1. Technical Field
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.
2. Description of Related Art
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.
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.
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.
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.
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 '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 '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.
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 “'920 patent”) discloses a humidity controller integrated with a constant volume air-handling unit. The '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.
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.
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 (O2), ozone (O3), 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.
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.
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.
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:
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 (O2), ozone (O3) and odors.
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.
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).
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.
The method of the present invention is illustrated with reference to
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
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.
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.
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
With reference to
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.
The present invention is able to complement the ventilation capabilities of the HVAC system with these non HVAC-specific ventilation systems. Referring to
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
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
This invention also includes an improved HVAC controller 700 as shown in
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.