Should spare or unused raceways be sealed where they enter a building?

Sealing spare or unused raceways where they enter a building is important primarily to prevent moisture intrusion. Allowing moisture to enter through these raceways can lead to a range of issues, including corrosion of wiring and connectors, mold growth, and potential damage to building materials. By sealing these openings, you are effectively minimizing the risk of water damage and maintaining a dry environment within the structure.

Additionally, ensuring that raceways are properly sealed can enhance the overall energy efficiency of the building by preventing drafts that could impact heating and cooling systems. This practice aligns with safety standards outlined in the NEC, which emphasizes the importance of protecting electrical installations from environmental factors that may compromise their integrity.