Evaluation of an Aluminum Conductor Material for Branch Circuit Applications

An experimental aluminum wire alloy containing Mg was among many tested in the early 1970's in research directed toward the solution of aluminum wire connection problems. Unlike other alloys tested at that time, its performance in heat-cycle tests of splices made with twist-on connectors was equivalent to copper wire. Enrichment of Mg at the wire surface appeared to account for the improved connectability of this alloy. Presently, an alloy containing a significant concentration of Mg, with Mg enrichment at the surface, is certified for use in Canada. This present investigation evaluates the Canadian alloy aluminum wire using two-wire (Al-Al) splices made with "special service" twist-on connectors installed with controlled tightening torque. No current flows in the test samples except when measurements of potential drop are made. Applied test conditions are within the normal rated application range for connections of this type. After one year of testing substantial progressive increases of connection resistance are evident among the splices made with the Canadian alloy. No performance improvement is seen with this alloy compared with other aluminum conductors tested. It is doubtful that stable and safe long-term performance will be achieved with this alloy in large-scale field applications involving the present types of connections. The reasons are noted, and the weaknesses of the qualification standards testing for aluminum wire are discussed