Copper or aluminium: identifying cable conductor

Copper and aluminium conduct the same electricity at very different weights and prices. A lot described as 'copper' that turns out to be aluminium is a different lot at a different value, and the mistake is common because both are sold in the same sizes and both look like metal on a reel.

Three quick tests

• Look at a cut end. Copper is red-gold; aluminium is silver-white.
• Weigh a length. Aluminium is roughly a third of the weight of copper for the same circular mil area.
• Bend a strand. Aluminium is softer and tends to kink; copper work-hardens and springs back.

A magnet will not help, because neither is magnetic. What it will do is find a steel armour or a steel core, which is a different question and worth knowing about.

Where aluminium turns up in Louisiana

• Service entrance and feeder cable in commercial and industrial buildings, especially larger sizes.
• URD and underground distribution cable, where aluminium is common on utility systems.
• ACSR and AAAC overhead conductor, which is aluminium by definition.
• Some tray and feeder cable bought on price for large projects.

Copper dominates in industrial plants, in smaller sizes, in flexible cable, in welding lead and in grounding conductor. That is not a rule, but it is a useful prior when you are looking at a mixed store.

Why the distinction matters

Copper carries a much higher value per pound, so a copper lot and an aluminium lot of the same physical size are not comparable. Mixing them in one description means the copper is priced as if it were aluminium, which is the single most expensive paperwork mistake in this trade.