How To Look At A House

McGarry and Madsen's home inspection blog for buyers of  

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I heard that aluminum wiring is bad. How do you check for aluminum wiring?

Thursday, October 4, 2018

Multi-strand aluminum wiring  is approved by building codes and regularly used for service cables (the main electric wires coming into the home’s panel) and for wiring to major appliances, such as air conditioning condensers, in the Gainesville area. It is easily recognized by its color and the anti-oxidant paste applied over the bare metal strands at connection lugs, as in the photo above. Although solid aluminum wires of an approved alloy is also acceptable per NEC, we have not seen any of it in our area in newer homes.

   The problematic aluminum wiring that you heard about is single-strand aluminum wiring of a particular alloy that was manufactured beginning in the mid-1960s, when copper prices spiked. It was a lower-priced alternative to copper, and installed in some homes from 1965 to 1972.

    Aluminum’s high coefficient of expansion caused wiring connections to loosen, and started numerous electrical fires. For while, a number of special replacement connectors were tried, in an attempt to alleviate the problem and still leave the wiring in place. Most did not function adequately. Ultimately, one obtained UL-approval, but many insurers simply would not issue a policy on a home with the older aluminum wiring, so virtually all of it has been replaced over time.

   We look for single-strand aluminum wiring in the electric panel as part of your home inspection, but rarely see it anymore. There is a type of house wiring that looks similar to aluminum, but is actually a tin-coated copper, and predates the era of problematic aluminum wiring. It usually has a cloth sheathing, and we typically find it in pre-1950 homes that still have some of their original electrical system intact.

   There is, however, one problem that occurs with the modern, code-approved multi-strand aluminum wire: oxidation (corrosion) of exposed strands at lug connections where the anti-oxidant paste is either missing or poorly applied. The oxidation reduces the current-carrying capacity of the wire and it heats up at the corroded area. The video below demonstrates how we find overheating problems like oxidized wiring in panels with the infrared camera.

    Also see our blog posts Does a home inspector check for aluminum wiring? and When did they stop using aluminum wiring? and Is aluminum wiring allowed in a mobile/manufactured home? and Is antioxidant paste code required for aluminum wire lug connections? and What are typical aluminum service entrance wire/cable sizes for the electrical service to a house? 

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Here’s links to a collection of our 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?  

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. 

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