A long-running question in data center circles centers on whether hot air or cold air containment systems are a better fit for an existing data center. As explained in a previous post, and in the Schneider Electric white paper “Implementing Hot and Cold Air Containment in Existing Data Centers,” the answer is a resounding, “It depends.”
In the previous post, we looked at some of the constraints that may lead you to one type of containment system or the other. In this post, we’ll look briefly at some of the more common data center configurations and fill you in on which type of containment system is likely the best fit for each.
1. Let’s say the data center is set up in a hot aisle / cold aisle arrangement, with the raised floor used as a supply air plenum. (For more information about that topic, see white paper number 135, “Impact of Hot and Cold Aisle Containment on Data Center Temperature and Efficiency.”) The height between the top of the rack and ceiling is less than 20 inches (508 mm).
A cold aisle containment system (CACS) will best fit this situation because it takes advantage of the existing raised floor plenum to deliver cool air. The CACS will enclose the cold aisle while the rest of the room essentially becomes a large hot air return plenum. If high-density racks can’t pull enough cold air from the raised floor, you may need active tiles or air distribution units to help. Both provide a means to direct more cold air to certain racks.
2. In our second scenario, the data center is set up in a hot aisle / cold aisle arrangement, but there’s no raised floor. Instead, the drop ceiling is used as a return air plenum, and the height between the top of the racks and ceiling is greater than 20 inches. Also, there are stand-alone IT devices, such as storage systems, on the data center perimeter.
In this case, a ducted hot aisle containment system (Ducted HACS) may be in order.
This method can be used with either a raised floor or a hard floor-based (room-cooled) air distribution system. Ducted HACS encloses the hot aisle, allowing the rest of the data center to become a large cold-air plenum. That cold air should be enough to cool standalone IT systems that are not enclosed by the containment system. It’s also preferable when people will routinely be working in the data center, as the cool air will keep it comfortable. (For more information about this topic, please watch for the soon-to-be-released white paper number 182, “The Use of Ducted Air Containment Systems in Data Centers.”)
3. Now let’s suppose the data center is not set up in a hot aisle / cold aisle arrangement. The drop ceiling is used as a return air plenum, and the height between the top of the racks and ceiling is greater than 20 inches. Also, high-density racks are scattered in different areas of the data center and building columns prevent the use of aisle containment systems.
This scenario may lend itself to a ducted rack containment system. With this method, a duct is mounted to the back of each rack to contain the hot exhaust air, and then duct it into the drop ceiling. Containing the exhaust airflow path has the effect of separating hot and cold air streams.
4. Finally, let’s say the data center is not set up in a hot aisle / cold aisle arrangement but the height between the top of the racks and ceiling is less than 20 inches. Again there are scattered high-density racks.
A rack air containment system (RACS) may be the best bet for this configuration. It’s an ideal solution for use with very high-density racks because it integrates rack-based cooling units with the racks, forcing the air to circulate only inside of the containment. (For more information about this topic, see white paper number 130, “Choosing between Room, Row, and Rack-based Cooling for Data Centers.”)
Check out white paper number 153, “Implementing Hot and Cold Air Containment in Existing Data Centers,” for more information on each of these scenarios as well as tips on some of the features to look for in any containment system.