Aluminum wiring has never stopped being used. Only a particular type of smaller-gauge single-strand aluminum is no longer available for residential wiring. It was substituted for copper from the mid-1960s to the mid-1970s because the price of copper skyrocketed during that period. 

   Solid aluminum wire turned out to have several problems that caused a lot of house fires. It has a high coefficient of expansion/contraction compared to copper, and the movement loosened of wire connections. Corrosion was also a problem, and aluminum is softer than copper and easily nicked. While it is a good electrical conductor, if not quite as good as copper, the surface corrodes to aluminum oxide, which is an insulator. Although that type of wire is no longer manufactured—and special switches, receptacles, and breakers rated for use with it were approved as a retrofit safety fix—many insurance companies will not insure a house with this wiring unless inspected and approved by a licensed electrician. 

     Many new homes today have multi-strand large-gauge aluminum wiring as service cables to the main panel and from the panel to major appliances, such as an electric range or furnace, and it is quite acceptable. The exposed wire at connections is usually coated with the required gray or black anti-oxidant paste, as shown below.

    And here’s an example of aluminum wiring at lugs with the anti-oxidant paste missing.

    Also, see our blog posts I heard that aluminum wiring is bad. How do you check for aluminum wiring? and Is aluminum wiring allowed in a mobile/manufactured home? and Does a home inspector check for aluminum wiring? and Is antioxidant paste code required for aluminum wire lug connections? and I heard that aluminum wiring is bad. How do you check for aluminum wiring?

• • • • • • • • • • • • • • • • • • • • • • • • • • •

Here’s links to a collection of some oour other blog posts about ELECTRICAL WIRING:

• Which house appliances need a dedicated electrical circuit?

• Can a short circuit cause a high electric bill?

• What is the maximum spacing requirement for securing NM-cable (nonmetallic-sheathed cable)?

• Is it alright to just put wire nuts on the end of unused or abandoned NM-cable or wiring?

• What causes copper wires to turn green or black in an electric panel?  

• What are typical aluminum service entrance wire/cable sizes for the electrical service to a house?

• Why is it unsafe to bond neutral and ground wiring at subpanels?

• Should I get a lightning rod system to protect my house?

• Why is a strain relief clamp necessary for the cord connection to some electric appliances?  

• Does a wire nut connection need to be wrapped with electrical tape?

• What is the minimum clearance of overhead electric service drop wires above a house roof?

• What are the requirements for NM-cables entering an electric panel box? 

• What is the color code for NM cable (Romex®) sheathing?

• Why are old electrical components not always "grandfathered" as acceptable by home inspectors?

• How can I find out the size of the electric service to a house?

• Can old electrical wiring go bad inside a wall? 

• What is an open electrical splice?

• What are the most common electrical defects found in a home inspection? 

• What is the life expectancy of electrical wiring in a house? 

• What is an "open junction box"? 

• How dangerous is old electrical wiring? 

• What is a ground wire? 

• What is "knob and tube" wiring?  

• What is the code requirement for receptacle outlets in a closet?

   Visit our ELECTRICAL page for other related blog posts on this subject, or go to the INDEX for a complete listing of all our articles.