More than just a ? on grounding size for sub panel.
I've read through a bunch of posts and found a lot of good info, but I didn't see this answered directly.
I'm running a 40amp sub panel in my attached garage using #6 in conduit. I'm not going all the way back to the main panel with it though. About 3/4th of the way across the basement I'm tying into an abandoned electric range feed, which is a 6/3 NM w/ground (all copper). I threw up a Milbank and brought in my #6's and the 6/3, and tied them in with a Polaris block.
My question is what size wire do I need to bring back from the sub panel to where I'm tying in with the 6/3? One of the electricians on a job I'm at said I should run #8 for the ground. Does it need to be that big? I've got the #8 so it's no big deal, but what if I ran the 6/3 w/ground all the way between each panel? The solid wire ground in that NM looks pretty small. Could I run the same size solid ground?
More of a theoretical question I suppose.
Thanks for any info.