Sizing the neutral

[posixPilot]

Hi Everyone,

I know this isn't an electricians fourm, but I wanted to see if anyone else has run into this. I've just finished installing a 50a circuit for my welder, runing from my electrical service to the garage. I'm running 4/4 (since I have to go 100ft) all the way from the breaker to the welder outlet. However, since the garage is a "damp location", code requries a ground fault breaker, which I installed. As you may know, GFI breakers wire the neutral through the body of the breaker so that the device can detect a fault to ground.

Even though the breaker accepts #4 for the 2 hots, it's prewired with #10 stranded for the neutral conductor (which seems smallish). I think this is probably OK for 250V applications since the neutral isn't really used. My understanding is that the neutral wire is actually a return to the center tap of the utility transformer, and is only used for "unbalanced" loads (i.e. 125v circuits).

Has anyone dealt with this before, and can check my thinking here?

Thanks
Mike

[jakeru]

According to "Code Check Electrical, 5th edition" (based on the 2006 IRC and the 2008 NEC), GFCIs are only required for 15A & 20A receptacles on 120V circuits and certain other applications for pools, spas and hydromassage tubs (for example, a 240V pool pump motor does require GFCI protection.)

Therefore a 240V garage circuit does not need GFCI protection.

[Powertig]

I don't think you have to worry about the size of that wire, I believe it is not meant to carry a load, it is a reference to ground so any loss of current to ground can be measured by the GFI( and there by tripped.) I agree with Jakeru, you should not have to use a GFI. one thing I did learn the hard way is that you must mount any garage outlets above 18" from the floor.

[Jake98]

I wouldn't be surprised if the GFI trips a lot. I guess you could wait to find out, but I wouldn't get my hopes up on it working.

[performance]

There is NO Neutral on a welder circuit. It is only 3 wires as ken said. Two hots and a ground. The Nema 6-50 IS the standard for welders, not the 14-50.

If your garage is damp, you should not be using a welder in it!

[posixPilot]

Interesting; I assumed that GFI would be required to any outlet in a damp location, regardless of the size. So, it sounds like it is legal per the NEC, but safe is another matter.

Thanks
Mike

[posixPilot]

Mark,

I'm using the term "damp" in the same sense as the NEC (i.e. outdoors or near water taps) ... of course I'm not standing in a puddle welding . As I mentioned in the OP, I understand that the welder doesn't have a neutral.

Cheers
Mike

[posixPilot]

Thanks Ken. I thought that unbalanced was the normal state for a 125 VAC circuit, since the neutral returns to the center of the utility transformer. I actually have a couple of 125 VAC 20A outlets on a subpanel that connect back through the 50A GFI, so that was one of the reasons for the original question. I haven't yet had any problems with the GFI tripping while running the welder.

Powertig: Thanks for the info as well. I was actually looking for the minimum height a few weekends ago when I was installing the outlet, but I never found the info. I think I ended up putting my outlet at 36", so I'm good .

Cheers
Mike

[Jake98]

Your ground is going to the same place as a neutral, since you aren't using a sub-panel. Welding on a steel table with steel legs would probably trip that GFI. At least that's how I think it works.. those things trip with something like a millionth of a volt.

[posixPilot]

I actually do have a subpanel in this setup, with ground and neutral split in the subpanel and bonded at the main panel. The GFI hasn't tripped yet, but I have also had my HF ground connected, so I wonder if that makes a difference. Hmmm, I'll have to see what happens if I disconnect it.

Cheers
Mike

[posixPilot]

Finally remembered to try this out while I had my welder hooked up today. I disconnected the HF ground, and the GFI did not trip. I also bought one of those little plug in GFI testers, and verified that the GFI tripped properly when I tested the 125V outlets branched from the subpanel.

Cheers
Mike

[Jake98]

Your new avitar is eggceptional Mike!

[posixPilot]

Thanks; I had a bit of extra time while I was traveling last week, so I fired up Gimp and the chicken-weldor was, um ... "hatched" .

Cheers
Mike