Journeyman Electrician Exam (NEC)Wiring Methods and MaterialsMedium
An industrial electrician is installing a new control circuit in a hazardous location identified as Class II, Division 1. Which of the following wiring methods is generally permitted for this application?
- AType NM (nonmetallic-sheathed) cable
- BType AC (armored) cable
- CFlexible metal conduit (FMC) with standard fittings
- DThreaded rigid metal conduit (RMC) with listed fittings
Show answer & explanationAnswer & explanation
Correct answer: D. Threaded rigid metal conduit (RMC) with listed fittings
For Class II, Division 1 locations, NEC Section 502.10(A)(1) permits wiring methods such as threaded rigid metal conduit (RMC) with listed fittings, intermediate metal conduit (IMC), or dusttight wireways. Other methods listed are not generally permitted for Class II, Division 1 due to the presence of combustible dust.
Why the other options are wrong
- A. Not permitted in Class II locations due to dust penetration risk.
- B. Not permitted in Class II, Division 1 locations.
- C. Standard FMC is not permitted; only specific types of flexible connections with dusttight fittings are allowed in limited circumstances.
Class II, Division 1 Wiring
Specific wiring methods required in locations where combustible dust is present under normal operating conditions.
- Focus on preventing dust ingress.
- Requires robust, dusttight enclosures and raceways.
- Examples include RMC, IMC, dusttight wireways.
Memory trick: Dusty DIV 1 demands rigid, sealed conduits.