Using 12-2/10-2 when wiring for machines?

[Caleb Dietrich]

Hello and Happy Thanksgiving.

I will be spending the weekend setting up my first personal shop in the basement of the house my wife and I bought in June.

**Can I run 220 w/ 12-2 for 20/20 amp breakers and 10-2 for 30/30 breakers?

I am running the wires and an electrician will be connecting them to the panel.

I have lengths of both I would prefer to use, and I have seen it done. I'm wondering what the drawbacks are to eliminating the neutral wire, as you must have to with 2 wire...

[Art Mann]

The wire sizes you are planning to use are standard for the current you intend to have them carry. The only reason you might want to up-size the 20A circuits to 10AWG is if you might want to upgrade from 20A to 30A with a different breaker at some future date. Sounds to me like you already know your 30A requirements and have figured them in. I don't know of any reason to run a neutral wire. I have several 240V circuits in my shop and have never wished I had run the third conductor. Woodworking equipment requiring a neutral wire is pretty rare.

[Don Abele]

Caleb, 220 lines do not use a neutral or common line. There are two hot legs (each with 110 volts). I have seen 220 installations where they mark the white line with a red tag to indicate it's a hot leg, not a neutral.

As for wire size, this is the information I have saved to my computer. Each is for a run of 100 feet or less. If you go over 100 feet it decreases the capacity by 5 amps, 200 feet decreases it by 15 amps (not 10).

3g = 100 amps
6g = 50 amps
8g = 30 amps
10g = 25 amps
12g = 20 amps
14g = 15 amps
16g = 13 amps
18g = 10 amps

Sorry but I don't have the exact reference for it - it's a chart I copied while doing research for a wiring job several years ago. I've stuck with that and have never had a problem with electrical inspectors.

I guess the best advice though would be to ask the electrician who will be making the final connection. He may have a personal preference regardless of what anyone posts here.

Be well,

Doc

[Caleb Dietrich]

Thanks guys. That solves it for me.

Caleb

[glenn bradley]

I'm with Art. I ran 10ga on my 20a 220v circuits. If I want to add a higher demand machine, I only have to change breakers and outlets.

[Jim Becker]

"Typically" we use 12/2 for 20 amp circuits and 10/2 for 30 amp circuits. I say "typically" because there are some times when there are circumstances that affect "the math"...such as distance, etc. Many folks will pull 10/2 in anticipation of future changes to the machinery without having to attack the wall again.

[Wade Lippman]

Odds are you don't need the neutral, but you never know. Typically the worst part is the labor rather than the material. It is much easier to overdo it the first time so you don't have to redo it.
I put a cable from my garage, where I run my generator, to a transfer box next to my panel. I ran 10/3 even though my 2kw would have been happy on 12/2; cause it was a lot of work and I didn't want to have to do it all over if I got a 7kw generator. (don't have to worry about voltage drop!)

I am not recommending 12/3, but just pointing out that there is more to it than the needs of a particular machine.

[Matt Meiser]

I agree with all the above posters but add one thought. On the feed to my TS, I used 12/3 because I have a small dedicated shop vac serving my overarm blade guard. I have it wired on a spare set of contacts in the magnetic starter so that it turns on and off with the saw. Since the saw is 220 and the vac is 110, I needed the neutral since you aren't allowed to use the ground for that purpose, even though if you measured between the line and the ground you would see 110.

[Tom Veatch]

...you aren't allowed to use the ground for that purpose, even though if you measured between the line and the ground you would see 110.

Ground and neutral are at the same potential since they are bonded at the main panel. The general rule is that the wire used for grounding equipment isn't permitted to carry current during normal operation although I believe there are some rare and specific exceptions.

[Matt Lentzner]

Is that code? I thought every 220 line had to be dedicated to a single device.

[Matt Meiser]

Matt, if you are referring to what I did, I'm not sure. However everything is wired from the starter on the saw, which has a cord that plugs into the receptacle so if someone wanted to get technical, its all one device as far as the building wiring is concerned. I don't know if that would fly from a legal point of view, but I guess I'm not worried about it. Maybe I should have.

I do have two different outlets off that drop--one a 4-wire for the saw and one a standard 20A for my plasma cutter. According to previous discussions that is allowed by NEC.

[Don Abele]

Matt, the question of multiple outlets on a 220 line has come up here several times. All the replys indicate there is no code against it. In fact, that's the way the electrician that verified my install for the permit recommended I do it.

As for pulling 110 off of a 220 line you must run a 3 conductor line as pointed out - you can not use the ground as a neutral. Also, the wiring for the 110 MUST be capable of carrying the entire amperage of the breaker - because it has the potential to pull that much. So if you wire a 220/30amp using 10/3 wire, you must use 10g wire to the 110 outlet. It should also be noted that anything plugged into that outlet is not going to have much overload protection because it has 30 amps before it trips.

Be well,

Doc

[Rick Christopherson]

As for wire size, this is the information I have saved to my computer. Each is for a run of 100 feet or less. If you go over 100 feet it decreases the capacity by 5 amps, 200 feet decreases it by 15 amps (not 10).

3g = 100 amps
6g = 50 amps
8g = 30 amps
10g = 25 amps
12g = 20 amps
14g = 15 amps
16g = 13 amps
18g = 10 amps
This information is incorrect.
http://www.waterfront-woods.com/Articles/Electricity/wiresize.gif

[Tom Veatch]

Is that code? I thought every 220 line had to be dedicated to a single device.

Code doesn't require that every 220 outlet be on a separate circuit or, IOW, it isn't necessary that each 220 circuit have one and only one outlet.

The branch circuits in my shop are wired with 3+ground (2 hots+neutral+ground) and have several dual voltage receptacles on each circuit. So at each wall plug location, I have both 110 and 220 available.

It was wired by a licensed electrician and signed off by the inspector.

[Tom Veatch]

... Also, the wiring for the 110 MUST be capable of carrying the entire amperage of the breaker - because it has the potential to pull that much. So if you wire a 220/30amp using 10/3 wire, you must use 10g wire to the 110 outlet. ..l

You should also note that the 110 receptacle must also be rated (or keyed) for 30 amps - NEMA 5-30. You can't use the "standard" NEMA 5-15 receptacles in that application.

[Dave MacArthur]

Check my signature below for a good article on wiring a home shop with various NEC references.