Should I use a centrifugal or axial fan for server room ventilation?

Question

First of all I know this is a strange one.

We have a server room which is small and a few servers in there. We have an AIR CON in there but we also have a ventilation duct which is a follows:

9 Meter Length x 600mm x 200mm

I would like to know which fan would be best for ducting. I have been told that a centrifugal blower would be good but I am not sure.

Please note this is a DIY job the idea is just to get rid of the hot air from the servers to outs side.

Best in what way? Lowest operating cost, most effective at removing hot air, etc. — Tester101, Nov 12 '12 at 20:19
This is a border line question that may be more appropriate for Server Fault due to the context. (Note, this isn't a suggestion to cross post, if it needs to be moved, we'll migrate it.) — BMitch, Nov 12 '12 at 20:23
@Tester101 Both, but if I had to choose. Lower operating cost as it will be only more than the air con. — Arthor, Nov 12 '12 at 20:23
@BMitch I would rather not. The question is about the fans types. Server fault do not know this because they use professional HAVC systems. — Arthor, Nov 12 '12 at 20:24
I agree with @Arthor, this is more relevant here. I've designed whole data centers and I have no idea. — GdD, Nov 12 '12 at 20:34
Thanks @GdD, that seems to be consistent with the opinion of the Server Fault mods, too. — BMitch, Nov 12 '12 at 20:37
If you have A/C, wouldn't the vent be sucking out as much warm air as cold air? — DA01, Nov 12 '12 at 20:57
If the servers are airtight, then perhaps that's the problem? ;) — DA01, Nov 12 '12 at 22:57
@DA01 LOL. I mean the air coming from the back is directed to the ducts. — Arthor, Nov 13 '12 at 00:47

score 1 · Answer 1 · answered Nov 12 '12 at 22:09

Is this a datacenter (raised flooring, proper precision air conditioning, fire suppression, etc.), or a server room (tiny space with heat producing machines that happens to have its own AC unit or duct leg)?

If you're talking about a small server room all you want is a fan that moves the volume of air you need to move through the length of duct work you need to go through, and preferably does it quietly enough not to annoy anyone.

As a general rule direct exhaust (or short straight duct runs) can use either type of fan, but for longer ducts, curved/bent ducts, or anything else that's going to increase resistance to airflow you want the extra force centrifugal fans generate.

Also as some folks mentioned in the comments, make sure you're pulling out hot air and not messing up your airflow -- cool air should be blowing in to the front of the servers, and the exhaust system should be pulling hot air from behind them.
A draft detector (or a cigarette if you're so inclined) can be useful in making sure air is going where you want it to (test with your AC on and off).

If you're talking about a real datacenter with raised floors and precision air conditioning you I beg you not to do this (or at least don't DIY) -- Proper datacenters are usually sealed environments, and adding exhaust systems to blow off hot air has lots of fire suppression and climate control implications.

Codes vary, but most datacenters use clean agent flooding for fire suppression, so exhaust systems have to have integration with the fire alarms (usually electro-mechanical or magnetic drop-dampers). That integration is a job for a licensed and insured HVAC contractor, because if something goes wrong your insurance company is going to want to sue somebody and you don't want it to be you :)

Although it does sound like this is for a "server room", the datacenter information cannot be stressed enough. — ND Geek, Nov 16 '12 at 16:11

Should I use a centrifugal or axial fan for server room ventilation?

1 Answers1