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retightening panel lugs


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Talking with an electrical contractor the other day, he had just finished replacing a 15 yr old exterior pedestal main breaker and meter base. His comment was that he see quite a few melt downs due to improper tightening lugs in panels, especially main lugs.

His suggestion was retighten everything in panel after first year, then check every 10 years from there.

Fluke, Overkill or good advice???

...Anybody talk to folks about retightening lugs in their panels???

Though probably a good idea on especially older panels that haven't been opened in years.

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I wouldn't recommend it because I see very few incidents of main lug failure from bad connections. Heck, if you're going to recommend that, what about being consistent and recommending the tightening of every screw in every breaker, neutral bus, ground bus, receptacle, switch, etc. A loose connection in a receptacle can generate enough heat to start a fire too. Eventually the recommendation list is discarded as impractical.

Marc

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AFAIK, the lugs are supposed to be torqued to a specified amount, the way you torque down a cylinder head on an engine. There should be no need to ever go back over the connections, IMO.

I agree with the "specified amount" portion John. I don't think that means things will stay there. IR testing in industrial facilities often identifies terminals that have weakened over time.

The idea of just tightening things again isn't necessarily the right thing to do. If you retighten something, you might actually cut through part of the conductor. Sometimes the right way is to remove the conductor, cut and strip it, and reinstall it. That would be especially important with aluminum.

Over-tightening can be just as bad as not enough torque. Around here, we have at least one jurisdiction that requires the contractor to have a torque wrench and torque screwdriver, and to torque the connections in the inspector's presence. If they call for inspection without those tools, it is an automatic turndown and reinspection fee.

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Torque screwdriver,

Jeez, now I gotta get one for my toolbox. Wish you hadn't mentioned that, Douglas.

Nope, won't be using it on the job. I'm just a little bit OCD. I've got a three different size torque wrenches - I only use one - now I can feel the pressure building up inside to find one of these.

Thnk I need to join a twelve step program for OCD types.

ONE TEAM - ONE FIGHT!!!

Mike

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  • 4 weeks later...

AFAIK, the lugs are supposed to be torqued to a specified amount, the way you torque down a cylinder head on an engine. There should be no need to ever go back over the connections, IMO.

I agree with the "specified amount" portion John. I don't think that means things will stay there. IR testing in industrial facilities often identifies terminals that have weakened over time.

The idea of just tightening things again isn't necessarily the right thing to do. If you retighten something, you might actually cut through part of the conductor. Sometimes the right way is to remove the conductor, cut and strip it, and reinstall it. That would be especially important with aluminum.

Over-tightening can be just as bad as not enough torque. Around here, we have at least one jurisdiction that requires the contractor to have a torque wrench and torque screwdriver, and to torque the connections in the inspector's presence. If they call for inspection without those tools, it is an automatic turndown and reinspection fee.

I always retorque cylinder head bolts after the first heat cycle and complete cool down after I build a motor.

As far as panels go if Im in there working on something else Ill check all the connections while Im in there,Its a crap shoot though .

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