Neutral and Ground Separation

[Kidd6488]

Hello everyone. Sorry this is kinda long, I have a lot to say :-). We are finishing up an addition we had put on to our house. This house was built in late 60's- early 70's, and had a wadsworth breaker box (complete with space-hogging cartridge main fuses). Outside was the meter, being fed with 3 wires from the pole, which I see has the neutral connected to the ground rod below.

The location of our addition required that our meter be moved, and therefore the mains coming from the meter to the main panel be moved as well. Our contractor hired a company to do this, and I observed . Outside, they installed a new meter base, and a 200A disconnect switch. They are wired as follows:

Hots and neutral run from meter base to disconnect switch, through metal hub (which bonds them together, correct?). In disconnect box, the hots connect to the switch and proceed on. The neutral connects to an insulated lug, and proceeds on. There is a separate ground lug, which connects to the case of the disconnect box, the copper wire going to the ground rod, and a separate ground wire going into the house. So the wire going to our main panel is 4/0 - 4/0 - 4/0 - 2/0.

He (The electrician hired to do this work) connected the mains to our main panel, and connected the neutral and bare ground wires to the only ground/neutral buss in our main panel box.

Because of the size of our addition, we had to install a 100A sub-panel. The same electrian ran the wire to that. Now I know that subpanels must be 4-wire, yet they ran 2-2-4 SEU I believe it is, with two insulated wires and a twisted grounding wire.

Not long after that, we (my dad and I) replaced our wadsworth box with a new GE box. We were told by someone from Lowes, that the new 4-wire services are starting to gain popularity; and since they have the neutral and ground completely separated, we need to keep them separate throughout the rest of our electrical system.

So we wired our new GE box as follows: The hots to the mains (obviously). The GE boxes have a neutral/ground bar on each side, with a jumper bar connecting them together at the bottom. The instructions to this panel were pretty confusing. So we removed that jumper bar, and connected the neutral to one bar (the one with the larger lug) and the ground to the other bar. We put the green bonding screw through the, now, ground bar, into the case.

We then re-wired almost our entire house, and ran all the grounds to the ground bar, and the neutrals to the other. We also re-wired the sub-panel feed, using 4-wire 2-2-2-4.

Now my questions. (I know, finally [B)])

• Is this installation correct?
• Does the line comming from the outside disconnect box to the main panel need to be 4-wire? (even though we're not about to change it now)
• Should our neutrals and grounds be separated like they are, (in both the main and sub-panels)
• Should we re-install that jumper bar between the main and neutral busses
• Did that electrician really screw up by running 3-wire originally to the sub-panel?

Now, I know the neutral is grounded out on the transformer, but, as I see it, on our property, our neutral and ground are completely separate. I can, however measure about one ohm between the neutral and ground in the outlets I have checked.

Also, we're putting another sub-panel out in our barn ~150' away from the panel. This needs separate neutral and ground, correct? We've already run 2-2-2 underground to it. 2 hots, and neutral. The ground is created out there with a ground rod, correct? Or do we need a 4th wire for ground out there too? If so, what guage would it need to be?

Thank you for reading all this, and I hope to hear some replies.

And if you would, explain all the reasoning behind the need for separation and such.

Thanks again,
Jonathon Reinhart

~Jonathon Reinhart

[kactuskid]

The neutral and ground must always be bonded together in a main electrical panel. They must always be separte in a sub panel. The wires going from a main panel to a sub panel must always be 4 wire if using to power 15 and 20 amp 120volt circuits. Also, an unattached building will always require not only a ground rod but a ground wire ran also.

You need to hire a different electrician, one that is licensed to come out and check out your entire system. It sounds very unsafe the way it is currently, spend the $$$ and get it done safely and properly. Here's a few links that should explain tons of details to you. Read them all, then still call an electrician.

http://homerepairforum.com/forum/topic.asp?TOPIC_ID=1889

http://www.homewiringandmore.com/homewiringusa/2002/maindwelling/meter/meter.html

[HayZee518]

I agree with kactuskid. The guy that wired the sub panels didn't do it right. sub panels are four wire!!!!! I got nailed by an inspector in Massachusetts after I ran a three wire 150 feet overhead to a sub - I had to remove it and put in a four wire overhead.

[Kidd6488]

Ok, so since we have an outside disconnect, should they be bonded together out there, or should they be bonded together in our breaker box?

~Jonathon Reinhart

[HayZee518]

Always bond the grounds at the MAIN panel. Anything distribution center outside of the main is a sub panel, even if its a few feet away. A single phase disconnect with a neutral bar is considered a sub-panel UNLESS it is feeding a dedicated circuit of ONLY 220 without a neutral.

[Kidd6488]

No, I'm talking about the MAIN disconnect, directly after the meter base. It's outside, right under the meter, connected by a metal hub. Its got a 200A breaker/disconnect, a nuetral lug, and a ground lug.

~Jonathon Reinhart

[Kidd6488]

Here's the way it is (quick lashup)



The two busses were initially connnected with the [dashed yellow] jumper bar. We removed that, made the right one neutral, and the left one ground. We put in the green bonding screw through the left bar, to connect the actual breaker box to ground.

What needs to be done?

~Jonathon Reinhart

[HayZee518]

OK gotcha now - Put that jumper bar back. Add an additional equipt grounding bus with screws for your bare grounds.

[Kidd6488]

Why would we need an additional grounding bus? We've already got the whole box wired as I showed up there (Branch circuits too). The neutral is completely isolated from ground. The ground bus is already bonded to the box. If I put the jumper back, our neutral and ground will bonded together again in the main box. Is that the way it should be? Why did they run 4-wire from the disconnect to the main panel? The ground and neutral are essentially the same thing? I'm quite confused now. I thought our situation was special here, because they had a completely separate ground and neutral system. Also, what exactly is the point of having the two hooked together?

~Jonathon Reinhart

[Rewired]

Kidd6488:

The ground and neutral have to be bonded together at one point and one point ONLY. "Ground" is considered to be at zero volts all the time. Bonding your ground to neutral will ensure that your service is essentially "grounded". If you didn't have that it IS possible to have wierd "voltages to ground". With what you have drawn, if that were here in Canada, you would have to put the "bonding screw" out at the main disconnect, and remove the bonding screw in the main panel.. That is here though, check your local code on where the bonding screw should be. Oh ya, you should never have 2 bonding screws such as one in the main panel and one at the disc. switch, that can cause 'ground loops" and ground currents that should not flow. That is another reason why the ground and neutral are also kept separate. "Ground" is well, zero volts and under normal conditions carries ZERO CURRENT (only under a fault condition will a ground or bonding path carry current).. "Neutral" carries unbalanced current but SHOULD be at "zero volts to ground", so BONDING them together will ensure the neutral stays at "zero" even though it is carrying unbalanced current..

A.D

[Kidd6488]

Thanks rewired, and everyone else, but rewired, you gave some nice details, and told me what I half-expected to hear, about bonding at the disconnect, because technically, isn't that where the 'service' ends? I thought the term 'service' applies to everything up to the first disconnect (which would be outside in my case). Also, this would explain why they ran 4-wire in from the disconnect in the first place.

So if I bond the neutral to ground outside in the disconnect box, i should leave the bonding screw in, in the main breaker box (its only bonding the case to gnd, not neutral to gnd), right?

Thanks a lot,

~Jonathon Reinhart

[Rewired]

Hey!

Glad i could help you out with the details!
First: About the bonding screw issue in your MAIN panel.
What should be done there is the "jumper bar" you Removed should be re-installed.. those bars on each side of the panel are neutral buss bars. You should add a grounding buss in your panel for ALL the grounding wires alone. It will be safer this way because the way it sounds you have it now, if the bonding screw were to get removed somehow, you would lose the bond between your panel enclosure and the now "ground" bar.. The potential for the enclosure to become live if there was a fault inside the panel is very likely the way you have it bonded together now, relying on the "bond screw" to bond the the enclosure to ground.
Second: Bonding neutral to ground at the main disconnect will be correct now. it will be "grounding" the service as it enters your house... (keeping neutral at "zero volts").

Now, Johnathon, look at how I described it there.. Now, picture what would happen if that "bond" between neutral and ground in your main disconnect was to be removed or somehow "disappear". Your "service" would become ungrounded, BUT all the grounds and metal enclosures would STILL be bonded together via the grounding / bonding wires and in turn bonded to the ground rod would they not? That means the every piece of "grounded" metal would still essentially remain at "zero volts" there would be no risk of something becoming live should something fault out, the WORST that will happen is you could show a wierd "voltage to ground" from your service wiring.. thats about it..

I hope I didn't confuse ya, let me know if I did I will sort it out for you!
A.D

[Kidd6488]

Ok, about the neutral/ground bars... This box is already wired, and very wired it is. It would be nearly impossible to change the grounds to a different bar, as they would be too short. The box may be set up correctly as the manufacturer intended, but the instructions aren't clear enough. Personally, I wouldn't worry about the bond screw coming loose, and we can even put some loctite on it to be safer. And say it does come out, and there is a line-to-case fault in the box, there is all kinds of contact from the bare grounds to the case, just by the freak chance that both conditions become true.

As for your second paragraph, I understand what you are saying. But I was reading elsewhere, and correct me if I am wrong, but aren't the electrons coming from the transformer seeking to get back to the transformer, not back to the earth? They might go to earth, but only because the center-tap of the transformer is grounded out at the pole (to its own ground rod).

So, if in some metal outlet box, for example, say a hot wire comes loose and touches the metal box. Now, lets say that the main system bonding jumper (I think it is called) is not there, and neutral and ground are separate. All metal boxes are now at 120V. For the electrons to return to neutral, which they are seeking to do, they must go through the grounding conductors, into the grounding electrode, through the earth 150' to the other ground rod out at the transformer, up the grounding wire, and up to the neutral conductor (center tap). By now, we probably have many ohms in the path, only allowing several amps to flow, and the circuit breaker sees only say 5A flowing through it, which it sees as fine. So the metal boxes remain at 120V touch voltage, waiting for someone to touch it and fry.

Now, I argued this to my dad, and he says that no, the electric is going to go to the ground rod, because everything wants to... But I said, If you take a 9V battery, and put a voltmeter from one terminal to a ground rod what will you get?

So am I correct?

Thanks again for everything...

~Jonathon Reinhart

[HayZee518]

Let me explain this to you from experience. I went on a service call to a house where the guy replaced a Sears broiler/oven. He made the splices in the box exactly the way he took them out. But when he turned on the breaker the oven did not function. I measured 220 on both hots and 110 on each leg to the bare ground wire. I went tracing out the wire in the basement and found another splice box above a dropped ceiling. I opened the box and pulled the wires out. Then I grabbed the bare wire and the dropped ceiling grid and BOY DID I GET A RAP!!! I checked with the meter and had 110 volts to the grid system. I should NOT read anything to this. It should be zero. Went to the main panel and took off the cover. The bare ground was just floating in the box - No connection to the neutral block. It may had touched something at one point or another so the original oven worked. I put the wire in the neutral block and tightened it and voila! The oven worked perfectly.

[Kidd6488]

I don't understand what was going on... It was 3-wire to the oven, I presume, and the oven needed the neutral for the 110 components, but how did you measure 110 to the ground? And I'm guessing you were being the link between the oven's nuetral and the ground, and so you had a hot nuetral, and thats why it hurt so bad... But how did you get 110 when you measured?

And does that prove me or my dad correct, or neither?

~Jonathon Reinhart