I'm just about ready to start drilling holes and wiring up my new garage.
I've never done any new structure wiring before.
I'm going to be sheeting with osb so I can hang stuff randomly on the walls.
What is the safest way to run all the wires? Should I drill near the tops of the studs and just bring single wires down to each outlet? How far in should the holes be? Should the wires run behind or in front of the insulation? How big of holes?
There are a number of different ways this CAN be done, but some are better than others. Given your desire to be able to "hang stuff randomly on the walls" in the future, you should go to some length to ensure that there WON'T be wires lurking behind wherever you might want to drive a (possibly too long) fastener five years from now (i.e., long after you've forgotten exactly where each wire actually runs). One way to accomplish that is to wire everything at least primarily from the top, drilling ONLY through the top plate. Anywhere you
DO need a horizontal run, keep it absolutely as low as possible, while still observing any code restrictions (which may specify a minimum height, due to concerns about flood water and such).
Given your 2x4 framing, you can "legally" drill holes in it of up to one-inch diameter; but this presumes that you get those holes PERFECTLY centered every time. Personally, I'd stick to 3/4-inch, whenever possible; this is still large enough to run at least a couple NM-B cables through (if perhaps a tight fit in the case of something like 10-3 w/g). Also, do NOT make "Swiss Cheese" out of your framing, by drilling multiple holes in close proximity.
The insulation should not be an issue. The wire gets stapled to the side of the stud from within a few inches of where it exits the hole to within a few inches of its final destination; and so it will be out of the way for at least most of its run. In the case of any horizontal segments, the wire should be in the middle (depth-wise) of the stud cavity (due to the holes being centered in the studs, if nothing else); in this case, the insulation gets "split" where it passes the wire, with half going behind the wire and half in front of it. Note that you need to get your electrical inspection done BEFORE you put in the insulation, so that the wires remain visible.
I'm going to be running lots of outlets. Probably close to 20 each on their own breaker So I never blow any. So lots of wire to run.
WHOA, NELLIE!!!
That is GROSS overkill, and a huge waste of money & effort.
For your general-purpose 120V outlets, my usual "recipe" will likely suffice: Put one double-gang box every 6-8 feet (maybe 10 feet, at the most) around the entire perimeter of the space, with each of the two duplexes in that box fed from a different breaker than the other one. In relatively small shops, two 20A circuits will normally handle the whole thing. In larger shops (particularly if there will be more than one person working concurrently), split it up further as you see fit; but even so, I SERIOUSLY doubt you'll really need to do so in a 30x30 "one man band" shop. This is relatively easy to do, and requires only two runs of 12-2 NM-B from one outlet box to the next, all the way down the line. Note that the FIRST pair of outlets in the run need to be GFCI types, and the rest of the "daisy chain" runs off the "Load" terminals on those outlets. In theory, you can use a single run of 12-3 from the breaker panel to the first pair of outlets; but personally, I wouldn't. First, it's easy enough to just pull another length of 12-2 off that big spool you're going to buy anyway; second, using 12-3 would require running the whole thing off a common-trip double-pole breaker, which means that if EITHER circuit trips, they ALL go out. Bottom Line: It's just not worth the hassle to save a few pennies on wire, IMCO.
Optionally, add a third 20A circuit in the vicinity of the workbench, especially if you (will) have high-draw 120V tools (bench grinder, drill press, etc.) in that area; but this is still really more for "peace of mind" than to address an actual NEED, as you presumably won't be running more than one of those tools at a time anyway.
Keep the bottom of the boxes at least 49-50 inches off the floor; you'll understand why the first time you try to store a 4x8 sheet of plywood, drywall, etc.
Most permanently installed "machinery" will likely require 240V; the specific current (and thus wiring) requirements will depend on the particular machines in question. Until you/we know exactly what those machines are (or will be), it's pointless to guess at it further.
A 1 or 1 1/4" spade bit will do you some work.
No. A 1-1/4" hole in a 2x4 stud (which is only 3-1/2" wide to start with) is too large, and will not leave sufficient "meat" on either side of the hole. As noted above, even 1-inch is "iffy", because it requires absolute precision in its placement.
Running dedicated lines to thing that will run by themselves (compressor, dust collector, etc) makes sense, but to dedicate everything else is silly.
I agree with that.
It's a 30x30 garage.
Yeah maybe 20 dedicated is a bit over kill.
No doubt about it.
There's going to be 2 - 220 outlets. One for a welder and one for a compressor.
These circuits need to be sized for the SPECIFIC equipment in question; and the proper methods to do that aren't necessarily obvious to the casual observer / DIY-er. Have you purchased these tools yet? If so, what are they, specifically? If not, then you need to make at least a fairly sharp (yet conservative) "educated guess" about what they will be.
Then a few 110's dedicated for power equipment that wont ever move like Drill press, Bench grinder, ban saw...also later probably a mill and lathe.
The drill press and bench grinder are covered above. The rest of that stuff is rather unlikely to run off 120V.
I have 100 amp service for the garage and a 48 circuit box in it. I figure it's better to over do it now then wish I had done it later.
No argument with the basic philosophy; but you are taking it to a silly extreme. And remember, you DO want to leave room for expansion later, because you cannot possibly predict EVERYTHING you're going to want to do in that space five or ten years down the line.
Usually it will just be me working in there but I could easily see 3 people working all at once.
And all using 120V power tools at the same time? THAT is the key issue.
I understand how they are getting it. DO NOT understand why this requirement is being touted for a RESIDENTAL garage.
Nobody has claimed that it is a "requirement". It is a RECOMMENDATION, which is a fundamentally different thing. Building something only to the minimum legally mandated requirement is a good way to ensure disappointment later.
Ok so something like this
3 - 220 circuits
5 - single outlet circuits
4 - multi outlet circuits. (Maybe 4 on each?)
1 - circuit for 2 garage door openers. (Or should they be independent?)
2 - for lighting
1 - for exterior lights and outlet
1 - to the furnace
That's only 20.... I'm sure I'm missing something right now though.
Still overkill.
As noted above, the 240V stuff needs to be addressed separately. But fourteen 120V circuits is just silly. AT
MOST (and with a big nod to the idea of multiple folks working simultaneously), four or five "general purpose" 20A/120V circuits (i.e., feeding each "half" of the space from a different "pair" of 20A circuits, with one more added in the workbench/tool area for good measure) will be MORE than adequate, even accounting for that drill press, bench grinder, blast cabinet, etc.
Two circuits for ALL of the the interior lighting will be quite sufficient. The exterior lighting can near-certainly be "piggy-backed" onto these same two circuits, unless you're planning on several HUGE Metal-Halide floods or similar.
The exterior outlets should NOT be on the same circuit(s) as your lights. But again, unless you're planning on (several) huge loads, they CAN be on the same circuits as your general-purpose interior outlets.
Ideally, the garage door openers would be on their own circuit (one @ 20A will near-certainly do); but this is mostly to avoid the need to GFCI-protect that circuit (which will also require that the GDOs be hard-wired -- but that's OK; they're not going anywhere).
The (presumably gas-fired) furnace does not really need its own circuit; but if you really want to, go for it. What it DOES need is a conspicuously placed and easily accessible Emergency Shut-Off switch, with an appropriately labeled (and usually red) switch plate.
So that's nine 120V circuits, MAX; and I'm being generous.
Garage door openers could go 1 on each lighting circuit.
MAYBE, depending on the relative loads. But probably not a good idea in any event.
OMG. I thought this would be a huge shop and 20 breakers might be reasonable. A 20x20?!
Actually, he said 30x30; but your point is well-taken.
4 walls, 3 without garage doors on them let's assume. If you want to go ********, do three MWBC circuits, one for each GD-less wall, with each receptacle split.
Given the need for the outlets to be GFCI-protected, MWBCs cannot be used except possibly for the initial run from the panel to the first pair of outlets; and as noted above, even that comes with a down side. IMCO, it's just not worth it.
I have this setup in my barn. Looks like the breakers are still quite expensive though, which *****. It'd be cheaper to run a different GFCI at each outlet!