[rescue] Big computer, single phase, three phase

Robert Darlington rdarlington at gmail.com
Fri Feb 12 13:04:30 CST 2010

Safety first, be very careful.  You won't get a second chance.

That being said, this is okay to do and encouraged to keep the phases in
balance.  Read up on grounding and bonding.  Bond all supplies together.  DO
NOT let the neutral float or you can fry equipment or yourself with over

Double check your voltage between L1&L2, L2&L3, and L1&L3.  Double check the
voltage between each phase and neutral (which is tied to ground at the
breaker box / load center ONLY) to be sure you're running at the voltage you
think you are.  This has saved my butt a few times when I discovered I
needed to go to a step down transformer to get the 240 V single phase I was

Consult the NEC.

Did I mention you should bond your supplies together?  Call me if you need


On Fri, Feb 12, 2010 at 11:28 AM, Ethan O'Toole <ethan at 757tech.net> wrote:

> Years ago when I worked at NASA most of the ~220 systems were setup so all
> the cabinets shared the same set of legs from the AC feed.
> Are there any issues if I have a 3 cabinet system that uses 240 single
> phase, with putting each cabinet on a different set of legs?
> System has 3 240 (or 208 or whatever) vac single phase inputs. I was
> thinking of doing leg A to B, B to C, C to A for each part.
> Outside of the obvious issues if a phase dies and such, anyknow know if
> there should be much of a problem doing this? It's not production. The
> machine just drives a bunch of DC power supplies anyways.
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