[132872] in North American Network Operators' Group
Re: Want to move to all 208V for server racks
daemon@ATHENA.MIT.EDU (Kevin Day)
Thu Dec 2 12:52:01 2010
From: Kevin Day <toasty@dragondata.com>
In-Reply-To: <1411250A-38F8-4099-89D4-616D6633F218@delong.com>
Date: Thu, 2 Dec 2010 11:51:42 -0600
To: Owen DeLong <owen@delong.com>
Cc: NANOG list <nanog@nanog.org>
Errors-To: nanog-bounces+nanog.discuss=bloom-picayune.mit.edu@nanog.org
On Dec 2, 2010, at 11:06 AM, Owen DeLong wrote:
> It is not uncommon for three-phase panels to be different and have
> all three phases in the panel each phase feeding every third breaker
> slot.
I was just recently trying to explain this to a European friend who =
thought I was hallucinating this system, so I took a picture.
http://dl.dropbox.com/u/230717/temp/208YPanel.jpg
That's a picture of one of the breaker boxes in our office, showing what =
you described. There are 3 phases coming into the panel, each a =
different coil off a Y transformer, as well as a "neutral". Those are =
the 4 black wires you see at the bottom. You can see how the three hot =
phases are staggered as they go up the breaker rails.
For standard 110V service, you use a single-wide breaker and send one =
hot phase + neutral and you get 110V. The difference between two phases =
is 208 volts though, so you use a double wide breaker and can send to =
device without using a neutral wire. Just 2 hots and a ground. If that's =
all you're doing (you don't need legacy 110V service anywhere) you skip =
the ground wire going into the panel entirely.
-- Kevin
