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Why should you build a rooftop lightning protection system with either all copper or aluminum components? Answered

I bought a book from Home Depot to learn about household wiring:

http://www.amazon.com/Wiring-Complete-Editors-Creative-Homeowner/dp/1580111602/ref=sr_1_1?ie=UTF8&s=books&qid=1279657048&sr=1-1

On pg. 238, about lightning protection systems, it says, "...these instructions are for copper only-do not use copper with aluminum."

Why shouldn't we use copper components with aluminum? It's essentially just a couple of lightning rods and a cable leading to a ground rod. I can scan the page if you'd like to read it. They made it sound fairly important. 

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NachoMahma

Best Answer 8 years ago

.  You want to provide the lowest resistance to ground possible. Using Al and Cu together causes galvanic corrosion which causes high resistance.

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GorframNachoMahma

Answer 8 years ago

+1.

And the resistance becomes especially high when the aluminum disappears because it's all been corroded away. You don't tug on Superman's cape, you don't spit into the wind, and you should never place dissimilar metals in electrical contact.

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caarnteddGorfram

Answer 8 years ago

Don't place dissimilar metals in contact (electrical or not) if they are exposed to the elements. Rain makes a good enough electrolyte to leave a hole where your zinc coated roofing material used to meet your lead flashing :D

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Gorframcaarntedd

Answer 8 years ago

Right. I should have said *any sort* of contact - electrical contact including physical contact, sharing an electrolyte (like rainwater), or being hooked up by wires. To move from misquoting Jim Croce to a direct quote from one of my Corrosion Engineering professors: "The joy of love may last but for a moment, the pain of love may last a a lifetime, but _Corrosion_Goes_On_*Forever*."

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GorframGorfram

Answer 8 years ago

Sorry for the bulky text and clumsy formatting. Rich Editor seems to have taken himself out to lunch. (Why not? - After all, he's rich. :)

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steveastroukNachoMahma

Answer 8 years ago

Oh the joy I had as a student working as an electrician in Connecticut 25 years ago, where we seemed to spend half our time remaking triplex drop cables where they connect to split nuts and the copper down cables to the service box. We found a nice gunk, which we scrubbed into the wires and the joints, and which, it was claimed, stopped the corrosion effects. Add a roll or two of insulating tape as a seal, and they were good to go