Can a grounding electrode conductor be smaller than the main bonding jumper?

A grounding electrode conductor (GEC) can indeed be smaller than the main bonding jumper under specific conditions set forth by the National Electrical Code (NEC). The purpose of the grounding electrode conductor is to connect the grounding electrode system to the grounding system of the electrical installation. The sizing of the GEC is determined based on the size of the service-entrance conductors and the material used.

On the other hand, the main bonding jumper serves to connect the grounded (neutral) conductor to the ground in order to ensure an effective grounding system that helps to mitigate electrical faults and maintain safety.

The relevant codes allow for the GEC to be sized according to rules that sometimes permit smaller conductor sizes than those used for the main bonding jumper. Thus, it is permissible for the GEC to be smaller than the main bonding jumper, emphasizing the flexibility within specific applications, as long as safety standards are maintained. The other options might imply fixed sizes or conditions that do not accurately reflect the NEC's flexibility regarding conductor sizing in practical applications.