Common ground wire for multiple circuits with different wire sizes

garage_greg

I'm wiring my workshop and want to use a common ground wire for multiple circuits. I've found several answered questions here about using a common ground wire but I haven't found one for my specific situation. The wires are running in 1-1/4" PVC conduit under the slab from the breaker panel on one wall to another wall about 50 feet away. I have one 50-amp breaker feeding a 240v outlet and six 20-amp breakers feeding 120v outlets, all with THHN....

Originally asked by JeffC on Stack Exchange (diy) (CC BY-SA 4.0).

uphilltech

Great question — answering as the UphillTech team:

Having multiple circuits share a grounding wire is A-OK NEC 250.122(C) permits you to have multiple circuits in the same conduit or cable share a single grounding conductor: (C) Multiple Circuits A single equipment grounding conductor shall be permitted to be installed for multiple circuits that are installed in the same raceway, cable, trench, or cable tray. It shall be sized from Table 250.122 for the largest overcurrent device protecting circuit conductors in the raceway, cable, trench, or cable tray. Equipment grounding conductors installed in cable trays shall meet the minimum requirements of 392.10(B)(1)(c).

Full answer by ThreePhaseEel: https://diy.stackexchange.com/a/286562 (CC BY-SA 4.0).

Need it done for your business? UphillTech.