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Electrical Metallic Tubing (EMT)

EMT is thin-wall, unthreaded steel or aluminum raceway joined with set-screw or compression fittings. It is the most common conduit for exposed and concealed branch circuits indoors.

Ref EL-0020NEC 358UL 797ANSI C80.3

Draft, open for review. Check every value against the governing standard and the manufacturer’s data before use.

What it is

Electrical metallic tubing (EMT) is a thin-wall metal raceway. It is too thin to thread, so it is joined with couplings and connectors that grip the outside of the tube. Most EMT is galvanized steel. Aluminum and stainless versions are also made. EMT is covered by NEC Article 358, listed to UL 797 and made to the dimensions in ANSI C80.3. It is sold by trade size, and the NEC limits its use to trade sizes 1/2 through 4.

How to identify

EMT has a smooth, bright or galvanized finish and no threads on the ends. Each 10 ft length is marked with the maker, trade size and listing. It is clearly lighter and thinner than rigid or IMC. Some EMT has a colored finish (red, blue and others) used to tell systems apart; color is not a rating. See the how to identify conduit types sheet.

Fitting types

Fitting type	How it grips	Typical use	Notes
Set-screw	Screw bites the tube	Dry, indoor locations	Most common and lowest cost
Compression	Nut squeezes a ring onto the tube	Wet locations when listed raintight	Check the raintight marking
Concrete-tight	Set-screw or compression listed for concrete	Embedded in concrete	Must be marked concrete-tight
Indenter	Tool crimps tube and fitting	Older and specialty work	Less common today
Transition fittings	Adapt EMT to rigid, flex or boxes	Changes of raceway type	Use listed combination fittings

Key points

EMT is not threaded. Use fittings listed for EMT.
Supports and securing intervals, bend limits and permitted locations are in Article 358. Bends between pull points may not total more than 360°.
Listed EMT and fittings can serve as an equipment grounding conductor under NEC 250.118, if the fittings are made up tight. Many specs still call for a separate wire grounding conductor.
Wet locations need fittings listed for wet locations. Outdoors, compression fittings are typical.
Corrosion protection matters in soil, concrete slabs on grade and severe environments. Check 358.10 and the maker's guidance.
Conductor fill is from NEC Chapter 9 tables. See the conduit trade size chart.

Common mistakes

Using indoor set-screw fittings outdoors or in wet locations.
Loose set screws that break the grounding path.
Using EMT where severe physical damage is expected, where heavier raceway is required.
Mixing EMT and rigid fittings without a listed transition.

Governing standards: NEC Article 358 (EMT); NEC 250.118 (grounding); UL 797 (EMT, steel); ANSI C80.3 (steel EMT dimensions); UL 514B (fittings).

Reference only. Verify against the current governing code or standard, the manufacturer's data and the project documents before use. Apps for Distributors disclaims liability arising from reliance on this reference.

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