Shop wiring help please...

[Jim Dawson]

I'm adding a 240v 30a outlet and multiple 120v 20a outlets in the garage. I'm going to surface mount EMT. What is the minimum number of wires I need and do I need to pull a separate bare ground wire or can I use the conduit as ground? If yes on the ground wire, can everything share the same ground wire and what size do I need? I'm going to use 10AWG THHN for both 120 and 240 so I don't have to buy two size wires.

Thanks,
Jim

 

[matt_i]

My two cents. Since you have done all the hard work of building an EMT system, put in a real copper grounding conductor, bond the metal boxes and the outlets to the copper wire.

I would buy by the foot: #10 awg black, #10 awg red.

Then: a spool of #12 black, a spool of #12 white and a spool of #12 green (whatever "spool size" is appropriate for the job plus some more) If you've done your own work up to this point, I feel certain someday you will want to expand the 120vac circuitry to accommodate something new. Copper is going to go up in price, slowly, forevermore, and you just locked in the price.

 

[Jim Dawson]

Thanks Matt, sounds like a good plan.

 

[sberry]

I agree with Matt. Buy the 10 you need for the single circuit by the foot and as much 10 ground as you need for it and b8uy the spools in 12 for the rest of it. You will have it for additions. Buy 500ft spools. Its a bit up front as he said but most economical.

 

[bigb56]

If you are choose to run a grounding conductor (and you should) it must be sized for the largest circuit which in your case would be #10. Just because you are not required to run a grounding conductor does not mean you can run an undersized one if you choose to run one. Once you reach the end of the 30 amp circuits you can drop it down to #12 from that point on.

 

[wyliesdiesels]

My two cents. Since you have done all the hard work of building an EMT system, put in a real copper grounding conductor, bond the metal boxes and the outlets to the copper wire.

I would buy by the foot: #10 awg black, #10 awg red

Then: a spool of #12 black, a spool of #12 white and a spool of #12 green (whatever "spool size" is appropriate for the job plus some more) If you've done your own work up to this point, I feel certain someday you will want to expand the 120vac circuitry to accommodate something new. Copper is going to go up in price, slowly, forevermore, and you just locked in the price.

OP will need green #10 for the 30a circuit.

 

[Jim Dawson]

OP will need green #10 for the 30a circuit.

But do I need two ground wires or can both circuits share the #10 wire?

 

[sberry]

It can share the 10.

 

[wyliesdiesels]

But do I need two ground wires or can both circuits share the #10 wire?

Bob answered that in #5.

You can share the EGC among different circuits but it needs to be sized for the largest circuit.