While all the below is true, I would put forward that many of us networking types, especially those who operate their own datacenters, generally know how to do an approximation. Afterall, if you don't have an idea of magnitude, if you haven't done your homework, your conversation with that professional will not go well. So it is appropriate for someone being tasked with researching cooling for a datacenter to learn how to do these approximations. My $0.73. (inflations's a bear.) -Wayne On Fri, May 01, 2009 at 09:22:24PM -0700, Seth Mattinen wrote:
Ricky Beam wrote:
On Fri, 01 May 2009 21:32:19 -0400, William Warren <hescominsoon@emmanuelcomputerconsulting.com> wrote:
Specifically, I am using the guide posted at: http://www.openxtra.co.uk/articles/calculating-heat-load
"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.))
You also have to take into account the environment surrounding the data room. At my wife's work The ceiling above is only separated with a false ceiling to the metal roof above but the rest of hte spaces surrounding the room are climate controled. They [had] to significantly upsize to account for the heat load of that ceiling.
Unless you are pulling air through the plenum (that space above the drop ceiling), the air up there shouldn't matter much -- there should be plenum returns up there to begin with venting the air to the surrounding plenum(s) (i.e. the rest of the office, hallway, neighboring office, etc.) However, I've seen more than enough office setups where the "engineers" planning the space completely ignore the plenum. In my current office building the static pressure pushes the bathroom doors open by almost 2". And they placed our server room directly under the building air handlers -- meaning all the air on the 3rd floor eventually passes through the plenum above my servers. (also, the sprinkler system riser room is in there.)
The space above the drop ceiling is only a plenum if it's used as air handling space opposed to ducting the returns everywhere. If it's not an air handling space, it's not a plenum, it's just where spiders might be. It's easier to throw grated panels in all over the place for returns in large systems.
Now, back on topic, plus nifty graphics explaining the difference:
http://en.wikipedia.org/wiki/Plenum_cable
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.)
But yes, please, don't learn how to make your own system from what we say here. HVAC systems are their own world. You wouldn't want an HVAC guy designing your network just because he's seen a lot of server rooms, would you?
~Seth
--- Wayne Bouchard web@typo.org Network Dude http://www.typo.org/~web/