Slightly OT: Calculating HVAC requirements for server rooms

Joe Greco jgreco at
Sat May 2 08:28:38 CDT 2009

> On Fri, 01 May 2009 21:32:19 -0400, William Warren  
> <hescominsoon at> wrote:
> >> Specifically, I am using the guide posted at:
> >>
> "Before you decide on an air conditioning unit you should commission an  
> audit from a suitably qualified air conditioning equipment specialist or  
> installer."
> Translation: Hire a f***ing professional.
> And that's exactly what you need to do.  Qualified HVAC installers (with  
> specific data center experience) will know far more than us "network  
> types" will ever want to know about cooling.  They do this for a living,  
> and thus, know all the tiny details and odd edge cases to look for. (like  
> looking above the drop ceiling -- that's what it's called, btw -- and  
> seeing what's up there long before pencil meets paper (not that anyone  
> uses paper anymore.))


> Bottom line, again, ask a professional.  NANOG is a bunch of network geeks  
> (in theory.)  I'd be surprised if there's even one licensed HVAC "geek" on  
> the list. ('tho I'm sure many may *know* an HVAC engineer.)

The problem is that you're ultimately responsible for determining the
competence of that "professional."  I've seen a number of them who have
talked about their "data center" experience, when it turns out that their
idea of "data center" is "I went down to $FooCo and set up their 200 sq
ft of server room with a mini-split system".

So, here's better advice.  Take some time.  Educate yourself.  There's a
ton of useful information out there that should give you some basic grasp
of what's important and what's not.  Airflow and BTU are important.  Do
not be afraid to get into it a bit: learn what "latent" and "sensible" 
mean in the HVAC world.  Knowing about realistic layouts for data centers 
is important.  If you run into a "professional" that looks at you funny
when you say "cold aisle," you know that you can wind up the conversation
and thank them for their time, and then call someone else.  But when you
find the right guy, you should be able to hold an intelligent conversation
with him, he should be able to make plausible and reasonable explanations
of where you've misunderstood things, and the best guys will not mind that
you are trying to work with them closer to their level, because ultimately 
it means that their task is also more likely to be successfully completed,
and that you'll be coming back to them in the future.

Best to not just blindly hand things off to a "professional."  Be sure
that they do, in fact, have the skill sets and experience you need.  Know
too that they are relying on you for critical bits, and that the best
situation for both parties is when you each understand the other's stuff
well enough that you can actually get the right thing done.

... JG
Joe Greco - Network Services - Milwaukee, WI -
"We call it the 'one bite at the apple' rule. Give me one chance [and] then I
won't contact you again." - Direct Marketing Ass'n position on e-mail spam(CNN)
With 24 million small businesses in the US alone, that's way too many apples.

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