I’ve read through past topics with this similar concern and im not finding a conclusive answer so I’m posting here. Siemens sub panel one bus bar had significant discoloration. Is this from possible over heating? Thanks for any help with this.
Given that it’s at the end of the bar I would say that it didn’t overheat but it’s hard to tell from a photo. Is there any other indication of overheating like damage conductor insulation?
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No nothing else anywhere that I saw.
Kind a looks an loose connection to the bus bar with a overloaded breaker.
Given that the discoloration is consistent for the entire visible length of the bus IMO it was not caused by heat but rather by something to do with the metal itself. In order for the heat to travel all the way to the end of the bus it would need to be significant and therefore there should be some other visible damage from a large amount of heat being generated. To know for sure you would need to remove the circuit breakers and check the entire bus.
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From here in Ohio it looks as if the zinc plating is discolored. Probably was like that when installed.
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It looks like just discolored bus to me. no plastic connections melting. I’m concerned about the enormous amount of rust in the panel though.
The likelihood of the discoloration being attributable to loose connections or overloaded circuits is almost zero.
Discoloration of tin-played busbars is common, and not usually an indication of a problem.
Some Seimens busbars are tin plated. Some are bare aluminum. The busbars in the subject panel look like they are tin-plated. Aluminum is non-magnetic. Tin is weakly magnetic. You can use a magnet to determine whether the busbars are tin-plated.
Tin can change color with relatively small temperatures changes. Cold can darken tin just as heat can darken it. Remove the other breakers on the right side. If the color is the same as the exposed part of the busbar, that’s a good indication that the busbar was exposed to cold, probably during storage before the panel was assembled.
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It could be discolouration or soot from a short circuit fault, though is hard to tell from the picture. Circuit breakers release carbon when they trip in a short circuit fault which looks like this. It may have been that there was a fault on the right hand side and breakers have been relocated since then. You can tell the difference as soot scrapes off (obviously isolate the board first) wheres the discolouration wont. If it is discolouration then it is perfectly fine.
Fun to have some input from around the world, Steve. Quite the website.
Welcome!
Morning there, eh?
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Thanks Larry!
Yeah a sunny morning in Sydney 
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No, it couldn’t. The discoloration is not consistent with any kind of fault.
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