Wiring Question - Switching Wire Gauges

[Marcus Waddell]

Hi all,
Been a while but I love this forum! I always get great advise here! I'm a fairly advanced DIYer and am putting in a subpanel in my basement for my basement woodshop and have a question about using EMT and wire gauges. I plan to run at least three circuits. Two 20A 120V circuits and (at least) one 30A 240V circuit. I'll be using EMT conduit (probably 3/4") and THHN wire. For the 120V/20A circuits 12 awg is needed, and 10 awg is needed for the other circuit. Could I simply run all three circuits with 10 awg? If so, do I need to do anything special when connecting the 120V/20A receptacles? Is it possible to switch from 10 awg stranded to 12 awg solid while wiring up the pigtails for the 120V/20A receptacles?

Thanks for your assistance, I look forward to the advise!

 

[hj]

As long as the circuit breaker is adequate for the wire size, you can use any wire size you want to.

 

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[ImOld]

I see you realize attempting to put #10 wire on standard receptacles would be unwise. I would never do what you describe and wonder why you are making a simple install more involved. Since this is a sub-panel, also make sure the ground and neutral are
separated in the panel. I'll assume this is not going to be inspected so no comments on emt installation. Here is a link to the NEC codes if you're interested. You have to know what code year your jurisdiction is under. It varies drastically across the country.

https://www.nfpa.org/codes-and-stan...des-and-standards/detail?code=70&tab=research

 

[Reach4]

Is it possible to switch from 10 awg stranded to 12 awg solid while wiring up the pigtails for the 120V/20A receptacles?

From what I can see, it would be permissible to run the 10 AWG to a big wire nut that also contains the two 12 AWG solid wires going to the left and right duplex receptacles. You wouldn't put just single duplex receptacles in a 2 inch boxes for a workshop, would you? But yes that would be permitted. At least consider using 4 inch boxes even for a single duplex receptacle for room and easy potential future expansion.

I am not an electrician.

 

[Marcus Waddell]

Definitely 2 gang boxes with two outlets in each. It probably will be inspected…what’s the issue with emt? Not trying to make it more complicated but I would imagine 10awg stranded is easier to pull than 12awg solid. Plus I’d only have to buy one bundle of wire.

 

[Reach4]

Definitely 2 gang boxes with two outlets in each. It probably will be inspected…what’s the issue with emt? Not trying to make it more complicated but I would imagine 10awg stranded is easier to pull than 12awg solid. Plus I’d only have to buy one bundle of wire.

No issue with EMT... saves you from running a ground, and protects wire really well. However I am not confident that 10awg stranded is easier to pull than 12awg solid. Are you going to have a long pull without pull boxes or pull elbows?

You are going to buy some white for the 120 volt outlet neutral, right?

3/4 EMT is harder to bend than 1/2, but easier to pull thru.

I expect you will be pulling 4 conductors total, so nice and roomy. Some 240 circuits also have a neutral, but I think you don't intend to use one of those outlets.

 

[Marcus Waddell]

Running two 120V/20A circuits and one 240V/30A Circuit (so 8 wires). Should only be two 90s from box to first outlet, then I can pull across to the other outlets. Would PVC conduit it better? I already have the cement and other items from when I ran a subpanel to my outdoor shed earlier this year.

 

[Reach4]

Running two 120V/20A circuits and one 240V/30A Circuit (so 8 wires).

If the two circuits were MWBC (Multi-Wire Branched Circuit), they could share a neutral. But separate neutrals is probably the better choice overall. So that's 4 wires. Then the 240 is 2 wires, totaling 6. The EMT and metal boxes form the ground path.

You can get wire by the foot some places. Then you could have the easier-to-work-with 12 AWG, and have different colors.

 

[Marcus Waddell]

Definitely not going to allow the EMT to serve as ground. I'll be running a separate ground wire.

 

[Marcus Waddell]

Silly question: I was thinking pull the wire to the first outlet and then just continue on from that outlet box to the next, but that means there will be conduit in the middle of my wall. Is it better to run separate pieces from the ceiling down to each outlet? I.E. An upside down "T" vs a sideways "E"?

 

[WorthFlorida]

You are not gaining anything using 10 awg wire for the two 120v circuits. Keep them at 12 awg. 12 gauge stranded is good with lots of turns but I find solid copper is much easier to terminate on wall switches and outlets. Do use 10 gauge stranded wire.

PVC conduit is cheap and very easy to work but there are guys that can bend EMT like a machine did it. It’s really up to you.

 

[Jadnashua]

10g wire is a good price increase versus 12g, so unless you have excess money to spend or the run is short, I'd use 12g where it's possible. I prefer to crimp on a connector when connecting to the receptacles with stranded wire versus trying to wrap it around the screw. If you're using one with clamps, verify that they allow stranded.

You'd want to verify the fill for the emt size. I don't remember the specs.

In a shop, you might want to have two circuits...that would only require one more wire for your 120vac receptacles if you shared the neutral. Using GFCI could complicate things if you did that, though.

 

[Marcus Waddell]

All...sorry, I'm a goober. I was thinking because it's 240V I'd need larger wire. I don't. All of the circuits will be 20a, so 12 awg wire will be fine.

 

[Norcal01]

Make sure to bond the grounding conductor to the boxes where you have boxes with splices & devices, this is very important.