Want to move to all 208V for server racks

Thu Dec 2 17:58:56 UTC 2010

On Thursday, December 02, 2010 11:46:28 am Leo Bicknell wrote:
> You may also find this arrangement in larger multi-tennent buildings
> where they are fed with 3-phase power.

There are two other 3 phase setups that are somewhat common.

120/240V delta (has the third leg 'wild' at 208V to neutral, with the neutral (grounded conductor in NEC parlance) connected to a centertap on one transformer of the three required).  This one has special labeling requirements and a prohibition on single-phase loads being connected to the 208V leg.  This one is sometimes provided in a two-transformer 'open delta' arrangement (instead of the correct three-transformer 'closed delta') and is, you might say, 'three phase lite' in practice.  

480V delta corner ground.  This one is 480V three phase on three wires; one phase is grounded at the service entrance, and the other two phases are 480V to ground.  This one also has special labeling requirements and no 'neutral' in the conventional sense.