Computer room AC unit - vendor?

[nahoku]

We have been reviewing estimates we have received and I was wondering if you could help me ballpark the cost of the unit for our new computer room. We are looking at 15 ton units, something like the Liebert systems. Do you have a ballpark price range for such units? Are there other manufacturers and types of systems that you could recommend?

Our system is a 100-node computer cluster, small room (11x11 feet), and our work is not missing critical and does not need 24/7 guarantee. However, we want the most economical approach possible, as we are trying to save money (academics, what else) but still build a solid system. We have been recommended to look at the Lieberts, but they seem to be fairly expensive.

Thank you.

 

[new2hvac]

I suspect the cost of a new, 15-ton Liebert is about $25,000 - 35,000 depending on the options you require (humidification/reheat, advanced microprocessor, etc.). The installed cost of this unit could be significantly more depending on the amount of condenser water piping or refrigerant piping, amount of ductwork, electrical requirements, etc. required for your particular installation.

There is a market for previously-purchased Lieberts. Many of the telecom and .com companies purchased these units during the boom years and never installed them. You can purchase these (new and in their original packaging) for about 50% of the price of a new unit.

There are also other manufacturers that can provide more competitive pricing than Liebert; Data Aire, Stulz, United Cool Air are a few that I'm aware of. I truly believe that Liebert provides superior quality and will result in fewer problems in the long run.

 

[lilliput1]

That is a large cooling load for a small room. This unit will take up about 25% of the room and is too large to be ceiling hung. Check your loads! A 15 ton unit in a 11" x 11' room can handle about 390 watts/SF!

 

[nahoku]

Hello,
well, I went back to my numbers and according to the specs, each of our nodes is rated at 405Watts max output. If they are running at 70% of the max (most of the time computer nodes to not run at 100% all the time), then this would translate into 283 Watts per unit. Multiplied by the 100 units plus the additional 17amps@115V for the other equipment that's 30,255 Watts . I multiplied this by 1.4 to account for the extra power in the AC system, and came up with approximately 42,357Watts that equal to about 12.1 tons of cooling. I am not sure if this the correct logic, I was trying to follow the other threads and information that I obtained about computer cluster room cooling systems.

One of the people that I have talked to said the room will be extremely windy, the air would be exchanged in it 12 times per minute (?!) and that I should start thinking about lead shoes when I will be administering the system. We have been recommended a 17-ton system for a total install cost of over $75K. That sounded really overextended to me, but I am a computer expert, not an AC one, unfortunately.

I will definitely look at the other systems that you mentioned above and the possiblity of purchasing a new, unused Liebert that is still in a box somewhere!

Your help and insights are appreciated!

 

[lilliput1]

A watt is 3.413 Btu/hr AC or DC so you don't need the 1.4 factor and can reduce the equipment size. Consider underfloor air distrubution because of the high load density. Allow service space around the AC equipment & the nodes. You may have to increase room size.

A 10 ton air cooled computer room unit will cost about $40,000 including electrical. Glycol cooled unit would be about $50,000.