In this installment of our data center maintenance series, we will discuss fans. While HVAC chillers ensure cool water supplied to fans for cool air is pumped into the servers in a data center, fans ensure that the hot air from the servers is removed efficiently and redirected to the Computer Room Air Conditioning (CRAC) unit.

Several options for cooling fans used in data centers:

  • Centrifugal fans
  • Fiberglass fans
  • Inline centrifugal fans
  • Mixed flow fans
  • Propeller roof ventilators
  • Propeller wall fans
  • Axial fans

Each of these options work best for certain data center conditions. You will have to decide which one will be most efficient for your data center. It’s also important to remember that not only do data centers require large amounts of water to cool servers, they require large amounts of air; an estimated 1.2 million gallons per minute, in fact, so the right fans and ventilators are critical.

Additionally, remember that while fans are part of the cooling process in a data center, their motors also account for seven to nine percent of the heat generated in the data center.

Knowing the outlet velocity of your data center fans is also important. Your particular data center environment (including the climate, layout of servers, etc.) will determine the CFM (cubic feet per minute) of air a fan is able to move.

This number (the CFM of air a fan can move) can vary based on two factors:

  • Air density (hot, low density or cold, high density)
  • Air pressure (positive or negative)

You also need to be aware of things like subfloor vortexes, which can occur when two high velocity air streams intersect from opposite directions and cause a reversal of the air current. This should influence your strategic placement of fans in the data center.

A couple good strategies for fan placement:

  • Eliminate high velocity air. This will ensure a more balanced delivery of air.
  • Create a cold aisle that is not dependent on raised floor tile placement at the foot of each rack.

Always remember that simply adding more or stronger fans will not remedy the underlying issue. You must understand how airflow affects the data center on a larger scale (its environment and other functioning components). Be strategic about using airflow in your data center and you will save energy and increase efficiency.


We invite you to continue to follow along with our data center maintenance blog series. Our next post will cover emergency generators.


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