Analysis of field failures of aluminum-copper pigtail splices made with twist-on connectors

A new type of twist-on splicing connector for use with aluminum and copper wire combinations was utilized to reconnect wire terminations in a group of residential apartment units. The connector differs from conventional twist-on connectors in that it is pre-filled with a corrosion inhibitor compound containing suspended particulates. Burnout occurring among these splices led to removal and replacement of all of the new connectors. In this study, the connectors removed from 102 apartments were inspected for signs of overheating and for indications of abnormal conditions that might cause the failed connectors included samples that were applied to rated wire combinations and showed no sign of abnormal installation or application conditions. Tests of the aluminum conductors from the apartments reveal no abnormalities that could account for the poor performance of the new connector. The inhibitor compound inside the connector was determined to be of limited effectiveness in improving the wire-to-wire contact through the high resistance film on the aluminum wire surface. On the basis of the field failures in combination with previously reported laboratory studies it is concluded that the connector is not suitable for permanent use with aluminum wire residential wiring systems.