Abstract:
A coupling harness useful with a HVAC mini-split system includes a first interface connected to a thermistor, a second interface connected to a condensate overflow sensor and a control device interface connected to a HVAC electronic control device. The first and second interfaces can notify the control device interface of the existence of an alarm condition of the thermistor and condensate overflow sensor, respectively. The control device interface can actuate the HVAC electronic control device in response to such notifications that an alarm condition exists for the thermistor or condensate overflow sensor.

Description:
CROSS REFERENCE TO RELATED APPLICATIONS 
       [0001]    This Application is a continuation application of and claims priority to U.S. patent application Ser. No. 14/715,068 filed on May 18, 2015 and entitled “Coupling Harness For HVAC Mini-Split System,” which is a continuation application and claims priority to U.S. patent application Ser. No. 12/806,977 filed on Aug. 25, 2010 and entitled “Solid State Control System,” both of which are hereby incorporated by reference herein in their entirety. 
     
    
     FIELD OF THE DISCLOSURE 
       [0002]    The present disclosure relates generally to HVAC systems, and more particularly, to mini-split HVAC systems. 
       BACKGROUND 
       [0003]    Air handling systems such as air conditioning systems typically have a condensate drain pan to collect condensate. 
         [0004]    Often removal of the condensate requires pumping the condensate from the condensation drain pan. Commonly, a drain pan system includes a sensor placed in the drain pan to measure the level of the condensation therein. When the condensate level reaches a predetermined level, the sensor generates a signal sent to a sensor switching circuit to activate the pump or stop operation of the compressor. 
         [0005]    HVAC systems know as mini-split systems present a particularly troublesome challenge. Mini-split systems comprise of two basic units—a compressor and multiple air handlers. The air handler is typically mounted on the wall in the space to be cooled. These air handlers are designed to be compact resulting in limited space for an overflow switch and condensate sensor. Specifically, systems use refrigerant lines together power and control wiring to connect the outdoor compressor to the individual indoor air handlers. The technology, developed in the 1950s, is called split-ductless or mini-split and is the primary method for conditioning spaces within a home or commercial building in countries around the world. Mini-split systems allow each space with an indoor air-handler unit to be controlled independently from other rooms, thus providing individualized comfort control within a home. 
         [0006]    In such mini-split systems, the compressor is connected to existing house voltage and supplies voltage to the air handlers. 
         [0007]    In addition, a communications link is used to coordinate the operation of the two basic units. As a result, any electronics that would utilize the power supply has the potential of disrupting the communication link. Thus, any effort to provide a condensate removal system would require an electrically isolated battery powered system. 
         [0008]    In order to shut down the highly integrated electro-mechanical mini-split system, a condensate control system can be tapped into a commonly found thermistor used to measure the evaporator temperature forming part of mini-split control loop. As designed, if the thermistor is broken or indicates a bad reading the compressor is shut down. This thermistor can be used to open the circuit when excess condensate is sensed in the condensate drain pan to shut down the compressor. 
         [0009]    The present invention employs a solid state relay or switch to control the thermistor without intruding or compromising the integrity of the power supply or communication link of existing mini-split systems. 
       BRIEF SUMMARY OF THE DISCLOSURE 
       [0010]    The present invention relates to a control system to selectively control the operation of the compressor of a mini-split air conditioning system that includes a compressor and at least one remote air handler. 
         [0011]    The present invention is a method of providing alarm signals to a HVAC mini-split system having a thermistor, a condensate overflow sensor and a HVAC electronic control device. The method includes removably engaging a unitary, releasable, self-contained, alarm coupling harness (having first, second and third electrically-coupled interfaces) with the HVAC mini-split system by electrically connecting the first interface with the thermistor, electrically connecting the second interface with the condensate overflow sensor and electrically connecting the third interface with the HVAC electronic control device. At least one among the first and second interfaces directs a signal to the third interface when an alarm condition exists in the thermistor and/or condensate overflow sensor, respectively. In response to a signal received from either the first or second interfaces, the third interface notifying the HVAC electronic control device that an alarm condition exists. 
         [0012]    The control system comprises a condensate sensor disposed to sense when condensate within the condensate drain pan reaches a predetermined level and a control device operatively coupled between the condensate sensor the control sensor and the air handler electronic system to turn off the compressor when the predetermined operating conditions exists. 
         [0013]    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 
         [0014]    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: 
           [0015]      FIG. 1  is a block diagram of the control system of the present invention in combination with a mini-split air conditioning system. 
           [0016]      FIG. 2  is an exploded view of the control system of the present invention. 
           [0017]      FIG. 3  is a detailed view of the coupling harness of the control system of the present invention. 
           [0018]      FIG. 4  is a circuit diagram or schematic of the control system of the present invention. 
       
    
    
       [0019]    Similar reference characters refer to similar parts throughout the several views of the drawings. 
       DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS 
       [0020]    The present invention relates to a control system to selectively control the operation of the compressor of a mini-split air conditioning system that includes a compressor and at least one remote air handler shown as  10  and  12  respectively in  FIG. 1 . 
         [0021]    As shown in  FIG. 2 , the air handler  12  includes an evaporator  14  coupled in closed-loop fluid communication with the compressor  10  by refrigerant lines or conduits  16  and  18 , a condensate drain pan  20  disposed to receive or capture condensate from the evaporator  14  and a condensate drain  22  to direct or carry condensate from the condensate drain pan  14  to a collection or run-off site (not shown). The air handler  12  further includes an air handler electronics system  24  coupled to multiple or redundant control sensors or thermistors  26  and  28  disposed in heat exchange relationship relative to the evaporator  14 . The control sensors or thermistors  26  and  28  are coupled to the air handler electronics system  24  and the control device  36  as described hereinafter and ultimately to the compressor  10  by air handler power/communication conductor or line  30  and  31 . The control sensor or thermistor  28  generates a sensor control signal when a predetermined operating condition such as a predetermined temperature is sensed in the evaporator  14  that causes the air handler electronic system  24  to generate a compressor control signal fed over the air handler power/communication conductor or line  30  to stop or turn-off the compressor  10  as described more fully hereinafter. The compressor  10  is coupled to an external power source (not shown) by a power supply line or conductor  32 . 
         [0022]    As shown in  FIG. 1 , the control system comprises a condensate sensor  34  disposed to sense when condensate within the condensate drain pan  20  reaches a predetermined level and a control device generally indicated as  36  operatively coupled to the condensate sensor  34  by sensor signal conductors or lines  38  and  40  and to the control sensor or thermistor  26  by a control signal conductor  42  and to the air handler electronic system  24  of the air handler  14  by conductor or line or  44  to control the operation of the control sensor or thermistor  26  and, in turn, the compressor  10  as described more fully hereunder. 
         [0023]    As shown in  FIGS. 2 and 4 , the condensate sensor  34  comprises a first condensate sensing probe  46  and a second condensate sensing probe  48  coupled or connected to the control device  36  that comprises a battery power source, low battery indicator or alarm and a solid state isolated control relay or switch generally indicated as  50 ,  114  and  54  respectively enclosed within a housing and a back plate generally indicated as  56  and  58  respectively. 
         [0024]      FIG. 3  depicts a coupling harness comprising a control sensor interface connector  60  and an air handler electronics system interface connector  62  connected to control sensor or thermistor  26  and the air handler electronic system  24  by conductors  64 ,  66  and  68 , and connected to a control device interface connector  70  coupled between the control sensor or thermistor  26  and the air handler electronics system  24  by the conductors  42  and  44  respectively to operatively integrate the control system  36  with an existing mini-split air conditioning system without compromising the integrity of the communication and control links  30  and  31 . 
         [0025]      FIG. 4  is a schematic diagram of the control system  36  comprising the battery power source  50 , the low battery indicator/alarm  52  and the solid state control relay/switch  54 . 
         [0026]    The solid state relay/switch  54  is powered by the isolated external battery power source  50  connected between a positive voltage socket or connector  110  and a ground and negative voltage socket or connector  112 . 
         [0027]    The low battery indicator/alarm  52  comprises a buzzer or audible alarm  114  coupled to the output of a comparator  116  coupled to the voltage power source  50  and a fixed reference voltage  118  to generate a low battery indication when the voltage from the battery power source  50  reaches a minimum predetermined voltage such as 1.2 volts. The low battery indicator/alarm  50  further includes scaling resistors  120 ,  122  and  124 , timing resistors  126  and  128  and timing diode  130 , feedback resistors  132  and  134 , capacitor  136 , and resistor  137 . 
         [0028]    A positive voltage socket or connector  138  is coupled between the battery power source  50  through current limiting resistor  140  and the first condensate sensing probe  46  through the first sensor signal conductor or line  38  and a socket or connector  142  is coupled between the solid state relay/switch circuit described hereinafter and the second condensate sensing probe  48  through the second sensor signal conductor or line  40 . 
         [0029]    The solid state relay/switch circuit comprises an input stage generally indicated as  144  coupled to an output stage generally indicated as  146  by an intermediate control stage generally indicated as  148 . 
         [0030]    The input stage  144  comprises voltage limiting zener diode  150 , resistor  152  and filter capacitor  154  combination and resistor  156  to hold the voltage low and configured to receive current through socket or connector  142  when the level of condensate within the condensate drain pan  20  is such that the tips of first condensate sensing probe  46  and the second condensate sensing probe  48  are submersed in the condensate completing the circuit causing current to flow through the input stage  144 . The intermediate control stage  148  comprises a field effect transistor  158  coupled to the output of the input stage  144  such that when current flows through the input stage  144  the field effect transistor  158  is turned on. 
         [0031]    The output stage  146  comprises a opto isolator or opto coupler  160  including a light emitting diode (LED)  162  coupled between positive voltage VCC through resistor  164  and field effect transistor  158  of intermediate control stage  148 , and a pair of field effect transistors  166  and  168  coupled to the control sensor or thermistor  26  and the evaporator  14  through sockets or connectors  170  and  172 , and control signal conductor or line  42  and control signal conductor or line  44  respectively such that when field effect transistor  158  of intermediate control stage  148  is conducting LED  162  of opto isolator or opto coupler  160  is energized driving the field transistors  166  and  168  causing the control sensor or thermistor  26  to generate a sensor control signal whereby the circuit through the air handler electronic system  24  to generate an “off” or compressor signal fed to the compressor  10  through the air handler power/communications conductors or lines  30  and  31  shutting down the compressor  10  when the condensate level reaches a predetermined level in the condensate drain pan  20  as sensed by the first condensate sensing probe  46  and the second condensate sensing probe  48  thus completing a circuit to actuate the control sensor or thermistor  26 . 
         [0032]    The condensate can be drained or pumped from the condensate drain pan  20  through the condensate drain conduit  22 . 
         [0033]    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. 
         [0034]    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.