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#1 (**permalink**) 01-16-2008, 04:05 PM

After the initial power-on spike - using a 110V power strip with
readout shows the X4100 drawing 2.0 amps. But when I plug the same
device to 208V (one branch of a 3phase 208V circuit) - the draw is
1.8V. Yet by rights I would expect the draw to be closer to 1.1amps
given that Watts=volts x amps and power consumption should remain
constant. Even if the first power strip is actually operating at 120V
I would expect to see amp draw no more than 1.2amps at 208V. Am I
missing something?

Thanks.

#2 (**permalink**) 01-16-2008, 04:05 PM

"amigan" <mmedwid@gmail.com> writes:
>device to 208V (one branch of a 3phase 208V circuit) - the draw is 1.8V.

(assuming that should be 1.8A).

Your statement doesn't make sense.

A 208V circuit is two branches that are 120V each, and the RMS
difference between the two works out to be 208V between the two
phases of the 3-phase power.

If you take one leg of a 208V circuit, you have a 120V circuit???

Power should be conserved.

If you feed it 120V, it sucks 2A, you're using 240VA.
If you feed it 208V, and it sucks 1.15A on each leg, you're using 240VA.
(more or less).

I sure see it day-to-day, when most of my customers average usage of
about 12A or so on 20A 110V feed, but average usage of about 6A on
each 2 phases of their 208V feeds. Nobody's brought in a fully-loaded
blade server yet, waiting for them start sucking 15A on each phase...

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Amp Draw with X4100s 208V vs 110V