Abstract:
An adapter is provided for placement within a furnace filter bay having a flow of air therethrough. The filter bay is for receiving a furnace filter. The adapter includes a filter abutment face for abutment with at least a portion of the furnace filter, a mounting face parallel to the flow of air and attachment means permitting removable attachment of the adapter to the furnace filter bay. The adapter allows filters of smaller depth than the filters originally designed for use within the filter bay to be used, thereby eliminating the need for purchasing the original filters. A brace is also provided for the same purpose. A kit is described that includes the adapter and/or brace, along with instructions for installation thereof within the filter bay.

Description:
CROSS REFERENCE TO RELATED APPLICATION 
     This application claims the benefit of U.S. Provisional Patent Application No. 61/098,411, filed Sep. 19, 2008, the disclosure of which is incorporated by reference herein in its entirety. 
    
    
     FIELD OF THE INVENTION 
     The invention relates to adapters and braces for insertion within large format furnace filter bays (those that accommodate furnace filters having a depth of 3-6″) to allow use of a conventional filter (typically having a depth of about 1″) in the bay. The adapters and braces are designed to be easily inserted and removed and may be customized in size to be suitable for use in a number of large format filter bays. 
     BACKGROUND 
     Heating and ventilation equipment utilizing a pressurized flow of air, for example forced air furnaces for use in heating residential and light commercial spaces, are equipped with a filter for use in removing airborne contaminants such as dust, debris, pollen, VOC&#39;s etc. from the air stream used to ventilate the space. Suitable filters for use in these applications are commonly described as furnace filters. Conventional furnace filters are approximately 1″ in depth and are sold under a number of brand names; examples of conventional furnace filters are sold by 3M and its subsidiaries, such as 3M Canada, under the FILTRETE® brand name. In recent years, there has been a trend towards use of large format (having a depth of 3-6″) furnace filter bays on new furnace installations. These bays are non-standard in size and accommodate a variety of different proprietary furnace filters. These proprietary large format filters are often expensive and can be difficult to find from retail suppliers. As a result, it would be desirable for owners of furnaces equipped with large format filter bays to be able to simply and easily retrofit those bays to accommodate conventional 1″ furnace filters. It would be further desirable to provide the means to retrofit the filter bay as part of a kit for sale along with or in addition to the furnace filters. 
     U.S. Pat. No. 6,716,267, filed Oct. 18, 2001, discloses a multi-position furnace filter rack comprising a spring-loaded frame of adjustable dimensions. This furnace filter rack is relatively complex and would tend to make the price of a kit prohibitively expensive relative to simply purchasing the proprietary large format filters 
     Referring to  FIG. 2 , another proposed solution is to provide a set of angle brackets shown at  200  and  202  and to pop-rivet the angle brackets  200  and  202  in place in the furnace filter bay. This permanently modifies the furnace filter bay so that it can be used with 1″ filters thereafter. A problem with such a solution, however, is that a skilled tradesperson is typically required to pop-rivet or permanently fasten a set of angle brackets into place in the filter bay and so it is typically relatively expensive and/or difficult to implement such a solution. 
     Accordingly, there remains a need for a new solution to permit a furnace filter bay that has been made for a first larger size of air filter to accommodate a smaller second size of air filter. 
     SUMMARY OF THE INVENTION 
     According to an embodiment of the present invention, there is provided an adapter for placement within a furnace filter bay having a flow of air therethrough, the filter bay for receiving a furnace filter, the adapter comprising: a filter abutment face for abutment with at least a portion of the furnace filter; a mounting face parallel to the flow of air; and, attachment means permitting removable attachment of the adapter to the furnace filter bay. 
     According to another embodiment of the present invention, there is provided a furnace filter brace for placement within a furnace filter bay having a flow of air therethrough, the filter bay for receiving a furnace filter, the brace comprising: a filter abutment face for abutment with at least a portion of the furnace filter; a mounting face for abutment against an interior portion of the filter bay; and, a first variable-length member diagonally or horizontally between the filter abutment face and filter bay abutment face. 
     According to yet another embodiment of the present invention, there is provided a kit for adapting a furnace filter bay to receive a furnace filter, the filter bay having a flow of air therethrough, the kit comprising: an adapter for placement within the furnace filter bay comprising a filter abutment face for abutment with at least a portion of the furnace filter and a mounting face parallel to the flow of air; the adapter including attachment means permitting removable attachment of the adapter to the furnace filter bay; and, instructions for attachment and placement of the adapter within the filter bay. 
     According to still another embodiment of the present invention, there is provided a kit for adapting a furnace filter bay to receive a furnace filter, the filter bay having a flow of air therethrough, the kit comprising: a brace for placement within the furnace filter bay comprising a filter abutment face for abutment with at least a portion of the furnace filter, a mounting face for abutment against an interior portion of the filter bay and a first variable-length member diagonally or horizontally between the filter abutment face and filter bay abutment face; and, instructions for placement of the brace within the filter bay. 
     In one embodiment, two adapters may be removably attached to the upper and lower (or left and right) interior surfaces of the furnace filter bay proximate the rear or downstream end thereof, just upstream of the filter. The filter is pushed toward the rear of the bay by the flow of air through the filter bay and the adapters prevent the filter from falling forward when the furnace fan cycles off. In another embodiment, two adapters may be removably attached to the upper and lower (or left and right) interior surfaces of the furnace filter bay proximate the front or upstream end thereof, just downstream of the filter. The filter is pushed towards the adapters by the flow of air through the filter bay and the adapters also prevent the filter from falling forward when the furnace fan cycles off. 
     The adapters may comprise a generally L-shaped piece that is magnetically or adhesively secured to the upper and lower interior surfaces of the bay to hold the filter in place at its top and bottom edges. The cross sectional shape may be square, triangular, semi-circular, quarter round, T-shaped, etc. and the material of construction may be thermoplastic, paper, polyurethane foam, or galvanized steel. A channel may be included for receiving the top and bottom edges of the filter. The mounting face of the adapter may be on a mounting portion of the adapter and a magnet channel face may be provided on an opposite side of the mounting portion from the mounting face. A magnet channel may be provided on the mounting portion, for example on the magnet channel face, and the attachment means may comprise a magnet inserted in the channel. The filter abutment face may alternatively be provided as part of a rectangular frame with top and bottom (and/or left and right) flanges having the mounting face for attachment to the filter bay. The adapters may be provided across the full width of the filter bay, or cover just a portion of the width and may be customized to a desired filter size, for example by cutting to size upon installation. 
     A single brace may be used as an alternative to the adapter. The brace is not attached to any interior surface of the filter bay, but generally comprises a filter abutment face abutted against a top front edge of the filter, a mounting face abutted against a bottom interior front edge of the filter bay, and a variable-length member oriented diagonally between the two faces. An X-shaped cross section can also be provided by adding a second brace configured in the reverse to the first brace just described and pivotally attaching the two at a central intersection of the variable-length members. In another variation, the filter abutment face is on a rectangular frame and the variable-length member extends horizontally between the bottom of the frame and the mounting face abutting the bottom front edge of the filter bay to form a generally L-shaped insert for the filter bay. In yet another variation, there are two such variable-length members extending from a first rectangular frame, located adjacent the filter when installed in the filter bay, and a second rectangular frame for abutment against a front interior edge or edges of the filter bay. 
     The filter abutment face of the adapter and/or the filter abutment face of the brace may be keyed with a pattern complementary to a pattern on at least a portion of the furnace filter in order to prevent or impede interchangeability of non-keyed filters with the adapters and/or braces of the present invention. 
     In yet another embodiment, the aforementioned adapters or braces are provided as component pieces packaged in a kit with instructions for assembly and installation in a furnace filter bay. The instructions may include a direction to cut or size components of the adapter according to the interior dimensions of the filter bay and/or furnace filter. The kit may include one or more conventional furnace filters. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       Having summarized the invention, preferred embodiments thereof will now be described with reference to the accompanying figures, in which: 
         FIG. 1  shows an overall perspective view of a furnace with a prior art filter bay, showing a 4″ deep filter being removed therefrom in a semi-exploded view; 
         FIG. 2  shows a side view of the filter bay with L-shaped angles pop-riveted to the top and bottom of the filter bay adjacent a 1″ filter pushed up against a downstream end of the filter bay; 
         FIG. 3   a  is a side view of the filter bay shown in  FIG. 1 , showing a set of adapters installed so that the filter bay can accommodate a filter having a second depth, in accordance with an embodiment of the present invention; 
         FIG. 3   b  is a front view of the set of adapters and filter shown in  FIG. 3   a;    
         FIG. 3   c  is a perspective view of the set of adapters and filter shown in  FIG. 3   a;    
         FIG. 4  is a front view of a variant of the set of adapters shown in  FIG. 3   b;    
         FIG. 5   a  is a sectional side view of an alternative to the adapter shown  FIG. 3   a , having a hollow triangular cross-sectional shape; 
         FIG. 5   b  is a sectional side view of another alternative to the adapter shown  FIG. 3   a , having a filled triangular cross-sectional shape; 
         FIG. 5   c  is a sectional side view of yet another alternative to the adapter shown  FIG. 3   a , having a filled quarter-circular cross-sectional shape; 
         FIG. 5   d  is a sectional side view of yet another alternative to the adapter shown  FIG. 3   a , having a filled semi-circular cross-sectional shape; 
         FIG. 5   e  is a sectional side view of yet another alternative to the adapter shown  FIG. 3   a , having a hollow square cross-sectional shape; 
         FIG. 5   f  is a sectional side view of yet another alternative to the adapter shown  FIG. 3   a , having a filled square cross-sectional shape; 
         FIG. 5   g  is a sectional side view of yet another alternative to the adapter shown  FIG. 3   a , having a T-shaped cross-sectional shape; 
         FIG. 6  is a perspective view of a variant of the adapters shown in  FIG. 3   a , configured to extend vertically in the filter bay; 
         FIG. 7   a  is a perspective view of an adapter in accordance with another embodiment of the present invention; 
         FIG. 7   b  is a perspective view of another adapter in accordance with yet another embodiment of the present invention; 
         FIG. 7   c  is a perspective view of another adapter in accordance with yet another embodiment of the present invention; 
         FIG. 7   d  is a perspective view of another adapter in accordance with yet another embodiment of the present invention; 
         FIG. 8  is a view of a kit for use in making a filter bay accommodate the filter having the second depth shown in  FIG. 3   a;    
         FIG. 9  is a side view of a diagonal brace within a filter bay with a 1″ filter in accordance with yet another embodiment of the present invention; 
         FIG. 10  is a side view of a brace incorporating two of the braces shown in  FIG. 9  in accordance with yet another embodiment of the present invention; 
         FIG. 11  is a perspective view of another brace in accordance with another embodiment of the present invention; 
         FIG. 12  is a perspective view of a variant of the brace in accordance with another embodiment of the present invention; and 
         FIGS. 13A-C  show another kit for use in making a filter bay accommodate the filter having the second depth shown in  FIG. 3   a.    
     
    
    
     DETAILED DESCRIPTION 
     Reference is made to  FIG. 1 , which shows an item of ventilation equipment suitable for use in HVAC systems, exemplified by a furnace  10 , and associated ducting  12 , including an inlet duct  12   a  and an outlet duct  12   b . On the inlet duct  12   a , there is a filter bay, exemplified by a furnace filter bay  14 , which is configured to hold a filter suitable for use in HVAC equipment, exemplified by a first furnace filter  16 . During operation of the furnace  10 , a flow of air  18  passes through the inlet duct  12   a , through the furnace  10  and out through the outlet duct  12   b  for distribution as desired. The flow of air  18  therefore passes through the furnace filter bay  14 . The furnace filter bay  14  has a rectangular cross-sectional shape and may thus have a set of filter bay walls  20  including first, second and third filter bay walls  20   a ,  20   b  and  20   c . In embodiments wherein the inlet duct  12   a  extends horizontally, the first, second and third filter bay walls  20   a ,  20   b  and  20   c  may be referred to as an upper wall, a lower wall and a side wall, respectively. The surfaces of the first, second and third walls  20   a ,  20   b  and  20   c  may be generally parallel to the flow of air  18  that, during use, passes through the inlet duct  12   a  and therefore through the furnace filter bay  14 . 
     The furnace filter bay  14  includes a first filter bay upstream retainer  22 , a second filter bay upstream retainer  24 , a first filter bay downstream retainer  26  and a second filter bay downstream retainer  28 , for retaining the first furnace filter  16  in position in the inlet duct  12   a . The filter bay upstream and downstream retainers  22 ,  24 ,  26  and  28  may all be members of a common base  30  that is mounted to the inlet duct  12   a . The base  30  may form the upper wall  20   a , lower wall  20   b  and side wall  20   c  of the furnace filter bay  14 . 
     The furnace filter  16  is installable into the furnace filter bay  14  by means of a furnace filter access aperture  34  in the inlet duct  12   a . An edge wall shown at  36  of the housing of the first furnace filter  16  may substantially occupy the area of the furnace filter access aperture  34  so as to inhibit drawing in ambient air through therethrough into the inlet duct  12   a  during use. Alternatively, a filter bay door (not shown) may be provided and installed over the access aperture  34  once the filter  16  is inserted. 
     During use, the flow of air  18  is cleaned at least partially of entrained particulate matter (and/or other contaminants) by the first furnace filter  16 . The first furnace filter  16  has a first depth D 1 . The first furnace filter  16  may be of a non-standard, uneasily obtainable size, such as, 14″(height)×25″(width)×4″(depth). In particular, the depth D 1  (which may nominally be 4″ as noted) may be non-standard and uneasily obtainable. 
     Persons skilled in the art recognize that furnaces, furnace filter bays and furnace filters are specific examples of items suitable for use in HVAC systems. HVAC systems amenable to use of the present invention need not necessarily include a heating component. As used herein, the terms “furnace”, “furnace filter bay”, “furnace filter”, etc. are meant to denote, in a non-limiting sense, equipment suitable for use in HVAC systems that may or may not include a heating component. 
     Reference is made to  FIG. 3   a , which shows the furnace filter bay  14  with a set of adapters  38  installed therein, including a first adapter  38   a  and a second adapter  38   b , which configure the furnace filter bay  14  for receiving a second furnace filter  40  having a second depth D 2 , in accordance with an embodiment of the present invention. The second depth D 2  is less than the first depth D 1 . More particularly, the second depth D 2  may correspond to a second furnace filter  40  that is relatively more standard and is relatively more easily obtainable than the first furnace filter  16  ( FIG. 1 ). For example, the second furnace filter  40  may be 14″(height)×25″(width)×1″(depth), which is a commonly available size of filter. 
     Each adapter  38  includes a filter abutment face  42 , which is positioned to abut the upstream face, shown at  44 , of the second furnace filter  40 , and a mounting face  46 , the surface of which is parallel to the flow of air  18  that passes through the furnace filter bay  14  during use. In the embodiment shown in  FIG. 3   a , each adapter  38  is made up of a filter abutment portion  47   a , which has the filter abutment face  42  thereon, and a mounting portion  47   b  which has the mounting face  46  thereon. The mounting face  46  is used to mount the adapter  38  to a filter bay wall  20 , such as, for example, the upper wall  20   a . The mounting face  46  and the filter abutment face  42  may be generally perpendicular to each other. 
     An attachment means  48  is provided on the mounting face  46  for mounting the adapter  38  to a filter bay wall  20  (e.g. the upper wall  20   a ). The attachment means  48  may removably join the adapter  38  to the filter bay wall  20  so that at some point, a user can remove the adapter  38  if desired. For example, the user may want to remove the adapter  38  in order to reinstall a first furnace filter  16  ( FIG. 1 ) into the furnace filter bay  14 . Also, by making the adapter  38  removably attachable to the furnace filter bay  14 , the furnace filter bay  14  is able to accommodate multiple depths of furnace filter, such as the first furnace filter  16 , the second furnace filter  40 , and a third furnace filter having a third depth (not shown). Additionally, making the adapter  38  removably attachable to the furnace filter bay  14  permits the position of the adapter  38  to be adjusted if necessary after being initially installed. Use of a removable attachment means  48  also permits easy installation without specialized skills or tools. The attachment means  48  may be any suitable type of attachment means, such as, for example, a magnetic strip or a layer of adhesive. The term ‘adhesive’ is to be understood broadly as meaning any kind of composition that is applied to the mounting face  46  for joining the mounting face  46  to the filter bay wall  20 , such as a pressure sensitive adhesive (PSA). A preferred adhesive is of the type used on removable adhesive tape. 
     Preferably, the adapter  38  is positioned for abutment with the upstream side  44  of the second furnace filter  40 , while the pre-existing first and second filter bay downstream retainers  26  and  28  abut and retain the downstream side  50  of the second furnace filter  40 . During use, the flow of air  18  exerts a force on the second furnace filter  40  in the downstream direction. By providing the adapter  38  to abut the upstream side  44  of the second furnace filter  40 , and by using the pre-existing first and second filter bay downstream retainers  26  and  28  to abut the downstream side  50  of the second furnace filter  40 , the first and second adapters are not called upon to hold the second furnace filter  40  against the force from the flow of air  18 . Thus, the adapter  38  is subject to a relatively low degree of stress and has a relatively lower likelihood of being torn loose from the furnace filter bay  14 . This reduces the need for relatively strong attachment between the adapter  38  and the associated filter bay wall  20 , which in turn permits the use of a relatively weak attachment means  48 . An advantage of using a relatively weak attachment means  48  is that, in some embodiments, it may be relatively inexpensive. Another advantage is that a weak attachment means  48  permits the adapter  38  to be more easily removed from the furnace filter bay  14  if desired. 
     Additionally, when the adapter  38  is positioned to cooperate with the first and second filter bay downstream retainers  26  and  28  to hold the second furnace filter  40 , the second furnace filter  40  is positioned immediately adjacent the downstream end of the furnace filter bay  14 , shown at  52 . As a result, any ambient air that is inadvertently drawn into the inlet duct  12   a  through the furnace filter bay aperture  34  ( FIG. 3   c ) during use of the furnace  10  is drawn in upstream from the second furnace filter  40  and therefore is cleaned by the second furnace filter  40 . 
     Referring to  FIGS. 3   b  and  3   c , each of the first and second adapters  38   a  and  38   b  may extend across substantially the entirety of the width of the second furnace filter  40 . Alternatively however, referring to  FIG. 4 , it is possible for each of the first and second adapters  38   a  and  38   b  to be relatively short, and for there to be provided an additional two adapters  38   c  and  38   d , each of which may be similar to the first and second adapters  38   a  and  38   b  respectively. 
     It will be noted that the first and second adapters  38   a  and  38   b  shown in  FIGS. 3   a - 3   c  may be identical and may simply be oriented as necessary for use on the upper and lower filter bay walls  20   a  and  20   b . Similar, the adapters  38   a ,  38   b ,  38   c  and  38   d  shown in  FIG. 4  may be identical and may simply be oriented as necessary for use on the upper and lower filter bay walls  20   a  and  20   b.    
     Each adapter  38  may have any suitable cross-sectional shape. For example, each adapter  38  may have a generally L-shaped cross-sectional shape and may be made from angle bracket. Other examples of cross-sectional shape are shown in  FIGS. 5   a - 5   g . In each figure, the adapter  38  is shown with an attachment means  48 . Thus, the cross-sectional shape of the adapter  38  may be a hollow shape ( FIGS. 5   a  and  5   e ) or a filled shape ( FIGS. 5   b ,  5   c ,  5   d  and  5   f ). The cross-sectional shape may, for example, be triangular ( FIGS. 5   a ,  5   b ), square ( FIGS. 5   e ,  5   f ), quarter-circular ( FIG. 5   c ), or semi-circular ( FIG. 5   d ). As can be seen in relation to the embodiment shown in  FIG. 5   d , the filter abutment face  42  of the adapter  38 , which is used to abut the second furnace filter  40  need not be planar ( FIG. 5   d ). As can be seen in relation to the embodiments shown in  FIGS. 5   d  and  5   g , the filter abutment face  42  need not extend along the entire height of the adapter  38 . 
     Reference is made to  FIG. 6 , in which two adapters  38   e ,  38   f  are provided vertically within the interior of the filter bay. Adapter  38   e  is mounted to the interior wall  20   c  of the filter bay and adapter  38   f  is mounted to the removable door (not shown) of the filter bay. The adapters  38   e ,  38   f  are otherwise identical to the adapters as previously described. 
     It has been shown in the figures to provide two or more adapters  38  for installation in the furnace filter bay  14  for retaining the second furnace filter  40 . It is alternatively possible to provide a single adapter (not shown) that is configured to retain the second furnace filter  40  in position without the need for any second or subsequent adapter. Such a single adapter is configured to retain the second furnace filter  40  in cooperation with two of the furnace filter bay retainers (e.g. the two downstream retainers  26  and  28 ). Such a single adapter preferably includes a filter abutment face that extends along a sufficient portion of the height or width of the second furnace filter to substantially prevent the second furnace filter from being inadvertently moved out of position. Preferably, such a single adapter is configured to abut portions of the housing of the second furnace filter  40  so as not to significantly impact on the air flow through the second furnace filter  40 . 
     Reference is made to  FIG. 7   a , which shows an adapter  70  in accordance with another embodiment of the present invention. The adapter  70  includes a filter abutment portion  71   a  and a mounting portion  71   b . The filter abutment portion  71   a  includes a filter channel  72 , which has therein a first filter abutment face  74  and a second filter abutment face  76 . The first and second filter abutment faces  74  and  76  may be configured to abut the upstream and downstream faces  44  and  50  of the second furnace filter  40  respectively. The mounting portion includes a mounting face  78  that has an attachment means  80  thereon, which may be similar to the attachment means  48  on the adapter  38  shown in  FIGS. 3   a - 3   c . The filter channel  72  may extend along one edge of the mounting portion  71   b . In this way, the adapter  70  may be installed in the furnace filter bay  14  with the filter channel  72  proximate the downstream end  52  ( FIG. 3   a ) of the furnace filter bay  14 , either in abutment with the downstream retainers  26 ,  28  or spaced apart therefrom. 
     Reference is made to  FIG. 7   b , which shows an adapter  82 , which may be similar to the adapter  70  ( FIG. 7   a ), and which has a filter abutment portion  83   a  and a mounting portion  83   b . The filter abutment portion  83   a  includes a filter channel  84 , which has first and second filter abutment faces  86  and  88  for abutment with the upstream and downstream faces  44  and  50  of the second furnace filter  40  respectively, and which may be similar to the filter channel  72  ( FIG. 7   a ). The filter channel  84  may be centrally positioned relative to the mounting portion  83   b  instead of being positioned along one edge of the mounting portion  83   b  (or potentially offset from center). The mounting portion  83   b  includes a mounting face  90  with an attachment means  92  thereon, which may be similar to the mounting face  78  and attachment means  80  ( FIG. 7   a ). 
     Reference is made to  FIG. 7   c , which shows an adapter  94  which may be similar to the adapter  82  ( FIG. 7   b ) and includes a filter abutment portion  95   a  and a mounting portion  95   b . The filter abutment portion  95   a  may include a filter channel  96  which may be similar to the filter channels  72  and  84  ( FIGS. 7   a  and  7   b ), and which has first and second filter abutment faces  98  and  100 . The mounting portion  95   b  includes a mounting face  102  which engages the filter bay wall  20 . The mounting portion  95   b  further includes a magnet channel face  104  which is opposed to the mounting face  102  and is separated from the mounting face  102  preferably by only a thin layer of material. This thin layer of material is preferably permeable to magnetic flux. The magnet channel face  104  has thereon a magnet channel  106  for holding a magnet  108 , which makes up an attachment means  110  for holding the adapter  94  in position in the furnace filter bay  14 . The magnet  108  may have any suitable cross-sectional shape and may be elongated, running the length of the magnet channel  106 . Alternatively, there may be a plurality of magnets  108  that are provided in the magnet channel  106 . The magnet channel  106  may be immediately adjacent the filter channel  96  as shown. The magnet channel  106  may include a set of retaining ribs  112  to assist in retaining the magnet  108 . 
     While a magnet  108  has been provided as the attachment means  110  in the embodiment shown in  FIG. 7   c , it is optionally possible to also provide an adhesive on the mounting face  102  to cooperate with the magnet  108  to attach the adapter  94  to a filter bay wall  20 . 
     Referring to  FIG. 7   d , an alternative embodiment of an adapter  194  is shown, that is similar to the adapter  94  ( FIG. 7   c ), but has only a first filter abutment face  198  and no second filter abutment face. The adapter  194  is positioned such that the filter abutment face  198  is adjacent the upstream edge of the filter to lodge the filter against the downstream retainers of the filter bay in a manner as previously described with reference to  FIGS. 3   a - c . A magnet channel  206  is formed between the upstream side of the filter abutment face  198  and a protrusion  202 , each of which include a lip  210 ,  204  that overhangs the channel to prevent the magnet  208  from popping out of the channel. The magnet  208  is slid into the magnet channel  206  to a desired position for securing the mounting portion  195  of the adapter  194  within the filter bay. The magnet  208  need not necessarily run along the entire length of the channel  206  and may be pre-cut or cut by an installer of the adapter  194  to an appropriate length for positioning at a desired location. The adapter  194  may optionally be provided with end caps  212  that snap over or into the ends of the adapter to prevent the magnet or magnets  208  from sliding out of the channel  206 . The end caps  212  also enhance safety of the adapter  194  by reducing the likelihood of any exposed sharp edges. The end caps  212  can optionally be marked with brand imagery and/or an air flow direction arrow to aid in proper installation of the adapter  194 . The magnet  208  may also be so marked. 
     The filter channel  96  may be centrally positioned, or offset, relative to the mounting portion  95   b  instead of being positioned along one edge of the mounting portion  95   b , in the same manner as described with reference to  FIG. 7   b.    
     Referring to  FIG. 8 , at least one adapter  38  may be provided together with a set of instructions shown at  114  containing instructions for attachment and placement of the adapter  38 ,  70 ,  82 ,  94  or  194  within the furnace filter bay  14  ( FIG. 3   a ), as a kit  116  for adapting a furnace filter bay to receive the second furnace filter  40 . The kit  116  may include a plurality of adapters  38 ,  70 ,  82 ,  94  or  194  instead of just one. The kit  116  may further include the second furnace filter  40 . 
     The set of instructions  114  may include an instruction  118  to trim the adapter  38  (or each of the adapters if more than one is provided and needs trimming) to a length commensurate with a width or height of the second furnace filter  40  or commensurate with the width or height of the furnace filter bay  14 . The set of instructions  114  may further include an instruction  120  to attach the attachment means to the adapter in embodiments wherein the attachment means is not provided on the adapter already. In the case where the kit  116  includes the adapter  94  or  194 , the instruction  120  may include an instruction to insert the magnet (or magnets) into the magnet channel and optionally to cut the magnet (or magnets) to an appropriate length and/or to position the magnets within the channel in order to provide sufficient support, stability and magnetic attachment. The set of instructions  114  may further comprise an instruction  122  to attach the adapter to the furnace filter bay  14  ( FIG. 3   a ) at a selected position. The instruction  122  may include an instruction  124  to place the adapter proximate the downstream end  52  ( FIG. 3   a ) of the furnace filter bay  14  so that it is positioned for abutment with at least the upstream face  44  of the second furnace filter  40 . The set of instructions  114  may further include an instruction  126  to insert the second furnace filter  40  at the downstream end  52  ( FIG. 3   a ) of the furnace filter bay  14 . Where the adapter comprises a filter channel  72 ,  84  or  96 , the set of instructions  114  may further include an instruction  128  to insert the second filter  40  within the filter channel as previously described with reference to  FIGS. 7   a - c.    
     Reference is made to  FIG. 9 , which shows a furnace filter brace  130  in accordance with another embodiment of the present invention. The furnace filter brace  130  includes a filter abutment member  132 , a filter bay abutment member  134  and a variable-length member  136  that extends between the filter abutment member  132  and the filter bay abutment member  134 . The filter abutment member  132  includes a filter abutment face  138  for abutment with the second furnace filter  40 . The filter bay abutment member  134  includes a furnace filter bay abutment face  140  for abutment with a suitable surface, such as the second filter bay upstream retainer  24 . In the embodiment shown in  FIG. 9 , the furnace filter brace  130  extends diagonally between the second filter bay upstream retainer  24  and the upper edge of the upstream face  44  of the second furnace filter  40 . To permit the furnace filter brace  130  to hold the second furnace filter  40  in position, the furnace filter brace  130  is variable in length by means of the variable-length member  136  so that it wedges between a first corner made up of the upper edge of the upstream face  44  of the second furnace filter  40  and the upper filter bay wall  20   a , and a second corner made up of the second filter bay upstream retainer  24  and the lower filter bay wall  20   b.    
     In an alternative embodiment of an installation method, the brace  130  may be installed horizontally within the filter bay  14  at a top or bottom thereof. Two braces  130  may be provided horizontally at the top and bottom of the filter bay  14 . When the brace  130  is installed at the top of the filter bay  14 , the first corner is made up of the upper edge of the upstream face  44  of the second furnace filter  40  and the upper filter bay wall  20   a , and the second corner is made up of the second filter bay upstream retainer  24  and the upper filter bay wall  20   a . When the brace  130  is installed at the bottom of the filter bay, the first corner is made up of the lower edge of the upstream face  44  of the second furnace filter  40  and the lower filter bay wall  20   b , and the second corner is made up of the second filter bay upstream retainer  24  and the lower filter bay wall  20   b.    
     The variable-length member  136  may be variable in length by any suitable means. For example, the variable-length member  136  may be made from first and second segments  142  and  144 , which are retractable and extensible with respect to each other, preferably telescopically, and a biasing member  146  that urges the first and second segments to extend. The biasing member  146  may be, for example, a compression spring positioned inside the first segment  142 . The rest length of the variable-length member  136  may be sufficiently long that it requires some amount of compression to fit in its position between the second furnace filter  40  and the second filter bay upstream retainer  24 . This causes the variable-length member to exert a force on the second furnace filter  40 , to hold the second furnace filter  40  in place. 
     Optionally and preferably, the filter abutment member  132  and the filter bay abutment member  134  are each pivotally connected to a respective end of the variable-length member  136  at pivot joints  148  and  150  respectively. Alternatively, the filter abutment member  132  and the filter bay abutment member  134  may be fixedly connected to the variable-length member  136 . 
     Reference is made to  FIG. 10 , which shows a furnace filter brace  152  that may comprise two furnace filter braces  130 , which may be pivotally connected together, and thus includes first and second filter abutment members  132 , individually identified at  132   a  and  132   b , first and second filter bay abutment members  134 , individually identified at  134   a  and  134   b , and first and second variable-length members  136 , individually identified at  136   a  and  136   b . The first filter abutment member  132   a  abuts the upper edge of the upstream face  44  of the second furnace filter  40 . The first filter bay abutment member  134   a  abuts the second filter bay upstream retainer  24 . Thus, the first variable-length member  136   a  may extend diagonally between the second filter bay upstream retainer  24  and the second furnace filter  40 . The second filter abutment member  132   b  abuts the lower edge of the upstream face  44  of the second furnace filter  40 . The second filter bay abutment member  134   b  abuts the first filter bay upstream retainer  22 . The second variable-length member  136   b  extends diagonally between them. 
     The first and second variable-length members  136   a  and  136   b  may be pivotally connected to each other as shown at a pivot joint  154 . 
     Reference is made to  FIG. 11 , which shows a furnace filter brace  156  in accordance with another embodiment of the present invention. The furnace filter brace  156  includes a filter abutment member  158  having a filter abutment face  159 , a filter bay abutment member  160  having a filter bay abutment face  161 , and first and second variable-length members  162 , individually shown at  162   a  and  162   b . The filter abutment member  158  is sized so as not to appreciably occlude the surface area of the second filter  40  available for air flow so as not to increase the pressure drop across the second filter significantly. 
     The filter abutment member  158  may have any suitable configuration. For example, the filter abutment member  158  may be a substantially rectangular frame that is configured to abut the entire peripheral edge of the upstream face  44  of the second furnace filter  40 . The filter bay abutment member  160  may be an elongate strip that is configured to abut substantially the entirety of the second filter bay upstream retainer  24  ( FIG. 3   a ). Persons skilled in the art will recognize that the structure shown in  FIG. 11  may be inverted such that the filter bay abutment member  160  abuts the second filter bay upstream retainer  24  ( FIG. 3   a ) along the top edge of the filter bay rather than the bottom edge as shown. Each of the variable length members  162  may include first and second segments  164  and  166  that retract and extend telescopically, and a biasing member  168 , such as a compression spring, which is provided inside the first segment  164 , that urges the first and second segments to extend. 
     Similarly to the variable length member  136  shown in  FIG. 9 , it is preferable that the rest length of the first and second variable-length members  162  is such that they are compressed by some amount to fit between the second furnace filter bay retainer  24  and the second furnace filter  40 . 
     Reference is made to  FIG. 12 , which shows a furnace filter brace  170  that may be similar to the furnace filter brace  156  ( FIG. 11 ) and may include all the same structure as the furnace filter brace  156 , but may further include third and fourth variable-length members  162 , shown individually at  162   c  and  162   d , and a second filter bay abutment member  160   b  which may be similar to the first filter bay abutment member  160   a . The second filter bay abutment member  160   b  is configured to abut the first filter bay upstream retainer  22  ( FIG. 3   a ). 
     Reference is made to  FIGS. 13A-C , which show a kit  180  for adapting the furnace filter bay  14  ( FIG. 3   a ) to accommodate the second furnace filter  40 . The kit  180  may be similar to the kit  116  ( FIG. 8 ) except that instead of including one or more adapters  38 ,  70 ,  82  or  94 , the kit  180  ( FIG. 13 ) includes one or more braces  130  or  152 , or a brace  156 , or a brace  170  and a set of instructions  182  instead of the set of instructions  114 . The kit  180  optionally includes the second furnace filter  40 . 
     The set of instructions  182  instruct a user on the installation and operation of the included brace or braces. The set of instructions  182  may include an instruction  184  to insert the second furnace filter  40  at the downstream end  52  of the furnace filter bay  14  ( FIG. 3   a ). The set of instructions  182  may further include an instruction  186  to insert the brace into position. For embodiments wherein the included brace or braces are the braces  130  or  152 , the instructions  182  may further specify to insert the brace into position after inserting the second furnace filter  40  into position in the furnace filter bay  14 . For embodiments wherein the included brace is the brace  156  or  170 , the instructions  182  may further specify that the brace may optionally be inserted in the furnace filter bay  14  ( FIG. 3   a ) before or after the second furnace filter  40 . 
     It will be understood that the second furnace filter  40  may be held in place in the furnace filter bay  14  by a combination of different adapters, such as an adapter  38  along the upper edge of the second furnace filter  40 , and an adapter  94  along the bottom edge of the second furnace filter  40 . Furthermore, a combination of adapters and braces may be used. For example, an adapter  38  may be used to hold the bottom edge of the second furnace filter  40  and a brace  130  may be used to hold the top edge. Alternatively, a combination of different braces may be used to hold the second furnace filter  40  in position. 
     While the above description constitutes a plurality of embodiments of the present invention, it will be appreciated that the present invention is susceptible to further modification and change without departing from the fair meaning of the accompanying claims.