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I have a great workshop (20 x 25 ft, 2 level) that was built with no power (previous owner). I'm installing a subpanel in the shop (90A) and need to install receptacles, lights, etc. as well. I've never organized a shop before so I'm unsure how to do it (looking for advice). Here is what I planned:

Install a 20A receptacle every 5 ft down the north, east, and west walls (south-facing wall has garage doors) and two rows of lights on the ceiling. The lights will be on their own 15A breaker and each wall will have its own 20A breaker. The first receptacle on each wall will be GFCI.

Here's my question: what is the best way to route wire to the receptacles and lights? Is it better (right/wrong) to drill through the studs to run the wire directly across the wall, or to run the wire along the top plate and drop wire down to each receptacle? Since I will not finish the walls I do not know if there is a code issue for either method, or if conduit needs used. If this is just a matter of preference (i.e. not code related) then I am still interested in hearing people's opinions.

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    I would ask those who voted to close to rescind their vote. I think this is an OK question, even if a bit broad. – George Anderson Oct 7 '20 at 17:15
  • @GeorgeAnderson I thought my original question was fine, but I modified it to be more focused. I tried to change it so that all of the answers are still relevant. – tnknepp Oct 7 '20 at 17:17
  • @GeorgeAnderson Well, I disagree with the close votes, but I don't fault isherwood for critiquing it. There is has to be balance in what/how much is posted, and I respect that, but at some point it becomes opinion based. I'd rather have the question live on in a modified state than be removed due to "poor quality". – tnknepp Oct 7 '20 at 17:22
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    Clarify please - is this workshop for welding or similar where the wiring might need extra protection? – Criggie Oct 8 '20 at 1:45
  • You could use the opportunity to install emergency stop buttons, if you wanted to. – Andrew Morton Oct 8 '20 at 9:14
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I prefer the "up and over" method rather than drilling thru the studs, esp. since you don't intend to finish the walls. Not sure what code says about that. I believe that exposed cable below a certain height needs to be protected (8 feet?) So that would mean running the cable in conduit for the 4-5' from the outlet to near the top plate.

When I built my shop, I used surface mounted Wiremold 4000. But because my shop is partially earth sheltered, I have very high (4.5') stem walls. I went with the raceway because shops are often "evolving" with new tools, changed layouts, evolving requirements, etc. Conduit would be less forgiving. So now when electrical needs change, all I do is pop off the covers and run whatever wiring is needed to the sub-panel, install the appropriate outlet and pop the covers back on. This may be over-kill for your needs, but wanted to let you know what I did. Also attached is a pic of the actually installation in my shop (wood-working oriented).

Some other advice: What are you planning on using your shop for? I spent hours laying mine out thinking about workflow, staging, benches, storage for small tools, etc. I have 2 basic work areas in my shop: 1) basic milling where I have the table saw, jointer and planer in one area, and 2) A free standing heavy duty bench for more detailed work like dove-tailing, sanding, gluing, routing, etc. I know this answer goes way beyond what you were asking, but I just wanted to share. Have fun setting up your shop.

Wiremold 4000 Actual install of wiremold 4000

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  • Thanks George. This is a great tip on the raceway. I think the up and over method will look better, so I'm inclined to go that route (or raceway). Running wire through the studs may work well for finished wall, but when the wall is exposed I worry about something snagging the wire and ripping it out of a receptacle. – tnknepp Oct 7 '20 at 17:00
  • Yes, and there are code issues regarding exposed cabling below a certain height. While the "up and over" method probably doesn't address the code issue, it would be safer than thru the studs. – George Anderson Oct 7 '20 at 17:20
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    Exposed-cable protection generally depends on inspector/locale, as the Code doesn't provide prescriptive guidance on that. The surface raceway is definitely a very good line of thinking, though! – ThreePhaseEel Oct 7 '20 at 23:55
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Lights on their own breaker is good.

One breaker per wall is dubious. If you alternate the breakers feeding outlets there's a bit more wire, but when you are working in an area and plug two things into adjacent outlets, less chance of a trip. Or, use dual-gang plates/boxes and put the two duplex outlets in each box on different breakers. You can use different colored outlets to visually indicate which outlets are on which breaker.

If you have double garage doors, an outlet on the center "post" divider will be of use. Consider some outside outlets (with in use covers) as well.

Consider locating wall outlets at ~52 inches, so that a sheet of 4x8 material leaned against the wall won't block them, at least where you don't plan workbenches.

My personal preference is to use EMT (right on the surface of the studs if not planning to finish, or on the surface of the wall if you are planning to finish) and THHN for workshop wiring, rather than NM/B. It's not much more expensive and it's far better protected.

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    I like the suggestion to alternate breakers on each wall. I guess a multiwire branch circuit would do the trick. diy.stackexchange.com/a/66444/124084 – tnknepp Oct 7 '20 at 17:19
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    The catch with MWBC is that you need to use GFCI double-breaker instead of GFCI/receptacle combo. – manassehkatz-Moving 2 Codidact Oct 7 '20 at 18:26
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    +1 for keeping lights on their own breaker - when a machine tool pops a breaker for some reason, you're not instantly in the dark with a moving blade slowing down and some stock that might catch and get thrown at you. – Criggie Oct 8 '20 at 11:09
  • I'd stay away from a MWBC these days. The price for 12/3 is almost double that of 12/2 and it just complicates everything. MWBCs don't always play nicely with arc fault and ground fault breakers. Others here may disagree but I no longer see any advantage to MBWCs. IMHO – George Anderson Oct 8 '20 at 14:18
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Your plan sounds good Drilling the studs is fine and usually uses less wire. (Both are ok) Make sure your hole is 1-1/4” back from the face of the stud on either side. Your shop lights don’t require a GFCI if they are hard wired but if plugged in they do require a GFCI (crazy I know but code is explicit there are no exceptions) You may think about outside lighting and a receptacle or 2 outside. I put 240v outlets on the back wall of my shop and later brought 1 to the front so I did not have to have a big extension cord. If you will be getting a welder what about a compressor? Possibly a second circuit for a compressor (now they both would require GFCI). That’s all I can think of for power wiring Low voltage wiring a security camera or alarm system may be something to think about.

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Since you're not finishing the walls (ie covering with drywall) then the wiring can be seen.

If its exposed, it can be damaged easier.

Personally I'd look at installing a series of dwangs (nods) across the wall, that can be used as storage shelves. If there's one just at the height of your outlets, then the cable can be secured under that shelf and pass through the studs. A facing board or edging strip across each shelf will help stop things falling off, and on the power shelf it can go down a little further and hide the wire. Also great for stickers or clipboards of notes/plans.

Each circuit will have to go up a stud at some point and back to the distribution board.

Consider also whether you want to use a 240V or high current appliance in the future. Pre-wiring a 240V line, or making provision for a car charger might be a wise plan.

Also consider putting a single protected waterproof socket outside the building too, on its own breaker - you may want to run a waterblaster, or connect a caravan or similar. Pre-building flexibility into your design is great.

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    Never thought of the dwang (had to look it up...apparently you're a Kiwi. Been to Lauder a few times; lovely place). One thing is for sure, I am always looking for another surface to store stuff (pencils, markers, etc.). – tnknepp Oct 8 '20 at 10:36
  • @tnknepp You can never have enough storage. And the ~3 inches depth of a wall is great for one line of spraypaint cans or jars or tins. If you have two ranks, the back one is invisible to guys :) – Criggie Oct 8 '20 at 11:11
  • "Dwang"... there's a new one for me! – Greg Nickoloff Oct 12 '20 at 18:01

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