Slide 4 Aluminum Wire: Copper Pigtailing Failures on CPSC Test, Examples
     


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Aluminum wiring repair failures at copper pigtail connections: Illustrations, photos, and explanation of overheating and failures at copper pigtail connections used to repair aluminum wire. In this article series aluminum electrical 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.

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Aluminum Wiring Repair Failures due to overheating at copper pigtails using twist on connectors

Color photos of aluminum wire repair procedures, and photos of failed connectors are included. 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 4 4. Burnouts like this occurred when various UL-listed twist-on connectors were tested for the pigtailing application, installed as per the manufacturers' instructions. Poor test results for twist-on splices with aluminum wire were reported by UL, Battelle, CPSC, and various wire and device manufacturers.



Slide 5 5. The fire hazard posed by these splices when they fail is easily seen when the "burnouts" are observed while passing current. At about 17 amps, less than the 20 Amp rating of the (#10 aluminum wire) circuit, the connector spring is red hot. The voltage drop is about 2 volts, so downstream loads operate normally.



Slide 6 6. Additional red-hot twist-on connector splices fr6m the CPSC tests are shown here. The key point is that a significant percentage of the CPSC test splices over a period of several years failed in this hazardous manner, the spring becoming red hot. The connector shells ignited (smoldering combustion).



Slide 7 7. These tests were all conducted within rated service conditions. Applied current never exceeded 90% of the circuit rating (based on aluminum wire size used). The twist-on connectors used were UL listed for the application, and were installed as per the manufacturers instructions.

 

 

Aluminum Wiring Repair Failure Photos & Causes: overheating at copper pigtails using twist on connectors

 

Slide 8
8. Simpler splices also failed. Here is a basic splice with two aluminum wires. Overheating is evident in the discoloration band around the shell. This is a characteristic heating pattern for failing aluminum wire twist-on splices. With time, further degradation occurs, and fire hazard develops with current loading.




Slide 9
9. The characteristic burn pattern is an important clue toward understanding the failure mechanism of the aluminum-wired twist-on connector splices.




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