On Saturday, December 23, 2017 at 10:10:39 AM UTC-5, dpb wrote:
On 12/23/2017 1:50 AM, Deguza wrote:
Hello all:

I have a home built in 1950. Im planning to rewire the home. I
looked under the crawlspace and saw that the whole house is wired
with wires in flexible metal conduits.

If I can use these conduits to care the new wiring, I dont have to
tear up any sheet rock, Except for replacing some of the metal boxes
that may be on the small side.

My electrician friend says that I should be able to run Romex cable through them.

Another friend says that I should just run individual insulated
wires.It might be cheaper and easier to work with, he says.

From what I understand both are acceptable in terms of code.

What do you folks advise?

That's BX armored cable. Why pull wire in the same run; in all
likelihood there's nothing wrong at all with the cable unless it's been
flooded or some other reason.

I guess because he's upgrading all the wiring, and per your later comments,
what he has doesn't have a proper ground, can't be used as part of new
wiring, etc.




With BX, the conduit generally served as the ground path so there's
likely not a ground conductor if this is original wiring and there
probably aren't grounded outlets unless some have been added since.

If it's very old BX, there was no ground back then. Today BX has
a separate ground wire in it, which provides the ground. In between
those two, I guess BX might have been used to provide a ground where
the metal jacket alone was used, but that doesn't provide an adequate
ground, which is why it now has the additional wire.





NEC limits the amount of "fill" such that going from 2-wire to 3-wire
the extra ground conductor may exceed allowable but if doesn't NM will
be much harder to pull and there's no point in doing so.

How would you ever pull anything in BX cable? Even if you theoretically
could get what's in there out, I don't think NM would ever fit inside.






A more definitive answer would be to know what is the purpose behind the
work envisioned.

--

Agree. IDK what he has, because he says an electrician friend suggested
he could run Romex inside, which doesn't make sense to me if he has BX.
But BX would seem to be the most likely thing for a house, not actual
conduit.