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Copper & Building WiresCopper cables provide guaranteed performancewhen compared with copper-clad aluminum cables

Copper-clad aluminum cable is a composite wire with analuminum core covered by a thin copper coating. There areseveral variations of the wire with respect to the volumepercentage of copper cladding. However, majority of thesewires would have 10% or 15% copper by volume with referenceto ASTM B-566 (2004).

Shortcomings presented by copper cladaluminum cables

Compared to pure copper cables, copper-clad aluminum cablesare incomparable in performance and quality assurance in bothshort and long runs.

Copper-clad aluminum disadvantages come from thoseinherent characteristics of aluminum such as creep, brittleness,and higher resistance. With majority of the cable compositionstill aluminum, creep takes its toll on connections wherein gapsmay form due to the expansion and contraction of the wire.

There could be flaw in the manufacture of the wire in terms of its concentricity and uniformity of the copper clad thickness.Also, wire breaking typically happens during manufacturingdue to its brittleness. Thus, care should be taken duringinstallation to avoid breaking the wire during pulling, bending,termination and connection.

Lesser conductor strands means lesser current capacity. Highresistance of copper-clad aluminum would mean higher lossand more heating compared to the same copper wire size.

A) Technical Assessment

• Wire Ampacity

With reference to the Philippine Electrical Code Part 1,the ampacity of copper-clad aluminum wire is equivalentto that of an aluminum wire. Thus, its equivalent copperwire is one metric size lower (or in American Wire Gauge,it would be two gauges lower). Let’s take for exampletypical home wirings of not more than three current-carrying conductors in a raceway for THHN/THWNinsulated wires rated at 90°C:

• Termination and Connection CompatibilityBeing the available conductor during the start of theelectric industry, copper enjoys the privilege of being

Copper Aluminum

Wire Size Ampacity

Metric, mm2 AWG No. Copper Aluminum

2 14 25 -*

3.5 12 30 25

5.5 10 40 35

8 8 55 45* Minimum wire size for aluminum orcopper-clad aluminum wire is 2 mm indiameter or 3.5 mm2 cross-sectional area.

Conductor Characteristics Copper CCA-10% Aluminum

Specific gravity 8.91 3.32 2.71

Resistivity, µohm-cm 1.724 2.673 2.79

Conductivity, IACS % 100 63 61

Weight in Percentage of Copper 100 27 -

 Volume in Percentage of Copper 100 10 -

Tensile, kg/sq.mm -hard 45.7 30 27

Tensile, kg/sq.mm -soft 35 17 17

Coefficient of thermal expansion (20 -100ºC), µm/m- ºK

16.8 22.9 24

Specific Heat, cal/g-ºC 0.092 0.181 0.214

Latent Heat, cal/g 48.9 82.1 95.4

Properties of copper-clad aluminum - physical and electrical characteristic of copper-clad aluminumin comparison with copper and aluminum are as follows:

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Understanding copper-clad aluminum

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the standard. Connectors and terminations are designed based on thecharacteristics of copper. Thus, when aluminum wires were used inthe US in 1960’s and 1970’s, it caused problems on the connections

and terminations that started many fires.

Terminations such as those for outlets and switches should bemarked CO/ALR, which means that such device has complied with thestringent heat-cycling requirements for suitability in their use withaluminum, copper and copper-clad aluminum wires. However, locallyavailable convenience outlets and switches have no CO/ALR markingson them and most are designed purely for copper conductors

• CorrosionThe bonding of copper and aluminum creates a condition wheregalvanic corrosion could occur. The copper coating could corrodethe aluminum core due to the harsh Philippine environment withhigh humidity and presence of salt contaminations. Some terminalconnecting means could damage the copper coating and expose thealuminum core. This portion then would corrode and increase contact

resistance to some degree where it could cause electrical fire.

B) Environmental Assessment

Copper is a 100% recyclable material. It can be recycled over and over againwithout losing its chemical or physical properties. It is this recyclabilitythat we are able to preserve this precious metal. Copper-clad aluminumhampers the effective recycling of copper due to the following reasons:

• Difficulty in Retrieval of Copper-clad aluminumMixed with copper wires, it is difficult to distinguish copper-cladaluminum since it has the same appearance as that of pure copperwires. For bus bars and large diameter copper-clad aluminum wiresit may be distinguished by looking at the cross sections. However,for thin copper-clad aluminum wires having same appearance with

copper-clad steel and pure copper wires, it will be extremely difficultand impractical to sort them out manually. Unlike copper-clad steelwhich can be separated by magnetic separation, there is no means of automatically separating copper-clad aluminum.

• Separation of the Two Metals in Copper-clad aluminumThe outer coating of copper-clad aluminum wire cannot be easilystripped away from its aluminum core. At present, the copper andaluminum content in copper-clad aluminum cannot be separatedthoroughly by fire refining due to their affinity. Also, there is nodeveloped hydrometallurgical refining technology to completelyseparate the two metals.

• Contamination in Scrap Copper RefiningCopper-clad aluminum waste wires can create huge losses to scrap

copper recycling and refining business since the aluminum contentof copper-clad aluminum could contaminate a batch of clean copperwire scraps resulting in a substandard production. Purity of therecycled batch will result to lower value.

C) Economic Assessment

• Initial savings may be realized with the use of Copper-clad aluminum.

However, one must look not only on the first cost, but on the wholelife cycle cost.

• Copper-clad aluminum, having higher resistance, would meanadditional line losses which would negate the initial savings in thelong run. Example: A 50 meter length of 3.5 mm2 Copper-cladaluminum wire when load 80% of its ampacity would result to anadditional line losses of about 0.95 kwhr/month at 60% utilizationwhen compared to the same sized copper wire. At Php 10/kwhr costof electricity, it negates your savings in less than four years.

• Copper-clad aluminum has little or no salvage value.

Conclusion

Copper-clad aluminum is an aluminum conductor coated with copper toimprove corrosion resistance and connection compatibility. Despite this, itstill retains most of aluminum’s weakness such as brittleness, creep, andlower conductivity and strength than copper.

During times when costs of basic materials become extremely high, itis natural to look for alternatives. Interest in the possible utilization of copper-clad aluminum takes stage when copper prices are high and suchinterest wanes when copper price drops. This type of cladded conductor isnot new; however, in the past 40 years of its presence, there’s no tendencyto increase the application of copper-clad aluminum over the years.

Moreover, there’s insufficient experimental data to prove the reliabilityof copper-clad aluminum, especially the connection problem duringapplication.

Copper-clad aluminum has found its application as a conductor takingadvantage of the skin effect only.

For utilization of copper-clad aluminum as building wires, the local marketfor the utilization of copper-clad aluminum is not ready. This is becausemost of the available electrical outlets and sockets in the market aredesigned for compatibility with copper conductors only. Cost of electricaloutlets and sockets with “CO/ALR” are relatively higher, easily cancelinginitial savings with copper-clad aluminum wires. Its higher resistance alsoincreases electricity cost due to unnecessary additional line losses..

Environmentally, copper-clad aluminum can create problems in the futureconcerning the effective recycling of copper unless advance methods of separating copper and aluminum can be developed.