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
