Slightly OT: Calculating HVAC requirements for server rooms

Alex Rubenstein alex at
Sat May 2 08:40:04 CDT 2009

Calculating heat load in a datacenter is pretty easy. That's not the hard part.

Some comments:

> I am curious what formulas/equations folks use to figure out required
> cooling for small datacenters in offices.

The simplest equation to use assumes that you know how much power is going into the room. 

Btu/hr = watts * 3.412

This further assumes that a typical IT load is very inefficient (which they are).. meaning that, for every watt that goes to a computer / server / router, a significant portion is converted to heat (we assume 100% for design purposes).

So, if you have a datacenter consuming 100kw, you'd need 341,200 btu/hr of cooling, or 28 tons of HVAC. Of course, there are other issues (like leakage, windows, doors, humans, lights) but these tend to be a little bit of line noise in a modern datacenter. Also outside environment (is this Quebec or is this Cuba), insulation, design delivery temperature, humidity requirements -- all play a part.

> Translation: Hire a f***ing professional.
> And that's exactly what you need to do.  Qualified HVAC installers

Two comments on this... first of all, the last thing you want is an HVAC 'installer' to design your HVAC system in a datacenter. Secondly, if you find an HVAC engineer who *really* knows datacenter dynamics, that could be a help. But, frankly, there aren't a lot of them.

If you need some help with this, let me know. There are a significant amount of questions that need to be asked to give a qualified answer. The cooling capacity question is secondary to the delivery and extraction method.

I also submit that any good datacenter operator, who has had years of experience of trial and error, years of engineers who say they know something and don't, and had scores of contractors who say they know something and don't, is in a much better position to talk about this than a PE who designs comfort cooling systems.

"Question everything, assume nothing, discuss all, and resolve quickly."

-- Alex Rubenstein, AR97, K2AHR, alex at, latency, Al Reuben --
--    Net Access Corporation, 800-NET-ME-36,   --

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