> At 03:47 PM 6/2/2006 -0600, you wrote:
>>I was asked to repair some EXIT signs ( in Colorado, USA ) in an office.
>>
>>I discovered the sign was being fed 280VAC.  This was stepped down
>>to 120VAC for the lights in the sign.  Is this a common practice ?
>
> No, but 208VAC is. (sqrt(3) * 120VAC)

What the above means is that 208VAC is the phase-to-phase voltage on a three 
phase system with 120VAC phase-to-neutral.

This is commonly used for lighting in industrial/commercial settings.

IIRC, another common industrial practice is a three phase system with 
nominal 480VAC from phase-to-phase and 277V from phase to neutral. This may 
be what you are seeing.

Bob Ammerman
RAm Systems



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