300.4 Protection from physical damage
What changed in 300.4
Where 4 AWG and larger conductors enter an enclosure from a raceway, a listed smooth-edged metal fitting now counts as protection, not just an insulating fitting.
Point by point
- Applies where a raceway holds 4 AWG or larger insulated conductors entering a cabinet, box, enclosure or another raceway.
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- 4 more points on exactly what changed
- The 2017 rule next to the 2020 rule, side by side
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This section across NEC® editions
2020 NEC®RevisedYou're here
Where 4 AWG and larger conductors enter an enclosure from a raceway, a listed smooth-edged metal fitting now counts as protection, not just an insulating fitting.
2023 NEC®Revised
Under metal roof decking, a new concrete exception was added and the RMC/IMC exception now depends on the fittings. Protective fittings for 4 AWG and larger go on before the pull.
Open the 2023 page →2026 NEC®Revised
Found at 300.6 in the 2026 NEC®.
The roof decking rule now covers every roof deck type and all wiring methods, and the bushing on 4 AWG and larger can go on after the pull.
Open the 2026 page →More 2020 changes in Article 300
This is a plain-English summary, not the NEC®'s exact wording. Always check the full section in the NEC® edition your area has adopted, plus any local amendments.
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