Condensate drain pan for air conditioning system

A drain pan for capturing condensate from a cooling coil in an air conditioning system is configured to facilitate condensate drainage from the pan and to inhibit accumulation of condensate therein. The pan includes troughs for collecting condensate and for channeling the condensate to the front part of the pan where the drain openings are located. A back trough has a central hump to enhance the flow of condensate from the back trough in both directions into opposed side troughs. The side troughs are sloped from back to front to conduct the condensate into a front trough to facilitate drainage from the pan. The lowermost portion of the front trough region is defined by a relatively narrow, non-flat area to reduce the amount of condensate residue in the pan.

TECHNICAL FIELD

This invention relates generally to air conditioning systems and in particular to a drain pan adapted to capture condensate from a cooling coil in an air conditioning system.

BACKGROUND ART

Air conditioning systems typically include a blower for circulating air to and from an indoor space to be heated or cooled and apparatus for cooling or heating the circulated air, depending on the mode of operation of the system (i.e., either heating or cooling mode). A device (e.g., a compressor) is also provided for circulating a heat transfer fluid (e.g., a vapor compression refrigerant) between indoor and outdoor heat exchanger coils, whereby the air supplied to the space is cooled or heated. When the system is a conventional air conditioning system (i.e., not a heat pump system), the indoor coil functions as a cooling coil (i.e., as an evaporator when a vapor compression refrigerant is used as a heat transfer fluid) to transfer heat from the air flowing across the outside of the coil to the heat transfer fluid flowing inside the coil, and the outdoor coil functions as a heating coil (i.e., as a condenser when a vapor compression refrigerant is used as a heat transfer fluid) to transfer heat from the heat transfer fluid flowing inside the outdoor coil to outdoor air flowing across the outside of the coil. When the air conditioning system is configured as a heat pump, the indoor coil functions as a cooling coil and the outdoor coil functions as a heating coil in the cooling mode, as in a conventional air conditioning system. However, in the heating mode, the functions are reversed (i.e., the indoor coil functions as a heating coil and the outdoor coil functions as a cooling coil).

When a heat exchanger coil is operated as a cooling coil (e.g., an evaporator), air flowing across the coil is dehumidified as well as cooled, causing condensation to form on the coil. This condensation must be disposed of to prevent freezing of the coil and damage to the surrounding building structure. Typically, a drain pan is located beneath the coil to receive condensate runoff. The pan includes an opening in a bottom part of the pan to conduct the condensate accumulated in the pan to an external drainage conduit. Drain pans of various types are known in the art, as exemplified by the following U.S. Pat. Nos. 4,474,232; 5,071,027; 5,511,386; 5,715,697; 5,966,959; and 6,360,911 B1.

It is advantageous to reduce water retention in the pan to the extent feasible, not only to reduce the likelihood of condensate spillage from the pan onto the adjacent building structure, but also to inhibit the formation of mold, rust and other undesirable byproducts of stagnant water in the pan. Further, air flowing through the heat exchanger coil may pick up moisture from excessive water accumulation in the pan, which may result in unwanted humidity in the air supplied to an indoor space.

SUMMARY OF THE INVENTION

In accordance with the present invention, a drain pan for an air conditioning system is provided. The pan is comprised of an inner front wall, an inner back wall and opposed inner side walls defining an inner perimeter of the pan, and an outer front wall, an outer back wall and opposed outer side walls defining an outer perimeter of the pan. The outer front wall has at least one drain opening to allow condensate to drain from the pan and a trough intermediate the inner perimeter and the outer perimeter. The trough is adapted to receive condensate runoff from an air conditioning coil and to conduct the condensate to the drain opening.

In accordance with one aspect of the invention, a portion of the trough between the inner back wall and the outer back wall includes a central hump to facilitate drainage of condensate toward both of the outer side walls. In accordance with another aspect of the invention, the pan is sloped from back to front to conduct condensate to the front part of the pan where the drain opening is located. In accordance with yet another aspect of the invention, a lowermost portion of the trough is defined by a non-flat surface to reduce condensate accumulation in the pan and to enhance condensate flow in the trough.

In accordance with one embodiment of the invention, the trough includes a front trough between the inner front wall and the outer front wall, a back trough between the inner back wall and the outer back wall, a first side trough between a first inner side wall and a first outer side wall and a second side trough between a second inner side wall and a second outer side wall. In accordance with another embodiment of the invention, the drain pan further includes first and second drain openings in the outer front wall. The first opening is generally aligned with the first side trough and said second drain opening is generally aligned with the second side trough.

In accordance with a preferred embodiment of the invention, the front trough is defined by a sloped surface extending downwardly and inwardly from the outer front wall and a curved surface extending downwardly and outwardly from the inner front wall. The intersection of these two surfaces defines a non-flat lowermost portion of the front trough. The back trough is defined by a first curved surface extending downwardly and outwardly from the inner back wall and a second curved surface extending downwardly and inwardly from the outer back wall. The first and second curved surfaces have different radii of curvature, such that their intersection also defines a non-flat lowermost portion of the back trough. Each side trough is defined by first and second sloped surfaces in downwardly converging relationship, with a curved surface intermediate the first and second sloped surfaces. The curved surface defines a lowermost portion of each side trough. Each side trough defines a channel for condensate flow. Each channel is at its deepest and narrowest proximate to the front trough and at its widest and shallowest proximate to the back trough.

BEST MODE FOR CARRYING OUT THE INVENTION

The best mode for carrying out the invention will now be described with reference to the accompanying drawings. Like parts are marked in the specification and drawings with the same respective reference numbers. In some instances, proportions may have been exaggerated in order to more clearly depict certain features of the invention.

Referring toFIGS. 1–10, a condensate drain pan10according to the present invention is adapted to be positioned underneath a heat exchanger coil12in a typical air conditioning system to capture condensate runoff from coil12when coil12is operated as a cooling coil to cool air flowing through coil12. For example, coil12may be used as an “evaporator” coil, to cool air flowing through coil12by evaporating a vapor compression refrigerant flowing inside tubes13of coil12. Coil12is depicted inFIG. 1as a conventional “A-Coil”, comprised of a pair of slabs12a,12bcoupled together at their respective upper ends and extending downwardly in diverging relationship. Each slab12a,12bis depicted as having two parallel rows of heat transfer fluid carrying tubes13. However, one skilled in the art will recognize that coil12can be configured with more or fewer than two rows of tubes13.

As can be best seen inFIGS. 2–5, drain pan10has a generally rectangular shape and is made of plastic, preferably by an injection molding process. Pan10has an outer front wall14, an outer back wall16and opposed outer side walls18,20. Walls14,16,18,20define a generally rectangular outer perimeter of pan10. Pan10further includes an inner front wall22, an inner back wall24and opposed inner side walls26,28. Walls22,24,26,28define a generally rectangular inner perimeter of pan10, which surrounds a central opening29. Opening29allows the air to be cooled to flow upwardly through pan10into coil12between slabs12a,12band then outwardly through slabs12a,12b, where heat is transferred from the air to the heat transfer fluid in tubes13to cool the air. Located on inner front wall22and inner back wall24are mounting clips30, which are adapted for mounting heat exchanger coil12in a fixed position with respect to drain pan10in a conventional manner. As can be best seen inFIG. 2, respective intermediate portions26a,28aof inner side walls26,28are reduced in height compared to front and back walls22,24to enhance the air flow through coil12. Inner side wall26further includes sloped portions26b,26con opposed sides of intermediate portion26a. Sloped portion26bis proximate to inner front wall22and sloped portion26cis proximate to inner back wall24. Inner side wall28further includes sloped portions28b,28con opposed sides of intermediate portion28a. Sloped portion28bis proximate to inner front wall22and sloped portion28cis proximate to inner back wall24.

The bottom part of drain pan10between the inner perimeter and outer perimeter thereof is a condensate collection region comprised of a front trough32, a back trough34and opposed side troughs36,38. Front trough32is located between outer front wall14and inner front wall22. Back trough34is located between outer back wall16and inner back wall24. Side trough36is located between outer side wall18and inner side wall26and side trough38is located between outer side wall20and inner side wall28.

Outer front wall14includes respective primary and secondary drain openings40,42adjacent side trough36and respective primary and secondary drain openings44,46adjacent side trough38. Both sets of drain openings are adapted for attachment to an external conduit (not shown) for draining condensate from pan10. By having two sets of drain openings, either side of pan10may be used to drain condensate therefrom. The set of drain openings not in use is capped to prevent condensate drainage therefrom. As can be best seen inFIGS. 2,3,5and10, primary drain opening40is generally aligned with side trough36and is located proximate to a relatively small depression47, which is located at the confluence of side trough36and front trough32, to facilitate drainage of condensate from pan10. Similarly, primary drain opening44is located proximate to a relatively small depression48, which is located at the confluence of side trough38and front trough32. Depressions47,48define the lowermost portions of pan10. In the event that the primary drainage conduit in use becomes blocked, condensate will back up into front trough32through the corresponding primary drain opening40or44until it reaches the level of the corresponding secondary drain opening42or46, whereupon condensate will flow out of drain pan10through the corresponding secondary drain42or46.

The respective bottom portions of side troughs36,38are sloped from back trough34to front trough32at an angle of about 2° relative to a horizontal axis, to enhance the flow of condensate to the front part of pan10, as shown by arrows50inFIGS. 5 and 6. Further, as can be best seen inFIG. 7, back trough34has a central raised portion or hump51and is sloped from hump51toward both side troughs36,38at an angle of about 4° relative to a horizontal axis, to cause condensate in back trough34to flow away from hump51in the direction of both side troughs36,38(as represented by arrows52,54, respectively). Therefore, pan10is configured to direct the flow of condensate from back trough34into side troughs36,38and from side troughs36,38into front trough32.

As can be best seen inFIG. 6, front trough32is defined by a sloped surface56extending downwardly and inwardly from outer front wall14at a substantially constant angle of about 20° relative to a horizontal axis and a curved surface58extending downwardly and outwardly from inner front wall22at a predetermined radius of curvature (e.g., about 1.1343 inches). The intersection of surfaces56,58defines a non-flat bottom32aof front trough32, which enhances condensate flow in front trough32and reduces condensate accumulation therein. Bottom32ais slightly elevated with respect to depressions47,48, so that substantially all of the condensate in pan10finds its way into one of the depressions47,48. Condensate will flow from the depression47,48that is in communication with the primary drain40,44in use. However, condensate in the opposite depression47,48will remain in pan10, but the amount that remains is negligible because volume of depressions47,48is relatively small. Further, by configuring bottom32aso that it is relatively narrow channel defined by a non-flat surface, the flow of condensate in front trough32is enhanced, which facilitates drainage of the condensate from pan10.

As can be best seen inFIGS. 6 and 9, back trough34is defined by curved surfaces60,62having different radii of curvature. For example, surface60preferably has a radius of curvature of about 0.4095 inch, while surface62preferably has a radius of curvature of about 0.4960 inch, so that the curvature of surface60is slightly more pronounced than the curvature of surface62. Curved surface60extends downwardly and outwardly from inner back wall24and curved surface62extends downwardly and inwardly from outer back wall16. The intersection of surfaces60,62defines a non-flat bottom34aof back trough34, which along with hump51enhances condensate flow in back trough34and reduces condensate accumulation therein.

As can be best seen inFIGS. 8 and 10, side trough36is defined by sloped surfaces64,66extending downwardly and inwardly from outer side wall18and a sloped surface68extending downwardly and outwardly from inner side wall26. A curved surface70is intermediate sloped surfaces66,68and defines a non-flat bottom portion of side trough36. Sloped surfaces66,68are sloped at angles of about 20° and 70° degrees, respectively, relative to a horizontal axis, along the entire length of side trough36. However, the slope angle of surface64changes along the length of side trough36. For example, the slope angle of surface64is greatest proximate to front trough32(e.g., about 20°), as shown inFIG. 10and least proximate to rear trough34(e.g., about 12°). The slope angle of surface64is about 16° at the approximate midpoint of side trough36between front and back troughs32,34, as shown inFIG. 8.

The radius of curvature of curved surface70also varies along the length of side trough36. The curvature is more pronounced in proximate to front trough32(e.g., radius of curvature of about 0.3344 inch), as shown inFIG. 9and least pronounced proximate to back trough34(e.g., radius of curvature of about 0.4752 inch). At the approximate midpoint of side trough36, the radius of curvature of surface70is intermediate the respective radii of curvature of surface70proximate to front and back troughs32,34(e.g., about 0.4048 inch). As previously described, bottom portion36aslopes downwardly from back trough34to front trough32at an angle of about 2°, so that side trough36is at its deepest proximate to front trough32and is at its shallowest proximate to back trough34. Although described in detail herein, one skilled in the art will recognize that side trough38has the same configuration as side trough36, as described hereinabove.

In accordance with the present invention, a drain pan is provided for use in an air conditioning system. The pan is adapted to enhance the flow of condensate captured by the pan toward the drain opening, to facilitate drainage of condensate from the pan and inhibit accumulation of condensate in the pan.

The best mode for carrying out the invention has now been described in detail. Since changes in and additions to the above-described best mode can be made without departing from the nature, spirit and scope of the invention, the invention is not to be limited to the above-described best mode, but only by the appended claims and their equivalents.