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What caused this?


Robert Jones
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This service panel was added/updated in June 2009. Client called me to state that half of their home was without power and that there was sparks coming from the panel. They also stated that for the last week or so, that the lights in the home were flickering. This is the only location that I can find any signs of arcing. Would this be caused by the nut not being completely tightened?

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This service panel was added/updated in June 2009. Client called me to state that half of their home was without power and that there was sparks coming from the panel. They also stated that for the last week or so, that the lights in the home were flickering. This is the only location that I can find any signs of arcing. Would this be caused by the nut not being completely tightened?

Sure. I'd have to wonder why though. That particular nut is tightened at the factory and it's very rare to have one not tightened to spec. It makes me wonder if someone messed with it.

Your pictures would make good illustrations for Billy Bob's recent post in the "toaster" thread. As he points out, good electrical connections are all about pressure.

- Jim Katen, Oregon

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Yes that is the kind of connection which would have "detailed engineering specifications" as to proper installation, maybe need to apply some sort of goop, and the nut would need to be tightned to a certain tightness. (Or the connection could fail.)

But this is not something which would be messed with in the field, so probably no mention of how to install that connection on the label. I would call the panel manufacturer and ask if the connection can be repaired or if the whole panel has to be replaced.

FYI - I used to service large mini computers the size of a refrigerator. These had a main DC power supply of about 10 volts. And the main wires to this were the size of car battery cables. (Lots of amperage.) And there was a problem with the connections to these cables getting hot. And you could touch these connections because it was only 10 volts DC. They were hot to the touch.

Anyway engineering studied the problem and told us to get torque wrenches and tighten the bolts to a certain tightness...

So there I was in the computer room with an automotive tourque wrench going at it with all my might. My boss walked by and saw me and said; "What on earth are you doing? Are you going to change the oil next?" (I explained.)

Anyway I tightned the nuts to what the engineers said to, then the connections were cool after that! (They were already what I would call "tight" before that. After using the torque wrench, they were more tight though.) Quite interesting!

WARNING! Never touch the main connections on an electric panel! The power is *always* on to these connections even with the main breaker off! There are "non touch" temperature guns you can aim at something like this and get the temperature.

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Hi,

Yeah, that looks like the main connection between that breaker and one of the two power buses.

Having a loose nut there would be like having a loose breaker-to-bar connection in a Zinsco panel - it would arc every time there was enough vibration/movement to create a tiny air gap and over time everyting around that nut, plus the nut and the bolt it's threaded to, will become all pitted and covered with crud and the connection will get worse and worse until one day it'll really get going and the heat will melt down everything in that panel into one big sticky mess.

ONE TEAM - ONE FIGHT!!!

Mike

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