ENCLOSURE AND METHOD OF COOLING SAME USING AMBIENT AIR Cross-Reference to Related Applications:

[0001 ] The present application claims the benefit of U.S. Provisional Patent Application No. 61/436,550, filed January 26, 201 1 , the entire contents of which are hereby incorporated by reference.

Field of the Invention

[0002] The present invention is directed to an enclosure suitable for housing heat-producing communications equipment and to a method of cooling same, and, more specifically, to an air conditioned enclosure having a fan for drawing ambient air into the enclosure and a controller configured to operate the fan under predetermined temperature and/or humidity conditions and to a method of cooling the enclosure with the fan.

Background of the Invention

[0003] It is often necessary to provide telecommunications equipment in outdoor locations at remote sites, near cell-phone towers, for example, and such equipment must be protected from the environment and maintained in a predetermined temperature range. Enclosures, which may be constructed from metal, wood or masonry, are generally used to house this equipment, and the enclosures are provided with heating and/or cooling devices for temperature control. For example, it is known to provide such enclosures with a heat pump or similar device that transfers heat from or to the enclosure. It is also possible to heat and cool the enclosure with electrical arrangements such as resistive heating elements or thermoelectric coolers, Peltier elements, for example.

[0004] Such outdoor enclosures are may be subjected to substantial temperature changes over the course of a twenty-four hour period, and the heat produced by the telecommunications equipment may vary with cell-phone use. During the morning, for example, the temperature of the housing may increase both from increased exposure to sunlight and from increased cell phone use as the business day begins. Heavy cell phone use may persist into the evening, and the telecommunications equipment will thus add heat to the enclosure even as the sun sets. Finally, the interior of the enclosure may become so cool during the night, with no sun and limited cell-phone use, that a heater must be used to maintain the interior in a desirable temperature range. It would be desirable to reduce the amount of time that the air conditioner operates while maintaining the temperature of the interior of the enclosure in a desired range as the heat level in the enclosure varies throughout the day.

SUMMARY OF THE INVENTION

[0005] This and other problems are addressed by embodiments of the present invention, a first aspect of which comprises a method of regulating the temperature of an enclosure housing heat-producing equipment. The method includes providing an air conditioner having a first state in which the air conditioner cools an interior of the enclosure and a second state in which the air conditioner does not cool the interior, providing a fan having a first condition in which the fan draws air into the interior and a second condition in which the fan does not draw air into the interior, and providing at least one controller for controlling the air conditioner and the fan. The method also includes detecting a temperature of the interior of the enclosure, placing the air conditioner in the first state and cooling the interior using the air conditioner when a temperature of the interior is greater than or equal to an "on" temperature and placing the air conditioner in the second state and ceasing to cool the interior using the air conditioner when the temperature of the interior is less than or equal to an "off temperature, the off temperature being less than the on temperature by a predetermined value. The method also includes determining an ambient temperature outside the enclosure, detecting a shift of the air conditioner from the first state to the second state and based on the air conditioner shifting from the first state to the second state, if the ambient temperature is less than the off temperature, placing the fan in the first condition to draw air into the interior until the temperature of the interior is less than the off temperature by a first amount and, in response to the temperature of the interior becoming less than the off temperature by the first amount, placing the fan in the second condition.

[0006] Another aspect of the invention comprises a method of supplementing the cooling of an air conditioned enclosure cooled by an air conditioner, wherein the air conditioner has a controller for setting a maximum desired temperature for the enclosure, a first state in which the air conditioner cools an interior of the enclosure and a second state in which the air conditioner does not cool the interior. The method includes providing a fan having a first condition in which the fan draws air into the interior at a first rate and a second condition in which the fan does not draw air into the interior, providing a fan controller for controlling the fan, determining a temperature of the interior of the enclosure, determining an ambient temperature outside the enclosure, and detecting a shift of the air conditioner from the first state to the second state. In response to the air conditioner shifting from the first state to the second state, the method includes providing the fan controller with a value indicative of the temperature of the interior and setting a fan set temperature in the fan controller based on the value and, if the ambient temperature is less than the fan set temperature, placing the fan in the first condition to draw air into the interior until the temperature of the interior is less than the fan set temperature by a first amount and, in response to the temperature of the interior becoming less than the fan set temperature by the first amount, placing the fan in the second condition.

[0007] A further aspect of the invention comprises an enclosure housing heat- producing equipment, an air conditioner having a first state in which the air conditioner cools an interior of the enclosure and a second state in which the air conditioner does not cool the interior, a fan having a first condition in which the fan draws air into the interior and a second condition in which the fan does not draw air into the interior, at least one controller for controlling the air conditioner and the fan, a first temperature sensor for detecting a temperature of the interior of the enclosure, and a second temperature sensor for determining an ambient temperature outside the enclosure. The controller is configured to place the air conditioner in the first state when a temperature of the interior is greater than or equal to an on temperature and to place the air conditioner in the second state when the temperature of the interior is less than or equal to an off temperature, the off temperature being less than the on temperature by a predetermined number of degrees and, if the ambient temperature is less than the off temperature and the air conditioner is in the second state, place the fan in the first condition until the temperature of the interior is less than the off temperature by a first amount and, in response to the temperature of the interior becoming less than the off temperature by the first amount, place the fan in the second condition.

BRIEF DESCRIPTION OF THE DRAWINGS

[0008] These and other aspects of the invention will be better understood after a reading of the following detailed description together with the attached drawings wherein:

[0009] Figure 1 is sectional side elevational view of an enclosure cooled by an air conditioner and by a fan controlled by a fan controller.

[0010] Figures 2-6 are schematic illustrations of arrangements for communicating an operating state of the air conditioner to the fan controller.

[001 1 ] Figure 7 is a flow chart illustrating a method according to an embodiment of the invention.

[0012] Figure 8 is a flow chart illustrating a method according to another embodiment.

DETAILED DESCRIPTION

[0013] The present invention now is described more fully hereinafter with reference to the accompanying drawings, in which embodiments of the invention are shown. This invention may, however, be embodied in many different forms and should not be construed as limited to the embodiments set forth herein; rather, these embodiments are provided so that this disclosure will be thorough and complete, and will fully convey the scope of the invention to those skilled in the art.

[0014] Like numbers refer to like elements throughout. In the figures, the thickness of certain lines, layers, components, elements or features may be exaggerated for clarity. The terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting of the invention. Unless otherwise defined, all terms (including technical and scientific terms) used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention belongs. It will be further understood that terms, such as those defined in commonly used dictionaries, should be interpreted as having a meaning that is consistent with their meaning in the context of the specification and relevant art and should not be interpreted in an idealized or overly formal sense unless expressly so defined herein. Well-known functions or constructions may not be described in detail for brevity and/or clarity.

[0015] As used herein, the singular forms "a", "an" and "the" are intended to include the plural forms as well, unless the context clearly indicates otherwise. It will be further understood that the terms "comprises" and/or "comprising," when used in this specification, specify the presence of stated features, integers, steps, operations, elements, and/or components, but do not preclude the presence or addition of one or more other features, integers, steps, operations, elements, components, and/or groups thereof. As used herein, the term "and/or" includes any and all combinations of one or more of the associated listed items. As used herein, phrases such as "between X and Y" and "between about X and Y" should be interpreted to include X and Y. As used herein, phrases such as "between about X and Y" mean "between about X and about Y." As used herein, phrases such as "from about X to Y" mean "from about X to about Y."

[0016] It will be understood that when an element is referred to as being "on",

"attached" to, "connected" to, "coupled" with, "contacting", etc., another element, it can be directly on, attached to, connected to, coupled with or contacting the other element or intervening elements may also be present. In contrast, when an element is referred to as being, for example, "directly on", "directly attached" to, "directly connected" to, "directly coupled" with or "directly contacting" another element, there are no intervening elements present. It will also be appreciated by those of skill in the art that references to a structure or feature that is disposed "adjacent" another feature may have portions that overlap or underlie the adjacent feature.

[0017] Spatially relative terms, such as "under", "below", "lower", "over", "upper", "lateral", "left", "right" and the like, may be used herein for ease of description to describe one element or feature's relationship to another element(s) or feature(s) as illustrated in the figures. It will be understood that the spatially relative terms are intended to encompass different orientations of the device in use or operation in addition to the orientation depicted in the figures. For example, if the device in the figures is inverted, elements described as "under" or "beneath" other elements or features would then be oriented "over" the other elements or features. The device may be otherwise oriented (rotated 90 degrees or at other orientations) and the descriptors of relative spatial relationships used herein interpreted accordingly.

[0018] Figure 1 illustrates an enclosure 10 having a first wall 12, a second, opposite wall 14 and an interior 16. The first wall 12 has a door 18 with a louvered vent opening 20, and the second wall 14 includes a fan opening 22. The enclosure 10 may be constructed from any suitable material including sheet metal, wood or masonry, and is generally designed to be located outdoors and to protect equipment housed therein from the elements and to limit access to the interior 16 to authorized personnel.

[0019] The enclosure 10 houses various types of telecommunications equipment such as the plurality of telecommunications modules 24 shown mounted in a rack 26. Such telecommunications equipment generally must be maintained within given temperature and humidity ranges to operate properly. Thus, when the enclosure 10 is located in a region where the ambient temperature is sometimes below the operating temperature range for the telecommunications modules 24, a heater 28 must be provided. Similarly, when the ambient temperature is sometimes above the operating temperature range for the telecommunications modules 24, an air conditioner 30 or other cooling device must be provided to cool the interior 16. The fact that the telecommunications modules 24 produce significant amounts of heat when they operate may also require the operation of the air conditioner 30 even when the ambient temperature outside the enclosure 10 is within the operating range of the telecommunications equipment. As used herein, "air conditioner" is intended to include conventional devices for cooling the interior of an enclosure such as expansion/compression cycle air conditioners and heat pumps, cold water based chiller systems and thermoelectric cooling devices, for example, systems based on Peltier elements. When the air conditioner 30 comprises a heat pump, a separate heater 28 is not required. The air conditioner controller 31 controls the air conditioner 30 and the heater 28 when present.

[0020] The enclosure 10 also includes a battery compartment 32 as a subportion of the housing 10 for housing a plurality of batteries 34 which are used for operating the telecommunications modules 24 when a primary source of power is not available. It is often desirable to maintain the batteries 34 at a temperature lower that the maximum operating temperature of the telecommunications modules 24 in order to prolong their useful life. The battery compartment 32 may thus be provided with a separate cooling device such as a thermoelectric cooler 36 and associated controller 38 to separately control the temperature of the battery compartment 32.

[0021 ] Enclosures housing heating and cooling devices and telecommunications equipment are conventionally known. In such systems, a temperature sensor monitors the temperature of the interior of the enclosure, and a controller controls the heater and air conditioner to maintain the temperature of the interior within a desired temperature range. However, the heating and cooling systems consume a significant amount of power, and reducing this power consumption can reduce the overall operating cost for the enclosure. The present embodiment therefore also includes a fan 40 mounted in the fan opening 22 in communication with a fan controller 42 (a single fan is described for simplicity; however, multiple fans could be used). Suitable filters, including a hydrophobic filter

41 for keeping water out of interior 16 and a particulate filter 43 for minimizing the entry of particulate matter into the interior 16, are also provided. The fan controller

42 is operably connected to an interior temperature sensor 44 for detecting the temperature of the interior 16 of the enclosure 10, an ambient temperature sensor 46 for determining a temperature of the air outside the enclosure 10 and a humidity sensor 48 for determining a humidity level of the air outside the enclosure 10. In the following discussion, separate controllers for the cooling device 36, air conditioner 30 and fan 40 are described. However, it is possible for a single controller to control some or all of these components, especially when the air conditioner 30 and fan 40 are installed in the enclosure 10 at the same time, during the original construction of the enclosure 10, for example. Separate controllers, especially a separate fan controller 42, may be useful in the case of a retrofit when the fan 40 is added to an existing, air conditioned enclosure. This is because, as described herein, the fan controller 42 only needs to determine the temperature of the interior 16 at the time that the air conditioner 30 shuts off - the fan controller 42 does not need to be integrated into or otherwise communicate with an existing air conditioner controller and does not require information regarding the temperature settings of the air conditioner controller 31 .

[0022] The air conditioner 30 has first and second operating states. In the first state, the air conditioner 30 cools the interior 16 of the enclosure 10, and in the second state, the air conditioner 30 does not cool the interior 16. The first state will generally correspond to the air conditioner being on and the second state to the air conditioner being off. However, it is possible that the air conditioner 30 may continue to run under some conditions without cooling the interior 16, when dampers or other structures (not illustrated) divert cool air from the air conditioner 30 to other locations, for example. Likewise, the fan 40 has a first operating condition under which it draws air into the interior 16 and a second operating condition under which it does not draw air into the interior 16. The first condition will generally correspond to the fan 40 being on and the second condition to the fan 40 being off. However, like the air conditioner 30, the fan 40 may continue to operate when dampers or other structures (not illustrated) prevent air from the fan 40 from entering the interior 16. The air conditioner 30 and fan 40 are therefore described as having states and conditions rather than being "on" or "off to cover such situations where the fan 40 and/or air conditioner 30 continue to run but do not draw air into and/or cool interior 16.

[0023] In operation, the interior temperature sensor 44, ambient temperature sensor 46 and exterior humidity sensor 48 provide signals to the fan controller 46 that are indicative of the temperatures and humidity levels detected. The fan controller 42 also includes an input for receiving a signal that indicates whether the air conditioner 30 is in the first state or the second state. This signal may be generated by the air conditioner controller 31 and sent to the fan controller 42 on line 50 or wirelessly via antenna 52 in fully integrated systems as illustrated in Figure 2. Alternately, a signal may be generated by detecting a control signal sent from the air conditioner controller 31 to the air conditioner 30 as illustrated in Figure 3 using a line 54 connected to the fan controller 42. In another arrangement, illustrated in Figure 4, a mechanical switch 56 is provided that is physically moved by a portion of the air conditioner 30 that moves between first and second positions when the air conditioner 30 shifts between the first and second states, a flap 58 as illustrated in Figure 4, for example. Switch 56 may be connected to the fan controller 42 by a line 60 or wirelessly via an antenna 62. Figure 5 illustrates an alternate switch 64 that is actuated by the airflow 66 from the air conditioner 30 and that sends a signal to the fan controller 42 either via line 68 or wirelessly via antenna 70 when air from the air conditioner 30 blows against the switch 64. Figure 6 illustrates a vibration sensor 72 mounted on the air conditioner 30 that determines the operating state of the air conditioner 30 based on the presence or absence of vibrations and which sends a signal to the fan controller 42 regarding the detected state via line 74 or wirelessly via antenna 76.

[0024] The air conditioner controller 31 can be set to shift to the first operating state at a first temperature and to shift to the second operating state at a second temperature less than the first temperature, which second temperature may also be determined by a user. It will be assumed that the air conditioner controller 31 is set to shift air conditioner 30 from the second operating state to the first operating state when the temperature in the interior 16 reaches 27 °C and to switch the air conditioner 30 to the second operating state when the temperature in the interior 16 falls to 25 °C. The fan controller 42 will not place the fan 40 in the first operating condition if the air conditioner 30 or the heater 28 is running. The fan 40 also will not operate if the ambient humidity detected by the ambient humidity sensor 48 is greater than a predetermined amount. That is, even if the ambient air is cool enough to provide useful cooling for the telecommunications modules 24 in the interior 16, high humidity could damage the telecommunications modules 24, and under such conditions, the air conditioner 30 is relied upon for all cooling needs.

[0025] When the fan controller 42 determines that the air conditioner has shifted to the second operating state, the fan controller 42 sets a temperature detected at that time by the temperature sensor 44 as an upper operating temperature (UOT). The fan controller 42 also determines the ambient temperature using input from ambient temperature sensor 46. If the ambient temperature is less than the UOT, the fan controller 42 shifts fan 40 from the second operating condition to the first operating condition. The fan controller 42 is configured with a first temperature offset (TO) to determine the temperature range in which the fan 40 will operate in the first operating condition. The first temperature offset will be assumed to be 2 °C for purposes of discussion, it being understood that a greater or lesser offset could be set in the fan controller 42. The fan controller 42 monitors the temperature of the interior 16 and shifts the fan 40 to the second operating condition if the temperature of the interior becomes less than the UOT by the amount of this temperature offset - in the present example, if the temperature of the interior falls from 25 °C to 23 °C. Alternately, if the temperature of the interior 16 rises to 27 °C (or other temperature set in the air conditioner controller 31 ), the air conditioner controller 31 will shift the air conditioner 30 from the second operating state to the first operating state, and, upon detecting this change of operating state of the air conditioner 30, the fan controller 42 will shift the fan 40 back to the second operating condition.

[0026] In this manner, fan controller 42 uses cool ambient air to cool the telecommunications modules 24 at times when the ambient air is cooler than the temperature of the interior 16. For example, at the end of the day, as the ambient temperature drops, a point may be reached at which the ambient temperature is 22 °C while the unconditioned temperature of the interior 16 is higher either due to residual heat radiated from the material of the enclosure 10 or due to the heat produced by the operation of the telecommunications modules 24. Under such conditions, fan 42 provides economical cooling without operating the air conditioner 30. Should the ambient temperature continue to fall, as night approaches and as the amount of cellular traffic falls after business hours, the fan 40 will continue to operate until the temperature of the interior is less than or equal to 23 °C at which time the fan 40 will shift to the second operating condition for the night.

[0027] In the morning, as the ambient temperature climbs and cell phone use

(and thus heat produced by telecommunications equipment 24) increases, the fan controller 42 will shift the fan 40 back into the first operating condition and maintain the fan 40 in this operating condition until the temperature of the interior reaches 27 °C at which time the air conditioner controller 31 shifts the air conditioner 30 into the first state and the fan controller 42 shifts the fan 40 to the second condition.

[0028] In another embodiment, the fan controller 42 operates the fan 40 at different rates depending on the difference between the UOT and the temperature of the interior 16. In this embodiment, the fan controller 42 is programmed with a second temperature offset that is less than the first temperature offset; in this example, the second temperature offset is 1 °C. When the temperature of the interior 16 is between the UOT and 24 °C, the fan 40 operates at full speed - at 100% pulse width modulation (PWM), for example. However, when the temperature of the interior 16 decreases by the amount of the second temperature offset, when it reaches 24 °C in this example, the speed of the fan 40 is reduced, to 80% PWM, for example. The fan controller 42 continues to monitor the interior temperature and decreases the PWM of the fan 40 by an additional 20% each time a temperature reading is taken, every 30 seconds, for example, until the temperature falls to 23 °C (the first temperature offset below the UOT) at which time the fan 40 is shifted to the second operating condition. This arrangement reduces the temperature overshoot that could occur if the fan 40 continues to operate at full power as the fan shut-off temperature is approached, especially in environments where the ambient temperature drops quickly at sunset. However, even if there is a significant temperature differential between the outside temperature and the inside temperature, the fan controller 42 will still run the fan 40 for at least 30 seconds before taking a temperature reading, and, if appropriate, shift the fan 40 to the second operating condition.

[0029] When the ambient temperature increases, the fan controller 42 starts the fan 40 operating at 20% PWM and increase the speed of the fan 40 in 20% PWM steps until the second temperature offset is reached, 24 °C in this example, at which point the fan controller 42 operates the fan 40 at full speed until the air conditioner controller 31 shifts the air conditioner 30 to the first operating state - at 27 °C in this example. This arrangement also avoids providing too great a degree of cooling - for example, when the ambient temperature is still significantly below the operating range for the telecommunications equipment 24 but when the heat produced by the operation of the telecommunications equipment begins to drive the temperature of the interior 16 above 23 °C. As the day warms up and the heat load in the enclosure 10 increases due to the rush hour cell station use, the air conditioner 30 will take over the main cooling task for the enclosure 10.

[0030] As previously noted, the fan controller 42 receives signals from the ambient humidity sensor 48. If at any time the ambient humidity exceeds a predetermined level, the fan controller 42 will shift the fan 40 to the second operating condition, and all cooling of the enclosure 10 will be provided by the air conditioner 30. Throughout all such operations, the controller 38 for cooling device 36 cools the batteries 34 in battery compartment 32 as necessary to maintain a desired battery temperature essentially independently of the temperature of the interior 16.

[0031 ] Beneficially, the UOT is set by detecting a temperature at which the air conditioner 30 shifts to the second operating state. If one were to attempt to set the fan controller 42 based on the set points of the air conditioner controller 31 , errors in the air conditioner temperature settings and/or operation could adversely affect the benefits provided by the fan 40. For example, if the air conditioner controller 31 is set significantly higher than the fan temperature set point, it will take more time for the interior temperature to achieve the lower fan temperature set point. During this time, the fan controller 42 will not run the fan 40. On the other hand, if the a thermostat (not illustrated) of the air conditioner 30 is set lower than the fan temperature set point, this would reduce or eliminate the time that the fan 40 would run. These problems are avoided, and a more easily retrofittable system is produced, by controlling the fan 40 based on a measured interior temperature of the enclosure 10 and based on the operating state of the air conditioner 30.

[0032] Figure 7 illustrates a method that includes a step 100 of providing an air conditioner having a first state in which the air conditioner cools an interior of the enclosure and a second state in which the air conditioner does not cool the interior, a step 102 of providing a fan having a first condition in which the fan draws air into the interior and a second condition in which the fan does not draw air into the interior, a step 104 of providing at least one controller for controlling the air conditioner and the fan, and a step 106 of detecting a temperature of the interior of the enclosure. The method also includes a step 108 of placing the air conditioner in the first state and cooling the interior using the air conditioner when a temperature of the interior is greater than or equal to an on temperature and placing the air conditioner in the second state and ceasing to cool the interior using the air conditioner when the temperature of the interior is less than an off temperature, the off temperature being less than the on temperature by a predetermined number of degrees, a step 1 10 of determining an ambient temperature outside the enclosure and a step 1 12 of, based on the air conditioner shifting from the first state to the second state, if the ambient temperature is less than the off temperature, placing the fan in the first condition to draw air into the interior until the temperature of the interior is less than the off temperature by a first amount and, in response to the temperature of the interior becoming less than the off temperature by the first amount, placing the fan in the second condition.

[0033] Figure 8 illustrates another method that includes a step 120 of providing a fan having a first condition in which the fan draws air into the interior of an air conditioned enclosure at a first rate and a second condition in which the fan does not draw air into the interior, a step 122 of providing a fan controller for controlling the fan, a step 124 of determining a temperature of the interior of the enclosure, and a step 126 of determining an ambient temperature outside the enclosure. The method also includes a step 128 of, in response to the air conditioner shifting from a first state in which the air conditioner cools the interior to a second state in which the air conditioner does not cool the interior, providing the fan controller with a value indicative of the temperature of the interior and setting a fan set temperature in the fan controller based on the value, and a step 130 of, if the ambient temperature is less than the fan set temperature, placing the fan in the first condition to draw air into the interior until the temperature of the interior is less than the fan set temperature by a first amount and, in response to the temperature of the interior becoming less than the fan set temperature by the first amount, placing the fan in the second condition.

[0034] The present invention has been described herein in terms of several preferred embodiments. Various additions and modifications to these embodiments will become apparent to those of ordinary skill in the relevant art upon reading of the foregoing disclosure. It is intended that all such modifications form a part of the present invention to the extent they fall within the scope of the several claims appended hereto.