Journeyman Electrician Exam (NEC)Wiring Methods and MaterialsHard
An industrial electrician is running a new 480-volt feeder through an area where corrosive fumes are regularly present. Which type of raceway is generally considered the most suitable for this environment, according to the NEC?
- APolyvinyl Chloride (PVC) conduit
- BElectrical Metallic Tubing (EMT)
- CRigid Metal Conduit (RMC)
- DGalvanized Rigid Nonmetallic Conduit (GRNC)
Show answer & explanationAnswer & explanation
Correct answer: A. Polyvinyl Chloride (PVC) conduit
NEC 352.10(B) permits the use of Schedule 40 and 80 PVC conduit in corrosive atmospheres where identified for the purpose. Metallic conduits like EMT and RMC, even if galvanized, can be susceptible to corrosion in severe chemical environments. GRNC is not a recognized NEC raceway type; 'Galvanized Rigid Nonmetallic Conduit' is a contradiction, as nonmetallic conduits are not galvanized. PVC is generally preferred for its excellent corrosion resistance.
Why the other options are wrong
- B. Incorrect. EMT is generally not suitable for corrosive environments without special coatings, as its thin walls can quickly corrode.
- C. Incorrect. While RMC is more robust than EMT, even galvanized RMC can corrode in severely corrosive atmospheres, requiring additional protection.
- D. Incorrect. 'Galvanized Rigid Nonmetallic Conduit' is not a recognized type of raceway in the NEC. Nonmetallic conduits are not galvanized.
Raceways in Corrosive Areas
The NEC mandates specific raceway types or protection methods for installations in corrosive environments to prevent degradation and ensure the longevity and safety of the electrical system.
- NEC Article 300.6 details protection against corrosion.
- Rigid Nonmetallic Conduit (RNC), such as PVC, is inherently corrosion-resistant.
- Metallic raceways may require supplementary protection (e.g., special coatings, wraps) in corrosive areas.
- The suitability of a raceway depends on the specific corrosive agents present.
Memory trick: Corrosive fumes? PVC assumes!