Abstract:
An HVAC controller and a method of controlling an HVAC system. In one embodiment, the controller includes: (1) a processor couplable to at least one indoor air quality sensor to receive values therefrom representing at least three levels of indoor air quality and (2) memory coupled to the processor and configured to store a software program capable of causing the processor to control an HVAC system based on magnitudes of the values.

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
       [0001]    This application claims the benefit of U.S. Provisional Application Ser. No. 61/180,405, filed by Mark Beste, et al., on May 21, 2009, entitled “Comprehensive HVAC Control System,” commonly assigned with this application and incorporated herein by reference. 
     
    
     TECHNICAL FIELD 
       [0002]    This application is directed, in general, to heating, ventilation and air conditioning (HVAC) systems and, more specifically, to an HVAC system controller having a multifunctional indoor air quality sensor and a method of controlling the HVAC system based on input from the sensor. 
       BACKGROUND 
       [0003]    Some conventional HVAC systems are capable of employing dry contact (discrete on-off switch) indoor air quality sensors to detect when carbon dioxide (CO 2 ) or volatile organic compounds (VOCs) reach a level of concentration regarded as potentially harmful. The design of the sensors themselves reflects that level of concentration. For example, one dry contact CO 2  sensor may be designed to change state when the CO concentration reaches 1000 parts per million (PPM), while another may be designed to change state when the CO 2  concentration reaches 5000 PPM. Conventional HVAC systems have employed dry contact indoor air quality sensors to advantage, and customers and users of such systems have benefitted from the integration of such sensors into such systems. 
       SUMMARY 
       [0004]    One aspect provides an HVAC controller. In one embodiment, the controller includes: (1) a processor couplable to at least one indoor air quality sensor to receive values therefrom representing at least three levels of indoor air quality and (2) memory coupled to the processor and configured to store a software program capable of causing the processor to control an HVAC system based on magnitudes of the values. 
         [0005]    Another aspect provides a method of controlling an HVAC system. In one embodiment, the method includes: (1) receiving values from at least one indoor air quality sensor, the values representing at least three levels of indoor air quality and (2) controlling the HVAC system based on magnitudes of the values. 
         [0006]    Yet another aspect provides an HVAC system. In one embodiment, the system includes: (1) an outdoor unit, including: (1a) at least one compressor stage, (1b) at least one corresponding condenser fan, (1c) at least one corresponding refrigerant pressure sensor, and (1d) at least one condenser coil, (2) an indoor unit, including: (2a) at least one evaporator coil, (2b) at least one indoor blower and (2c) at least one expansion valve, (3) at least one damper and (4) an HVAC controller, including: (4a) a processor couplable to at least one indoor air quality sensor to receive values therefrom representing at least three levels of indoor air quality and (4b) memory coupled to the processor and configured to store a software program capable of causing the processor to control the HVAC system based on magnitudes of the values. 
     
    
     
       BRIEF DESCRIPTION 
         [0007]    Reference is now made to the following descriptions taken in conjunction with the accompanying drawings, in which: 
           [0008]      FIG. 1  is a block diagram of an HVAC system containing one embodiment of a controller having a multifunctional indoor air quality sensor connector constructed according to the principles of the invention; 
           [0009]      FIG. 2  is a block diagram of one embodiment of the controller of  FIG. 1 ; and 
           [0010]      FIG. 3  is a flow diagram of one embodiment of a method of controlling an HVAC system based on input from a multifunctional indoor air quality sensor connector carried out according to the principles of the invention. 
       
    
    
     DETAILED DESCRIPTION 
       [0011]    As stated above, conventional HVAC systems have employed dry contact indoor air quality sensors to advantage, and customers and users of such systems have benefitted from the integration of such sensors into such systems. However, it is realized herein that more effective steps may be taken to detect and react to changes in indoor air quality were quantitative air quality data available. Further, it is also realized herein that indoor air quality may be improved more comprehensively were an array of pollutants broader than CO 2  and VOCs, such as radon, molds and other allergens, legionella and other bacteria, asbestos fibers, carbon monoxide (CO), ozone (O 3 ) and other potentially harmful substances, taken into account. It is also realized herein that various types and degrees of air quality deficiency may be identified and responded to or compensated for in various ways and to various degrees. Accordingly, introduced herein are various controllers and methods for gathering and analyzing quantitative indoor air quality data and controlling an HVAC system based thereon. 
         [0012]      FIG. 1  is a block diagram of an HVAC system  100  containing one embodiment of a controller having a multifunctional indoor air quality sensor connector constructed according to the principles of the invention. The HVAC system  100  includes an outdoor unit  110 , which may be a rooftop unit, and an indoor unit  120 . The outdoor unit  110  and the indoor unit  120  are represented as being separate, but in fact may be housed in a common enclosure. The outdoor unit  110  of  FIG. 1  is air-cooled. However, the outdoor unit  110  is liquid-cooled in an alternative embodiment. 
         [0013]    The illustrated embodiment of the outdoor unit  110  includes one or more compressors each having one or more stages  111 . One or more condenser fans  112  are associated with one or more condenser coils  113  to move air across the one or more condenser coils  113 . An outside air temperature sensor  114  is situated in or on the outdoor unit  110  to detect an ambient outdoor air temperature, and one or more refrigerant pressure sensors  115  are situated in or on the outdoor unit to detect refrigerant pressure in the one or more condenser coils  113 . In the illustrated embodiment, at least one refrigerant pressure sensor, a low ambient pressure switch, is associated with each condenser coil and is configured to change switch state (open or close) as a function of the pressure of refrigerant in its associated coil relative to a pre-established pressure at a lower end of an acceptable pressure range. In another embodiment, a high ambient pressure switch is also associated with each condenser coil and is configured to change switch state as a function of the pressure of refrigerant in its associated coil relative to a pre-established pressure at a higher end of an acceptable pressure range. 
         [0014]    The illustrated embodiment of the indoor unit  120  includes one or more evaporator coils  121 . One or more blowers  122 , sometimes known as indoor blowers, are associated with the one or more evaporator coils  121  to move air across the one or more evaporator coils  121 . One or more expansion valves  123  are coupled to one or more corresponding refrigerant conduits  124 . The one or more refrigerant conduits  124  couple the one or more stages  111  of the one or more compressors, the one or more condenser coils  113 , the one or more expansion valves  123  and the one or more evaporator coils  121  to form a loop within which a refrigerant (e.g., a hydrofluorocarbon fluid or carbon dioxide) is repeatedly compressed, cooled, decompressed and warmed to effect air conditioning. In one embodiment, the indoor unit  120  includes one or more heater coils (not shown) associated with the one or more blowers  122  to effect heating. In another embodiment, the one or more blowers  122  may be activated separately to effect ventilation. 
         [0015]    As stated above, the illustrated embodiment of the system  100  further includes an HVAC controller  130 . The illustrated embodiment of the controller  130  is configured to receive input signals from, perhaps among other things, the outside air temperature sensor  114 , the one or more refrigerant pressure sensors  115  and one or more indoor air quality sensors  140 . Based on one or more of these input signals, the controller  130  is further configured to generate output signals to control, perhaps among other things, the one or more condenser fans  112 , the one or more blowers  122 , one or more dampers  150  and one or more exhaust fans  160  that, in turn, direct air through ducts associated with the one or more blowers  122 . The illustrated embodiment has two or more dampers  150 . One or more of the dampers  150  may be located where duct pressure is less than outside ambient air pressure and opened to admit outside air into the ducts, where it mixes with indoor air. One or more dampers may be located where duct pressure is greater than the outside ambient air pressure and opened to exhaust indoor air to the outside environment. The one or more dampers  150  may have one or more fans associated therewith to allow exhaust and ventilation rates to be changed (increased or decreased). 
         [0016]    A user interface (not shown), perhaps including an indoor temperature sensor, a message screen and an alarm annunciator (such as a bell, a public-address speaker, a telephone message generator, or a computer network gateway), is coupled to the controller  130  and configured to allow a user to select a setpoint indoor temperature and perhaps a system operational mode (i.e., air conditioning, heating or ventilation) and also display information about the HVAC system  100 , including providing alarms and other messages. The controller  130  may provide at least some of these alarms and messages to a building control system  170  and, in some embodiments, receives data from the building control system  170  as well. Those skilled in the pertinent art are familiar with the manner in which HVAC systems, such as the HVAC system  100  of  FIG. 1 , may be controlled by a user. Those skilled in the pertinent art are also familiar with alarm annunciators that are conventionally associated with fire systems, including those that include bells or speakers to alert building occupants and provide instructions when a fire or other condition is detected. 
         [0017]    As stated above, the illustrated embodiment of the system  100  further includes one or more indoor air quality sensors  140  coupled to the controller  130 . The one or more sensors  140  may be of any type or combinations of conventional or later-developed type. The one or more sensors  140  may produce analog or digital values that represent quantitative measurements the one or more sensors  140  make. If analog, the values may be converted to digital form before being provided to the processor  210 . The controller  130  then receives the analog or digital values and employs them as an input to one or more response processes. In the illustrated embodiment, the one or more response processes take the form of one or more software programs employable to evaluate the inputs, including their type and the magnitude of their values, and decide upon a correct action to take in response. The output of the one or more response processes may then be used to control the HVAC system and thereby respond to indoor air quality issues that may arise. 
         [0018]      FIG. 2  is a block diagram of one embodiment of the controller  130  of  FIG. 1 . In the embodiment of  FIG. 2 , the controller  130  takes the form of a general purpose microcontroller and contains a processor  210  configured to execute software (e.g., firmware) instructions, a volatile memory  220  coupled to the processor  210  and configured to store software instructions, data or both software instructions and data and nonvolatile memory  230  coupled to the processor  210  and configured to store software instructions, data or both software instructions and data. In the embodiment of  FIG. 2 , the nonvolatile memory  230  stores the software instructions and persistent data (e.g., factory settings and messages) that enable the operation of the controller  130 , including the response processes, and the volatile memory  220  stores data that the controller  130  collects during its operation and stores temporarily for internal use or external recall (e.g., scratchpad data and operational logs). 
         [0019]    As  FIG. 2  shows, an outside air temperature sensor  114 , a refrigerant pressure sensor  115  and the indoor air quality sensor  140  of  FIG. 1  are coupled to the processor  210  to provide input signals thereto. In the embodiment of  FIG. 1 , the indoor air quality sensor  140  provides analog input signals that an analog-to-digital converter  240  then converts to digital values that the processor  210  can employ. Likewise, the processor  210  is coupled to a compressor stage  111 , a corresponding condenser fan  112  and inlet and exhaust dampers  150 . 
         [0020]    Having set forth several embodiments of an HVAC system and a controller, several examples of response processes will now be set forth. In a first example, the indoor air quality sensor is a CO sensor, and the values that the CO sensor is providing to the controller  130  indicates a relatively minor CO issue in one part of a building. An example response process may therefore just increase the ventilation rate of the HVAC system as a whole (e.g., increase the speed of the one or more blowers  122  and modulate the outdoor air damper to allow more fresh air into the building) to distribute the CO and reduce its local concentration to acceptable levels. 
         [0021]    In a second example, the indoor air quality sensor remains a CO sensor, and the values that the CO sensor is providing to the controller  130  indicates a moderate CO issue in the building. The example response process may therefore open an inlet damper  150  to admit outside air into the building to reduce the CO concentration to acceptable levels. 
         [0022]    In a third example, the indoor air quality sensor is again a CO sensor, and the values that the CO sensor is providing to the controller  130  indicates a major CO issue in the building. The example response process may therefore increase the ventilation rate of the HVAC system, open an exhaust damper  150  and turn on an exhaust fan  160  to exhaust indoor air to the outside and activate the alarm annunciator, perhaps via the building control system  170 , to prompt building occupants to exit the building. 
         [0023]    In a fourth example, the indoor air quality sensor is a mold sensor, and the values that the mold sensor is providing to the controller  130  indicates a moderate mold problem in one part of the building. The example response process may therefore increase the ventilation rate of the HVAC system in that part of the building, cause a warning message to be displayed on user interfaces in that part of the building and cause a further warning message to be transmitted via the building control system  170  to a building management company and/or a mold remediation service. 
         [0024]    In a fifth example, the indoor air quality sensor is a VOC sensor, and the values that the VOC sensor is providing to the controller  130  indicates a major VOC issue in the building, with an attendant fire risk. The example response process may therefore (1) reduce the ventilation rate of the HVAC system to zero to keep the VOCs from spreading, (2) activate alarm codes to cause ventilation in other areas of the building to increase to keep VOC particles concentrated in the particular zone where they were detected and not allow them to spread through doors, windows or return ducts and (3) activate the alarm annunciator perhaps via the building control system  170  to prompt building occupants to exit the building, cause a VOC alarm message to be transmitted to building management and call the local authorities. As one skilled in the art can readily see, the examples given here are but a small subset of possible examples given the many types of indoor air quality sensors that may be employed, the many magnitudes of values that such sensors may provide and the many types of responses that an HVAC system may make to such magnitudes. The invention fully contemplates and encompasses all such sensors, magnitudes and responses. 
         [0025]      FIG. 3  is a flow diagram of one embodiment of a method of controlling an HVAC system based on input from a multifunctional indoor air quality sensor connector carried out according to the principles of the invention. The method begins in a start step  305 . In a step  310 , at least one indoor air quality value is received from at least one indoor air quality sensor. In a step  315 , a response process is executed to determine how to respond based on magnitude of the at least one indoor air quality value. In a decisional step  320 , it is determined whether the response process calls for the ventilation rate of the HVAC system to be changed. If so, a ventilation rate based on the magnitude of the at least one indoor air quality value is selected in a step  325 . 
         [0026]    In a decisional step  330 , it is determined whether the response process instead or also calls for one or more dampers in the HVAC system to be moved and if one or more exhaust fans are to be turned on. If so, damper positions and fans are selected based on the magnitude of the at least one indoor air quality value. In a decisional step  340 , it is determined whether the response process instead or also calls for an alarm to be issued. If so, an alarm is issued based on the magnitude of the at least one indoor air quality value in a step  350 . The method then returns to the step  310 , in which subsequent indoor air quality values are received, and the step  320 , in which subsequent response processes are executed to determine whether responses should be undertaken and, if so, what those responses should be. 
         [0027]    Those skilled in the art to which this application relates will appreciate that other and further additions, deletions, substitutions and modifications may be made to the described embodiments.