Why choose 120 volts?

Joe Greco jgreco at ns.sol.net
Tue May 26 15:39:30 CDT 2009

> I have a pure curiosity question for the NANOG crowd here. If you run
> your facility/datacenter/cage/rack on 120 volts, why?
> I've been running my facility at 208 for years because I can get away
> with lower amperage circuits. I'm curious about the reasons for using
> high-amp 120 volt circuits to drive racks of equipment instead of
> low-amp 208 or 240 volt circuits.

208 isn't all that great.  On one hand, a 20A 208V circuit is vaguely
more convenient than a 30A 120V circuit because it is delivering a bit
more power to the rack (3328 vs 2880), and it's likely to work with a
lot of modern equipment containing autoranging power supplies.

On the flip side, with 120, you don't have to have "odd cords," and it
is somewhat easier to "right-size" power for a rack (20A, 30A, 2x20A),
so for an average rack that isn't crammed with high power webhosting
1U's (etc), a customer might actually find that the ability to right-
size the power feed is more flexible with 120V.

And I don't like not having anywhere to plug in my power screwdriver's
recharger...  I suppose I should see if I can find someplace that has
a transformer of an appropriate size, or does anyone already have the
part number for something that can provide a few hunderd milliamps of
120V from 208?  :-)

... JG
Joe Greco - sol.net Network Services - Milwaukee, WI - http://www.sol.net
"We call it the 'one bite at the apple' rule. Give me one chance [and] then I
won't contact you again." - Direct Marketing Ass'n position on e-mail spam(CNN)
With 24 million small businesses in the US alone, that's way too many apples.

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