Patent ID: 12196438

DETAILED DESCRIPTION

A machine enclosure for housing electronic equipment such as telecommunications hardware needs to maintain a conditioned space for proper equipment operation. Such machine enclosures may be referred to as machine rooms, telecoms enclosures and the like, and in general represent HVAC controlled spaces suited for computer and network hardware, typically for supporting telecommunications and related network information and media traffic. While sensitive to temperatures, electronic equipment operates over a much larger temperature range than a human conditioned space, and is typically more focused on cooling operations as the equipment itself tends to generate substantial heat. Previous approaches to temperature regulation in machine enclosures are discussed in U.S. Pat. No. 8,313,038, filed Nov. 20, 2012, entitled TELECOM SHELTER COOLING AND CONTROL SYSTEM,” and U.S. patent application Ser. No. 16/417,874, filed May 21, 2019, entitled “VENTILATION CONTROL APPARATUS AND METHOD,” both incorporated herein by reference. The former is directed to Direct Air Control (DAC) for drawing in outside air to supplement native HVAC temperature control. The latter controls the temperature over a range, rather than a single setpoint and/or tolerance as typical human occupied spaces are. The approach claimed herein extends such approaches by varying a fan speed driving air exchange to make efficient use of mechanical HVAC only when needed without introducing excessive humidity or harsh temperate changes from a high temperature differential of ambient outside air.

In an example configuration shown below, the temperature differential maps to a table of variations from the differential to determine an appropriate fan speed. The controller indexes a target delta temperature based on the machine room temperature, and computes a delta T offset from a shortfall in the temperature differential from the indexed target delta temperature. The delta T offset provides a variation in the temperature differential that can be tolerated, and therefore defines an operating band of temperature around which the fan operates. For a particular machine room temperature, the controller adjusts the fan speed based on the delta T offset as indexed in the target delta T table, shown further below. The temperature differential indicates the cooling value of the incoming air; the delta T offset indicates a temperature differential that is sought. This is mapped to an input for fan speed, such as a PWM (Pulse Width Modulated) control signal, to increase or decrease the rate of exchange based on the temperature differential. PWM is employed as an example AC motor control medium that is well suited to a fan speed, however any suitable variable speed control may be employed.

FIG.1is a context view of a machine or equipment room environment100suitable for use with configurations herein. Referring toFIG.1, in the machine room environment100, the machine enclosure101defines a conditioned space102for maintaining telecommunication equipment110within a working temperature range. The telecommunication equipment110performs any number of a variety of tasks, typically including connection and transmission of information on a wireless112or wired114network such as the Internet.

The machine enclosure101or room includes a native HVAC system120, including an outside compressor122, heat exchanger124and fan, inside the enclosure101, and a controller130. The controller130engages the native HVAC system, often via a simple, low voltage (24V) connection commonly utilized for a conventional thermostat, and also implements direct air control (DAC)150by one or more fans132-1. . .132-3(132generally) and an exhaust louver134or vent for exhausting machine room air in favor of ambient outside air drawn in by the fan132. The fan132may be invoked (energized) according to control logic136that pulls in ambient outside air when a sufficient temperature differential exists to provide efficient cooling in lieu of the mechanical HVAC system120. Conventional approaches would instead seek mechanical cooling as the unventilated enclosure builds heat from the equipment110, even if the ambient outside air was substantially colder.

An internal temperature sensor107, such as a thermistor or similar device, senses the temperature inside the machine room. Another temperature sensor109is on a fan tray or air intake for sensing the temperature of the ambient outside air105. Alternatively, the ambient sensor109′ may be mounted outside. Either of these may have redundant or backup sensors for accommodating failure or air pockets inside the enclosure101, discussed further below.

The control logic136further increase efficiency by running the fans132at a speed needed to effect proper cooling without excessive and air turnover. Running the fans more slowly yet still achieving sufficient cooling saves electrical energy and avoids temperature extremes that can lead to condensation, for example. The flowcharts below illustrate operation based on periodic measurement of temperature and motor speed control. Temperature is measured by thermistors or similar sensors, typically at the outside air intake and at one or more machine room locations. This may include designating one of a plurality of sensors in the machine room as an active sensor and employing the active sensor for determining the machine room temperature. Air exchange is moderated by controlling the fan speed, for example, by changing the PWM voltage signal or setting an input voltage or supplying a serial interface input supplied to a fan motor.

In general, the temperature differential represents the cooling value of the exchanged ambient air. The controller increases the fan speed as the computed delta T offset increases for drawing in additional ambient air to compensate for a decreasing temperature differential, since the outside air is not cooling as much. Conversely, the controller decreases the fan speed as the computed delta T offset decreases for moderating a volume of ambient air as the temperature differential increases, as when the outside air is cooling substantially as a result of a high differential. The target delta T table indicates this band for a given machine room temperature, such that the fan speed is based on the target delta T. In an example configuration, the table is defined by a GUI (Graphical User Interface) user parameter, which receives values for the table mapping the machine room temperature to the target delta temperature, and for indexing the target delta temperature based on the table.

Concurrently, upon invoking the mechanical HVAC compressors and/or other devices for cooling, the controller closes an ambient air exchange portal, or exhaust vent134, for separating an environment of the machine room from the outside air and turning off the fan driving the ambient air exchange, to effectively seal off the now HVAC conditioned space in the machine enclosure106. It should be noted that while the HVAC system coordinates both cooling and heating of the machine enclosure101, ambient air exchange is unlikely to be invoked for increasing the temperature in the machine enclosure, i.e. in a heating context.

FIG.2is a flowchart200of fan operation in the machine room ofFIG.1. Referring toFIGS.1and2, the method of controlling a machine enclosure internal temperature through an ambient air exchange as defined herein includes, at step201, receiving an indication of a temperature of machine room air102inside the machine enclosure101, and receiving an indication of an ambient air temperature of ambient air105outside the machine enclosure101, as depicted at step202. The controller130modulates a fan speed of the fan(s)132-N driving an exchange of the ambient air105outside with the air102inside the machine enclosure101based on a difference between the machine room temperature and the ambient air temperature, as shown at step203.

FIG.3is a block diagram of fan control based on the flowchart ofFIG.2. Referring toFIGS.1-3, the controller130includes native HVAC control120and direct air control (DAC)150. The DAC150includes control logic136for fan speed control as defined herein. Inside sensors107-1. . .107-N provide temperature sensing inside the enclosure101, and one or more ambient air sensors109sense the temperature of the incoming ambient air for exchange. Based on the temperature information, the control logic136controls the fan132speed for increased or decreased exchange of the ambient outside air105. Modulating the fan speed based on the temperature differential, rather than an absolute outside temperature, limits air exchange for maintaining a relative humidity in the machine room at a non-condensing level, even when the thermal load inside the machine enclosure drops.

The control logic136determines when the ambient air exchange becomes ineffective at maintaining the machine room temperature, and invokes a mechanical cooling device such as air conditioning115for maintaining the machine room temperature. As the temperature differential narrows and the effectiveness of ambient air exchange degrades, control reverts to the native HVAC control120for air conditioning115and/or115, defined by the HVAC equipment described above.

FIG.4Ais a graph of temperature response in the machine room ofFIGS.1-3, andFIG.4Bis a GUI example for setting the temperature response. Referring initially toFIG.4A, a graph400depicts temperature response in the machine enclosure101in response to the control logic136. A vertical axis402depicts a speed of the fan motor as directed by the control logic136. The axis402ranges from 0-100% of motor speed, typically as a PWM (Pulse Width Modulated) signal to the motor driving the fans132. A horizontal axis404depicts the temperature differential between the temperatures of the conditioned space102and outside (ambient) air105.

At a given temperature differential404, the control logic136maps a fan speed402based on a speed curve410. The speed curve410shows a linear response, however this may be augmented by a GUI configuration, shown further below inFIG.4B. In general, the speed curve410demonstrates that a larger temperature differential404allows a slower motor speed402, thus resulting in a reduced volume of ambient air exchange needed for cooling since the air provides greater thermal mass.

An example scenario shows an ambient air105temperature of 60° F. and conditioned space102temperature of 80° F., yielding a temperature differential of 20° F. Mapping this value to the speed curve410indicates a fan speed of 75% at position420. Another example shows an ambient 30° F. temperature and a conditioned space102at 80° F., computing to a temperature differential of 50°. Since the differential is greater, a lower fan speed is needed for the same thermal effect. Accordingly, the mapped fan speed, given by point422, is only 25%.

FIG.4Bis an example for setting the speed curve and related parameters in a GUI for the controller130. Referring toFIGS.1-4B, the speed curve410is settable in a series of steps452, each defining a particular temperature450along the speed curve410, shown on the horizontal axis414. At each step, a corresponding target delta T defines the temperature differential that should be sought, shown on the vertical axis412. The resulting commanded fan speed is based on a delta t offset between the current temperature differential and the target delta T. The commanded fan speed increases if greater cooling, resulting from a greater delta T offset, is called for. A separate pull down440provided for a turn-off temperature, at which the air exchange is halted to define the temperature value at which the fans are not required to run as no cooling is necessary. Another pulldown442provides a hysteresis to avoid rapid on/off cycling as the system operates near the turn off440threshold.

FIG.5is a flowchart of fan control in the machine room ofFIGS.1-3. Referring toFIGS.1-5, in a particular configuration, the controller130launches a control application for activating the ambient air exchange (DAC)150and the native mechanical HVAC120system for maintaining the machine room temperature within a predetermined range. A full control loop considers both DAC and HVAC control for optimal efficiency. If called for, the control logic136in the DAC150determines, based on a temperature differential between the machine room temperature and the ambient air temperature; whether ambient air exchange is effective for maintaining the machine room temperature. If so, the control logic136iteratively compares an update counter in a control loop for determining whether a change to the fan speed is called for.

The controller130controls all aspects of the temperature in the machine enclosure, and therefore invokes both HVAC control120and DAC control logic136as needed, typically in an iterative or looping manner as various temperatures and other parameters are examined. InFIG.5, a control loop500in the control logic136reads the internal temperature sensor107for determining the ambient air temperature of the conditioned space102in the machine room, and the temperature sensor109for outside air105, as depicted at step502. A check is performed, at step504, for any detected failure that might compromise the equipment (i.e. runaway heating or cooling), and if so a remedial measure to fully ventilate occurs, at step506.

The control logic136computes a temperature differential based on a difference between the machine room temperature and the ambient air temperature, as depicted at step508. If the ambient air temperature is not above the fan shutoff specified by pulldowns440and442, at step508, the fans are turned off by issuing a PWM control of 0, as cooling is sufficient, as shown at step510, and the loop exited.

Otherwise, sampling for hot/cold spots in the machine enclosure101occurs at step512, discussed further inFIG.6. Sampling occurs when all fans continue to be off since cooling is not called for. If the sampling flag is turned on in the sampling step512, then the loop exits at step514, otherwise a check is performed to determine if the fan speed, or PWM commands, should be updated, as depicted at step516. Since the control loop500is part of a larger operating sequence, continual iterations are made, and not all iterations need to address fan speed or air sampling. Hence, a set of counters identifies which checks and controls should be interrogated during a given iteration. is updated. For example, if the main controller130loop cycle is set to 1 s., then a PWM count of 20 would update the PWM speed settings every 20 s. If fan speeds are not due for checking/updates, then the PWM counter is incremented at step518until successive iterations call for updated fan speed settings.

If the check at step516calls for an update, then the fan speeds are updated, as shown at step520. This includes computing a temperature differential based on a difference between the machine room temperature and the ambient air temperature, and either decreasing the fan speed for decreasing a rate of ambient air exchange as the temperature differential increases, or increasing the fan speed for increasing a rate of ambient air exchange as the temperature differential decreases. A mapping is performed, based on the current temperature differential, using the speed curve410. If needed, a new fan speed402is mapped based on the temperature differential (internal sensor107—ambient temperate109), and the mapped speed sent to the fan132as a PWM command based on the percentage of full speed, as shown at step522. The PWM cycle counter is reset at step524for the next iteration.

not turned on.

During a period of ambient air exchange, such as overnight, the ambient air exchange may drive the machine room temperature below a shutoff temperature, meaning that ambient air exchange has satisfied the cooling demand. In this state, the controller deactivates the fan due to satisfaction of the machine room temperature in response to the ambient air exchange. Since the air is now dormant, the controller periodically cycles the fans to an activated state regardless of thermal demand to update each of the plurality of sensors based on thermal pockets and changing outside temperatures. This will force enough ambient air through to update the intake air (outside) temperature reading and the interior machine room temperature to alleviate any “hot spots” that may have evolved.

FIG.6is a flowchart of sampling intervals in the flowchart ofFIG.4. Referring toFIGS.5and6,FIG.6shows a sampling operation that concludes that ambient air exchange is idle, meaning cooling is not called for. Sampling includes periodically energizing the fan for normalizing the machine room temperature by agitating stagnant air, computing the temperature differential based on the freshly agitated air to dissipate any hot or cold spots, and then reengaging the fans for ambient air exchange if called for.

From step512, a check is performed, at step602, to determine if the fans are idle (i.e. PWM controls at0). If so, this means the controller130is in a sampling mode and the sampling timer is checked, at step604. If the sampling timer indicates that the sampling period has expired, then the fans132are set accordingly, at step606, the sampling timer reset (step608), and the sampling flag set ON, at step610, to commence an active sampling. Setting the fans for sampling means running at a low speed, such as 12%, to dissipate the machine room air to achieve a uniform temperature.

On the next iteration, since the fans are not OFF (but rather at a sampling speed), the sampling flag will be checked, as shown at step612, and the sampling timer checked to see if a full sampling interval has been achieved (i.e. enough to uniformly distribute the machine room air102), as shown at step614. If not, sampling continues until the timer expires, and then at step616, the sampling flag set to OFF at step616and the sampling timer reset, at step618.

In the full machine room management context, the ambient air exchange described above performs direct air cooling and is coupled with a mechanical (compressor driven) HVAC system for heating and cooling when needed. The direct air cooling (DAC) is often an efficiency increasing complement to full range HVAC systems, which were common in conventional installations as the only environmental control. Several operating scenarios follow to illustrate.

In a typical operating scenario, ambient air exchange is likely to be most effective at night, when the ambient temperatures are cooler. Following sunrise, as the ambient temperature increases, ambient air circulation becomes more aggressive, cycling the fan around a temperature band defined by the delta T offset tolerated at a particular machine room temperature. Ultimately, native HVAC control will be invoked in view of the increasing cooling demand. A temperature of the machine room fluctuates during ambient exchange around a band defined by the delta T offset. The controller identifies when an operating band defined by the delta T offset and resulting fan speed results in an extended running cycle of the fans, and increases the fan speed for increasing ambient air exchange prior to invoking the mechanical HVAC cooling. Therefore, just prior to the limits of the ambient air exchange, the mapped fan speed may not be forcing a maximum amount of air, i.e. the PWM control value dictated by the target delta T value may not be the fan top speed. Upon detecting an upper limit to the temperature maintained by the ambient air exchange, fan speed may be increased to a maximum to force additional cooler air (based on the temperature differential) to extract as much cooling as possible from the ambient air prior to the compressor handoff.

The control loop provides an effective way to allow both the mechanical HVAC and DAC to alternate at appropriate times for achieving an efficient approach. Since the machine enclosures101are often unattended, an autonomous control is important. In an example scenario, the control130iteratively executes instruction in a control loop for assessing heating and cooling demand in the machine enclosure. The control loop evaluates, at each iteration, whether ambient air exchange or mechanical cooling is better suited for maintaining the machine room temperature in an operational range, and selectively invokes the ambient air exchange based on the evaluation. Evaluation including computing the temperature differential between the machine room temperature and the ambient air temperature when the ambient air temperature indicates an offset with a target machine room temperature.

When ambient air circulation is selected, the control loop determines when the ambient air exchange has cooled the air in the machine enclosure to a machine room temperature at or below a target machine room temperature, typically defined by a range of acceptable temperatures. Ambient air exchange is disengaged, and a sampling flag is set for commencing periodic sampling of the machine room temperature. The control loop reevaluates the machine room temperature upon expiration of a sampling interval, and when called for, reengages the ambient air exchange based on the machine room temperature following the sampling interval.

Another scenario includes determining that the machine room temperature is below a temperature threshold indicative of a cooling need, and therefore disengages the ambient air exchange based on the satisfactory machine room temperature. The machine room temperature is periodically reevaluated in the control loop.

Another typical scenario involves changeover to a mechanical HVAC when the daytime ambient temperature increases. The control loop determines that the temperature differential has limited an effectiveness of the ambient air exchange for reducing the machine room temperature, meaning that the ambient air exchange is approaching its limit for effective cooling. Just prior to the changeover, the control loop will run the fan at a maximum speed for increasing a cooling effect of the ambient air exchange. This extends the ambient exchange to pull maximum cooling from the ambient air, even if the speed mapping might have indicated less than full speed. The control loop then disengages the ambient air exchange in favor of activation of the HVAC system, likely until cooler temperatures return, such as sundown.

Those skilled in the art should readily appreciate that the programs and methods defined herein are deliverable to a user processing and rendering device in many forms, including but not limited to a) information permanently stored on non-writeable storage media such as ROM devices, b) information alterably stored on writeable non-transitory storage media such as floppy disks, magnetic tapes, CDs, RAM devices, and other magnetic and optical media, or c) information conveyed to a computer through communication media, as in an electronic network such as the Internet or telephone modem lines. The operations and methods may be implemented in a software executable object or as a set of encoded instructions for execution by a processor responsive to the instructions. Alternatively, the operations and methods disclosed herein may be embodied in whole or in part using hardware components, such as Application Specific Integrated Circuits (ASICs), Field Programmable Gate Arrays (FPGAs), state machines, controllers or other hardware components or devices, or a combination of hardware, software, and firmware components.

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.