Want to move to all 208V for server racks

Fri Dec 3 04:58:37 UTC 2010

> 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 requirement. Perhaps Sq-D or Eaton paid the NFPA/NEC to put this in the code to sell 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 "engineering supervision." In fact, it is quite normal to have GFI Alarm on the generator mains, so as to prevent you from having a nuisance trip when you transfer to emergency power.

As to the second part of your paragraph, that would be discovered (hopefully) in the commissioning process, where you have your coordination studies done. 

Anyway, back to topic: Vendors, please a) get all your gear to cool front-to-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.