I love the knowledge from my readers and this tip from retired electrician Larry Skarin is just an example of why. Here is an email I received from Larry in response to the Short Circuit / Circuit Overload section of my tutorial on Reasons Why Circuit Breakers Trip.
I added his suggestion to the article.

Thanks Larry!

• Subject: Another (and rare) cause for circuit breaker tripping.
  "My electric dryer kept tripping the ganged 30 ampere breakers, yet the dryer was working correctly. There was no evidence of a defective induction motor nor shorted heating elements.
  
  The problem was the connections from the #10 wires to the breakers -- the screws were tightened too loosely, and the heat generated by this high resistance connection found its way into the breaker's overload mechanism. Tightening the screws solved the problem.
  
  This was a Cutler-Hammer box and it WAS copper wire."
  
  Lawrence Skarin
  Retired Electrical Engineering Professor
  Rochester, NY