Called BS on using a torque screwdriver for breakers until I snapped a lug on a Square D panel last Tuesday

Was in a rush on a 200 amp service upgrade in Phoenix. Hand tightened a 4/0 aluminum lug like I always do, felt normal, then went to test it and the lug cracked right at the threads. $40 part and an hour of my time gone. My journeyman handed me his torque screwdriver and said this is exactly why. Tested it on the replacement, 50 in-lbs felt way tighter than I would have guessed. Anyone else had lugs fail on them from hand tightening?

2 comments

2 Comments

gonzalez.grant1mo ago

Practice on some scrap lugs first so you get a feel for what proper torque feels like in your hand. Your hand can learn the muscle memory, you just gotta give it a chance.

angela_carter1mo ago

Laid into a Square D QO breaker last summer with my bare hands on a 100 amp feeder, snapped the terminal screw right off. Felt like a total dinosaur standing there with the piece in my hand. Borrowed my buddy's Wiha torque driver after that and it's been a rude awakening. What I thought was "snug" was actually way over, and what felt tight but safe was still loose. Makes you wonder how many panel fires start because somebody like me was just winging it with a #2 square.