Data Center Handbook

24Hot Aisle versus Cold Aisle Containment

Dave Moody

Schneider Electric ITB, O’Fallon, MO, USA

24.1 Executive Summary

Hot Aisle Containment system (HACS) or Cold Aisle Containment system (CACS) can be installed in new or existing data centers, in conjunction with internal or external cooling systems, and either on raised-floor systems or hard-floor (overhead) systems. Passive ducts directly from racks (chimney) are considered a special case of HACS.

Both Hot Aisle Containment (HAC) and Cold Aisle Containment (CAC) are capable of their primary function, which is separation of the cool supply air and hot return airflow streams in a data center.

Both HAC and CAC may provide a benefit to some degree as follows:

1. Increase cooling system coil capacity, by affecting Return Air Temperature (RAT)
2. Increase cooling system coil efficiency, by affecting RAT
3. Decrease cooling system fan power
4. Provide predictable and reliable IT equipment inlet air temperatures
5. Improve redundancy in row-based cooling system by extending the sphere of influence for the cooling units

HACS and CACS also impact data center operations as follows:

6. Affect personnel working conditions inside the data center or inside the containment system
7. Impact ride-through time for cooling system and data center temperatures in the event of cooling system failure or cooling system power loss
8. Impact conditions for peripheral equipment in the data center outside any of the HAC or CAC zone(s)
9. Impact economizer operation time periods ...