Abstract:
The present invention provides an improved method and system for controlling an HVAC system for managing multiple indoor air quality (IAQ) parameters. An acceptable range is defined for each of the IAQ parameter. The parameters are then monitored by sensors within a controlled space. The parameters may comprise temperature, humidity, smoke, radon, VOCs, carbon dioxide, carbon monoxide, particulates, hydrocarbons, oxygen, ozone, and odors. The invention maintains the IAQ parameters within their respective acceptable ranges by automatically manipulating certain HVAC system functions including heating, cooling, humidification, dehumidification, ventilation, addition or removal of materials or compounds which affect IAQ parameters, airflow volume and air recirculation. In one embodiment of the invention, a non-HVAC-specific venting system is used to augment HVAC adjustment of airflow volume and air recirculation. This may include bathroom, kitchen and attic venting systems as well as whole-home vacuum systems.

Description:
BACKGROUND 
       [0001]    1. Technical Field 
         [0002]    The present invention relates generally to a process or method for controlling HVAC systems, and more particularly to controlling HVAC systems according to multiple variables including but not limited to measurements of indoor air quality parameters. 
         [0003]    2. Description of Related Art 
         [0004]    Simple heating ventilation and air conditioning (HVAC) systems respond to or control merely one or two variables at a time. Temperature is the one most often controlled. When the environment is too hot or cold, a system turns on a heater, furnace, heat pump, or air conditioner based on the settings of a thermostat and adjusts the air temperature either upward or downward to match a set point and keep the air in a controlled space within a temperature range. Relatively sophisticated systems can be programmed to different set points or ranges at different times during a typical daily cycle. 
         [0005]    HVAC systems typically control temperature with a single temperature controller or thermostat which has the single control input of dry bulb temperature and a single controlled output which is the run time of the equipment and in some cases, the recirculating air temperature. This equipment can have an effect on other variables such as humidity in the controlled space during operation. When moisture content is high, or when the thermostat does not sufficiently run the equipment because of low dry bulb conditioning requirements, the humidity can be excessively high. Also, during periods of high humidity and relatively warm temperatures in a controlled space, many air-handling units have sufficient capacity to cool the space, but are incapable of keeping the humidity at a sufficiently comfortable level. In such cases, a separate humidity control unit can be added to the system. 
         [0006]      FIG. 1A  shows a typical HVAC system with a rudimentary controller for a residential dwelling  110 . With reference to  FIG. 1A , an HVAC unit  140  pulls internal air into an inlet  106  and blows it through air conditioning openings  108  throughout the controlled space  102 . The HVAC unit  140  usually attempts to control the temperature of the air in the controlled space  102  through the use of a temperature sensor  104  or thermostat and a feedback controller (not shown). Thus, at most, the HVAC unit  140  can heat or cool the air as it recirculates through the controlled space. Relatively small volumes of air may also enter or leave the controlled space  102  through openings  116  to the outside  150  such as windows or doors or other leaky openings. 
         [0007]    Some residential and commercial HVAC units offer a slight improvement over such rudimentary circulation by supplementing recirculated air with an inlet stream of fresh air. In this way, multiple air quality variables may be adjusted by controlling the relative amount of inlet or fresh air flowing into the HVAC system. Certain HVAC systems, including those in automobiles, commonly include an inlet air controller such as a movable valve or shutter (referred to herein simply as an inlet air valve) that is positioned to control what proportion of the inlet air is drawn from inside and outside the controlled space. In a typical application, a system controller positions the air inlet valve to optimize system efficiency and occupant comfort, and an occupant is permitted to override the normal control when indoor air recirculation or outside air ventilation is desired. For example, air recirculation may be used to limit the intrusion of polluted outside air, or outside air may be used to purge the controlled space of smoke or odors. However, occupants frequently fail to manually correct the inlet air valve to accommodate the prevailing conditions in the controlled space. A need exists for a control system that measures IAQ parameters in the controlled space and makes adjustments automatically. 
         [0008]      FIG. 1B  shows a typical residential HVAC unit with just such a limitation. With reference to  FIG. 1B , an HVAC unit  140  pulls inside air into an inlet  106 , combines it with fixed volume of fresh outside air taken from an outside air inlet  112 , and blows it through air conditioning openings  108  throughout the controlled space  102 . In addition, some HVAC systems purge some of the air in the controlled space  102  through an exhaust vent  114 . Through the combination of adding fresh outside air and exhausting some stale air, the HVAC system  140  reduces build up of air quality contaminants. Simultaneously, an HVAC system  140  controls air temperature in the controlled space  102  through the use of a temperature sensor  104  and a feedback controller (not shown). The HVAC unit  140  blows a fixed ratio of recirculated air and fresh or makeup air throughout the controlled space. Such ratio can be adjusted for comfort conditions, efficiency, or seasonal changes and is not normally dynamically controlled in real time to adjust for variations in air quality parameters. Likewise, no dynamic real time adjustment is made for changes in the amount of air that enters or leaves through windows and doors such as when occupants enter or leave the controlled space. 
         [0009]    In addition to the limitation of controlling just one or two variables, all HVAC systems have a maximum volume of air for ventilation through the controlled space. There is no systematic means to supplement this ventilation volume. While other ventilation systems exist in the house, for example bathroom and kitchen ventilators, they are not integrated into a system which controls ventilation levels for the building. 
         [0010]    There have been some attempts at detecting and controlling a single pollutant or environmental constituent depending on certain conditions. For example, U.S. Pat. No. 6,916,239 issued to Siddaramanna et al. on Jul. 12, 2005 (“patent &#39;239”) discloses a method of controlling carbon dioxide levels in a controlled space by changing the volume of air circulated, depending on the number of human occupants in the controlled space. The &#39;239 patent discloses a method to control both carbon dioxide levels and air temperature within a controlled space. Outside air is injected into the controlled space when predicted carbon dioxide levels rise. The carbon dioxide levels are predicted based upon a count of people entering or exiting a controlled space. An alternative method of controlling carbon dioxide levels in a space uses single or multiple carbon dioxide sensors in conjunction with a controller to adjust the amount of outside air injected to keep carbon dioxide levels within a desired range. 
         [0011]    Some newer HVAC systems control the indoor humidity within certain limits in addition to temperature. U.S. Pat. No. 6,826,920 issued to Wacker on Dec. 7, 2004 (the “&#39;920 patent”) discloses a humidity controller integrated with a constant volume air-handling unit. The &#39;920 patent discloses a system having an actuator controlling a mixed air damper and actuator controlling both an outdoor air intake damper and an indoor air exhaust damper. It also teaches the use of humidity and temperature sensors placed outdoors and within the controlled space, wherein humidity may be controlled by slowing down the movement of air across the cooling coil of the air-handling unit. 
         [0012]    Despite the existence of a variety of improved HVAC systems, improved sensors, and improved control systems, there remains a need to control HVAC systems according to multiple variables including those associated with air quality within a controlled space, not just the “comfort” variables of temperature and humidity. A need exists to simultaneously control temperature, humidity, odors, and the level of inside air constituents and pollutants, as well as a programmed set of responses to changes in a variety of environmental variables. Furthermore, it would be desirable to independently control such variables in a plurality of controlled space compartments. The present invention fills these goals and others as detailed more fully below. 
       SUMMARY OF THE INVENTION 
       [0013]    The present invention provides an improved method and system for controlling an HVAC system for managing multiple indoor air quality (IAQ) parameters. An acceptable range is defined for each of the IAQ parameter. The parameters are then continually monitored by sensors within a controlled space. The parameters may include temperature, humidity, and levels of smoke, radon, VOCs including aldehydes, carbon dioxide, carbon monoxide, particulates, oxygen (O 2 ), ozone (O 3 ), and odors. The invention maintains the IAQ parameters within their respective acceptable ranges by automatically manipulating certain HVAC system functions including heating, cooling, humidifying, dehumidifying, the addition or removal of materials or compounds that affect IAQ parameters, airflow volume and air recirculation. 
         [0014]    In one embodiment of the invention, non-HVAC-specific venting systems are used to augment HVAC adjustment of airflow volume and air recirculation. This may include bathroom and kitchen exhaust vents, attic fans as well as whole-home vacuum systems. 
         [0015]    In another embodiment, an improved thermostat is disclosed that includes the additional sensors. This allows for a central point of control. The thermostat may include sensors for particulates, radon, VOCs, carbon dioxide, carbon monoxide, oxygen, ozone, hydrocarbons, smoke and odors. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0016]    The novel features believed characteristic of the invention are set forth in the appended claims. The invention itself, however, as well as a preferred mode of use, further objectives and advantages thereof, will be best understood by reference to the following detailed description of illustrative embodiments when read in conjunction with the accompanying drawings, wherein: 
           [0017]      FIG. 1A  is a schematic view of a controlled indoor space showing air temperature control according to the prior art; 
           [0018]      FIG. 1B  is a schematic view of a controlled indoor space showing air temperature control along with fresh air input and air exhaust according to the prior art; 
           [0019]      FIG. 2  is a schematic view of a controlled indoor space showing elements of an improved method to control indoor air quality according to a first embodiment of the present invention; 
           [0020]      FIG. 3  is a schematic view of a controlled indoor space showing elements of an improved method to control indoor air quality according to a second embodiment of the present invention; 
           [0021]      FIG. 4  is a response matrix or table showing possible actions taken in response to changes in at least one indoor air quality parameter or constituent; 
           [0022]      FIG. 5  shows alternate embodiment of the present invention in which the traditional airflow and venting passages of the HVAC system are supplemented with additional venting systems commonly found in homes; 
           [0023]      FIG. 6  illustrates the optimization relationships between IAQ components and conditions for which the HVAC system must compensate; and 
           [0024]      FIG. 7  illustrates a controller that incorporates thermostat controls and IAQ sensors and controls as well. 
       
    
    
     DETAILED DESCRIPTION 
       [0025]    While the invention is described below with respect to a preferred embodiment, other embodiments are possible. The concepts disclosed herein apply equally to other processes and methods to control indoor air quality (IAQ) parameters. in a controlled space. These IAQ parameters include comfort components such as temperature and humidity and traditional IAQ components such as levels of radon, VOCs including aldehydes, carbon dioxide, carbon monoxide, particulates, oxygen (O 2 ), ozone (O 3 ) and odors. 
         [0026]    The present invention is an improved method for controlling IAQ parameters by controlling airflow throughout an enclosed or controlled space, including individual zones within such space.  FIG. 2  illustrates one embodiment of the elements used in the present invention wherein a dwelling or living space comprises three zones. With reference to  FIG. 2 , air is recirculated through a controlled space divided into compartments, rooms, or zones. As in most dwellings, there is some commingling of air between a first zone  202 , a second zone  204 , and a third zone  206  as shown by the arrows. Air flows counter-clockwise from an HVAC unit  240  through air passageways into each zone  202 ,  204 ,  206  and returns to the HVAC unit  240  through return vents  242 ,  244 ,  246  from each room. Baffles  222 ,  224 ,  226  control the flow of air into each of the respective zones  202 ,  204 ,  206 . Sensors  212 ,  214 ,  216  in each of the zones  202 ,  204 ,  206  provide feedback signals to the controller in the HVAC unit  240  or alternatively to a controller  250  located within the space. The controller, which is located in the space, would also communicate with the HVAC unit  240 . Communication can be through wires or alternatively through wireless means. 
         [0027]    An outside sensor  218  allows the HVAC system to determine the quality of the outside air  150 . Fresh or outside air  150  enters the controlled space through a separate intake vent. An intake baffle  230  in conjunction with an exhaust baffle  228 , control the relative amount of fresh air versus recirculated air in the system. Internal to the HVAC unit  240 , one or more elements (not shown) provide a continuous range of overall airflow to the controlled space. Such range may extend from no airflow (off position) to a maximum of several volumes of controlled air space per unit time (e.g. ten volumes per hour). 
         [0028]    Each sensor  212 ,  214 ,  216  may be a single sensor, a composite sensor or may represent multiple sensors that provide a feedback signal on a variety of air components and air conditions. Additionally, each sensor may be in the return duct leading back to the HVAC unit  240  from each of the zones  202 ,  204 ,  206 . Such signals are used to control system components or variables to affect IAQ parameters. 
         [0029]    The method of the present invention is illustrated with reference to  FIG. 2  according to various scenarios. In a first scenario, when an IAQ parameter (e.g. VOC) enters a first zone  202 , a first zone sensor  212  alerts the HVAC system  240 , which responds by taking a variety of programmed actions. The HVAC system  240  increases the overall airflow within the controlled space and, if possible, also changes the relative amounts of airflow through the various zones  202 ,  204 ,  206 . 
         [0030]    The HVAC system  240  accomplishes this change by partially or fully closing a second airflow baffle  224  and a third airflow baffle  226  leading to the second zone  204  and third zone  206 , respectively. The HVAC system  240  also increases the opening of a first airflow baffle  222  leading to the first zone  202 . Finally, the HVAC system maximizes the use of fresh or outside air  150  into the controlled space. In this way, the pollutant is flushed as quickly as possible from the controlled space and the first zone  202 . This example assumes that the outside or fresh air is lower in concentration of the pollutant. With reference to  FIG. 2 , the HVAC system can make adjustments based upon a reading from an outdoor sensor  218  regarding the amount of pollutant in the outside air  150 . 
         [0031]    In a second example, if the outside concentration of an IAQ parameter is above an unacceptable level, and if a first zone sensor  212  detects an increase of this IAQ parameter, the HVAC system  240  responds differently. In this second scenario, the HVAC system  240  maximizes recirculation of air within the controlled space to minimize the chance of the outside IAQ parameter from entering the system. The HVAC system  240  does this by closing an exhaust baffle  228  and closing an input air baffle  230 . It may also optionally slow the overall flow of air throughout the controlled space and if appropriate, turn on a device within the system which removes the IAQ parameter of concern. If the second and third sensors  214 ,  216  in the second and third zones  204 ,  206 , respectively, detect lower amounts of this IAQ parameter, the HVAC system  240  circulates more air through the first zone  202  relative to the second zone  204  and third zone  206  to flush out the IAQ parameter from the first zone  202 . As before, this is accomplished by changing the relative positions of the airflow baffles  222 ,  224 ,  226 . Once the indoor sensors  212 ,  214 ,  216  indicate that the level of IAQ parameter has declined to below an acceptable limit, the HVAC system returns to normal operation. 
         [0032]    In a third scenario, if the second sensor  214  detects a high level of carbon dioxide, the HVAC system  240  increases the overall airflow to the entire controlled space and increases the relative amount of fresh air injected into the controlled space. If the second sensor  214  detects a high level of VOCs, the HVAC system  240  turns on a device within the system to reduce the VOCs by absorption, adsorption, conversion or other means. The HVAC system  240  also responds by increasing the circulation of fresh air into the controlled space as previously described, and increasing the flow of air into the second zone  204  if possible. 
         [0033]    In a fourth scenario, if the third sensor  216  detects a relatively high level of particulates, the HVAC system  240  turns on an internal filtration system (not shown) to filter out the air-borne particulates. Such internal filtration system may be within the air ducts returning to the HVAC system  240 , or may be a separate airflow system in fluid communication with one or more zones of the controlled space. In addition, the HVAC system  240  may increase the airflow to the third zone  206  where the high level of particulates is found or to the entire controlled space so as to keep particulates airborne and exposed to the filtration system. In each scenario the sensors can communicate with a centrally located controller  250 , like the thermostat shown in  FIG. 7 . The connection can be by wireless or wired network. 
         [0034]      FIG. 3  is a second embodiment of the elements used in the present invention wherein similar three zones are found within a dwelling. In this configuration, air is circulated through a controlled space divided into three zones  302 ,  304 ,  306 . In this dwelling  110 , as mentioned in regard to  FIG. 2 , there is some commingling of air between a first zone  302 , a second zone  304 , and a third zone  306  as shown by the arrows. Unlike the embodiment in  FIG. 2 , air flows counter-clockwise from an HVAC unit  340  through individual air passageways into each zone  302 ,  304 ,  306 . Air circulated in this manner returns in separate air return lines to the HVAC unit  340  through individual return vents  342 ,  344 ,  346  in each room. Baffles  222 ,  224 ,  226  may be used to control the flow of air into each of the respective zones  302 ,  304 ,  306 . However, as shown in  FIG. 3 , through the use of separate air lines, these airflow baffles  222 ,  224 ,  226  are not required and airflow into each zone  302 ,  304 ,  306  may be controlled directly within the HVAC system  340 . 
         [0035]    With reference to  FIG. 3 , sensors  212 ,  214 ,  216  in each of the zones  302 ,  304 ,  306  provide an electronic feedback signal to the controller in the HVAC unit  340 . When one of the sensors detects the presence of a contaminant, the HVAC system  340  responds. For example, when the second sensor  214  detects an abnormally high level of VOCs, the HVAC system  340  responds by changing the airflow in the second zone  304  and possibly turning on a device within the system, which removes VOCs. Specifically, the HVAC system  340  increases the quantity of airflow entering and exiting the second zone  304 . The HVAC system  340  may also increase the airflow or air pressure in the first zone  302  and the third zone  306  so that the overall net flow of air is into the second zone  304  and out through the second return duct  344  to the HVAC system  340 . With individual air passages into each zone, the HVAC system  340  may blow recirculated air into the first zone  302  and the third zone  306 , and may blow fresh outside air  150  into the second zone  304 . The HVAC system  340  may blow heated air into the first zone  302  and third zone  306  and may blow cool air into the second zone  304  so as to further limit the diffusion of contaminant out of the second zone  304 . Alternatively, if a high level of carbon monoxide is detected within the controlled space the HVAC system  340  may slow or stop air recirculation, increase ventilation and/or set off an alarm to alert the occupants of the controlled space of the presence of unacceptable levels of carbon monoxide. 
         [0036]    The HVAC system  340  takes corrective action until a detectable contaminant has reached an acceptable level. The HVAC system  340  may take other simultaneous corrective actions to maintain the other controlled variables within desired ranges. For other disturbances, the HVAC system  340  makes specific, individually tailored corrective actions depending on the identity of the contaminant or type of disturbance. 
         [0037]      FIG. 4  illustrates the various actions  400  taken by an HVAC system according to detected changes in dependent variables according to one embodiment of the invention and any number of scenarios such as those previously presented.  FIG. 4  is by way of illustration and should not be construed as a limitation on the functions of the present invention. An HVAC controller  402  measures IAQ parameters  404 . These measurements are conveyed to the HVAC system  406 . For comfort components, the system may perform as a traditional HVAC system  408 . However, for the measured IAQ components  410 , the system will perform in other ways to mitigate and control the IAQ parameters. For high CO 2  or radon measurements  412 , the HVAC system will open ventilation dampers  414  and allow more fresh air into the controlled space. The system may also activate a whole house vacuum system, which is typically driven by a blower located in the home&#39;s garage or basement. Alternatively, or in supplement thereof, the system can activate the kitchen, bath or laundry exhaust systems. The controller  402  will activate the vacuum, which will then vent the CO 2  or radon from the controlled spaces having access ports to the whole home vacuum system. Covers over the ports may be opened to create access between the controlled space and the vacuum system. For this system to be more effective, the vacuum system could be vented to the outdoors. In the event that the measured IAQ parameters indicate high particulates  420 , then the fan may be run continuously through filtration media  422  until the particulate count reaches an acceptable level. Alternatively, the system may simply shut-down if the level of particulates indicates a fire. In the case of high volatile organic compounds (VOCs)  430 , the system may again ventilate the controlled space to the outside. It may also activate an air cleaner  432  such as a PCO (photocatalytic oxidation) device that uses ultraviolet light to break down the VOCs. 
         [0038]      FIG. 5  shows another embodiment of the present invention in which traditional airflow and venting passages of the HVAC system are supplemented with additional venting systems commonly found in homes. In addition to HVAC air ducts, most homes include several additional air venting systems associated with specific functions. The two most common are kitchen exhaust systems and bathroom ventilation systems. In addition, in some geographical areas, fans are sometimes installed in homes to exhaust indoor air to the attic for whole house cooling at night. Less common is a whole house vacuum system, which provides a centralized vacuum that may be accessed from multiple vent outlets throughout the house. 
         [0039]    The present invention is able to complement the ventilation capabilities of the HVAC system with these non HVAC-specific ventilation systems. Referring to  FIG. 5 , the first zone  502  in the controlled space may be the kitchen, which includes a vent  510 . The third zone  506  might be a bathroom with an exhaust vent  512 . If the home in question has a whole house vacuum system, it is likely to have airflow outlets  514 ,  516 ,  518  in each room (zone) leading to a common outflow vent  520 . 
         [0040]    The HVAC system  540  is able to control these additional ventilation systems in order to supplement and fine tune the functions of the HVAC baffles and airflow vents. For example, if toast is burned in the kitchen, it may be most desirable to turn on the kitchen exhaust fan in conjunction with supplying additional air to the zone including the kitchen using the HVAC system  540 . If a fire occurs however, and there is an acute increase in smoke, VOCs or carbon monoxide that the HVAC ventilation airflow paths alone cannot compensate for within an acceptable time frame, the system  540  may simply be programmed to shut down. A shut down could also be initiated by a signal from a fire detector or a security system. Similar to the system shown in  FIG. 2 , the non-HVAC venting systems can be controlled by a centrally located controller  550 . The connection between the controller and the venting system can be wired or wireless. 
         [0041]      FIG. 6  illustrates the optimization relationships between IAQ components and comfort components for which the HVAC system must compensate. When dealing with multiple parameters, some of which require different compensatory actions on the part of the HVAC system, there must be a constant balancing of one parameter against another.  FIG. 6  shows a simplified graph that covers four parameters: carbon dioxide, VOCs, temperature, and humidity. Additional parameters may also be included, but for simplicity of illustration, the present example is limited to four. 
         [0042]    An optimal range is established for each parameter. The control algorithm for the HVAC system attempts to keep all parameters within their respective optimal ranges. If any of the parameters, such as VOCs  604  and temperature  606 , begin to move out of this range, the HVAC system will compensate to bring it back to optimal. In the example depicted in  FIG. 6 , both carbon dioxide  602  and humidity  608  are beyond their designated maximum, which would trigger the HVAC system to adjust them. The HVAC system continually balances the parameters against each other in order to keep them within this range, and may rely on supplemental venting provided by non-HVAC airflow paths as described above. In certain circumstances, it might be difficult to keep all parameters within guidelines at all times. To address such conflicts, a hierarchy of control can be establish based on the relative importance of each parameter. For example, one response to high CO2 levels is to increase ventilation. Yet, in the summer, this might also result in high humidity. 
         [0043]    This invention also includes an improved HVAC controller  700  as shown in  FIG. 7 . The controller may look like a normal thermostat having a case  702  and a display  704 . A series of sensors  706  may be located in the case  702 . Alternatively, the sensors can be located throughout the controlled spaces as shown in  FIGS. 2 and 5 . The sensors could be modular so that a select set of sensors may be used. For example, this HVAC controller might have temperature and relative humidity sensors, CO 2  and radon sensors, a particulate sensor and a VOC sensor. For a simpler controller, maybe only a CO 2  sensor is included. The display includes readings for temperature  708 , and relative humidity  710 . For these values, users are well accustomed to seeing and understanding numerical values. However, for a factor such as CO 2 , a user may be better served with a bar graph showing acceptable ranges and a current reading located on that bar  712 . The same is true for a contaminant such as radon. For other IAQ parameters, such as particulates and VOCs, it may be better to have a set of potential ranges such as low, medium and high  714 . The present HVAC controller is flexible and may provide for each of these forms of readout. 
         [0044]    The foregoing discussion of the invention has been presented for purposes of illustration and description. Further, the description is not intended to limit the invention to the forms disclosed herein. Consequently, variation and modification commensurate with the above teachings, within the skill and knowledge of the relevant art, are within the scope of the present invention. The embodiment described herein and above is further intended to explain the best mode presently known of practicing the invention and to enable others skilled in the art to use the invention as such, or in other embodiments, and with the various modifications required by their particular application or uses of the invention. It is intended that the appended claims be construed to include alternate embodiments to the extent permitted.