Main breaker tripping

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Old 02-15-18, 09:08 PM
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Main breaker tripping

I have an EVSE that has been working for a couple years. Recently it seems to be causing my main breaker to trip. The breaker gets very hot when it trips. Not the 40a breaker on the line, but the 100a main house breaker. I have a Sense energy monitor installed so I can tell that the first time it happened we were using over 11kw, but recently itís been happening at usage as low as 7.8kw. We had to replace the EVSE once before due to failure to charge. So that was my first suspect, but it seems to me if it was causing the 100a breaker to trip due to some circuitry fault, it would also or instead trip the 49a breaker. Do I have a bad 100a breaker? Or something else?
 
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Old 02-15-18, 09:13 PM
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It would be helpful to have amp reading from both legs of the panel. What size service do you have? Has anyone checked the bus Connections?
 
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Old 02-15-18, 09:38 PM
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I can only get individual legs in real time. I will try to setup a test to get that. The whole house only has 100a service. No one has checked the bus connections. Is that something that can change on its own?
 
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Old 02-15-18, 10:06 PM
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If a connection is loose it will start to arc . As the contacts pit the arcing gets worse and more heat will build up.
 
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Old 02-16-18, 10:10 AM
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This sounds like it might be my problem. We have also had what appeared to be brown out conditions as well. So I would think that bad busbar connection could cause that too. We are in a mobile home so I can cut the power at the pedestal and safely remove the main breaker and check the bus bar conditions
 
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Old 02-19-18, 01:54 PM
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It got worse and worse. Finally blew with only a few hundred watts being used. When we tried to reset, got sparks from main breaker. Pulled it. One leg was obviously burnt. Yes, bus bar tab for that leg had some pitting. We carefully knocked down the highest peaks with a jewelers file before putting in the new breaker. Worked fine, no heating at all. Finally tried charging car today, no problem or heating at all. Stone cold. Going to have electrician out this week to check bus bar. Thanks for your help.
 
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Old 02-21-18, 07:55 PM
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One leg was obviously burnt. Yes, bus bar tab for that leg had some pitting. We carefully knocked down the highest peaks with a jewelers file before putting in the new breaker.

You made at best a temporary repair. When aluminum bus stabs burn and pit and are filed, the tin plating is removed which allows the aluminum to oxidize. Prepare now for replacing the panel in the not-too- distant future.
 
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