Article 360

Flexible Metallic Tubing: Type FMT

Part I. General

1. Scope. This article covers the use, installation, and construction specifications for flexible metallic tubing (FMT) and associated fittings.
2. Definition.

Flexible Metallic Tubing (FMT). A metal raceway that is circu‐ lar in cross section, flexible, and liquidtight without a nonme‐ tallic jacket.

360.6 Listing Requirements. FMT and associated fittings shall be listed.

Part II. Installation

360.10 Uses Permitted. FMT shall be permitted to be used for branch circuits as follows:

1. In dry locations
2. Where concealed

360.12 Uses Not Permitted. FMT shall not be used as follows:

1. In hoistways
2. In storage battery rooms
3. In hazardous (classified) locations unless otherwise permitted under other articles in this Code
4. Underground for direct earth burial, or embedded in poured concrete or aggregate
5. Where subject to physical damage
6. In lengths over 1.8 m (6 ft)

360.20 Size.

1. Minimum. FMT smaller than metric designator 16 (trade size 1∕2) shall not be used.Exception No. 1: FMT of metric designator 12 (trade size 3∕8) shall be permitted to be installed in accordance with 300.22(B) and (C).Exception No. 2: FMT of metric designator 12 (trade size 3∕8) shall be permitted in lengths not in excess of 1.8 m (6 ft) as part of a listed assembly or for luminaires. See 410.117(C).
2. Maximum. The maximum size of FMT shall be metric designator 21 (trade size 3∕4).

Informational Note: See 300.1(C) for the metric designators and trade sizes. These are for identification purposes only and do not relate to actual dimensions.

360.22 Number of Conductors.

1. FMT — Metric Designators 16 and 21 (Trade Sizes 1∕2 and 3∕4). The number of conductors in metric designators 16 (trade size 1∕2) and 21 (trade size 3∕4) shall not exceed that permitted by the percentage fill specified in Table 1, Chapter 9.Cables shall be permitted to be installed where such use is not prohibited by the respective cable articles. The number of cables shall not exceed the allowable percentage fill specified in Table 1, Chapter 9.
2. FMT — Metric Designator 12 (Trade Size 3∕8). The number of conductors in metric designator 12 (trade size 3∕8) shall not exceed that permitted in Table 348.22.

360.24 Bends.

1. Infrequent Flexing Use. When FMT is infrequently flexed in service after installation, the radii of bends measured to the inside of the bend shall not be less than specified in Table 360.24(A).
2. Fixed Bends. Where FMT is bent for installation purposes and is not flexed or bent as required by use after installation, the radii of bends measured to the inside of the bend shall not be less than specified in Table 360.24(B).

360.56 Splices and Taps. Splices and taps shall be made in accordance with 300.15.

Table 360.24(A) Minimum Radii for Flexing Use

Minimum Radii

(4) For system voltages of 1000 volts maximum	Designator	Trade Size	mm	in.
	12	3∕8	254.0	10
	16	1∕2	317.5	121∕2
	21	3∕4	444.5	171∕2

(3) In accessible locations

Metric

for Flexing Use

360.60 ARTICLE 362 — ELECTRICAL NONMETALLIC TUBING: TYPE ENT

Table 360.24(B) Minimum Radii for Fixed Bends

Minimum Radii

tified in listings of fire-rated assemblies. The 15-minute- finish-rated thermal barrier shall be permitted to be used for combustible or noncombustible walls, floors, and ceil‐

Metric

for Fixed Bends

ings.

Designator	Trade Size	mm	in.
12	3∕8	88.9	31∕2
16	1∕2	101.6	4
21	3∕4	127.0	5

Exception to (2): Where a fire sprinkler system(s) is installed in accordance with NFPA 13-2013, Standard for the Installation of Sprinkler Systems, on all floors, ENT shall be permitted to be used within walls, floors, and ceilings, exposed or concealed, in build‐ ings exceeding three floors abovegrade.

Informational Note: A finish rating is established for

360.60 Grounding. FMT shall be permitted as an equipment grounding conductor where installed in accordance with 250.118(7).

Part III. Construction Specifications

360.120 Marking. FMT shall be marked according to 110.21.