Addressing HVAC in IT Server Rooms
Todd Simkins, BOC graduate and Facilities Engineer for Providence Health & Services, conducted a detailed analysis of IT server rooms for the company’s Everett, WA facility. The server room on the Colby Campus already had difficult cooling issues but it was evident that the system required expansion, which would tax the current set up even more. Most businesses lifelines today revolve around computing capacity and keeping equipment at steady, cool temperatures ensures a more reliable and long-lasting system.
The server room was not being used according to the original design intent, with the then-current one-row utilization less efficient than the original two-row design. There were complaints that the room wasn’t being supplied with enough cooling but to be more accurate, as Simkins concluded, it was the equipment, not the room, that needed the cooling and it wasn’t getting it.
As an evaluation starting point, Simkins focused on the general considerations for server or data center design: room size, cooling required versus total projected heat load, power needs and power backup. He observed, “Many server rooms feel cold which can be a huge waste of energy. The focus should not be the room but rather the air temperature going into the equipment and the temperature coming out of it. Occupancy comfort is secondary.”
What Simkins found was that there were many structural set ups in the server room that could be easily and inexpensively adjusted to create a greater air flow efficiency. Exhaust ducts were improperly located and were cooling the air as it left the room rather than the reverse. The original two-row design for equipment had been changed to a one-row setup. As a result, 82.8% of the cooling capacity was being wasted.
“Cooling a room in general is a brute force approach to server room cooling and is a bad way to operate. It is inefficient and also causes hot spots where the equipment will overheat. So, one wastes more energy and gets less of what is expected. Most of our changes were directed at air flow, redirecting to the equipment (cold isle) instead of the room in general. It is a great example of being energy efficient with little added cost and larger savings,” Simkins observed.
The major changes made to the room were:
- Repositioning and adding to the supply and return ducts in the proper configuration for a Hot Isle/Cold Isle implementation.
- Installing blanking plates in cabinets.
- Increasing and re-arranging the ventilated floor plenum tiles.
- Sealing holes in the floor plenum tiles.
By directing the air to the equipment (cold isle) instead of the room in general, the efficiency of delivering cooling to the equipment rose from 17.2% to just above 90% over the second part of the project implementation.
Simkins is adamant that there should be a policy to determine proper room temperature for equipment of this kind. “There is a correlation between room temperature, equipment life and energy savings, but for ‘room temperature’ you have to look at the whole picture – both server and occupant level – and adjust air flow accordingly. Without a policy that states what the supply air temperature minimum and maximum are, energy savings become rather ambiguous. The policy should state what the highest temperature can be at the direct server level without adverse effects to the life or performance of the equipment. In terms of room occupants, that temperature could be quite different,” he believes.