"asta" wrote in message
...
hi!
i've always wondered what phase-shift there is between those two 110V
lines in an USA 220V AC net system.

I think the answer to your question is either no phase shift or 180 degrees.
(The two conductors you mention are the two ends of the same phase!)
To explain; coming into the typical North American residence is a three wire
service.
The three wires are the two ends of and the centre tap of a single phase 230
volt secondary winding of the power utility distribution or step down
transformer located nearby. Note 1.
Thus there is 230 volts single phase between the two outer conductors or
legs and 115 volts between each of them and the centre tap. The centre tap
is grounded/earthed at the transformer and again (once only) where the
service enters the house.
It becomes the neutral or zero voltage wire.
Some people, including electricians, incorrectly refer to the two outer
conductors, each at 115v to neutral, as 'Phases'!
They are not and a more understandable designation is 'Legs'.
Typical colour coding is Leg A = Black, Neutral = White, Leg B = Red.
Although this is AC you can, sort of, think of it as Black = Plus 115 volts,
White = 0 volts, Red = Minus 115 volts.
Within the house heavy appliances that require considerable wattage, such as
a water heater or cooking stove are connected to 230 volts through double
pole breakers. (Some also have 115 volt items, e.g. an oven light, so also
use the neutral wire.
Everything in house has a ground/earth (bare or green) wire; which does not
carry any current for safety.
The 115 volt loads comprising lights and outlets are distributed over both
legs in a hopefully balanced manner through single pole breakers. It works
well and the maximum voltage to ground or neutral is 115v AC RMS.
If you want a comparison; think about those single phase safety transformers
they often use now on British construction sites, with 115 volt tools. As I
understand they step down the normal 230v to 115v, that in itself is less
voltage. The centre tap of the 115 volt secondary (again as I understand) is
grounded. Thus the maximum voltage to ground is half the 115 volts. That's
57.5 volts RMS and about 81 volts peak; much safer eh?
So our North American residential service is, sort of, similar.
Any help?
In commercial work you may get into three phase, one voltage used is 347
volts AC RMS e.g. lighting in a say a supermarket.
Note 1. A typical 'primary' distribution voltage from the subsation some 5
kilometres away is around 12.7 kilovolts. The lane behind our house has a
single phase 2 wire (live plus neutral) primary; various step down
distribution transformers supply groups or individual houses each with a 3
wire 230 volt centre tapped supply. In this area it is all overhead. While
o.head distribution can be more easily damaged by weather it is much quicker
to repair than underground plant, imagine moving three feet of snow and then
digging into frozen ground! And maybe breaking the telephone cable while
doing it! The poles are shared with telephone and TV cable systems. Thus in
quite small communities we have a choice of internet service from the cable
TV provider via their coax, or ADSL from the telco, or dial up over regular
telephone etc. In competition with cable TV (analogue and now also digital)
we now have two Canadian satellite systems and in many areas of Canada
people can subscribe to US satellite services as well.
Long winded answer but hope it helps.
Terry.