Why do CRAC units love to eat hot air?

Why do CRAC units love to eat hot air?

CRAC's should be eating up all equipment exhaust in the facility.

As an increasing number of organizations move data into the cloud, colocation facilities can expect to see a surge in market value. By 2020, MarketsandMarkets has predicted that the colocation market will be worth more than $54 billion, up from $25 billion in 2015. This is mainly a result of organizations interested in controlling their own data storage, without actually having to purchase property to build their own data centers. In a colocation model, they simply rent out the space and each tenant fills their space with the servers and other computing equipment. Maintenance of this hardware will be a somewhat joint effort between the organizations' IT staff and the colocation provider depending on the terms of the service-level agreement.

That said, maintenance of the data center environment will fall entirely on the shoulders of the colocation provider. This includes the management of all environmental levels. In the modern data center, traditional air conditioners have mostly been replaced by computer-room air conditioning (CRAC) units. The primary function of the CRAC is to draw in hot air, treat it so that it is within a desired temperature and humidity range, and then exhale it back into the data center. 

The more hot air reaching the CRAC, the better

Many colocation data center managers set up their CRAC cooling units in a hot-aisle, cold-aisle layout. Perforated tiles on the floor will expel cool air from the CRAC, which passes through the front of the cabinets and is then released at the back of the rack as hot air. The aisle in which cool air is being released is the cold aisle, while the opposite aisle is referred to as the hot aisle. In this model, the air in the hot aisle should rise into plenum where it is channeled back to the CRAC unit. This air is then treated and released again into the cold aisle.  

"Exhaust all too often finds its way into the cold aisle."

However, this methodology is often imperfect. The cool air in the cold aisle might mix with the warmer air from the hot aisle, resulting in inefficient cooling. This typically happens as a result of poor containment.

According to Data Center Knowledge contributor Bill Kleyman, the most important aspect of airflow management is to be sure that hot and cold air never mix. If one or the other is adequately contained, this should not be a problem.

With hot-air containment, the goal is to capture as much exhaust as possible from equipment, and feed it to the CRAC. The more hot air the CRAC eats, the more efficient a colocation cooling strategy will be. This means less money spent on air conditioning and a much slimmer chance of overheating equipment thanks to reliable cooling components. 

Geist Cool provides a smarter way to manage airflow.Geist Cool provides a smarter way to manage airflow.

Smart airflow systems: The key to consistent containment

The only way to ensure that the CRAC is constantly receiving hot air, and only hot air, is to make sure that all exhaust is consistently isolated and expelled. Even for a hot-aisle or cold-aisle containment system, this is a difficult task. This is because exhaust always has a way to escape into the other aisle, and vice versa. 

A more efficient method is to make all of your aisles cold aisles by guiding hot air directly into a return plenum using chimneys installed at the top of cabinets. This is at the core of why Geist ActiveAir is such an effective airflow and cooling management system.

Smart fans that rely on pressure sensors control how much cool air passes through equipment as it is released from vents on the floor. Exhaust from hardware is then captured, passed through chimneys – also integrated with sensors – and fed directly into the plenum, where it can be swallowed up by the CRAC, never to mix with cool air. Because warm air never actually reaches any of the aisles, maximum cooling efficiency is achieved.

A CRAC will do any colocation management team's bidding, but only if it's getting a consistent flow of hot air – and not just most of it, but all of it. Reliable containment and smart, pressure-controlled cooling fans are the closest thing to a perfect containment method. Settle for no less in a colocation facility.