nanog mailing list archives

Re: Why choose 120 volts?


From: Joe Greco <jgreco () ns sol net>
Date: Wed, 27 May 2009 18:40:39 -0500 (CDT)

On Wed, 27 May 2009, Seth Mattinen wrote:

Here's the L-G voltage off the 208v taps from an isolation transformer in a 
system with no neutral: http://ninjamonkey.us/not_120_volts.jpg

Not 120, but 90 give or take.  90 is at the low end of the acceptable 
range for common household 110/120v service.

Yeah, but that's L-G voltage (geez, did you even look at the picture?)
And Seth just finished telling us that it was 211 L-L:

Seth > "The L-L voltage on that same PDU is 211."

What's going to be presented at the neutral and hot of the 5-15R of the
monitor power adapter are the L and L.  Think about it.  Or get out a
meter and test.

Depending on how the phases are balanced in your facility, you may see 
that fluctuate up or down, of course.  If you measure hot to hot on the 
same PDU, do you get anywhere close to 208? 

Yes, Seth just finished telling us that in the portion of his message you
conveniently snipped.

I'm going to suspect either 
your fairly out of balance, or you've got a good bit of voltage drop by 
the time it arrives....

But since the concensus from those who haven't used this is that the 
device will present 208/240 at the 5-15 plug, I withdraw my suggestion and 
leave you to your own methods.   (for the rest, test it yourself)

For those of us who *have* used this, we're telling you that it'll present
208/240 at the 5-15R.

I also won't argue using ground for neutral, that's like arguing bonded vs 
unbonded panels.

No it's not.  Only idiots argue for using ground for neutral.  In doubt?
Ask your electrical inspector.

... 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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