On Thursday, November 14, 2013 8:55:14 PM UTC-5, Danny D'Amico wrote:
On Thu, 14 Nov 2013 19:39:38 -0600, dpb wrote:



the third wire is the ground but NEC until

relatively recently allowed the ground to also be the neutral



You seem to understand this better than I do.



The way *I* understand a "ground" is that a ground wire carries no current

(unless there is a problem). The "neutral" wire, on the other hand, *always*

carries current.



That is true. But I have to be careful here. You said that the
neutral *always* carries current. I know what you mean, but there
are some here who insist on all cases being covered. So, to be
correct, it should be said the neutral carries the unbalanced
portion of the load in that 240V circuit. Whew. I hope DD
feels better now. The ground doesn't carry current unless something
is wrong.






That's a pretty big difference (as I understand it anyway).



correct


More specifically, the way I understand a ground wire, is that it goes

from the receptacle in the wall to the main breaker panel, where it

literally is driven directly into the ground (usually by some kind of bar).



Basically correct.




In contrast, the neutral wire, as I understand it, goes to the same

breaker panel, but then it goes from there to the power pole, and then

from that pole it may travel hundreds of feet to a few more power poles,

but eventually, it too is driven straight into the ground.



It's tied to the ground system of the house at the panel.




The difference, as I understand it, is that the ground never carries

current (unless there is a fault), while the neutral is always carrying

current (and therefore it might have a potential on it).



Given that they're not at all the same thing, I then have trouble

understanding the statement that the ground is "also" a neutral.



It is for 3 wire appliances that were permitted to be installed
that way prior to the 90s when the code was changed. They use one
conductor for both the ground and the neutral.




Again, you seem to understand better than I do, but, the way I

described it above, a ground and a neutral are totally different

things.



So, I don't understand how a ground can 'also' be a neutral.