Sizing Free - Copper Cable

Real-world example: A 15A pump, 200 feet from the panel on 120V. Using 14 AWG (common for 15A) gives a 7.2% voltage drop. That pump will fail. You must jump to 10 AWG to drop to 2.8%. Myth 1: "Copper is copper." False. Pure copper (Cu-ETP) is standard. CCA (Copper-Clad Aluminum) is not copper; it requires a 2-step larger size. And "tinned copper" is for marine/corrosive environments but has identical ampacity.

| AWG/kcmil | Ampacity (75°C) | Typical Use | Max distance for 15A @ 120V (<3% drop) | | :--- | :--- | :--- | :--- | | 14 | 20A | Lighting, general outlets | 30 ft | | 12 | 25A | Kitchen outlets, 20A circuits | 40 ft | | 10 | 35A | Water heaters, AC units | 65 ft | | 8 | 50A | Small subpanels, ranges | 80 ft | | 6 | 65A | EV chargers, large ovens | 100 ft | | 4 | 85A | Subpanels, feeders | 130 ft | | 2 | 115A | Main feeders, heat pumps | N/A (requires calc) | copper cable sizing

Note: Always verify with local codes and actual installation conditions. Real-world example: A 15A pump, 200 feet from

The best electricians don't just read ampacity tables; they understand why the table says what it does. They account for the heat, the distance, and the neighbors in the conduit. You must jump to 10 AWG to drop to 2