/4 in. taper per foot) shall be used.
FPN: See ANSI/ASME B.l.20.1-1983, Standard for Pipe Threads, General Purpose (Inch).
342.30 Securing and Supporting. IMC shall be installed as a complete system in accordance with 300.18 and shall be securely fastened in place and supported in accordance with 342.30(A) and (B), or permitted to be unsupported in accordance with 342.30(C).
(A) Securely Fastened. Each IMC shall be securely fas- tened within 900 mm (3 ft) of each outlet box, junction box, device box, cabinet, conduit body, or other conduit termination. Fastening shall be permitted to be increased to a distance of 1.5 m (5 ft) where structural members do not readily permit fastening within 900 mm (3 ft). Where approved, conduit shall not be required to be securely fastened within 900 mm (3 ft) of the service head for above-the-roof termination of a
mast.
(B) Supports. IMC shall be supported in accordance with one of the following:
(1) Conduit shall be supported at intervals not exceeding
3 m (10 ft).
(2) The distance between supports for straight runs of conduit shall be permitted in accordance with Table
344.30(B)(2), provided the conduit is made up with threaded couplings and such supports prevent transmission of stresses to termination where conduit is deflected between supports.
(3) Exposed vertical risers from industrial machinery or fixed equipment shall be permitted to be supported at intervals not exceeding 6 m (20 ft) if the conduit is made up with threaded couplings, the conduit is supported and securely fastened at the top and bottom of the riser, and no other means of intermediate support is readily available.
(4) Horizontal runs of IMC supported by openings through framing members at intervals not exceeding
3 m (10 ft) and securely fastened within 900 mm (3 ft) of termination points shall be permitted.
(C) Unsupported Raceways. Where oversized, concentric or eccentric knockouts are not encountered, Type IMC shall be permitted to be unsupported where the raceway is not more than 450 mm (18 in.) and remains in unbroken lengths (without coupling). Such raceways shall terminate in an outlet box, junction box, device box, cabinet, or other termination at each end of the raceway.
342.42 Couplings and Connectors.
(A) Threadless. Threadless couplings and connectors used with conduit shall be made tight. Where buried in masonry or concrete, they shall be the concretetight type. Where installed in wet locations, they shall comply with 314.15. Threadless couplings and connectors shall not be used on threaded conduit ends unless listed for the purpose.
(B) Running Threads. Running threads shall not be used on conduit for connection at couplings.
342.46 Bushings. Where a conduit enters a box, fitting, or other enclosure, a bushing shall be provided to protect the wire from abrasion unless the design of the box, fitting, or enclosure is such as to afford equivalent protection.
FPN: See 300.4(G) for the protection of conductors 4
AWG and larger at bushings.