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Aluminum wire terminated under two screws that have overheated

Aluminum Wiring

Dear Mr. Electrician: Is aluminum wiring safe to use?  I am planning to have the electrical service to my house upgraded. The licensed electrical contractor that I am using will be installing aluminum wire for this installation.   Answer: Yes, it is safe to use aluminum wiring for new installations and upgrades.  Table of Contents: Inspecting Aluminum Wire Repairing Aluminum Wire Oxidation NOTE: Some text links below go to applicable products on Amazon.  As an Amazon Associate, I earn from qualifying purchases. Aluminum wire does have a questionable past, and problems still occasionally surface to this day from improper installations that date back to the 1960s and 1970s. New types of wires, aluminum-rated devices, and equipment with aluminum wire approval have all been tested to be safe.  Click here to read a short history of "Aluminum Building Wire" published on Wikipedia.   Top Of Page ALUMINUM WIRING INSPECTION If you own a house built in the 1960s or 1970s and wired with aluminum throughout, there is no need to panic.  However, you will need to take some steps to ensure the wiring is in good operating condition and properly installed. The issues with the wiring at that time became apparent over time.  It turns out that the alloys used to make that wire back then were subject to oxidation.  As the oxidation at the connection points got worse, so did the resistance of the connection.  This caused the connections to arc and burn, and the wired connection would melt with a low melting point. When that became apparent, it was then required to use an anti-oxidant compound on all aluminum wiring connections.  However, now the aluminum alloy has been changed, and on new aluminum wiring installations, it is not required to use an anti-oxidant unless specified by the manufacturer. Another problem with aluminum was that it had a greater expansion and contraction capacity than copper.  So it would expand when the wire was under a large electrical LOAD, such as an electric heater.  Then when the LOAD was off, the wire would contract.  Over time, this caused the connections under screw terminals to become loose, leading to arcing, burning, and melting. It is very important when installing aluminum wire that all connection and termination points are rated and approved for its use. Top Of Page It is possible that a previous owner took the necessary precautionary measures to ensure that the existing aluminum wire was connected properly.  However, you will have no idea if the repairs were done or done correctly unless you investigate or have an inspector or electrician take a look. The simplest thing to do is look at your electrical switches and receptacles inside the electrical box.  Turn off the power at the circuit breaker before doing this.  If you remove the wall plate over a switch or electrical receptacle outlet, you may see the aluminum wires on the screw terminals.  Shining a flashlight inside may help. Try to see if an aluminum wire is connected directly to the screw terminal.  Also, look inside the electrical box for purple-colored wire connectors commonly used for...