Abstract:
A blockage detector initially sounds an alarm while permitting the air cooling system to continue to operate when a first level of liquid is detected within the drain pan of an air cooling system. The blockage detector will turn off the air cooling system when a second level of liquid, which is greater than the first level of liquid, is detected in the drain pan of the air cooling system. This enables the resident(s) of the building (which could be a single family-dwelling or a multiple-family dwelling, such as an apartment building) to contact a technician to correct the blockage condition before the air-cooling system is turned off. If the alarm is not detected, or if the blockage is not eliminated quickly enough, the detector will turn off the air cooling system before water overflows from the drain pan and causes water damage to the building.

Description:
BACKGROUND OF THE INVENTION  
         [0001]    1. Field of Invention  
           [0002]    The present invention relates to blockage detectors, and in particular to blockage detectors that can be incorporated into air cooling systems to detect blockage in portions of the condensate drainage tubing.  
           [0003]    2. Description of Related Art  
           [0004]    Numerous devices are available for detecting a blockage in the condensate drainage tubing of an air-cooling system, for example, which is included as part of the HVAC system of buildings. As is known, the air-cooling systems include a heat exchange coil that forms condensate, which is caught by a drain pan of the system. The liquid is evacuated from the drain pan through tubing, which leads to the outside of the building or to some drainage area. The drain tubing often includes a U-shaped trap to form a water seal in the drainage path.  
           [0005]    The drain tubing is small in diameter, and can become clogged by dirt and mold that accumulates within the drainage tubing.  
           [0006]    Systems are available for detecting clogging of the drainage tubing, for example, by detecting that the level of fluid within the drain pan of the air-cooling system is above some predetermined level. One such system is shown in U.S. Pat. No. 5,522,229 to Stuchlik, III et al. The disclosure of U.S. Pat. No. 5,522,229 is incorporated herein by reference in its entirety. When the predetermined level of liquid, indicative of a blockage, is detected within the drain pan, the system of U.S. Pat. No. 5,522,229 sounds an alarm and/or turns off the air cooling system.  
           [0007]    Like the above-mentioned patent, other known blockage detectors also sound an alarm and/or turn off the air cooling system when the liquid reaches a predetermined level. While the systems that turn off the air cooling system are successful in preventing condensate from overflowing out of the drain pan, which can cause water damage to the building, it can be inconvenient (and uncomfortable) to the building resident(s) for the air-cooling system to be turned off, particularly if a technician is not available to clear the blockage in the immediate future. While systems that only sound an alarm do not have this problem, such systems can lead to water damage if the alarm is not detected (for example, if the resident(s) of the building is/are out of town when the alarm is sounded) or if the blockage is not eliminated quickly enough.  
         SUMMARY OF THE INVENTION  
         [0008]    The invention seeks to address the above-identified problems in known blockage detection systems.  
           [0009]    According to one aspect of the invention, a blockage detector initially sounds an alarm while permitting the air cooling system to continue to operate when a first level of liquid is detected within the drain pan of an air cooling system. The blockage detector will turn off the air cooling system when a second level of liquid, which is greater than the first level of liquid, is detected in the drain pan of the air cooling system. This enables the resident(s) of the building (which could be a single family-dwelling or a multiple-family dwelling, such as an apartment building) to contact a technician to correct the blockage condition before the air-cooling system is turned off by the detector. On the other hand, if the alarm is not detected, or if the blockage is not eliminated quickly enough, the detector will turn off the air cooling system before water overflows from the drain pan and causes water damage to the building.  
           [0010]    As part of the alarm function, the blockage detector can actuate a dialing system that contacts the technician, thereby placing a service call to have the blockage corrected. 
       
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0011]    The invention will be described with reference to the following drawings, in which like reference numerals refer to like elements, and wherein:  
         [0012]    [0012]FIG. 1 is a diagrammatic view of an air cooling system incorporating the blockage detector of one preferred embodiment of this invention;  
         [0013]    [0013]FIG. 2 is a perspective view of the air cooling system drain pan, showing the blockage detector and a drain pipe attached to the drain pan;  
         [0014]    [0014]FIG. 3 is a schematic diagram of the electrical connections made by the blockage detector, its remote panel, a dialing system and the building&#39;s air cooling system and power transformer;  
         [0015]    [0015]FIG. 4 is a perspective view of the blockage detector sensor housing having a square cross section;  
         [0016]    [0016]FIG. 5 shows the rear surface of the FIG. 4 blockage detector; and  
         [0017]    [0017]FIG. 6 is an exploded, perspective view of a blockage detector having a circular cross-section sensor housing and the coupling structure by which the sensor housing is attached to the air cooling system drain pan.  
     
    
     DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS  
       [0018]    [0018]FIG. 1 is a diagrammatic view of an air cooling system including the blockage detector and a remote panel of one embodiment of the invention. The air cooling system includes an air handler  10 , which contains the heat exchange coils  22  of an air cooling device  20 . The heat exchange coils  22  carry a cold material for cooling warm air conveyed into the air handler  10  through an inlet duct  14 . Cooled air is conveyed away from the air handler  10  through outlet duct  12 . As the air is cooled, liquid in the air condenses and collects in the drain pan  16  located at the bottom of the air handler  10 . As is known, the drain pan  16  also can be a separate pan located below the air handler, and into which condensate drains from the air handler  10 .  
         [0019]    As shown in FIG. 2., the drain pan  16  typically includes an upper outlet  15  and a lower outlet  17 . The lower outlet  17  usually is connected to a drain pipe  70 , which drains the condensate from the drain pan. The drain pipe  70  typically leads to the outside of the building or to a drainage system within the building. The drain pipe  70  often includes a trap, such as a U-shaped trap  72  in order to form a water seal to prevent external air from entering the air handler  10  through the drain pipe  70 . Depending upon the building code where the air cooling system is installed, the upper outlet  15  is either blocked (i.e., not used) or it may be connected to a drainage system.  
         [0020]    The blockage detector  50  of the invention can be coupled to the upper outlet  15 . Accordingly, if a blockage occurs in the drain pipe  70 , the liquid level within the drain pan  16  will rise and reach the upper outlet  15  to which the blockage detector  50  is coupled. The blockage detector is water proof such that liquid will not leak from the upper outlet  15  when the blockage detector  50  is connected to it.  
         [0021]    As shown in FIG. 4, the blockage detector includes three contacts  52 ,  54  and  56 . Contact  54  is coupled to a first circuit that controls an alarm. Contact  56  is coupled to a second circuit that controls a supply of power to the air-cooling system  20 . Contact  52  is used with each of the contacts  54  and  56 , as will be described below, and will be referred to as the common contact.  
         [0022]    The blockage detector is coupled to the drain pan  16  such that the contacts are arranged having the vertical orientation illustrated in FIG. 4. In other words, the common contact  52  should be the lowermost of the three contacts, whereas the power-supply contact  56  should be the uppermost of the three contacts. The alarm contact  54  should be located between contacts  52  and  56 . It is understood that the three contacts do not need to be located in a straight line and do not need to be oriented perfectly vertically. However, it is only necessary that contact  56  be the uppermost, contact  52  be the lowermost, and contact  54  be located between contacts  52  and  56 . When liquid rises to the level at which the alarm contact  54  is located, current will pass between contacts  52  and  54 . This will cause an alarm circuit to be closed, thereby sounding an alarm. For example, referring to FIG. 1, a remote panel  40 , mounted at a convenient location within the building, for example, on a wall of the building near a thermostat, includes an audible alarm  42  and a visual alarm, such as a light  44 . When the alarm is sounded, the light  44  will be lighted, and the audible alarm  42  will emit its alarm sound. An audible alarm shutoff button  46  can be provided on the remote panel  40  in order to turn off the audible alarm  42 . Preferably, the light  44  remains lighted until the blockage is eliminated and the liquid falls below the level of contact  54 . The remote panel  40  also could be provided as part of a thermostat, as opposed to being a separate control panel.  
         [0023]    If the blockage is not eliminated quickly enough, the level of liquid in the drain pan  16  will continue to rise until it reaches the power-supply contact  56 . At that time, current will flow between the common contact  52  and the power-supply contact  56 , which will then cause the air-cooling system  20  to be turned off. Accordingly, no further condensate will collect, which prevents the drain pan  16  from reaching an overflow condition. The air-cooling system  20  will not be able to be turned back on until the blockage is eliminated and the liquid falls below the level of contact  56 .  
         [0024]    As illustrated in FIGS. 2 and 5, the blockage detector  50  preferably includes, on its rear surface, a two-pole test switch  57  and a light  59 . When the user presses the switch  57  once, the alarm circuitry is tested. When the switch  57  is pressed a second time, the power-supply circuitry is tested. In each instance, the light  59  will be illuminated if the circuitry is operating properly. The provision of the test circuitry, switch  57  and light  59 , are optional, and do not constitute a main aspect of the invention.  
         [0025]    In addition, as illustrated in FIG. 2, it is preferable to include some kind of indicia  51  on the external surface of the blockage detector  50  so as to indicate the proper orientation of the blockage detector  50 , such that the contacts  52 ,  54 ,  56  are provided in the necessary orientation illustrated in FIG. 4 (i.e., with contact  56  being uppermost, contact  52  being lowermost, and contact  54  being located between contacts  56  and  52 ) when installed on the drain pan  16 .  
         [0026]    A schematic diagram of the circuitry associated with the blockage detector  50  and the control panel  40 , as well as the electrical connection of those elements to the air cooling system  20  is shown in FIG. 3. In FIG. 3, the building includes a transformer  100  that converts a 240 volt or a 120 volt power supply to the common 24 volt power supply. The lines labeled X 1  constitute the red (or hot) lines, whereas the lines labeled X 2  are neutral lines. The alarm system illustrated in FIG. 3 also is coupled to a dialing unit  90  that will automatically contact a predetermined number, for example, the telephone or pager of an HVAC technician when the alarm condition occurs.  
         [0027]    The blockage detector  50  includes a first actuator  62  that is coupled to the common contact  52 , the power-supply contact  56  and to an on/off switch  66 . A second actuator  64  is coupled to the common contact  52 , the alarm contact  54  and to a second on/off switch  68 . The actuators  62  and  64  can be solenoids or other actuators, such as electronic switches. When no blockage is present, and liquid does not reach the levels of contacts  54  or  56 , the switch  66  is closed, whereas the switch  68  is open. In this state (shown in FIG. 3), power is supplied to the air-cooling system  20  such that it operates as usual.  
         [0028]    When a blockage occurs in the drain pipe  70 , such that the level of liquid within the drain pan  16  rises to the level of the alarm contact  54 , actuator  64  will cause the on/off switch  68  to close. This will supply power to the alarm system within the remote panel  40 . Accordingly, the alarm light  44  will be lighted, and an audible alarm, if present, will sound. In addition, the dialing system  90 , if provided, will contact the predetermined number so as to request a service call. Switch  66  remains closed such that the air-cooling system  20  will continue to operate as normal. As noted previously, if button  46  is provided, it can be pressed to turn off the audible alarm; however, the visual alarm  44  preferably continues to be lighted.  
         [0029]    If the blockage is not eliminated, the liquid will continue to rise within the drain pan  16  until it reaches contact  56 . When the liquid reaches contact  56 , actuator  62  will cause the on/off switch  66  to open, which will prevent power from being provided to the air-cooling system  20 . The alarm system will continue to operate and sound its alarm. Accordingly, no further condensate will collect, which prevents the drain pan  16  from reaching an overflow condition. The air-cooling system  20  will not be able to be turned back on until the blockage is eliminated and the liquid falls below the level of contact  56 .  
         [0030]    In this way, the technician or homeowner will be provided with an opportunity to eliminate the blockage before the air-cooling system  20  is turned off. If, on the other hand, for some reason the blockage is not eliminated, the air-cooling system  20  will ultimately turn off so that water damage will not occur.  
         [0031]    As noted previously, it is desirable to provide indicia  51  on the blockage detector so that it will be attached to the drain pan  16  with a proper orientation. FIG. 4 illustrates one preferred way of achieving this goal. In the FIG. 4 embodiment, the sensor housing  50   a  has a rectangular (e.g., square) cross-section with the word “TOP” printed as the indicia  51  on one of the four surfaces.  
         [0032]    The sensor housing  50   b  illustrated in FIG. 6 has a circular cross-section with indicia  51  such as the word “TOP” or the words “THIS END UP” provided at the appropriate location thereon.  
         [0033]    [0033]FIG. 6 also illustrates one preferred construction of the blockage detector. A fitting  53  is provided with a threaded end for attachment to the outlet  15  of the drain pan  16 . An O-ring  58  is placed on the end of the fitting  53  opposite from the end containing the threads. The diameter of the O-ring  58  is the same as the diameter of the end of the fitting  53  against which the O-ring  58  is placed. A cap  55  has an internal diameter that slides over the O-ring  58  and the non-threaded end of the fitting  53 . Accordingly, the cap  55  is slid over the non-threaded end of the fitting  53  such that the O-ring  58  is held between the end of the fitting  53  and an internal surface of the cap  55  through which a hole  60  is formed. The hole  60  is provided in the cap  55  such that the sensor housing  50   b  (or  50   a  of FIG. 4) can slide through the hole  60 , and through the O-ring  58  and into the fitting  53 . The O-ring  58  seals against the external surface of the sensor housing  50   b . Since the fitting  53  is hollow, the contacts of the sensor housing will be exposed to the liquid within the drain pan  16 .  
         [0034]    The fitting  53  shown in FIG. 6 has external threads, and is for use with a drain pan having an internally threaded (female) drain outlet. Of course, the structure of the fitting will vary depending on the structure of the drain pan outlet. For example, the fitting could be of the female type having internal threads, for engagement with an externally threaded male type drain pan outlet. As another alternative example, the fitting could be a standard coupling with no threads for engagement with a drain pan outlet that does not include threads.  
         [0035]    While the present invention has been described with reference to preferred embodiments thereof, it is to be understood that the invention is not limited to the preferred embodiments or constructions. To the contrary, the invention is intended to cover various modifications and equivalent arrangements. In addition, while the various elements of the preferred embodiments are shown in various combinations and configurations, which are exemplary, other combinations and configurations, including more, less or only a single element, are also within the spirit and scope of the invention.