Surface mounted PVC pull box below main panel

Question

So, I was going to just make a few comments to clarify things as requested but “it” suggested instead that I edit my original question. Since this is my first post on this “exceedingly invaluable to me” forum of “highly respected and trustworthy experts” I’ll just rewrite the whole dang thing and hope it makes more sense this time.

I need to replace a janky and dangerous 6/3 NM Romex cable run a prior homeowner ran from a recessed/ flush mounted main breaker panel in the front corner of the garage to a detached shed/workshop that’s 30’ away from the back corner of the garage. The cable ran down and and out of a hole in the wall 3 feet below the panel. It then ran exposed/stapled along that same garage wall for 10 feet or so then dove back through the wall into a 3/4” PVC conduit body and then through 30’ of PVC conduit buried 4” underground and into a 6 switch subpanel that fed the tattered shed workshop.

Pretty dangerous stuff on a 50 amp breaker so I gotta fix it somehow. I’ve locked out the breaker, pulled out the cable and conduit and temporarily terminated that into a J-box mounted near the main breaker panel. I’m not ready to cut out Sheetrock and delve into that new to me main panel yet. Who knows what I’ll find in there. Meanwhile I’ve totally remodeled that old tattered shed, roughed in the wiring to convert it to a proper workshop (using extension cords for power of course).

I’ve replaced the old 6 switch subpanel with a larger Main Breaker Load Center as I thought I needed a main switch out there. I added a grounding bar to it. The Neutral bonding screw came in a bag so one less thing to do. I’ll need to find a creative way to wire up couple of ground rods to it since the shed sits on a thick gravel pad that extends out a foot or so around the entire shed.

So now I need to hand dig a 30’ long 18”+ deep trench from the garage to the shed (joy). But, I can’t do that until I know where the conduit will exit the garage.

I was planning on following the same route as the previous janky NM cable as it results in the shortest and easiest conduit path and trench. It also moves the path away from the main panel area where all of the services enter the home from underground. I plan on using 1 1/4” PVC conduit, conduit bodies, expansion fittings and potentially a pull box or two as I will probably have to pull the wires on my own without help and, it just kinda makes sense to me.

I was planning to cut the Sheetrock and run a 6/3 NM Romex cable from the existing 50amp breaker (or from a new GFCI one if safer?) about 3 feet inside the wall straight down and into the back of 4x4x4 or 6x6x4 surface mounted, outdoor rated (less than 3 feet from the garage door) metal (have to ground it) or PVC (how do you clamp the cable/s) J-Box/pull box(?).

Inside that J-Box, connect the 6/3 NM cable wires to 6-6-6-8? (R,W,B,G) THHN/THWN-2 wires using well insulated split bolts (Those THWN wires will run continuous in conduit from there to the workshop subpanel).

Attach an 8 foot section of 1 1/4” PVC conduit to the side of that surface mounted J-Box and run it horizontally along the face of the same garage wall and into the side of another surface mounted PVC J-box (pull box). Then, stub conduit out of the back of that box through the exterior wall and into a conduit body. Then, down to a PVC expansion fitting and to a PVC 90 connected to 30 feet of dead eye straight 1 1/4” PVC conduit buried 18+ inches underground.

At the shed, connect a 90 to get out of the ground then connect an expansion fitting and conduit body to get into the shed. Stub through the wall into the back of a flush mounted 4x4x4 (?) pull box (inset into the wall) then run conduit out of the top of that box and hub it to the subpanel.

This all seems right to me and it seems to make me feel good about the whole thing but for now at least. What do you awesomely wise folks think? Should I do it this way?

Answer 1

If going outside, often the simplest approach for a flush-mount box is a junction box or LB in the wall (with access on the wall surface) leading to a conduit going outside, and run the conduit outside from that point. Or a conduit nipple straight out the back of the Main panel to outside.

Another approach specific to working room rules is to come out of the wall above the working room height (78 inches or the top of the equipment, whichever is higher) on top of the panel. Plug the old hole in the panel for the previous cable with a filler plug. If you are left with a hole in the wall the cable came out of and are very opposed to drywall repair, cut to insert an empty old-work junction box (flush) and cover.

Personally, I'd cut drywall, install cable or conduit, and repair drywall. It's not the living room. And I'd take a serious look at 2AWG or 4AWG (but the price is often nearly the same) aluminum, since a 2224 aluminum feeder will fit in 1-1/4" conduit, costs less than 6 AWG copper, and has more capacity than 6 AWG copper.