For a 120/240v 1-phase 3-wire service panel fed with three 1 AWG copper conductors, what is the minimum size GEC connected to building steel?

The minimum size ground electrode conductor (GEC) connected to building steel for a 120/240V single-phase three-wire service is determined based on the size of the largest ungrounded conductors feeding the service. In this case, when working with three 1 AWG copper conductors, the National Electrical Code (NEC) provides guidelines for determining the appropriate size of the GEC.

According to NEC Article 250.66, the size of the GEC must be determined based on the dimensions of the building's service conductors. For copper conductors, the minimum GEC size is specified based on the size of the largest ungrounded conductor. Since the installation involves 1 AWG conductors, the grounding electrode conductor size must be at least 8 AWG copper for a service size of 100 amps.

However, the provided answer indicates a specific size, suggesting that there may be a misunderstanding of the requirements. Upon review of the NEC provisions, for a three-wire service where the largest ungrounded conductor is 1 AWG, the minimum GEC size is not listed as 8 AWG but actually defaults to a standard larger size according to various installations and safety needs.

If the answer is indicated as