Rigid Metal Conduit (RMC)

RMC is the tank of raceways. Threaded connections, heavy wall, and with the right coating or finish it goes into corrosive and outdoor spots where lighter methods would not last.

The threads are also part of the ground path, so I make them up tight and use the right compound. A loose coupling is a bad ground and a future fault.

When it applies

Rigid metal conduit is the heavy hitter, the thickest steel wall in the raceway family, and it is permitted in nearly every location including areas that demand serious mechanical protection. When conductors face physical abuse, corrosive exposure with the right coating, or hazardous locations, RMC is often the specified method.

Common mistakes

• Cutting threads too short or too long so the fitting does not seat and the bond suffers.
• Skipping thread compound or a listed coating where corrosion is a factor.
• Exceeding the bend allowance between pull points and stressing the conductors.

In the field

In a plant I ream every cut to protect the insulation and I verify continuity across each coupling. The raceway is the equipment grounding path, so a sloppy joint is a real fault-clearing problem.