Electrical – Need tips on running 230 in detached garage

electrical

I'm looking for some direction here. I have a detached garage that already has power supplied to it, and the structure is divided into garage space and a woodworking shop by a partition wall. The garage space is all exposed joists, beams, and studs, but the shop area is all finished. The panel is in the garage on an unfinished wall. I want to run a 20A 230V circuit to the partition wall for a single 230 receptacle, and an electrician has told me there's enough spare amperage to run the circuit. I'd have a run of about 15' to the wall, and then over a few more feet to drop it down the wall (the top of the wall is also exposed in the garage side, but is finished with OSB).

I spent some time as an apprentice electrician about a decade ago, so I have the tools and confidence, a healthy respect for the lethality of electricity, can generally read and understand NEC code citations, and I'm an anal retentive perfectionist who doesn't want to get sued or have anyone get killed.

So these are my questions:

  1. Should I use THHN in PVC rather than NM cable? If THHN, could I make
    a run up the wall and across the joists into a junction box, and
    then run NM down the wall?

  2. What's considered "workmanlike" practice when running conduit up
    studs and across / parallel to joists?

  3. I'm planning to use 12 gauge conductors for a 20A circuit – I'm
    under the impression this is what's advised? A dust collector is the only thing that'll be running on this circuit.

Best Answer

I would not hesitate to run EMT conduit the whole way, and for a very good reason: Alterability given that the wood shop is a finished space.

You're in a wood shop. You have things arranged the way you'd like now, but you may decide later you'd like to rearrange, or add something else. Add a circuit? Pop the covers off, pull 2 wires, punch em down, badabing.

And I like EMT conduit because over on the unfinished side, it provides physical protection without question. Sched 40 PVC is limited in its ability to provide physical protection.

Also, if you're drilling holes through joists to accommodate the wire or conduit, EMT lets you get the most through the smallest hole - up to 4 circuits in a 1/2" EMT pipe. With wood shop tools that even allows a couple of 30A/#10 tools.

I think 12 AWG is a good idea. I own 11 colors of stranded 12 AWG (just found blue-red at the Habitat for Humanity store) and none of 14 AWG. I need the colors for circuit disambiguation, much much much more than I need to save small coin on my few circuits that can be 15A.

There is one circumstance where you can put #14 on a 20A breaker (or #12 on a 30A) - but this is not a case of undersizing wire (you'd never do that). For certain motors, you are allowed to use the correct and proper size of wire for the motor, then up the breaker to avoid startup trips. To qualify for this, certain motor calculations are required.

Related Topic