[132957] in North American Network Operators' Group
RE: Want to move to all 208V for server racks
daemon@ATHENA.MIT.EDU (Alex Rubenstein)
Thu Dec 2 23:58:54 2010
From: Alex Rubenstein <alex@corp.nac.net>
To: John van Oppen <jvanoppen@spectrumnet.us>, 'Chris Adams'
<cmadams@hiwaay.net>, NANOG list <nanog@nanog.org>
Date: Thu, 2 Dec 2010 23:58:37 -0500
In-Reply-To: <AF24AE2D4A4D334FB9B667985E2AE7637AC790@mail1-sea.office.spectrumnet.us>
Errors-To: nanog-bounces+nanog.discuss=bloom-picayune.mit.edu@nanog.org
> GFCI breakers are very common, the slightly less common version are arc
> fault breakers which are starting to show up more as well.
Partly because of a code requirement. Houses burning down, etc. Somehow, we=
all survived for a long time without them, but now there is a huge require=
ment. Perhaps Sq-D or Eaton paid the NFPA/NEC to put this in the code to se=
ll pricier breakers. Yes, I believe in conspiracies.
> GFCI breakers are often required on large services, most large (new)
> 480v services I have seen (1000A and larger) a have Ground fault
> breakers, in fact I have seen some bad outages on entire datacenters
> where the main breakers had a lower ground-fault current setting (for
> tripping) than a branch circuit that had a phase-to-ground fault
> resulting in the main breakers tripping instead of the branch circuit.
> I don't know if the ground-fault breakers are required just in
> Washington (I am in seattle) or if it is a NEC requirement.
I believe it to be any service 1200 amps or larger. And, you don't have to =
have GFI trip, you can have a GFI alarm, especially if you are under "engin=
eering supervision." In fact, it is quite normal to have GFI Alarm on the g=
enerator mains, so as to prevent you from having a nuisance trip when you t=
ransfer to emergency power.
As to the second part of your paragraph, that would be discovered (hopefull=
y) in the commissioning process, where you have your coordination studies d=
one.=20
Anyway, back to topic: Vendors, please a) get all your gear to cool front-t=
o-back, and b) let it take 480 polyphase and not require a neutral. I, for =
one, will be happier. The datacenter of tomorrow (hell, today) require this=
.
