Pete C. wrote:
....
I'd recommend the OP check more carefully to see if there is indeed a
bare ground conductor in that Romex, perhaps one that was clipped flush
with the jacket for some reason by the original installer.

If the Romex has a PVC jacket vs. cloth, there should certainly be a
ground conductor in it. The print on the PVC jacket should indicate
something like 12-3 with ground. If the Romex is old enough to have a
cloth jacket then perhaps it really doesn't have a ground, though I've
seen a lot of cloth jacketed Romex that has the expected bare ground
conductor.

And I've seen a lot of plastic-jacketed romex w/o the ground, too. It
certainly wouldn't be at all hard for all the wiring except the ends
coming out of the handy box and in the panel to be inaccessible to
check, but if can be seen, that would tell OP if he can't tell. But, if
the original installer cut it off so short he can't even tell there was
one there, it really won't help much any way, will it?

--