In a Data Center, proper cooling is one of the most important factors for ensuring the correct operation and reliability of your IT equipment. The cool air has to flow in a specific way around the server racks for good efficiency. Energy costs for cooling are one of the biggest operational expenses (OpEx) for a Data Center.

How Differential Air Pressure Aids in Cooling

Differential air pressure sensors can assist in optimizing the cooling and the airflow in your Data Center. Monitor the system via differential pressure sensors. These sensors will help to understand the airflow patterns and monitor their efficiency throughout your Data Center. For example, the correct sealing of underfloor tiles, indicating possible air leaks, or obstructions in the airflow.

Important Note: Differential pressure is not a measurement of the airflow, just the air pressure that drives this airflow. It’s the difference in the air pressure between one area and another. You may for example place one part of the sensor inside the hot aisle, and another in your cold aisle. The pressure difference between the two would indicate if you have proper airflow from cold to hot. If there was a positive pressure differential in the hot aisle, it would indicate you have hot air leaking back into your cold aisle. The differential pressure is read in Pascals.

In another case, you can place the pressure tubes at the front and rear of the cabinet. There should always be positive pressure at the front of a server cabinet. Air travels from areas of high pressure to low pressure, and it is imperative for efficient cooling to check that there is higher pressure at the front of the cabinet and lower pressure at the rear. However, this doesn’t show the volume of the airflow, only the force at which the air is being pushed.

When you analyze the differential pressure zones and airflow at your Data Center, you will be able to:

  • Optimize airflow and cooling utilization, and apply changes if necessary
  • Find out if the airflow and pressure is incorrect or misdirected
  • Get notified about any airflow changes that might occur, indicating potential leaks or changes in cooling performance
  • Detect a possible HVAC or cooling fans failure
  • Visualize and verify the effects of cooling and air handling efficiency
  • Correlate air pressure/flow changes with the temperature changes when used with temperature sensors

The improved cooling performance will quickly return your investment, in the monitoring system, by optimizing the airflow and cooling systems you can cut your energy bill. Differential air pressure can also be used as an input to control CRAC fan speeds as discussed in this article.

Installation of Differential Pressure Sensors

When you are installing differential pressure sensors, you will need to find two areas with different air pressures – an area with higher airflow will always have a different pressure than an area with a lower flow rate.

These are the typical areas for monitoring:

  • Server racks
  • Between aisles in a Data Center and between underfloor perforated tiles
  • Vents and air plenums

Installing a typical differential pressure sensor is usually as simple as placing the two pressure sensing tubes extending from the sensor to their intended monitoring zones:
Place one tube in a higher-pressure zone with the faster airflow. For example at the base of a server cabinet, where the air intake is. The second tube is in the ambient area where there is little airflow. For example at the top of your cabinet.

The resulting pressure differential reading will indicate the degree of the airflow coming through the cabinet. As noted earlier, keep in mind that this is not a measurement of the airflow rate, only a relative indication. A lower differential pressure will indicate a lower airflow rate, and a higher-pressure value indicates a higher flow rate between the high- and low-pressure zones.

Optimize Data Center Cooling With Differential Pressure Sensors

Data Center Monitoring Solutions

To help monitor your Data Center cooling, AKCP has multiple sensors available. In addition to the Airflow Sensor which can detect the presence or absence of the airflow, you can use our Cabinet Analysis Sensors to help you get a visual representation of each rack in your Data Center, the temperatures, differential pressures, and the flow of air.

Airflow and Thermal Mapping for IT Cabinets
The Cabinet Analysis Sensor (CAS) features a cabinet thermal map for detecting hot spots and a differential pressure sensor for analysis of the airflow. You can monitor up to 16 cabinets from a single IP address with the sensorProbeX+ base units. A Wireless Cabinet Analysis Sensor is also available using our Wireless Tunnel™ Technology.

Differential Temperature (△T) and Thermal Maps
The cabinet thermal maps consist of 2 strings of 3x Temperature and 1x Humidity sensor. With these sensors, you can monitor the temperature at the front and rear of the cabinet, top, middle, and bottom. The △T value, front to rear temperature differential is calculated and displayed with animated arrows in AKCPro Server cabinet rack map views.

Differential Pressure (△D)
There should always be a positive pressure at the front of the cabinet, to ensure that air from hot and cold aisles is not mixing. As the air travels from areas of high pressure to low pressure, it is imperative for efficient cooling to check that there is higher pressure at the front of the cabinet and lower pressure at the rear.
Rack Maps and Containment Views

AKCPro Server Aisle Containment View

With an L-DCIM or PC with AKCPro Server installed, dedicated rack maps displaying Cabinet Analysis Sensor data can be configured to give you a visual representation of each rack in your data center. If you are running a hot/cold aisle containment, then containment views can also be configured to give a sectional view of your racks and containment aisles.

Wireless Cabinet Analysis Sensor – All In One Wireless Cabinet Sensor
The Wireless Cabinet Analysis Sensor (W-CAS) has the same features as the wired Cabinet Analysis Sensor (CAS): cabinet thermal map for detecting hot spots, differential pressure sensor for analysis of airflow, and 2x dry contact inputs for door security sensors. Powered by USB, or 4x AA rechargeable batteries and using AKCP Wireless Wall Penetrating Technology, the data is collected and sent to one of our wireless sensor gateways.
Door Contacts. I/O dry contact inputs can be used to monitor the front and rear doors of the cabinet, or alternatively alarm outputs from UPS or other rack-mounted equipment.

AKCP Cabinet Analysis Sensor Installation examples

The sensors and SP2+ base unit are installed in the rack.

1U L-DCIM with SP2+ and Cabinet Analysis Sensor

On the top of this picture, the wireless L-DCIM unit in its 1U configuration is also shown.

A second Airflow sensor and the differential pressure sensor’s second tube are mounted at the back of the rack. On the rear rack door, the Thermal Map’s temperature sensor can also be seen.

Differential air pressure tube at rear of rack

This is the full rack view from the front. The differential pressure sensor’s first tube is mounted at the front of the rack, where the cooled air enters the cabinet. There is also an LCD sensor and Sensor Status Light on top of the rack.

Full Rack View of cabinet analysis sensor

On the front rack door, the Thermal Map’s temperature sensors can also be seen, and there is a Swing Handle Lock installed to secure the door.

This picture shows the Wireless Cabinet Analysis Sensor (W-CAS) on top of the rack. Due to its wireless nature, it could be placed anywhere at strategic locations for efficient monitoring.

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