Get personalized answers from home improvement experts We've got a small server room ( approximately 600 square feet in area ), and three partially-filled racks of servers, switches, et cetera. What's the best-practice way of computing the AC capacity needed to hold temperature/humidity conditions constant in a server environment? Our current AC unit was installed about 10 years and 12 servers ago, and despite regular visits from the helpful physical facilities staff-- it's unable to hold temp/humidity without overheating the compressor. Right now, I've got the estimated power-draw of the servers, switches, etc--- but I can't find a good way to take that power usage and determine cooling needs from that. Any help/directions would be appreciated. Just convert the estimated draw from Watts to BTUs: To calculate the BTUs/hour, multiply the watts by 3.413. 1 ton of cooling is equivalent to 12,000 BTU/hour. Most of the energy drawn will be converted to waste heat.

From what I am reading, a pro would tell you to have someone come in and do the full calculation. That would take into effect any odd heat sources (solar for example) and your humidity concern. In practice - I have just oversized mine by 25% or so in the past - to allow(In a small equipment room!) I would also STRONGLY recommend you pick up this book: Even though it is from 2002, it is still very relevant today. It is all about A/C, power, rack load, rack placement (cold aisle/hot aisle), good housekeeping, cabling runs, etc. for a datacenter. Yours is a good question.. Here's a link that might help you, and another one that could be of some use. To be completely honest, this is something that I've seen a.) tackled by server admins and IT managers with the best of intentions yet yielding the worst results :) and b.) honestly better left up to HVAC/building engineering/facilities professionals who know the right questions to ask and what to think of.

I do, of course realize that you may not have that option though. Please consider that many now believe that it's cheaper, quicker and more environmentally-sound to use fans to extract warm air from a data centre and draw in ambient air from the outside (via some form of filtration at least). Most, if not all, IT kit is designed to be ran at ambient temperatures, not the 17-10C we all seem to feed them. As an example look at Switch Communications new enormous data centre - there's no AC at all, it saves them a fortune - and they're in Nevada so it clearly works even in hot and dusty surroundings.Browse other questions tagged server-room physical-environment or ask your own question.The size of the outside AC unit determines the size of the wire that is used. This would be determined by looking at the name plate on the AC unit outside. The larger the tons, the larger the wire size and breaker. Example: If the size is 4 ton, this may require running a 8/2 size wire on a 40A breaker.