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Why should you never connect copper and aluminum branch circuit wiring together with standard plastic twist wire nuts?

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 Correct IncorrectDissimilar metal galvanic corrosion and differing thermal expansion rates can cause aluminum connections to loosen, oxidize, overheat, and create structure-fire hazards. Specialized Al/Cu connectors are required.

Why should you never connect copper and aluminum branch circuit wiring together with standard plastic twist wire nuts?

• The aluminum will turn into liquid mercury
• Galvanic corrosion and different thermal expansion create loose high-resistance fire hazards
• It magnetizes the circuit breakers
• It reduces AC power frequency to 30Hz