Abstract:
A control is provided for controlling the operation of a climate control system, which includes a processor that is capable of receiving power from a low voltage power supply adapted to be connected to an external alternating current power source, or a second external low voltage power supply. The processor is capable of storing diagnostic information pertaining to the operating status of at least one component of the climate control system. The processor is configured to retrieve stored diagnostic information from memory pertaining to the climate control system and send the diagnostic information to the display means when the processor receives power from the external low voltage power supply and detects the absence of a connection to an external alternating current power source.

Description:
BACKGROUND OF THE INVENTION 
   The present invention is generally related to controls for air conditioning and fuel-fired heating systems, and more specifically to controls for communicating diagnostic information relating to an HVAC component. 
   Many controls for controlling an air conditioner or heating appliance have the capability of reporting diagnostic information pertaining to various components of such climate control systems. The controls and components of these systems are often unnecessarily removed and replace by a contractor when troubleshooting or repairing a non-operating climate control system. Frequently, the removed controls or components are returned to a distributor for manufacturer&#39;s warranty credit. While such prior art controls provided diagnostic information pertaining to the control or various components of the climate control system, this diagnostic information was not available to the distributor once the control or component was removed from the climate control system. Furthermore, even if the distributor supplied power to the control or component to test the returned item, the distributor would be unable to determine the operating condition absent the climate control system. This prevents the distributor from determining whether the returned item is defective or in good operating condition. A distributor&#39;s acceptance of returned controls or components that are not defective results in unwanted and unnecessary manufacturer&#39;s warranty costs. 
   SUMMARY OF THE INVENTION 
   There is provided, in accordance with one aspect of the invention, a control for a heating system or an air conditioning system that comprises a microprocessor capable of determining the operating status of both the control and/or other components in the system, and a first low voltage power supply circuit connected to an external alternating current power source. The control further comprises a low voltage receptacle socket for connecting the control to a second external low voltage plug-in power supply, where the microprocessor is powered by either the first low voltage power supply circuit or the second external low-voltage power supply. When the microprocessor is powered by only the external low voltage power supply, the microprocessor detects the absence of an external alternating current power source and responsively retrieves and communicates stored diagnostic information relating to the operating status of at least the control. The microprocessor may also retrieve and communicate stored diagnostic information relating to at least one other component of the climate control system. 
   In another aspect of the present invention, a thermostat for controlling an air conditioner or heating appliance of a climate control system is provided that is capable of being powered after removal from the climate control system, for the purpose of retrieving operating condition information pertaining to the control or a component within the system. 
   In yet another aspect of the present invention, some embodiments of a thermostat may provide historical diagnostic information pertaining to the operation of the control or a component in the system, to enable evaluation of the historical diagnostic information relating to the operation or eventual failure of the control. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
       FIG. 1  is a diagram of a building having a climate control system that includes one embodiment of a control according to the principles of the present invention. 
       FIG. 2  is a schematic of one embodiment of a control according to the principles of the present invention. 
   

   DETAILED DESCRIPTION OF THE INVENTION 
   A typical climate control system for a building comprising a preferred embodiment of a control for an outside air conditioning condenser unit  100  or a heating appliance  110  in accordance with the present invention is shown in  FIG. 1 . The air conditioning unit  100  comprises a control  102 , and the heating appliance  110  comprises an ignition control module  112 . The controls for the climate control systems are each connected to an alternating current power source  122  within the building. Such air conditioning units and heating appliances may be removed and replaced by a contractor, and often are returned to a distributor for manufacturer&#39;s warranty credit. 
   A schematic diagram of one preferred embodiment of a control is shown in a schematic in Fig  2 . The control  20  comprises a microprocessor  22  in connection with a low voltage power supply  50 . This first low voltage power supply  50  for the control may be a 5 volt power supply for example, which may be connected to an external alternating current power source. In the preferred embodiment, the 5 volt power supply is connected at  40  to an external alternating current power source, which may be a 24 vac power source  24 , for example. The control  20  further comprises a connector  92  adapted to be connected to a second external low voltage power supply  96 . The connector is preferably a plug-in connector  92  for connection to an external low voltage wall plug-in power supply. The control is typically connected to a thermostat, and may also be connected to other components such as a pressure switch, igniter and gas valve in the case of a heating system or a compressor and condenser motor in the case of an air conditioning unit. The microprocessor  22  receives power from either the first low voltage power supply  50 , or from a second external low voltage power supply  96  when a second low voltage power supply  96  is connected to the connector  92 . As shown in  FIG. 2  the 5 volt power supply  50  and the second external low voltage power supply connector  92  are both connected at node  90  to the microprocessor  22  in a manner such that the microprocessor may be powered by either low voltage power supply ( 50 ,  96 ). The low voltage power supply  50  is preferably a half wave regulated power supply, and comprises a diode  42  in series with a transistor  48 , and also a regulating capacitor  44  and zener diode  46  for gating the transistor  48 . The microprocessor may, for example, be capable of observing the number of failed compressor motor starts or condenser motor starts for an air conditioning unit. The microprocessor may also be capable of detecting a failure of an element in the control itself, and may responsively communicate the fault or failure of the control when later prompted. The microprocessor of the present invention is preferably a ST72C334 microprocessor  22  manufactured by ST Microelectronics, but may alternatively be a comparable microprocessor that is suitable for use in such applications. 
   The microprocessor  22  further comprises a non-volatile memory, which can be used to store the historical diagnostic information for future evaluation. Specifically, the microprocessor  22  may determine an operating condition or status based on a predetermined number of historical failures, and store the determined operating status in the non-volatile EEPROM memory of the microprocessor  22 . If power to the control is interrupted, the historical diagnostic information and operating status will remain stored in EEPROM memory for future retrieval. An example of a situation where power could be interrupted is when the control is removed by a service technician for evaluation or return. After removal, the microprocessor  22  is capable of detecting the absence of a connection to the external alternating current power source  24 , when the microprocessor  22  receives power from a second external low voltage power supply  96  that is connected to the connection  92 . Specifically, when power to the control  20  is restored via an external  5  volt power source  96 , the microprocessor  22  checks a connection  94  to verify the presence of a connection to an external alternating current power source at  40 . The absence of an input at  94  to the microprocessor  22  indicates to the microprocessor that the control  20  is being powered through the second external low voltage power supply connection  92 . Accordingly, the microprocessor  22  responsively retrieves the last stored operating condition or status and outputs a signal to a communication means for communicating information, such as the gate of a transistor  54  for switching 5 volts to an LED  56  for communicating the diagnostic information. It should be noted that the control may alternately communicate the signal to a device or location external to the control. The LED may be flashed on and off a predetermined number of times to indicate the control is in good operating condition, and another predetermined number of times to indicate a separate component is in good operating condition. The control may also flash the LED a predetermined number of times to indicate whether the control or a component is defective. In one embodiment of a control in accordance with the principles of the present invention, the control may be part of an outside air conditioning condenser unit that comprises a compressor that may have been removed by a contractor for return to a distributor. The distributor would be able to insert a standard low voltage power supply plug to the control and subsequently retrieve and communicate information relating to the control&#39;s operation for warranty evaluation. The control may further retrieve and communicate diagnostic information relating to the compressor&#39;s operating condition for warranty evaluation. The contractor would also be able to plug in a low voltage power supply to the control prior to removing the compressor, to determine whether the control or the compressor would be accepted for return under the manufacturer&#39;s warranty. In the event the control indicates a component such as a compressor is defective, the control can be further prompted to communicate historical diagnostic information for evaluating the cause of failure of the compressor. 
   In a second embodiment of a control in accordance with the principles of the present invention, the control may be part of a heating system such as a furnace or heat pump. The second embodiment similarly possesses a microprocessor  22  and a first low voltage power supply connected to an external alternating current power source. The first low voltage power supply may be a 5 volt power supply, for example. The first power supply and the second external low voltage power supply connector  92  are both connected at node  90  to the microprocessor  22  in a manner such that the microprocessor may be powered by either low voltage power supply. The low voltage power supply is preferably a half wave regulated power supply, and comprises a diode  42  in series with a transistor  48 , and also a regulating capacitor  44  and zener diode  46  for gating the transistor  48 . The microprocessor may for example be capable of observing the number of occurrences of a failed ignition attempt or pressure switch closure for a heating appliance, or the failure of the operation of the control itself. The microprocessor may also be capable of detecting a failure of an element in the control itself, and may responsively communicate the fault or failure of the control when later prompted. 
   The microprocessor  22  further comprises a non-volatile memory, which can be used to store the historical diagnostic information for future evaluation. Specifically, the microprocessor  22  may determine an operating condition or status based on a predetermined number of historical failures, and store the determined operating status in the non-volatile EEPROM memory of the microprocessor  22 . If power to the control is interrupted, the historical diagnostic information and operating status will remain stored in EEPROM memory for future retrieval. An example of a situation where power could be interrupted is when the control is removed by a service technician for evaluation or return. When power to the control  20  is restored via an external 5 volt power source, the microprocessor  22  checks a connection  94  to verify the presence of an external alternating current power source  40 . The absence of an input at  94  to the microprocessor  22  indicates to the microprocessor that the control  20  is being powered through the second external low voltage power supply connection  92 . Accordingly, the microprocessor  22  responsively retrieves the last stored operating condition or status and outputs a signal to the gate of a transistor  54  for switching 5 volts to an LED  56  for communicating the diagnostic information. It should be noted that the control may alternately communicate the signal to a device or location external to the control. The LED may be flashed on and off a predetermined number of times to indicate the control is in good operating condition, and another predetermined number of times to indicate a separate component is in good operating condition. The control may also flash the LED a predetermined number of times to indicate whether the control or a component is defective. Such diagnostic information would be of value to both the service technician and the manufacturer in evaluating an operating failure of the control or a component in the system. 
   It should be noted that the method of communicating the diagnostic errors or information may alternatively be performed using an LCD display in place of an LED. The LCD display would be able to display a text message or a number indicating an operating condition or status. The LCD display would further be able to display historical diagnostic information for evaluating failures. The control may alternatively use an LED capable of displaying at least two colors, for indicating the control is either in good operating condition or is defective. Likewise, the control may also be able to communicate the diagnostic information to a computer, palm, or other external device through a simple connection such as an RS485 connection, or the like. 
   Additional design considerations, readily apparent to one of ordinary skill in the art, such as the modification of the control to provide an LCD display for display of diagnostic information, may also provide improved appliance operation. It should be apparent to those skilled in the art that various modifications such as the above may be made without departing from the spirit and scope of the invention. More particularly, the apparatus may be adapted to any of a variety of different air conditioning units, heat pump units and heating appliance controls. Accordingly, it is not intended that the invention be limited by the particular form illustrated and described above, but by the appended claims.