Aluminum cable to copper connectors

[edko]

The connectors used on an old installation were copper and the cables aluminum. Has anyone heard of thermal runaway where the contact surface of the lug eventually breaks down after 40 years of service. Understanably, this is not the right connector to use for aluminum cable because it is dissimilar.

 

[Laplacian]

I have seen this type of connection fail after just a few years, but it was an outdoor application exposed to cooling tower drift. The AL had corroded, and pitted away where the CU was in contact. Additionally, the AL oxides swelled in between the connection, forcing the lug away from the pad.

Similar installations at the same plant were inspected, and were found with corrosion and pitting, but not to the extent of the area near a cooling tower.

Hubble makes a NEMA bolt-hole dimensioned metal strip that goes between the lug and pad for this application. It is a thin plate consisting of two sheets (20% CU, and 80% AL by thickness)of the two metals molecularly bonded.