Wiring – Running 6/2 cable to garage for NEMA 6-50 outlet

garagewiring

I plan to install a NEMA 6-50 outlet in my garage, from a 50A breaker in the main panel. I plan to use 6/2 cable, unless there is a better recommendation. The run is about 50 feet, planned as follows:

a. about 20' along joist in basement

b. drill through block basement wall, exiting just above the floor of the garage

c. up wall of garage, through drywall ceiling into garage attic

d. across ceiling joists in attic

e. straight down through ceiling to outlet.

My questions pertain to steps b, d, and c/e.

b: When passing the wire through the block wall, is conduit required? I don't believe so, but please advise.

d: I under stand that the NEC permits the wire to run across the ceiling joists unsecured, provided that the attic is inaccessible (no permanent stairs, which is the case here–I have to use a ladder and climb up) and the wire is run at least 6' from the opening, which will also be the case here.

c and e: I assume conduit IS required for runs up and down the garage wall, otherwise the cable would be exposed to damage. So, I'm planning to use 3/4 PVC conduit, based on these factors:

NEC requires that cable take up no more than 53% of the space inside the conduit;
Outside diameter 6/2 cable = .3664; Inside diameter 3/4 PVC conduit = .824 (Link to home depot 3/4 Conduit for specs); Thus, cable will occupy only 44% of the conduit.

Please let me know your thoughts on these plans.

Best Answer

In turn here:

  • For your case b), conduit is not required -- NM is routinely run through bored holes in structural members without conduit.
  • For d), again, conduit is not required -- you can get away without guards if you run the cable along the side of the joist and at least 1.25" away from its edges. (320.23(B) and 300.4(D))
  • As to your protective runs in c) and e) -- 3/4" Schedule 80 PVC conduit has 138mm^2 of usable room in it for a single cable or conductor, and a 6/2 W/G NM-B cable, according to your specs, takes up only 70mm^2, so you have ample space. This might be a tight pull, though, so you may wish to go with 1" instead.
  • There are two other things you need to address with your conduit runs:
    1. The conduit you linked is Schedule 40, which isn't sturdy enough to protect wires from physical damage -- the code requires the thicker, sturdier Schedule 80 instead.
    2. Make sure to put expansion fittings in your PVC runs lest they do the snake on you mid-summer, or pull apart mid-winter! Easy rule of thumb for conduit that is operating within oh, 24degC of room temp -- put them in every 4m/12'. (You might be able to get away without it for isolated runs like yours provided the supports are set up so they don't provide excessive longitudinal restraint to the conduit.)
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