How to Choose Between Hot-Aisle and Cold-Aisle Containment

What is Aisle containment?

Aisle containment is a proven technique for optimizing data center cooling.. It builds upon the best practice of arranging racks and cabinets with the fronts of racks in one row facing the fronts of racks in an adjacent row. That way, hot exhaust air from the back is less likely to be drawn into nearby equipment. An aisle containment solution further minimizes hot and cold air mixing by capturing the air within a given aisle.

There are two choices for data center hot-aisle and cold-aisle containment — and there isn’t much guidance out in the marketplace as to which way to go. However, there are a few variables that can help you decide. It depends on how the data center is cooled and where the heat is rejected.

Why Cold-Aisle Containment

Data Center cold-aisle containment is by far the more common technique. Generally, doors are installed at each end of the aisle so that the aisle fills with chilled air. Sometimes a roof is used as well. In addition to focusing chilled air on the intake side of the equipment, cold-aisle containment makes the environment more comfortable for IT staff.

Why Hot-Aisle Containment

Data Center hot-aisle containment has value as well, although it’s somewhat less intuitive. The goal of hot-aisle containment is to trap exhaust air at its hottest point and provide it with a direct path into the AC return. Hot-aisle containment increases the cooling capacity of AC units, which is measured as the ratio of the difference between supply and return air temperatures.

With that in mind, there are three situations when hot-aisle containment would be the preferred method.

• Chilled air is not effectively getting into the aisle. If you’re going to box off the cold aisle, you need to ensure that chilled air is getting into the space. Otherwise, the chilled air will simply blow over the cold aisle into the hot aisle and not cool the equipment.
• The data center has a slab floor. Cold-aisle containment is most often used in environments where cold air is generated outside the containment area and brought in through the floor. If you have a slab floor, you’d have to bring the containment system up to the ceiling of the cold aisle to capture the chilled air and keep the hot air out.
• You’re using in-row cooling. In-row cooling units are most efficient when the return air is as hot as possible, so hot-aisle containment should be used. Also, if the in-row cooling unit fails in a cold-aisle containment configuration, chilled air won’t get to the IT equipment.

Here are some best practices for data center aisle containment

• Seal gaps and leaks: Containment systems are only effective if they are properly sealed. Gaps and leaks can allow hot air to mix with cold air, reducing the efficiency of cooling systems. Ensure that all gaps and leaks are properly sealed using materials such as brush seals, gaskets, or adhesive strips.
• Use blanking panels: Blanking panels are used to fill empty spaces in server racks, preventing hot air from escaping and cold air from being wasted. This can improve cooling efficiency and reduce energy costs.
• Monitor temperature and humidity: Monitoring temperature and humidity levels in the data center is important for ensuring that cooling systems are operating within the recommended range. Use sensors to monitor temperature and humidity levels, and adjust cooling systems as necessary.
• Regularly maintain containment systems: Regular maintenance is necessary to ensure that containment systems continue to function properly. This includes inspecting seals and panels, replacing damaged components, and cleaning equipment.
• Consider raising the roof to allow more headroom. Most containment systems have a flat roof that goes over the tops of the racks. Many data centers are using 48U and 52U racks, which means a ladder is needed to get to the gear at the top. It’s recommend raising the roof four to six inches.

There are no hard and fast rules as to the choice between cold-aisle and hot-aisle containment. But if you understand how AC systems work and how your data center cooling is designed, you can identify situations where hot-aisle containment is preferred. Contact Us for more information about Data Center Cooling Solutions.