Heat Damaged Buss

[Chuck Evans]

Noticed heavy discoloration of the buss connector at the main disconnect at today's inspection. Looks like excessive heat caused this to me. Also, if you look closely at the feeders you can see where the anti-oxidant grease has run down from the connections and even dripped onto the conductors at the dryer breaker. This also leads me to believe that there were some pretty high temps inside this panel. If you look at the ungrounded buss below the connections (i.e., the portion where the breakers attach) that section of the buss looks clean and shiny.

I did shoot this with the IR camera and none of the components were excessively hot at the time.

The client has a friend who is a master electrician and he will be doing a follow-up on this.

Any other thoughts on this?

[Robert Meier]

A few observations. The discolored upper bus and the lower bus are two different metals so it's hard to say if the upper bus has actually been discolored by excessive heat. It certainly does appear that way from the photo's. I can see what you mean about he anti-oxidant running down. Only question is at what temperature does that stuff turn to liquid? It could happen within the normal operating temperature of the conductors. The AL conductors do not appear to be burnt and it does not appear that their insulation has been damaged which would be a sign of excessive heat.

[Chuck Evans]

For comparison, here is a picture of one from a few months ago that was confirmed to be overheated. The coloring is similar, but in this instance both buss sections show discoloration around the connection and there are visible signs of arcing at the site. This one was measured at about 400 degrees after the current was shut off.

In the pictures above you can see some of the patterning of the discoloration and there was some blue tinging also, which leads me to think it's not corrosion. I'll hedge a little on my working in the writeup since I can't be certain it was heat caused. They are already scheduling follow-up with a sparky, so it's going to get a second opinion.