DIY Chatroom Home Improvement Forum

DIY Chatroom Home Improvement Forum (http://www.diychatroom.com/)
-   Electrical (http://www.diychatroom.com/f18/)
-   -   breaker panel question (http://www.diychatroom.com/f18/breaker-panel-question-10590/)

chadvavra 08-09-2007 04:17 PM

breaker panel question
 
i replaced a bad breaker today, no big deal but when I put the cover back on the panel I noticed some small arcing from the cover to the bare metal around the mounting screw threads....

Does this normally happen because of the exposed neutrals in the box or do I have a short somewhere in the box?

I've been in the house for a year and haven't had any issue with the breakers till today. Never even thrown one.

chadvavra 08-09-2007 04:39 PM

update:

I put my Ohm meter across the panel mount and the house ground and it read 0.00.

I think I'm fine, but tell me otherwise if I missed something please.

SecretSquirrel 08-09-2007 07:27 PM

Quote:

Does this normally happen because of the exposed neutrals in the box or do I have a short somewhere in the box?
No, this is not a normal occurance. The bare wires should be the grounds. The white wires are neutrals.

Quote:

I put my Ohm meter across the panel mount and the house ground and it read 0.00.
Try setting your meter for AC volts and read from the panel to ground.

My only theory is that the cover is barely making contact with some exposed wiring and you're getting a bit of leakage. If it was a dead short you'd know it because your hair would be standing on end. Is there anything such as wiring that the cover comes in contact with prior to getting it seated properly?

chadvavra 08-09-2007 08:08 PM

it is very likely that the cover is coming in contact with a bare ground wire before seating on the box.

this brings up a good question. Isn't neutral the same as ground, in as far as where they are connected in the box? I checked and my breaker box has 2 ground buses which are connected to each other by metal strip behind the breakers. Both buses have grounds and neutrals attached to them.

I did check for AC voltage. (I like my meter enough to not want to buy a new one.) With the cover in place it was still 0.00

Update: Just now I went and made sure that the cover did not have any bare grounds touching it before it seated and I didn't get any arcs......

chadvavra 08-09-2007 08:37 PM

My box looks very much like this one.

http://www.heimer.com/photographs/im...r-panel--2.jpg

neutrals and grounds wired to the same bus (on the far right.)

digiwizard 08-09-2007 08:43 PM

slight arcing at the mounting screws in your panel.
 
Quote:

Originally Posted by chadvavra (Post 57029)
i replaced a bad breaker today, no big deal but when I put the cover back on the panel I noticed some small arcing from the cover to the bare metal around the mounting screw threads....

Does this normally happen because of the exposed neutrals in the box or do I have a short somewhere in the box?

I've been in the house for a year and haven't had any issue with the breakers till today. Never even thrown one.

Hello,

Digiwizard here.

This is a grounding issue. You need to determine one of two conditions.

1. Is the main 100 A or larger breaker connected directly to the Electric meter? The service wire, (the largest wire in your panel, should not be connected to a separate disconnecting means). The 100A, 150A or 200A breaker in your circuit panel IS your disconnect)

If this scenario is true then you should have a green screw in the neutral bar which bonds the circuit panel enclosure to the neutral bar. From the Neutral bar you should have at least one, hopefully two large bare or green wires(approx 1/4 inch in diameter). One wire should go to a COLD water pipe, and the other should go to a ground rod outside. This setup allows you to land the ground and neutrals on the same bar(s) within your panel. You should have continunity between the neutral bar and the screw hole(s) in the panel enclosure. Use the screw holes so the paint will not interfere with your reading (screw holes will be bare metal.

2. If you do not have a 100A or larger breaker in your circuit panel then you have a "main lug" panel.

Somewhere between the Electric meter and the panel should be a disconnect. The NEC says that the neutral and the ground shall be bonded at the first disconnect point past the Electric meter or transformer.
This is not verbatum but an interpretation of the code.

If you have a main lug panel then the green bonding screw from scenario #1 should NOT be bonding the neutral bar, to the circuit panel enclosure. The grounds (bare or green wires) and the neutrals (white wires) must be isolated from each other. To avoid a multiple ground path. The neutral bar will be mounted on a plastic or fiberglass insulator and the ground bars will be mounted directly to the panel enclosure. You should have continunity from the ground bar(s) to the screw holes but your neutral bar will be isolated therefore you will not have continuity between the neutral and ground bars.

If you have continuity between these bars then you might have have a green bonding screw bonding the neutral bar to the panel enclosure.

If you cannot see a green screw then the neutrals and grounds might be landed on the same bars. Separate the grounds and neutrals.

If you have a main lug panel (without the 100A or larger breaker), and you DO NOT have a disconnect between the Electric meter and the circuit panel then you have an illegal installation (You MUST have a disconnecting means.) Contact an electrician to correct the problem.

Lastly, be very, very careful when working in your panel.
One wrong move could cause serious injury or death.

If you are not sure about something, contact a qualified electrician.

Remember, when working with live electrical wires and such, you MIGHT get a second chance but you only have one life!

This probelm should be corrected.

Take care and be careful

Digiwizard.

**** It's ok to be energized, It's ok to be grounded the trick is to keep them from partying together!! ****

SecretSquirrel 08-09-2007 09:21 PM

Quote:

Originally Posted by chadvavra (Post 57051)
this brings up a good question. Isn't neutral the same as ground, in as far as where they are connected in the box? I checked and my breaker box has 2 ground buses which are connected to each other by metal strip behind the breakers. Both buses have grounds and neutrals attached to them.

The neutrals should be terminated on a separate bar from the grounds. The neutral bar is "bonded" to the box with a bonding screw and that essentially grounds the neutrals. So it would seem that they are one and the same but they are not. If the inspector were to check your wiring you would unbond the neutral bar and he would check for "grounded" neutrals, which having one is a no-no. I think this is the concept that Digiwizard was attempting to explain. I know your immediate concern was about the arching but it appears you have some additional issues that need to be looked at as far as the neutrals and grounds are concerned.

chadvavra 08-09-2007 09:42 PM

Quote:

Originally Posted by digiwizard (Post 57057)

1. Is the main 100 A or larger breaker connected directly to the Electric meter? The service wire, (the largest wire in your panel, should not be connected to a separate disconnecting means). The 100A, 150A or 200A breaker in your circuit panel IS your disconnect)

If this scenario is true then you should have a green screw in the neutral bar which bonds the circuit panel enclosure to the neutral bar. From the Neutral bar you should have at least one, hopefully two large bare or green wires(approx 1/4 inch in diameter). One wire should go to a COLD water pipe, and the other should go to a ground rod outside. This setup allows you to land the ground and neutrals on the same bar(s) within your panel. You should have continunity between the neutral bar and the screw hole(s) in the panel enclosure. Use the screw holes so the paint will not interfere with your reading (screw holes will be bare metal.

I do have a 100A breaker connected to the main and the grounds are in place. (pipe and outside) The neutral bar does have continuity to the screw holes of the panel cover......

But I also have continuity between the neutral bar and the ground bar and each bar has both grounds and neutrals attached to it.

I am assuming that this is not perfect, but also not an immediate fire or device damaging hazard?

Thank you for the information.

--chad

chadvavra 08-09-2007 09:57 PM

Quote:

At the main service panel....neutral and ground are one and the same (they are bonded there)....but that is the ONLY time they are.
http://en.allexperts.com/q/Electrica...-bonding-1.htm


The above is why I am confused...

SecretSquirrel 08-10-2007 06:07 AM

Quote:

Originally Posted by chadvavra (Post 57071)
At the main service panel....neutral and ground are one and the same (they are bonded there)....but that is the ONLY time they are.

The above is why I am confused...

This concept is that all the neutrals in your wiring system are terminated at one point (neutral bar) and that one point is "bonded". This means that there is only one return path for current. Since the neutrals always carry current when a load is present, then for safety's concern they are terminated separately from the grounds as the grounds should carry no potential at all unless during a momentary short circuit. When you bond the neutral bar it essentially becomes grounded... but as stated the neutral system is bonded at only one place and one place only.

Quote:

I am assuming that this is not perfect, but also not an immediate fire or device damaging hazard?

No, it's not perfect but it should be fixed as soon as you can arrange it in order to bring the panel up to code. Having the neutrals and grounds mixed should not pose an immediate risk of fire (in theory) but I would be concerned about the arcing that you reported and that should be addressed immediately. It is possible that when you put the cover on and it touched a ground wire then you had some bleed back from a neutral (because of the mixing) and when the cover touched the box it found a source to ground.

jbfan 08-10-2007 06:37 AM

There is nothing wrong with haveing the grounds and neturals connected in a main panel as long as this is the only place they are connected.
You may have a loose connection somewhere causing the cover to arc.

chadvavra 08-10-2007 09:20 AM

That makes sense and explains the vague nature of all the documentation on this that I've found.

BTW: The arcing wasn't like a 120A welders arc, it was like a dead 9 volt arc. As I said, I moved a couple grounds deeper in the box and it went away.

thanks.


All times are GMT -5. The time now is 12:28 AM.