The International Copper Association Releases Test Results Comparing Connectivity of Copper and Aluminum Wiring in Electrical Wiring Applications

November 11, 2014


Copper Wiring with Copper Connectors Exhibit Most Stable Performance

NEW YORK, NY— Copper wire with copper connectors has proven to be more reliable and outperform aluminum alloy wiring systems for power distribution applications, according to a new study undertaken on the behalf of the International Copper Association.

The study compares three types of electrical connections, including copper connectors between copper wires, aluminum dual-rated connectors between copper wires, and aluminum connectors between aluminum alloy wires.

Mechanical screw type connectors were used to connect lengths of #1 AWG copper wires and #2/0 AWG (8000 series) aluminum alloy wires. These wires are typically used in power distribution applications at voltages less than 1000 volts. The connectors were standard single screw lug connectors obtained from local suppliers. These wire and connector samples were subjected to accelerated ageing by current cycling using the test procedures outlined in IEC 61238-1 as a guide.

The testing included 1500 current cycles applied through the wires and across the connectors. The DC resistance and peak temperature of each sample were measured during the testing. Temperatures in the connections typically climbed from room temperature to 100 degrees Celsius above the ambient.

Additionally, tests were performed with different levels of torque applied to the connector screw, with the screw tightened to 70 percent, 100 percent and 125 percent of the rated torque. Measurements were made with aluminum alloy samples prepared with and without abrasion of the conductor surfaces and with and without oxide inhibitor, as code-required installation instructions for aluminum require surface abrasion and the application of oxide inhibitor. The copper samples were not specially prepared in any manner.

The copper conductors with copper mechanical connectors performed well with no sample failures through 1500 cycles. On the other hand, 100 percent of the aluminum samples torqued to the manufacturer’s specifications failed the test. This result was irrespective of conductor preparation.

The study also found that 33 percent of the samples with copper conductors and dual rated (aluminum/copper) connectors failed testing to 1500 cycles; and 94 percent of the dual rated (aluminum/copper) connectors with aluminum wire failed or showed significantly increasing resistance and heat to 1500 cycles.

“This study bears out what we have known for a long time,” says David Brender, National Program Manager for the Copper Development Association (CDA).  “For power distribution applications, copper conductors with copper connectors provide the safest and most reliable performance. Aluminum wiring systems, even properly prepared and properly torqued, largely failed the test.”

Testing was carried out at the request of the International Copper Association by PowerTech Labs, Surrey, B.C., Canada in 2013 and 2014. 

The complete Powertech Labs Inc. report titled “Connectability Testing of North American and Chinese Copper and Aluminum Wiring” is available from the Copper Development Association (Report # PL-00236-REP1, 27 June 2014).

For more information, visit CDA’s Electrical Applications section.

About The International Copper Association

The International Copper Association (ICA) increases awareness and usage of copper by communicating the unique attributes that make this sustainable element an essential contributor to the formation of life, to advances in science and technology, and to a higher standard of living throughout the world. The ICA's 43 members represent a majority of the world's refined copper output and are among the largest copper producers, fabricators, and wire and cable companies.  For more information, visit