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-   -   Help! Glowing spot at bonding screw (http://www.diychatroom.com/f18/help-glowing-spot-bonding-screw-125575/)

WillK 12-04-2011 03:02 PM

Help! Glowing spot at bonding screw
 
So I heard a faint sound that could have been either a sizzle or a squirrel on the roof. Since a quiet house with a 5 year old girl, a 6 year old boy and a high strung redheaded wife is something that only happens when everyone is asleep, I decided the best way to figure out if it was electrical was to take off the cover from my main panel.

Sure enough, I saw a little spot glowing on the side of my bonding screw. By the time I took the picture, the spot had cooled down to the point it isn't glowing enough to capture in a photo. However the label next to the spot is burnt and the neutral wire for the dryer shows signs of having overheated.

I have 2 questions:

One thing that seems to be needed is to ensure the bonding screw is tightenned properly, is there any reason to be concerned about doing this (I'd otherwise assume the answer is no, but with enough current to cause metal to glow where there should be no current flow, I don't want to assume it's safe.)

Second question: What could cause this?

For those that don't remember, I installed this panel myself and it was done under permit with very close scrutiny under inspection. All the circuits in this panel are new, my POCO moved the service entrance to this panel just before labor day after which a tree fell on the service entrance.

For some reason I'm having difficulty posting pics, but it's a 200A Homeline panel and I'll get back to post pics later when I Can.

WillK 12-04-2011 03:34 PM

2 Attachment(s)
I have the photos attached now.

The bonding screw was originally green.

I've tightenned the bonding screw a quarter turn but it's still acting the same. I'm pretty sure I probably originally went so far as putting a torque wrench on the screw.

Also I've shut off the breaker for the garage and dryer, but that had no effect.

Could I be getting current jumping from one of the hot wires to the neutral in the service entrance? After the tree fell, I had complained about how the POCO fixed it, but they said it was fine. Their fix put the hot wires under tension.

gregzoll 12-04-2011 03:50 PM

Power surge most likely, somewhere on the same leg that your house is on.

brric 12-04-2011 03:58 PM

Where is the grounding electrode conductor??????????
And what type of electrode(s) do you have?

Stubbie 12-04-2011 04:52 PM

When you say you turned off the dryer breaker and garage breaker and it didn't change anything are you saying that the bonding screw is continuing to glow ?

WillK 12-04-2011 05:09 PM

The panel has a GEC connected to the ground bar on the right hand side and it connects to two 5/8" ground rods.

It does not glow continuously. It is arcing intermitently. It stopped for a little while when I asked my neighbor if he'd stop by and look at it, but it has since restarted.

WillK 12-04-2011 05:11 PM

Quote:

Originally Posted by Stubbie (Post 785948)
When you say you turned off the dryer breaker and garage breaker and it didn't change anything are you saying that the bonding screw is continuing to glow ?

Yes. The arcing it was doing intermitently did not seem to stop when I did anything like shutting off the garage and/or dryer circuit breaker, and it did not change either with shutting off bathroom lights, christmas tree or anything else I tried.

I had been noticing that the bathroom lights would dim for a second here and there in the morning, but I never noticed anything else. Today now that I noticed the ground bonding screw, I'm noticing that when it arcs that a slight dimming of any incandescent lights in the house can be seen.

AllanJ 12-04-2011 05:15 PM

Flip off all branch circuit breakers. Then turn on breakers one at a time or a few at a time. Can you isolate the glowing spot to just one breaker? What appliances does that breaker serve?

Next, unplug everything except for a few incandescent lights. Remove the bonding screw. Turn on the breakers for the incandescent lights. Go upstairs and turn individual lights on and off. Do other lights dim or brighten? Try plugging in the incandescent light into different circuits.

With the bonding screw removed and a few incandescent lights turned on, and all 240 volt circuits (double breakers) flipped off what is the voltage from hot to hot, and from hot to neutral and from neutral to ground in the panel. Write it all down.

By the way, hot shorting to neutral up on the line going to the utility pole will probably not cause the glowing spot you described.

kbsparky 12-04-2011 05:35 PM

It sounds like you have quite a load imposed on the connection between the grounded enclosure of your panel, and the neutral wires.

I see from your photo that you have a separate equipment grounding bar present. You may have back-feeding juice coming in from your water mains, if you are bonded to a municipal water system.

OR your neutral line outside could be bad, and all your juice is returning VIA your water pipes. Either way, you should call the power company.

Is this a sub-panel, or your main service panel (It should be your main service panel, considering there is a bonding screw present)?


Since you have separate equipment grounding bars, AND you are dealing with the main service panel, start by installing a jumper wire between them. That should eliminate the potential between the neutral and the enclosure.

joed 12-04-2011 06:06 PM

Quote:

Originally Posted by kbsparky (Post 785986)
It sounds like you have quite a load imposed on the connection between the grounded enclosure of your panel, and the neutral wires.

I see from your photo that you have a separate equipment grounding bar present. You may have back-feeding juice coming in from your water mains, if you are bonded to a municipal water system.

OR your neutral line outside could be bad, and all your juice is returning VIA your water pipes. Either way, you should call the power company.

Is this a sub-panel, or your main service panel (It should be your main service panel, considering there is a bonding screw present)?


Since there should never normally be any current flow through the bond, this is the best advice you have received. Loose neutral connection on your or a neighbour's service was my first thought.

WillK 12-04-2011 06:53 PM

Quote:

Originally Posted by kbsparky (Post 785986)
Is this a sub-panel, or your main service panel (It should be your main service panel, considering there is a bonding screw present)?


Since you have separate equipment grounding bars, AND you are dealing with the main service panel, start by installing a jumper wire between them. That should eliminate the potential between the neutral and the enclosure.

The arcing at the bonding screw is observed in the main service panel. I originally installed this as a sub with the intent of moving the service entrance such that this panel became the main. Late August is when the POCO completed the move of the service entrance.

My longer term intent is to move all the old circuits from the original main panel, which is now acting as a subpanel. The old work is suspect, but the worst has been replaced.

At any rate, after the PoCo connected, a tree fell on the service entrance. We didn't lose power. The Poco disconnected and reconnected over top of the fallen tree. But the service drop hung too low to the garage, so I called and they came out and pulled it tighter to gain clearance, and reconnected. Then after that I had an electrician replace a broken insulator in the service cap, so that would be a third time the service connection at the top of the service mast was redone.

At any rate, I'll try shutting off more breakers after kids go to bed. I've been meaning to disconnect the old main which is now a sub since that would isolate a big chunk, but the TV and first floor lights run off that and the kids would start shrieking without TV or lights.

WillK 12-04-2011 06:54 PM

Quote:

Originally Posted by joed (Post 786008)
Since there should never normally be any current flow through the bond, this is the best advice you have received. Loose neutral connection on your or a neighbour's service was my first thought.

And the same electrician that replaced my service cap insulator replaced my neighbor's main panel, about the same time the other half of my tree would've landed on his service entrance (actually it fell while they had it down.)

WillK 12-04-2011 06:57 PM

One note I wanted to add: Same time we got the service move, PoCo upgraded the neighborhood including us to digital meters. I was wondering how well this might serve in the PoCo being able to detect a problem remotely if I was to call?

gregzoll 12-04-2011 07:05 PM

Not really. They operate in the same sense that a Ted5000 does, but only update in a lesser rate than the Ted does.

Billy_Bob 12-04-2011 07:19 PM

If an appliance (such as the dryer) were to have a hot shorting to ground, how would that hot current get back to neutral?

Only via that bonding screw?

Do you have 2 ground bars?

Do they both connect to ground via heavy gauge ground wires? Or is one only connected to your ground and to neutral via that screw?


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