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Posted to uk.d-i-y
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Server room rack power
wrote:
Ok, not strictly D-I-Y i know, but I have been asked to come up with
some specs so that we can get quotes for a new power supply for our
server room at work.
W have 3 tall racks (30U from memory) round about 6 - 7 feet anyway
which are mostly stuffed full of Dell servers. These are rated at 2
Amp (The 1U jobbies) and 5A (2U jobbies). I don't know if this is the
maximum they draw at start up, or if they may take more at startup.
What I do know is that the 30A breaker which feeds the radial circuit
they all go back to (via a few UPSs) trips out if the power comes back
on after an outage
This can be a bit embaressing if we are all asleep in our beds and
there is a power cut. The sequence goes something like
Power goes off,
UPSs continue to power equipment
Backup generator kicks in
MCB opens
large inrush current from switched mode PSUs
UPSs keep the servers up for 10 or 15 mins
Then everything goes down.
If we are here when it happens, we just put the breaker back in while
the UPSs are holding up and live to fight another day.
Anyway, to the question (I hope I haven't asked this before, I
couldn't find it via google) Is there a rule of thumb for specing
power supplies for these racks? Based on the rating plates, I could
allow 2.5A per U, but I don't know if I need to allow extra over what
it says on the rating plates of the servers, or if Dell have already
done that. Does 60A per rack sound about right, way over the top?
Way under?
Assuming it is right, what would be the best way to provide it? A
number of 16A or 30A Industrial sockets?
I'd be tempted to split the load across multiple 16A outlets, to reduce
the total inrush current per circuit, also switch to type-C MCBs.
Alternatively consider intelligent power distribution strips which can
sequence the servers back on after any power cut, and have the advantage
you can remotely power them off/on if required.
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