On Sat, 17 Sep 2011 12:00:24 -0400, Doug Miller
wrote:

On 9/17/2011 9:33 AM, Andy wrote:
On Sep 16, 6:29 pm, Doug
wrote:
On 9/16/2011 6:43 PM, Andy wrote:

On Sep 16, 6:15 am, Doug
wrote:

Also, someone working on one circuit and not knowing that the neutral
carries current from a different circuit could receive a fatal shock
from that neutral -- how would he know to shut down both circuits?

Andy comments:
I am confused as to how you think someone could receive a shock
from the "neutral" wire...

Because it carries current. The same current that's in the hot.

It is normally not disconnected in any
configuration ---

It doesn't really matter whether it's disconnected or not. It's carrying
current.

Consider two simple circuits, A and B, each supplying no loads other
than a single 100W light bulb, each of which is turned on -- but,
unbeknowst to you, their neutrals are cross-connected. Well and good.
Now suppose you need to replace the fixture on circuit A. Knowing that
it's on circuit A, you shut off that breaker, and disconnect the hot
lead to the fixture. Now when you go to disconnect the neutral lead, you
get a shock, because -- and I think this is the point you are missing --
electricity doesn't "follow the path of least resistance" as many people
believe, it follows *all possible paths*, including the one that you've
just made with your body by touching that energized lead.

Andy comments:

You are incorrect. I suggest you actually try it. Both neutrals
are
connected together, HARDWIRED, at the sub panel...

Yes, I know that. You don't seem to understand the concept of parallel
circuits. If your body is grounded, and also in contact with the neutral
conductor, there are two parallel paths to ground: one through the
neutral conductor, and one through your body.

Most of the current will flow through the copper conductors. But it
takes only a few tens of milliamps to interfere with heart rhythms.

1ma is the threshold of sensory perception - less than 1ma the average
person can NOT detect. 5ma can be considered to be "dangerous"
20-30ma is a strong enough shock that you "can't let go" and at
anywhere between 100 and 300ma the heart is affected and death is
likely.
6 amps will stop the heart - after which normal rythm can be returned
(defibrilator)
That is current THROUGH THE BODY. If ALL of that current flows through
the HEART MUSCLE, several milliamps CAN be fatal.

You are nomore likely to get a shock from one as from the other...

In the sense that you're equally able to get a shock from each, I'd agree.

But, I'm not here to argue with you... My input is to Ivan... He
is
smart enough to read all the inputs and decide for himself...

Andy in Eureka, Texas, Licensed Electrical
Engineer....

An EE that doesn't understand parallel circuits? Yeah, riiiiight.