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Many data centers use a hybrid cooling strategy, with row cooling for all the rack-mounted IT equipment and supplemental cooling for ancillary equipment such as tape systems and storage units that can’t be rack-mounted for whatever reason. But if you’re designing a new data center that will use row cooling as the primary cooling system, you can realize significant benefits by going with purely row cooling vs. a hybrid approach. Those benefits include:
- Eliminating the cost of installing and maintaining a raised floor to distribute air to IT equipment.
- No fighting between row and perimeter coolers
- Lower capital expenses by eliminating over–conservative data center designs with respect to cooling
- Simpler redundancy by eliminating the need for redundant perimeter cooling units
- Lower energy costs by avoiding the over-provisioning of perimeter cooling units, many of which have fixed-speed fans that chew up energy
- Lower maintenance costs by eliminating maintenance contracts for perimeter coolers
To understand how row-based coolers support these ancillary loads it’s important to understand that row coolers are variable capacity devices that are capable of over-supplying cold air to the cold aisle. Normally they supply just enough cool air to deal with the IT equipment in the row. But when additional heat load is added outside of the rows due to the ancillary equipment, that will raise the temperature of the overall room environment. The row coolers will sense this increase and respond by increasing cooling capacity. Because that increased capacity will be greater than what’s required to cool the IT equipment in the row, the excess begins to flow into the rest of the room, cooling the ancillary devices.
The strategy works even when containment units are in place. In this case, the row coolers still see the increase in room temperature caused by the non-row equipment and increase their airflow and capacity as a result. The contained row becomes a net generator of cool air from the room perspective, and that cool air causes mixing in the room that holds down the temperature of the ancillary equipment.
Now, it’s to be expected that the ancillary equipment will operate at a slightly higher temperature than the row equipment, because it is not coupled as well to the row coolers. But many times the supply temperature of the row-based coolers is set well below what the IT equipment can tolerate, such as ASHRAE’s recommended maximum of 80.6°F. In such a case, a small temperature rise of the ancillary equipment is acceptable and may be no worse than the temperature rise if a traditional raised floor system was installed.
To learn about the computational fluid dynamics modeling that proves this theory is sound, check out the APC by Schneider Electric white paper “Cooling Entire Data Centers Using Only Row Cooling.”
We’ve also created a web-based “TradeOff Tool,” called InRow Ancillary IT Equipment Cooling Calculator, to help you determine if ancillary loads can be supported by row-based coolers in your data center, given the room geometry, IT equipment, and cooling configuration attributes. We hope you’ll find it helpful.
