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Old 09-02-2012, 12:47 AM   #1
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bending 35 yr old Al 4/0 SE


I just installed a Reliance manual transfer switch between meter and main panel. Had to bend the old SE to fit it to the lugs in the Reliance. Pain in the ass. It wouldn't bend and then even once bent it would just spring back to its original shape. Had to bend it almost 180o to get it to keep a 90o bend. The new SE 4/0 Al was a pleasure by comparison.

Anybody else had this experience? Anyone know if it's due to changes in the metal over the 35 years since the house was built? Or are we using friendlier alloys these days?

All done, passed inspection. Just curious. Thanks.
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Old 09-02-2012, 03:22 AM   #2
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bending 35 yr old Al 4/0 SE


Like many metals, aluminum's hardness and springiness varies depending on the metal's temper. Temper is a function of the microstructure of the metal - how large the continuous crystals of metal are and what their shape and orientation are. Newly processed aluminum wire is annealed, so it's in the softest state. It hardens by bending (or any other plastic deformation), but also hardens naturally over time. This is a slower version of the same thermal-treatment hardening process used to make high strength aluminum parts. After 35 years, aluminum wire will have hardened substantially by natural precipitation hardening. This makes it much springier than new wire. There also may be differences in the manufacturing and metallurgical properties of wire from 35 years ago that made it harder to handle.
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Old 09-02-2012, 09:49 AM   #3
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bending 35 yr old Al 4/0 SE


Yup, thanks, that's what I figured. Be interesting to know though, how much of the effect is due to changes in crystal structure of the metal vs. changes in the alloy composition. I did some Googling but didn;t fid anything useful/relevant.
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