"Danny D'Amico" wrote in message ...
On Tue, 19 Nov 2013 18:03:14 +0100, nestork wrote:

I find the first diagram on this web page that was posted by SRN
helpful:

Here's a PNG of that diagram, for reference:
http://farm8.staticflickr.com/7292/1...4ba18de1_o.png

In the dryer thread, it was noted that most USA circuit breakers
are *not* arrayed in AB-AB-AB format; but in AA-BB-AA-BB format.

I'm not sure what that means though...


Your panel is ABABAB...AB from top to bottom, on both sides of
the breaker panel (left/right). The example given in your .png
showed AB....AB on the left, and BA....BA on the right. This is
a lay-out that makes zero sense and would require some goofy
bus work to accomplish. If you look at your breaker mounting
points you will notice that every other bus tab, from top to
bottom, is the same. So, the top two bus tabs, inline from left
to right are phase A. The next row down will be phase B, inline
from left to right. A 2-pole breaker will take up two spaces, top
to bottom and will give you both an A and a B phase. A 2-pole
breaker mounted to its right will pick up the same bus tabs as the
first breaker, but, of course, it will be to the right of the first
circuit breaker. Just look at the two breakers that currently
exist at the top of your panel. They are end to end with their
operators (handles) moving in opposite directions to achieve the
same action. Yet, the wiring is the same for both breaker, top
to bottom. Meaning that if you where to have black and red wires
denoting phasing, the black would go on A, and the red would go on
B. This is a universal construct in electrical work. Black is always
A, Red is always B, and if three phase, blue would be C. A three
phase Delta would replace the red with an orange, denoting the fact
that the system is Delta, and that the B phase to ground is a high
leg and is not 120v and is not to be used for 120v circuits.

Colors are important!

I worked in a 240 Delta panel once that was phase taped for a Wye
connection. Black, Red, Blue. I needed to move a single pole
breaker down one slot to install a 3 pole breaker. There was a
single pole breaker at the top of the panel, on that side, so this
put the breaker I had to move down onto the high leg. I did not
notice this and since my boss just said hurry up, get it done, and
lets get out of here, I did not check the voltage. Well, someone
went into the bathroom and the fart fan ran really fast for about
10 seconds before it went up in a puff of smoke and the incandescent
lamp was really bright, too. Until it blew up. Never take anything
for granted for when you do so, you or someone else might get hurt.