Connect 6/3 Romex to THWN? (Detached shop to detached shop wiring)

[Will Rowland]

I've got a detached shop with a 100 amp subpanel. Behind that shop is an older 480 sq ft garage that languished in disrepair for a number of years. I have now structurally rebuilt and re-roofed the older garage, and I plan to use it for both both storage and secondary working space.

I'd like to add a 60-amp sub panel to this building, as it currently has no electrical service. To go from the 100 amp sub panel in the main shop, I'll need to run through the main shop's walls about 25 feet, and then outside about 6 ft, and then of course up and into the 60 amp sub panel.

My plan is to run 6/3 Romex inside, through the walls (which will soon be insulated), and then switch to individual THWN wires (6-6-6-10) inside a metal "pull box" enclosure on the outside of the main shop. The THWN wires will continue in 1" conduit underground and into the second building. I'm aware that the second shop will need its own ground rod, and that the neutral and ground must be kept separate on the sub panel.

My questions are 1) is there any reason you can't or wouldn't want to run 6/3 Romex inside an insulated 2x4 wall, and 2) what is the approved way to connect the Romex to THWN inside the pull box. Do I just use split bolts, heavily wrapped with plastic tape and then electrical tape? Or do I have use something like a "Polaris" connector ($$$)?

[Bruce Wrenn]

You can use split bolts, or wire nuts, but the ground has to be connected in a buss bar. Just buy a ground bar for a panel, and mount it to your box, to connect grounds. . Personally I would run it all the way with THHN. Why not go through wall at panel with an LB, and run PVC all the way. No splices, or junction box.

[Scot wolf]

^^^^^

That's what I'd do. Except THWN....underground conduit is a wet location.

[Christopher Dopp]

If you use THWN all the way, I believe you will need to run conduit inside the house as well as it has to be protected even in stud bays.

I did the same thing you are thinking about. I installed a large junction box where the 6/3 Romex met the THWN (6-6-6-10) and used a splicer terminal block to join them together. I used a large wire nut for the ground.

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http://www.drillspot.com/products/44...terminal_block

[Jim Neeley]

Another approach, if it were worthwhile for you, would be to go install a disconnect panel for the "junction box". It would provide the "terminals in a box" and permit you to "lock-out, tag-out" energy isolation for the older garage.

Jim`

[Von Bickley]

Will,

The procedure that you described will work fine. I would use the split-bolt connectors with good electrical tape.

[Will Rowland]

Thanks the responses. The terminal block above is exactly what I was hoping to use (but didn't know how to find/describe one until now). A disconnect is also a good idea, but I do plan to have a breaker at the main shop panel as well as a back-fed breaker on the "shop annex" panel, so it would be a bit overkill, and I would have to find a 3-pole disconnect at a reasonable cost.

Running THWN in conduit directly out of the wall behind the main shop panel would no doubt be the simplest option, but that side of the shop is adjacent to the patio "sitting area", replete with pavers and landscaping, so aesthetically that's not really option (the main shop sub panel lines enter the building underground through conduit in the slab).