FIELD OF THE INVENTION  
       [0001]     This invention relates to gas inserts designed to be retrofitted into fireplaces.  
       BACKGROUND OF THE INVENTION  
       [0002]     It is known to provide gas fireplace inserts that are designed to be retrofitted into wood burning fireplaces. Examples of such inserts are disclosed in U.S. Pat. No. 5,191,877 to Shimek, U.S. Pat. No. 5,752,500 to Jamieson et al., U.S. Pat. No. 6,029,655 to Hussong et al. and U.S. Pat. No. 6,116,232 to Valters et al.  
         [0003]     The use and installation of gas fireplace inserts are constrained by certain conditions. Inserts of the sealed combustion type are often provided with an integral heat exchange passageway around the firebox into which room air is drawn in, heated and expelled back into the room. The pathway is defined by an outer wall of the insert that is spaced from the top and back walls of the firebox. Circulation of air through the pathway is often ensured by a blower mounted beneath or to the rear of the firebox. Legs or brackets supporting the firebox base provide a gap under the firebox to accommodate the gas piping and controls (and sometimes a blower) and to define the bottom part of the pathway. Heated air is exhausted forward into the room from the top of the firebox, immediately above the window of the insert.  
         [0004]     Gas fireplace inserts should provide an aesthetically pleasing appearance. One means of doing so is to mask the gap between the insert and the inner walls of the hearth of the original fireplace. This is accomplished by providing trim designed to overlap the outer edges of the fireplace mouth (and sometimes the louvers and original fireplace facing). The trim connects to the insert such that the insert window lies generally in the plane of the fireplace mouth.  
         [0005]     In order to provide as large a window as possible while still accommodating the outer dimensions of the insert, the insert is made as large as possible while still allowing it to be slid to the back of the hearth. As a result, there is usually very little clearance (sometimes as little as half an inch) between the top of the insert and the bottom of the lintel, baffle or smoke curtain that is provided in many wood burning fireplaces. This tight fit presents challenges to installers who are required to fit ducting or liners from the flue onto the insert&#39;s vent connector. In some cases, installers are known to remove the smoke curtain, portions of the masonry wall of the fireplace and the metal floor of manufactured fireplaces in order to install inserts. Such modifications to the fireplace stand the risk of running afoul of building codes and gas appliance restrictions.  
         [0006]     Because of the use of trim that extends from the edges of the window of the insert to past the edges of the fireplace mouth, there is often a disproportionate amount of trim in relation to the surface area of the window. This may detract from the appearance of the fireplace by making the window look small in proportion to the overall fireplace. Various approaches are taken to minimize such effect. These include maximizing the size of the window within the constraints mentioned above, as well as providing various decorative elements and treatments to the facing. This “porthole” effect is compounded by the fact that a portion of the front area of the insert is taken up by the outlet of the heat exchange passageway, leaving less space available for the window.  
         [0007]     As inserts are seated on the floor inside the hearth with a glass panel in the plane of the fireplace mouth, this constrains how far into the fireplace hearth the insert can be seated. This usually makes the insert look significantly shallower than the original fireplace.  
         [0008]     It is an object of the present invention to provide a fireplace insert that offers an improved physical appearance to the installed insert. More particularly it is an object of the invention to provide an insert that looks larger, sits deeper, and is less distinguishable as an insert than the inserts of the prior art.  
         [0009]     It is a more particular object of the invention to provide a gas fireplace insert wherein the installed insert creates the illusion of a single appliance set in an open hearth while still providing effective heating and circulation of room air.  
         [0010]     It is a further object of the invention to provide a fireplace insert for a wood burning fireplace that is easier to install than prior art inserts, and which is easier to connect the insert vent to flue liners or ducting.  
         [0011]     It is yet a further object of the invention to provide airflow around the fireplace insert that minimizes obstructive turbulence near the top of the insert.  
         [0012]     These and other objects of the invention will be more fully appreciated by reference to the detailed description that follows. It will be noted that not all objects of the invention are necessarily realized in all possible embodiments of the invention as defined by each claim.  
       SUMMARY OF THE INVENTION  
       [0013]     The invention consists of a gas fireplace insert assembly for insertion into a fireplace comprising a hearth with a floor, a mouth and a lintel. The insert assembly comprises a firebox having a base, a top, rear and side walls, and an outer shroud defining an heat exchange passageway surrounding the firebox for conveying air around the firebox and back into the room.  
         [0014]     According to one aspect of the invention, the insert assembly comprises an air guide plate extending forward of the top of the passageway outlet. In a more particular aspect, the guide plate is adjustably securable to extend at various distances and angles from the top of the passageway outlet, thereby allowing the pathway outlet to be above the top edge of the fireplace mouth. This in turn allows the top edge of the insert window to be less visible from outside the fireplace.  
         [0015]     In another aspect the guide plate comprises spaced threaded stubs, the spacing of which corresponds to spacing between slots formed in tabs extending forward of the top of the insert, said stubs being adapted to be seated in said slots.  
         [0016]     According to another aspect of the invention, the insert comprises removable legs adapted to be removably secured to the bottom surface of the firebox. These allow the insert to be installed and then raised off the floor in the fireplace hearth such that the passageway outlet may be higher than the bottom edge of the lintel or smoke curtain, before securing the legs to the insert.  
         [0017]     In another aspect, the top of the rear wall of the firebox is coloured a dark colour such as black while the balance of the rear wall has a lighter, contrasting colouring whereby to simulate the appearance of an open firelog basket.  
         [0018]     In yet a further aspect, the invention comprises a gas fireplace insert and a decorative fender for installation in front of said insert, and wherein the fender is seated in front of the insert and rearwardly of the plane of the fireplace mouth.  
         [0019]     In yet a further aspect, the invention comprises a fireplace comprising a fireplace hearth with a floor, a gas fireplace insert seated on said hearth floor, at least one vent extending from the firebox of the insert to the exterior of the fireplace and wherein the space between the gas fireplace insert and the interior walls of the hearth function as a passageway for drawing in room air, circulating said room air around the gas fireplace insert and expelling said room air back into the room.  
         [0020]     In yet a further aspect, the fireplace according to the invention includes a gas fireplace insert that has a front window with a transparent panel therein, said panel being in a plane that is spaced rearwardly from the plane of the mouth of the fireplace, the panel extending upwards at least to within 2 inches of the lintel.  
         [0021]     In a further aspect of the fireplace according to the invention, the fireplace hearth has a rear wall that is painted black, and portions of said rear wall are visible from the front of the fireplace.  
         [0022]     In yet a further aspect, the invention comprises a fireplace including an insert with removable legs on the base thereof, means for connecting a guide plate to the top of the insert, a guide plate extending from the top of the insert forward to the front of the top edge of the fireplace mouth, the insert being seated into the fireplace such that the window of the insert lies in a plane that is rearwardly offset in relation to the plane of the fireplace mouth, and a fender seated on the fireplace hearth and set back into the fireplace. The top edge of the insert window is located within 2 inches of the top edge of the fireplace mouth. The top portion of the rear wall of the insert firebox is coloured a darker colour such as black and room air has substantially unimpeded access to the sides of the insert.  
         [0023]     In another aspect the invention comprises a method of installing a fireplace insert comprising the steps of removing removable legs from the base of the insert, sliding the insert into the hearth such that the plane of the insert window is spaced rearwardly from the plane of the fireplace mouth, connecting liners to the insert, raising the insert into the fireplace and re-installing the legs, and installing a guide plate between the top of the insert and the top of the fireplace mouth. In a further aspect, a fender is also disposed on the hearth floor in front of the insert and rearwardly of the plane of the fireplace mouth.  
         [0024]     In another aspect, the invention comprises a gas fireplace insert assembly, comprising a firebox having a base and legs adapted to be removably secured to said base.  
         [0025]     In a further aspect, the firebox comprises a top and at least one wall, the wall extends between the top and the base such that the base, the top and the at least one wall define a front-opening firebox; the wall has a rear portion and side portions having a dark colour and a contrasting light colour, the light colour extends downward from a demarcation between the dark and light colours to the base; and the demarcation is continuous across the rear and side portions. In yet a further aspect, the at least one wall comprises a rear wall and opposed side walls.  
         [0026]     In a further aspect, the top and base each have inner surfaces facing the interior of the firebox and outer surfaces, and the dark colour is applied to the inner surfaces, to the outer surfaces, to the legs and to an outer surface of the wall.  
         [0027]     In another aspect, the invention comprises a gas fireplace insert assembly with a decorative fender having a width of at least the distance between the opposed side walls of the assembly.  
         [0028]     In further aspect, the invention comprises a gas fireplace insert assembly with a heat exchange passageway for conducting air from the vicinity of the base and along at least one outer wall of the firebox, and having an outlet defined between the top and a top panel mounted in spaced relationship to the top; a guide plate for guiding in a forward direction air exiting the outlet, where the guide plate is removably attached to said top panel; and a decorative fender having a width of at least the distance between opposed side walls of the assembly.  
         [0029]     In a further aspect, the top panel comprises one or more forwardly extending tabs and the guide plate is adapted to be removably attached to said tabs. In yet a further aspect, the guide plate comprises one or more downwardly extending stubs, each of which is adapted to be removably attached to one of the forwardly extending tabs; and each of the one or more downwardly extending stubs may be spaced from a longitudinal centreline of the guide plate.  
         [0030]     In another aspect, the invention comprises a gas fireplace insert assembly comprising a firebox having a base, opposed side walls and a top; legs adapted to be removably attached to the firebox base; a heat exchange passageway for conducting air from the vicinity of the base and along at least one outer wall of the firebox, and having an outlet defined between the top and a top panel mounted in spaced relationship to the top; and a guide plate for guiding in a forward direction air exiting the outlet, the guide plate being removably attached to the top panel.  
         [0031]     In another aspect, the invention comprises a gas fireplace insert assembly comprising a firebox having a base, opposed side walls and a top; a heat exchange passageway for conducting air from the vicinity of the base and along at least one outer wall of the firebox, and having an outlet defined between the top and a top panel mounted in spaced relationship to the top; and a guide plate for guiding in a forward direction air exiting the outlet, the guide plate being removably attached to said top panel. In a further aspect, the gas fireplace insert assembly may comprise legs adapted to be removably attached to the firebox base.  
         [0032]     In another aspect, the invention comprises a fireplace comprising a hearth having a floor, a mouth and a lintel and further comprising a gas fireplace insert assembly resting on the floor, where the insert assembly comprises a base, a top and at least one wall extending between the base and the top and legs adapted to be removably secured to said base; where the top extends above the height of the lintel.  
         [0033]     In a further aspect, the invention comprises a fireplace with a heat exchange passageway for conducting air from the vicinity of the base and along at least one outer wall of the firebox, and having an outlet defined between the top and a top panel mounted in spaced relationship to the top and a guide plate for guiding in a forward direction air exiting the outlet, the guide plate being removably attached to said top panel.  
         [0034]     In yet a further aspect, the invention comprises a fireplace with at least two contrasting colours inside the insert assembly; and a dark colour applied to the inside of the hearth. The contrasting colours may comprise a dark colour and a light colour. In yet a further aspect, the wall of the insert assembly may have a rear portion and side portions having a dark colour and a contrasting light colour, the light colour extending downward from a demarcation between the dark and light colours to the base; and the demarcation being continuous across said rear and said side portions. In yet a further aspect, the dark colour may be further applied to the legs and to all outer surfaces of the insert assembly.  
         [0035]     In a further aspect, the fireplace may comprise a decorative fender inside the hearth, between the insert assembly and the mouth. The decorative fender may be unsupported by the insert assembly.  
         [0036]     In another aspect, the invention comprises a method of installing a gas fireplace insert assembly in a fireplace having a rear wall, a hearth having a floor, a mouth and one or more ducts, comprising the steps of placing a gas fireplace insert onto the floor through the front opening; connecting the insert to the one or more ducts; and attaching one or more supports to an underside of the insert, thereby lifting the insert away from the floor.  
         [0037]     In a further aspect, the method of the invention may comprise installing a gas fireplace insert assembly, wherein the insert further comprises a firebox having a base, a top and a heat exchange passageway for conducting air from the vicinity of the base and along at least one outer wall of the firebox, the heat exchange passageway having an outlet defined between the top and a top panel mounted in spaced relationship to the top, and the method may further comprise the step of attaching to the top panel a guide plate for guiding in a forward direction air exiting the outlet, the guide plate being removably attachable to the top panel.  
         [0038]     In yet a further aspect, the method of the invention further comprises the step of placing a decorative fender on the floor of the fireplace between the insert and the mouth.  
         [0039]     Other aspects of the invention will be appreciated by reference to the detailed description of the preferred embodiment and to the claims. 
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0040]     The preferred embodiment of the invention will be described by reference to the attached drawings in which:  
         [0041]      FIG. 1  is a perspective view of an embodiment of the insert assembly according to the preferred embodiment of the invention;  
         [0042]      FIG. 2  is a front view of an embodiment of an insert according to the invention, excluding the heat exchange shroud;  
         [0043]      FIG. 3  is an exploded perspective view of the insert of  FIG. 2 ;  
         [0044]      FIG. 4  is a front view of an embodiment of the insert and shroud;  
         [0045]      FIG. 5  is a sectional view along line  5 - 5  of  FIG. 4 , and further including the heated air exhaust guide plate;  
         [0046]      FIG. 6  is a perspective view of the removable legs of an embodiment of the insert assembly;  
         [0047]      FIG. 7  is a front view of an embodiment of the insert assembly, in place in a typical fireplace hearth, without a fender;  
         [0048]      FIG. 8  is a sectional view along line  8 - 8  of  FIG. 7 , including a fender;  
         [0049]      FIG. 9  is a rear view of the firebox and heat exchange shroud of an embodiment of the insert assembly, with the air inlet collar exploded therefrom;  
         [0050]      FIG. 10  is a perspective view of the heated air exhaust guide plate;  
         [0051]      FIG. 11  is a bottom view of the heated air exhaust guide plate;  
         [0052]      FIG. 12  is a side view of the connection between the heated air exhaust guide plate and the top shroud panel of the insert; and  
         [0053]      FIG. 13  is a front view of an embodiment of the insert assembly, in place in a typical fireplace hearth.  
     
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT  
       [0054]     Referring to  FIG. 1 , the insert assembly  10  according to the preferred embodiment generally comprises an insert  12 , a heated air exhaust guide plate  14  and a decorative fender  16 .  
         [0055]     Insert  12  includes a firebox, a burner assembly, a shroud partially surrounding the firebox and a heat exchange passageway, as described below. A log set  150  (seen only in  FIG. 13 ), for example ceramic simulated logs, may be placed within insert  12  to enhance the resemblance of insert assembly  10  to an actual wood-burning fireplace.  
         [0056]     Referring to  FIGS. 2 and 3 , a front-opening firebox  18  is defined by a base  20  (which may be a full base or a base rim  20 , as in the illustrated embodiment), a rear wall  22 , at least one side wall (two opposed side walls  24 ,  26  are shown in the embodiment illustrated in  FIGS. 2 and 3 ) and a firebox top  28 . A baffle  30  controls the flow of combustion exhaust gases. Firebox cover  31  includes an aperture  33  to which is attached an exhaust collar  35 .  
         [0057]     A burner assembly is seated on base rim  20  and includes a burner plate  56 , a burner  32 , a pilot assembly  34  and a control and fittings assembly  36 . A window and glass panel  38  are fitted to the front of the insert  12 .  
         [0058]     Referring to  FIGS. 4 and 5 , a heat exchange passageway  40  is defined by a shroud comprising side shroud panels  42 ,  44  (seen only in  FIG. 4 ), rear shroud panel  46  and top shroud panel  48 , each of which is spaced from the adjacent walls of the firebox  18  to define the passageway  40 . Gaps  50 ,  52  at the bottom edges of the side shroud panels  42 ,  44  and gap  53  at the bottom edge of rear shroud panel  46  form room air inlets for the passageway  40 .  
         [0059]     A gap  54  at the forward edge of the top shroud panel  48  defines the passageway outlet. In use, room air is drawn under the burner plate  56  as indicated by arrow  57 , through the gaps  50 ,  52  and  53 , up the sides  58 ,  60  and rear  62  portions of the passageway  40  and across the top  64  of the passageway  40 . The heated air is exhausted out of the outlet  54  between the top shroud panel  48  and the firebox cover  31 . A blower (not shown) may optionally be seated beneath the firebox to draw room air under the base and into the heat exchange passageway. In the absence of a blower, natural convection will draw sufficient room air into the passageway  40 .  
         [0060]     Referring now to  FIGS. 5 and 8 , combustion air is drawn through a vent liner  66 , partially visible in  FIG. 8 . Vent liner  66  is attached to combustion air inlet collar  79  (see  FIG. 9 ) and into a combustion air duct  68  defined between wall  70 , top shroud panel  48  and rear shroud panel  46 .  FIGS. 1-5  illustrate a pair of short inlet pipes  72 ,  74  that extend from combustion air duct  68 , through heat exchange duct  40 , and that open into the bottom of the firebox  18 . Only inlet  74  is visible in the views provided by  FIGS. 1-3 .  
         [0061]     As best seen in  FIG. 9 , the forward edge of the top shroud panel  48  is provided with opposed, forwardly extending tabs  76 ,  78  each comprising an elongated slot  80 ,  82  for securing heated air exhaust guide plate  14  to the top shroud panel  48 .  
         [0062]     Guide plate  14  is illustrated in  FIGS. 10 and 11 . It comprises an elongated generally rectangular panel having a length approximately corresponding to the lateral extent of the insert. The width of the panel may be chosen to suit the fireplace in which the insert will be installed. For a typical 36″ wide by 17″ high by 14″ deep fireplace, the width of the preferred panel according to the invention is 5″. The underside of the guide plate  14  is provided with two threaded stubs  84 ,  86  sized for engagement into slots  80 ,  82  of the tabs  76 ,  78 .  
         [0063]     As best illustrated in  FIG. 12 , guide plate  14  may be secured to tabs  76 ,  78  of top shroud panel  48  by engaging stubs  84 ,  86  into slots  80 ,  82  and tightening wing nuts  88 ,  90  onto the stubs. Stubs  84 ,  86  are spaced from the rear edge  92  of the guide plate  14  a distance greater than the distance between the forward end of the slots  80 ,  82  and the forward edge of the top shroud panel  48 . Doing so ensures that when the stubs  84 ,  86  are engaged at the forwardmost end of the slots  80 ,  82 , the rear edge  92  of the guide plate will still extend rearwardly of the forward edge of top shroud panel  48 . Provided the stubs  84 ,  86  are spaced from the longitudinal centreline of the guide plate  14 , the guide plate  14  can be turned around to achieve a different maximum forward reach.  
         [0064]     Referring to  FIG. 8 , guide plate  14  acts to direct heated room air that is exhausted from the duct outlet  54 . This allows the top of the duct outlet  54  to be above the top edge  94  (which may be the bottom edge of a smoke curtain or lintel  96 ) of the fireplace mouth  95 . As a result, the insert may be seated higher off the floor  99  of the fireplace hearth than is the case for prior art inserts, thereby allowing the top edge of the glass panel  38  to be completely or nearly hidden from view. This helps to camouflage the top part of the insert and enhances the illusion of a simple burner seated in an original fireplace.  
         [0065]     As best shown in  FIG. 6 , a pair of removable supports, such as legs  100 ,  102  are each provided with spaced posts  104 ,  106 . One of posts  104  has a horizontal flange  108  through which a leveling bolt  110  is threaded. Each support  100 ,  102  also includes an upper flange  112  provided with a bore  114  adapted to receive a screw  116 , and two upstanding walls  118  to assist in locating the support in relation to the base rim  20  of the insert  12 . Legs  100 ,  102  are preferably shaped to correspond to the shape of base rim  20  on respective sides of the insert  12 . Rim  20  is provided with bores  120  to correspond with each of bores  114  for releasably securing legs  100 ,  102  to the rim  20  during installation of the insert  12 .  
         [0066]     A decorative fender  16  is provided with suitable means  122  allowing the fender  16  to be positioned as a freestanding unit on the floor  99  of the fireplace hearth  98  in front of the insert  12 . Fender  16  is preferably made to resemble a protective fender used in an open hearth fireplace. Fender  16  generally has a width of at least the distance between the opposed side walls  24 ,  26 .  
         [0067]     The installation of the fireplace insert assembly according to the invention will now be described with references to  FIGS. 7 and 8 . The insert assembly is generally installed in an existing fireplace having a rear wall  97 , a hearth  98  with a floor  99 , a front mouth  95 , and one or more ducts or liners  66  and/or  68 , normally including at least an exhaust liner and for sealed combustion systems, a combustion air liner.  
         [0068]     Prior to seating the insert assembly  10  into the fireplace hearth  98 , legs  100 ,  102  are removed from the insert assembly  10 . The insert assembly  10  is then slid rearwardly through fireplace mouth  95 , along the hearth floor  99  and as far back as possible into the hearth  98 . It is no longer necessary to align the front panel of the insert assembly  10  with the mouth  95 , as is required in the prior art.  
         [0069]     With the legs  100 ,  102  removed and the insert assembly  10  seated and set back on the floor  99  of the hearth  98 , there is sufficient space above the insert assembly  10  to enable the installer to connect the exhaust and combustion air liners  66 ,  68  to the collars  35  and  79  respectively, without the need for sophisticated vent engagement systems. The clearance provided by the insert assembly  10  and the position of the insert assembly  10  in the fireplace make access to the liners and their connection to the insert assembly  10  considerably easier than in the prior art.  
         [0070]     Once the liners are connected to the insert assembly  10 , the insert assembly  10  is then raised off the floor  99  of the hearth  98  and legs  100 ,  102  are re-installed on the base of the insert assembly  10  using appropriate fasteners.  
         [0071]     The guide plate  14  is installed by first loosely engaging wing nuts  88 ,  90  onto stubs  84 ,  86 . The guide plate  14  is then angled past the top edge  94  of the fireplace mouth  95  and stubs  84 ,  86  are engaged into slots  80 ,  82  of tabs  76 ,  78  such that tabs  76 ,  78  are sandwiched between the wing nuts  88 ,  90  and the guide plate  14 . The guide plate  14  is then extended forward to contact, or nearly contact, the front of the fireplace and the wing nuts  88 ,  90  are tightened.  
         [0072]     The guide plate  14  ensures that air exhausted from the heat exchange passageway outlet  54  will be directed to the fireplace mouth  95  with minimal turbulence being generated atop the insert  10 . This arrangement promotes the smooth flow of air back into the room resulting in increased efficiency.  
         [0073]     Fender  16  is then installed in front of the insert assembly  10 , but is placed as far back into the hearth  98  as possible. The ability to set back the fender  16  on the floor  99  of the hearth  98  is the result of the ability to set back the insert assembly  10  itself into the fireplace mouth  95 . This in turn is the result of using the guide plate  14 , which overcomes the turbulence effects that would otherwise be suffered from seating the insert assembly  10  too far back into the fireplace mouth  95 .  
         [0074]     No additional facing or trim is required around the edges of the insert assembly  10  or of the fireplace mouth  95 . The absence of trim and the setting back of the insert assembly  10  and fender  16  into the fireplace hearth  98  enhances the effect of a stand-alone grate and log set  150  seated in a fireplace enclosure.  
         [0075]     Colouring the upper portion  146  of at least one of the firebox side walls  24 ,  26 , rear wall  22  and baffle  30  a darker colour, such as black, while providing a contrasting lighter coloured lower portion  148  surrounding the log set  150  can further enhance such effect. In an embodiment best shown in  FIG. 13 , the lighter coloured portion  148  wraps around the lower portions of side walls  24  and  26  in an arc descending from back to front, the arc continuing across rear wall  22 . The contrast provided by the demarcation between the light and dark areas distracts the viewer from the joints and edges of the side and rear walls and enhances the illusion that the fireplace insert  10  spans the entire width of the fireplace, rather than being confined to the area within the firebox  18 . This produces the same visual effect as would be expected in a wood-burning fireplace where soot, ash and other residue rise up from the burning logs towards a chimney, but partially deposit on the rear wall of the fireplace. This also camouflages the edges of the insert assembly  10 , allowing the edges to blend into the shadows of the hearth  98 . The insert assembly  10  in place thus appears identical to a wood-burning fireplace and appears to completely occupy the space inside the fireplace hearth  98 , without excess trim or other components around the outer edges of insert assembly  10 .  
         [0076]     The inner surfaces of the hearth  98  may also be coloured a dark colour, similar to the dark colour on the insert assembly  10 , further camouflaging the edges of the insert assembly  10  and providing the illusion of a larger, deeper hearth  98 .  
         [0077]     In another embodiment, more parts of the insert assembly  10 , except the lighter coloured portion  148 , may also be a dark colour. This may include the outer surfaces of the base rim  20 , rear wall  22 , side walls  24 ,  26 , firebox top  28  and legs  100 ,  102 , to ensure no outer part of the insert assembly  10  is visible in the darkness of the hearth  98   
         [0078]     The insert assembly  10  according to the invention may include a window that is larger than the prior art inserts and whose top edge is hidden behind the top edge of the fireplace mouth  95 , further masking the frame of the insert  10 .  
         [0079]     As the invention obviates the need for trim between the insert assembly  10  and the fireplace mouth edges, a freer flow of room air around the insert is made possible. Despite seating the insert assembly  10  as far back as possible within the fireplace hearth, there will typically be space for room air to be drawn in around the sides of the insert, in addition to any room air entrained into the heat exchange passageway. Such air will be drawn principally by convection but some of the air may be incidentally entrained towards the sides of the insert as a result of the operation of a blower which otherwise seeks to entrain air into the heat exchange passageway. The air then proceeds by convection up the sides and back of the insert and will find its way around guide plate  14 . As a result, the room air will undergo secondary heat exchange from contact with the exterior walls and panels of the insert, thereby further heating the room.  
         [0080]     The invention therefore achieves the objects of an insert having a significantly improved visual appearance when seated in a fireplace. The insert is also easy to install and provides an efficient heat exchange with the room air.  
         [0081]     It will be appreciated that while the preferred embodiment of the invention has been described, other variations may be practised within the scope thereof without departing from the principles of the invention.
The invention provides an insert assembly to convert an existing fireplace hearth into a gas burning fireplace and a method for installing the insert assembly while conveying the appearance of a wood burning fireplace. The insert assembly comprises legs removably attachable to the base of the firebox for allowing the insert to be installed higher into the hearth. The inner walls of the firebox are coloured so as to camouflage the structure of the assembly in the hearth and a decorative fender mimics a wood burning grill. Where the insert includes a heat exchanger, a guide plate is provided at the top of the insert to ensure that air exiting the heat exchange outlet at the top of the insert is directed into the room.