Rigid
Steel Conduit — (RSC)
The
installation of Rigid Steel Conduit (RSC) is covered by Article 344 of the
National Electrical Code® (NEC®). This article is entitled "Rigid
Metal Conduit (RMC) and includes all requirements for all rigid metal conduits,
including steel, stainless steel, aluminum, and red brass. Information on
this STI website covers only rigid steel conduit. You will often see
the following acronyms used: RSC (Rigid Steel Conduit), ERSC (Electrical Rigid
Steel Conduit), or GRC (Galvanized Rigid Conduit) in place of RMC (Rigid Metal
Conduit) in order to differentiate the type of metal used in the product.
Rigid
steel conduit (RSC) is a listed threaded metal raceway of circular cross section
with a coupling which can be either a standard straight tapped conduit coupling
or the integral type. Threads on the uncoupled end are covered by industry
color-coded thread protectors which protect the threads, keep them clean and
sharp, and aid in trade size recognition. Rigid metal conduit is available
in trade sizes 1/2 through 6. Thread protectors for trade sizes 1, 2, 3, 4,
5, and 6 are color-coded blue, trade sizes 1/2, 1 1/2, 2 1/2, 3 1/2 are black,
and trade sizes 3/4 and 1-1/4 are red. The nominal finished length of RMC
with couplings is 10 feet. Twenty foot lengths are available in some trade
sizes.
There
are different processes used to provide corrosion protection to rigid steel
conduit. Rigid steel conduit can have a primary coating of zinc, a combination
of zinc and organic coatings, or a nonmetallic coating (such as PVC). Supplementary
coatings can be applied to all three where additional corrosion protection
is needed.
(NOTE:
Contact manufacturers listed on the bottom of this page).
Rigid steel conduit is the heaviest-weight and thickest wall conduit. Where galvanized by the hot-dip process, it has a coating of zinc on both the inside and outside. Electro-galvanized rigid conduit has a coating of zinc on the exterior only, with approved corrosion resistant organic coatings on the interior. Rigid conduit with "alternate corrosion protection coatings" generally has organic coatings on both the exterior and the interior surfaces. Galvanized rigid metal conduit (GRC) is non-combustible and can be used indoors, outdoors, underground, concealed or exposed. Rigid steel conduit with coatings that are not zinc-based may have temperature limitations which will be noted on the manufacturer's product label and may not be listed for use in environmental air spaces; consult manufacturers’ listings and markings.
