Abstract:
An HVAC controller for an equipment enclosure or machine room employs ambient air exchange and compressor driven cooling appliances for maintaining an operating temperature of a telecommunications machine room within acceptable levels. Coordinated engagement of the ambient air exchange and a plurality of lead/lag cooling appliances provides staged engagement of the cooling appliances to correspond to a cooling demand. Designation of lead and lag cooling appliances is alternated according to a designation interval to avoid disproportionate use of individual cooling appliances for promoting longevity. Multiple cooling appliances alternate the lead/lag designation to equalize equipment wear, and alternation of the lead/lag designation follows an normal operational satisfaction of the cooling demand, to minimize a frequency of equipment engagement (power up) cycles which contribute to wear.

Description:
RELATED APPLICATIONS 
       [0001]    This application claims the benefit under 35 U.S.C. §119(e) of U.S. Provisional Patent Application No. 62/200,857 filed Aug. 4, 2015, entitled “OPTIMIZED LEAD-LAG HVAC CONTROLLER FOR EQUIPMENT,” incorporated herein by reference in entirety. 
     
    
     BACKGROUND 
       [0002]    Computing resources are widely distributed throughout the telecommunications industry. Proliferation of personal electronic devices continues to increase the need for both wireless and wired network connectivity. Modern network deployment requires connectivity hardware, such as cell towers and antennas, in addition to more substantial data centers, to be located throughout a region supported by the network. Each of these locations requires an environmentally controlled enclosure to operate effectively. Further, since the equipment enclosures are typically unstaffed, reliability and longevity of cooling appliances and other HVAC (Heating, Ventilation and Air Conditioning) apparatus is paramount. 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]    An HVAC controller for an equipment enclosure or machine room employs ambient air exchange and compressor driven cooling appliances for maintaining an operating temperature of a telecommunications machine room within acceptable levels. Coordinated engagement of the ambient air exchange and a plurality of lead/lag cooling appliances provides staged engagement of the cooling appliances to correspond to a cooling demand. Designation of lead and lag cooling appliances is alternated according to a designation interval to avoid disproportionate use of individual cooling appliances for promoting longevity. Multiple cooling appliances alternate the lead/lag designation to equalize equipment wear, and alternation of the lead/lag designation follows a normal operational satisfaction of the cooling demand, to minimize a frequency of equipment engagement (power up) cycles which contribute to wear. 
         [0004]    Configurations herein are based, in part, on the observation that machine room HVAC controls often rely on analog sensed thermostatic switched control, which simply cycles cooling appliances on and off without any moderation or phased/gradual engagement based on future demands, usage inferences or usage mitigation. Unfortunately, such conventional approaches suffer from the shortcomings of overcooling, excessive cycling leading to degraded equipment lifespan, and wide temperature fluctuations in the environmentally conditioned space. Further, conventional approaches provide no coordination between multiple cooling appliances for leveling usage patterns and ensuring coordinated usage. Typically, separate conventional thermostatic controls are employed which simply burdens the lower set thermostat unit with the bulk of the cooling demand. Accordingly, configurations herein substantially overcome the above described shortcomings by common control of a plurality of cooling appliances in a lead/lag manner coupled with ambient air exchange when conditions dictate. Lead and lag designations alternate to coordinate the engagement of each of the cooling appliances and ensure balanced uptime, promoting longevity and mitigating uneven wear. Lead cooling appliances energize first, followed by lag cooling appliances as needed to maintain the operational temperature, and the designations alternated following a designation period so that the lag cooling appliance becomes the lead cooling appliance in the next designation interval. Larger installations having more cooling appliances rotate the lead appliance and each of the lag appliances in a prioritized manner to ensure equal uptime. 
         [0005]    In a particular arrangement depicted below, an environmental control for an equipment enclosure having ambient air exchange and cooling appliances, in which each of the cooling appliances is operable for designation as a lead cooling appliance or a lag cooling appliance, a controller device for maintaining a temperature within the equipment enclosure is configured to commence operation of a lead cooling appliance when an operational temperature inside the equipment enclosure exceeds a predetermined cooling engagement threshold, and commence operation of a lag cooling appliance based on an indication that additional cooling is needed to maintain the operational temperature. Following satisfaction of the additional cooling indication, the controller ceases operation of one of the lead cooling appliance and lag cooling appliance, and alternates the lead and lag designations of the cooling appliances in an iterative manner based on control logic for promoting longevity and minimizing cycles of the cooling appliance. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0006]    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. 
           [0007]      FIG. 1  is a context diagram of a telecommunications environment suitable for use with configurations disclosed herein; 
           [0008]      FIG. 2  is a plan view of an equipment enclosure in the environment of  FIG. 1 ; 
           [0009]      FIGS. 3 a -3 c    are a flowchart of controller device operation in the equipment enclosure of  FIG. 2 ; 
           [0010]      FIGS. 4 a -4 c    are GUI screens for management of the controller device of  FIGS. 1 and 2 . 
       
    
    
     DETAILED DESCRIPTION 
       [0011]    Depicted below is a particular configuration of the equipment enclosure and cooling appliances responsive to the controller. Particular cooling appliances are designated as lead or lag appliances, typically controlled by powering a compressor motor powering each cooling appliance. The lead and lag designations alternate, in a substantially equal manner to spread compressor “on” time among the different cooling appliances for promoting equal usage patterns. Multiple lag compressors likewise alternate, or iterate through a priority of the lag compressors and the lead (first priority) compressor. Compressors may also be designated as “lag only” if meant to provide only ancillary support, as opposed to primary cooling. 
         [0012]    The lead-lag descriptor is assigned to controllers that operate two or more HVAC systems simultaneously. The control scheme was developed to reduce wear and tear on HVAC units and to allow for staging of units in situations where one or all HVAC(s) has/(have) insufficient capacity to handle peak heat loads or has malfunctioned. 
         [0000]    The HVAC unit designated as “lead” is switched on first and the others designated as “lag” are then used as supplemental cooling as required. The disclosed lead-lag controller has the ability to manually switch the lead and lag designations as well as time based logic (hardwired or programmed) that swaps through the configured systems. This prevents any single HVAC unit having to bear the bulk of the cooling work and more evenly spreads the compressor on-off cycles amongst the available HVAC units, thereby extending the expected lifespan of all the units in the system. It is the cycling of the compressors that largely determines the effective life of HVAC units. 
         [0013]    There are several temperature thresholds or temperature differential thresholds that can be set to trigger the staging of the lag units. For example, if the room temperature is more than 6° F. above the set point, then the second stage is engaged. The second stage then shuts down when the temp gets to within 2° F. of the set point. 
         [0014]      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 equipment enclosure  110  takes the form of a machine room for telecommunications equipment. Telecommunications devices  112 - 1  . . .  112 - 3  ( 112  generally) such as switching and routing equipment includes various processor based computing devices for maintaining information and data throughput throughout a network supported by the telecommunications environment. Generally, it is expected that the telecommunications devices  112  connect to a public access network  118  for facilitating network throughput. Such telecommunications devices  112  generate substantial heat, due to the electronic nature of the devices. Accordingly, the equipment enclosure  110  should be environmentally controlled or the generated heat would quickly rise to unsafe and/or damaging levels. 
         [0015]    A plurality of cooling appliances  120 - 1  . . .  120 - 2  ( 120  generally) each include a compressor  124  driven by a motor  123 , an evaporator  125  driven by a fan  127  within the enclosure  110  for absorbing heat and a condenser  126  outside the enclosure for venting the heat. Coolant lines  128  circulate refrigerant fluid which changes phase between a liquid and a gas as it flows between the evaporator  125  and condenser  126  for exhausting the heat. A plurality of cooling appliances  120 , colloquially referred to as air conditioners, HVAC units, or simply AC, may be employed in the equipment enclosure  110  based on an expected cooling demand produced by the heat generated from the telecommunications devices  112 . Any suitable thermal based device may be employed for cooling, however in the example configuration the cooling appliances provide cooling by a phase change of a compressor driven fluid passed between the enclosure and outside air for performing heat transfer from the air inside the electronics enclosure. 
         [0016]    An ambient air exchanger  130  may also be invoked to exchange air in the equipment enclosure  110  when outside conditions permit, allowing interior air to exhaust through an exhaust vent  132  or damper. Ambient air exchange is discussed further in copending U.S. patent application Ser. No. 14/946,055, filed Nov. 19, 2015, entitled “VENTILATION CONTROL APPARATUS AND METHOD,” and U.S. patent application Ser. No. 14/946,182, filed Nov. 19, 2015, entitled “VENT CONTROL APPARATUS AND METHOD,” both incorporated herein by reference in entirety. 
         [0017]    A controller  150  includes control logic  152  for activating the cooling appliances  120  and ambient air exchanger  130  for efficiently maintaining an operating temperature in the equipment enclosure  110  in an optimal range. The controller  150  receives input from sensors  162 - 1  . . .  162 - 2 , which are configured to sense temperature, humidity and other environmental parameters. Each of the cooling appliances  120  and ambient air exchanger  130  is responsive to the controller  150  via interfaces  154 . The controller  150 , which may comprise a PC or similar computing unit and processor, includes connections or ports for the interfaces  154  and inputs from the sensors  162 . An operator interface including a GUI screen  156  and keyboard  158  or other input device (i.e. mouse, touchscreen, etc.) and communications device  159  such as a WiFi, 4GL or wired connection to an external network such as the Internet is also provided. 
         [0018]      FIG. 2  is a plan view of an equipment enclosure in the environment of  FIG. 1 . Referring to  FIGS. 1 and 2 , the controller  150  is configured to control a plurality of cooling appliances  120  or cooling/heating appliances, and is operable with equipment enclosures  110  of various sizes for housing a broad range of telecommunications devices  112 . Such enclosures  110  range in size from several square feet for a small closet enclosure to full machine rooms having raised floors, full height mounting racks and suitable for human occupancy. 
         [0019]    Conventional approaches to installation of multiple cooling appliances  120  often utilize separate thermostatic controls for each cooling appliance. Depending on the setting of each thermostat, this can cause one cooling appliance to engage more often, as the unit with the lowest thermostatic setting will detect a call for cooling first. A large discrepancy or other imbalances, such as warm or cold regions of the enclosure, can cause one appliance to bear most of the load with other cooling appliances to remain substantially dormant. This usage pattern causes the pattern of greater use to encounter greater maintenance costs and reduced lifespan. In contrast, the controller  150  is operable to commence a plurality of cooling appliances  120  responsive to the controller  150 , such that the cooling appliances  120  are designated as a lead cooling appliance and a prioritized sequence of lag cooling appliances. The controller iteratively assigns the lead/lag designations in a substantially equal apportionment among the lead and lag sequence. 
         [0020]    In a generalized configuration, in the equipment enclosure having ambient air exchange and cooling appliances and a controller for maintaining a temperature within the equipment enclosure, a plurality of cooling appliances  120 - 11  . . .  120 -N installed in the equipment enclosure  110  cool (or heat) the environment inside the enclosure to maintain a proper operating temperature. Multiple telecommunications or other devices  112 - 11  . . .  112 -N occupy the enclosure  110  and generate heat that defines a cooling load for the cooling appliances  120 . The controller  150  receives input from one or more sensors  162 - 11  . . .  162 -N for controlling the cooling appliances  120 . The sensors  162  may comprise thermistors, humidity sensors, smoke or other gaseous detection, and may be located inside or outside the enclosure  110 . 
         [0021]      FIGS. 3 a -3 c    are a flowchart of controller device operation in the equipment enclosure  110  of  FIG. 2 . The disclosed flowchart depicts one example of operation that may be pursued by the controller  150 , but is not intended to exhaustively cover all available operating scenarios that the controller  150  may address. Referring to  FIGS. 1-3   c , the controller is operable to evaluate the operational temperature from a plurality of thermistors in the equipment enclosure  110 , and commencing and ceasing based on a cooling demand determined based on a highest reading of each of the plurality of thermistors (sensors)  162 , as depicted at step  301 . A check is performed, at step  302 , to determine if the operating temperature in the equipment enclosure  110  is excessive. If the operating temperature is within acceptable limits, the controller  150  continues monitoring and maintaining the temperature, as depicted at step  303 . 
         [0022]    At step  304 , upon detecting a cooling demand based on the operational temperature inside the equipment enclosure exceeding a predetermined cooling engagement threshold, the controller  150  evaluates and/or engages an ambient air exchanger for an air exchange duration to determine if ambient air is sufficient to maintain the operational temperature. A check is performed, at step  305 , to identify when the ambient air exchange is deemed insufficient to maintain the operating temperature. When active cooling is called for, the controller  150  identifies or alternates the lead and lag designations of the cooling appliances based on control logic for promoting longevity and minimizing cycles of the cooling appliance, in which each of the cooling appliances is operable for designation as a lead cooling appliance or a lag cooling appliance, as depicted at step  306 . An initial determination of lead/lag cooling appliances is made, followed by redesignation of the lead and lag appliances as discussed further below. Alternately, the controller  150  is operable to identify a cooling appliance  120  for designation only as a lag cooling appliance  120  (step  307 ), as received from a GUI selection discussed below with respect to  FIGS. 4 a   - 4   c.    
         [0023]    The controller  150  commences operation of a lead cooling appliance when an operational temperature inside the equipment enclosure exceeds a predetermined cooling engagement threshold, as depicted at step  308 . A check is performed, at step  309 , to determine if the lead compressor has satisfied the cooling demand. If not, an exceeded 
         [0000]    supplemental cooling engagement threshold is indicative that a currently operating cooling appliance is insufficient to maintain the operating temperature below the cooling engagement threshold, as depicted at step  310 . The supplemental cooling threshold represents a differential from the cooling engagement threshold that is variable to allow assessment of cooling load satisfaction by the lead cooling appliance. In general, the indication that additional cooling is needed is based on a difference between the cooling engagement threshold and the supplemental cooling engagement threshold. Additional lag appliances may correspond to other differentials or absolute temperature settings. Therefore, the controller  150  is operable to operate the lag cooling appliance  120  based on whether the lead cooling appliance is also operating and on whether a cooling demand remains after an adjustment interval for allowing the lead appliance to satisfy the demand, as shown at step  311 . This is in contrast to conventional separate controls where compressors are switched on based only on a single thermostatic input without regard to the operational state of other compressors operating on the same enclosure. Therefore, the controller  150  commences operation of the lag cooling appliance  120  based on an indication that additional cooling is needed to maintain the operational temperature, as depicted at step  312 . 
         [0024]    A further check is performed, at step  323 , to determine if the operational temperature within acceptable range (following a reasonable delay to allow results of the engaged lag appliance to be effective). If additional lag cooling appliances  120  are needed, they are engaged in order according to a lag priority; if all lag appliances are commenced, there may be an operational fault. An alarm may be triggered, or self-remediation approaches may be first invoked. For example, in the event of a transient icing of coils due to excessive humidity, the controller may receive a pressure indication from a cooling appliance indicative of a pressure abnormality, and/or cease operation of the cooling appliance for an equilibrium interval to allow abatement of overpressure and icing conditions, and permit operation after the equilibrium interval to assess if the pressure anomaly has subsided. 
         [0025]    Upon again reaching an acceptable operational temperature, based on satisfaction of the additional cooling indication, the controller ceases operation of one of the lead cooling appliance or the lag cooling appliance, as disclosed at step  314 . This includes, at step  315 , the control logic  152  identifying a return of the operational temperature below the cooling engagement threshold in satisfaction of the cooling demand, and ceasing operation of one or more of the cooling appliances  120  in response to the cooling need satisfaction, as shown at step  316 . 
         [0026]    As indicated above, each of the cooling appliances is defined by operation of an evaporator fan and a compressor. The controller  150  is operable to control the evaporator fan  127  and compressor  124  individually. Accordingly, upon ceasing operation of a cooling appliance, the controller  150  disengaging operation of both the evaporator fan  127  and compressor  124  when ceasing operation of the corresponding cooling appliance  120 . On the next cooling cycle as the operating temperature rises, upon commencing operation based on the operation temperature, the controller  150  powers the evaporator fan  127  of the most recently operated cooling appliance  120  for extracting residual cooling capacity from the evaporator  125  corresponding to the evaporator fan  127 . Cycling operation without compressor operation may suffice to cool the enclosure  110  for considerable time based on the thermal inertia of the most recently operated evaporator. 
         [0027]    Following a normal termination of the cooling appliance  120  due to cooling demand satisfaction, the controller  150  is operable to alternate the lead and lag designations following a return of the operational temperature below the cooling engagement threshold such that none of the cooling appliances are operating. Upon the next cooling demand, the controller  150  will commence operation of a cooling appliance different than the cooling appliance that was most recently operational, based on redesignation of a different lead (and lag) cooling appliance, as shown at step  317 . Upon a subsequent cooling demand based on the operation temperature exceeding the cooling engagement threshold, the controller will commence operation of the alternated lead cooling appliance, in which the lead cooling appliance had been designated as the lag cooling appliance prior to the alternating. 
         [0028]    At step  318 , a check is performed to determine if a lead/lag designation interval has expired. Lead/lag intervals may persist for any suitable duration, such as 6, 12 or 24 hours, following which different lead and lag compressors are selected to evenly distribute uptime and which compressor is initially invoked as the “lead.” Therefore, the controller  150  maintains the lead/lag designations for a designated interval, as depicted at step  319 , and alternates the lead/lag designations following expiration of the interval and operation cessation of the lead cooling appliance  120 . This is to avoid prematurely shutting down a compressor merely to satisfy a designation threshold. The current operating cycle is maintained until the controller  150  shuts down the compressor upon cooling load satisfaction. Alternatively, the designation interval may be defined by a number of power on or commenced/engaged cycles when the cooling appliance is called on to provide cooling, rather than a fixed time period. Re designation then proceeds by commencing a subsequent designation interval with the newly designated lead cooling appliance based on the alternating of lead lag compressors, or reordering of the priority of lag compressors following designation of a different lead cooling appliance (compressor). Control then reverts to step  303  to continue monitoring for the next cooling demand. 
         [0029]      FIGS. 4 a -4 c    are GUI screens for management of the controller device of  FIGS. 1 and 2 . Referring to  FIGS. 1 and 4   a , a system configuration screen  410  provides a GUI interface for introducing cooling appliances  120 . An air con window  412 - 1  . . .  412 - 4  ( 412  generally) provides entry for each cooling appliance  120 . For each window  412 , a “fitted” button  420  designates whether the cooling appliance  120  (cooling unit) is installed (attached). A “never lead” button  422  indicates that the cooling appliance  120  should not be selected as the lead appliance, for example due to insufficient cooling ability to handle the entire cooling demand alone. A thermistor configuration window  414  indicates the number of thermistors, or sensors  162 , employed. A temperature scale window  416  defines temperature units of F or C degrees, and a heater selection  418  provides similar selection for heating capacity. 
         [0030]    Referring to  FIGS. 1 and 4   b , a setpoint screen  430  provides an “on” setpoint  432  for designating the cooling engagement threshold. A max cooling button  434  defines a maximum operating temperature above the cooling engagement threshold. A max temperature across coil  436  indicates an allowable range across the exchanger/evaporator  125 . A staging enable button  438  allows lead lag functionality as disclosed above. A cooling stage differential  440  determines the number of degrees between engagement of successive lag units. For example, a differential of 2 and a cooling engagement threshold of 75 would engage the first lag unit at 77 degrees, the second lag unit at 79, and so on. A stage delay  442  sets a delay before a successive lag unit should be commenced to allow stabilization. An alarm delay sets a delay to allow AC operation to begin dropping the operating temperature before triggering an alarm. 
         [0031]    A heating setup window  450  provides similar controls for heating apparatus (heating apparatus may not be required in some climates, as overheating of the environment is a primary focus of the environmental controls, however heating controls may be implemented using similar control logic). A high temperature alarm window  542  sets thresholds for high temperature alarms, and a low temperature alarm window  454  defines low temperature alarms. 
         [0032]    Referring to  FIG. 4 c   , a lead/lag selection screen  460  refines the designation interval. A run time window  462  allows a designation interval based on a time interval, such as 6, 12 or 24 hours. A run cycle selection window  464  defines a number of on/off cycles in each designation interval. A compressor lockout window  466  allows detection of compressor freeze-up and/or pressure anomalies. 
         [0033]    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 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. 
         [0034]    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.