Differences in size and weight of equipment using copper and aluminium conductors

Common misconception

It is a common misconception that electrical equipment built using aluminum conductors will always be larger than the same equipment using copper conductors. While the actual conductor within the equipment will be larger with aluminum, many times the enclosure for the equipment is the same size whether copper or aluminum conductors are used.

This is true for switchboards, panelboards and most dry type transformers. Oil filled transformers will generally range from 2-5% larger when constructed with aluminum instead of copper windings.

The biggest size impact for electrical equipment when copper and aluminum conductors are considered is for busway. Since the actual conductor is the primary component within the busway, the size difference will be more apparent.

For example, GE busway is 4.5” thick, but the width will vary. For 1000A busway, the aluminum bus will be approximately 22% larger than copper bus and for 4000A busway, the size difference increases to almost 27% larger for the aluminum.

Even though the size for the aluminum bus is larger than for the copper bus, the weight difference is more dramatic and favors the aluminum bus.

Using the same examples used for size and assuming 3 phase, 4 wire busway, the 1000A copper is 50% heavier than the aluminum and for the 4000A busway, this value increases where copper is 73% heavier than the aluminum. This weight differential can be a huge factor for both the designer and the installer.

The weight difference between equipment items with aluminum or copper conductors is present with all of the equipment types. For switchboards, the actual percentage will vary significantly with the amount of breakers installed in a section; and with a higher count of breakers, the percentage of weight contributed by the busbars diminishes.

However, if you just consider the weight of the steel enclosure and the busbars, copper bussed switchboard sections will be heavier than aluminum bussed switchboard sections, varying between 20% for 1000A sections to 29% for 4000A sections.

Dry type transformers like switchboards do not typically have a physical size difference between copper and aluminum units, but they like switchboards, have significant weight differences. These differences will vary from 18% for a 45kVA unit to 22% for a 75kVA unit.

This translates to a copper wound 75kVA transformer weighing 130 pounds more than the corresponding aluminum wound transformer.

When considering the differences between copper and aluminum conductors in electrical equipment, size must be acknowledged, but for most equipment types the size is not a delineating feature. The weight of the equipment is generally not apparent, but can be big difference in terms of labor and material for the installation and support of the equipment.

More about Al/Cu comparison…

• Copper or aluminium? Which one to use and when?
• Aluminum vs. Copper: Conductors in Low Voltage Dry Type Transformers
• Aluminium or copper busbar trunking? Myth busted!
• Few Aspects of Copper versus Aluminium

Reference // A comarison of aluminium vs. copper as used in electrical equipment – GE, Larry Pryor, Rick Schlobohm and Bill Brownell