Slide 17 Aluminum Wire: Failure to make adequate wire-to-wire metallic contact leads to overheating aluminum wire connections

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This article explains the reasons for and effects of inadequate contact between aluminum conductor wires inside of a twist-on connector.

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Inadequate Contact Between Aluminum Conductors in Twist-On Connectors

Color photos and descriptive captions from CPSC Meeting 9/28/95. In this document aluminum wire twist-on connector failures and repair procedures are described, including aluminum wire repair methods which work and methods which do not work and are unsafe. This document series describes hazards with existing aluminum wiring repair products, explains the aluminum wiring failure mechanism, and reviews recommended retrofit procedures including use of readily-available materials.

This information was presented to the US Consumer Product Safety Commission by Dr. J. Aronstein, 9/28/95. The minutes of that meeting were obtained under the Freedom of Information Act and posted by Daniel Friedman January 1996.

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Slide 17 17. The characteristic heating in a band around the connector shows us where the heat is being generated. In all of those failures shown, from both lab and homes, the heat is generated by current flowing in the connector spring. Here, all of the current is passing from wire-to-wire through sections of the steel spring.

Slide 18 18. Current flow in the steel spring occurs due to a fundamental deficiency in this type of connection when made with aluminum wire. There is inadequate metallic contact directly established from wire-to-wire. The insulating oxide on the aluminum is not sufficiently broken up. (Photo: connector removed after splicing.)

Slide 19 19. The amount of twisting together of the wires varies substantially with the hardness, size(s), and number of wires installed. Inadequate mechanical disturbance results in poor electrical contact at the wire-to-wire interface. This is a fundamental deficiency of twist-on connections with aluminum wire.


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