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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 for upgrades.  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 1960's and 1970's. New types of wires, aluminum wire rated devices, and equipment with an aluminum wire approval have all been tested to be safe.  Click here to read a short history of "Aluminum Building Wire" published on WikipediA.   ALUMINUM WIRING INSPECTION If you own a house that was built in the 1960's or 1970's and it was wired with aluminum wiring throughout, there is no need to panic.  However you will need to take some steps to be sure that the wiring is currently in good operating condition and is 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 was 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 with a low melting point the wired connection would melt. When that became apparent it was then required to use 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 the aluminum wire was that it had a greater expansion and contraction capacity over copper.  So when the wire was under a large load such as an electric heater it would expand.  Then when the load was off the wire would contract.  Over time this caused the connections under screw terminals to become loose which led to arcing and burning and melting. It is very important when installing aluminum wire that all connection and termination points are rated and approved for its use. It is possible that a previous owner took the necessary precautionary measures to ensure that the existing aluminum wire is 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 to have a 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 be able to see the aluminum wires on the screw terminals.  Shining a flashlight inside may help. Try to see if there is an aluminum wire connected directly onto the screw terminal.  Also look inside the electrical...