In its simplest form, Hot Aisle Containment (HAC) consists of a barrier that guides hot aisle exhaust airflow upward back to the CRAC (computer room air conditioner) return. This method keeps hot exhaust air emitted from server racks separated. Keep in mind though, while HAC improves energy efficiency compared to no HAC; it can add cooling (and power) load because of larger fans to overcome additional pressure drops.
Benefits
✓ One redundant cooling unit can serve several aisle containments.
✓ HAC with Inrow cooling improves energy efficiency compared to traditional raised floor cooling with HAC.
✓ Typically a rack hat style containment with end row doors.
✓ Minimizes cold and hot air mixing so the return temperature to the CRAC is higher.
✓ HAC with Inrow cooling can cool more than 30kW heat load per rack.
Considerations
1
Cooling is not focused cooling
The open air distribution increases the risk of providing the servers with input air that is not the required temperature.
2
Air temperatures potentially are high
Air temperatures can exceed acceptable levels for personnel working in the aisle.
3
Requires complete hot air ducting
The hot return air must be ducted all the way from the HAC to the air inlet of the CRAC. This typically entails using the overhead plenum for return air (if possible), ducting between the HAC and ceiling plenum, and ducting between the ceiling plenum and the CRACs.
4
Plug leaks
The data center should plug leaks both around the 19-inch rails in front of the racks and in the U space among the rack mounts by using blanking panels. Plug holes in raised floors around cabling with floor grommets.
