Want to move to all 208V for server racks

John van Oppen jvanoppen at spectrumnet.us
Thu Dec 2 13:20:39 CST 2010

It is probably worth nothing that a 3-phase input in Europe is actually 240/415 volt Y (for every panel I have seen in Germany at least, even the places I have lived there had 240/415 three phase).   The normal 240v single phase outlet circuits were the phase to neutral voltage.   Obviously Europe also runs at 50 hz vs 60 in the US as well but the three phase still works the same way.

A Europe 64 amp 240/415 circuit is pretty close to equivalent in to a 277/480 Y configured 60 amp circuit in the US.   The biggest notable difference is that equipment that runs on two different service voltage ranges where Europe has far less need for in-building step-down transformers since even small loads work on the phase-to-neutral voltage of the big services.   I always find it interesting in the US to note how many 480v to 120/208Y step-down transformers one can find in a big building or datacenter.


-----Original Message-----
From: Ingo Flaschberger [mailto:if at xip.at] 
Sent: Thursday, December 02, 2010 10:08 AM
To: Kevin Day
Cc: NANOG list
Subject: Re: Want to move to all 208V for server racks

> 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.

that one looks dangerous.

In europe:

64A 240V 3-Phase input.
Out to Servers single phase, output to airconditioners with 3 phase (not 
at this picture).

Kind regards,
 	Ingo Flaschberger

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