 122 and the burner tray assembly 128, and is covered by a fuel tray 144 that is raised up to sit proud of the burner box 122 and thereby provide a gap 146 for air flow under the fuel tray 144. The fuel tray 144 also has slots 148 in its rear face. i.e. the part closest to the burner tray 128, to allow air to flow through the fuel tray 144. The fuel tray 144 can be filled with gravel or fuel bed pieces (not shown) to visually extend the depth of the fuel bed and provide additional heat storage when the fire is operating.

When the fire is in operation, the resulting glow (emitted heat) from the fuel bed radiates through the slots 148 in the fuel tray, and through the gravel/fuel pieces if provided. Both the primary air flowing down to the venturi 126, and the secondary air flowing down and towards the back of the matrix 130, is pre-heated as it flows through and around the fuel tray 144. The air flowing under the burner 126 additionally scmbs heat fromthe base of the burner 126 itself The design additionally provides a sufficient gap within the burner tray 128 to add an insulation pad 150, primarily to protect the controls 152 of the fife, which are spaced below the burner fray 128, from being damaged by the high temperatures generated by the burner 126. The air flow can additionally scrub temperature from this insulation 150. This not only assists in minimising the amount of heat transmitted from to the controls 152, but also further heats the air supply to the burner 126, which further improves the fire's efficiency.

The air flows around the burner assembly are indicated by broken arrows in Figure 4, and the means to preheat these air flows prior to combustion adds to the fife's efficiency. As the room heats-up, the resulting warmer room air re-circulates back through the fire further increasing the temperature of the pre-heated air supply.

Although the idea of hot air recirculation is known, the design of the present invention allows the combustion air to be pre-heated to a considerably higher temperature than normal, i.e. 65°C compared with 35°C. This is extremely significant when calculating the efficiency, as it significantly reduces the necessary temperature rise during combustion.

Figure 6 shows the burner assembly 120, in the burner box 122, located within the firebox 101 of Figure 3. The burner box 122 is lifted through the front opening of the firebox and fitted in the burner opening 112 in the conventional way for fires of this type. It can be seen that the burtter assembly 120 is positioned towards the rear of the firebox 101 to reduce its tendency to spill its products of combustion, and to provide more free space at the front and top of the firebox 101 for the positioning of building lintels.

Figure 6 also shows a hood 154 fitted in the top opening 110 of thc firebox 101. The hood 154 has been developed so that it can be fitted through the front of the firebox 101, in the same manner as the burner box 120, and fixed in place at the top of the firebox 101 with screws. As a -15 -result, it can be applied to the firebox 101 after it has been fixed in position, so the total fife, (hood and burner box) can be installed after the builder's enclosure has been constructed.

The fuel bed and burner assembly 120 are designed to operate at the highest temperature possible to try and maximise the thermal lift of a fire, but this is always compromised by cooler room air. The larger and wider the opening at the front of a fire, the greater will be the effect of the room air and, accordingly, the less thermal lift will be provided from a burner operating at a given temperature.

The hood shape was developed and adjusted over numerous tests and its design changed to ensure that the products of combustion flowed smoothly towards the products outlet swiftly after light-up to provide a quick clearance of the products of combustion and within the typical five minute time period. Figure 7 shows the hood 154 viewed from the direction indicated 156 in Figure 6a. The side shape of the hood 154 had to be adjusted to ensure the products of combustion were collected from the widest points of the fire. The height of the hood 154, as viewed in Figure 7, is 174mm. This ensures that the thermal lift yet is maximised but still allows the hood 154 to be installed through the front opening of the firebox 101. The hood is approximately 700mm wide and 146mm deep at its base 158 to completely fill the top opening of the firebox 101. A flange 160 is provided around the base 158 of the hood 154 for fixing and sealing to the inside of the firebox 101. The end walls 162 of the hood 154 are angled inwards from the base 158 so as to form an angle of 123° with the flange 160, thus giving each end of the hood 154 an internal angle of 57° to guide the products towards the outlet.

Returning to Figure 6a, the front angle of the hood 154, marked a', is 76°. This angle had to be adjusted during development of the fire ti maximise the benefits of a baffle asembly, which will be described later. The rear angle b' of the hood 154 is 800, and the height e' of the outlet 164 is approximately 70mm. By restricting the fife's products outlet, the hood 154 reduces the amount of air drawn into the fire from the room, which is an important first stage in achieving efficiency. -16-

The ability to fit the hood 154 through the firebox 101 provides greater access for inspection of the builder's opening/enclosure and or flue without the need for removal of the firebox 101.

Furthermore, should it be necessary to disassemble the fire to allow access, for instance in a situation where major debris issues or flueing problems were apparent, this can be achieved without any damage to the building work of the enclosure or any external decoration.

Return flanges 166 are provided to strengthen the material at free edges around the outlet 164 of the hood 154. This allows thinner, lighter, material to be used, reducing the weight of the hood 154 to assist with the installation. The support bracket 118 providcd at the rear of the firebox 101 supports the weight of the hood 154 while fixing screws are fitted, further simplifying the installation process.

The outlet 164 of the hood 154 is also designed to prevent debris dropping from the flue/chimney onto the fuel bed. Typically, letterbox fires use a firebox with an open top 10, similar to that shown in Figure 1. A gather' for combustion products is sometimes built into the builder's opening to help guide the combustion products into a chimney, but this does not prevent debris from falling down onto the fuel bed. The use of the hOod 154 removes the necessity for the construction of a gather in the building enclosure.

Although the hood design had been provided to maximise the flow of combustion products into the 5" flue, there remained a leakage of products of combustion at the widest points of the fife as the flue waâ restricted to fmd the fire's spillage point. Indeed, the resulting spillage point was too low for the standard efficincy assessment to be performed. With a wide fire the temperature generated by the burner is spread over a wide area. This means that the thermal lift and resulting inertia of the products of combustion creates a more gentle lift, particularly at the edges. The products therefore lose their force/lift and spill more easily than for a narrower fire.

A separate baffle assembly 168 was therefore developed to further restrict the products as they pass through the fire. By further reducing the flow of air being drawn from the room into the fire, the baffle assembly 168 helped to maximise the effects of the thermal lift and the resulting suction developed over the ftll width of the fire.

The baffle assembly 168 is shown in Figure 8 fitted in the firebox 101 below the opening to the hood 154. The baffle assembly 168 is also shown in isolation, and in greater detail, in Figure 8a. The baffle assembly 168 is fitted over the opening to the hood 154, so its width (not visible in Figure 8a) and depth dimensions are similar to those of the hood, i.e. around 700mm and 146mm respectively.

The optimum angles of the twin baffles 170,172 were determined following a number of tests.

The front baffle 172 forms an angle d' of around 1400 with the gap 174 provided between the twin baffles 170,172. The angle of the rear baffle 170 is similar. The front edge of the front baffle 172 is spaced by a distance e' of around 17mm froth a flange 176 provided at the top of the baffle assembly 168 for fixing the baffle assembly 168 in place within the firebox 101. By lowering the front edge of the front baffle 172, a catchments area 178 (see Figure 8) is provided to retain the combustion products from falling back into the firebox and reduce the risk of spillage as the fire is restricted. It may also be possible to lower the baffle assembly 168 and/or the firebox top 106 even further to increase the efficiency of the fife.

The position and size of the gap 174 between the two baffles 170,172 is also important in reducing the tendency of the fire to spill as the flue was restricted. The gap 174 of the baffle assembly 168 shown in Figure 8a is around 100mm.

A return flange 180 is once again provided to strengthen the material at the free edge of the rear baffle 170 and reduce the weight of the baffle assembly 168 to help with installation. The angle of the return flange 180 provides a further advantage in that the flames of the fire tend to cling to the angle of the metal, directing the combustion products towards the products outlet. This -18 -ifirther improves the performance of the fife and reduced the tendency of the flames to flow forward causing spillage. The baffles 170,172, in particular the rear baffle 170, provide a fbrther obstacle to prevent any debris from the chimney that does enter the outlet 164 of the hood 154 from falling into the firebox 101.

The baffle assembly 168 also helps to retain the side liner panels 105 shown in Figure 2 in position at the top of the firebox 101. The baffle assembly and the liner panels 105,107 can be fitted after all other installation requirements to minimise the risk of damaging the liner panels.

The general flow of combustion products around the deflector assembly 168 and the hood 154 is shown in Figure 8 using broken arrows: Figure 9 shows a sheet metal restrictor 182 fitted within the hood assembly to further reduce the area of the outlet. A restrictor of this type might be required when a flue is drawing too much air through the fire. Often, an installer will routinely include a restrictor if a flue has an effective height over tlree meters. In these circumstances, the restrictor 182 would generally be fitted to the inside of the hood 154, such that the hood 154 and restrictor 182 would be fitted at the same time. The baffle assembly would then be fitted afterwards.

If, for some reason, the flue is found to be performing poorly and not clearing its products of combustion after about five minutes from cold, then the restrictor 182 may need to be removed.

In such situations, the fire would be turned off and allowed to cool. The installer would then remove the baffle assembly and the restrictor 182 could then be removed through the front opening of the firebox 101, as shown in Figure 9, without any difficulty. To achieve this, the restrictor plate 182 had to be made taller and the fixing holes positioned such that a screwdriver could be applied at the correct angle directly onto the restrictor fixing screws when working from the open front of the firebox 101. With some further development, it is hoped that the restrictor 182 could be removed without moving the baffle assembly. -19-

Restrictors are not typically included in wide open-fronted fires of this type, because their general focus is not on efficiency so the amount of air drawn through the fire by the flue is not a serious consideration. The present invention is the first fire of this type to need a restrietor, and therefore provide a means to fit or remove it.

Many other type of fires have their restrictors at the rear, meaning that removing a restrictor if a problem is found is extremely difficult, and often requires the entire fire to be removed. As such, the ability in the present invention to remove a resfrictor from the rear of the fire with relative ease also provides an advantage over many known fires of other types.

With the fmal design of both baffle assembly 168 and hood 154 it was found that spillage was initially quite evenly distributed over the flaIl width of the baffle assembly 168, and that the fire* actually spilled more at the centre as the flue was restricted, indicating that the baffle assembly 168 and hood 154 design was maxiniising the effectiveness of the fire's thermal lift. The baffle position and the resulting gap 174 enabled the fire to clear more quickly than without the baffle assembly 168 fitted, and its performance together with the restrictor 182 resulted in a Class 2 net efficiency rating of 62.4%. This level of efficiency is a first for wide open-fronted fires of this type.

The fire of the present invention has so far been described for installations with a ready made chimney. However, in some installations there is no chimney and so both the builder's opening/enclosure and flue system have to be provided. With this system, a means has to be provided whereby the flue, e.g. a flexible flue liner, can be connected directly and sealed to the products outlet.

Figure 10 shows an alternative installation of the fire where a canopy 184 is used in place of the hood. The baffle assembly 168, being formed as a separate component, can be used equally with either the hood 154 or the canopy 184.

-20 -Although it is known to provide similar canopies with fires of this type, they are generally attached to the firebox before installation. This means that the builder's opening/enclosure has to be made very large initially, and then closed up around the canopy after the firebox and canopy have been installed. In contrast, the canopy 184 of the present invention can be installed through the firebox front opening, as shown in Figure 10, after the firebox 101 has been installed and fixed in place, in much the same way as described previously for the hood 154. The flexible flue 186 can be secured to the top of the canopy 184 within the firebox 101 before the canopy 184 is pushed up and secured in place in the top opening 110 of the firebox 101. The flexible flue 186 is then fixed and sealed at roof level.

This means of fitting the canopy 184 can also be of assistance where it is discovered, after fitting a fire, that a chimney is performing poorly. Cracks, holes, or other leaks in a chimney can prevent it Born operating properly and clearing combustion products from a fire even where the fire's outlet is unrestricted. Often, the only way to resolve this is by lining the chimney with a flexible flue liner. With the present invention, this can be done after the firebox 101 is installed without any need to dismantle the builder's opening/enclosure. If leaks are detected, or develop, in the flue after a fife is installed, then the hood 154 of the fire can be removed through the front opening of the firebox 101 and simply replaced with a canopy 184 and flue liner while leaving the firebox in place.

The firebox base has been adapted to allow a cable fixing bracket system to be used when installing the firebox. Eyebolts are secured within the builder's opening and cables are run through these and through brackets in the firebox, and are then tightened to secure the fire in place. This avoids any drilling of the materials around the enclosure formed for the fire, which can cause chipping or cracking. Elevating the base of the firebox provided space for these cable fixing brackets to be included without increasing the overall height of the firebox or impeding it from sliding into or out of the enclosure. -21 -

After the firebox has been slid into the builder's enclosure and secured with the cable fixing system, the burner box is then dropped through a hole in the firebox base, which locates it in its correct position.

Although the fife of the present invention will commonly be fitted into a completed builder's opening/enclosure and fmished with a frame or surround, it is also possible to install the firebox 101 to provide a so-called trimless fire. The firebox 101 would be built-in to the builder's enclosure before the outer plaster, board is applied, such that the edges of the plaster board fully cover the front flanges of firebox 101 providing the front of the fire with a rectangular triniless opening.

This method of providing a trimless fire is known, and always requires the firebox to be built-in at the building stage, much like the glass-fronted fires discussed earlier. However, unlike with known built-in fires, all other components of the fire of the present invention, such as internal linings, burner box 120, hood 154 or canopy 184, liner panels 105,107 and baffle assembly 168, can be fitted through the front opening of the firebox 101 after all building work has been finished. In particular, by allowing the liner panels 105,107 to be fitted last, the risk of damage to these delicate components during the building process of the enclosure and installation of the firebox 101 is removed.

Only the firebox 101 need be built-in prior to being plaster boarded in position. The fmal installation can be carried out after the building work has been finished and is fully cUred.

Furthermore, a high degree of access to the flue and builder's enclosure remains possible by removing the hood 154 and burner box 120 through the firebox. This avoids the work and damage associated with removing the fircbox for servicing, and the costs of servicing the fife are thereby minimised.

-22 -Although not shown in the drawings, a removable debris plate is provided within the base of the burner box 122 to allow access to the base of the chimney for clearing/checking for debris that may build up and block the chimney. This debris plate ensures that is not necessary to* remove the fife when checking for debris build-up, and also doubles as a means for providing easier routing and sealing of the gas inlet pipe.

The burner box 122 also provides a battery holder, designed to be housed low within the burner box in its own metal enclosure that provides an air jacket/gap around the battery holder. The fire generates a lot of heat, meaning that batteries and controls 152 and the remote control receiver housed in the burncr box 122 need to be located as far from the heat source as possible.

These temperature constraints mean that controls and batteries have previously been housed remote from the fire in a self contained housing, for example in the side of the chimney breast or housed within a standard single electrical wall switch box. In the present invention, the batteries to provide control of the fire are housed within the burner box 122 so that the fife and controls are therefore totally self contained. This helps with the realism of the fife as no means of control like switch boxes are visible.

However, locating the batteries so deep within the fire makes access to the batteries more difficult. To address this issue, the battery holder sits in a cradle having an extended handle that locates it centrally within the battery enclosure. This helps to maintain an even air jacket/gap around the battery holder, and also enables the batteries to be changed by the customer, through an opening provided in the fuel fray assembly at one end of the burner assembly 120, rather than requiring a technical specialist.

The burner box 122 is also deep enough to allow for provision of a mains operated lighting system that could also be controlled by the remote control handset, possibly with provision for dimming the lights. Additional batteries could also be incor3orated to provide LED lighting, again with dimming controllability. Additional remote systems could be housed within the -23 -burner box, which could be made deeper if needed, provided its height did not restrict installation through the front opening of the firebox 101.

The invention is not considered to be limited to the specific embodiments described above. The configuration of the structure as well as the dimensions and, to a certain extent, the material of the component parts would be dependent on a specific application.

The features described above were developed in connection with a 780-800nn wide, letterbox style, open-fronted fire. However, the features would be equally applicable to narrower fires of a similar style or, in many cases, different styles of gas fifes. It is also possible that the features described could allow even wider open-fronted fires to be produced with a considerable higher efficiency than currently available fires.

The heat inputs and efficiency levels quoted were obtained using a natural gas fuel supply, but the features of the fire would provide similar benefits in Propane fuelled fires. The maximum heat output was achieved with a fuel bed consisting of wood effect piec&s laid on the matrix 130, however similar levels were achieved with both pebble and coal effects. Other fuel effect pieces of any shape could also be used.

Claims (27)

1. CLAIMS1. A gas fire comprising a firebox with a base, a top, and an open front; the firebox, in use, being received in an enclosure, a burner assembly recessed below the firebox, and a hood above the firebox for gathering combustion products from the firebox and restricting the outlet of the fire.
2. 2. A gas fire according to claim 1, wherein at least a part of the top of the firebox is angled downwards from the open front towards the rear of the firebox.
3. 3. A gas fire according to claim 1 or 2, wherein the burner assembly is located towards the rear of the firebox.
4. 4. A gas fire according to claim 3, wherein the base of the firebox is raised up at the rear to raise the position of the burner assembly.
5. 5. A gas fire according to claim 3 or 4, wherein a ridge is provided on the base of the firebox, between, and substantially parallel with, the burner assembly and the front of the firebox.
6. 6. A gas fire according to claim 3 or 4, wherein a strip of glass is provided at the base of the firebox, between, and substantially parallel with, the burner assembly and the front of the firebox.
7. 7. A gas fife according to any of the preceding claims, wherein the burner assembly comprises a burner tray with air gaps to allow air to flow around components of the burner assembly.
8. 8. A gas fire according to claim 7; wherein the components of the burner assembly comprise a burner/venturi and a burner pad.
9. 9. A gas fire according to claim 8, wherein a metal enclosure is provided around side edges of the burner pad.
10. 10. A gas fire according to claim 8 or 9, wherein the burner pad is substantially rectangular and wherein two rows of flame slots, each parallel with a long edge of the burner pad, are provided through the burner pad, one row comprising fewer flame slots than the other row such that no flame slots are provided adjacent to two corners of the burner pad.
11. 11. A gas fife according to any of claims 7 to 10, wherein the components of the burner assembly further comprises an insulation pad below the burner/venturi.
12. 12. A gas fire according to any of claims 7 to 11, wherein the burner assembly further comprises a fuel tray through which air flows when entering the burner assembly.
13. 13.A gas fire according to any of claims 7 to 12, wherein the burner assembly is housed in a burner box which is received in an opening in the base of the firebox.
14. 14. A gas fire according to claim 13, wherein the burner box further houses controls and batteries for the fire.
15. 15.A gas fire according to any of the preceding claims, wherein the hood is received through the open front of the firebox and installed in an opening formed in the top of the firebox.
16. 16. A gas fire according to claim 15, wherein the hood is located in said opening after the firebox has been fitted in the enclosure.
17. 17. A gas fire according to claim 15 or 16, wherein the hood comprises an inlet, located adjacent to the top of the firebox, and an outlet which is smaller than the inlet, and located outside the firebox.
18. 18. A gas fire according to claim 17, wherein the outlet of the hood is located at the top of the hood in a wall of the hood which, in use, faces away from the front of the firebox.
19. 19. A gas fire according to claim 17 or 18, wherein the hood comprises two end walls which are angled towards each other as they extend away from the inlet.
20. 20. A gas fire according to any of claims 17 to 19, further comprising a baffle assembly fitted in the firebox over the inlet of the hood.
21. 21. A gas fire according to claim 20, wherein the baffle assembly is formed as a unitary component.
22. 22. A gas fire according to claim 20 or 21, wherein the baffle assembly comprises two angled baffles.
23. 23. A gas fire according to any of the preceding claims, wherein the enclosure is formed in a building wall.20.
24. 24. A gas fire aQcording to any of claims I to 22, wherein the enclosure is formed proud of a building wall:
25. 25. An open-fronted gas fire having a front opening with a width of 750mm or more, and a net heat input of under 7kW.
26. 26. An open-fronted gas fire according to claim 25, further comprises the features of any of claims I to24.
27. 27. A gas fire substantially as herein described with reference to the accompanying drawings.