Shop electrical outlets?

[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/comb...e-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.