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This page continues the explanation of why twist-on connectors overheat and lead to failures when used for copper to aluminum pigtailing as an attempt at aluminum wiring repair. The observation explained here is that with this type of aluminum to copper wire splice, resistance increases between the copper and aluminum wires, leading to overheating of the connection and the twist-on the connector.

This is Aluminum Wiring Repair Procedure - Page 8 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.

Color photos of aluminum wire repair procedures, and photos of failed connectors are included. This document describes hazards with existing 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.

Click on the thumbnail sketches below to see each full-sized illustration.

25. As the aluminum-wired twist-on splices age, the wire-to-wire contact increases in resistance and may finally open altogether. The many wire-to-spring contacts also deteriorate (increase resistance) and some may also open completely, as shown in this equivalent circuit.





26. The deterioration process is observed experimentally as a slow but progressive increase in resistance, as the various current paths within the splice degrade. There are less parallel paths active through the spring, and the result can be a red-hot spring when current flows.





27. That is exactly what has happened here. All of the current is passing through only a few segments of the spring and those parts of the spring become red hot.

Text from attachment occurs here:

The Ideal #65 connector has a zinc-plated steel spring. A combination known to be bad in contact with aluminum. Containing a free-burning oxide inhibitor grease, and having a free-burning thermoplastic shell, the connector can ignite readily if failures of the types shown here occur.

The only justification given for marketing this connector as suitable for aluminum wiring is that it has passed the test requirements of UL486C.

That the tests of UL486C are insufficient can be understood by considering the following table. [Table is on next page.]

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Aluminum Wiring Repair Methods - CPSC Meeting 9/28/95
  Contents
  Copper Pigtailing
  Pigtailing failures
  Additional failures
  Field Failures
  Wire-to-wire Contact
  Equivalent Circuits
  Current Flow
  Connection Deterioration
  UL Test Inadequate
  "Special Connector" Failures
  AMP TYCO COPALUM
  Alternative Repair
  Special Concerns
ALUMINUM WIRING HAZARDS & REPAIRS
Aluminum Wiring Repair-
-Methods - CPSC Meeting 9/28/95
Aluminum Wire Risk
Reduce the Risk
Repair Details
DIRECTORY OF ELECTRICIANS - Aluminum Wiring
DIRECTORY OF ELECTRICIANS - FPE Zinsco
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• The Aluminum Wiring Information Website Aluminum Wiring Hazards and Repairs: in-depth info, photos, documents. Main Page.
• The Aluminum Electrical Wiring Hazard Explained (in the document you are presently viewing)
• How to Reduce the Risk in Buildings with Aluminum Electrical Wiring - Overview of Acceptable Repair Practices (in the document you are presently viewing)
• Aluminum Electrical Repair Method Details - "How to" details, how to identify, COPALUM repair, alternative repairs, history, products, research, source of special AMP TYCO COPALUM connectors & COPALUM Electricians (in the document you are presently viewing)
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• The Aluminum Wiring Bibliography: extensive resources on Aluminum Wiring
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• Reducing the Fire Hazards in Aluminum-Wired Homes, Jess Aronstein, Ph.D., This document answers most technical questions about the hazards and remedies of aluminum electrical wiring. Some of the sections of this very thorough document are listed below:
• Fire Hazards With Aluminum to Copper Twist-on Connectors & Acceptable Aluminum Wiring Repair Practices Color Photos, Current Issues. 9/28/95 CPSC Meeting Minutes
• "Is YOUR Aluminum Wiring Safe?" article discussing safety claims made by some people without looking at the wiring, J. Aronstein, 11/21/95
• "Repairing Aluminum Wiring," U.S. Consumer Product Safety Commission Publication CPSC#516 available online
• * Safety Hazards and Safe Inspection Procedures for Electrical and Home Inspectors at Residential Electric Panels
• Electrical Panels, How to Inspect in Buildings, safety for electrical inspectors, electrical panel, fusing, wiring defects, defective products. Inspection Class Presentation
• Electrical System & Wiring Hazard Inspection, Detection, Cause, Remedy, Prevention - Main Electrical Page
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