Article 358 Electrical Metallic Tubing Type EMT

I. General





It is a thinwall listed metallic tubing, circular, with a cross-sectional area that is approved when joined together with listed fittings, for the installation of electrical conductors.


Listing Requirements


II. Installation


Uses Permitted

It can be used for both exposed and concealed work. Both ferrous and nonferrous tubing and fittings can be installed in concrete, in areas subject to severe corrosion, and in direct contact with the earth if protected against corrosion and suitable for the condition. It can be installed in wet locations if all supports, bolts, etc. are corrosion resistant or covered with corrosion resistant material.


Uses Not Permitted

It cannot be used where it will be subject to severe damage, where protected from corrosion by only enamel, in cinder concrete or cinder fill where there is permanent moisture unless there is a layer of noncinder concrete on all sides at least 50 mm (2 in.) thick or the tubing is at least 450 mm (18 in.) under the fill, to support fixtures or equipment except conduit bodies not larger than the largest trade size of the tubing, or in hazardous locations except as permitted in Sections 502.4, 503.3, and 504.20. Where possible, there should be no contact between dissimilar metals in the system.



The minimum size permitted is metric designator 16 (trade size ½) unless used for enclosing motor leads [see Section 430.145(B)]. The maximum size permitted is metric designator 103 (trade size 4).


Number of Conductors

Cannot exceed the percentage fill requirements of Table 1, Chapter 9. Cables can be used if not prohibited by cable articles. Cable cannot exceed the fill requirements of Table 1, Chapter 9.


BendsHow Made

The tubing must not be injured and the internal diameter is not reduced. Refer to Table 2, Chapter 9, for the radius of the center line of a field bend.


BendsNumber in One Run

The maximum that is permitted is not more than 360° in bends between pull points.

358.28 Reaming and Threading

Threading is not permitted except on factory-threaded integral couplings. Remove rough edges of all cuts.


Securing and Supporting

The tubing must be installed as a complete system as noted in Article 300.18. It must be fastened and supported in accordance with 358.30(A) and (B). The tubing must be fastened at intervals no longer than 3 m (10 ft.) and not more than 900 mm (3 ft.) from a box, fitting, etc. The 900 mm (3-ft.) rule may be extended to 1.5 m (5 ft.) for unbroken lengths where structural members interfere at 900 mm (3 ft.). There is an exception for concealed work. EMT in horizontal runs supported by openings through framing not more than 3 m (10 ft.) and fastened within 900 mm (3 ft.) of termination is permitted.


Couplings and Connectors

They must be tight and concrete-tight if used in concrete and comply with 314.15(A) if used in wet locations.


Splices and Taps

They are to be made in accordance with Section 300.15.



EMT is permitted as an equipment grounding conductor.

III. Construction Specifications



If an integral threaded coupling is used, threads for both the couplings and tubing must be factory made. The EMT threads and couplings can not bend the tubing at any part of the thread.



It must be clearly and durable marked at least every 3 m (10 ft.) on accordance with 110.21.

Article 90 Introduction


Wiring and Protection

Wiring Methods and Materials

Equipment for General Use

Special Occupancies

Special Equipment

Special Conditions


Annex C. Conduit and Tubing Fill Tables for Conductors and Fixture Wires of the Same Size

Annex D. Examples

Annex E. Types of Construction

Pocket Guide to the National Electrical Code 2005
Pocket Guide to the National Electrical Code(R), 2005 Edition (8th Edition)
ISBN: 0131480014
EAN: 2147483647
Year: 2004
Pages: 120 © 2008-2020.
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