System and method for controlling a fan unit

A system and method for controlling a fan unit are described and shown. The system may comprise an electronic controller, an indoor sensor responsive to at least one characteristic of interior air, and an outdoor sensor responsive to at least one characteristic of exterior air. The electronic controller may cause at least one fan of a window fan to be activated when interior air meets certain criteria relative to a set point and exterior air meets certain criteria relative to interior air. The method may comprise the steps of measuring at least one characteristic of exterior air, at least one characteristic of interior air, and activating an intake fan when the interior air meets certain criteria relative to a set point and the exterior air meets certain criteria relative to the interior air. The fan unit may optionally include a selectively activated compressor and selectively provide air conditioning.

CROSS REFERENCES TO RELATED APPLICATIONS

This Application is a national stage filing under 35 U.S.C. §371 of International Application No. PCT/US2010/045357, filed Aug. 12, 2010, which claimed the benefit of currently pending U.S. patent application Ser. No. 12/540,080, filed on Aug. 12, 2009 and also claimed the benefit of currently pending U.S. patent application Ser. No. 12/540,067, filed on Aug. 12, 2009, the disclosures of which are hereby incorporated by reference.

REFERENCE TO SEQUENTIAL LISTING, ETC.

BACKGROUND

1. Field of the Invention

This invention relates to a control system for a fan unit and a method of controlling a fan unit.

2. Description of the Related Art

Prior art window fans are utilized to move stagnant air and cool internal building areas or rooms when air conditioning is not available. There are various known problems however, with prior art fan structures. First, as depicted inFIG. 15, prior art fans in many cases only pull air into a room and fail to exhaust air which causes poor circulation within the room and therefore hinders cooling. Alternatively, other fan systems pull air into a room and exhaust air in the same vertical plane or elevation. Therefore these fan systems fail to eliminate temperature stratification and reduce cooling effectiveness.

Another problem related to prior art fans is that fan units do no inhibit water passing through a housing and into a room when the fan is operated while a rain event is occurring. Consequently, during rain events, many window fans may not be operated without drawing water into the building.

Another problem with prior art window units is the limited control of fan operation and failure to be intelligently integrated with AC functionality. Most prior art units are manually operated, meaning a user must turn the fan on and off as desired. It would be desirable to use a window fan when specific outside air criteria are met, so that the air conditioning system in the building or home is not needed when the outside air is cool to and of a saturation or humidity level which would be comfortable to an occupant of the building or room.

Additionally, the use of the dew point and humidity controls would allow for increased comfort and energy savings by limiting the use of air conditioning in the building or home. Such limited use of natural resources is desirable.

It would be desirable to create a window fan unit which overcomes these and other deficiencies in order to decrease energy consumption, more efficiently cool interior areas of a building, commercial, residential or other, and improve occupant comfort while ultimately saving money on cooling by using outside air where applicable.

SUMMARY

Generally, in one aspect a control system for a fan unit is provided. The fan unit has a fan for selectively drawing air from an exterior area having exterior air into an interior area having interior air. The control system includes an electronic controller in electrical communication with the fan and a control panel having a user selectable set point input. The set point input is in electrical communication with the electronic controller and provides a user selected set point to the electronic controller. The control system also includes an indoor sensor and an outdoor sensor each in electrical communication with the electronic controller. The indoor sensor is located so as to be responsive to at least one characteristic of the interior air and communicates the at least one characteristic of the interior air to the electronic controller. The outdoor sensor is located so as to be responsive to at least one characteristic of the exterior air and communicates the at least one characteristic of the exterior air to the electronic controller. The fan unit is operable in an automatic mode and in the automatic mode the electronic controller causes the fan to be activated and exterior air to be communicated between the exterior area and the interior area when: the at least one characteristic of the interior air indicates a dry bulb temperature of the interior air is greater than the set point, the at least one characteristic of the exterior air indicates a dry bulb temperature of the exterior air is less than the dry bulb temperature of the interior air, and the at least one characteristic of the exterior air indicates a dew point of the exterior air is less than a dew point of the interior air as indicated by the at least one characteristic of the interior air.

In some embodiments the control system includes a second fan that is an exhaust fan that selectively expels the interior air into the exterior area. In versions of these embodiments the fan may be driven at a plurality of speeds. In versions of these embodiments the speed of the fan may correspond to a differential between the set point and the indoor dry bulb temperature and/or the speed of the second fan may correspond to a differential between the set point and the indoor dry bulb temperature. In versions of these embodiments the second fan is disposed vertically above the fan when the fan unit is installed.

In some embodiments the control system further includes a selectively activated compressor in communication with the electronic controller. The compressor helps selectively cool interior air circulated by the fan unit back into the interior area. In those embodiments the electronic controller causes the compressor to be inactive when: the at least one characteristic of the interior air indicates a dry bulb temperature of the interior air is above the set point, the at least one characteristic of the exterior air indicates a dry bulb temperature of the exterior air is less than the dry bulb temperature of the interior air, and the at least one characteristic of the exterior air indicates a dew point of the exterior air is less than a dew point of the interior air as indicated by the at least one characteristic of the interior air. In versions of these embodiments the electronic controller causes the compressor to be active when: the at least one characteristic of the interior air indicates a dry bulb temperature of the interior air is above the set point, and at least one of the following two conditions is met: (1) the at least one characteristic of the exterior air indicates a dry bulb temperature of the exterior air is greater than the dry bulb temperature of the interior air; and (2) the at least one characteristic of the exterior air indicates a dew point of the exterior air is greater than a dew point of the interior air as indicated by the at least one characteristic of the interior air. In versions of these embodiments the electronic controller closes at least one barrier when the compressor is activated, thereby substantially isolating the fan from the exterior air. When the barrier is closed and the compressor is activated the fan circulates the interior air over an evaporator coil and back into the interior area. In versions of these embodiments the control system further includes a second fan. When the at least one barrier is closed and the compressor is activated the second fan selectively circulates the exterior air over a condensing coil and into the exterior area. In versions of to these embodiments the second fan selectively expels the interior air into the exterior area when: the at least one characteristic of the interior air indicates a dry bulb temperature of the interior air is greater than the set point, the at least one characteristic of the exterior air indicates a dry bulb temperature of the exterior air is less than the dry bulb temperature of the interior air, and the at least one characteristic of the exterior air indicates a dew point of the exterior air is less than a dew point of the interior air as indicated by the at least one characteristic of the interior air. In versions of these embodiments the electronic controller causes the compressor to be active when: the at least one characteristic of the interior air indicates a dry bulb temperature of the interior air is above an AC set point, the AC set point being greater than the set point, and at least one of the following two conditions is met: (1) the at least one characteristic of the exterior air indicates a dry bulb temperature of the exterior air is greater than the dry bulb temperature of the interior air; and (2) the at least one characteristic of the exterior air indicates a dew point of the exterior air is greater than a dew point of the interior air as indicated by the at least one characteristic of the interior air.

Generally, in another aspect a method of controlling a fan unit is provided. The fan unit has an intake fan that selectively draws exterior air through the fan unit into a building interior and at least one barrier that selectively inhibits airflow through the fan unit. The method includes the steps of: allowing a user to select a set point indicative of a minimum desired temperature of interior air; measuring at least one characteristic of the exterior air; measuring at least one characteristic of the interior air; activating the intake fan and opening the at least one barrier to allow exterior air through the fan unit and into the interior area when: the at least one characteristic of the interior air indicates a dry bulb temperature of the interior air is above the set point, the at least one characteristic of the exterior air indicates a dry bulb temperature of the exterior air is less than the dry bulb temperature of the interior air, and the at least one characteristic of the exterior air indicates a dew point of the exterior air is less than a dew point of the interior air as indicated by the at least one characteristic of the interior air.

In some embodiments the fan unit includes an exhaust fan that selectively expels interior air through the fan unit into an exterior and the method further includes the step of activating the exhaust fan when: the at least one characteristic of the interior air indicates a dry bulb temperature of the interior air is above the set point, the at least one characteristic of the exterior air indicates a dry bulb temperature of the exterior air is less to than the dry bulb temperature of the interior air, and the at least one characteristic of the exterior air indicates a dew point of the exterior air is less than a dew point of the interior air as indicated by the at least one characteristic of the interior air. In versions of these embodiments the intake fan and the exhaust fan are each drivable at a plurality of speeds. In versions of these embodiments the method further includes the step of deactivating the intake fan, deactivating the exhaust fan, and closing the at least one barrier when the at least one characteristic of the interior air indicate a dry bulb temperature of the interior air is less than the set point.

In some embodiments the fan unit has air conditioning functionality and includes a selectively activated compressor. In versions of these embodiments the method further includes the step of causing the compressor to be inactive when: the at least one characteristic of the interior air indicates a dry bulb temperature of the interior air is above the set point, the at least one characteristic of the exterior air indicates a dry bulb temperature of the exterior air is less than the dry bulb temperature of the interior air, and the at least one characteristic of the exterior air indicates a dew point of the exterior air is less than a dew point of the interior air as indicated by the at least one characteristic of the interior air. In versions of these embodiments the method further includes the step of causing the compressor to be active when: the at least one characteristic of the interior air indicates a dry bulb temperature of the interior air is above the set point, and at least one of the following two conditions is met: (1) the at least one characteristic of the exterior air indicates a dry bulb temperature of the exterior air is greater than the dry bulb temperature of the interior air; and (2) the at least one characteristic of the exterior air indicates a dew point of the exterior air is greater than a dew point of the interior air as indicated by the at least one characteristic of the interior air. In versions of these embodiments the fan unit includes a second fan and when the compressor is activated the second fan selectively circulates the exterior air over a condensing coil and into the exterior area. In versions of these embodiments the second fan selectively expels the interior air into the exterior area when: the at least one characteristic of the interior air indicates a dry bulb temperature of the interior air is greater than the set point, the at least one characteristic of the exterior air indicates a dry bulb temperature of the exterior air is less than the dry bulb temperature of the interior air, and the at least one characteristic of the exterior air indicates a dew point of to the exterior air is less than a dew point of the interior air as indicated by the at least one characteristic of the interior air. In versions of these embodiments the electronic controller may cause the compressor to be active when the at least one characteristic of the interior air indicates a dry bulb temperature of the interior air is above an AC set point, the AC set point being greater than the set point, and at least one of the following two conditions is met: (1) the at least one characteristic of the exterior air indicates a dry bulb temperature of the exterior air is greater than the dry bulb temperature of the interior air; and (2) the at least one characteristic of the exterior air indicates a dew point of the exterior air is greater than a dew point of the interior air as indicated by the at least one characteristic of the interior air.

In the control system and in the method the at least one characteristic of the interior air may include an interior relative humidity measurement and the at least one characteristic of the exterior air may include an exterior relative humidity measurement. The at least one characteristic of the interior air may include an interior dry bulb temperature measurement and the at least one characteristic of the exterior air may include an exterior dry bulb temperature measurement; an interior dew point may be calculated from the interior dry bulb temperature measurement and the interior relative humidity measurement; an exterior dew point may be calculated from the exterior dry bulb temperature measurement and the exterior relative humidity measurement; and the interior dew point may be compared to the exterior dew point to thereby determine if the dew point of the exterior air is less than the dew point of the interior air. The at least one characteristic of the interior air may include an interior dry bulb temperature measurement and the at least one characteristic of the exterior air may include an exterior dry bulb temperature measurement; an interior specific humidity level may be calculated from the interior dry bulb temperature measurement and the interior relative humidity measurement; an exterior specific humidity level may be calculated from the exterior dry bulb temperature measurement and the exterior relative humidity measurement; and the exterior specific humidity level may be compared to the specific humidity level to thereby indirectly determine if the dew point of the exterior air is less than the dew point of the interior air.

DETAILED DESCRIPTION

Furthermore, and as described in subsequent paragraphs, the specific mechanical configurations illustrated in the drawings are intended to exemplify embodiments of the invention and that other alternative mechanical configurations are possible.

Referring now to the drawings wherein like numerals indicate like elements throughout the several views that are shown inFIGS. 1-24various aspects of a fan system or fan unit. The fan system may inhibit rain passage through the housing and dispels the rain without the water content entering the interior area of the building. The fan unit may also comprises a barrier or louver system to, among other things, open and close vents to limit heat transfer through the system when the fans are turned off. Additionally, the fan unit may have a ducting arrangement which pulls air into a room and exhausts air from the room to improve circulation and may utilize a fan arrangement to aid with the circulation. The fan system also utilizes a control system to selectively utilize outside air having desirable characteristics which cools the room and may be also used with existing air conditioning, therefore decreasing the reliance on an air conditioning system, and saving energy and costs associated with air conditioning operation. The fan system may also optionally incorporate selective air conditioning functionality.

Referring now toFIG. 1, a perspective view of a window fan system10is depicted on a window sill and with a window sash (both shown in broken line) engaging an upper surface of the window fan system10. Positioned about the lower portion of the fan system10is a lower housing12which wraps around the front and sides of the fan system10and may be formed of metal, plastic or other resilient material and which has aesthetically pleasing qualities. A power cord14is shown extending from a side of the lower housing12and may extend to a power supply such as an in-wall power outlet (not shown). Adjacent to power cord14is a sill bracket16which allows for adjustable connection to the window sill wherein the window fan system10is positioned. Although a sash type window is depicted, it should be understood that use of the window fan system10may be used with slider type window which slides in a horizontal direction rather than a vertical direction.

Within the lower housing12is an outside air exhaust18. When outside air is entrained into the fan system10and passes through at least one fan within the window fan system10, the outside air is exhausted into the building or room through the outside air exhaust18. The outside air exhaust18is positioned on the lower area of the housing so that an upper intake30can remove hotter air from the room. The outside air exhaust18may be opened or closed to allow or inhibit airflow into the room or area being cooled.

Above the lower housing12is an upper housing20which may also be formed of metal, plastic or other resilient material like the lower housing12and may be matching. The upper and lower housings20,12of the exemplary embodiment are depicted as separate housing pieces, however, such housing elements12,20may be combined into a single one-piece housing. Additionally, the upper housing20comprises a control panel22having a display24and at least one control button26. Adjacent to the control panel22is a room exhaust intake30. The window fan system10also exhausts air from inside the building to outside in order to improve circulation within the room or building. Thus, cooler air comes into the building through the outside air exhaust18and hotter air is withdrawn from the room through the upper room exhaust intake30. With the room exhaust intake30on the upper surface of the window fan system10, the room exhaust intake30can better draw warm air from the room and move it outside. Conversely, the outside air exhaust18is at a lower position, as this air is cooler than the warmer air being exhausted by the room exhaust intake30. This configuration aids circulation since warm air rises and cooler air descends.

The surrounding window structure is shown in broken line to provide environmental understanding of how the window fan system10is placed in the window and when the sash is closed against the upper surface of the upper housing20. Positioned on the upper housing20is an adjustable sash bracket28. This bracket provides an adjustable width to fit various sizes of window sash. The bracket28also provides adjustability to compensate for the position the window fan10is inwardly or outwardly relative to the window sill beneath the system10. For example, some windows will require further positioning of the system10toward the interior of the building than other windows. The sash bracket28also aids to compensate for such adjustments.

Referring now toFIG. 2, a side schematic view of a room is depicted. A window fan system10is depicted in a sidewall of the room. A lower fan draws air into the room which circulates across the room, up an opposite wall, along the ceiling and down the wall in which the window fan unit10is positioned. Additionally, it will be understood that the air moving into the room may move along the walls toward the window fan system10. As the air moves along the walls toward the system10, any rising temperature of the air will cause the air to rise nearer the fan system10. A second upper fan draws air from within the room and out to atmosphere. As previously indicated, the upper fan is utilized to draw air from the room since warmer air will be higher in the room. In comparison withFIG. 15, one of skill in the art will recognize that where the prior art device fails by not removing air from the interior, the instant embodiment removes warmer air increasing circulation, which ultimately aids in cooling the room. The vertical circulation pattern created by the fan system10eliminates temperature stratification of prior art devices with air intake and air exhaust both in the same vertical elevation

Referring now toFIG. 3, a rear perspective view of the window fan system10is depicted. The rear side of the window fan system10is positioned on the outside of the building being cooled both drawing air into the room and exhausting air out of the room. With the upper housing20, the lower housing12and the rear louver32all removed, a frame40is revealed. The frame40comprises a first side member41and a second opposed side member43. Both the first side member41and the second side member43are vertical members and substantially parallel to one another in the exemplary embodiment although such design should not be considered limiting. Along the upper side of the frame40and connecting the first side member and second side member41,43is an upper frame member42. The upper frame member42is substantially horizontal and opposite to an opening44which is defined by a first strut45and an opposed second strut46. Around the mid-portion of the frame40, in a vertical direction is a partition38which separates the upper exhaust portion50from the lower intake portion52of the window fan system10. On the upper side of the fan partition38, is an upper fan housing54. Beneath the partition38in the lower intake portion52is a lower fan housing56. Each of the housings54,56may be formed of one or more housing portions which are connected in various manners or alternatively may be formed integrally.

Referring now toFIG. 4, a perspective view of a window fan system10is depicted with the internal components of the system10removed. Through the openings of the upper housing20, the rear louver32may be seen which is positioned on the outwardly facing side of the window fan system10. The rear louver32covers the upper exhaust portion50and the lower intake portion52(FIG. 3). These portions50,52are separated by the partition38(FIG. 2) so as to create two separate air pathways. The lower intake portion52pulls outside air into the system10directs the air into the building or home through the outside air exhaust18. The upper exhaust portion50pulls air from the room or building interior through the room exhaust intake30and directs this warmer air out of the upper half of the rear louver32.

Within the lower area of the system10, a dam60may be seen adjacent the rear louver32. The dam60is located generally between the first and second struts45,46(FIG. 2). The dam60may be separately formed and positioned between the struts45,46or, alternatively the dam60may be integrally formed with lower housing portion12, frame40, or other portions of the fan system10. In either formation, the dam60inhibits water passage through the fan system10. Water passing through the lower portion of rear louver32encounters the dam60as it moves into or toward the lower intake portion52. The dam inhibits the water droplet from passing though the housing and into the room. The dam60performs this function by creating a reservoir for water droplets which fall out of the airstream being pulled into the housing. In other words, the dam60effectuates removal from the entrained water droplets from the airflow. Afterward, the fallen water droplets are gravity fed to a well62(FIG. 6) where the water may drain through the housing and out of the system10and may be aided by the lower fan at the bottom of the fan blade.

Referring now toFIGS. 5 and 6, a partially sectioned rear perspective view and side sectioned view of the window fan unit10are depicted. The rear louver32comprises a plurality of vertical fins32aand a plurality of horizontally extending fins32b. The horizontally extending fins32bare tilted at an angle which slopes downward from the inside of the system10to the outside. The fins32a,32bare fixed and are sloped in order to deflect rain which might otherwise be pulled into the lower half of the louver32and into the lower intake portion52. According to the exemplary embodiment, the slope of the horizontal fins is 5%, although such slope should not be considered limiting as other slopes may be utilized. Additionally, an aspect ratio of the rear louver32is defined as being about two-to-one (2:1). The term aspect ratio means that, as measured between vertical fins32a, the width of the horizontal fin32bis twice the vertical distance between louvers. Again this aspect ratio is merely exemplary, as other ratios may be utilized. The illustrative aspect ratio is utilized also for its ability to deflect rain which may be entrained near the lower intake portion52of the louver32.

From this view, one skilled in the art will realize that the upper exhaust portion50(FIG. 2) which blows air outwardly through the upper portion of the louver32also aids to clear the airspace immediately above the lower intake portion52(FIG. 2) of louver32of rain and other contaminants which may be otherwise pulled into the lower intake portion52by the lower fan. For purpose of this description, the term contaminants should be understood to mean rain, snow or other weather elements in addition to other elements which may be found in the outside air. Thus, the present embodiment utilizes a louver32having fin characteristics which aid to inhibit rain from entering the window fan system10. The arrangement of an upper fan system80blowing outwardly and a lower fan74pulling air inwardly aids to blow rain away from the lower portion of louver32inhibiting rainwater from entering the window fan system10during use. Additionally, any rainwater which passes through the rear louver32may be impinged on the dam60adjacent the lower intake fan74or alternatively slowed by the dam60causing the water to fall or drain into the well62.

As shown near the bottom of the window fan system10, and between the first and second struts45,46, the dam60has an upper surface61which generally slopes from an upper point closer to fan74to a lower point near the louver32. The dam60receives some water which passes through the louver32. Typically, the flow path of the water may be interrupted by the louvers32and this disruption in velocity causes the water droplets to fall onto the upper surface onto the dam60. The slope of dam60, in combination with gravity, causes water to drain down this dam slope into a well62(FIG. 6).

Moving away from the louver32, beyond the dam60, an intake fan assembly70is depicted. The fan assembly70includes a motor72which may be a 120 Volt motor having a high speed of approximately 1425 RPM, a medium speed of approximately 1322 RPM, and a low speed of approximately 1184 RPM. Connected to the fan motor72is a blower or fan74. The blower or fan74may be a centripetal fan which draws air into the top portion beneath the partition38. Alternatively, various types of fans may be used, for example centrifugal, tangential or cross-flow fans. The blower74is generally cylindrical in shape having a plurality of horizontal fins which may be slightly curved and connected by a plurality of axially aligned ribs. The blower74is operably connected to the fan motor72and spins about a central axis with the motor72. In the views shown inFIGS. 5 and 6, the motor72rotates in a substantially counterclockwise direction which pulls air inwardly through the lower portion of louver32and moves the air upwardly through the blower housing56and expels the accelerated air through the room air exhaust18. The blower housing56is connected to the partition38which separates the lower intake portion52(FIG. 2) from the upper exhaust portion50(FIG. 2).

Still referring toFIGS. 5,6and7, the partition38includes a sloped portion closest to the rear louver32. The sloped portion of the partition38also utilizes gravity to remove any water which may gather in this area of the fan and drains this water to the dam60or the well62. At the downhill side of the dam60is a well62. The function of the well62is to receive water which runs off the slope surface of the dam60and remove the water from the fan system10. A plurality of apertures64are seen at a lower surface of the window fan unit10. These apertures64function as drain holes and are located generally in the bottom of the well62. A plurality of ribs66are positioned on the lower surface of the dam60which eliminates the need to make a solid dam60and saves weight while strengthening the part. As previously described the dam60may be separately formed or integrally formed with the housing12, frame40, or other parts.

Above the partition38, an upper exhaust fan assembly80is positioned. Similar to the lower fan assembly70, the upper exhaust fan assembly80comprises a fan motor82and a centripetal fan or blower84. The upper fan assembly80removes air from the building interior through the room exhaust intake30, through the blower74and out to atmosphere through the upper portion of the rear louver32.

Referring now toFIG. 8, the window fan unit10is depicted with the lower housing12and upper housing20removed. Extending from the frame40is a room exhaust intake30having a plurality of louvers34which are pivotally positioned within a louver frame36. The louver frame36functions as a duct through which air passes from the room, through the room exhaust intake30, louvers34and into the upper fan assembly80. Beneath the louver frame36is the upper fan cowling56which is curved to proximate the curvature of the blower84and includes a plurality of stiffening ribs along the outer surface thereof.

Beneath the room exhaust intake30, is the outside air exhaust18, which also comprises a louver housing90and a plurality of pivotable louvers92. The louver housing90also functions as a duct adjacent to the lower fan assembly70and allows air passage through the outside air exhaust18into the room or building where the window fan unit10is positioned.

Referring now toFIG. 9, a perspective view of the room exhaust intake30and the outside air exhaust18is shown in a rear perspective view through which air passes from a building interior to the outside of the building. The upper louver frame36includes a plurality of louvers34positioned therein. The louvers34may be pivoted open to allow air flow when the system10is in operation. Alternatively, when the window system10is not operating, the louvers34may be closed to inhibit flow of air from the interior of the room to the outside or vice versa depending on the temperature difference between the outside ambient air and the inside air temperature. The louver frame36includes a plurality of moldings and fastening apertures for connection to the frame40(FIG. 7) or other components of the system10.

Beneath the room exhaust intake30is the outside air exhaust18. The louver housing90defines a duct area through which air passes from the fan system80to the room interior. Within the lower housing90are a plurality of pivotally connected louvers92which also open and close depending on the state of the window fan system10. The lower housing90also includes a plurality of moldings and apertures for connecting the lower housing90to the frame40or adjacent structure. As best seen inFIG. 8, positioned about the front area of the housings36,90and louvers34,92are trim elements which define portions of the outer housings12,20.

The louvers34,92may, according to one embodiment, move independently of one another. Alternatively, in the exemplary embodiment depicted, and described hereinafter, a linkage system100is utilized to open and close the louvers34,92simultaneously. The linkage system100comprises an actuator motor102. An actuator arm104is operably connected to the motor with a pivot point106and first and second linkage connections108,109.

Referring now toFIG. 10, a perspective view of the linkage system100is depicted. Connected to the arm104at pivot point109(FIG. 9) is a lower linkage110. The lower linkage110connects to a lower louver pivot mechanism112. This mechanism112includes at least one arm114, connected to lower linkage110. The upper linkage120extends to an upper pivot mechanism122having an arm124. Both arms114,124pivot to move the corresponding louvers92,34.

Referring now toFIGS. 11 and 12, perspective views of the pivot mechanism122are depicted with the louvers34in first and second positions. Arm124is generally v-shaped and pivotally connected to the louver frame36. A slide member126is connected to the arm124and slides along a surface of the louver frame136as the arm124rotates with movement of linkage arm120. Each of the louvers34are operably connected to the slide126so that movement of the arm124causes movement of the slide126, and therefore movement of the louvers34. In sum, according to the exemplary embodiment, the actuator motor102pivots each of the louvers34with a single motion via the arm124and slide member126. As shown inFIG. 11, the louvers34are in an open position. As the arm124is rotated and the slide member126moves, the louvers34rotate to a closed position.

Referring now toFIGS. 13 and 14, perspective views of the lower pivot mechanism112are depicted with the louvers in first and second positions. Depending from the actuator motor102is the lower linkage110which engages an arm134. Extending from the lower housing90is a pivot structure about which the arm134rotates. Also connected to the arm134is a lower slide member136. The plurality of louvers92are each pivotally connected to the slide member136so that rotation of the arm134causes pivotal movement, opening or closing, of the louvers92.

Referring now toFIG. 16, a top view of a second embodiment of a control panel122is depicted. Both control panels22,122may be in electronic communication with the fan systems70,80as well as linkage system100for controlling the window fan system10. Control panel122may be located, for example, in a similar location as control panel22on window fan system10. Control panel122includes a display124that provides an area for displaying a current dry bulb temperature of the room or interior air and an area for displaying the current set point temperature that has been selected by a user. A power push button126ais provided to enable a user to selectively power window fan system10and a fan push button126bis provided to enable a user to cause lower fan74and upper fan84to be set to a low, medium, high, or automatic setting. AUTO LED125a, HIGH LED125b, MED LED125c, and LOW LED125dare selectively illuminated to convey to a user which setting is selected for lower fan74and upper fan84. Similarly, ON LED125eis illuminated when the window fan system10is powered on to convey to a user that it is powered. A set point “+” button126cand a set point “−” button126dare provided to enable a user to increment the set point upwardly or downwardly, respectively. The area of display124for displaying the current set point temperature conveys to a user the currently selected set point.

Referring now toFIG. 17, a schematic representation of an embodiment of a control system for a window fan is depicted. Power button126a, fan button126b, set point “+” button126c, and set point “−” button126dof control panel122are in selective electrical communication with controller210, causing one or more signals to be sent to controller210when they are actuated. Controller210is also in electrical communication with AUTO LED125a, HIGH LED125b, MED LED125c, LOW LED125d, and ON LED125eof control panel122and is programmed to selectively illuminate the LEDs based on input received from a user via power button126a, fan button126b, set point “+” button126c, and/or set point “−” button126d. Outdoor sensor96and indoor sensor98are also in electrical communication with controller210and may communicate one or more signals to controller210that are indicative of one or more characteristics of exterior air and interior air, respectively. Such characteristics include, without limitation, dry bulb temperature, wet bulb temperature, absolute humidity, specific humidity, relative humidity, pressure, and/or dew point temperature. Controller210is also in electrical communication with relays214for lower fan motor72and upper fan motor82and drivers218for actuator motor102. The relays214are in electrical communication with lower fan motor72and upper fan motor82and can be selectively activated to cause lower fan motor72and upper fan motor82to be driven at a desired speed of a plurality of speeds. In some embodiments three relays are provided and may be selectively activated to drive lower fan motor72and upper fan motor82at either a low, medium, or high speed. The drivers218are in electrical communication with actuator motor102and may be selectively activated to accurately control actuator motor102and, resultantly, louvers34and92. In some embodiments four driver channels may be provided in electrical communication with actuator motor102and may be selectively activated to provide full stepping or half stepping of the actuator motor102.

In some embodiments Power button126a, fan button126b, set point “+” button126cand set point “−” button126dmay be membrane type buttons that engage a corresponding switch on a circuit board adjacent the control panel122when actuated. The circuit board may also include the controller210, AUTO LED125a, HIGH LED125b, MED LED125c, LOW LED125d, ON LED125e, display124, relays214for lower fan motor72and upper fan motor82, and/or drivers218for the actuator motor102. The control may be a PIC microcontroller model number PIC18LF4331-1/PT, the actuator motor102may be a PM Step Motor 24BYJ model manufactured by Best Electronics Industrials Co., Ltd., and outdoor sensor96and indoor sensor98may be Relative Humidity and Temperature Modules HTG3500 Series manufactured by Measurement Specialties. Referring briefly toFIGS. 5-7, outdoor sensor96may be located just inside louver32near the base of louver32and strut45. In the depicted embodiment the outdoor sensor96is located near lower intake portion52so as to be appropriately exposed to exterior air. Referring briefly toFIG. 8where a portion of control panel22is shown cut away, and toFIGS. 5 and 6, indoor sensor98may be located on a circuit board205adjacent the control panel22in a position so as to be exposed to the interior air and be relatively unaffected by any heat generated by other components attached to the circuit board205. InFIGS. 1 and 5apertures23are shown that extend through control panel22to enable indoor sensor98to be appropriately exposed to indoor air. Outdoor sensor96and indoor sensor98may be located elsewhere on window fan system10or may be located remote from window fan system10, so long as they are located to be responsive to one or more characteristics of the exterior air and interior air, respectively. Outdoor sensor96and indoor sensor98may be in wired or wireless electronic communication with electronic controller210.

Referring now toFIG. 18, a flow diagram shows an embodiment of the generalized logic of controller210when fan button126bis actuated by a user. If it is the first time fan button126bhas been pressed, the controller210causes AUTO LED125ato be illuminated and controller210automatically operates the window fan system10. An embodiment of the automatic operation of the window fan system is shown in detail inFIG. 20and described in detail hereinafter. If it is the second time fan button126bhas been pressed, the controller210causes HIGH LED125bto be illuminated, communicates with relays214to cause them to all be activated, causing lower fan motor72and upper fan motor82to operate at a high speed. Controller210also communicates with drivers218to ensure actuator motor102is appropriately stepped to place louvers34and92in an open position to allow airflow through window fan system10. If it is the third time fan button126bhas been pressed, the controller210causes MED LED125cto be illuminated, communicates with relays214to cause two relays to be activated, causing lower fan motor72and upper fan motor82to operate at a medium speed. Controller210also communicates with drivers218to ensure actuator motor102is appropriately stepped to place louvers34and92in an open position to allow airflow through window fan system10. If it is the fourth time fan button126bhas been pressed, the controller210causes LOW LED125dto be illuminated, communicates with relays214to cause a single relay to be activated, causing lower fan motor72and upper fan motor82to operate at a low speed. Controller210also communicates with drivers218to ensure actuator motor102is appropriately stepped to place louvers34and92in an open position to allow airflow through window fan system10.

Referring now toFIG. 19, a flow diagram shows an embodiment of the generalized logic of controller210when set point “+” button126cis actuated by a user and when set point “−” button126dis actuated by a user. If the set point “+” button126cis actuated controller210increments the currently stored set point up by one degree. The controller210also causes the area of display124that displays the current set point temperature to be updated to reflect the current set point temperature selected. If the set point “−” button126dis actuated controller210increments the currently stored set point down by one degree. The controller210also causes the area of display124that displays the current set point temperature to be updated to reflect the current set point temperature selected. In alternative embodiments increments smaller or larger than one degree may be used.

Referring now toFIG. 20, a flow diagram shows an embodiment of the generalized logic of controller210automatically operating the window fan system10. In the flow diagram ofFIG. 20interior dry bulb temperature (I. D. B.), exterior dry bulb temperature (E. D. B.), interior dew point (I. D. P), and exterior dew point (E.D.P.) are analyzed by controller210. In some embodiments indoor sensor98and outdoor sensor96supply signals to controller210that are indicative of measured interior and exterior dry bulb temperatures and relative humidity levels and controller210calculates an interior and exterior dew point that correspond to the measured interior and exterior dry bulb temperatures and relative humidity levels. In some embodiments controller210could calculate dew points by referencing a table, such as a table containing dry bulb temperatures, relative humidity levels, and dew point temperatures to determine a dew point temperature that corresponds to the measured dry bulb temperature and relative humidity level. In some embodiments controller210could calculate dew points by using one or more formulas. For example, the dew point could be calculated using the formula: Dew Point Temperature=[(17.271*Dry Bulb Temperature)/(237.7+Dry Bulb Temperature)]+ln(Relative Humidity/100), where the temperatures are in degrees Celsius and “ln” refers to the natural logarithm.

In other embodiments indoor sensor98and outdoor sensor96could measure alternative or additional characteristics of the interior and exterior air and supply signals to controller210indicative of such characteristics. Such characteristics include, without limitation, dry bulb temperature, wet bulb temperature, absolute humidity, specific humidity, relative humidity, pressure, and/or dew point temperature. Controller210could then use these alternative or additional characteristics to compare, either directly or indirectly, exterior and interior dry bulb temperatures and exterior and interior dew points for use in the automatic operation of the window fan system10. For example, instead of measuring interior and exterior relative humidity, determining the interior and exterior dew point from the relative humidity measurements, and directly comparing the interior and exterior dew point, interior and exterior relative humidity could be measured, interior and exterior specific relative humidity determined from the relative humidity measurements, and interior and exterior specific relative humidity directly compared. Comparison of the exterior specific humidity and interior specific humidity may indirectly indicate the exterior dew point is less than the interior dew point. For example, if the exterior specific humidity is less than the interior specific humidity it may indirectly indicate that the exterior dew point is less than the interior dew point. Other characteristics of exterior and/or interior air may be measured and analyzed to directly or indirectly determine if the exterior dew point is less than an interior dew point. Temperatures can be set, measured, calculated, and/or displayed in Celsius and/or Fahrenheit as desired.

If automatic operation of the window fan system10has been chosen by a user, at step252controller210determines if the interior dry bulb temperature as indicated by indoor sensor98is greater than the current set point temperature plus one degree. Comparing the interior dry bulb temperature to the current set point temperature plus one degree at this point in the flow diagram prevents excessive cycling of the lower fan motor72and upper fan motor82. If at step252the interior dry bulb temperature is determined to be greater than the current set point temperature plus one degree, at step254controller210determines if the interior dry bulb temperature is greater than the current set point. If the interior dry bulb temperature is greater than the current set point, at step256controller210determines if the exterior dry bulb temperature is less than the interior dry bulb temperature. If the exterior dry bulb temperature is less than the interior dry bulb temperature, at step258controller210determines if the exterior dew point minus five tenths is less than the interior dew point. If so, at step260then the controller210turns the motor flag on and opens louvers34and92.

The controller210then determines at step262if the difference between the interior dry bulb temperature and the current set point temperature (Δ D.B.) is less than or equal to two. If so, at step266the controller210activates the necessary relays to drive the lower fan motor72and upper fan motor82at low speed. If the difference between the interior dry bulb temperature and the current set point temperature is not less than or equal to two, the controller210determines at step264if the difference between the interior dry bulb temperature and the current set point temperature is greater than two and less than or equal to three. If so, at step268the controller210activates the necessary relays to drive the lower fan motor72and upper fan motor82at medium speed. If the difference between the interior dry bulb temperature and the current set point temperature is not greater than two and less than or equal to three, then at step270the controller210activates the necessary relays to drive the lower fan motor72and upper fan motor82at high speed. In other embodiments more or fewer than three fan speeds corresponding to more or fewer temperature differentials may be provided. For example, in some embodiments one or more fans may be driven at five preselected speeds corresponding to five different temperature differential ranges. Also, for example, in some embodiments one or more fans may be driven at a plurality of continuously variable speeds each corresponding to a temperature differential.

Once the controller210has activated the necessary controls to drive the lower fan motor72and upper fan motor82at low speed in step266, medium speed in step268, or high speed in step270, a two minute countdown timer is started in step274. After the two minute timer is completed the controller210checks to see if the motor flag is on in step276(the motor flag will be on if the conditions of steps254,256, and258were met in the previous loop). If the motor flag is on then controller210will proceed to determine if the conditions of steps254,256, and258continue to be met. If the conditions of steps254,256, and258are met, controller210will again check the difference between the interior dry bulb temperature and the current set point temperature at steps262and264to determine if the speed at which the lower fan motor72and upper fan motor82are being driven needs to be adjusted. If the conditions of steps254,256, or258are not met than at step272the motor flag will be turned off if it is on, lower fan motor72and upper fan motor82will also be turned off, and then the two minute timer of step274executed. Following execution of the two minute timer, the process will proceed to step252(since the motor flag is no longer on) to determine if the indoor dry bulb temperature is greater than the current set point temperature plus one degree. If the interior dry bulb temperature is not greater than the current set point temperature plus one degree, controller210again executes a two minute timer at step274and after the timer has run again proceeds to step252to determine if the indoor dry bulb temperature is greater than the current set point plus one degree.

Automatic operation of the window fan system10will continue until a user chooses a different fan setting through actuation of fan button126bor powers the window fan system down through actuation of power button126a. Automatic operation of the window fan system10brings exterior air into an interior area and exhausts interior air to an exterior area when doing so would be advantageous in cooling the interior area as desired by a user. Automatic operation of the window fan system10may result in energy savings without requiring consistent monitoring by a user and without the need to sync the window fan system10with an air conditioner or other device.

The methods and control systems described herein, as well as variations thereof, may be implemented in an air conditioning unit that includes a compressor and one or more fans that selectively draw exterior air into an interior area. Such one or more fans may also selectively draw in interior air, circulate the interior air over cooling coils, and exhaust the circulated air back into the interior area. Such an air conditioning unit may also include one or more fans that selectively exhaust interior air to an exterior area. Such one or more fans may also selectively draw in exterior air, circulate the exterior air over a condenser, and exhaust the circulated air back into the exterior area. The compressor of the air conditioning unit may be selectively deactivated when bringing exterior air into an interior area and/or exhausting interior air to an exterior area would be advantageous in cooling the interior area.

For example, a hotel room air conditioning unit or a window room air conditioner unit may be installed in a wall or window and extend between a room and the outside. The air conditioning unit may include an interior sensor that monitors one or more characteristics of the air in the hotel room and an exterior sensor that monitors one or more characteristics of the outside air. The air conditioning unit may include a fan that selectively draws air from the outside and into the hotel room. Such a fan may be the same as, or to distinct from, a primary air conditioning fan that blows air into the hotel room that has first been cooled through an evaporator or other device. The air that is cooled by an evaporator or other device may optionally, and preferably, be drawn from inside the hotel room. The air conditioning unit may be programmed to utilize the compressor to cool air being blown from the air conditioning unit into a room interior when the desired set point is less than the current room interior temperature and bringing exterior air into the room interior would not be advantageous in cooling the interior area. The hotel room air conditioning unit may further be programmed to deactivate the compressor and provide exterior air into the room interior when the desired cooling temperature is less than the current room interior temperature and bringing exterior air into the room interior would be advantageous in cooling the interior area. Such an air conditioning unit may also optionally include a second fan that selectively draws air from the exterior area, forces the air over a condenser, and expels the air back into the exterior area. The second fan may perform such functionality at least when the compressor is activated. The second fan may also optionally function to expel interior air to an exterior area when the compressor is deactivated.

AC operation may be desired in such a hotel room air conditioning unit when at least one characteristic of the interior air indicates a dry bulb temperature of the interior air is above the current set point and at least one of two conditions is met. The first condition being that at least one characteristic of the exterior air indicates a dry bulb temperature of the exterior air is greater than the dry bulb temperature of the interior air. The second condition being that at least one characteristic of the exterior air indicates a dew point of the exterior air is greater than a dew point of the interior air. Optionally, a separate AC set point may be provided that is a greater temperature than the set point for fan only non-AC operation. For example, the AC set point may be eighty degrees and the fan only set point may be seventy degrees. Accordingly, the window fan may operate with AC functionality when a dry bulb temperature of the interior air is above the current AC set point and either: a) at least one characteristic of the exterior air indicates a dry bulb temperature of the exterior air is greater than the dry bulb temperature of the interior air or b) at least one characteristic of the exterior air indicates a dew point of the exterior air is greater than a dew point of the interior air. The window fan may operate with fan only operation when at least one characteristic of the interior air indicates a dry bulb temperature of the interior air is greater than the current fan only set point, the dry bulb temperature of the exterior air is less than the dry bulb temperature of the interior air, and the dew point of the exterior air is less than (or equal to) the dew point of the interior air.

Referring now toFIGS. 21A and 21B, a front view and a top section view, respectively, of a window fan system401that includes air conditioning functionality is provided. As described in additional detail herein, the window fan system401is in a state for providing air conditioning inFIGS. 21A and 21B. The window fan system401includes a housing412that may be installed such that it extends between an interior area and an exterior area. A window sill, visible on both sides of the housing412inFIG. 21B, generally defines the barrier between the interior area and the exterior area.FIG. 21Aprovides a front view (from the interior area side) of the window fan unit410. Actuable front louvers487are visible in an open state inFIG. 21Aand provide for selective intake of interior air when they are in the open state and the window fan system401is in an air conditioning mode. An air discharge489is also visible inFIG. 21Aand provides for cooled air discharge into the interior area when the window fan system401is in the air conditioning mode. A control panel422is also visible inFIG. 21A. Control panel422may have a similar configuration as control panel22and/or control panel122and may include one or more indicators and/or displays such as, for example, those shown inFIG. 23.

Inside the housing412is a fan motor475that is coupled to and drives a blower or indoor fan474and also drives an outdoor fan484. InFIG. 21Bthe indoor fan474is substantially isolated from exterior air by panel476, panel470, closed actuable intake barrier or door471and closed actuable exhaust bather or door473. The doors471and473are actubable in between at least a closed position (FIG. 21B) and an open position (FIG. 22B) and are actuated via a linkage472coupled to a motor such as, for example, an actuator motor. The panels476and470and the intake doors471and473span from proximal the top to proximal the bottom of the interior of the housing412to substantially isolate indoor fan474from exterior air. When window fan system401is running in the air conditioning mode, indoor fan474draws interior air in through the open front louvers487, through a filter488, through an evaporator coil497(which cools and/or dehumidifies the air), and back into the interior area through air discharge489. When window fan system401is running in the air conditioning mode, compressor495is activated and pumps a refrigerant through the evaporator coil497and also pumps the refrigerant through a condensing coil499located proximal a rear discharge of the window fan system401. When window fan system401is running in the air conditioning mode, the outdoor fan484draws exterior air in through one or more fixed louvers provided on the sides and/or top of the exteriorly positioned portion of the window fan system401. The fixed louvers may be provided, for example, in the sides and/or top of the window fan system at one or more locations between partition478and partitions470and476. The exterior air drawn in by the outdoor fan484is blown over the condenser coil499and discharged back into the exterior area.

The panel478is provided proximal the condenser coil499. The panel478has an opening therethrough and, accordingly, does not completely isolate the outdoor fan484from the area around the fan motor475. In some embodiments the opening may be substantially aligned with the fan484and may be of a slightly larger diameter than the fan. A base mount477is provided below the compressor495to support the compressor495. A control box housing479is provided proximal the evaporator coil and may house an electronic controller (e.g., electronic controller410ofFIG. 23) among other things. An outdoor sensor496is positioned so as to be in communication with exterior air and an indoor sensor498is positioned so as to be in communication with interior air. The outdoor sensor496and indoor sensor498may communicate one or more signals to the controller410that are indicative of one or more characteristics of exterior air and interior air, respectively.

Referring now toFIGS. 22A and 22B, a front view and a top section view, respectively, of the window fan system401is provided. As described in additional detail herein, the window fan system401is in a non-air conditioning fan only mode inFIGS. 22A and 22B. The actuable louvers487are visible in a closed state inFIG. 22A, thereby inhibiting passage of air therethrough. The air discharge489will provides discharge of exterior air into the interior area when the window fan system401is in the fan only mode. In the fan only mode the intake door471and the exhaust door473are both in a fully open position. In some embodiments the intake door471and/or the exhaust door473may only be partially opened in some or all aspects of fan only operations. The intake door471and the exhaust door473have been moved into the open position through actuation of linkage472. Indoor fan474is no longer isolated from the exterior air. Indoor fan474may now draw exterior air in through the fixed louvers provided on the exteriorly positioned portion of the window fan system401, through the opening that is created by intake door471being in the open position, through pollen filter469, and discharge the exterior air through air discharge489into the interior area. Also, outdoor fan484is no longer isolated from the interior air. Outdoor fan484may now draw interior air in through a fixed louver485provided on the side of the interiorly positioned portion of the window fan system401, through the opening that is created by the exhaust door473being in the open position, and discharge the interior air through condenser coils499and into the exterior environment. The compressor495is not operated in the fan only mode. When the window fan system401is not being operated, the doors471and473and/or the front louvers487may be closed to inhibit air exchange between the interior area and the exterior area. It is understood that the doors471and473may be closed, that the front louvers487may be opened, and the compressor495may be deactivated if a user (or the controller410) desires to have fan operation without air conditioning functionality and without drawing in exterior air and/or expelling interior air.

Referring now toFIG. 23, a schematic representation of an embodiment of a control system for the window fan system401that includes air conditioning functionality is provided. The control system ofFIG. 23has many elements in common with the control system ofFIG. 17and, except as otherwise described herein, like numbering between the two refers to similar parts with similar functionality. Accordingly, description concerning many aspects of the control system ofFIG. 22is omitted herein for purpose of conciseness. However, it is understood that those aspects of the control system ofFIG. 22having numbering of 4XX share a substantially common configuration with those aspects of the control system ofFIG. 17having numbering of XX or 1XX. For example, power button426ahas a common configuration as power button126a.

The fan set point “+” button426cand fan set point “−” button426dare in communication with controller410and are provided to enable a user to increment the fan only non-AC set point upwardly or downwardly, respectively. A separate AC set point “+” button426eand AC set point “−” button426fare in communication with controller410and are provided to enable a user to increment the AC set point upwardly or downwardly, respectively. In some embodiments a user may select both an AC set point and a fan only set point. In some embodiments a user may select an AC set point or a fan only set point and then may choose a desired temperature differential for the other of the AC set point and the fan only set point (e.g., a five degree temperature differential). In other embodiments the user may only enter in one of the AC set point and the fan only set point and the controller410may automatically determine the other of the AC set point and the fan only set point.

The controller410is also in communication with the compressor495. A relay, driver, and/or a motor may optionally be interposed between controller410and compressor495. The controller410causes the compressor495to be activated when AC functionality is desired. The controller410also is in communication with drivers418for actuator motors. The drivers418are in electrical communication with actuator motors402and may be selectively activated to accurately control one or more actuator motors402. The one or more actuator motors402may control, inter alia, movable louver487and linkage472. The controller410selectively causes drivers418to cause selective of the actuator motors402to appropriately actuate one or more barriers (e.g., louvers and/or doors). For example, when fan only operation is desired the controller410may cause drivers418to cause selective of the actuator motors402to close front lovers487and open doors471and473. The controller410causes fan motor475to be driven by fan motors414when fan only operation is desired and when AC operation is desired.

FIG. 24is a flow diagram of an embodiment of the generalized logic of a control when automatically operating the window fan system401that includes air conditioning functionality. The flow diagram ofFIG. 24has many elements in common with the flow diagram ofFIG. 20and like numbering between the two refers to similar steps with similar functionality. At step352the controller410determines if the interior dry bulb temperature as indicated by an indoor sensor is greater than the current fan set point temperature plus one degree. If at step352the interior dry bulb temperature is determined to be greater than the current set point temperature plus one degree, at step354controller410determines if the interior dry bulb temperature is greater than the current fan set point. If the interior dry bulb temperature is greater than the current fan set point, at step356controller410determines if the exterior dry bulb temperature is less than the interior dry bulb temperature. If the exterior dry bulb temperature is less than the interior dry bulb temperature, at step358controller310determines if the exterior dew point minus five tenths is less than the interior dew point. If so, at step360then the controller410turns the motor flag on, opens doors471and473, and closes front louvers487.

The controller410then determines at step362if the difference between the interior dry bulb temperature and the current fan set point temperature (Δ D.B.) is less than or equal to two. If so, at step366the controller410activates the necessary relays to drive the fan motor475at low speed. If the difference between the interior dry bulb temperature and the current fan set point temperature is not less than or equal to two, the controller410determines at step364if the difference between the interior dry bulb temperature and the current fan set point temperature is greater than two and less than or equal to three. If so, at step368the controller410activates the necessary relays to drive the fan motor475at medium speed. If the difference between the interior dry bulb temperature and the current fan set point temperature is not greater than two and less than or equal to three, then at step370the controller410activates the necessary relays to drive the fan motor475at high speed. One of ordinary skill in the art having had the benefit of the present disclosure will recognize that more or fewer than three fan speeds corresponding to more or fewer temperature differentials may be provided. For example, in some embodiments one or more fans may be driven at five preselected speeds corresponding to five different temperature differential ranges. Moreover, motor speed may optionally be continuously variable between a maximum and a minimum speed and may be driven at a desired speed based on, inter alia, a temperature range or a specific temperature differential

Once the controller410has activated the necessary controls to drive the fan motor475at an appropriate speed, a two minute countdown timer is started in step374. After the two minute timer is completed the controller410checks to see if the motor flag is on in step376. If the motor flag is on then controller410will proceed to determine if the conditions of steps354,356, and358continue to be met. If the condition of step354is not met, motor flag will be turned off if it is on, fan motor475will also be turned off, and then the two minute timer of step374executed. Following execution of the two minute timer, the process will proceed to step352(since the motor flag is no longer on) to determine if the indoor dry bulb temperature is greater than the current set point temperature plus one degree.

If during automatic operation the condition at step354is met, but either of the conditions at steps356and steps358is not met, then the controller410at step380checks to see if the interior dry bulb temperature is greater than the AC room set point. If the interior dry bulb temperature is not greater than the current AC room set point then the controller410progresses to step372. If, however, the interior dry bulb temperature is greater than the current AC room set point then the controller progresses to step382. At step382the controller410turns the motor flag on if it is off, turns on the compressor495, closes doors471and473, and opens front louvers487, thereby running the fan unit in AC mode. The controller then proceeds to step374, where a two minute countdown timer is initiated. After the two minute timer is completed the controller410checks to see if the motor flag is on in step376. If the motor flag is on then controller410will proceed to determine if the condition of steps354has been met and will then continue through the algorithm as previously described herein. While the unit is running in AC mode the speed of the motor475may optionally be proportional to the temperature differential between the AC room set point and the interior dry bulb temperature.

Automatic operation of the window fan system401will continue until a user chooses a different setting (e.g., manual AC mode or manual fan only mode) or powers the window fan system down. Automatic operation of the window fan system401brings exterior air into an interior area and exhausts interior air to an exterior area when doing so would be advantageous in cooling the interior area as desired by a user. Moreover, automatic operation of the window fan system401enables use of a compressor to cool interior air to prevent the interior air from heating beyond a user selected maximum level. Automatic operation of the window fan system401may result in energy savings without requiring consistent monitoring by a user and without the need to sync the window fan system401with a separate air conditioner or other device.