A Couple More Questions About Wiring Up My Garage

johnliu_gwJune 21, 2011

I've started wiring the garage, and have a couple quick (I think) questions. I'd appreciate your advice on what is proper, tidy practice.

- I'll have four duplex outlets on one side and back corner of the garage, on one 20A circuit, and four on the other side and corner on another 20 A circuit. Can I do these in one conduit system? I mean, the three hot/neutral/ground wires for the near wall's circuit runs through the conduit and outlet boxes, connected to receptacles #1 through #4, with #1 being GFCI, and terminates at receptacle #4. The three wires for the far wall's circuit runs through the same conduit and the same outlet boxes, but is only connected to receptacles #5 through #8, with #5 being GFCI. I am using #12 individual conductors in 1/2'' PVC conduit, and the boxes are PVC, all surface mounted, with the conduit running directly from one box to the next, horizontally around the garage at 50'' height.

- If I do that, then should I use a black hot wire for one circuit and a red hot wire for the other? Just to keep things organized?

- I will have a wall switch controlling the ceiling lights, and on a different circuit a ceiling receptacle for the garage door. Is it okay to run the wires for these two circuits in a single conduit to a ceiling junction box, then branch conduit off to each circuit's destination?

- I will have two 240v outlets on the far side of the garage, each on a different circuit. Can I run these circuits in a single conduit system, as I described for the 120v outlets above? Or should I run each circuit in it's own conduit?

- (As you can tell, I'm unsure if it is considered sloppy to bundle multiple circuits in one conduit run. I'd like to do that, for convenience.)

- The 240v outlets are not required to be GFCI, is that correct? Is it recommended to make them GFCI, and if so, what is the best way? (I didn't see any GFCI 240v breakers or outlets at the big orange box.) Oh, one 240v will be for my table saw (rated 9 A at 240v) the other is for some unknown future tool? Maybe a small (hobby type TIG) welder someday. I was going to use #8 conductors in 1'' conduit, to accommodate the possible future welder, which might draw up to 30 A at 240v.

- The ground wire from my ground rods can be . . . #6 bare copper, simply stapled to the garage structure (it has to come up over the garage door to get to the subpanel)? Or does it have to be insulated, or in conduit?


Thank you for reporting this comment. Undo
Ron Natalie

You can put as many circuits as you want in the conduit (subject to the conduit fill rules). Do note that if you run more than three current carrying wires in the conduit you will have to derate which may mean increasing the wire size. If you run two independent circuits, that would be FOUR current carrying wires.

You can use whatever colors you want to keep things straight as long as your hots are some other color other than green or white. More often than not everything is black.

Running THHN through the conduit allows you to derate and still make 20A.
Another out is to ditch the GFCI receptacles for a GFCI breaker and install a multiwire branch circuit (which would be allowed to share the neutral providing for only 3 current carrying conductors).

Your biggest issue is 1/2" PVC is going to be too small. It's legal limit is 4 #12's. You'll not get two independent circuits in there (that would take 5 wires at least). The other thing to watch out is for your box fills, you need to count the conductors that pass through even if they don't terminate at a device or are otherwise spliced there.

As for the lights and the garage doors, again you can run wires together again as long as you don't exceed the conduit fill rules and wire ampacity rules.

Again the same applies for your 240V circuits (other than the fact you can't have a MWBC for 240). The code only mandates garages (at or below grade) to have GFCI's for the 120V 15 or 20A receptacles. It is up to you to decide if you want or need GFCI protection on the 240 circuits. They most certainly do make 240V GFCI breakers. They're a bit pricy and the borgs do carry them for some of the more popular panel brands. Otherwise, unless you can wrangle the trade discount out of the local electrical supplier, you can find them on the Internet at competitive prices.

The ground wire doesn't need to be insulated or in conduit except as necessary to be protected from physical damage. I might sleeve it where it emerges from the ground for a 18" or so. It's not a strict code requirement, but frankly if direct buried stuff can be damaged emerging from grade, so can your ground. Keep it safe from weed whackers and other careless gardening.

The fact that you put ground rods in seems to imply this is a separate structure. Did you run both a neutral and ground with your feeder?

    Bookmark   June 21, 2011 at 7:05AM
Thank you for reporting this comment. Undo

Time available does not permit posting my suggestions to all your questions. But one suggestion is to keep every electrical box at least 18" above the floor level. Lower installations may require the use of materials suitable for Class 1 locations.

    Bookmark   June 21, 2011 at 7:09AM
Thank you for reporting this comment. Undo

The feeder is two hot, neutral, ground. Neutral bar in subpanel is not bonded.

Arrgh about the 1/2'' conduit being too small. I fear I'll end up running each circuit in it's own conduit system, then. (I thought 1/2'' was logical as the female holes in the outlet and switch boxes were 1/2''.)

I am keeping all outlets at 50'' height, as I want them to be above work counters and tools.

    Bookmark   June 21, 2011 at 8:28AM
Thank you for reporting this comment. Undo

You can run up to eight 12ga THHN wires in 1/2" conduit, so your plan for running two circuits is fine. If you run two independent circuits you need two hots, two neutrals, and one ground (can serve both circuits). You will need to to make sure the neutrals are kept separate for each circuit.

    Bookmark   June 21, 2011 at 9:16AM
Thank you for reporting this comment. Undo
Ron Natalie

Depends on whether you are using sched 40 or sched 80 conduit. I inadvertently gave the numbers for sched 80.

    Bookmark   June 21, 2011 at 1:07PM
Thank you for reporting this comment. Undo

I'm using sched 40, sorry - I should have stated that.

    Bookmark   June 21, 2011 at 2:20PM
Thank you for reporting this comment. Undo
Ron Natalie

I had sched 80 on the brain because you can't use sched 40 for protection from physical damage.

    Bookmark   June 21, 2011 at 3:31PM
Sign Up to comment
More Discussions
Humming Transformer
Last summer the POCO replaced the transformer on the...
Badly done multi-wire circuits (previous owner strikes again..)
I bought a 1940-ish house last year, for which the...
Wireless light switch for switched outlet?
So we have no overhead lighting in any of our bedrooms,...
Goodbye Phone Jack: what to do with wires?
We want to remove this phone jack. It's in a useless...
Inspection Report
Had a gorgeous 1909 house inspected yesterday and don't...
People viewed this after searching for:
© 2015 Houzz Inc. Houzz® The new way to design your home™