Extending a circuit -- what wire do I need?

[klieber]

I'll start off by saying I know very little about electrical wiring.

With that, I have two 30A/240V single phase circuits in my shop that I use for welding and plasma cutting. I want to extend both of these circuits to a different part of the shop. The run is ~60-75ft in total length. Because of the layout, there's going to be a lot of time and labor involved in running the actual wire -- that's stuff I can do myself and then pay an electrician to actually hook the new wires to the existing circuit. I'm not cutting drywall for this, so I'm planning to run wire in EMT conduit and then mount the EMT to the drywall. Thus, I'm NOT planning to use romex.

My questions:

• From Googling, i think I need 4 wires per circuit - 2 power leads (red and black), 1 neutral (white) and a bare ground. Correct?
• I'm planning to use 8ga wire for the power/neutral and 10ga for the bare ground. Is this appropriate or overkill?
• Can I run two sets of wires in a single EMT conduit? (not sure if there's crosstalk or interference to worry about)

Any other tips or pointers that might be relevant are appreciated as well. Thanks!

 

[zmaxmotorsports]

What size/how many wires are feeding the circuits currently?
Picture of existing boxes?

 

[Norcal]

240 volt welders and plasma cutters do not require a neutral.

 

[LS6 Tommy]

Just FYI, code requires the conduit be run first, then the wires pulled. It doesn't allow assembling conduits with the wires already in them or pulling them as you assemble.

Tommy

 

[klieber]

240 volt welders and plasma cutters do not require a neutral.

Thanks -- what wires do they require? Just red/black/ground?

 

[Jason280]

Yes, just red/black/ground wires. You usually see the 4th white wire (neutral) in residential settings, for stoves, some dryers, etc.

Just to be curious, how big is the welder and plasma machine?

 

[sberry]

Depending on the machines 10 may be fine.

 

[Cmreschke]

Just FYI, code requires the conduit be run first, then the wires pulled. It doesn't allow assembling conduits with the wires already in them or pulling them as you assemble.

Tommy

Reference?

 

[FordTruckWench]

With that, I have two 30A/240V single phase circuits in my shop that I use for welding and plasma cutting.

What sort of receptacle do you have now? A three pin (hot/hot/ground)? A four pin "new" dryer hookup (hot/hot/neutral/ground). A three pin "old" dryer (hot/hot/neutral). Or a 50A receptacle? Or maybe some twist lock receptacle?

Do you want to extend from those receptacles? Do you want to keep the old receptacles live? Or do you want new home runs back to the breaker panel?

Do you have surface access to all the relevant parts? Or will you have to connect to existing in-wall wiring?

Because of the layout, there's going to be a lot of time and labor involved in running the actual wire -- that's stuff I can do myself and then pay an electrician to actually hook the new wires to the existing circuit. ... so I'm planning to run wire in EMT conduit ...

Sounds like you might want to install the EMT, and let the electrician pull the wires.

Here's an online calculator to determine what size EMT you need:

http://www.electrician2.com/calculators/rf_calculator.html

Limit the number of bends in your conduit runs to no more than 360 degrees - i.e. four 90 degree corners. And in reality, less is better. If needed, add junction boxes or conduit bodies.

 

[klieber]

Just to be curious, how big is the welder and plasma machine?

The welder is a Millermatic 211 and the cutter is actually one from the Chinese Cut50F group buy.

 

[klieber]

What sort of receptacle do you have now?

Do you want to extend from those receptacles? Do you want to keep the old receptacles live? Or do you want new home runs back to the breaker panel?

Do you have surface access to all the relevant parts? Or will you have to connect to existing in-wall wiring?

They're both standard NEMA 6-50 connectors. Here's a picture.

Ideally, I'd like to extend from those receptacles and keep the old ones live. That way, I can use the welder/cutter in either location. There's surface access to all the relevant parts, though I'll obviously need new, surface mount receptacles in place of the in-wall single-gang boxes there currently.

I may go with your recommendation and run the conduit with a pull string and then let the electrician handle the rest. 80% of the labor is in the conduit work, so that would still save me a bunch of money.

Thanks for the other links/pointers.

 

[pattenp]

Quote:
Originally Posted by LS6 Tommy View Post
Just FYI, code requires the conduit be run first, then the wires pulled. It doesn't allow assembling conduits with the wires already in them or pulling them as you assemble.

Tommy

Reference?

NEC 300.18 A

 

[LS6 Tommy]

Reference?

Quote:
Originally Posted by LS6 Tommy View Post
Just FYI, code requires the conduit be run first, then the wires pulled. It doesn't allow assembling conduits with the wires already in them or pulling them as you assemble.

Tommy



NEC 300.18 A

Thanks, pattenp. I would not have known the reg.

Tommy

 

[theoldwizard1]

... I'm not cutting drywall for this, so I'm planning to run wire in EMT conduit and then mount the EMT to the drywall. Thus, I'm NOT planning to use romex.

FYI, you CAN use Romex in conduit as long as the conduit is properly sized. Single strand is likely cheaper,

Can I run two sets of wires in a single EMT conduit? (not sure if there's crosstalk or interference to worry about)!

You CAN run multiple circuit in conduit as long as the conduit is properly sized.

 

[klieber]

Just FYI, code requires the conduit be run first, then the wires pulled. It doesn't allow assembling conduits with the wires already in them or pulling them as you assemble.

I had read this elsewhere and am curious as to the reason behind it. I confess that's exactly what I was planning to do. (and, frankly, still may do since I doubt anyone will ever know exactly how the wire came to be in the conduit)

I'm guessing the reasons have to do with not crimping/chafing the sheathing on the wire as you connect the EMT. If that's the case, I feel pretty comfortable taking that risk in assembling everything.

 

[Cmreschke]

Thanks, I learned something new today. Never done it and wouldn't recommend it, but didn't know it was a violation. I would have been wrong.

NEC 300.18 A[/QUOTE]

 

[theoldwizard1]

Thanks, I learned something new today.

Does conduit need to be inspected first ?

MC is an exception ?

 

[zmaxmotorsports]

Does conduit need to be inspected first ?

MC is an exception ?

Ive never had exposed conduit inspected before pulling wire through it,I just leave the devices off with the wiring made up for a rough in inspection.
On concealed work I do pretty much the same and get a rough in before the sheetrock is hung.

 

[wyliesdiesels]

Something else to keep in mind is some local jurisdictions do not allow multiple 240v outlets on the same circuit. I would check with your AHJ first....

Also, when multiple wires are ran in the same conduit, derating of the wire ampacity is required.

EGCs/grounds are insulated when ran in conduit...The EMT can be used as the EGC if perferred though many do not like going that route...

 

[zmaxmotorsports]

Something else to keep in mind is some local jurisdictions do not allow multiple 240v outlets on the same circuit.

Also, when multiple wires are ran in the same conduit, derating of the wire ampacity is required.

EGCs/grounds are insulated when ran in conduit...The EMT can be used as the EGC if perferred though many do not like going that route...