How To Look At A House
McGarry and Madsen's home inspection blog for buyers of
site-built, mobile/manufactured and modular homes
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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