I. General
360.1 Scope. This article covers the use, installation, and construction specifications for flexible metallic tubing (FMT) and associated fittings.
360.2 Definition.
Flexible Metallic Tubing (FMT). A raceway that is circu- lar in cross section, flexible, metallic, and liquidtight without a nonmetallic jacket.
360.6 Listing Requirements. FMT and associated fittings shall be listed.
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
(3) In accessible locations
(4) For system voltages of 1000 volts maximum
360.12 Uses Not Permitted. FMT shall not be used as follows:
(B) Maximum. The maximum size of FMT shall be metric designator 21 (trade size 3A).
FPN: 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.
(A) FMT — Metric Designators 16 and 21 (Trade Sizes
Vi and 3A). The number of conductors in metric designators 16 (trade size Vi) and 21 (trade size %) 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.
(B) FMT — Metric Designator 12 (Trade Size %). The number of conductors in metric designator 12 (trade
size Vs) shall not exceed that permitted in Table
348.22.
360.24 Bends.
(A) Infrequent Flexing Use. Where FMT may be infre- quently 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).
Table 360.24(A) Minimum Radii for Flexing Use
(1) In hoistways
(2) In storage battery rooms
Metric
Designator
Trade Size Minimum Radii for Flexing Use
mm in.
(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
12 %
16 Vz
21 V4
254.0 10
317.5 12'/ 2
444.5 171/2
(6) In lengths over 1.8 m (6 ft)
360.20 Size.
(A) Minimum. FMT smaller than metric designator 16 (trade size Vi) shall not be used.
(B) 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).
Table 360.24(B) Minimum Radii for Fixed Bends
Exception No. 1: FMT of metric designator 12 (trade size
3/n) shall be permitted to be installed in accordance with
300.22(B) and (C).
Exception No. 2: FMT of metric designator 12 (trade size Vs) shall be permitted in lengths not in excess of 1.8 m (6ft) as part of a listed assembly or for luminaires. See
410.117(C).