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Ensuring the safety and efficiency of an electrical installation requires the proper application of amperage to the conductor. Amperage is the maximum current that a conductor can safely carry, and its effect depends on the specifics of the conductor material, insulation type, temperature rating, and installation environment. This blog presents charts of the ampacity of copper, aluminum, and copper-clad aluminum conductors under standard conditions (ambient temperature of 30°C/86°F), highlighting key factors for proper use.
1. Copper Conductors
Copper conductors are popular because of their excellent electrical conductivity and thermal properties. The following table lists the amperage of copper conductors at three temperature ratings:
| AWG Size | 60°C (140°F) | 75°C (167°F) | 90°C (194°F) |
|---|---|---|---|
| 14 | 20 A | 25 A | 30 A |
| 12 | 25 A | 30 A | 35 A |
| 10 | 30 A | 35 A | 40 A |
| 8 | 40 A | 50 A | 60 A |
| 6 | 55 A | 65 A | 75 A |
| 4 | 70 A | 85 A | 95 A |
| 3 | 85 A | 100 A | 110 A |
| 2 | 95 A | 115 A | 130 A |
| 1 | 110 A | 130 A | 150 A |
| 1/0 | 125 A | 150 A | 170 A |
| 2/0 | 145 A | 175 A | 195 A |
| 3/0 | 165 A | 200 A | 225 A |
| 4/0 | 195 A | 230 A | 260 A |
| 250 | 215 A | 255 A | 290 A |
| 300 | 240 A | 285 A | 320 A |
| 350 | 260 A | 310 A | 350 A |
| 400 | 280 A | 335 A | 380 A |
| 500 | 320 A | 380 A | 430 A |
| 600 | 355 A | 420 A | 475 A |
| 700 | 385 A | 460 A | 520 A |
| 750 | 400 A | 475 A | 535 A |
| 800 | 410 A | 490 A | 555 A |
| 900 | 435 A | 520 A | 585 A |
| 1000 | 455 A | 545 A | 615 A |
2. Aluminum Conductors
Aluminum conductors are generally less expensive and lighter in weight, and are therefore widely used; however, their amperage values are typically lower than those of copper conductors. The chart below reflects the amperage of aluminum conductors:
| AWG Size | 60°C (140°F) | 75°C (167°F) | 90°C (194°F) |
|---|---|---|---|
| 14 | 15 A | 20 A | 25 A |
| 12 | 20 A | 25 A | 30 A |
| 10 | 25 A | 30 A | 35 A |
| 8 | 35 A | 45 A | 50 A |
| 6 | 40 A | 50 A | 60 A |
| 4 | 55 A | 65 A | 75 A |
| 3 | 65 A | 75 A | 85 A |
| 2 | 75 A | 90 A | 100 A |
| 1 | 85 A | 100 A | 115 A |
| 1/0 | 100 A | 115 A | 130 A |
| 2/0 | 115 A | 135 A | 150 A |
| 3/0 | 130 A | 155 A | 175 A |
| 4/0 | 150 A | 180 A | 205 A |
| 250 | 170 A | 200 A | 225 A |
| 300 | 190 A | 225 A | 255 A |
| 350 | 210 A | 245 A | 275 A |
| 400 | 225 A | 265 A | 300 A |
| 500 | 250 A | 300 A | 335 A |
| 600 | 275 A | 325 A | 365 A |
| 700 | 300 A | 355 A | 400 A |
| 750 | 310 A | 365 A | 410 A |
| 800 | 320 A | 375 A | 420 A |
| 900 | 340 A | 395 A | 440 A |
| 1000 | 360 A | 415 A | 460 A |
3. Copper-Clad Aluminum (CCA) Conductors
Copper-clad aluminum conductors, like aluminum conductors, are lighter and less expensive than copper conductors, but add a thin layer of copper to these advantages to provide a better connection. Overcurrent protection ratings may be lower than those of other materials due to material properties and terminal temperature limitations. For example, 12 AWG CCA conductors used in non-metallic (NM) cable applications are typically limited to 15 A circuit breakers, although theoretical amperage tables may be higher. The following is a reference for CCA wire amperage:
| AWG Size | 60°C (140°F) | 75°C (167°F) | 90°C (194°F) |
|---|---|---|---|
| 12 | 20 A | 20 A | 25 A |
| 10 | 25 A | 30 A | 35 A |
| 8 | 30 A | 40 A | 45 A |
| 6 | 40 A | 50 A | 55 A |
| 4 | 55 A | 65 A | 75 A |
| 3 | 65 A | 75 A | 85 A |
| 2 | 75 A | 90 A | 100 A |
| 1 | 85 A | 100 A | 115 A |
| 1/0 | 100 A | 115 A | 130 A |
| 2/0 | 115 A | 135 A | 150 A |
| 3/0 | 130 A | 155 A | 175 A |
| 4/0 | 150 A | 180 A | 205 A |
Note: Although the theoretical ampacity charts for a 12 AWG CCA conductor may be as listed above, NEC guidelines often restrict its overcurrent protection to 15 A in specific applications (e.g., NM cables) to ensure safe, long-term operation.
Key Considerations
- Ambient Temperature: The amperage values shown are based on an ambient temperature of 30°C (86°F). A correction factor must be applied according to the NE if the actual temperature differs from the stated temperature.
- Installation Conditions: Mounting conditions affect heat dissipation (e.g., conduit, bundling, direct burial). In all cases, a derating factor must be considered based on the installation conditions.
- Compliance with Standards: When designing an electrical system, always refer to your local electrical code (e.g., the National Electrical Code, or NEC) and verify the manufacturer’s specifications. The appropriate overcurrent protection ratings should be followed in any application (e.g., NM cable installations).
- Application Examples:
- Residential Wiring: Copper conductors are typically preferred in residential applications due to their higher current-carrying capacity and reliability.
- Utility or Large-Scale Installations: Aluminum conductors are sometimes used in utility or large-scale applications where weight and cost are factors to be considered, as long as the ratings are appropriately reduced.
- Cost-Sensitive Projects: Copper-clad aluminum conductors are more cost-effective, but must be used in compliance with the National Electrical Code’s (NEC) safe operating limits.
Conclusion
Selecting the proper conductor type and size is crucial in evaluating the safety and performance of an electrical system. Selecting copper, aluminum, or copper-clad aluminum conductors requires considering material properties, temperature ratings, insulation, and installation conditions. Always consult local codes and take advice from a licensed electrical professional when making design decisions regarding safety and performance.
Sam Wu is the Marketing Manager at Romtronic, holding a degree in Mechatronics. With 12 years of experience in sales within the electronic wiring harness industry, he manages marketing efforts across Europe. An expert in cable assembly, wiring harnesses, and advanced connectivity solutions, Sam simplifies complex technologies, offering clear, actionable advice to help you confidently navigate your electrical projects.
