Romex in Conduit?/Grounding
My wife and I bought a house a year ago, and in the last 12 months we've done a lot to upgrade the electrical. We've discovered some pretty interesting stuff behind our walls.
Right now we're focusing on some rewiring in our detatched garage, which has an old Square D sub-panel that is several years old. Eventually we'll replace that panel, but I'm trying to work with it now.
One thing I have noticed is that the panel does not have its own grounding bus. I believe the previous owners dealt with this by feeding outdoor-rated UF cable through the garage wall and down into a hole inside metal conduit.
I can't quite tell without ripping it out of the ground, though. Is there any way to tell that this is what they were doing and/or test that this is properly grounded?
If not, is this a reasonable and safe solution for grounding the subpanel?
I'm also rewiring all of the outlets inside the garage using 12-3 double receptacle circuit and GFCIs. There is currently a system of conduit in place, but the wiring inside the conduit is old and I don't trust it.
I'm wondering if it's OK to run Romex-type 12-3 cable through conduit, or if the individual wires must be unsheathed. I have 12-3 wire in-hand, and my preference is to use that, but if it's not safe or code-compliant I'll go ahead and use unsheathed wire. I've gotten conflicting info on this and I'm hoping to get the matter settled.
If they do need to be unsheathed, is it OK to use bare copper ground wire, or must that be insulated (green)?
Thanks in advance for any guidance.