220A welding circuit question

wstf2 · Jul 30, 2011

Today I tore out the four wire wiring as seen in my opening post and replaced it with three wire 6AWG 600 volt black, white and bare copper ground. The run was only around two feet so the expense was minimal.
The old white wire was as suspected just clipped off above the oultet's wall box with no wire nut.
I have sure learned a lot about 230V circuits since I started this thread but by no means will I venture any further into the relm of "electricianism" without consulting the forum as I did here.
Nothing on the horizon but that can always change, thanks all.

Inspector507 · Jul 30, 2011

You were fine before you did all that. And you're good to go now.

Transit · Jul 30, 2011

Always glad to confuse you. Happy welding, enjoy making sparks.

xtn · Jul 31, 2011

Unless I misunderstood, please wrap the ends of you new white wire with red tape. You are using it as a hot leg and you don't want anybody ever thinking that it's a neutral.

Haywire · Jul 31, 2011

Why does the ground bus and the neutral bus have to be separated at the add on panel if they are common at the main panel?

Not disputing anyone, just asking.

Ian

dstig1 · Jul 31, 2011

The ground wire is supposed to NEVER carry current, per code - unless there is a short, in which case its job is to carry the current back to the panel to allow the breaker to trip. The neutral carries the return current on any 120V circuit. Even though the 2 are bonded together in the main panel, the one carries current and the other one does not (except during a short).

If you hook the ground and neutral together in a sub panel, the "neutral" current from a circuit in that subpanel will go back to the subpanel on the neutral but since the ground and neutral were incorrectly tied together in the subpanel, from there it would have 2 paths back to the main panel, and at least some of it would go on the ground wire, thus the ground would be carrying current. Bad hoo-doo.

Make sense?

crazyal · Jul 31, 2011

I think the easiest way (at least for me) is to think of it as the sub panel is a circuit (branch) off of the main panel. As such you cna't think of a sub panel like a main panel.

Haywire · Jul 31, 2011

dstig1 said:
The ground wire is supposed to NEVER carry current, per code - unless there is a short, in which case its job is to carry the current back to the panel to allow the breaker to trip. The neutral carries the return current on any 120V circuit. Even though the 2 are bonded together in the main panel, the one carries current and the other one does not (except during a short).

If you hook the ground and neutral together in a sub panel, the "neutral" current from a circuit in that subpanel will go back to the subpanel on the neutral but since the ground and neutral were incorrectly tied together in the subpanel, from there it would have 2 paths back to the main panel, and at least some of it would go on the ground wire, thus the ground would be carrying current. Bad hoo-doo.

Make sense?

I can't see it making a practical difference since it all goes back to the same ground point anyway.

Ian

wstf2 · Jul 31, 2011

xtn said:
Unless I misunderstood, please wrap the ends of you new white wire with red tape. You are using it as a hot leg and you don't want anybody ever thinking that it's a neutral.

I'm sure getting good at opening up and buttoning up a sub panel!

dstig1 · Jul 31, 2011

Haywire said:
I can't see it making a practical difference since it all goes back to the same ground point anyway.

Ian

Well you've now made your entire ground system in the house hot. You go to replace something and turn off the breaker, but if you short the ground to the neutral you can create a circuit. Or grab the ground, and the current can travel through you. Also, since many folks bond their copper pipes to the ground system, you have just energized all your pipes.

And if a ground connection comes loose or fails, then you do NOT have it all going back to the same place. It is easy for that to happen to a ground and never notice as they are not part of the day-to-day function. If you drop a hot or neutral, the appliance won't work so you will quickly notice, but if you drop a ground, you may only find out the hard way, if ever.

Remember, everything in the code is there for a reason...and the reason is usually it has happened before...

Plus you can create ground loops which can cause other trouble in the system, so I'm told. never looked into that much myself.