Written By Bobby. On Jan 21. In Shop Systems,Workshop Layout

Are you tripping over power cords? Do you worry about what you’ll do when you buy a 240V table saw when you only have 120V outlets? Are you routinely tripping circuit breakers?

As part of your overall woodshop design, assigning each tool to a circuit and positioning outlets to handle your current and future layout is one of the first steps. If your wiring is run in your walls, you have to do that first before you insulate and close them up.

I wired up my garage as soon as I moved in. But since I’m now insulating the walls (to increase shop time in the winter and summer months), I don’t want to be stuck with an electrical layout that won’t meet my future needs.

The outlets for my table saw right now cause a power cord to run across the floor in a major walking route for me, so I want to put in a ceiling outlet and run the power cord with the dust collection flex hose. I don’t have enough 240V outlets to accommodate my new drum sander, future 20″ bandsaw, or jointer. Before I close up the walls, I want to make sure that the wiring is as close to what I want and will want as possible.

You can have an electrician do the work or do it yourself if you know what you’re doing, but you should at least design it because only you know what you’ll be doing in the shop, and you can better communicate with the contractor.

How To Get Started Today

Where do you start for all this? Well, I started at my electrical panel. I opened it up, and decided to figure out what circuit breaker served what outlets. So, I used my electrical outlet tester and sniffer to check each outlet. I turned off one breaker at a time and tested various outlets to see which ones were off. Then I used my P-Touch labeler to tag each breaker in the panel so I didn’t have to test everything again. I did this for the whole house and the shop. It took about 3 hours (there were a few mystery circuits in the house).

Once everything was labeled, I figured out how many spots were left in my panel to add circuits. I didn’t want to change any of my house circuits for now, so I left that alone. I have a total of 10 available for the shop, including one 240V circuit that was already installed.

Next, I made a list of all of my machines that need power, and included all the misc. things in another list. I indicated the voltage and amp draw of each. I also listed future tools that were on my woodshop layout. If a machine might be upgraded to a 240V type later, you’ll need to account for that outlet and circuit, and just install both the 120 and 240V, on separate circuits of course.

WoodChip Tip: For some of my tools, I looked at the nameplate for the amps, but sometimes I just looked it up online. For some stuff, you can estimate it or calculate it. If you know the Watts, (such as my radiant heaters are labeled at 1500 W), you can calculate the # Amps by taking the Watts and dividing by the Voltage. Of course, you should check with the manuf. for the amperage first, and then with an electrician once you list what you would like to be on each circuit. Make sure you’re not overloading anything or violating the maximum capacity rules.

Subpanel?

I don’t really see the need to add a sub-panel at the moment, but I can easily do so later. I’m mainly interested in getting the correct wiring in the wall routed to the electrical panel area. I’ll keep the access to this area open so I can add a sub panel later. The only reason I may add this is if I need another 240V circuit for a dust collector upgrade, since there is no more room on my house panel. At that point, I might as well just put the whole shop on its own panel with plenty of room for all the circuits I’ll need. For now I’ll be adding an extra 240V outlet where the dust collector is and a junction box for future connection.

You can do the same thing, or add your sub panel now. If I do add one, I’ll have an electrician do it all; I don’t want to mess with the main power coming from the utility company to do it.

120V vs. 240V

Most of what you have might be 120V, but most serious hobbyist and small business woodworking machines run on 240V, such as cabinet saws, jointers, drum sanders, wide belt sanders, larger dust collectors, and resaw bandsaws. Because of this, I suggest you have at least one 240V circuit pre-wired in your shop, and that you allocate the panel space for a double-pole breaker. Two of these circuits is better to have available.

In my case, I only have room for one, and since my dust collector is 120V and works great, I’ll never have two 240V machines running at the same time.

15A vs. 20A

Unless you have a welder or other machine that needs it, you probably don’t need more than a 20 amp breaker for any given circuit. My 240V outlets and its associated breaker is 15A, because nothing on that circuit draws really close to that amperage. However, I ran 12 AWG wiring for the 240V.

The majority of my 120V circuits are 20A, because many of the tools draw really close or just over 15A. I ran 12 AWG wiring for the 15A circuit in case I need to upgrade it to 20A later. 12 AWG is ok for 20A, and 14 AWG is ok for 15A, but I would use 12 AWG for even 15A circuits in case you want to upgrade. Don’t try to save money in places you can’t access after closing up the wall.

Each receptacle and switch has an amp rating as well, so be careful about the rules of when you can install these outlets with what breaker and wire size. Definitively don’t install 14 AWG wiring and protect it with a 20A breaker. The breakers are designed to prevent more amperage from going through the wire than it can handle, so you must install a breaker that limits the amp draw to the installed wiring’s rating. I recommend either really read a lot, or have an electrician review what you’re planning on doing before you start (unless you’re already pretty savvy with electrical work). I still bought an A-B-C wiring book to make sure I’m not missing anything, and I ran my ideas by an electrical engineer.

Which Circuit Does This Go On?

The way I did this was ask myself what things would be on at the same time? An easy one was the dust collector, which will be on when most other tools are also on. Since the dust collector draws a large amount of power, I’ll likely trip a breaker if any other tool is on that same circuit. So, I assigned it a dedicated circuit right away. Next, I thought about the air compressor. That thing cycles on and off with a mind of its own. I certainly don’t want to trip a breaker during a machining operation because the compressor suddenly turns on.

Also, heating and cooling equipment usually has a high amp draw, especially cooling equipment or electric-based heaters. So, make sure you know the amp draw of those items, and maybe only attach light power items on those circuits. For me, since my attic fan is controlled by a thermostat, it won’t be on during cold weather when the radiant heaters will be on.

There are times when two things could be on at the same time but they have a low amp draw. The air cleaner I want only draws 3.9 amps. So, it’s ok that this is on the same circuit as the miter saw or a misc. hand power tool.

Now, as a safety thing, I decided that the main lights should have a dedicated circuit. I don’t want them to dim when I turn something on. I really don’t want them to all turn off if I trip the breaker. I have some lights (“secondary lights”) that I put on another circuit just in case.

I only have one 240V circuit, so I’m ok with that for now, even though I’ll add provisions for a second 240V circuit. As I’m designing so far, I’ve used up a circuit for the 240V, the dust collector, the air compressor, and the main lights for a total of 4. I have 6 circuits left to assign. With this, I decided to divide up the rest of the items on my list (see below), making sure that if two things are on at the same time I’m not exceeding the amp rating of the breaker.

I decided to add a key rule to my circuit allocation strategy. I don’t want an outlet of one wall to share a circuit of another wall’s outlet. That way, I know that only outlets on the same wall could possibly share a circuit. So, if I plug something into the North Wall, and run it at the same time as something on the East Wall, I probably won’t blow a breaker.

Below is my complete list of all the things that I considered for my shop circuiting:

240V Equipment:

Table Saw

Jointer

Drum Sander

Future 20” Bandsaw

Provision for a 2nd 240V Outlet for Dust Collector

120V Equipment

Dust Collector

Shop Vac

Air Cleaner

Main Lights

Secondary Lights (Different Circuit than Main Lights)

Future Outbuilding (Finishing and Lumber Storage)

14” Bandsaw

Planer

Lathe

Router Table

Scroll Saw

Oscillating Spindle Sander

Belt-Disc Sander

Mortiser

Drill Press

Assembly Table Power Strip/ Charging Station

Info Station Power Strip

Workbench Power Strip/ Charging Station

Sharpening Station

Mitre Saw

Future Panel Saw

Radiant Heaters

Misc. Items:

Shop Attic Fan

House Attic Fan

Garage Door Opener

Sprinkler Timer

Exterior Lights

Future Loft Outlet

TV, DVD Player, iPod Dock, Radio

Internet/ Cable TV Processor Box

(2) Exterior Outlets (Good for outdoor sanding, garden equipment)

What I decided to do is shown here (click on this to see a PDF of my AutoCad Plan). You can see that I’ve added quite a few ceiling outlets. This is because I don’t want to trip over power cords. Of course, I have to pay attention to where the infeed and outfeed is, and how I’ll maneuver lumber around without bumping into a dust collection flex hose and wire running up from the machine to the ceiling. But, it’s better than having a bunch of cords criss-crossing the floor.

The hardest part of assigning each item to a circuit was the radiant heaters. Each of these draws 12.5A, so they had to go on different circuits. But, even when put on a 20A circuit, there isn’t a lot of capacity left for heavy duty equipment on that circuit. So, I placed smaller items on those circuits like secondary lighting, the house attic fan, one of the future Finishing/ Lumber Storage outbuilding circuits, and the exterior outlets.

By looking at what things could be on at the same time, I began to do some trial and error on paper to see what should go on a particular circuit. After assigning the dedicated circuits, I started with the assumption that each wall would get one circuit. If it had stuff on it that could be on at the same time, and exceed the breaker, I took items off until I knew that breaker wouldn’t trip.

I would have like maybe one more circuit, so I may run wire in advance in case I get a sub panel to make this possible. Be sure to use junction boxes so you can access the wiring later.

Since I plan to build a small outbuilding in my backyard for finishing and lumber storage, I put two separate conduits through the shop walls with an access from the outside. I am running 12 AWG wire from two separate circuits, one for lights and fans, and one for spray equipment.

Outlet Locations

Ok, once I had the list of what circuits are connected to what machines, it was time to place outlets. Of course, for tools not located on walls I opted put those outlets on the ceiling. For the workbench, I think I’ll use one of those cord reels so I can connect it to a power strip when I need to. That way, I’ll minimize the number of vertical power cords in the shop. Where the vertical cords will exist, I’ll locate the ceiling outlets out of the traffic paths and infeed /outfeed areas.

I suggest drawing the realistic power cord routing from each machine on your layout to each outlet so you can see what you’ll wind up with.

WoodChip Tip: For machine mobility, and a clean look, I am zip-tying the power cords to the dust collection flex hose where they both go up to the ceiling. I am leaving enough slack so that they don’t interfere with stock moving across the tool, and so that I can freely rotate or slide the machine enough. For the dust collection, you can use a ball-joint type connection to avoid breaking the seal on your sheet metal elbows. Also, some people use a twist-lock type plug to prevent it from popping out of the outlet. I don’t want to use these because if I accidentally move the machine too far, I want the plug to disconnect before anything vital is broken.

For machines located against the wall, I am making sure that there is an outlet directly behind the machine. If there is too much space between those outlets, I’ll be adding an extra one. For certain areas, such as behind the Assembly Table and at the Router Table, I am putting quadruplex outlets (those can accommodate 4 plugs). Don’t forget that you will need an area to accommodate a charging station or two. To me the logical places for those are the Workbench and Assembly Table.

From some outlets, I am running extra wire to a junction box, but the wires won’t be connected to anything on either end for now. This way I can tie something else to that circuit in the future. Make sure the outlet boxes you use have adequate room for the wire you’re using.

If you have a storage loft, or an office planned, don’t forget to run some wire for outlets, switches, and lights in those spaces. If you are planning a small bathroom, add a wire for an exhaust fan as well. There are codes that specify what type and where outlets and switches are installed in office and bathroom spaces.

WoodChip Tip: I use Ground Fault Circuit Interrupter (GFCI) outlets wherever required, because the garage is considered in the code to be a “wet” environment. So all wall-mounted outlets are definitely GFCI outlets. You can have one GFCI outlet and subsequent outlets down the line be regular outlets but all are protected the same way if you wire it right.

Don’t Forget Switches and Controls

Some outlets I realized I want controlled by a switch, such as the lights. But, I’ve also connected each exterior outlet to a switch as well. I want to be able to disconnect the power when I’m not using them.

The attic fan is connected to a line-voltage thermostat. When it reaches say 90 deg., the fan will turn on. But, sometimes I want to turn it off. So I’ll provide a switch.

My dust collector is plugged into a remote control switch box, and I have a keychain remote that I pick up when I walk into the shop. This saves tons of time when I go from tool to tool. All I have to do is close the blastgate on the machine I’m done with and open it on the next. In the future, I want to upgrade to automatic blastgates (this can cost $, but I say it’s worth it if you have the cash).

The air cleaner will also have a remote control. I’ll store that on the wall near the shop entry door. If I put a belt clip on it, then I can have it with me when I need it.

Final Thoughts

The above represents my thoughts as I went about my design. This was what was holding up my insulation job, so it’s what I’m currently doing. Your shop will be different, and you’ll have different building and electrical codes to deal with. As you get permits or run your design by an electrician, they’ll point out mistakes or code violations with your design.

As an engineer in the building industry, I find most of the codes are there because something bad happened to cause it to be written. Occasionally you’ll run into a plan checker or inspector who will have a whacky interpretation of the code, but on the whole you’ll want to comply with everything that covers your jurisdiction. An electrical fire is really easy to create.

Also, if you’re going to do this yourself, get all the testing equipment mentioned above, and carefully check how-to books to make sure you’re doing it right. If you’re having an electrician do this, then you’ll at least know exactly what you want and need by designing it first.

It’s probably a good idea to take this post’s ideas and incorporate the ones that work for you into your design, then post your questions in the comment section below so other woodworkers can get even more out of the discussion.

Of course, the reason I’m writing this post is to help you with your design, and let you take advantage of the research and thought that went into my design. But, on the flip-side, many of you have experiences or knowledge that would help me as well. Do you have any suggestions to help woodworkers avoid future frustrations or safety hazards? Do you see something in my plan that you think I should change?

PDF of my Electrical Plan

Connect with me on Facebook, and follow me on Twitter for more ninja tips to Optimize Your Woodshop!

Gotta get more clamps,

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