Thanks to industry leaders and groups like ASHRAE, best practice in data center HVAC has come a long way. Unfortunately, many older data centers and telecom facilities are cooled with constant-speed computer room air conditioning (CRAC) units with simple controls.
The constant-speed fans in an older computer room unit can use a shocking amount of electricity (pun intended). At 10 hp, a single computer room unit fan can cost $9,800 in electricity per year if run continuously. Adding insult to injury, all of this power generates heat: Heat that needs to be removed by the A/C circuits in the CRACs, or by the chilled water plant, potentially increasing annual costs to $12,000. It’s not unlikely that a single CRAC unit may be introducing more heat than your hottest rack.
But the CRAC needs to run, right?
Not necessarily. Often, redundant CRAC units have been installed. The simple controls in many older data centers and telecom facilities will happily run CRAC units whether they are actually needed for cooling or not.
The CRAC unit in the photo above is not cooling. If the CRAC is running, but not cooling, it is just burning energy. Control adjustments, air balancing, and software changes can often reduce the number of operating CRACs in the data center while keeping your rack inlet temperatures at allowable levels.
Next time you are in your data center, take a look at your CRACs. Are any of these units running, but not doing much cooling? Can any of them be turned off, shifting load to the remaining CRACs while keeping rack inlet temperatures within allowable bounds?
Worse yet, are any CRAC units heating? Believe it or not, this happens.
Optimizing operation of these legacy data centers can sometimes be counterintuitive, and minimizing fan energy is often the most important strategy. G/BA has extensive experience in new and existing data center and telecom space design, energy audits, and commissioning. Feel free to reach out to us if we can be of assistance: info@grummanbutkus.com.
