Shop electrical outlets?

[Steve Mathews]

I'm just beginning to organize my woodworking area in a section of my barn/outbuilding and have a few questions about electrical outlets. Some of my machines operate off of 220v single phase. I was thinking of placing both 110v and 220v outlets in the area. Is it possible or recommended to place a couple of 110v and one 220v outlet in one double gang box? Separate circuits would be used. What spacing is recommended between the outlets?

[Wade Lippman]

Depends on what you are talking about. There is no reason you can't put 120 and 240 ( but not 110 and 220, which don't exist) in a double gang box, but the spacing is pretty much fixed. Are you talking about the distance between boxes? Put them where ever you will need electricity. Just make sure you have enough circuits. Lay your workshop out before you start doing the electrical.

[Ken Fitzgerald]

Steve,

I don't know if code allows 120 and 240 in the same box. I just don't know.

When I built my shop, I placed all my wall outlets about 50" above the finished floor. I can stand a sheet of plywood up against the wall and still have access to the outlets.

I placed 120v outlets about every 4' along each wall. I have 2 circuits going down each wall and every other outlet is on the other circuit. In other words no two adjoining outlets are on the same circuit but there are only two circuits feeding that long wall and 1/2 of the connecting short wall. A total of 4 separate 120v circuit breakers handle all the wall outlets. A 5th circuit breaker handles a series of ceiling 120v outlets.

My lighting is on 2 different circuits and controlled by 4 different switches. Thus I don't have to have all the lights on but if I do and a lighting breaker was to trip, I won't lose all the lighting.

[Mike Henderson]

Based on my experience with my shop, I'd put the outlets about 48" to 50" from the floor and I'd put in a lot of outlets. The reason is that you'll change around your shop one day and running new outlets is a pain once you close in the walls. I think I put mine about 4" apart. When I was putting mine in, there was one place where I thought it was unlikely that I'd use the outlet, but outlets are cheap and I put it in. Turns out it's really convenient when I plug in my vacuum press.

Err on the side of too many, rather than too few.

One other thing, I found that I preferred my 240V outlets low on the wall, and my 120V outlets higher (48" to 50"). The reason is that the 240V cords stay plugged in and it makes a shorter run to the tool that way. With the 120V outlets, I'm always plugging and unplugging, so higher is more convenient.

Mike

[Oh, and I did the same as Ken. Outlets next to each other are on separate circuits.]

[Bob Michaels]

Steve, my personal preference, and what I did in my own shop was to place an abundance of 120 v duplex receptacles about 40" above finish floor in their own boxes. I also have 6 or 7 240 v single twist lock receptacles in their own boxes, some within 6" of the 120 v outlets. However, they are never mixed in the same electrical box. I am not an electrician but IMHO I think best practice would dictate keeping these separate. Also, It may be difficult finding box cover plates with both duplex receptacle and 240 v punch outs on a double plate. Just my 2 cents worth.

[Rod Sheridan]

I'm just beginning to organize my woodworking area in a section of my barn/outbuilding and have a few questions about electrical outlets. Some of my machines operate off of 220v single phase. I was thinking of placing both 110v and 220v outlets in the area. Is it possible or recommended to place a couple of 110v and one 220v outlet in one double gang box? Separate circuits would be used. What spacing is recommended between the outlets?

Yes, it's a great way to wire your shop, both can be fed from the same circuit if it's a 15 or 20 ampere multi-wire branch circuit............Rod.

[Kent A Bathurst]

There is such a thing as dual-voltage duplex recepts. One is 120, the other 240.

Where I need 240, I almost never needed 2 - the big dogs are not that close together, with one exception. So I always put in the duals. Sooner or late, I am going to want to plug some 120 thing in there - a shop vac on a shop tour, a fan, some temp floodlights for finishing, etc.

[Mike Henderson]

Yes, it's a great way to wire your shop, both can be fed from the same circuit if it's a 15 or 20 ampere multi-wire branch circuit............Rod.
In the US, especially if your shop is in the garage, every 120V outlet must be GFCI controlled. If you go with a multi-voltage, multi-wire branch circuit (two hots and a neutral), you'll have to put a GFCI outlet at every box. GFCI works by summing the current. If you used a 240V circuit with a neutral and ran 120V between either hot and the neutral, the currents wouldn't sum to zero at any point except the end point of each 120V outlet.

Mike

[Mike Schuch]

There is a very simple problem with putting a double 120v outlet in the same box as a single 240v outlet. Nobody makes a face plate that covers a double and single outlet in a double gang box. You would have to drill/cut your own custom face plate.

[John Stankus]

There is a very simple problem with putting a double 120v outlet in the same box as a single 240v outlet. Nobody makes a face plate that covers a double and single outlet in a double gang box. You would have to drill/cut your own custom face plate.

You mean like this?

http://www.kyleswitchplates.com/combo-duplex-outlet-single-1-62-20a-round-receptacle-cover-plate/

[Jim Finn]

I put fourplex 120Volt every four feet in my shop and ran all of them with surface mounted conduit so changes are easy if I need them.

[Rod Sheridan]

In the US, especially if your shop is in the garage, every 120V outlet must be GFCI controlled. If you go with a multi-voltage, multi-wire branch circuit (two hots and a neutral), you'll have to put a GFCI outlet at every box. GFCI works by summing the current. If you used a 240V circuit with a neutral and ran 120V between either hot and the neutral, the currents wouldn't sum to zero at any point except the end point of each 120V outlet.

Mike

Mike, you can use a multiwire branch circuit with a GFCI in the first box and feed all downstream 120V receptacles from it.

Use a red and a black conductor for the 240V circuit, and a blue and white for the 120V.
Regards, Rod.

[Clay Crocker]

There is a very simple problem with putting a double 120v outlet in the same box as a single 240v outlet. Nobody makes a face plate that covers a double and single outlet in a double gang box. You would have to drill/cut your own custom face plate.

This is not exactly true. They do make a combo face plate. Also, I bought "modular" face plates when I wired my shop about 10 years ago. With these, you snap together the correct face plate for each gang prior screwing the face plate down.

[David Ragan]

When finishing my small shop, I had read that the most common gripe folks had was not enough outlets.

So, going around the entire shop, I put an outlet on each and every stud. The lower level @ I think 18" above the floor (Code), alternating with about precisely 4' above the floor. All GFCI. 6 outlets per circuit.

All the 220 are 10 gauge and separate entirely.

lights on their own circuits

Be sure you make a master circuit drawing so you can track down any problems.

So far, so good!

Oh, if your walls are finished, I put those little plates on the studs over area where wire runs through. Has saved me drilling through a cable.

[Jim Dwight]

My shop has many fewer circuits than the others but it's the second shop in a row I've done this way and I used the last one 15 years so I saw no reason to change. I have one 20A 120V circuit for tools and one 15A 120V circuit for lights and my 1hp Delta AP400 DC. I put outlets about 4 feet off the floor. I may also run a few outlets on the 15A circuit. I wanted lights separated from tools, however, because I am much more likely to trip the tool circuit. But once I got it to 20A (two houses ago) I don't remember it ever tripping.

My shop is used by me. My wife doesn't even have a key to the garage door side. I keyed the back door the same as the rest of the house so I guess she could get in that side. There is no entrance from the house to the shop, you have to go outside. I say all this to say I don't run multiple tools at once and there are never multiple people using the shop. So I see no need for multiple tool circuits. Lights are CFLs that only draw about an amp. So I have capacity on that circuit for my small DC.

I thought about running a 12 gauge three wire for a possible future 220V circuit but I was paying an electrician for the rough in and went cheap. Then I had a chance when I was putting new subfloor in the room over but didn't take up all the old and didn't do it. I may regret this if I ever really need 220V in the shop. But if I do, a little drywall patching and I can add it. The main potential would be if I decide to get a welder. Right now I just have my son do it if I need something welded.

[Steve Peterson]

What spacing is recommended between the outlets?

I put outlets on every other stud, so the spacing is 32". It is easy to run 2 circuits so every other outlet is on a different breaker. This allows you to run a tool on one circuit and a shop vac on a different circuit. 50" above the floor is nice and you can usually fish a wire down to a lower box later if you need a floor mounted outlet.

I ran a few 240V circuits where I knew they were needed. You can always run additional circuits as long as you have attic or crawl space access. Things change over time even if you think you have your shop completely figured out. I usually over-plan everything and still end up changing 2 or 3 outlets later.

Steve

[Mike Henderson]

Mike, you can use a multiwire branch circuit with a GFCI in the first box and feed all downstream 120V receptacles from it.

Use a red and a black conductor for the 240V circuit, and a blue and white for the 120V.
Regards, Rod.
Yes, that's true. I thought you would were talking about running the 240 and 120 to every outlet. That is, three wires to every outlet - two hots and a neutral.

Mike

[Andy Fox]

Whether 120 and 240 can be in the same box is a question for your local inspector. They determine what the code is.

You might run into problems with the box fill, either the calculation or the reality of things being too tight to fit safely.

See: http://ecmweb.com/code-basics/box-fill-calculations

[Wade Lippman]

You mean like this?

http://www.kyleswitchplates.com/combo-duplex-outlet-single-1-62-20a-round-receptacle-cover-plate/

That would work, but Lowes sells partials that you put together to make whatever you want.

[Ole Anderson]

One 15 amp circuit for lights, 120v 20 amp outlets spaced 4' to 6' oc at four feet off the floor, number of circuits depends on the number of outlets (per code), a dedicated 240 v 20 amp circuit for my DC, a second 240 v 20 amp circuit for my other tools (only runs at a time) (3 hp TS, 3 hp chop saw 1.5 hp mini mill), 1 hp compressor on its own 120 v 20 amp circuit. I have a wall mounted power strip for my chargers so I can turn them off when I am on vacation and another near my MS where I also plug in my sanders.

I keep my 120 and 240 volt outlets separate, and I don't bother with twist locks, not really needed IMHO unless they are ceiling mounted.

[Ian Scofield]

Yes, that's true. I thought you would were talking about running the 240 and 120 to every outlet. That is, three wires to every outlet - two hots and a neutral.

Mike

I'm sure you were implying this but just so the OP doesn't overlook it, you should be running 4 WIRES to every box.

2 hots + ground for the 240V
1 hot + 1 neutral + ground for the 120V.

Therefore, 2 hots, 1 neutral, 1 ground. DO NOT run your neutral for the 120V on the ground wire. That's not up to code.

[Chris Padilla]

Ian,

The bare/green ground wire is technically not counted but it is assumed. For example, when spec'ing romex cable, it goes as 12/3 + ground although most don't add the + part and simply say, '12/3', which of course implies two hots and a neutral...plus the bare ground.

[Steve Mathews]

Thanks everyone for the very thoughtful and terrific responses. I especially like the idea of having separate circuits or alternate outlets on separate circuits for the dust collector. That never occurred to me. The table saw and planer are the only pieces of equipment requiring 240. One is rated 15A and the other is 30A. If I only have one circuit serving both of these what size circuit breaker should I use? Or should there be separate circuits because of the different load ratings? Also, my dust collector has a 1.75hp motor which is capable of running 240v. It's now wired for 120. What's the advantage of 240? It seems to run fine now.

[Mike Henderson]

Thanks everyone for the very thoughtful and terrific responses. I especially like the idea of having separate circuits or alternate outlets on separate circuits for the dust collector. That never occurred to me. The table saw and planer are the only pieces of equipment requiring 240. One is rated 15A and the other is 30A. If I only have one circuit serving both of these what size circuit breaker should I use? Or should there be separate circuits because of the different load ratings? Also, my dust collector has a 1.75hp motor which is capable of running 240v. It's now wired for 120. What's the advantage of 240? It seems to run fine now.
The circuit breaker is there to protect the wire. If you use 12 gauge wire, the breaker should probably be 20 amps. If 10 gauge, 30 amps.

Mike

[Steve Mathews]

The circuit breaker is there to protect the wire. If you use 12 gauge wire, the breaker should probably be 20 amps. If 10 gauge, 30 amps.

Mike

So it's acceptable to use one 30A circuit for both 15A and 30A machines that don't run at the same time?

[Ole Anderson]

Ideally you would limit your 30 amp circuit to 80% of the breaker value, or 24 amps. Anything less is ok as long as you are not hardwired with a cable less than 10 awg.

[Mike Henderson]

Ideally you would limit your 30 amp circuit to 80% of the breaker value, or 24 amps. Anything less is ok as long as you are not hardwired with a cable less than 10 awg.
Just to add to Ole's comment. Most tools that require a 30 amp circuit only draw 30 amps at full load. So if you had a table saw (for example) that required a 30 amp circuit, it would only draw 30 amps when you were cutting very thick, very hard wood, very fast. Most of the time, the saw would be idling and the current draw would be quite less.

So I think his comment is that you should limit the draw to 80% on average. It's certainly acceptable to peak to close to 30 amps, as long as the average over a reasonable time frame (let's say 10 minutes) is 80%. Most 20 amp machines peak at startup at close to 20 amps, for example.

Beyond that, yes, you can run a 15 amp machine off of a 30 amp circuit.

Mike

[Rick Potter]

I have overkill on my shop electrical, with 39 breakers. One thing I did that I think is important is to hopscotch my plugs. Plugs 1, 3, and 5 are on one circuit, plugs 2, 4, and 6 on another. This applies to both 120 and 240 circuits.

Most of my 240 circuits are 20A, using 20A/240 duplex plugs, which are handy sometimes. I only have two 30A 240 circuits, for the 37" drum sander, and the TS/DC combo. There are 6 outlets for the 30A, also. It is nice to be able to rearrange without having to rewire.

[Ole Anderson]

Just to add to Ole's comment. Most tools that require a 30 amp circuit only draw 30 amps at full load. So if you had a table saw (for example) that required a 30 amp circuit, it would only draw 30 amps when you were cutting very thick, very hard wood, very fast. Most of the time, the saw would be idling and the current draw would be quite less.

So I think his comment is that you should limit the draw to 80% on average. It's certainly acceptable to peak to close to 30 amps, as long as the average over a reasonable time frame (let's say 10 minutes) is 80%. Most 20 amp machines peak at startup at close to 20 amps, for example.

Beyond that, yes, you can run a 15 amp machine off of a 30 amp circuit.

Mike

I agree with the normal draw of a TS being much less than the FLA on the nameplate. I prefer to size the breaker and wire as I stated, however for motors there is a whole section of code on sizing breakers and wire for motors, which I really don't want to figure out, so I play it conservative. The 80% rule is code for resistive loads, IIRC. Motor starting amperage, however, is many times the FLA on the nameplate, but it is so brief that the breaker (and wire) is able to handle it. On my 2 hp dust collector, under load it draws about 10 amps (240 volts), but at startup the digital ammeter reads around 65 amps briefly until the impeller comes up to speed.

[Lee Reep]

I have three 120VAC "tool" circuits in my shop. (All lighting is on separate 120VAC circuit.) Each circuit uses a different color receptacle so it is easy to tell which circuit a particular outlet in on. Another handy practice is to install two circuits at each outlet box location, or at least close. That way you can power a tool on one, and a shop vac on another, and not risk tripping a breaker. This is not an issue when you are using a a 240VAC saw, and a 120VAC shop vac, but still a nice practice. I have a contractor saw that runs on 120VAC, and before I got my dust collection system, I used a shop vac, so I needed two circuits to run both saw and shop vac together.

Also, many states require GFCI circuits in basements. Even if not required, it is a a pretty good idea to do so.

[Tom M King]

Lee, I really like the idea of different color devices for each circuit.

[Lee Reep]

Thanks Tom. When I started my basement shop, I found some orange "hospital grade" outlets on clearance. I thought these would be cool as my outlets for the primary "tool" circuit. A few years later I wanted to add more. Guess what, no clearance pricing this time -- they run about $13-14 each at Home Depot! But I had to have them, so I bit the bullet and bought a couple more. :)

The other circuits are gray and white, so they are cheap and available anywhere ...