Master Electrician Exam (NEC)Special Occupancies, Equipment, and ConditionsMedium
A master electrician is installing a new industrial control panel in a Class I, Division 2 hazardous location where flammable gases are present. The panel contains switches, relays, and other control devices. Which wiring method is generally permitted for connecting components within this control panel?
- ANonmetallic-sheathed cable (NM cable)
- BFlexible cord, Type SOW
- COpen wiring on insulators
- DRigid metal conduit (RMC)
Show answer & explanationAnswer & explanation
Correct answer: D. Rigid metal conduit (RMC)
For Class I, Division 2 hazardous locations, rigid metal conduit (RMC) is a permitted wiring method, as specified in NEC 501.10(B)(1)(1). It provides robust physical protection and helps contain potential arcs or sparks within the conduit, preventing ignition of external flammable gases.
Why the other options are wrong
- A. NM cable is not permitted in hazardous locations due to lack of suitable protection and sealing.
- B. Flexible cords are generally not permitted for fixed wiring in hazardous locations, except for specific, limited applications.
- C. Open wiring is not permitted in hazardous locations due to lack of protection.
Class I, Div 2 Wiring Methods
Approved wiring methods for Class I, Division 2 hazardous locations, designed to prevent ignition of flammable gases or vapors.
- RMC, IMC, EMT, Type MC, and certain cables are common.
- Must prevent ignition of external atmosphere.
- Sealing fittings are often required.
Memory trick: In hazardous zones, wiring needs armor like a knight to fight the fire.