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

[Alex Rubenstein <alex () corp nac net>]

> > GFCI breakers are often required on large services, most large (new)
> > 480v services I have seen (1000A and larger) a have Ground fault
> > breakers,
>
> Actually, my recollection is that large new services include arc suppression
> rather than ground fault (480V service may be floating in any case, since it
> would depend on delta-wye distribution).  There has been strong efforts to
> protect the low voltage electricians (in common power distribution speak,
> 12K+ voltage is high voltage, less is considered low voltage; yes, this is a
> different point of view).  Even with a 100Cal suit on, you really want arc
> suppression at those high joule ratings to protect a life (every master
> electrician has a story about arc flashes, and some stories include the outline
> of the ex-individual on the opposite wall).  It is now common when doing
> work on downstream devices to reduce the arc limits so that ones life has
> increased protection.  A protective trip is better than the alternative.

Don't confused arc-flash protection with arc-flash circuit breakers. Doesn't sound like you did, but I said it anyway.

As far as ground fault protection, in the 2008 NEC Code, it is required on any service 600 volts or less, 1000 amps or 
more, per 230.95.

As an aside, generally it is accepted that 600v and less is 'low voltage' (not to be confused with telecom/datcomm low 
voltage); 1kv to about 35kv or so is medium voltage, and above that is high voltage. I think IEEE or ANSI or someone 
defines this. Google around.

Arc flash is a whole new requirement, generally for the life safety aspect of the operators of the electrical 
equipment. I love putting on a arc flash suit to close a 800 amp breaker, when in the old days we'd do it barefooted on 
a damp floor. Maybe it wasn't smart, but some of the new arc flash stuff is a bit ridiculous.