Abstract:
A packaged air conditioner or heat pump unit is provided with an elongated removable drain pan having an inner longitudinal portion that underlies and receives condensate falling from the portion of the unit&#39;s indoor coil positioned within the conditioned air flow through the unit. An outer longitudinal portion of the drain pan underlies tubing portion return bends of the coil positioned outside of the conditioned air flow and separated from the inner longitudinal pan portion by a vertical dividing wall having a small condensate transfer hole therein. During cooling operation of the unit, the unit blower creates a negative pressure inwardly adjacent the hole which draws return bend condensation from the outer longitudinal pan portion into the inner longitudinal pan portion for drainage outwardly therefrom, with the condensate received from the balance of the coil, via a drain line connected to the pan.

Description:
BACKGROUND OF THE INVENTION 
   The present invention generally relates to air conditioning apparatus and, in a representatively illustrated embodiment thereof, more particularly relates to condensate drain pan structures used in conjunction with air conditioning cooling coils. 
   A coil used in air conditioning apparatus such as furnaces, air handling units, heat pumps and packaged air conditioners extracts moisture from the air which is being flowed externally across the coil (by a blower portion of the apparatus and cooled by the coil for delivery to a conditioned space served by the apparatus. This moisture extraction creates condensation (water) on the exterior of the coil which drips from the coil into an associated drain pan structure within the outer housing of the air conditioning apparatus. Coil condensation dripping into the pan flows away therefrom by gravity via a condensate drain line suitably connected to the pan. 
   Packaged self-contained heat pumps and air conditioners are typically positioned outside of a building (such as on the roof or on the ground adjacent the building) which they serve. In several conventional designs of such a packaged unit its condensate drain pan underlies the portion of the cooling coil which is interposed in the return air/supply air conditioned air stream and catches and drains away condensate falling from this coil portion. However, in these conventional air conditioning apparatus designs, coil tubing return bends which are not disposed in the cool conditioned air stream project outwardly from an end of the coil and beyond the condensate-receiving periphery of the underlying drain pan. 
   Because packaged units of this type are normally positioned outdoors, it was not thought necessary to use a drain pan structure to catch and drain away this relatively minor condensate drippage from these exposed coil tubing return bends. However, in time, this minor condensate drippage tended to leak out of the housing of the packaged unit and, when observed by the owner of the unit, triggered “nuisance” service calls to fix what, in reality, was neither a defect in or a problem with the unit. 
   In view of this it would be desirable to provide a modified drain pan which additionally receives and drains away this coil tubing return bend condensate without having to modify the unit in which the drain pan is installed. It is to this goal that the present invention is directed. 
   SUMMARY OF THE INVENTION 
   In carrying out principles of the present invention, in accordance with a preferred embodiment thereof, a specially designed condensate drain pan is incorporated in an air conditioning apparatus, representatively a self-contained heat pump package unit, and is useable to catch, and drain away, condensate falling from the unit&#39;s indoor coil which functions as a cooling coil during use of the unit in a cooling mode. Such condensate is formed on the exterior of the coil as a blower portion of the unit draws air through the interior of its housing and across the cooling coil which is disposed therein. 
   The cooling coil has a main body portion disposed in the blower-created conditioned air stream, and a series of coil tubing return bends projecting outwardly from the main coil body portion and disposed outside of the conditioned air stream. The condensate drain pan is removably supported beneath the cooling coil and preferably has an elongated, generally trough-shaped body having a bottom wall, first and second opposite upstanding end walls, and an upstanding intermediate wall dividing the body into a first longitudinal portion extending between the first end wall and the intermediate wall and underlying the main coil body portion, and a second longitudinal portion extending between the intermediate wall and the second end wall and underlying the coil tubing return bends. 
   A condensate transfer opening is formed in the intermediate wall and intercommunicates the interiors of the first and second longitudinal portions of the drain body. The drain pan further includes a drain conduit structure connected to the first longitudinal portion of the body and having an inlet communicated with its interior. 
   During operation of the unit in a cooling mode, condensate from the main coil body falls into the first longitudinal drain pan portion and is drained away therefrom via the drain conduit structure. At the same time, condensate from the coil tubing return bends falls into the second longitudinal drain pan portion. Operation of the blower creates a negative pressure within the first longitudinal drain pan portion which draws the condensate from the second longitudinal drain pan portion inwardly through the condensate transfer opening into the interior of the first longitudinal drain pan portion. This transferred condensate is drained away from the interior of the first longitudinal drain pan portion via the drain conduit structure. 
   Illustratively, the drain pan is formed from a glass-filled polypropylene material, but could alternatively be formed from a variety of other suitable materials if desired. In the illustrated embodiment of the drain pan its first longitudinal portion has an upwardly concave bottom wall and an upstanding central rib with a bottom edge cutout area at the intermediate wall, the inlet of the drain conduit structure being disposed at this cutout area. 
   In the illustrated embodiment of the condensate drain pan, the drain conduit structure longitudinally extends transversely outwardly from the intermediate wall, with a longitudinal portion of the drain conduit structure being disposed within the second longitudinal drain pan portion. The second longitudinal portion of the body includes first and second laterally opposite bottom wall portions having upwardly concave configurations and projecting outwardly from circumferentially spaced apart outer side surface portions of the drain conduit structure. Preferably, the second bottom wall portion is disposed higher than the first bottom wall portion. This configuration of the second longitudinal drain pan portion facilitates the flow of condensate through the interior of the second longitudinal drain pan portion to the condensate transfer opening which is preferably disposed closely adjacent the juncture between the first bottom wall portion and the condensate drain conduit structure. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
       FIG. 1  is a perspective view of a cooling coil having operatively supported thereon a specially designed condensate drain pan embodying principles of the present invention, the drain pan being in its retracted operating orientation; 
       FIG. 2  is a front side perspective view of a representative self-contained heat pump package unit in which the drain pan is removably incorporated, the drain pan being shown in an outwardly extended inspection/maintenance position; 
       FIG. 3  is a partially exploded front side perspective view of the heat pump unit of  FIG. 2 ; 
       FIG. 4  is a partially exploded rear side perspective view of the heat pump unit with the drain pan in its retracted operating orientation; 
       FIG. 5  is an enlarged scale perspective view of the drain pan removed from the cooling coil; 
       FIG. 6  is an enlarged scale schematic partial cross-sectional view through the drain pan taken generally along line  6 - 6  of  FIG. 5 ; 
       FIG. 7  is an enlarged top plan view of an outer end portion of the drain pan as shown in  FIG. 5 ; 
       FIG. 8  is a cross-sectional view through the drain pan taken generally along line  8 - 8  of  FIG. 7 ; and 
       FIG. 9  is an outer end elevational view of the drain pan taken generally along line  9 - 9  of  FIG. 7 . 
   

   DETAILED DESCRIPTION 
   Referring initially to  FIGS. 1 and 2 , the present invention provides air conditioning apparatus, representatively in the form of a self-contained heat pump package unit  10 , which incorporates therein a specially designed removable condensate drain pan  12  that embodies principles of the present invention. Illustratively, the self-contained heat pump package unit  10 , in which the novel drain pan  12  is installed, is of a prior art configuration, but could alternatively be a self-contained packaged air conditioner of the same prior art configuration, or another type of air conditioning apparatus or unit requiring a condensate drain pan. 
   With reference now to  FIGS. 5-9 , the drain pan  12  (see  FIG. 5 ) is representatively of a unitary, non-metallic construction, preferably being formed from a glass-filled polypropylene material, and has a horizontally elongated configuration with an inner longitudinal portion  12   a  and an outer longitudinal portion  12   b.  As described in greater detail below, the inner longitudinal drain pan portion  12   a  is similar to the prior art drain pan previously incorporated in the representatively illustrated package heat pump unit  10 , while the outer longitudinal drain pan portion  12   b  represents a novel addition to and improvement of the previous drain pan, and is a key aspect of the present invention. 
   The conventional inner longitudinal drain pan portion  12   a  includes inner and outer end walls  14 , 16  and an elongated base wall  18  extending between walls  14 , 16  and having, along its length, an arcuate, upwardly concave configuration. As illustrated, the wall  16  transversely projects outwardly beyond the base wall  18 . From its opposite outer sides, base wall  18  laterally slopes downwardly and inwardly. Longitudinally extending along a central top side portion of the base wall  18 , between the opposite end walls  14  and  16 , is an elongated upstanding rib  20  having a bottom edge cutout area  22  (see  FIG. 6 ) extending inwardly from the outer end wall  16 . A tubular drain outlet fitting  24  extends outwardly from the outer end wall  16  and has an inlet  24   a  that communicates with a bottom interior area of the inner longitudinal drain pan portion  12   a  at the rib cutout area  22  as best illustrated in  FIGS. 6 and 7 . A suitable sealing gasket  26  is preferably secured to the inner side of the outwardly projecting portion of the outer end wall  16 . 
   The new outer longitudinal drain pan portion  12   b  extends longitudinally outwardly from the wall  16 , with the drain outlet fitting  24  extending through a bottom interior side portion of the drain pan portion  12   b  as best illustrated in  FIGS. 5 and 8 . Drain outlet fitting  24  has been somewhat lengthened to accommodate the novel addition to the overall drain pan  12  of the specially designed outer longitudinal drain pan portion  12   b.    
   As best illustrated in  FIGS. 5 ,  8  and  9 , the outwardly extending drain pan portion  12   b  is generally trough-shaped and has an outer end wall  28  (making the end wall  16  of the drain pan portion  12   a  a longitudinally intermediate wall in the lengthened drain pan  12  of the present invention), and first and second upwardly concave side walls  30  and  32  sloping laterally inwardly and downwardly to circumferentially spaced apart outer side surface portions of the drain outlet fitting  24 . According to another aspect of the present invention, for purposes later described herein, a small circular condensate transfer hole  34  is formed through the wall  16  upwardly adjacent the juncture between the side wall  30  and the drain outlet fitting  24 , and communicates the interiors of the inner and outer longitudinal portions  12   a , 12   b  of the condensate drain pan  12 . Both of the side walls  30 , 32  of the outer longitudinal drain pan portion  12   b  slope laterally inwardly and downwardly toward the condensate transfer hole  34  which is disposed upwardly adjacent a bottom interior side portion of the drain pan portion  12   b.  Side wall  32  is disposed somewhat higher than side wall  30 . 
   The condensate drain pan  12 , as best illustrated in  FIG. 1 , is removably and operatively supported beneath the indoor coil  36  of the illustrated heat pump unit  10  which, during the cooling cycle of the unit functions as a cooling coil that exteriorly generates condensate which falls therefrom. However, the condensate drain pan  12  may alternatively be utilized in conjunction with a variety of other types of condensate-generating cooling coils without departing from principles of the present invention. 
   With continuing reference to  FIG. 1 , coil  36  is of a fin and tube construction and has a main body portion  37  with a horizontally elongated rectangular shape. Coil body  37  has a horizontally inner end to which a coil plate  38  is mounted, and a horizontally outer end to which a substantially wider coil plate  40  is mounted. Tubing return bends  42  project horizontally outwardly from the plate  38 , and tubing return bends  44  project horizontally outwardly from the plate  40 . For purposes later described herein, a horizontally elongated opening  46  is formed through a bottom end portion of the coil plate  40 . 
   The drain pan  12  is operatively installed beneath the coil  36  by longitudinally sliding the drain pan  12  (from its  FIG. 1  removed orientation) inwardly through the outer coil plate opening  46  until the gasketed drain pan wall  16  is brought into abutment with the coil plate  40 . Screws  48  (see  FIGS. 1 and 2 ) are then threaded into aligned openings in the drain pan wall  16  and coil plate  40  to removably retain the inserted drain pan  12  beneath the coil  36 . The inserted drain pan base wall  18  rests on an underlying, complementarily shaped support structure  50  (see  FIG. 1 ) which, in turn is disposed within the interior of the packaged heat pump unit  10  and suitably secured to its bottom wall  52  (see  FIGS. 2-4 ). The support structure  50  is configured in a manner such that the inserted drain pan  12  longitudinally slopes downwardly from its inner end wall  14  towards the  16 . 
   As illustrated in  FIGS. 2-4 , the packaged heat pump  10  has a hollow rectangular housing  54  having, in addition to its bottom wall  52 , a removable top wall  56 , front and rear side walls  58  and  60 , and opposite end walls  62 , 64 . A removable access panel  66  on the front wall  58  (shown only in  FIG. 4 ) covers a recessed area  68  disposed within front side of the heat pump interior and through which the drain pan  12  may be installed and removed. 
   The coil  36  is suitably supported within the interior of the heat pump housing  54  with the coil plate  40  forming the inner boundary of the recessed area  68 , the coil tubing return bends  44  projecting into the recessed area  68  and overlying the open top side of the outer longitudinal portion  12   b  of the removably installed drain pan  12 , and the main body  37  of the coil  36  overlying the open top side of the inner longitudinal portion  12   a  of the installed drain pan  12 . A conditioned air flow plenum  70  extends inwardly from the housing end wall  64  and is divided by the coil  36  into a return portion  70   a  and a supply portion  70   b  (see  FIGS. 3 and 4 ). Return and supply air openings  72 , 74  (see  FIG. 4 ) are formed in the rear housing wall  60  and respectively communicate with the return and supply portions  70   a , 70   b  of the plenum  70 . An air supply blower  76  is operatively disposed in the plenum  70   b  downstream from the coil  36 . 
   During cooling operation of the heat pump.  10 , the blower  76  draws return air  78  (see  FIG. 4 ) from the conditioned building space served by the heat pump  10  into the plenum portion  70   a  via opening  72 , across coil  36  to cool the return air  78 , and then forces the now cooled air outwardly through the supply opening  74  in the form of cooled supply air  80  for delivery to the conditioned space. Suitable air ducts (not shown) may be appropriately connected to the return and supply openings  72 , 74  in a conventional manner to appropriately route the air flows  78 , 80  external to the heat pump  10 . As can be seen, the blower  76 , relative to the coil  36 , operates in a “draw through” mode. This creates a negative pressure region adjacent the coil  36  and the inner side of the drain pan wall  16  that outwardly overlies the coil plate opening  46  (see  FIG. 1 ). 
   Portion  12   b  of the installed drain pan  12 , and the coil return bends  44 , are disposed outside the blower-created air flow stream within the recessed area  68  of the housing  54 . With reference now to  FIG. 7 , condensate  82  falling from the body  37  of the coil  36  drops into the open top side of the underlying inner longitudinal portion  12   a  of the drain pan  12 , laterally drains toward a laterally central portion of the upwardly concave drain pan base wall  18 , and longitudinally drains along the top side of the base wall  18  toward the drain pan  16  where, via the rib cutout area  22 , the condensate  82  enters and flows outwardly through the drain outlet fitting  24 . The upstanding central rib  20  acts as a protective barrier to prevent air flowing horizontally across the coil  36  from forcing condensate  82  out of the inner longitudinal drain pan portion  12   a.    
   Also during cooling operation of the heat pump  10  (or another type of condensate-generating air conditioning apparatus in which the drain pan  12  is installed as the case may be), and according to a key aspect of the present invention, condensate  84  from the coil tubing return bends  44  falls into the open top side of the underlying outer longitudinal portion  12   b  of the drain pan. The blower-created negative pressure at the inner side of the drain pan wall  16  draws the condensate  84  inwardly through the condensate transfer hole  34  in the wall  16  into an outer end portion of the inner longitudinal portion  12   a  of the drain pan  12 . Condensate  84  entering the drain pan portion  12   a  via the wall hole  34  then, by gravity, reverses direction and flows outwardly through the drain outlet fitting  24  with the flow of condensate  82 . 
   With reference now to  FIG. 8 , the transfer to the wall hole  34  of the condensate  84  received by the outer longitudinal portion  12   b  of the drain pan  12  is facilitated by a novel configuration of its bottom wall structure. Specifically, both of the bottom side wall portions  30 , 32  of the drain pan extension portion  12   b  have an upwardly concave shape, with each of the side wall portions  30 , 32  extending outwardly from the drain outlet fitting  24 , and the condensate transfer hole  34  being adjacent the juncture of the wall portion  30  and the drain outlet fitting  24 . As previously noted, the side wall portion  32  is positioned higher than the side wall portion  30  and has a top side generally flush with the top side of the drain outlet fitting  24 . Accordingly, condensate  84  falling onto the side wall  32  easily drains by gravity laterally across the drain outlet fitting  24  and into the lowest area of the wall  30  disposed at the condensate transfer hole  34 . 
   As previously mentioned herein, the specially designed drain pan  12  of the present invention may be used to advantage in conjunction with air conditioning apparatus of types other than the illustrated heat pump  10  without departing from principles of the present invention. Additionally, while the negative pressure region within the unit housing  54 , created by operation of the blower  76  and drawing the return bend condensate  84  into the inner longitudinal drain pan portion  12   a,  is representatively created by placing the blower  76  downstream from the coil  36 , other apparatus and techniques for creating this negative pressure region within the housing  54  during blower operation (such as, for example, using a blow-through coil arrangement and a suitable venturi structure adjacent the condensate transfer hole  34 ) may be alternatively utilized without departing from principles of the present invention. 
   The foregoing detailed description is to be clearly understood as being given by way of illustration and example only, the spirit and scope of the present invention being limited solely by the appended claims.