[RE-wrenches] Classic 150 100 amp output breaker tripping

[Daniel Duffield]

Some years ago, we had a similiar problem with a 50 amp breaker nuisance tripping, we over  analyzed the problem and still could not prevent this erratic issue, sometimes it would work fine for weeks - sometimes days apart, sometimes on sunny days, sometimes on cloudy days.
 In the end the answer was simple and so easy it was overlooked more than once. 
It was just a matter of the proper torque, with the copper compression fitting on a Sq D QO breaker, just a hair breathe too loose, enough heat would build over many hours to change the trip curve. 
We measured, swapped breakers, everything you could think off until we employed a torque wrench with a screwdriver bit. 
Problem vanished, never to come back. 
Not saying this is answer, but sometimes tightening a compression fitting to the correct "feel", by a journeman electrician with 20 years experience, is not good enough. If your crew or organization has torque screwdrivers, we had no excuse not to use them, and back then we found out the hardway.

Daniel O. Duffield
NABCEP Certified PV Installer since 2005
EE 98 & ER01, Albuquerque, New Mexico, IEEE member 1995
DPW Solar (Integration-Division)
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