Abstract:
An environmental control system for a telecom shelter integrates with a native HVAC system for exchanging interior air in a conditioned space in a machine room, telecom enclosure, or other closed machine environment by forcing or directing cooler outside air to replace interior air without active refrigeration by the native HVAC system. Primary cooling and heating of the conditioned space in the enclosure is performed by an exchange system and control logic that identifies, based on sensory input, when outside air exchange is more efficient than native AC (Air Conditioner) operation. The native AC system is suppressed or inhibited, and primary environmental control performed by fan driven exchange of outside air with air in the enclosure. Sensors and timers identify appropriate periods to defer control to the native AC system for cooling demand in excess of outside air exchange capability, and also identify ongoing suppression, or “takeback” of cooling control from the native system when erroneous, erratic or mistaken operation results in excessive or insufficient cooling, resulting from such factors as equipment failure, operator error, and environmental/disaster occurrences.

Description:
RELATED APPLICATIONS 
       [0001]    This application claims the benefit under 35 U.S.C. §119(e) of U.S. Provisional Patent Application No. 62/081,727 filed Nov. 19, 2014, entitled “EQUIPMENT ROOM VENTILATION CONTROL,” and U.S. Provisional Patent Application No. 62/081,730 filed Nov. 19, 2014, entitled “MACHINE ROOM HVAC SUPERCESSION CONTROL,” both incorporated herein by reference in entirety. 
     
    
     BACKGROUND 
       [0002]    Electronic equipment generates heat as a by-product of electrical flow. As modern technology allows for more densely arranged elements such as memory and processors on circuit boards, the electrical consumption and corresponding generated heat increases. In a computer supported environment, electronic equipment such as computers, routers, switches and other telecommunications equipment is often stored in a “machine room” that has a separate ventilation, or HVAC (Heating, Ventilation and Air Conditioning) system than the rest of the building, office, or structure. However, modern proliferation of mobile devices requires controlled environment structures for on-site electronic switching and control equipment for telecommunications, such as machine rooms (telecom shelters) for housing switching equipment at cell phone towers, for example. Such machine rooms typically house a dense configuration of electronic equipment, since accommodation of human workers is generally not required except for occasional maintenance. HVAC demands of these small, specialized machine rooms are particularly specialized and intense due to the small conditioned space and significant heat generation capability of the equipment stored therein. 
       SUMMARY 
       [0003]    A supplemental cooling system for a telecommunications equipment enclosure manages cooling resources for electronic equipment by identifying a thermostatic control to a native cooling resource directed to the telecommunication equipment enclosure, and interfacing with the thermostatic control for superseding the thermostatic control to enable and disable the cooling resource according to air exchange logic. Air exchange logic performs selective disabling, based on an interior temperature of the equipment enclosure and an ambient temperature outside the equipment enclosure, of the native cooling resource in favor of ambient air exchange with the equipment enclosure. The air exchange logic then monitors the interior temperature for determining when to re-enable the native cooling resource. 
         [0004]    Upon disabling the native cooling resource, the air exchange logic sets an override timer, and evaluates, upon expiration of the override timer, continued suppression of the native cooling resource to determine if a transient or temporary condition has subsided. The air exchange logic determines whether the native cooling resource should be re-enabled to maintain adequate temperatures in the equipment enclosure, and if so, re-enables the native cooling resource. Such transient conditions include excessive compressor head pressure or frozen coils, for example, that if not mitigated as disclosed herein, could persist and exacerbate cooling problems or equipment overheating and failure. 
         [0005]    Upon re-enabling the native cooling resource to commence cooling operations, the air exchange logic sets a takeback timer for reevaluating continued performance of the native cooling resource, and subsequently disables, if a condition resulting in the previous disabling of the native cooling resource persists, the native cooling resource, since the previous inhibiting of the native control according to the override timer may have not cured the problem or malfunction. The air exchange logic then continues management of the interior temperature using the ambient air exchange for mitigating high temperatures as much as possible until a more thorough diagnostic is available. Such air exchange, however, nonetheless exhausts heat and may provide adequate cooling, depending on the outside ambient temperature, and is certainly an improvement over the heat buildup that would otherwise occur in the closed machine room. 
         [0006]    Configurations herein are based, in part, on the observation that controlled environment structures for electronic equipment often employ HVAC (heating/ventilation/air conditioning) equipment disproportionate to the air volume of an enclosure defined by the interior of the structure. These specialized installations are typically unattended and have HVAC systems sized for a worst-case scenario. Often, such an HVAC system has a capacity in excess of that required for sufficiently cooling the cubic foot volume of the enclosure. Unfortunately, conventional approaches to machine enclosure cooling suffer from the shortcoming that the native HVAC system cannot be effectively scaled based on demand, resulting in excessive cooling of the equipment enclosure. Therefore, such native HVAC systems may be governed by control equipment that is inefficient or wasteful in providing appropriate cooling to the enclosure, and in extreme circumstances may result in overcooling and/or overheating of the enclosure, placing sensitive electronic equipment at risk of damage from excessive operating temperatures. 
         [0007]    Accordingly, configurations herein substantially overcome the above-described shortcomings by providing a system, method and apparatus for invoking an external air exchange with a conditioned space in the enclosure when doing so provides more efficient environmental and temperature controls for keeping the interior at an acceptable temperature. An override and takeback setting actively manage and control the native HVAC system to correct short term problems or anomalies and prevent ongoing inefficient operation using a takeback interval that assesses remedial measures for effectiveness. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0008]    The foregoing and other objects, features and advantages of the invention will be apparent from the following description of particular embodiments of the invention, as illustrated in the accompanying drawings in which like reference characters refer to the same parts throughout the different views. The drawings are not necessarily to scale, emphasis instead being placed upon illustrating the principles of the invention. 
           [0009]      FIG. 1  is a context diagram of a telecommunications environment suitable for use with configurations disclosed herein; 
           [0010]      FIG. 2  is a plan view of an equipment enclosure in the environment of  FIG. 1 ; 
           [0011]      FIG. 3  is a block diagram of a configuration in an equipment enclosure as in  FIG. 2 ; and 
           [0012]      FIGS. 4A and 4B  are a flowchart of operation of a management circuit and application in the equipment enclosure of  FIG. 3 . 
       
    
    
     DETAILED DESCRIPTION 
       [0013]    Electronics equipment for telecommunications is often located at a transmission point defined by an antenna, cell tower, or an intermediate routing location. Small, specialized enclosures or machine rooms provide a protective, temperature controlled environment that is vital to continued operation of the equipment. Since such enclosures may be remote, and only periodically monitored by an on-site technician, a native control system for providing HVAC support is intended to provide autonomous operation. Further, due to the size and number of equipment enclosures, rigorous attention to HVAC systems serving individual enclosures presents a logistical challenge. Additionally, such shelters are built according to standard configurations that must account for worst case conditions including heat load, geography, condition of the HVAC (age degradation) and solar gain based on time of day and year and local shade casting elements such as buildings, trees, etc., that typically do not apply equally to all shelters. Accordingly, inefficient or underperforming installations may elude detection until outright failure, placing the equipment therein at risk. Configurations below provide a supplemental management and oversight approach that increases efficiency and longevity of the native control HVAC system, alerts as to functional deficiencies, and mitigates cooling shortfalls in the event of failure. 
         [0014]    Environmental control of telecommunications (telecoms) enclosures benefits from the observation that substantial equipment cooling may often be achieved by ventilating with ambient air for replacing heated machine room air through a system of fans and louvers. One such approach is outlined in U.S. Pat. No. 8,770,493, filed Oct. 10, 2012, entitled “TELECOM SHELTER COOLING AND CONTROL SYSTEM.” While not always applicable as an exclusive cooling approach, strategic use of ambient air exchange reduces the usage time and power cycles imposed on the native control. In the approaches discussed further below, supplemental air exchange is performed in conjunction with sensor based diagnostic and monitoring of the enclosure for overriding the native control in favor of ambient air exchange, and selectively inhibiting and enabling operation of the native control. In conjunction with air exchange logic for interpreting sensor data such as temperature and humidity, the native control is monitored in a supervisory capacity within certain predetermined limits of temperature and/or humidity. Intervention in response to detected inefficiency or operational problems disables the native control for mitigating a temporary malfunction or anomaly. The air exchange logic re-enables the native control, subject to a takeback of control if the detected inefficiency or malfunction persists. 
         [0015]    In a typical operating scenario according to configurations herein, a controller having air exchange logic disables, based on an interior temperature of the equipment enclosure and an ambient temperature outside the equipment enclosure, the native cooling resource in favor of ambient air exchange with the equipment enclosure, and monitors the interior temperature for determining when to re-enable the native cooling resource. Upon disabling the native cooling resource, the air exchange logic sets the override timer and re-enables the native cooling resource. Suspending operation of the native control includes interfacing with a thermostatic circuit for overriding a thermostatic switch to disable the native control as described further below. 
         [0016]    Following expiration of the override timer, the air exchange logic may conclude that the native control is capable of again maintaining the temperature within the predetermined limits, and re-enables the native control subject to a takeback timer. Upon expiration of the takeback timer, the air exchange logic again disables, if a condition resulting in the previous disabling of the native cooling resource persists, the native cooling resource. 
         [0017]    The examples below depict several configurations, typically for cooling as equipment heat generation is a paramount concern, and provide a method and apparatus for implementing the proposed approach. Alternate arrangements of HVAC control, such as additional environmental sensors and circuits for interfacing with the native control, could be implemented according to the principles herein. 
         [0018]      FIG. 1  is a context diagram of a telecommunications environment suitable for use with configurations disclosed herein. Referring to  FIG. 1 , in a telecommunications environment  100 , an enclosure  110  houses a machine room  112  for storing and operating communications equipment  120 , such as switching and routing equipment, power supplies, antenna amplifiers, and associated computers and processing devices. A HVAC system  130  provides the native control and includes an evaporator  132  and fan  133  for blowing cooled air, a compressor  136 , a condenser  134  outside the enclosure, and a thermostat  138  or other control for switching the compressor  136  and other HVAC components. The cooling operation of the HVAC system  130  is generally the most used, to offset the high heat given off by the equipment  120 . 
         [0019]    A controller  150  in the enclosure  110  includes air exchange logic  152  ( FIG. 2 ) in the form of a circuit and/or application, and operates the intake fan  154  and controls the HVAC system  130  via an interface  160  to the thermostat  138  for providing thermostatic control over the HVAC system  130 . An intake vent  156  and output vent  158  isolate the machine room  112  when the intake fan  154  is idle, such as by louvers, gates, panels or other automated closures. 
         [0020]    A telecommunications tower  170 , such as a cell tower or TV/radio transmission beacon is responsive to the equipment  120  for throughput support, and AC lines  172  provide electrical power. A local antenna  174  provides Internet connectivity for the controller via WiFi or 4GL wireless links under IEEE 802.11 connectivity; alternatively a hardwired Ethernet cable or other Internet LAN may also be provided alternatively, form C contacts may be employed for communicating alarms and status. 
         [0021]      FIG. 2  is a plan view of an equipment enclosure in the environment of  FIG. 1 . Referring to  FIGS. 1 and 2 , an example machine room includes a native control HVAC system  130  having a single compressor  136  and thermostat  138 . The controller  150  connects to the thermostat  138  via the interface  160 , and also connects to temperature sensors (such as thermistors)  151 - 1  and  151 - 2 , for sensing interior temperature in the enclosure  110 , and  151 - 3  ( 151  generally) for sensing ambient temperature outside the enclosure  110 . Note that outside air thermistor  151 - 3  may be disposed at the intake vent  156  to avoid running exterior wires through the enclosure  110  wall, and is coordinated with opening of the vent, discussed below. 
         [0022]    Intake vent  156  and output vent  158  are also responsive to the controller  150 , and coordinate with the intake fan  154  for exchanging ambient air. Alternatively, the intake fan  154  could be mounted as an exhaust fan, as long as an airflow path for ambient air is provided. Air exchange logic  152  in the controller  150  receives input from the thermistors  151  and the thermostat  138  for computing a current state and need for ambient exchange and control of the compressor  136  (native control), as discussed further below. Actuators  180  responsive to the controller  150  open and close the vents  156 ,  158 . 
         [0023]      FIG. 3  is a block diagram of a configuration in an equipment enclosure as in  FIG. 2 . Referring to  FIGS. 2 and 3 , enclosures  110  vary in size and may take the form of a small cabinet up to human accessible rooms having rows of equipment. A typical communications equipment enclosure or shelter is disposed at the base of the tower or antennas it supports, and is large enough to accommodate one or  2  technicians for limited access to the equipment therein. Depending on the size, and therefore the cooling demand, multiple compressors  136 -N may be used for redundancy and/or increased thermal response. The multiple compressors  156 -N may have an integrated native control, or may operate separately at different ranges of temperature to implement a “phase in” as demand increases. It is, however, often desirable to commonly manage multiple cooling resources for load sharing to prevent unbalanced usage, and thus wear, on the compressor, such as a compressor with a lower turn-on temperature set point that is always to be invoked first. 
         [0024]    For example, the native control  130  may include a plurality of independently switchable compressors  136 , and suspending operation includes identifying a power cycle count and an elapsed time count for each of the plurality of compressors, and alternating enablement of each compressor of the plurality of compressors  136  for achieving an even distribution of operational time and/or cycling. This ensures that switching and override of the native control  130  as described herein will not resort to always restarting the same compressor,  136 , resulting in an uneven load, but will instead distribute the burden evenly. 
         [0025]    Continuing to refer to  FIG. 3 , the controller  150  is responsive to a management station  153 , such as a separate controller, laptop, PC or server having control software/firmware, data storage, and programs for receiving, analyzing, and responding to sensor data (thermistors, humidity sensors, switches, etc.) and control objects such as the compressors, fans, louvers and gates in the enclosure  112 . A GUI  155  (Graphical User Interface) provides an interactive operator with settings and controls for examining and updating system parameters such as temperature thresholds (set points) and timeouts that affect operation of the air exchange logic  152 . 
         [0026]    The controller  150  may be a server, integrated circuit, firmware or other suitable processing device for implementing the air exchange logic. The controller  150  includes an override timer  182  and a takeback timer  184  for implementing the respective intervals for inhibiting and enabling the compressors  136 . The timers  182 ,  184  may be implemented as hardware or software registers, firmware values or other suitable implementation. 
         [0027]    Each compressor  136 - 1  . . .  136 -N ( 136  generally) has one or more thermostats  138 - 1  . . .  138 -N for sensing temperatures in the machine room  112 , and interfaces with the controller  150  via the interface  160  and feedback indicator  161 . In the example configuration, the interface  160  opens and closes a thermostat circuit to which the compressor  136  responds, although other mechanisms for enabling and inhibiting (suppressing) compressor operation may be invoked. The feedback indicator  161  indicates when each compressor  138 -N is commanded to an “on” state by the native control, and is used to track power cycles and uptime. 
         [0028]    In certain configurations, the machine room  112  employs a plurality of temperature sensors (such as thermistors)  151  for each installation or controller  150 . Placement and readings from the sensors  152  include invoking the ambient air circulation fan  154  for obtaining a true reading from an ambient air temperature sensor disposed adjacent to the ambient air circulation fan  154 , to provide a true reading without requiring exterior mounting. The air exchange logic  152  then employs a lowest reading from among each sensor  151  of a plurality of interior temperature sensors for initiating the ambient air circulation for cooling the enclosure, based on a sensed ambient temperature and a sensed enclosure temperature obtained from the plurality of sensors, and employs a highest reading from among each sensor of a plurality of interior sensors for halting the ambient air circulation, for ensuring an inaccurate sensor reading is ignored. Strategic placement of sensors  151  to cover range variations in temperature assures that an accurate reading of environmental conditions in the enclosure  110  is computed by the air exchange logic  152 . 
         [0029]    Sensor information such as temperature, humidity and airflow therefore derives from the temperature or other sensors placed in the conditioned space and outside of the enclosure to determine a delta or difference to help identify expected changes in the conditioned space will result from exchange with the outside air. Placement of exterior sensors is sensitive to solar load and shifting with shadows due to solar movement, wind, and snow/icing conditions, which can vary based on exterior exposure to sun and wind. 
         [0030]    In an example arrangement, sensor or thermistor  151  readings for determining adequate temperatures are defined by a range between a maximum set point and a minimum set point, and monitoring includes a measurement of an interior temperature inside the machine room, a measurement of exterior temperature of ambient air outside the machine room  112 , and a correction interval such as the override timer for permitting the native control to remain idle. 
         [0031]    In the example configuration identifying the power cycle and elapsed time includes interfacing with the thermostatic circuit for determining enablement of the compressors, and receiving a rectified signal over a single conductor from a plurality of thermostatic switches for identifying which thermostatic circuits are enabling the respective compressors. A single conductor and signal may be employed by connecting a rectifier  165 - 1  . . .  165 -N to an energized conductor from the thermostat  138 , and varying the rectification (half wave, quarter wave, etc.) for each compressor  136 . In a typical installation, the native HVAC system (native control)  130  operates on a 24VAC thermostatic circuit. Identifying the power cycle and elapsed time includes interfacing with a thermostatic circuit for determining enablement of the compressors, as the thermostat  138  return line will only register 24VAC when energized. Rectifiers  165  connected between the thermostat  138  return line and the controller  150  receive a rectified signal over a single conductor from a plurality of thermostatic switches  138  for identifying which thermostatic circuits are enabling the respective compressors  136 . The rectified connection has a varying response based on the thermostatic circuit The rectified signals will aggregate such that multiple compressor “on” signals generate different wave forms depending on which compressors are powered on, and the controller  150  reads the individual, aggregate signal on the feedback indicator  161  to ascertain compressor operation. 
         [0032]    The intake vent  156  and exhaust (output) vent  158  may be louvers, gates, or closures responsive to the controller  150 . Each of the vents  156 ,  158  should remain closed when ambient air exchange is not occurring, to avoid loss of cooled air and for conformance with fire suppression regulations. Multiple vents may be employed. In a particular configuration, the vents  156 ,  158  have a counterbalanced panel closure such as that disclosed in co-pending U.S. patent application Ser. No. 14/______,______ , incorporated herein by reference. 
         [0033]    Temperature sensors  151 - 1  . . .  151 -N may be for sensing interior or exterior temperature, and may vary in number to account for so-called “hot spots” which offer skewed or erratic readings. For example, an exterior thermistor in direct sunlight will tend to read a higher than actual temperature. Similarly, an interior thermistor closer to the path of cooled air may give an artificially reduced reading then the machine room  112  as a whole. 
         [0034]    Accordingly, the air exchange logic  152  employs a plurality of thermistors  151  (or other temperature sensing device) for each compressor  136  in the native control  130 . The air exchange logic  151  may invoke the ambient air circulation fan  133  for obtaining a true reading from an ambient air thermistor disposed adjacent to the ambient air circulation fan  133 , as thermistor  151  placement adjacent to (or within) the intake vent  156  avoids wiring outside of the enclosure  110  for external thermistors. 
         [0035]    Such placement may be, for example, inside the fan tray of the intake fan, which is beneficial for at least 2 reasons: 1) Accuracy of measurement. The outside air temp thermistor can influenced by solar loading and radiated heat (off the building, door &amp;/or adjacent equipment) so it can be moved inside the fan tray to minimize these influences; and 2) Ease of installation. The outside air temperature sensor can now be factory installed and it is no longer necessary to drill holes in the shelter to place it, or to be concerned with inconsistent placement by different installers. 
         [0036]    When multiple temperature sensors are used, the air exchange logic may employ a lowest reading from among each sensor of a plurality of interior sensors for initiating the ambient air circulation for cooling the enclosure. Similarly, it may employ the highest reading from among each sensor of a plurality of interior sensors for halting the ambient air circulation, for ensuring an inaccurate sensor reading is ignored. Similar placement considerations and reading applies to the exterior temperature readings. 
         [0037]      FIG. 4  is a flowchart of operation of a management circuit and application in the equipment enclosure of  FIG. 3 . Referring to  FIGS. 3 and 4 , the disclosed method of managing cooling resources or a compressor  136  for cooling electronic equipment  120  includes identifying a thermostatic control  138  to a native cooling resource, such as a compressor  136 , directed to a telecommunication equipment enclosure  110 , and interfacing with the thermostatic control  138  for superseding the thermostatic control  138  to enable and disable the cooling resource according to air exchange logic  152 , as disclosed at step  200 . The thermostatic control  138  may be a conventional 24v on/off circuit, or may be part of a more elaborate demand computation. The air exchange logic  152  monitors the temperature in the machine room  112  for deviation from the predetermined limits, as depicted at step  201 . The predetermined limits include temperature, as measured by sensors (such as thermistors)  151 , and may also include other factors such as humidistats for humidity or any suitable environmental aspect. 
         [0038]    In a particular example, predetermined limits encompass temperature, and include identifying a high set point defining a temperature at which the native control is invoked for cooling the machine room, and identifying a low set point defining a temperature at which the native control is disabled. The high set point and low set point therefore identify a range of operation included in the predetermined limits for ambient air circulation in favor of native control. 
         [0039]    The air exchange logic  152  determines when the native control of the HVAC system  130  is operating outside of predetermined limits for temperature, as shown at step  202  and the air exchange logic  152  suspends operation of the native control in favor of ambient air circulation by exchanging outside air, as depicted at step  203 . If the native control is operating within the predetermined limits, control reverts to step  201  for continued monitoring. 
         [0040]    In particular configurations, concluding the capability of the native control further includes comparing the temperature of ambient air outside the machine room  112  with a maximum interior temperature, and determining that ambient air circulation provides insufficient cooling capacity, resulting in a switch over from ambient air circulation back over to the native control  130 . 
         [0041]    However, an improperly sized native control  130  may result in an overcooling situation. In such an instance, determining when the native control is outside the predetermined limits includes comparing the temperature of the machine room  112  resulting from the native control  130  to a minimum interior temperature, and determining a cooling effect from the native control is in excess of a need for maintaining the minimum interior temperature because of bringing the machine room  112  temperature down too quickly. 
         [0042]    The air exchange logic  152  sets an override timer  182  corresponding to a condition resulting in a deviant parameter associated with the operation outside of the predetermined limits of native control operation, as shown at step  204 . In response, the air exchange logic inhibits operation of the native control for the duration of the override timer  182 , as depicted at step  205 . The override timer  182  is set to allow temporary conditions such as excessive backpressure in the compressor  136  or coil freezing to abate, and in a typical scenario may be in the range of 3-30 minutes, although any suitable value may be used. Some fault conditions exacerbate from attempted continued operation, and require only an idle period of the native control for self-correction. Otherwise, in the absence of the inhibit mode disclosed herein, the fault condition would persist and compromise the equipment  120  or the ability to control the environment of the enclosure  110 . 
         [0043]    Using the example above, the air exchange logic  152  may identify a short cycling and overcooling condition in the enclosure based on a plurality of occurrences of operation outside of the predetermined limits for temperature. The air exchange logic  152  sets the override timer  182  based on a duration for allowing ambient air circulation to maintain the temperature in the enclosure  110  below a maximum set point without power cycling a compressor in the native control. The predetermined limits such as temperature also pertain to environmental conditions in the enclosure and the deviant parameter includes at least one of excessively cold or hot interior temperature, excessive humidity, airflow or excessive cycling of a refrigerant compressor of the native control. 
         [0044]    For example, the air exchange logic performs a hysteresis analysis of power cycles and elapsed time during each power cycle of the compressors, and may conclude that a short cycling pattern is causing operation outside of the predetermined limits by a disproportionate cooling effect from the elapsed time. The native AC unit may be oversized and is rapidly bringing down the temperature in a short time without proper dehumidification. In such an instance, the air exchange logic inhibits operation of the native control for extending a cycle time without significant deviation from the predetermined limits of temperature. This allows ambient air exchange until a temperature setpoint just short of an excessive level, thus resulting in longer cycle times. 
         [0045]    The air exchange logic  152  evaluates, upon expiration of the override timer  182 , continued suppression of the native cooling resource  130 , as depicted at step  206 . This includes determining, with the air exchange logic  152 , whether the native cooling resource  130  should be re-enabled to maintain adequate temperatures in the equipment enclosure  110 , as shown at step  207 . A check is performed, at step  208 , and the air exchange logic  152  re-enables the native control  130  upon expiration of the override timer  182  based on observed correction of the deviant parameter that resulted in operation outside the predetermined temperate range or other environmental conditions, as disclosed at step  209 . If the condition has not abated, ambient air management is used to mitigate excessive temperatures, as discussed below with respect to step  214 . 
         [0046]    Upon re-enabling the native cooling resource  130 , the air exchange logic  152  sets a takeback timer  184  for reevaluating continued performance of the native cooling resource  130 , as disclosed at step  210 . This includes setting the takeback timer  184  corresponding to a condition resulting in observed diminished performance, as depicted at step  211 . Conditions resulting in diminished performance and/or deviant parameters include excessive cooling causing increased humidity, such as a short interval of cooling that drops the temperature but fails to condense moisture from the air. The air exchange logic  152  permits operation of the native control for the duration of the takeback timer  184  to ascertain if the condition causing the diminished performance has abated, as depicted at step  213 . 
         [0047]    A check is performed, at step  213 , to identify if the condition has abated and if the system is again operating within normal parameters. If so, control reverts to step  201  for continued monitoring in a supervisor state, in which the air exchange logic  152  monitors but does not intervene in native control  130  operation. 
         [0048]    If the check at step  213  did not indicate correction, then the air exchange logic  152  re-inhibits the native control  130  at the expiration of the takeback timer  184  if the condition persists as depicted at step  214 , and continues management of the interior temperature using the ambient air exchange for preventing hardware overhearing, as disclosed at step  215 . Ambient air exchange can effectively provide sufficient cooling depending on the differential between ambient (outside) air and the machine room  112  temperature resulting from equipment generated heat. Various alarms and notifications are also generated to alert monitoring personnel or equipment, and continued increased heat may result in equipment  120  shutdown to prevent damage. 
         [0049]    Several example use cases of operational scenarios are as follows. When the fans are running, the outside air stream temperature can be sampled continuously. When the fans aren&#39;t running [such as when the HVACs are running or when the air temperature inside is below either a. an air conditioner maximum cooling threshold (the low end of the control range where the HVACs are re-inhibited) or b. the air conditioner On temperature threshold] the outside air is sampled periodically by running the fans for a brief period (long enough to allow the temperature sensor to respond and settle at a temperature reading that more accurately reflects the outside air temperature). Samples are also taken when mode changes occur (such as switching to/from Aircon mode or Aircon Too Cool mode or Direct Air mode). A “freshness” metric avoids unnecessary sampling if the last sample was taken recently enough to be valid for control purposes. Logic to suspend sampling when the inside air temp drops below the fan On temp threshold is also implemented. In this way, he inside temperature will not be driven even lower by sampling outside air periodically when outside air temperatures are low (recall that the fans turn on at low speed when sampling and that could drop inside the inside temperature if it is really cold outside and the heat load inside is too low to warm the inflow of the cold air sufficiently). 
         [0050]    Alternate configurations of the invention include a multiprogramming or multiprocessing computerized device such as a multiprocessor, controller or dedicated computing device or the like configured with software and/or circuitry (e.g., a processor as summarized above) to process any or all of the method operations disclosed herein as embodiments of the invention. Still other embodiments of the invention include software programs such as a Java Virtual Machine and/or an operating system that can operate alone or in conjunction with each other with a multiprocessing computerized device to perform the method embodiment steps and operations summarized above and disclosed in detail below. One such embodiment comprises a computer program product that has a non-transitory computer-readable storage medium including computer program logic encoded as instructions thereon that, when performed in a multiprocessing computerized device having a coupling of a memory and a processor, programs the processor to perform the operations disclosed herein as embodiments of the invention to carry out data access requests. Such arrangements of the invention are typically provided as software, code and/or other data (e.g., data structures) arranged or encoded on a computer readable medium such as an optical medium (e.g., CD-ROM), floppy or hard disk, flash drive or other medium such as firmware or microcode in one or more ROM, RAM or PROM chips, field programmable gate arrays (FPGAs) or as an Application Specific Integrated Circuit (ASIC). The software or firmware or other such configurations can be installed onto the computerized device (e.g., during operating system execution or during environment installation) to cause the computerized device to perform the techniques explained herein as embodiments of the invention. 
         [0051]    While the system and methods defined herein have been particularly shown and described with references to embodiments thereof, it will be understood by those skilled in the art that various changes in form and details may be made therein without departing from the scope of the invention encompassed by the appended claims.