Full of Hot Air: Debunking the Hot Aisle Containment Myth

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It’s no secret that temperature-controlled air flow is crucial to the design and everyday workings of a data center. It’s a pretty simple concept: The harder your server equipment is working, the more heat it exhausts – and at a certain temperature, it will cost more money in the long run if your machines are working too hot…and too hard. And worst-case scenario: running your equipment too hot for too long will shorten its life span and cost you real money, not just a higher electric bill. That’s where cold aisle containment and hot aisle containment come in. But is the term “hot aisle containment” an oxymoron? We believe it is – here’s why.

At the end of the day the goal is to make sure your equipment maintains a sustainable operating temperature, achieved through having ideal equipment intake temperatures (which vary based on equipment), with typical intake temperatures between 68 and 72 degrees. Cold aisle containment contains cold air that’s pumped into the data center, holding it in the aisles to keep things cool. Pretty simple, right?

But in the case of what to do with the hot air, containing it is exactly the wrong thing to do. Logistically speaking, even though it’s called hot aisle “containment,” the goal is actually to push the hot air out. The exact opposite of what the term suggests. So instead, we like to think of it as hot aisle management.

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Using this term, it’s a lot easier to explain how the overall approach works. Hot aisle management takes advantage of the natural flow of air. Underfloor conditioned air enters the cold aisle through perforated floor tiles; the cold air is pulled into the front of the rack mount equipment using fans to facilitate this movement. At the same time, exhaust leaves the rear of the rack mount equipment and exits the enclosure into the hot aisle. Vertical panels above the enclosure create a barrier and prevent the exhaust from recirculating into the cold aisle from above the enclosures; because hot air rises, the exhaust simply goes up to the ceiling and is funneled back into a CRAC (Computer Room Air Conditioning) unit. The CRAC unit then cools the exhaust and recycles it back to the underfloor cooling system where the process starts all over again.

By comparison, in a cold air containment setup, the goal is to pump cold air into the cold aisle– and keep it there. To do so, partitions are placed across the top of the aisle so that the cold air that is being pumped in from below is trapped inside the aisle and instead goes into the equipment racks to keep them cool. That’s why that term – cold aisle containment – does make sense.

No matter what approach you take – or what you call it – keeping your equipment at an optimal temperature is imperative to the safety and effectiveness of your data center or server room. Looking for more information on data centers, air flow, and more?

Chill out and give us a call. We’re here to help.

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