On Fri, 20 Apr 2001, Geoff Roberts wrote:

> 
> ----- Original Message -----
> From: "Anders Hogrelius" <ahs@hogrelius.nu>
> To: "Gunther Schadow" <gunther@aurora.regenstrief.org>
> Cc: "Sridhar Ayengar" <sridhar@ikickass.org>; <port-vax@netbsd.org>
> Sent: Saturday, April 21, 2001 2:31 AM
> Subject: Re: Three Phase
> 
> 
<big snip>

Any other electricians out there?  I'll take a stab at a few of these, then.

Normal US House power is 240 single phase, with a center tap, yielding a
neutral (the centertap) that is bonded to ground at exactly one point (the
first disconnect, generally a main breaker panel, or perhaps a disconnect
mounted outside the house).  Available voltages are 120 volts hot (either,
known as A-leg (black) and B-leg (red) around here) to neutral, and 240
volts A-leg to B-leg.  It is true single phase.  The nominal voltage may
vary, generally anything from 110-120/220-240 is acceptable. 

208 volts is the hot-hot voltage derived from a 120 volt-to-neutral
wye-connected three phase service.  I've never seen one of these on a
house proper, altho larger apt/condo buildings may have them.  

more tonight...
ja ne

Bob