Shared air and electric line

[curtis cutter]

How many amps do you think you will need to see at the end of the run?

20 amps max. for just the welder if I'm reading rating plate on the MP210 welder correctly.

How many feet from your source to your load?

[jcfx]

Best guess, 120 ft ?

[curtis cutter]

Below is a calculator. I personally would shoot for a 3% voltage drop or less. For a test, run Copper 10 AWG wire and see the results then try 12 AWG. Although 12 AWG will handle 20 amps, it has a cost for trying to push it through the wire and that is more voltage drop than you may wish.

https://www.calculator.net/voltage-drop ... &x=62&y=16

[John Hasler]

Your bx has to be large enough (i.e., small enough AWG) to be protected by the upstream breaker. It also should be large enough to comply with the NEC recommended 3% maximum voltage drop limit at the rated current of the upstream breaker.

I'd put bushings on the ends of the conduit (you'll want these to protect your air line anyway) and treat it as a really small tunnel.

BTW is there any chance of the conduit filling with water? If so don't use unjacketed bx.

[jcfx]

Curtis, John, Thanks for the advice, that calculator is handy,
I don't think there's any chance that the conduit will fill with water.