Quote:
Originally Posted by Al Skierkiewicz
Aren,
The breaker is a simple bimetallic device. As the current flows through it (and heat is generated), the contact latch cam deforms due to the expansion of two different metals. Theoretically, the breaker could exist forever at just under the trip temperature without damage. Pushing the red button merely forces the latch cam back to a position that prevents contact.
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I'm aware of the operational principle. Pressing the red button to manually release the latch cam does not increase its temperature, and perhaps does not even force any deformation (elastic or plastic). We all know that this mechanical action, typically performed with the breaker closer to room temperature, does no harm to the breaker internals, since we have successfully used the breaker for years.
But things change under a trip condition when all the components are much hotter, and perhaps plastic deformation thresholds are different. It's also not clear to me whether there is any material deformation at all when the button is pressed, while there is of course significant deformation due to heating in an over current condition. This difference in conditions could conceivably lead to component damage in a trip condition while there is no damage when the button is pressed.