In a PVC conduit carrying three circuits: 12 AWG conductors on a 20-A breaker, 8 AWG conductors on a 50-A breaker, and 6 AWG conductors on a 60-A breaker, what is the smallest EGC permitted to be installed in the conduit?

• A. 12 AWG
• B. 8 AWG
• C. 10 AWG
• D. 6 AWG

Answer: (C)

In a conduit that carries more than one circuit, the equipment grounding conductor (EGC) has to provide a reliable grounding path for all of the circuits sharing that raceway. The EGC must be sized to handle the fault current along the path back to the source, taking into account the protection devices protecting each circuit in that run. When you have a mix of circuits with different breaker ratings, you look for the smallest conductor size that still satisfies the grounding needs for the arrangement as a whole, while not being undersized for the larger protection devices present in the run. In this scenario, the combination of circuits in the PVC conduit allows a common EGC size that is not as large as the largest single circuit would require, and the smallest EGC size that still safely accommodates grounding for the group is 10 AWG. Using a smaller size would be inadequate for the higher-ampacity circuit, and using a larger size isn’t necessary for grounding the whole assembly. Hence 10 AWG is the most appropriate choice for the smallest EGC permitted in this conduit.