My journeyman said to always use a torque wrench on main lugs, but after a service call in Denver last week where a lug torqued to spec was still loose, I'm not so sure.

The spec sheet said 50 in-lbs, I hit that, but the thermal imaging showed a 15-degree hotspot because the aluminum bus bar was oxidized, so has anyone found a better method than just going by the book number?

3 comments

3 Comments

hunt.quinn22d ago

Had a panel last year with the same problem. I started using a small amount of antioxidant paste on the bus bar before putting the lug on, and it made a real difference. The torque wrench reading became a lot more reliable after that.

dylanfisher28d ago

A buddy of mine had the same issue on a panel retrofit. He started cleaning the bus bar with a wire brush and a bit of contact cleaner before torquing, and his hotspots went away. The book number is a starting point, but surface prep matters just as much.

wilson.anna27d ago

Totally makes sense. I've seen that too, where a little cleaning fixes what the torque wrench couldn't. It's easy to forget how much grime builds up.