Want to move to all 208V for server racks

Sat Dec 4 22:52:09 UTC 2010

> Date: Sat, 4 Dec 2010 23:26:46 +0100 (CET)
> From: Ingo Flaschberger <if at xip.at>
> 
> > There's also a telco oriented 48V inverter rack system thats escaping
> > my mind at the moment.  It can be setup with A/B 48V strings, and you
> > plug in inverter modules up to IIRC around 8kW.  Not parallel capable
> > between racks AFAIK.
> 
> 48V (and some more when batteries are full) are slightly below the limit 
> of non harmfull voltage.
> 
> Thus you have a voltage with less power loss at short transports and a 
> secure voltage. (creating a short is still not a great idea).

Saying that 48V is not a harmful voltage is a very dangerous
statement. It is unlikely to be a threat of electrocution (though even
that has exceptions), but people have lost fingers to 12V systems.

Lead-acid batteries can deliver way over 100 amps of current and a
conductor across "safe" voltage will get hot and, if not heavy enough,
will vaporize. The temperatures attained can cause major burns and,
should the metal vaporize, can damage tissue so severely that fingers
have been lost when the blood vessels were cauterized.

While safety rules often list voltages under 50 as being safe, it is
still important to exercise caution like removing rings, bracelets and
the like.
-- 
R. Kevin Oberman, Network Engineer
Energy Sciences Network (ESnet)
Ernest O. Lawrence Berkeley National Laboratory (Berkeley Lab)
E-mail: oberman at es.net			Phone: +1 510 486-8634
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