The ground wire that runs with your circuit (the equipment grounding conductor, or EGC) is primarily sized by your breaker rating, with some exceptions such as voltage-drop adjustments. A 20-amp breaker needs a #12 AWG copper EGC. A 200-amp feeder. The National Electrical Code (NEC) provides clear guidelines for ground wire sizing through Table 250. 122, but understanding how to apply these requirements correctly can make the difference between a safe installation and a costly code violation. Proper grounding conductor sizing is critical for. What is the NEC rule that specifies the size of the equipment ground conductor on the secondary side of a transformer to the panel? Not open for further replies. This would logically be the size required. You said ground wire size which is too generic to find it in the NEC. It ensures safe fault current paths, compliance with NEC codes, and reliable protection for residential, commercial, and industrial installations.
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