Electrical Conduits: RMC

Vocabulary terms covering specifications, National Electrical Code sizing constraints, physical construction differences, and installation purposes for Rigid Metal Conduit (RMC), Intermediate Metal Conduit (IMC), and Rigid Nonmetallic Conduit (RNC/PVC).

Rigid Metal Conduit (RMC) Thread Protectors — 1-Inch Increments

Thread protectors colored blue to identify conduit sized in $1''$ increments.

Rigid Metal Conduit (RMC) Thread Protectors — 1/2-Inch Increments

Thread protectors colored black to identify conduit sized in $1/2''$ increments.

Rigid Metal Conduit (RMC) Thread Protectors — 1/4-Inch Increments

Thread protectors colored red to identify conduit sized in $1/4''$ increments.

National Pipe Thread

The standard thread specification utilized on Rigid Metal Conduit and Intermediate Metal Conduit, defined by a $3/4''$ taper per foot (1 inch 16 taper).

Trade Size Determination (RMC)

The procedure of determining the trade size of Rigid Metal Conduit by measuring its outside diameter and subtracting $3/8''$.

Minimum Trade Size for RMC

The smallest size permitted by the National Electrical Code for Rigid Metal Conduit, which states that sizes smaller than trade size $1/2''$ shall not be used.

RMC Physical Seam

A smooth interior seam characteristic of Rigid Metal Conduit, distinguishing it from galvanized plumber's pipe which can possess a rough seam.

RMC Couplings

Couplings manufactured with straight threads, unlike traditional galvanized plumber's pipe couplings which feature tapered threads.

Standard Length of RMC

A standard manufactured length of $10\text{ feet}$ equipped with a coupling (bell end coupling).

Purposes of RMC

Three specific electrical installation functions: providing a raceway for conductors, protecting wire from damage, and providing an electrical path for an equipment ground.

Intermediate Metal Conduit (IMC) Thread Protectors — 1-Inch Increments

Thread protectors colored orange to designate conduit sized in $1''$ increments.

Intermediate Metal Conduit (IMC) Thread Protectors — 1/2-Inch Increments

Thread protectors colored yellow to designate conduit sized in $1/2''$ increments.

Intermediate Metal Conduit (IMC) Thread Protectors — 1/4-Inch Increments

Thread protectors colored green to designate conduit sized in $1/4''$ increments.

Minimum Trade Size for IMC

The smallest size permitted by the National Electrical Code for Intermediate Metal Conduit, specifying that sizes smaller than trade size $1/2\text{ inch}$ shall not be used.

Maximum Trade Size for IMC

The largest size permitted by the National Electrical Code for Intermediate Metal Conduit, specifying that sizes larger than trade size $4\text{ inch}$ shall not be used.

IMC Stamping Requirement

The mandatory manufacturer marking consisting of the letters 'IMC' stamped along the conduit at least once every $5\text{ feet}$.

Maximum Degree of Bend (IMC)

The total cumulative limit of bends allowed in a single run of Intermediate Metal Conduit, which is $360^\top$ degrees.

RMC vs. IMC Wall Construction

The primary structural difference between the two conduits: Rigid Metal Conduit (RMC) has a thicker wall than Intermediate Metal Conduit (IMC).

Purposes of IMC

Three specific electrical installation functions: providing a raceway for conductors, protecting wire from damage, and providing an electrical path for an equipment ground.

Polyvinyl Chloride (PVC)

The plastic compound acronym composing Rigid Nonmetallic Conduit, which also serves as the common name used by electricians for this raceway.

Schedule 40 (SCH 40)

The ordering designation specifying standard wall thickness for Rigid Nonmetallic Conduit.

Schedule 80 (SCH 80)

The ordering designation specifying the heaviest wall thickness available for Rigid Nonmetallic Conduit.

RNC Bonding Agent

Glue or solvent utilized to bond Rigid Nonmetallic Conduit sections to Rigid Nonmetallic Conduit fittings.

RNC Thread Specification

None; standard lengths of Rigid Nonmetallic Conduit do not feature threads.

Minimum Trade Size for RNC

The smallest size permitted by the National Electrical Code for Rigid Nonmetallic Conduit, stating that sizes smaller than trade size $1/2\text{ inch}$ shall not be used.

Maximum Trade Size for RNC

The largest size permitted by the National Electrical Code for Rigid Nonmetallic Conduit, stating that sizes larger than trade size $6\text{ inch}$ shall not be used.

RNC Bending Equipment

An external heat source required to bend Rigid Nonmetallic Conduit, such as a heating blanket, heating box, or weed burner.

Standard Length of RNC

A standard manufactured raceway segment measuring $10\text{ feet}$ with a bell end.

Optional Formats for RNC

Alternative raceway distributions available in $20\text{ feet}$ straight lengths or supplied on a continuous reel.

Purposes of RNC

Two specific electrical installation functions: providing a raceway for conductors and protecting wire from damage.