Patent Publication Number: US-9410731-B1

Title: Expandable drain pan

Description:
RELATED APPLICATIONS 
     This application is a continuation-in-part of my U.S. patent application Ser. No. 13/542,866, filed Jul. 6, 2012, entitled “Drop-front Drain Pan,” which in turn claims priority to my U.S. provisional patent application Ser. No. 61/504,767, filed Jul. 6, 2011, entitled “Drop-front Drain Pan,” the latter of which is referred to herein as “the provisional application.” Both related applications are herein incorporated by reference. 
    
    
     FIELD OF THE INVENTION 
     This invention relates to drain pans for air handling units, and more particularly, to secondary or overflow drain pans for forced air conditioning systems. 
     BACKGROUND OF THE INVENTION 
     As air passes over the evaporator coil inside an air handler, such as one used with a split air conditioning or heat pump system, condensate forms on the coil. This condensate descends from the coil into the primary drain pan inside the air handler. In case the primary pan overflows, contractors often install a secondary, or emergency, drain pan under the air handler. 
     A secondary drain pan is typically made of plastic or metal and is rectangular or round in shape. Common pan sizes range from 18″×46″ to 36″×60″ to 34″×79″. Such a pan typically has side walls that define a basin that contains a waterway that allows drainage to exit through a drainage hole. The secondary pan rests on a platform or hangs under suspended equipment. 
     Secondary drain pans should be maneuverable enough to fit through attic or crawlspace doors. For cost, handling, and code considerations, plastic pans are generally made from a minimum 0.065″ thick material, and sturdier pans may be 0.125″ thick, or more. Sheet metal pans generally have a minimum thickness of 0.0236″ (24 gage). 
     A variety of methods and materials, some referred to as risers, are employed in the field in order to elevate the installed equipment above the level of any water that may collect in the pan. Equipment may be elevated further to provide proper drainage pitch for the primary drain line and easy access to equipment panels. This elevation is achieved by using substantial risers, by constructing a platform under the drain pan, or by hanging the unit from the ceiling trusses. As discussed in my patent application Ser. No. 11/320,992, filed Dec. 29, 2005, one improvement to the art is a drain pan with integrated risers that provide structural support for the air handler. When formed of plastic, that pan requires thicker material than ordinary pans in order to meet structural requirements and to withstand potentially high attic temperatures (140° F.). Yet the pan still must be set on a plywood platform for support. Distributors and contractors must purchase and carry a variety of pan types and sizes in order to meet the needs of different installations. There is a need in the art for a drain pan that is adjustable to fit a range of equipment sizes and installation configurations. 
     SUMMARY 
     An expandable secondary condensate drain pan is provided to capture any condensate that overflows from a primary drain pan of an air handling unit mounted above the drain pan. The drain pan, which may be thermoformed and unibody, comprises a drainage basin formed by sidewalls that extend upwardly around a perimeter of the drain pan from a base. An expansion section, which allows a section of the base and corresponding sections of the sidewalls to be expanded or compressed, may be located toward the middle of the pan or along a side of the pan. When located along a side of the drain pan, the base of the expansion section may be stepped such that the base at the side of the pan is higher than the base toward the center of the pan. A stepped base allows drainage to cascade toward the center of the pan and away from the side of the pan. The expansion section may be flexible or convertible and operative to configure the drain pan between commonly used drain pan sizes, permitting a contractor to carry only one drain pan that may function in multiple common pan sizes. 
     The expansion section may be configured to expand and collapse along a plurality of fold lines and may be further configured to minimize pooling of drainage through a variety of means. The expansion section may be strengthened against cracking by a relatively thin coating or film. Further, the secondary pan may contain risers and may be nestably stackable. 
     A method is also provided for installing a pre-manufactured expandable secondary condensate drain pan under an air conditioning unit comprises adjusting the size of the drain pan, placing the drain pan on a support, and setting an air conditioning unit on the drain pan. The method may further comprise placing anti-vibration pads or risers in the pan under the air conditioning unit. 
     These and many other embodiments and advantages of the invention will be readily apparent to those skilled in the art from the following detailed description taken in conjunction with the annexed sheets of drawings, which illustrate the invention. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       It will be appreciated that the drawings are provided for illustrative purposes and that the invention is not limited to the illustrated embodiment. For clarity and in order to emphasize certain features, not all of the drawings depict all of the features that might be included with the depicted embodiment. The invention also encompasses embodiments that combine features illustrated in multiple different drawings; embodiments that omit, modify, or replace some of the features depicted; and embodiments that include features not illustrated in the drawings. Therefore, it should be understood that there is no restrictive one-to-one correspondence between any given embodiment of the invention and any of the drawings. 
       Also, many modifications may be made to adapt or modify a depicted embodiment without departing from the objective, spirit and scope of the present invention. Therefore, it should be understood that, unless otherwise specified, this invention is not to be limited to the specific details shown and described herein, and all such modifications are intended to be within the scope of the claims made herein. 
         FIG. 1  is a perspective view of a typical prior art horizontal air handler installation. 
         FIG. 2  is a perspective view of a horizontal air handler installation using an embodiment of a new drop-front drain pan. 
         FIG. 3  is a perspective view of a convertible drop-front drain pan in a stepped configuration. 
         FIG. 4  is a perspective view of the convertible drop-front drain pan of  FIG. 3  in a standard or substantially flat configuration. 
         FIG. 5  is another perspective view of the convertible drop-front drain pan of  FIG. 3 , also in a standard configuration. 
         FIG. 6  is a side view of the convertible drop-front drain pan of  FIG. 3  in a standard configuration. 
         FIG. 7  is a side view of the convertible drop-front drain pan of  FIG. 3  in a stepped configuration. 
         FIG. 8  is a perspective view of a convertible drop-front drain pan that employs living hinges to enable modification between stepped and standard configurations. 
         FIG. 9  is a perspective view of a square drop-front drain pan. 
         FIG. 10  is a perspective view of a rectangular drop-front drain pan. 
         FIG. 11  is a perspective view of a drop front drain pan suspended from rafters. 
         FIG. 12  is a perspective view of drainage channels formed in the bottom surface of the drop-front drain pan. 
         FIG. 13  is a perspective view of a drop-front drain pan with channels for front-to-back support beams. 
         FIG. 14  is a side view of a drop-front drain pan with multiple notches for side-to-side support beams. 
         FIG. 15  is a rear view of a drop-front drain pan with multiple notches for front-to-back support beams. 
         FIGS. 16-18  are perspective views of the side of a drop front drain pan using various structures for mounting or attaching the drop front drain pan to support beams. 
         FIGS. 19-20  are side views of a drop front drain pan using various structures for providing additional support to the drop front drain pan to support beams. 
         FIG. 21  is a side view of a drop-front drain pan with a sloped back section. 
         FIG. 22  is a side view of a fully sloped drop-front drain pan. 
         FIGS. 23-24  are perspective views of a drop-front drain pan installed on wall brackets for use with a mini-split installation. 
         FIG. 25  is a top view of a drain pan with an expansion section. 
         FIG. 26  is a side view of the drain pan of  FIG. 25  with an expanded expansion section. 
         FIG. 27  is a side view of the expansion section of  FIG. 26 . 
         FIG. 28  is a top view of a drain pan with two expansion sections. 
         FIG. 29  is a top view of a drain pan with an expansion section along a side. 
         FIG. 30  is a side view of a drain pan with a stepped expansion section along a side. 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
       FIG. 1  illustrates a standard prior art secondary drain pan  10  mounted with and under a horizontal air handling unit  30  inside an attic. A sheet of plywood  15  placed on the framing joists or truss chords  20  forms a platform for the installation and provides a working area for the technician. The drain pan  10  is placed under the unit  30  in order to capture any leakage. Inside the unit  30  is a primary drain pan (not shown) that is equipped with one or more drainage outlets  58 . The secondary drain pan  10  is also equipped with one or more drainage outlets  57 . The unit  30  also may be equipped with p-traps (not shown) and condensate shut-off switches (not shown). Standard pans  10  typically have sides of 1.5″ to 3″ in height, with a small lip  12  around the upper perimeter, and substantially flat bottoms. The pan  10  may contain profiles (not shown) to add rigidity and yet allow drainage to reach the drainage outlet  57 . 
     Units  30  are usually placed on anti-vibration pads or tall risers  59  to elevate the unit  30  out of any water in the pan  10 . Elevation also helps with access to the unit  30  and removal of panels  33 . In addition, units are typically elevated further to provide proper drain line pitch. This elevation may be achieved through additional risers (not shown) or by elevating the entire platform  15  under the pan  10 . Newer drain pans  10  have integral risers to save contractors time and material. Upflow installations also use pans  10 , but with a smaller footprint. Alternatively, both the unit  30  and the secondary drain pan  10  may be hung from attic rafters or other framing (not shown). Drain pans  30  are either hung under the unit, not bearing the weight of the unit  30 , or are placed on a suspended platform. Metal pans may be favored when hanging, as they flex less. In all instances, the drain pan  10  remains stationary, held in place by supports, equipment, and completed ductwork  34 . 
       FIG. 2  depicts an installation similar to that shown in  FIG. 1 , but incorporates an embodiment of a novel and nestably-stackable secondary condensate drop-front drain pan  100  configured to capture any condensate that overflows from a primary drain pan of an air conditioning unit  30  that is mounted above the drain pan  100 . The drain pan  100  is, in one embodiment, thermoformed and unibody and, in another embodiment, made from sheet metal. The drain pan  100  comprises a drainage basin formed by a main or upper base or basin portion  110 , an auxiliary lower base, basin, or trough portion  120 , and sidewalls  119  that extend upwardly around a perimeter of the drain pan from both the upper base and trough portions  110  and  120 . The trough portion  120  is located along only one side (e.g., a front side corresponding with the panels  33  of the unit  30 , where a technician could most easily access it) of the drain pan  100 . The trough portion  120  is also stepped down relative to the main base portion  110 , vertically displaced from it by an at least steeply sloping or alternatively vertical transition section  150 . When the upper base portion  110  is positioned upon support beams  40 , the trough portion  120  descends along or near a side or end of the front support beam  40  and below a portion of the front support beam  40 . 
     The drop-front drain pan  100  is adapted to be fitted over and take its structural support from elevating elongated support beams  40 . Downwardly extending projections or lugs descending below the plane of the drainage basin form notches or saddles  126  for straddling or mounting the drain pan to the support beams  40 . In this instance, 2″ lumber of any desired height is placed on top of and attached to attic truss chords or other structural framing joists  20 . Specifically,  FIG. 2  depicts a 30″×60″ drain pan  100  placed on top of elongated support beams  40  made of 2″ lumber, with the pan  100  supported by and attached to the 2″ lumber through saddles or notches  126  formed on the sides of the pan  100 . The combination of 2″ lumber plus drain pan  100  is used in place of a plywood platform  15 , saving labor and material cost. Contractors may install longer pieces  40  of 2″ lumber in order to distribute the load of the unit  30  across more truss chords  20 . Attic insulation may be placed under the elevated drain pan  100 . The air handling or air conditioning unit  30 , with ductwork  34  attached, sits on top of anti-vibration pads  61 , which in turn sit on the drain pan  100 . The supports  40  and risers  61  do not interfere with condensate running to the front trough portion  120 . 
     The upper base portion  110  of the drain pan  100  may be shallower than standard pans  10 , with a sidewall height of about 1″-1.5″, because the upper area routes water to the trough portion  120  and does not hold water. The short sidewall height, along with the elevation provided by the 2″ lumber, allows for the use of short risers  61  under the unit  30 . The unit  30  has sufficient drain line pitch. Even with short risers  61 , the drop-front pan  100  allows access for the technician to open panels  33  and to connect a flexible gas pipe  55  under the unit  30  if needed. The drop-front trough portion  120  may have a primary or main drainage outlet  136  at its lower edge, and the sides of the trough portion  120  may be 1.5″-3″ high in order to meet code. The front trough portion  120  also serves as a lightweight tool rest for the technician. 
     As illustrated in  FIGS. 3-7 , a transitional section  150  of the pan  100  that transitions from upper base portion  110  to the auxiliary base or trough portion  120  may be gusseted on the sides to enable the pan  100  to lie flat. Contractors in the field will appreciate a pan  100  with a convertible transition portion  150  that can convert the pan  100  from a standard or conventional substantially flat configuration  176  ( FIG. 6 ) to a stepped drop-front configuration  174  ( FIG. 7 ) that aids elevated installations. The expandable and/or bendable properties of the gussets  160  at key points or fold lines allow the pan  100  to transform between a drop-front or stepped configuration  174  and a standard or substantially flat pan configuration  176 . Drainage channels (not shown) may run across the transition section or fold area  150 , so that water may still drain when the pan  100  is in a standard, substantially flat configuration. Or, the channels of the gussets  160  may be much shallower than illustrated. Similarly, in  FIGS. 25-30  the expansion section  150  allows an expandable drain pan  100  to transform from one size of “flat” drain pan to another size of “flat” drain pan. 
     Alternatively, as illustrated in  FIG. 8 , the pan  100  may bend along a line, such as a living hinge  170  or other discrete fold, or may bend over a wider portion of material, as in the case of corrugated material. It also is envisioned that the pan  100  may fold in ways and locations other than those illustrated. 
     The pan  100 , in the stepped configuration  174 , as illustrated in  FIGS. 3, 7, and 8 , may be used on top of a suspension frame or on 2″×8″ lumber for elevation. The sidewalls  119  are approximately 2″ high. As best illustrated in  FIG. 7 , at the top bend  152 , the gussets  160  are expanded to allow the downward bend of the trough portion  120 , while maintaining leak-free continuity in the sidewalls  119  between the main base section  110  and the trough or front base section  120 . At the bottom bend  154  of the trough portion  120 , where the trough portion  120  begins to extend forward, the gussets  160  are compressed to hold the trough portion  120  in its roughly horizontal position. The gussets  160  may be secured to maintain the pan  100  in this position. The top of the transition portion  150  may have no upper lip in order to allow flexibility. 
     Further, the trough portion  120  may be secured to framing joists  20  or support beams  40  to maintain the stepped configuration  174  and anchor the drain pan  100  to its support. Typically, however, the drop-front drain pan  100  will not be installed directly on the truss chords or framing joists  20 . Generally, elevating support beams  40  are contemplated to achieve a proper installation. 
     Support beams  40  may run left to right under the entire drain pan  100 , as shown in many of the drawings, or front to back within risers  113 , as shown in  FIGS. 3-5 , and within corresponding underside channels  105  as shown in  FIG. 13 . Also, as shown in  FIGS. 3-5 , for example, cones or other molded risers  140  may elevate the unit  30  and transfer the load to the supports  40 , or anti-vibration pads (not shown) or other materials may be used in place of the cones  140 . The cones  140  may be further constructed to enable screws to run through the cones  140  and into the supports  40  without allowing condensate to escape through the cones (not shown). Certain cones  140  may also be reinforced with foam or other material to make them stronger. 
     As depicted in  FIG. 7 , the front “drop” is about 5″, and the trough portion  120  is about 5″ from front to back. The height and depth of the trough portion  120  are modifiable, of course, and when modified will change the overall dimensions of the drop-front and flat modes of the pan  100 , as well as the difference in dimension between those two modes. A first drain hole  136  ( FIG. 10 ) may be placed front and center, or at another location as needed. Other backup drain holes  138  ( FIG. 10 ) may also be placed along various locations of the sidewall  119 . The upper base portion  110  of the drain pan  100  channels water to the trough portion  120 . As shown in  FIGS. 3-5 , risers or cones  140  may be integrally formed within the trough portion  120  in order to support an equipment unit  30  in the standard, substantially flat position. Risers  140  may be short or tall, and they may hold the equipment unit  30  level or at a slight angle in order to facilitate drainage from the primary pan (not shown) within the equipment unit  40 . 
       FIGS. 4 and 5  show the drain pan  100  of  FIG. 3  in its flat orientation, as if resting on plywood or a platform. If, for example, the pan in  FIG. 3  is 27″×64″ in folded position, the same pan in  FIG. 4  is 32″×64″ flat, with the same 2″ height for the sidewalls  119  and a drain hole (not shown) front and center. This one pan  100  covers multiple popular sizes. 
       FIG. 8  illustrates an alternative configuration in which the drain pan  100  folds along discrete lines or folds or (in the case of plastic) living hinges  170  and corresponding sidewall gussets  171 . 
       FIGS. 9 and 10  show two sizes (24″×24″ and 30″×60″, respectively) of a drop-front drain pan  100 . The pan  100  has a reinforcing lip  114  around the perimeter. The lip  114  includes lip extensions or lugs  116  that turn down, parallel to the sidewalls  119 , that form notches or saddles  126  ( FIG. 2 ) over the 2″ lumber beams  40 . As with many of the other embodiments, this pan  100  may be unibody (integrally formed) and nestably stackable with other pans  100 . Such characteristics reduce storage space and minimize manufacturing and material cost. 
       FIG. 11  illustrates a square drop-front pan  100  hanging from the rafters  22  via threaded rods  48  and  49 . Often, a pan will hang from just two rafters  22 , but the illustrated configuration spreads the load across four. Other structural supports may replace the threaded rods  48  and  49 , such as chains. Although not shown in  FIG. 11  for purposes of clarity, the unit  30  itself may be hung from the rods  48  and  49 , and any pan  100  suspended underneath, requiring its own support. Alternatively, a piece of plywood  15  may be suspended, with the pan  100  and unit  30  on top.  FIG. 11  also illustrates pieces of angle iron or channel strut  44  running from front to back, along the side of the pan, to provide added stability and allow the hanging members  48  and  49  to be attached at the far corners of the pan  100 , out of the way of ductwork and panel doors. The pan  100  may also be hung using 2″ lumber or another rigid material instead of strut  44 . 
       FIG. 12  shows the same square drop-front pan  100  with small channels  104  in the pan bottom to facilitate placement of anti-vibration pads and channel water to the front of the pan  100 . Also shown are ribs or ridges  106 , or raised areas of the pan bottom, to elevate the unit  30  slightly out of the water if no anti-vibration pads are employed. These channels  104  also form profiles that give the pan  100  added rigidity. 
       FIG. 14  illustrates a right side view of a pan  100  with multiple “saddles” or notches formed by downwardly extending projections or lugs in an extended, down-turned lip  116  to give the contractor more options for installation. Contractors are accustomed to 16″ and 24″ on center spacings, but given the sizes of popular drain pans, the actual spacing between support beams  40  may be closer to 20″. Accordingly, the pan  100  includes a first notch  42  adjacent, and formed in part by, the drop front trough portion  120 . Second, third, and fourth notches  62 ,  63 , and  64 , respectively, are spaced distances A, B, and C away (measured from the notch centers) from notch  42 . For example, distances A″, B″, and C″ may be 16″, 20″, and 24″ respectively. 
     A variety of additional features are contemplated to facilitate installation of the drain pan  100 . The drain pan  100  may be anchored, for example, by gravity, straps, lugs, saddles, screws through cones, zip ties, and other mechanisms, to support beams  40 , the existing truss chords or framing joists  20 , to a plywood surface  15 , or to a hanging or cantilevered frame. The weight of the unit  30  on top and the stability of ductwork and piping may also aid in keeping the pan  100  in place. 
       FIG. 16  illustrates a pan  100  with a short lip  114  around the perimeter of the sidewalls  119 . Here, no direct method of attachment is shown, but the back face  122  of the drop-front trough or lower base section  120  cozies up to the beam  40  in the front. A strap or other method of mechanical attachment may be used in the back to attach the lip  114  to the rear beam  40 . 
       FIG. 17  illustrates 2″ beams that pass through the sides of the pan  100  that are attached to the beams  40  via flaps or tabs  51 , rather than a saddle, protruding from the side of the pan  100 . The flaps  51  may extend directly from the pan side, where the side intersects the bottom. Alternatively, the pan lip  114  may turn down, further than the bottom of the pan  100 , such that there is a gap between the pan side and the down-turned lip, and the flaps  51  are formed out of material from the lip extension  116 . 
       FIG. 18  illustrates blocks  53  (e.g., of wood) that are added to the top of the 2″ beams  40  to pin the pan  100  in place. 
       FIGS. 19 and 20  illustrate additional support that can be added around the support beams  40  to secure and/or support the pan  100 .  FIG. 19  uses ribbing  147 , and  FIG. 12  uses a u-channel type of clip  28  that may be embedded or added separately. If made of a somewhat flexible material that can be folded during storage, such supports may still allow the pan  100  to be stackable. In either case, the added supports do not affect the ability of the drainage to flow to the front of the pan. 
     Flow of drainage is obviously important.  FIG. 21  illustrates a pan  100  with an angled back  115  to make sure that water flows to the drop-front trough portion  120 .  FIG. 22  illustrates a slightly shorter 2″ beam  41  in the front, near the drop-front trough portion  120 , than the 2″ beam  40  in the back, giving the pan  100  a slope. In  FIG. 22 , risers  66  would be placed inside the pan  100  on top of the front beam  41  in order to level any unit  30  mounted on the pan  100 . Even with a substantially flat pan  100 , the bottom surface may be formed so that it has a very slight downward slope to the front trough portion  120 . 
     It should be noted that in  FIGS. 18-22 , many features of the drop front pan  100  have been omitted for simplicity. 
     Many of the described embodiments of the pan  100  are configured for, and show, support beams  40  running side to side under the drain pan  100 . In some instances, a design may be preferred for support beams  40  that run front to back, as shown, for example, in  FIGS. 3-7 .  FIG. 15  is a rear view of a drain pan  100  with an extended, down-turned lip extension  116  running adjacent the back sidewall. The descending lugs or projections of the lip extension  116  form notches or saddles  42  accepting beams spaced apart distances A, B, and C, which may be 16″, 20″, and 24″ respectively. For simplicity,  FIG. 15  does not show the drop-front trough  120  of the pan  100 . 
       FIG. 13  also illustrates a configuration of the pan  100  designed to be mounted over front-to-back support beams. In this configuration, support beam receiving channels also rise above the bottom surface of the upper base portion  110  to form long, front-to-back risers, in the form of raised ribs or ridges  105 , for elevating the unit  30 . All drainage still flows to the drop-front trough portion  120 . 
     In another embodiment, not shown, support beams  40  would run diagonally beneath the pan  100 , and corresponding lugs, notches, saddles, and/or channels would also run, or be disposed, diagonally along the sidewalls  119  and/or underside of the pan  100 . 
     Mini-splits are increasing in popularity, and those that function in heat pump mode may also require drain pans  100 . The mini-splits are typically installed on wall brackets  25 , with a standard drain pan  10  hanging underneath.  FIG. 23  illustrates how installation of the drop-front drain pan  100  would provide a more uniform and attractive look for a mini-split installation. The pan  100  hides the bottom portion of the horizontal supports  24 , and a drain hole  137 , if needed, would go out the bottom/back of the drop front trough portion  120  of the pan  100 . 
       FIG. 24  illustrates an embodiment of a mini-split installation that installs the drop front drain pan  100  over the horizontal supports  24  (not shown), and then installs an additional metal frame  26 , attached to the wall brackets  25 , on or over the surface of the main base section  110  to support the mini-split unit. The drop-front pan  100  protects the frame  26  from standing water. It will be evident that the drop front drain pan  100  may also be used with traditional window units. 
     In the embodiment of the expandable drain pan  100  illustrated in  FIGS. 25-30 , the convertible transition section  150  of the pan  100  is referred to as an expansion section  150 . The drain pan  100  comprises a base portion  110  and sidewalls  119  that include at least one expansion section  150 . The pan  100  may be expanded or compressed and still lie flat. Contractors in the field will appreciate a pan  100  with an expansion portion  150  that can convert the pan  100  to a range of standard or common drain pan sizes. The expandable and/or bendable properties of the gussets  160  at key points or fold lines allow the pan  100  to transform. Valleys or drainage channels  162  may run across the transition section or fold area  150  to aid drainage. Or, the channels of the gussets  160  may be shallower than illustrated. 
     It also is envisioned that the pan  100  may fold in ways and locations other than those illustrated, as previously discussed related to  FIG. 8 . It should be noted that in  FIGS. 25-30 , many features of the expandable drain pan  100  have been omitted for simplicity. 
       FIG. 25 , a top view of a drain pan  100 , illustrates an expansion section  150  located toward the center of the drain pan  100 . Condensate that overflows from an air conditioning unit  30  installed above may flow across the expansion section  150  to reach a drain hole  136  (not shown). Additional profiles (not shown) may be added to the base portion  110  and sidewalls  119  of the drain pan  100  to add rigidity. The drain pan  100  may be unibody and nestably stackable. In one embodiment it is thermoformed of plastic, but the product is not limited to plastic or to the process of thermoforming. Risers or cones  140  may be integrally formed within the drain pan  100 . 
       FIG. 26 , a side view of the drain pan  100  in  FIG. 25 , illustrates an expansion section  150  that has been expanded. In this configuration, the gussets  160  have a triangular appearance, but the gussets  160  are preferably rounded as they round the corner from the side walls  119  to the base  100 , as shown in  FIG. 4 . The gussets  160  do not have to be rounded, but rounding is typically better for manufacturing and durability. 
       FIG. 27 , a side view of the expansion section  150  of  FIG. 26 , better details this configuration. Each gusset  160  forms a semi-conical portion  161  bounded in part by a lower leg  155  and a side leg  156 . These legs  155  and  156  connect (around the side walls  119  and base  110  of the expansion section  150 ) to form joints  153 . When the gussets  160  are compressed, the joints  153  allow the semi-conical portions  161  to nest and the drain pan  100  to reduce in size. When the gussets  160  are expanded, the joints  153  allow the drain pan to increase in size according to the leg  155  and  156  lengths. The legs may be configured such that they “lock” after compression or expansion, such that the drain pan  100  maintains its adjusted size. Alternatively, mechanical fasteners or other means may be employed to secure a pan  100  in its adjusted size. 
     In this configuration, the legs  155  and  156  of the semi-conical portion  161  form a right triangle with a first angle  157  and a second angle  159 . The first angle  157  may be 30 degrees and the second angle  159  may be 60 degrees. Or those measurements may be reversed. The angles  157  and  159  are not limited to those degrees, and the triangle is not limited to a right triangle. Rather, different variations on this configuration will allow for variations in expansion and compression. 
     The lengths of the legs  155  and  156  determine the height of the base  110  of the expansion section  150 . Thus the legs  155  and  156  influence the flow of drainage across the expansion section  150 . Ideally, the lower the drain hole  136  (not shown) on a side wall  119  (not shown), the lower the height of the base  110  of the expansion section  150  should be, so drainage does not pool away from the drain hole  136 . It is expected that a lower leg  155  may be about ½″ long in a shallow configuration of this product, but a lower leg  155  is not limited to ½″ in length. 
       FIG. 28  illustrates an expandable drain pan  100  with two expansion sections  150 , one located toward the center of the drain pan  100  and the other located along a side of the drain pan  100 . In this illustration, the central expansion section  150  is shown in a fully expanded configuration. One or both expansion sections  150  may be compressed or expanded for storage and for installation. Additionally, the sidewalls  119  of the expansion sections may or may not have lips. Both expansion sections  150  contain drainage valleys or channels  162  to reduce pooling and help drainage cross the expansion section  150 . 
       FIG. 29  illustrates an expandable drain pan  100  with an expansion section  150  along a side. In this configuration the expansion section lip  165  runs the length of the expansion section  150  along the sidewall  119  and is connected to the expansion section by tabs  169 . If the drain pan  100  is thermoformed, then a space  167  is created between the expansion section  150  and the expansion section lip  165  by use of a router or water jet, leaving the tabs  169 . In practice, an installer would cut the expansion section lip  165  and and/or tabs  169  before compressing or expanding part or all of the expansion section  150 . The installer may use standard sheet metal screws through the cut parts of the expansion section lip  165  to secure the compressed or expanded pan  100  to itself or to a supporting structure in order to help the drain pan  100  maintain its adjusted size. The drawing shows three tabs  169  on each side, but the drain pan  100  is not limited to three tabs  169  per side. The drain pan  100  may utilize no tabs  169  or may omit expansion section lip  165 . Further, the expansion section lip  165  itself may be flexible and expandable. 
     An expansion section  150  is not limited to a specific expansion length. However, for example, if the drain pan  100  in  FIG. 29  is 32″×63″ in its original position, the pan  100  may compress to 30″×63″ or 27″×63″ or expand to 36″×63″. An expansion section  150  with approximately 6″ extension length would cover multiple adjusted sizes and allow anti-vibration pads or risers to contact both the base  110  and the equipment  30  without interference from the expansion section  150  itself. Therefore, the installer receives greater functionality from one drain pan. 
       FIG. 30  illustrates a drain pan  100  with a stepped expansion section  150  along a side. The base  110  of the expansion section  150  may be stepped such that the base  110  at a side of the pan  100  is higher than the base  110  toward the center of the pan  100 , allowing drainage to cascade toward the center of the pan  100  and away from a side  119  of the pan  100 . The gussets  160  may be secured to maintain the pan  100  in this position. As in  FIG. 27 , the gussets or folds  160  comprise angles that allow the folds to compress, expand, and “lock” like the corrugations of a flexible drinking straw or downspout. Unlike those products, which flex somewhat like a ball joint, the drain pan  100  is not circular and has an open top, reducing flexibility. Thus, the expansion section  150  mainly expands and collapses in a unidirectional manner, such that a sidewall  119  whether expanded or collapsed resides in the same relative orientation. Additionally, thermoforming a product of this thickness with such flexibility is a technical challenge. The top of the transition portion  150  may have no upper lip  114  in order to increase flexibility. The fold lines of the configuration section  150  may be configured other than as shown, and other methods may be used to make the drain pan  100  maintain its adjusted size. 
     Secondary drain pans  100  are required by code to be larger on each side than the equipment  30  resting above, and risers or other supports placed in the pan  100  under the equipment  30  are typically located several inches inside the perimeter of the equipment. For this reason, the stepped expansion section  150  along a side of a pan  100  will not interfere with the air conditioning unit  30 , and drainage is less likely to drip into the expansion section  150  along the side than into the central area of the base  110 . 
     A method for installing a pre-manufactured expandable secondary condensate drain pan  100  under an air conditioning unit  30  comprises adjusting the size of the drain pan  100 , configuring the drain pan  100  to remain as adjusted, placing the drain pan  100  on a support, installing a set of anti-vibration pads  61  or risers  59 , and setting an air conditioning unit  30  on the drain pan  100 . The method may further comprise cutting one or more expansion section lips  165 . Some steps in this method may be reordered or omitted. 
     Although the foregoing specific details describe various embodiments of the invention, persons reasonably skilled in the art will recognize that various changes may be made in the details of the apparatus of this invention without departing from the spirit and scope of the invention as defined in the appended claims. 
     The present invention includes several independently meritorious inventive aspects and advantages. Unless compelled by the claim language itself, the claims should not be construed to be limited to any particular set of drawings, as it is contemplated that each of the drawings may incorporate features shown in others of the drawings.