Contained here is my opinion on how to wire your workshop. My workshop is fed from a separate 40A 220volt subpanel fed from the Main electrical panel. This has proven more than adequate for my needs. I have about 25 Fluorescent light fixtures, a number of portable power tools, and a Large Radial Arm saw, and a large Clausing engine lathe, and a couple 1 hp stationary tools (Bandsaw, drill press, Horizontal Bandsaw, etc). I also have a 220 volt 5hp air compressor. If you have a lot of large, stationary power tools, you may need a larger subpanel, but this has worked for me. Note alas, I have no allowance for a welder! Ah well. In my house, they had moved the Kitchen stove, and abandoned the old electrical wiring in place. Since this was close to the Shop, and the Electrical panel was at the other end of the house, this was used for my new sub-panel.
I want to stress right here that I can not make any assumptions about Electrical Code compliance. My installation passed inspection fine, but be sure to check before doing. It also helps to be on good terms with the local inspector, as they have some leeway in approval! Take this page as guidance, but always adhere to the Electrical Code!
On this page, I am going to address some specific issues first, and then describe my setup, why I did it that way, and how. I want to point out first, that my wiring is all in Conduit, and I highly recommend that. It solves some problems, looks better, is safer, and depending on where your shop is, it might be required. You may also find that once you get the hang of bending and installing conduit, it is a lot of fun! And, one bit of warning. Although I will address this below, be aware that just because a particular device or wire is at the Home Depot, does not mean it conforms to code! Make sure of what you are buying, and that it fits the application.
Finally, I want to make it clear, Make sure to get your work inspected, and make sure you do not have any (house) insurance issues if you do it yourself!! Check your policy and/or call your agent! Do not do electrical wiring if you are not familiar and comfortable with it. If you have any questions or doubts about how to do it, call in a licensed electrician. It is not worth your safety, and the safety of your family, friends, and house. You may be able to do the mechanical work, and let an electrician specify and hook it all up. You can consult your friendly electrician for that. Make no mistake, electrical wiring done improperly is a major, major safety and fire risk. I am going to focus on the layout and materials issues, not the techniques, if you are unsure, don't do it. And, remember, you are allowed to work on your own home, but not someone else's unless you are licensed.
I cannot stress this enough. Buy quality (Spec Grade) outlets and switches. The cheap fifty cent outlets are total junk! They will not hold up in a shop, and will often short out, and cause a fire on their own! Trust me on this one. Same with switches, and Wire Nuts!! Save the headache, and spend a little more. This is where quality counts, and it doesn't cost that much more. Buy brands like Arrow Hart, or the 'good" leviton. Get quality wire nuts from 3M or similar. And, never re-use a wire nut! And, about wire. Some wire out there is cheap, with very marginal insulation. Get brand name stuff. While the NEC has numerous tables, and formulas, basically, for conduit you want THHN of the proper size, and rated at 90 or 105 degrees C. The wire should be UL Approved, and is required to have rating markings printed on it every 1 foot. Some wire for sale at the Big Box store does not meet code!
Ny shop subpanel has eight circuits. Two of these are for a 220v outlet for my Air Compressor. I have one circuit (Breaker) that feeds some outdoor lights and the security system as well as a shop outlet for my clock & stuff, and this is left on all the time. There is one breaker for the general lighting, and then four separate circuits for different areas of the shop (Electronics bench, mechanical bench, woodworking, and power tools. This allows me to shut down the entire shop from the electrical sub-panel (which is near the door), and know that it is all turned off before leaving. One more note, if you have large stationary tools, you may want to consider a special circuit with emergency stop buttons located around the shop. This is outside the scope of this article, but you may want to consider it. Use GFCI breakers in your panel instead of separate GFCI outlets. It is much easier, safer, and often cheaper in the long run.
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This is my Shop Subpanel. It has six GFCI breakers in it and 1 220v dual breaker. The Large #6 Romex at the top is the feed in. The other two smaller romexes go to outside lights. The Conduit on the left top is the power feeds to the new shop, and the conduits coming from the light switches are for lighting. Inside, it is pretty simple. Neatness counts! | 
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Most of your wiring will use 1/2" or 3/4" conduit. You will need one special tool for this, a conduit bender. You normally get a handle, and then get a 1/2" head, and a 3/4" head. (This can also be used for other bending jobs). It takes a little practice to learn how to bend conduit. One tip: There is an arrow, or mark on the bender. If you measure the length you want, and place that arrow on your mark, the outside edge of the conduit will end up at your mark. Try it. You can also get all kinds of fittings. Elbows, couplers, various box entries. Use Compression type fittings when possible! These are easier to work with, stronger, watertight, and just plain nicer. When you put a piece of conduit in a fitting, take the time to COMPLETELY de-burr it with a rat tail file first. Do not leave any sharp edges to snag the wires. And, do not overfill the conduit! 30-40% percent is a good rule, but check with your code.
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| Conduit Benders | Assorted Conduit Fittings | Boxes, and 4" Dual Outlet Cover |
I just want to repeat again. Use quality outlets and switches. Leave the cheap junk behind. You wont have to fix it, your tools will run better, and your shop won't burn down! Place plenty of outlets! I use almost exclusively a four inch box that holds two duplex receptacles. These can be pre-wired, and then attached. (See picture). As noted under lighting, I placed outlet boxes in the ceiling joists where light fixtures will go, and then just plug in the fixtures. I also have a couple of other outlets up there for things I may want to hang from the ceiling (PC Speakers), as well as above the worktables for cord reels, etc. Now is the time to place plenty of outlets everywhere. Consider wiring a few in the ceiling to switches to control specialty or task lights. Ask your electrical inspector to see if you can put that many outlets on one circuit, the interpretations seem to vary.
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| Cheap outlet on left, spec grade on right | Another comparison of outlets | Cheap switch is on left |
This topic is important enough that I am dedicating a section to it. I placed outlets (4" box with one duplex receptacle) at each location I wanted a light. On a couple of these, the second duplex outlet is wired to a wall switch so I can control task and specialty lighting. I also have one outlet box controlled by switches for red and blue lighting, and a disco ball - Yes, it is an all purpose playroom! Honestly, I use the red lighting sometimes for special projects, or to light the shop at night with the doors open while I am stargazing, or playing with lasers, etc.
As mentioned above, for conduit use a quality THHN stranded copper wire. Get the right size, I.E. 12 gauge for 20A/115 volt, 14 gauge for 15a/120v. It should have a temperature rating of 90 degrees Centigrade (or 105 Degree). And, if you use romex (Type NM-B), keep in mind a lot of the romex for sale at the Home centers is NOT code approved! Make sure it is UL Approved, has a 90c temperature rating, (the B in NM-B, if it just says NM, it is 60 degree).and that the wire is marked every foot with Manufacturer and type. And do not forget romex is color coded since 2001: 14 AWG is White, 12 AWG is Yellow, 10 AWG is Orange, 8 AWG is Black. If you use romex do not forget to anchor it properly, and observe the exposure and raceway rules. While on the topic, although I use side cutters to strip a lot of wire, for your electrical wiring, get and use a wire stripper to avoid nicking the wires, again this is not the place to cut corners! -
As the shop was being built, I took the time to run PVC Conduits under the floor to where the worktables will be, and where my table saw will end up. I ran a 4" PVC, and 2 or more 1 1/2" PVC to each location, starting at the closest wall. The conduits have a threaded fitting even with the floor. This allows me to cap them off, and have a flat floor if I want to, and to attach tubing extensions when they are being used to keep water and dirt out. This required a little care getting everything even, and my cement contractor was very tolerant also. When installing, I used a couple of Rebar stuck in the ground to support them, and put Duct tape and grease around the outside of the screw part, so it would not get cemented in. Every day I am thankful I did this. It took about 75 bucks, and a couple hours, but there are no cords to trip over! I can run a standard heavy duty extension cord through the 1 1/2" pipe. Likewise, a 1/4" air hose fits through just fine. The big pipe is for dust collection, and at the center table it is used for my network, speaker and misc cables. Each conduit is separately run to the wall, no fittings or tees! And, do not run misc low voltage wires in the same Conduit as the AC Cord! That can be very dangerous! And against code.
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| This is the conduit installed before the slab was poured | |||
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| And here it is after the slab was finished. Click on a pic for a bigger one. | |||
I was originally going to put some tips for wiring here. But, I feel strongly about this. If you do not have experience wiring, if you are uncomfortable, or if you are not sure about basic wiring practices (including Code issues, grounding, etc) then hire a Licensed Pro. Electrical wiring done improperly can kill someone, burn your house down, and, at the least cause all kinds of issues with your tools, test equipment, and experimenting. Additionally, if something would happen, it is possible your Home Insurance would not cover losses due to wiring by an unlicensed person - No matter how good it is! My suggestion, if you go this route, is to find a Contractor, and talk to them. Even pay for an hour or so visit to your project. Discuss the parts of the project you can do, and get their recommendations on parts and supplies. You very well may be able to do the Mechanical stuff, conduit installation, mounting of boxes, and even pull the wires. Then let the electrician actually connect it up. This will save you money, and allow you to take the time to do the installation part to your own standards.
Again, If any of these techniques are unclear or unfamiliar, consult a licensed electrician! Be safe! This is not the place to scrimp on quality and experience.
Here are some book recommendations that may help you with wiring your shop, and learning about electrical wiring.
And a couple of videos on electrical wiring!