Abstract:
A heating, ventilation, and air conditioning (HVAC) system is described that includes a first unit and a second unit. The first unit comprises a controller configured to output a coded compressor activation signal that is based at least partially on a compressor run signal received from a thermostat. The second unit comprises at least a compressor relay. The second unit is configured to receive and decode the coded compressor activation signal from the first unit and is operable to operate the compressor relay based on the decoded content of the coded compressor activation signal.

Description:
BACKGROUND OF THE INVENTION  
       [0001]     This invention relates generally to operation of heating, ventilation, and air conditioning (HVAC) systems, and more specifically, to operation of compressors, fan coils, and the like using electronically commutated motors (ECMs).  
         [0002]     Energy efficiency minimum requirements continue to be tightened for HVAC equipment and systems. Therefore it has become more important that outdoor condenser/compressor units and indoor evaporator/air handler units are properly matched to one another so that it is possible to achieve the desired energy efficiency ratings.  
         [0003]     Heretofore it has been a common practice, when servicing HVAC equipment, to retain the working unit of the indoor/outdoor pair and replace the non-working unit. In certain scenarios this practice may result in a less than optimal performance of the system, while in other cases, replacement of the non-working unit may be acceptable.  
       BRIEF DESCRIPTION OF THE INVENTION  
       [0004]     In one aspect, a heating, ventilation, and air conditioning (HVAC) system is provided that includes a first unit and a second unit. The first unit comprises a controller configured to output a coded compressor activation signal that is based at least partially on a compressor run signal received from a thermostat. The second unit comprises at least a compressor relay and is configured to receive and decode the coded compressor activation signal from the first unit. The second unit is operable to operate the compressor relay based on the decoded content of the coded compressor activation signal.  
         [0005]     In another aspect, a method for controlling operation of a compressor within a heating, ventilation, and air conditioning (HVAC) system is described. The method includes providing a compressor run signal to a first unit, utilizing the compressor run signal within the first unit to generate a coded compressor activation signal, outputting the coded compressor activation signal to a second unit that includes a compressor, and decoding the coded compressor activation signal within the second unit to determine whether the compressor is to be activated.  
         [0006]     In still another aspect, a blower unit for a heating, ventilation, and air conditioning (HVAC) system is provided. The blower unit is configured to receive a compressor run signal from a thermostat and comprises at least one apparatus configured to generate a signal for combination with the compressor run signal. The blower unit is further configured to output a combination of the compressor run signal and generated signal as a coded compressor activation signal.  
         [0007]     In yet another aspect, a unit for controlling operation of a compressor is provided. The unit comprises a compressor run relay and a decoder. The decoder comprises a relay coil driver operable to change a state of the compressor run relay. The decoder is configured to receive and decode a coded compressor activation signal from an external source and operable to activate the relay coil driver based on the decoded content of the coded compressor activation signal. 
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0008]      FIG. 1  is a block diagram of a thermostatically controlled heating, ventilation, and air conditioning (HVAC) system.  
         [0009]      FIG. 2  is a block diagram of an indoor unit of HVAC system that incorporates a high frequency generator.  
         [0010]      FIG. 3  is a block diagram of an indoor unit of HVAC system that incorporates a high frequency generator within an electronically commutated motor of the blower.  
         [0011]      FIG. 4  is a block diagram of an outdoor unit of an HVAC system configured to operate with one of the indoor units of  FIGS. 2 and 3 .  
         [0012]      FIG. 5  is a block diagram of an alternative embodiment of indoor unit for an HVAC system.  
         [0013]      FIG. 6  is a block diagram of an outdoor unit of an HVAC system configured to operate with the indoor unit of  FIG. 5 . 
     
    
     DETAILED DESCRIPTION OF THE INVENTION  
       [0014]     In one embodiment, the methods and systems herein described prevent operation of a HVAC system where only an outdoor unit of an indoor/outdoor unit pair has been replaced. However, these same methods and systems allow operation of such HVAC systems when only the indoor unit has been replaced. Such methods and systems results in HVAC system configurations such that ever increasing efficiency enhancing measures within indoor units can be utilized though the outdoor unit may be of a different configuration.  
         [0015]     Generally, and referring to  FIG. 1 , in HVAC systems  10 , an indoor evaporator/air handler unit  12  contains a circuit board based controller  14  that receives a  24  volt control signal  16  from a thermostat  18 . In these embodiments, circuit board controller  14  is configured such that a subset  20  of the thermostat signals are routed through to an outdoor condenser/compressor unit  22  to control the operation of a compressor, fan, and other components of outdoor unit  22 . One such thermostat signal ‘Y’ is typically utilized to turn on the compressor by energizing a compressor relay  26  located within outdoor unit  22 . In an alternative embodiment (not shown), a relay coil driver, operating based on a signal other than ‘Y’, may utilized to energize compressor relay  26 .  
         [0016]      FIG. 2  is a block diagram of an indoor unit  50  according to one embodiment of the present invention that is communicatively coupled to thermostat  52 . Indoor unit  50  includes a controller board  51  for routing signals to and from thermostat  52  as described above. In the embodiment illustrated in  FIG. 2 , when a thermostat signal  54  is present that is utilized for turning on one or more of a compressor and fan within an outdoor unit, a high frequency generator circuit  56  in the indoor air handler adds a high frequency signal onto the 24 volt AC compressor run signal  58  going to the outdoor unit. Such combined signals are sometimes referred to herein as a coded compressor activation signal. High frequency generator circuit  56 , in one embodiment, is additionally configured to eliminate any higher harmonics of the high frequency signal that could cause radio frequency interference by filtering and/or low duty factor operation.  
         [0017]     In another embodiment, high frequency generator circuit  56  is configured to provide the coded compressor activation signal which can be received by an outdoor decoder board (described below). The frequency of the signal output by high frequency generator circuit  56  is chosen to be high enough, 100 KHz for example, such that the reactance found in a typical compressor relay coil will not significantly attenuate the signal, and can be easily separated from the 24 volt, 60 Hz, compressor run signal utilizing an inexpensive filter. As further described below, an absence of the high frequency signal at signal Y 1 , which is output to an outdoor unit, will not allow activation of the compressor associated with specific embodiments of outdoor compressor units, as further described below.  
         [0018]      FIG. 3  is a block diagram of an alternative embodiment for an indoor unit  100 . In this embodiment, a high frequency generator (not shown, but similar to high frequency generator circuit  56 ) is integrated into a motor control  102  of an ECM  104  that is powering a blower  106 . The embodiment of  FIG. 3  provides an additional operational feature to that described with respect to indoor unit  50  (shown in  FIG. 2 ) in that ECM  104  becomes a key enabling element. Since the high frequency signal is generated within ECM  104 , a possibility of tampering within indoor unit  100  to bypass the interlock provided through utilization of the high frequency compressor activation signal may be significantly reduced. Operationally however, indoor unit  100  provides the same capabilities as does indoor unit  50  (shown in  FIG. 2 ), that is, an absence of the high frequency signal at signal Y, which is output to an outdoor unit, will not allow activation of the compressor associated with specific embodiments of outdoor compressor units, as further described below.  
         [0019]     Indoor units  50  and  100 , however, are operable with existing outdoor units, for example, those that operate compressors therein based upon receiving a 24 VAC signal from a thermostat. Though indoor units  50  and  100  impose a high frequency signal upon the 24 VAC thermostat signal, existing outdoor compressor units are capable of recognizing the 24 VAC portion of the coded compressor activation signal and controlling operation of their compressors based on whether or not the 24 VAC signal is present.  
         [0020]      FIG. 4  is a block diagram of an outdoor unit  150  according to one embodiment of the present invention. In the embodiment, outdoor unit  150  includes a decoder circuit  152  for receiving coded compressor activation signals. Decoder circuit  152  includes a high pass filter  154 , a detector  156 , and a relay coil driver  158  that outputs a signal for operating compressor relay  160 .  
         [0021]     Outdoor unit  150  utilizes the high frequency coded compressor activation signals generated by either of indoor units  50  (shown in  FIG. 2 ) and  100  (shown in  FIG. 3 ) to determine whether to activate a compressor (not shown) by applying a signal to compressor run relay  160 . More specifically, through incorporation of high pass filter  154  and detector  156 , unless a high frequency signal is input into outdoor unit  150  at signal Y, relay coil driver  158  will not be enabled and the compressor will not run. The signal at Y must be of a frequency high enough to pass through high pass filter  154  and of sufficient amplitude to cause detector  156  to output a compressor activation signal.  
         [0022]     Now referring to  FIG. 5 , an alternative embodiment for generating a coded compressor activation signal is illustrated. Specifically, referring to the block diagram of indoor unit  200 , a control board  202  and a blower motor  204  are included. In a specific embodiment, blower motor  204  is an electronically commutated motor. In the illustrated embodiment, a compressor run signal  206  is combined with an identifying signal  208  from indoor blower motor  204  using a resistor  210 . This results in a coded compressor activation signal  212  that is sent to an outdoor unit over the compressor run signal wire. In an embodiment, the indoor blower motor terminal changes its impedance in step with a changing state of identifying signal  208  so that the composite compressor activation signal  212  will be near ground potential when the output terminal of the blower motor is in a low impedance state, and at an approximately 24 VAC potential when it is in a high impedance state.  
         [0023]     Since composite compressor activation signal  212 , also labeled as Y′ in  FIG. 5 , cannot supply enough current to drive the compressor relay of an outdoor unit, due to the presence of resistor  210 , a source of 24 VAC is needed in any outdoor unit that is utilized with indoor unit  200 . In one embodiment, the ECM operating as the blower motor is configured with an open collector output channel, which is utilized to provide identifying signal  208 . In various embodiments, identifying signal  208  can consist of a frequency code or a pulse code that is received by the decoder board in the outdoor unit. This output channel is configured in a specific embodiment so that indoor unit can provide identifying signal  208  only during a positive portion of the AC signal from control board  202 , as the ECM incorporates a diode that clamps the negative portion of the AC signal.  
         [0024]      FIG. 6  is a block diagram for an outdoor unit  250  that is operable with the indoor unit  200  of  FIG. 5 . Specifically, outdoor unit  250  includes a decoder board  252  that includes a transient filter  254  receiving composite signal  212  from indoor unit  200 . Decoder board  252  also includes a processing unit (microcontroller  256 ) that receives signals through transient filter  254  and controls operation of relay coil driver  258 . Relay coil driver  258 , in conjunction with a DC bias power supply  260  and a 24 VAC supply  262 , control operation of compressor run relay  264 , thereby controlling operation of a compressor (not shown).  
         [0025]     In one embodiment, the components of decoder board  252  evaluate the signal on Y′ for the presence of a combined compressor run signal and identifying signal from the ECM motor  204  (shown in  FIG. 5 ). In this embodiment, decoder board  252 , through filter  254  and processor  256 , are able to discriminate between a positive voltage containing both the blower identifying signal and a half wave DC signal (the compressor run signal) or no signal. If the compressor run signal is present with or without the blower identifying signal, compressor relay  264  will be energized. If a preset time elapses without processor  256  detecting the identifying signal, compressor relay  264  will be deenergized and locked out for a predetermined time. Otherwise the compressor (and condenser fan) will be allowed to run.  
         [0026]     As described above, if a standard outdoor unit (i.e., not one of the above described embodiments) is to be connected to one of the above described indoor units, the compressor activation signal has to be connected to the same terminal as the compressor signal thermostat, so that the outdoor unit is provided with a typical 24 VAC run signal for activating the compressor, though the 24 VAC signal may be combined with a high frequency signal or other frequency coded or pulse coded signal.  
         [0027]     If an outdoor unit is utilized that is configured to be paired with one of the above described indoor unit, it will contain a decoder circuit (see outdoor unit  250  shown in  FIG. 6 ) or filter circuit (see outdoor unit  150  shown in  FIG. 4 ). The output of the decoder or filter is connected to the input of a relay driver circuit, which in turn switches the  24  volt AC to the compressor relay coil ( 158  or  258 ). Such a configuration makes an outdoor unit unresponsive to a typical 24 VAC, 60 Hz, control signal, but responsive to the frequency or coded signal received from one of the above described indoor units.  
         [0028]     If one of the above described outdoor units  150  or  250  is connected to an indoor unit that does not have the identifying, or high frequency, signal, the compressor will be prevented from operating since a typical 24 VAC, 60 Hz, compressor run signal will not satisfy the conditions needed to pass the compressor activation signal through decoder board  252  or the combination of filter  154  and detector  156 .  
         [0029]     As described above, the methods and systems prevents the operation of an outdoor condenser/compressor unit with an indoor fan coil unit that is not configured to operate with the indoor fan coil unit, while allowing the operation of other outdoor unit/indoor unit combination. Such configurations allow an HVAC system that may include one or more replacement components to comply with increasingly rigid energy efficiency ratings while providing the performance desired by users of such HVAC systems.  
         [0030]     Additionally, two stage compressor systems within outdoor units are becoming popular because of the higher efficiency attainable when they run at a lower capacity stage. The methods and systems described herein are easily extensible to such two stage compressor systems, for example, utilizing two different high frequency signals for selection of the two compressor stages in combination with one or more of a separate relay and driver signal for each stage and a single relay utilized in conjunction with a switching circuit to provide either of a first stage connection and a second stage connection to the compressor.  
         [0031]     While the invention has been described in terms of various specific embodiments, those skilled in the art will recognize that the invention can be practiced with modification within the spirit and scope of the claims.