[132880] in North American Network Operators' Group
Re: Want to move to all 208V for server racks
daemon@ATHENA.MIT.EDU (Kevin Day)
Thu Dec 2 13:39:35 2010
From: Kevin Day <toasty@dragondata.com>
In-Reply-To: <alpine.LFD.2.00.1012021918290.2841@filebunker.xip.at>
Date: Thu, 2 Dec 2010 12:39:16 -0600
To: Ingo Flaschberger <if@xip.at>
Cc: NANOG list <nanog@nanog.org>
Errors-To: nanog-bounces+nanog.discuss=bloom-picayune.mit.edu@nanog.org
On Dec 2, 2010, at 12:20 PM, Ingo Flaschberger wrote:
>> Err, I meant "skip the neutral wire". It's still grounded. And there =
are normally significantly more covers over the panel than this, there =
were a dozen screws I had to remove to expose all of this. :)
>>=20
>> This is a much smaller scale panel though, not far up from a typical =
home system. The more current you start talking about, the more isolated =
everything becomes until you wouldn't even be able to see the bus bars =
like in this one.
>=20
> are "Residual-current device" (Fi in German) are common in us?
> I use for servers "Residual-current device" and circuit breaker =
integrated in one device; but I try to use the more expensive pulse =
tolerant ones.
They're called "Ground Fault Interruptors" here, or GFI/GFCI.
They're extremely common built into wall power outlets, and GFI outlets =
are required in wet areas (kitchens, bathrooms, hot tubs, outdoors, =
etc). Most wall outlets with GFIs built into them have a "daisy chain" =
system where one outlet in the kitchen has the circuitry and the =
Test/Reset buttons, and it protects all non-GFI downstream outlets from =
it. Downstream outlets usually have a sticker on them saying "GFI =
Protected" which is a hint that if the outlet stops working, check other =
outlets in the room to see if one of them tripped. Newer versions have a =
light that comes on to indicate when they've been tripped, which is =
handy for non-technical people to figure out what happened more easily.=20=
You can get breakers with GFIs built into them(called GFCIs), but =
they're favored less than putting them at the outlet. I haven't seen any =
datacenters using them, but I haven't looked that closely. An =
electrician I talked to once about it felt that the panel mounted =
variety were designed to be less sensitive/slower reacting due to much =
longer wire lengths, but I'm not sure if that's just urban legend, =
experience with a single product or fact. =20
-- Kevin
