NEC 2023 · Article 358
NEC Article 358 — Electrical Metallic Tubing (EMT)
The commercial workhorse raceway: where it's allowed, how many conductors it takes, and how it has to be strapped. Fill counts below assume all conductors are the same size.
THHN/THWN Conductor Fill (40% — 3 or More Conductors)
Selected counts for the most common trade sizes, per the Chapter 9, Table 1 fill limits (Annex C values). Mixed conductor sizes require the full calculation — use the conduit fill reference.
| EMT Trade Size | 14 AWG | 12 AWG | 10 AWG | 8 AWG |
|---|---|---|---|---|
| 1/2" | 12 | 9 | 5 | 3 |
| 3/4" | 22 | 16 | 10 | 6 |
| 1" | 35 | 26 | 16 | 9 |
Fill is a physical limit, not an electrical one — more than 3 current-carrying conductors triggers ampacity adjustment under 310.15(C)(1).
Uses Permitted & Not Permitted — 358.10 / 358.12
- • Permitted: exposed and concealed work; wet locations with corrosion-resistant hardware and listed raintight fittings; in concrete or direct contact with earth where protected against corrosion and judged suitable.
- • Not permitted: where subject to severe physical damage; for support of luminaires or equipment (except where the tubing is identified for it); in most corrosive/cinder-fill environments without protection.
- • No threading: EMT is never threaded — couplings and connectors only. Set-screw for dry, compression rated raintight for wet.
- • Bends — 358.26: maximum 360° of bends (four quarter bends) between pull points.
358.30 — Securing & Supporting
- • Strap within 3 ft of every box, cabinet, conduit body, or other termination.
- • Support at intervals not exceeding 10 ft along the run.
- • Up to 5 ft from a termination is allowed where structural members prevent fastening at 3 ft.
- • Unbroken lengths may be fished into concealed spaces of finished buildings without securing.
- • EMT is an equipment grounding conductor when fittings are made up tight (250.118) — every loose set-screw is a broken ground path.
Mixed conductor sizes in one run?
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