Why choose 120 volts?

Joe Greco jgreco at ns.sol.net
Wed May 27 18:40:39 CDT 2009


> 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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