I want to run an open wire feed to a 160M Dipole .... I need to bring
the feed in and across my basement. I want to run along the floor
joists
but like most basements there are pipes and duct work all over.

What would be the minimal acceptable separation between other metal
object and the open wire feed???

For an idea of what I'm up against:
http://pabut.org/feedline.jpg



So far, no one has mentioned using a short section of balanced coax.
Rather than using baluns and a single coax, you could use two lengths of
coax to get past the metal. Use the center conductors of both parallel
pieces, and just connect the two shields together. You will still have
high losses in the coax, but shouldn't be significant if you keep the
coax run short. Doing it this way will at least avoid the possible high
voltage node / fire hazzard problem of having open ladderline near wood
and metal fixtures, and also avoid needing to use baluns.

good luck.

Ed K7AAT