Wiring a shop: How many circuits?

[Andy McKenzie]

Hey folks. It looks like I'm actually going to be able to do the work necessary to add electricity to my garage this summer, meaning it will be usable as a shop. (Finally, a space where I can run a bandsaw!)

I'm looking for input on number of circuits. The background here is that I haven't had a space where I could use powered tools in something like five years, so 99% of what I'm doing now is hand tool work. I have a bandsaw, drill press, hollow chisel mortiser, and chop saw. The first three will be pretty much set up permanently, and the chop saw will come out for construction projects. I probably won't add any new power tools, except possibly a router table, in the next year, but I may add some machining tools (a milling machine and metal lathe) eventually. The garage currently has one circuit, of decaying 1940's era armored cable with no ground. That's getting ripped out, and a new subpanel will be installed with a run back to the main panel.

My plan at the moment is:
1) Two 20 amp circuits, with adjacent boxes at each drop point. That way I can plug a task light into circuit one, and the bandsaw into circuit two, or something like that. They'll get different colored faceplates and outlets.

2) One 15 amp circuit for lighting.

3) I'll prep for a single 240V circuit, with the expectation of wiring it if I get equipment that needs it.

4) I'll make sure there's room on the subpanel to do electric heat if I decide that's necessary.


I have an uncle who was an electrician to make sure I get wiring sizes right, but he doesn't run a wood shop and can't tell me what I've overlooked in that sense.

So: what am I forgetting?

[Marty Tippin]

My advice would be to use double gang outlet boxes and put both 20A circuits next to each other in the same box. In my shop, I alternated the circuits every 4 ft or so and it has been inconvenient pretty much every time I need to do something.

If your wiring is going to be in conduit you've got lots of flexibility to add stuff later but if it's buried in the walls, you really want to get it right the first time.

[russell lusthaus]

When i wired my shop, all outlets on a wall are at least higher than 48 inches for plywood leaning clearance, and I also placed many of my outlets on the ceiling or otherwise overhead. I find I use the over head outlets way more then the wall mounted. IMHO - you cant have to many, outlets or circuits, and make all of them double duplex boxes - why would you not?

Russ

[Andy McKenzie]

My advice would be to use double gang outlet boxes and put both 20A circuits next to each other in the same box. In my shop, I alternated the circuits every 4 ft or so and it has been inconvenient pretty much every time I need to do something.

If your wiring is going to be in conduit you've got lots of flexibility to add stuff later but if it's buried in the walls, you really want to get it right the first time.

Thanks for the advice!

I hadn't been able to figure out whether it was up to code to do two circuits in one box, but the non-code consensus on a few forums seemed to be that it was a lousy thing to do to the next person to work on the wiring. I'd figured I'd put a pair of boxes every six feet or so, with circuit one on the right side of the stud and circuit two on the left side.

As to conduit... I hadn't come to a decision yet. My thinking is that either I should run conduit, or I should run the wire at ceiling level and drop down to whatever height I decide on for outlets at the outlet (probably around 4 feet). Being a shop, I'm expecting to do a lot of drilling in the walls, and knowing I won't hit a wire anywhere is worth quite a lot. Either way, the supply run from the house is going through oversized conduit with a couple extra pull-strings, and I may run a second conduit for future low-voltage upgrades like network, since wi-fi doesn't really reach the garage very well.

[Andy McKenzie]

When i wired my shop, all outlets on a wall are at least higher than 48 inches for plywood leaning clearance, and I also placed many of my outlets on the ceiling or otherwise overhead. I find I use the over head outlets way more then the wall mounted. IMHO - you cant have to many, outlets or circuits, and make all of them double duplex boxes - why would you not?

Russ

Thanks! I was figuring on mounting the boxes at around 4', to clear machinery, benches, and the like. I don't use much plywood, but that's an excellent point, and I may add 6" to the height. I still figure I'll put in mostly single boxes, but I'll likely do a few doubles along the back wall, where most of the machinery will be.

[Steve Peterson]

If you are planning to run new wire back to the main panel, then upsize it for future usage. You can run quite a bit of circuitry on a 50A breaker. I have a 5hp tablesaw and a 5hp cyclone dust collector plus lights running at the same time on a 50A subpanel.

I used alternating circuits for 120V outlets and it worked fine for me. Most of my tools were stationary. I would only need to pick an outlet when plugging in a shop vac and a router. My outlets were spaced every 32 inches so one was always nearby.

Steve

[Andy McKenzie]

If you are planning to run new wire back to the main panel, then upsize it for future usage. You can run quite a bit of circuitry on a 50A breaker. I have a 5hp tablesaw and a 5hp cyclone dust collector plus lights running at the same time on a 50A subpanel.

I used alternating circuits for 120V outlets and it worked fine for me. Most of my tools were stationary. I would only need to pick an outlet when plugging in a shop vac and a router. My outlets were spaced every 32 inches so one was always nearby.

Steve

The plan is a 60 amp subpanel, so yeah... there should be power to spare, given how light my power-tool use is. Sounds like I'm on the right track with two circuits, though.

Thanks!

[Chris Padilla]

You may be a bit on the small side now for your needs but you need to consider future expansion should you really start getting into the hobby. Only you will know where this might all go. Just make it easy for you to add additional circuits. For those of us with more power-hungry tools, we need to think about dedicated circuits for: air-compressor, dust collector, and heater/ac. All those could be running at the same time as you are running a band saw or table saw or your jointer or planer. Most dedicated circuits will be of the 240V 20A and 30A variety but the air-compressor might be on a 120V/20A circuit. Lights should be on their own circuit and some folks will even put them on two different circuits. It is all about minimizing being in the dark should something happen.

If you REALLY want to future-proof your general circuits, wire everything with 10/2 or 10/3. Doing this will ensure that you can change any circuit to a 240V/30A should the need arise. Otherwise, that oversized wire will do all your 20 A and 15 A circuits just fine.

Lots of ways to approach this but think hard about future changes and needs.

[Jay Larson]

In the shop area, I put two 20A circuits in alternating each outlet every 4' or so. I also put in a 240V outlet for the table saw. I put the lights on a 15A circuit and a separate 15A circuit in my desk area. I figure that way I don't need to have any radios or computers on a 20A one.

There is also a 240V circuit for a compressor out in the garage area, along with another 20A circuit. Plus I have an outlet from each of the shop 20A circuits in the garage area. Don't think I can be in both places at once...

[Steve Meliza]

Use a subpanel with at least 12 spaces, not one of those dinky 6 space panels that you'll fill up with no room for expansion. I have an attached garage so when the main panel started filling up during a recent remodeling project I was able to drop a few new circuits into the subpanel as well. You could use NM-B 6/3 wire and a 60A two-pole breaker to supply the subpanel.

Outlets at ~48" off the ground not just for plywood but for convenience and saving your back. Hold your arm out level, it is 12" above the floor or more like 48" above the floor? I also agree that it is a good idea to run a pair of 120V circuits with a pair of duplex outlets at each location.

I ran 1/2" EMT (metal conduit) about 52" off the floor and every 4' I put in a 4" square metal box to hold the pair of duplex outlets. All of the outlets on the left side belong to one circuit while all of the outlets on the right side of boxes are from the other circuit. My horizontal conduit runs keep the wall free of vertical drops of wiring, that makes it easier to use the upper wall space as it is bare and free of obstacles. I have a second run of conduit just above that one the serves 3 home run circuits, two 120V and one 240V.

My suggestions are based on what I've done and work very well for a one man shop where I'm just as likely to use a Disston as a Delta. My only 240V load is a 1.5HP 8" jointer that easily runs on a 20A circuit. One home run is for the air compressor and the other I typically plug the dust collector into. The table saw or lunch box planer get plugged into the nearest 120V general use circuit (all of my tools are mobile). Change the circuit voltages and ampacities as needed to match your tools.

1. 20A/120V for general use (#12 wire)
2. 20A/120V for general use (#12 wire)
3. 15A/120V for lighting (#14 wire)
4. 20A/120V home run (#12 wire)
5. 20A/120V home run (#12 wire)
6. 20A/240V home run (#12 wire)

[Steve Meliza]

If you REALLY want to future-proof your general circuits, wire everything with 10/2 or 10/3. Doing this will ensure that you can change any circuit to a 240V/30A should the need arise. Otherwise, that oversized wire will do all your 20 A and 15 A circuits just fine.

I don't agree for general use 120V circuits as they might have a dozen or more duplex outlets on them and therefore are not candidates for conversion to 240V/30A. As such using #10 wire for general use circuits with 5-15R or 5-20R duplex outlets is an unnecessary expense, a pain to work with, and more likely to cause fill violations. In fact, the outlets aren't even rated for use with #10 wire so I think you'd have to pigtail with #12 wire. Using #10 as future proofing on a 240V circuit or 120V home run makes more sense to me, but keep in mind you don't need #10 wire till you bring that 5HP monster home.

[Andy McKenzie]

You may be a bit on the small side now for your needs but you need to consider future expansion should you really start getting into the hobby. Only you will know where this might all go. Just make it easy for you to add additional circuits. For those of us with more power-hungry tools, we need to think about dedicated circuits for: air-compressor, dust collector, and heater/ac. All those could be running at the same time as you are running a band saw or table saw or your jointer or planer. Most dedicated circuits will be of the 240V 20A and 30A variety but the air-compressor might be on a 120V/20A circuit. Lights should be on their own circuit and some folks will even put them on two different circuits. It is all about minimizing being in the dark should something happen.

If you REALLY want to future-proof your general circuits, wire everything with 10/2 or 10/3. Doing this will ensure that you can change any circuit to a 240V/30A should the need arise. Otherwise, that oversized wire will do all your 20 A and 15 A circuits just fine.

Lots of ways to approach this but think hard about future changes and needs.

I gave up my table saw when I moved, and haven't missed it once. I did wish I had a router table while I was making a pair of toychests for my nephews (roughly 36x20x25, frame and panel), given the number of grooves I needed to cut. A compressor is something I hadn't thought of yet, and is a good reminder. Heat/AC I'll definitely need... the space is currently unheated and uninsulated: insulation will go in this summer, I hope, with heat/AC to follow once my budget has recovered.

In the shop area, I put two 20A circuits in alternating each outlet every 4' or so. I also put in a 240V outlet for the table saw. I put the lights on a 15A circuit and a separate 15A circuit in my desk area. I figure that way I don't need to have any radios or computers on a 20A one.

There is also a 240V circuit for a compressor out in the garage area, along with another 20A circuit. Plus I have an outlet from each of the shop 20A circuits in the garage area. Don't think I can be in both places at once...

Good to know!

Use a subpanel with at least 12 spaces, not one of those dinky 6 space panels that you'll fill up with no room for expansion. I have an attached garage so when the main panel started filling up during a recent remodeling project I was able to drop a few new circuits into the subpanel as well. You could use NM-B 6/3 wire and a 60A two-pole breaker to supply the subpanel.

Outlets at ~48" off the ground not just for plywood but for convenience and saving your back. Hold your arm out level, it is 12" above the floor or more like 48" above the floor? I also agree that it is a good idea to run a pair of 120V circuits with a pair of duplex outlets at each location.

I ran 1/2" EMT (metal conduit) about 52" off the floor and every 4' I put in a 4" square metal box to hold the pair of duplex outlets. All of the outlets on the left side belong to one circuit while all of the outlets on the right side of boxes are from the other circuit. My horizontal conduit runs keep the wall free of vertical drops of wiring, that makes it easier to use the upper wall space as it is bare and free of obstacles. I have a second run of conduit just above that one the serves 3 home run circuits, two 120V and one 240V.

My suggestions are based on what I've done and work very well for a one man shop where I'm just as likely to use a Disston as a Delta. My only 240V load is a 1.5HP 8" jointer that easily runs on a 20A circuit. One home run is for the air compressor and the other I typically plug the dust collector into. The table saw or lunch box planer get plugged into the nearest 120V general use circuit (all of my tools are mobile). Change the circuit voltages and ampacities as needed to match your tools.

1. 20A/120V for general use (#12 wire)
2. 20A/120V for general use (#12 wire)
3. 15A/120V for lighting (#14 wire)
4. 20A/120V home run (#12 wire)
5. 20A/120V home run (#12 wire)
6. 20A/240V home run (#12 wire)

Yeah. I understand why houses don't have outlets at shoulder level, but I really wish more garages did. I was already planning on putting outlets at least 3-4 feet up to keep them above benches or tools, and I'll likely bring them up a little further now that I've thought about dealing with sheet goods.



Thanks again to all of you!

[Chris Padilla]

I don't agree for general use 120V circuits as they might have a dozen or more duplex outlets on them and therefore are not candidates for conversion to 240V/30A. As such using #10 wire for general use circuits with 5-15R or 5-20R duplex outlets is an unnecessary expense, a pain to work with, and more likely to cause fill violations. In fact, the outlets aren't even rated for use with #10 wire so I think you'd have to pigtail with #12 wire. Using #10 as future proofing on a 240V circuit or 120V home run makes more sense to me, but keep in mind you don't need #10 wire till you bring that 5HP monster home.

Properly laid out and thought about, all these things could still work with #10 everywhere. I don't know about the wire size rating you call out. I wired all my 5-20R with #10 and didn't have a problem but I'd have to check and see if they are rated for it or not--honestly do not know. Now if you go with conduit, then you can pull whatever you like whenever you like. With Romex, it takes a bit more planning.

Remember that Murphy rules the universe...you'll need/want it if you don't have it!

[Thomas Bank]

The one thing you don’t say is how big the shop is - square footage would be a bit of a determining factor for some things.

Definitely have the lighting on a separate circuit. I’ve seen too many places where you pop a breaker with a tool and then are left in the dark to boot. Having two lighting circuits may be overkill. What are the chances you’d pop a breaker on a lighting circuit? Particularly with the low draw of T5s, T8s, and LEDs these days compared to old incandescent setups. But depending on size, it may be useful so you don’t have to light everything up if you’re only working on one side.

Alternating circuits for receptacles is something I’ve done and it seems to work well. I share the workshop with my girlfriend and my father is sometimes over, so it is nice to be able to each be doing our own thing without overloading anything. I also put in receptacles every four feet. That way I can pretty much plug something in anywhere in the shop without using an extension cord.

I’ve ended up with more 220V equipment than I had initially planned on. Fortunately, I was fairly liberal with 220V circuits too, so I’m in good shape. My shaper, tablesaw, planer, and dust collector are all 220V.

The only thing I didn’t quite plan on was I ended up with a 110V 20A bandsaw and thickness sander. Fortunately, I had done the receptacles in 10ga, so I could swap the 15A circuit out for 20A.

[Mike Heidrick]

Separate DC circuit
Separate air compressor circuit
alternating 120V 12ga 20a circuits
alternating 240V 10ga 30a circuits
Lighting on its own circuits - 20A ea
Separate circuits for electronics
Separate circuit for fridge
Emergency lighting circuit ( I share that circuit with my garage door openers)
Considering any ceiling circuits? Drop down
Need outdoor lights? outdoort power?
Some switched wall outlets for signs or wall task lighting?
If you are doing it put in a large panel with plenty of room all you have thought about now X2
Size main breaker accordingly