Reference Connectors for Evaluation of Aluminium Building-Wire Connectability

A line of aluminum (Al) setscrew splice connectors was developed which, in conjunction with an appropriate test technique, permits evaluating connectabiiity of aluminum building wire. These connectors incorporate features that make them particularly suited to reference purposes: familiar geometry, alI-Al construction, nonplated contact surfaces, and availability of test points for measuring resistances. Use of these Al reference connectors (ARC's) provides the structure within which to separately judge conductor and commercial terminal effectiveness. Where conventional assembly resistance measurements from equalizer to connector do not resolve questions on contact resistance, additional measurements are made from equalizer to individual strand ends and from connector to strand ends. A special concentric probe in which the insulated potential lead is spring loaded within a brass measuring-current-carrying tube simplifies resistance measurements to the free end of a strand. Application of Thevenin's theorem to the three-terminal network represented by the equalizer, connector, and strand allows substitution of an equivalent wye for the complicated network of the stranded conductor termination. Connectability comparisons include 1350-H19 and Al alloy building wire of different Constructions, interstrand lubricity, and sources, including the voluntary inventory program of test conductors for connector qualification under Underwriters' Laboratories Standard' 486B.