Re: Want to move to all 208V for server racks

[Kevin Day <toasty () dragondata com>]

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. :)
> >
> > 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.
>
> 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. 

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.  


-- Kevin