220A welding circuit question

[wstf2]

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]

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

 

[Transit]

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

 

[xtn]

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]

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]

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]

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]

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]

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]

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.

 

[Haywire]

I'll just have to take your word for it. Seems to me like the ground is already shorted to the neutral at the main breaker panel.

 

[dstig1]

Yes, but if you assume perfection in installation and no future problems, then why add a ground wire at all? It doesn't do anything 99.99999% of the time....

 

[crazyal]

Like I said, think of it like a circuit. You wouldn't connect the ground wire to the neutral wire on a simple duplex receptacle. The ground and neutral certainly aren't grounded inside the outlet. If you are wiring up a light fixture, you connect the ground wire to the ground screw or ground wire and not the neutral.

Yes it shouldn't make a difference. But remember the neutral wire's job is to provide a point between the two hot legs coming in from the pole.

My father had a problem with his house (built in 67). The main panel wasn't grounded, it just relied on the neutral coming in from the pole. Over the years he built a garage and added a sub panel (mid 70s). Dad knew plenty about electricity but not so much about codes. He did add a simple clamp on the water line coming in from the street for a ground.

Inside the meter box the connection for the neutral wires rusted, who pulls their meter to look inside it? So not knowing he had a problem he did nothing. The builder didn't do a good job balancing the load. So that one clamp he put on in the garage was now the only thing trying to keep the neutral from floating. Since he didn't use the correct equipment it started to fail. All of a sudden things with capacitors rated for voltages below 200 started blowing up. When he started to explore what was happening (later that day) he disconnected that one ground wire and the fridge turned on he got a nice shock and then blew out about a dozen electrical devices throught the house.

Yes it took several things to happen before a bare wire in his garage had live power on it. But because it does happen the code has been updated to include two ground rods for main panels, the gauge of ground wire needed, and that a sub panel's ground is no longer to be tied into the neutral.

My biggest problem with codes is that they should make a version of them easy to understand (at least for residential houses) since I can do work to my house's electrical system. A simple on-line system for homeowners with the logic behind it would go a long way.

Most people have no idea why the main feed coming into the house has two hot wires that are a larger gauge than the one single neutral wire. When i ask people most just say that the rest of the power goes through the ground rod.

 

[Haywire]

Well... my barn isn't to code then. The panel in it is a 100a panel designed to be a main with the neutral and ground bars bussed together (I replaced the 100a main breaker with a 60a). One bar has the neutral feed from the main panel in the house and the other bar has a solid wire to the ground rod at the barn. The grounds and neutrals are not segregated.

oh well,
Ian

 

[Transit]

Crazyal, check out Code Check, a series of flip books about all common building codes with diagrams.

 

[dstig1]

Well... my barn isn't to code then. The panel in it is a 100a panel designed to be a main with the neutral and ground bars bussed together (I replaced the 100a main breaker with a 60a). One bar has the neutral feed from the main panel in the house and the other bar has a solid wire to the ground rod at the barn. The grounds and neutrals are not segregated.

oh well,
Ian

Ahhhhhh! You were looking for an excuse, Ian! It isn't hard to separate them. Most panels have a single screw or strap that you remove to separate the neutral from the ground. If you needed to cobble something, you could simply take a piece of plastic larger than the neutral buss, remove the buss and screw the plastic in place as an insulator. Then screw the neutral buss to the plastic, avoiding metal contact.

Al - if they wanted the NEC to make sense they would have never used the terms "grounding conductor" and "Grounded conductor" to mean two different things...for one example.

 

[xtn]

I'll just have to take your word for it. Seems to me like the ground is already shorted to the neutral at the main breaker panel.

Yes it is, but at that point any current can flow a short distance to the rods in the earth. It isn't going to energized all your enclosures, boxes, water pipes, etc. If they are connected anywhere downstream then everything in the system that's grounded could see current on a regular basis. Don't want to plug in your good old metal cased drill motor and get a shock from holding it.

Functionally everything will work, as the electrons don't care which way they get back to the source. But for safety, keep them properly separated.

 

[Haywire]

So since the sub panel in question is also ground rodded, it's a non-issue. LOL

 

[xtn]

So since the sub panel in question is also ground rodded, it's a non-issue. LOL

Probably right, but that doesn't mean it is code compliant.

 

[Transit]

Haywire, if you have a main panel and a sub panel connected with a ground lead and both panels have ground rods, you have built yourself a battery. the circulating current over time will rot out many things in the system, to say nothing of your TV, PC, sound system going nuts.