When conductors run underground in nonmetallic raceways, how can they be arranged according to the NEC?

The correct choice is based on the NEC's provisions regarding the arrangement of conductors in nonmetallic raceways. When conductors are run underground in nonmetallic raceways, they must be installed in a manner that limits the possibility of overheating and ensures that their performance and safety are maintained.

Isolated phase installations refer to a configuration where conductors are separated from one another, minimizing the interaction between their magnetic fields, which can produce induced currents and potentially lead to overheating. This arrangement is particularly important in underground applications where heat dissipation is more challenging due to the insulation properties of nonmetallic raceways and the surrounding soil.

This approach ensures that each conductor can operate efficiently without being affected by the others, balancing current distribution and reducing risks associated with overloading. Additionally, it adheres to the NEC’s safety requirements to prevent potential hazards.

The other types of installations, while they have their own significance, do not fit the specific guidelines for underground installations in nonmetallic raceways as effectively as isolated phase installations. Understanding this specific setup is critical for maintaining both the safety and the reliability of the electrical system.