Battery Equivalents and Replacements

500 kcmil (MCM) Copper and Aluminum Wire

The 500 kcmil (MCM) wire is a prevalent choice for a variety of commercial and industrial applications due to its large Ampacity and wire size.

The term "kcmil" stands for "thousand circular mils," while "MCM" is an abbreviation for "thousand circular mil area." Both terms refer to the same wire size and cross-sectional area, and they are commonly used interchangeably.

Published: May 5, 2023.

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500 kcmil (MCM) Wire Diameter and Cross Section Area

The 500 kcmil (MCM) wire boasts a diameter of approximately 0.707 inches or 17.96 millimeters. Its circular cross-sectional area measures 500000 circular mils, shortened to 500 kcmil, which equates to approximately 253.4 square millimeters.

These dimensions make it suitable for high-power applications where the ability to efficiently conduct electricity is crucial.

Copper and aluminum are the most popular materials for 500 kcmil wire construction. The choice between these materials often depends on the specific project requirements, budget, and other factors. Copper, known for its superior conductivity, is more expensive, while aluminum offers a lighter and more cost-effective option.

500 kcmil/MCM Copper and Aluminum Wire Ampacity

The ampacity of a 500 kcmil wire, whether copper or aluminum, is a critical factor to consider when selecting the appropriate wire for the required application.

Note: Ampacity refers to the maximum amount of electrical current that a conductor can safely carry without overheating or causing damage to the insulation. Copper and aluminum wires have different ampacities due to their distinct electrical and thermal properties. Also, it is not the same if the wires are enclosed or free in the air.

For copper 500 kcmil wire, the ampacity typically ranges from 380 to 430 amperes, depending on the insulation type and temperature rating.

Conversely, the ampacity of aluminum 500 kcmil wire is generally lower, ranging from 310 to 345 amperes. It is essential to consider these differences when designing electrical systems to ensure adequate performance and safety.

The following chart lists the Ampacities of enclosed copper and aluminum 500 kcmil wires:

Copper Wire Ampacity (A) Aluminum Wire Ampacity (A)
@60°C/140°F @75°C/167°F @90°C/194°F @60°C/140°F @75°C/167°F @90°C/194°F
Enclosed/Insulated Wire 320 380 430 260 310 350
Wire Free In Air 515 620 700 405 485 545

When installing 500 kcmil wire in an open-air environment, the wire's ampacity differs from its rating in an enclosed space.

The ambient temperature, proximity to other conductors, and the presence of other heat sources can all impact the wire's ampacity. Consequently, it is crucial to evaluate these factors during the design and installation process.

For instance, a 500 kcmil copper wire with an ambient temperature of 30°C may have an ampacity of 430 amperes (with a maximum allowed temperature of 90°C/194°F).

However, this value may decrease if the ambient temperature rises or if the wire is bundled with other conductors. Similarly, the ampacity of a 500 kcmil aluminum wire in the open air will also be influenced by the surrounding conditions. Consulting the National Electrical Code (NEC) or other relevant guidelines can help ensure safe and efficient wire installation in open-air environments.

Note: The values in the chart above are the maximum allowed Ampacities without having any safety margin.

The 80% Rule

The so-called "80% Rule" decreases the theoretical Ampacity of the wire down to 80% - this ensures that the wire doesn't get too hot, even if pushed to its 80% Rule limit. Thus, after applying the 80% Rule, we get the following:

Copper Wire Ampacity (A) Aluminum Wire Ampacity (A)
@60°C/140°F @75°C/167°F @90°C/194°F @60°C/140°F @75°C/167°F @90°C/194°F
Enclosed/Insulated Wire 256 304 344 208 248 280
Wire Free In Air 412 496 560 324 388 436

This rule is very important, especially for aluminum wires - aluminum melts at 660°C/1220°F, but it loses its strength rapidly above 120-130°C/248-266°F.

Wire Length

The 80% Rule doesn't take into account wire length, and it is generally used for shorter wires, usually up to 50 feet (~15m).

To keep the energy losses to acceptable levels, the actual Ampacity of wires is decreased by 10% for every 50 feet of wire.

For example, if we want to calculate the actual Ampacity of the 100 feet long enclosed copper wire with a maximum temperature of 60°C/140°F, we would use the following formula:

Ampacity (A) = 320A * 0.8 / 1.2 = ~213.3 Amps

Similarly, one can calculate Ampacities for different types of wires at different lengths and with different maximum surface temperatures.

500 kcmil/MCM Wire Weight

Understanding the weight of 500 kcmil wire is essential for various reasons, including transportation, storage, and installation.

The weight of a wire is typically measured in pounds per 1,000 feet (lbs/1,000 ft) or kilograms per kilometer (kg/km). The wire's material is a primary factor in determining its weight, with copper being significantly heavier than aluminum.

A 500 kcmil bare copper wire weighs approximately 1550 lbs/1,000 ft (~2300 kg/km) and with insulation up to 1650 lbs/1000 ft (~2450 kg/km).

An equivalent insulated aluminum wire weighs up to 540-560 lbs/1000 ft (~800-830 kg/km).

This weight disparity is a critical consideration when selecting the appropriate wire for a project, as it may impact factors such as installation costs, structural support requirements, and overall system design.

Lightweight aluminum wires may be preferred in situations where weight reduction is crucial, while copper wires might be chosen for their higher conductivity despite their increased weight.

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500 kcmil Wire Price

500 kcmil wires are anything but cheap - their price depends on the wire type, wire material, construction (number of strands), insulation quality, etc.

Also, it is not the same if You purchase just a few feet of these wires or hundreds or even thousands of meters of 500 kcmil wire.

Few Final Words

500 kcmil (MCM) copper and aluminum wires are versatile and robust conductors suitable for a variety of high-power applications.

When selecting the appropriate wire for a project, it is essential to consider factors such as diameter, cross-sectional area, ampacity, weight, and the specific requirements of the application. Copper and aluminum each have unique properties, with copper offering higher conductivity while aluminum provides a lightweight and cost-effective alternative.

Understanding the differences between copper and aluminum 500 kcmil wires, their ampacity in various environments, and the impact of weight on installation and system design is crucial for making informed decisions.