Here's something to think about the next time you're using a cable tie to secure wiring.  A couple of days ago my wife told me that the circuit breaker for the circulating fans in one of her greenhouses was tripping.  I checked it out and found that while the breaker was tripping it did not trip immediately after being reset.  The fans would run for a while, usually several minutes to an hour, and then the breaker would trip.  What I found was the power cords to the fans had been secured to the metal fan mounting brackets with cable ties.  The cords were secured against the flat face of the metal, not an edge, and the fans and the power outlets were both attached to the same metal brackets.  The fans vibrate slightly but you would think that since everything was mounted to the same structure there would be hardly any movement.  Well, there isn't much but apparently there was enough that after 7 years the cord insulation on one of the fans chafed to the point that a bare wire was making contact with the mounting bracket.  The path from the mounting bracket through the greenhouse structure (all galvanized steel) to literal earth ground was good enough that it was tripping a 15A breaker.  (The fan normally pulls 1.4A.)  After fixing the problem fan I checked the other one and found that it was also chafing and was very close to shorting as well.

 

Granted this is not aircraft wiring and it did take 7 years of continuous operation to fail, but the vibration involved was very slight and the power cord was being held against a smooth, flat piece of metal.  Think about the harsher conditions, mechanical and environmental, under the cowls of our airplanes and give some extra thought to simply using a cable tie to secure wiring to any convenient surface.

 

Just some food for thought for those of us doing our own wiring.

 

Tom Gourley