Message Board Thread - "Differing temp on one side of breaker"

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Differing temp on one side of breaker jlowell 2/22/2011
I recently found a breaker that is showing a temperature differnence on the top side of the breaker. The bottom side has a similar pattern but has 10 degree Celsius lower temperature. The load is even on A & C while B phase has almost 10 amps more. While the temperature of 32C is not by itself high, is this uneven heating a earmark of a potentially failing breaker or a normal heating pattern. Thanks in advance for any help.
Re:Differing temp on one side of breaker jlowell 2/22/2011
I forgot to load the image in the origianl post.
Re:Differing temp on one side of breaker IRJay 2/23/2011
This pattern is the linkage path for the current flow. This breaker obviously has a significant load for a while for this to appear. It is not necessarily a problem. The reason I say this is that the heat is uniform and staying within the internal workings of the breaker. If one of these areas was standing out then the indication would assume a connection issue in that area. You could double check the breaker with a millivolt drop across each leg. but note this pattern we see is load related and lags the current by quite a bit because of the conductivity and heat capacity of this material.

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Re:Differing temp on one side of breaker MCB 3/7/2011
I've seen molded case breakers with uneven temperatures outside, being the result of connection problems on the inside. Depending on the usage, these connections may get pitted or arced causing a higher resistance connection, and more heat. The outside temperatures on molded case breakers could be compared to bus duct, in that any problem has to "get through" airspace before being "seen" on the outside.

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