This is the fourth article in a best practices series on data center energy efficiency through effective airflow management strategies.
Containment components include rack containment using rack-based chimneys, and aisle containment using end of row doors, aisle ceilings and overhead vertical wall systems. Chimneys affix to the hot air side of the rack, ducting hot air into a drop ceiling or return plenum that leads to the air conditioning system. Passive chimneys use the plenum’s negative pressure to pull the hot air out. Active chimneys with fans move hot air based on rack temperature or the difference in pressure inside and outside the rack.
End of row doors seal off the end of the aisle. Vendors offer end of row doors in a variety of practical configurations. The vendor should be able to tailor door selections to suit each data center’s specific spatial requirements.
Door configurations include swinging or sliding doors that are available as single or double doors. The data center may require an emergency break out feature for sliding doors to meet emergency evacuation safety standards. When a smoke or fire alarm sounds, staff members can break through the door via a break out bar that opens a separate door on a hinge. This will ensure that staff are not trapped in an emergency.
Vendors offer additional door options including auto-close, soft close and auto lockout capabilities. Auto-close enables the door to quickly re-establish an airtight seal. Soft closing doors use snubbers to slow auto-closing. This ensures that the doors won’t close on the staff or customers who are entering or leaving the aisle. Auto lockout stabilizes doors in the open position allowing hands to be free to move data center equipment in and out of the aisle.
Glass doors or small windows are available for data centers seeking visibility into the aisle. Glass doors and windows maintain aisle visibility without forcing staff to enter the aisle.
Data centers can top off their aisles with precise ceiling types and options as the vendor brings them closer to total containment. The vendor can deliver a horizontal structure, which is a flat-aisle covering or roof. The overhead vertical wall approach constructs one wall along the top of a row of racks, a second vertical wall on the top of the opposing row of racks and one at each end of the aisle, creating a rectangular box that contains the air.
There are a number of factors that data centers should consider when selecting containment solutions. The application specific environmental requirements of the data center including the cooling supply source and type, fire suppression design, the human factor and rack hygiene form one set of factors.
The data center should marry cooling that emanates from CRAC units, raised floors, perimeter cooling, and overhead cooling systems to the most compatible containment option. For example, while the hot aisle approach is usually best for CRAC/CRAH units, the cold aisle approach is usually best for perimeter cooling on raised floor or ducted cold air delivery from roof top chillers.
Data center fire suppression techniques including sprinklers, gas systems and VESDA systems can affect containment selection. Vertical walls and horizontal structures with intelligent panels are best suited for overhead fire suppression.
Data center employees and customers may not want to work in a data center environment that is 100-degrees. If the data center contains the cold aisle, the rest of the data center is the hot aisle, which can be 95- to 110- degrees. If the data center contains the hot aisle, the rest of the data center will be cold. When staff or customers enter the hot aisle, it will be 95- to 110-degrees. The data center may want to factor in the effect of requiring its personnel to acclimate to an environment that is either too hot or too cold while also considering the effect of moving between the two when working inside and outside the aisle.
Once containment is in place, the rack becomes an airflow plenum. The data center that invests in containment should not waste the effort by permitting poor rack hygiene and air leakage through the rack. In an aisle with 10 racks on each side or 20 in the pod, the racks make up approximately 60-percent of the total surface area. Leaking racks could lead hot and cold air to mix, defeating the data center’s containment efforts.
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.
Next Thursday's article will cover containment providers and due diligence. If you would prefer, you can download the complete Data Center Knowledge Guide to Data Center Containment in PDF form, courtesy of Eaton.