Abstract:
A control device including a condensate sensor to generate a control signal when the condensate sensor detects condensate accumulated in a condensate reservoir has reached a predetermined level wherein the condensate sensor comprises a first sensor pin and second sensor pin coupled to a control section by a first detection sensor component and a second detection sensor component respectively balanced to reduce electrolysis that occurs when the condensate reaches the predetermined level that would otherwise cause the first sensor pin and the second sensor pin to corrode excessively.

Description:
CROSS-REFERENCE 
       [0001]    This application claims priority from pending provisional patent application Ser. No. 61/795,455 filed Oct. 17, 2012. 
     
    
     BACKGROUND OF THE INVENTION 
       [0002]    1. Background of the Invention 
         [0003]    A control device for use with a condensate sensor to generate a control signal to activate or deactivate a switch when condensate within a condensate reservoir reaches a predetermined level. 
         [0004]    2. Description of the Prior Art 
         [0005]    An overflow of condensate/water can cause serious damage to structures such as a home or business if undetected. Numerous devices and systems have been designed to detect water overflow, water leakage or rising water. Generally, when water is detected, a sensor activates a warning device and other devices to reduce or mitigate potential water damage. 
         [0006]    A common source of potential water/condensate damage are heating and air conditioning systems. Many such HVAC systems ground the Air Handler and Evaporator to a 24-VAC “Transformer-Ground”. To save on the cost of a center-tap transformer and associated equipment and material, such systems may opt for a non-center-tap transformer. By so doing, the transformer (Common) wire which is the return line is connected to system/chassis ground. In such case, when the air handler comes on the evaporator immediately begins to remove moisture from the air and generates condensate H 2 O. Condensate slowly drips along the evaporator coil down to the primary drain pan which is typically made out of plastic. The complete air handler is now grounded to system ground which is at the same potential of 24-VAC transformer “Common” due to the absence of a center-tap transformer. Because the primary drain pan is fastened to the evaporator coil, when condensate water backs up the drain line, the primary pan fills up with water. When this occurs, where both are fastened together, the metal part of the evaporator coil and primary drain pan come into contact with each other due to condensate water. At this point, the water inside the primary drain pan sees the same 24-VAC transformer “Common” voltage potential. This creates a potential problem with respect to voltages throughout the condensate detection and control system. 
         [0007]    U.S. Pat. No. 5,428,347 discloses water sensor for a plurality of water-related appliances or equipment to simultaneously monitor and, in the event of sensing water with respect to any one of the several devices being monitored, appropriate action, such as shutting off the power to the unit is taken, and shutting off the water supply to that particular unit. The sensor comprises a plurality of electronic circuits which include thermal circuit breakers acting as a “fault memory.” When a fault occurs, the circuit breakers are tripped. Thus, the fault condition will be “remembered” indefinitely until human intervention. 
         [0008]    U.S. Pat. No. 8,169,314 relates to a drain pan system for activating a pump when a predetermined water level is detected in a drain pan. The drain pan system includes the drain pan, the pump, a water sensor, first and second inputs, a control section and a switching device. The water sensor is coupled to the drain pan for detecting a level of water in the drain pan to generate a drain pan water level detection signal in response to detection of the level of the water in the drain pan equal to or greater than a predetermined water level. The pump is coupled to the drain pan and, when activated, pumps the water from the drain pan. 
         [0009]    U.S. Pat. No. 5,404,048 discloses a liquid sensing switch for use primarily in sensing the bilge water level aboard a boat. The switch is designed with a high input impedance and a high trigger sensitivity so that the presence of a liquid may be detected by using a remotely located single wire probe. The probe is able to sense immersion into low conductivity liquids or into liquids where no hardwired ground is provided, such as within fiberglass boat hulls. In order to prevent false triggering and cyclic operation of the bilge pump, the liquid sensing switch provides a time delay before it is activated, as well as a further time delay before being deactivated. 
         [0010]    U.S. Pat. Nos. 4,736,622 and 4,736,623 show a method for testing for leaks in above ground tanks of liquid having a lower specific gravity and a lower electrical or thermal conductivity than water. 
         [0011]    U.S. Pat. No. 6,041,611 discloses a system for cleaning-out a condensate drain line operatively associated with an air-conditioner that contains an evaporator coil and a primary drain pan. The system comprises sensor means, operatively associated with a secondary pan, for measuring the level of condensation within the secondary pan and activating an alarm once a predetermined level is reached. 
         [0012]    While some of the prior art may contain some similarities relating to the present invention, none of them teach, suggest or include all of the advantages and unique features of the invention disclosed hereunder. 
       SUMMARY OF THE INVENTION 
       [0013]    The present invention relates to a control device to detect condensate/water that could damage property or equipment when water or condensate reaches a predetermined level within a condensate reservoir. Electrical current flows between two electrodes or pins when in water or condensate to activate a control sensor to indicate the presence of water or condensate. 
         [0014]    In operation, a transformer provides power at the pins or electrodes. Normally once this condition exists, a high voltage is induced into the electrodes. This induced voltage is high enough to cause significance electrolysis and corrosion damage to the electrodes. To reduce electrolysis, the values of certain electronic components within the control device are selected. 
         [0015]    Thus the condensate sensor detects condensate/water in such a manner to reduce electrolysis that causes oxidation on the pins or electrodes that would otherwise corrode or damage the pins or electrodes. The process comprises of passing a small amount of current through the two electrodes or pins by applying an electrical potential across the electrodes or pins immersed in the condensate or water. By reducing the potential between the electrodes or pins corrosion is kept to a minimum. 
         [0016]    Once installed in an HVAC equipment, the sensor should be capable of remaining active upon detection of condensate or water for a period of up to a week without degradation of the electrodes. The pins or electrodes of the present invention remain active in condensate or water for up to thirty (30) days. In other words, the circuit is designed by selecting the values of the electronics and minimizing the voltage between the electrodes or pins. 
         [0017]    The invention accordingly comprises the features of construction, combination of elements, and arrangement of parts which will be exemplified in the construction hereinafter set forth, and the scope of the invention will be indicated in the claims. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0018]    For a fuller understanding of the nature and object of the invention, reference should be had to the following detailed description taken in connection with the accompanying drawings in which: 
           [0019]      FIG. 1  is a schematic diagram of the control device of the present invention. 
       
    
    
       [0020]    Similar reference characters refer to similar parts throughout the several views of the drawings. 
       DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
       [0021]    The present invention relates to a control device including a condensate sensor to generate a control signal when the condensate sensor detects condensate accumulated in a condensate reservoir has reached a predetermined level such as shown in U.S. Pat. No. 8,169,314. 
         [0022]    As shown in  FIG. 1 , the control device comprises an input section  10  coupled to a control or amplifier section  12  through an AC voltage rectification section  14 , an output section  16  coupled through a control signal generator section  18  to the control section  12  and a condensate sensing input section  20  coupled to the control section  12 . 
         [0023]    The input section  10  comprises a first terminal  22  coupled to the positive or hot output of the secondary winding of transformer (not shown) and a second terminal  24  coupled to the negative or common output of the secondary winding of the transformer (not shown). 
         [0024]    The AC voltage rectification section  14  comprises a bridge rectifier generally indicated as  26  including a first pair of diodes each indicated as  28  and a second pair of diodes each indicated as  30  coupled across the first terminal  22  and the second terminal  24 . The first pair of diodes  28  and the second pair of diodes  30  are coupled between ground GND and a filter or capacitor  32  coupled to GND. 
         [0025]    The control section  12  or amplifier comprises a first resistor  34  coupled to the transistor  36  and a second resistor  38  coupled to the base of the transistor  36 . 
         [0026]    The condensate sensing input section  20  comprises a first sensor terminal  40  coupled to a first sensor pin (not shown) and a second sensor terminal  42  coupled to a second sensor pin (not shown). The first sensor terminal  40  is coupled to the control section  12  and the AC voltage rectification section  14  through a resistor  44 ; while, the second sensor terminal  42  is coupled to the control section  12  through a resistor  46  and a field-effect transistor  48 . The condensate sensing input section  20  further includes a time delay section  50  comprising an RC circuit including a resistor  52  and a capacitor  54  coupled between the resistor  46  and the field-effect transistor  48  and a resistor  56  arranged in parallel between the first resistor  52  and GND. 
         [0027]    The first sensor terminal  40  and the resistor or impedance  44  comprise a first detection sensor component; while he second sensor terminal  42  and the resistor or impedance  46  comprise a second detection sensor component. 
         [0028]    The control signal generator  18  comprises a plurality of branches each coupled between the transistor  36  of the control section  12  and a control switch generally indicated as  68 . The branches comprise a first resistor  58  and an LED  60 , a noise snubber including a second resistor  62  and a capacitor  64 , and a free wheeling diode  66 . The control switch  68  operable in a first state or position and a second state or position may comprise a coil  70  and a single pole/double throw switch element or member  72  movable between a first or closed position and a second or open position to couple a first output terminal  74  or a second output terminal  76  to the control signal generator  18  to receive condensate signals from the condensate sensing input section  20  through the control section  12  when condensate within the condensate reservoir (not shown) reaches a predetermined level as described hereinafter. 
         [0029]    The control switch  68  may comprise either a normal open or inactive state or a normally closed or active state without effecting the operation of the control device. 
         [0030]    The condensate sensing input section  20  may further comprise second set or pair of condensate sensors. Specifically, a first sensor probe (not shown) is coupled to a third terminal  78 ; while, a second sensor probe (not shown) is coupled to a fourth terminal  80 . 
         [0031]    A circuit protection device  84  such as a fuse is coupled between the first terminal  22  of the input section  10  and the bridge rectifier  26  of the AC voltage rectification section  14 . 
         [0032]    Normally in operation, when water or condensate is below the predetermined level in the condensate reservoir (not shown) there is no current flow between the first sensor pin (not shown) and the second sensor pin (not shown). When the water or condensate reaches the predetermined level, the impedance of the water or condensate allows current to flow from the AC power source through the bridge rectifier  26 , the first detection sensor component including the resistor or impedance  44 , the first sensor terminal  40  and the second sensor terminal  42  through the second detection sensor component including the resistor or impedance  46  turning the field-effect transistor  48  on causing current to flow through the transistor  36  to energize the coil  70  moving the single pole/double throw switch element or member  72  to open or close; activate or deactivate to send a continual signal to an external device. The third sensor terminal  78  and the fourth sensor terminal.  80  operate similarly when condensate or water is sensed between the first sensor probe (not shown) and the second sensor probe (not shown). 
         [0033]    The time delay section  50  prevents the control device from generating false readings or hunting when the condensate or water level is fluctuating at the predetermined level in the condensate reservoir (not shown). 
         [0034]    When installed the HVAC is grounded to system ground which is at the same potential of the 24 VAC transformer (not shown) due to the absence of a center-tap transformer. Since the control device is powered by the 24 VAC transformer (not shown) across the first terminal  22  and the second terminal  24  a voltage is induced in the first sensor pin (not shown) and the second sensor pin (not shown) that can cause a significant electrolysis and damage. Note that the resistor or impedance  46  is electrically connected to the transformer common at the same potential as at the pins (not shown). 
         [0035]    To reduce or mitigate the electrolysis the value of the first detection sensor component and the second detector sensor component are selected or balanced relative to each other and the impedance of the condensate or water. Specifically, the impedance of the first detector sensor component and the second detector sensor component are substantially equal; at least 20 megaohms each and preferably 30 megaohms each. 
         [0036]    Of course, the various electronic components may be digitized capable of the same functions allowing for the use of a microprocessor. 
         [0037]    Similarly, when the condensate control system is used with an HVAC system when a voltage is not induced between the first sensor pin (not shown) and the second sensor pin (not shown) electrolysis can be minimized by the selection of particular values of the various electronic components. 
         [0038]    In addition, although a 24 VAC power source is described, a +24 VDC may be used. In addition, by selecting circuit components of different values, a +3 VDC, +5 VDC, +9 VDC and a +12 VDC may be used to trigger or actuate the condensate control device. 
         [0039]    It will thus be seen that the objects set forth above, among those made apparent from the preceding description are efficiently attained and since certain changes may be made in the above construction without departing from the scope of the invention, it is intended that all matter contained in the above description or shown in the accompanying drawing shall be interpreted as illustrative and not in a limiting sense. 
         [0040]    It is also to be understood that the following claims are intended to cover all of the generic and specific features of the invention herein described, and all statements of the scope of the invention which, as a matter of language, might be said to fall therebetween.