Want to move to all 208V for server racks

Fri Dec 3 17:09:04 UTC 2010

btw, one thing I do not recall seeing on this thread is that
208v avoids one of the common problems with 120v, which
is the third harmonic issue.

With the cheaper switching power supplies, one will often
see significant 3rd harmonics in the waveforms(*).  The 3rd
harmonic, across a 3 phase circuit, are additive on the
neutral.  In worst case, your (common) neutral current
may exceed the line currents.  Proper engineering for
significant 120v distribution in new DC construction often
requires double sized neutrals to mitigate against this.
Using 208v mitigates this particular issue.

Gary

(*) There are also other harmonics, but for this
    discussion, 3rd is what matters.