Few Aspects of Copper versus Aluminium

Conductor connections and terminations

The constructions of aluminum wire and terminals have both been revised from past years. At one time the conductor was nearly pure aluminum, now they are all much stronger 8000 series alloys, with physical characteristics similar to copper.
The wire terminations also have much more severe UL test requirements, resulting in reliable long-term connections when installed in accordance with instructions. There is a common misconception that only compression (crimp) lugs should be used with aluminum cables, but this is not true.

In the past with the use of the softer aluminum conductors, only compression connectors were suitable. However with the aluminum conductors used today and modern design and plating of mechanical pressure connectors, compression connectors are no longer required.

The terminals on molded case circuit breakers are typically plated aluminum alloy with mechanical setscrews, listed for use with either aluminum or copper conductors.

These lugs rated ALCU alleviate the need for more expensive compression connectors and the more laborious installations for these connectors.

The substitution of aluminum wire for copper always involves size and can also impact quantity. The size increase is usually one or two wire sizes.

It is more common to have compact stranding of aluminum wire than copper, which can reduce the conduit upsizing required. Even though physically larger the aluminum wire is lighter and easier to handle than the equivalent copper conductor. In
most cases the same lug can accommodate either aluminum or copper and has adequate wire range.
Any lug marked ALCU is suitable for use with either conductor. Another factor with the use of aluminum wiring for the supply or load from a piece of the electrical equipment is the size of the conduits. The use of aluminum conductors will result in either larger conductor size or more quantity of conductors. Either way, more or larger conduits will be utilized.
A design trend is always toward equipment with smaller footprints. Cost of the space in the structures housing the equipment is constantly increasing.
However in many cases there might not be physical space in the equipment for the termination of the conduits using aluminum conductors while there is adequate space for the quantity and size of the conduits for the copper conductors.

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