In a service conduit containing three 4/0 AWG conductors, what is the smallest GEC that can be installed to building steel?

When determining the minimum grounding electrode conductor (GEC) size required for a conduit containing three 4/0 AWG conductors connected to building steel, the National Electrical Code (NEC) provides guidance. The GEC should be sized based on the size of the largest ungrounded conductors supplying the service.

In this case, the largest conductors are 4/0 AWG. According to the NEC Table for Grounding Electrode Conductor Sizes, the minimum size for the GEC connected to building steel when the largest ungrounded conductor is 4/0 AWG is 2 AWG copper.

This minimum size is critical for ensuring the safety and effectiveness of grounding, as it helps maintain system integrity and provides adequate fault protection and equipment safety. Thus, specifying a GEC that is too small could compromise the grounding system's effectiveness, making option listing 2 AWG the correct response.