An industrial electrician is installing a new control circuit in a hazardous location identified as Class I, Division 2. Which of the following wiring methods is generally NOT permitted for the interconnection of devices in this specific location?
- AType MC Cable with a gas/vaportight sheath
- BLiquidtight Flexible Metal Conduit (LFMC)
- CElectrical Metallic Tubing (EMT)
- DRigid Metal Conduit (RMC)
Show answer & explanationAnswer & explanation
Correct answer: C. Electrical Metallic Tubing (EMT)
For Class I, Division 2 locations, wiring methods must prevent the entry of ignitable concentrations of gases or vapors. While RMC, LFMC, and certain Type MC cables are permitted, Electrical Metallic Tubing (EMT) is generally not permitted for interconnections of devices because its fittings are not considered explosionproof or inherently gas/vaportight, unlike RMC or LFMC with appropriate fittings, or sealed MC cable. Refer to NEC Article 501.10(B).
Why the other options are wrong
- A. Type MC Cable with a gas/vaportight continuous corrugated metallic sheath and appropriate termination fittings is permitted.
- B. LFMC is permitted in Class I, Division 2 locations with listed fittings, subject to length limitations.
- D. RMC is generally permitted in Class I, Division 2 locations when installed with appropriate explosionproof fittings.
Class I, Division 2 Wiring Methods
Specific wiring methods required in Class I, Division 2 hazardous locations to prevent the ignition of flammable gases or vapors, characterized by the need for sealed or explosionproof integrity.
- Hazardous locations are defined by NEC Article 500.
- Class I, Division 2 means ignitable concentrations are present only under abnormal conditions.
- Wiring methods must prevent gas/vapor entry to prevent ignition.
Memory trick: In Div 2, seal it tight, don't let the gas ignite, EMT is not the 'safe tube'.