In Class III locations, circuits for electric cranes operating over combustible fibers shall not be ___.

In Class III locations, circuits for electric cranes operating over combustible fibers shall not be ___.

• A. spliced
• B. run in raceways
• C. THHN conductors
• D. grounded

Answer: (D)

In Class III locations the focus is on preventing ignition from electrical equipment near easily ignitable fibers. Grounding a circuit creates a definite path for fault current and can energize metal surfaces or produce arcing to ground if insulation or connections fail. That spark or heat could ignite the combustible fibers. Keeping the crane circuits ungrounded minimizes the chance of a ground-fault spark or heat reacting with the fibers, which is why the requirement is that these circuits shall not be grounded. Splicing, running conductors in raceways, and using THHN conductors are standard ways to protect and route wiring, but they don’t address the ignition risk from a grounded fault the way an ungrounded circuit does in this specific hazardous location.

In Class III locations the focus is on preventing ignition from electrical equipment near easily ignitable fibers. Grounding a circuit creates a definite path for fault current and can energize metal surfaces or produce arcing to ground if insulation or connections fail. That spark or heat could ignite the combustible fibers. Keeping the crane circuits ungrounded minimizes the chance of a ground-fault spark or heat reacting with the fibers, which is why the requirement is that these circuits shall not be grounded. Splicing, running conductors in raceways, and using THHN conductors are standard ways to protect and route wiring, but they don’t address the ignition risk from a grounded fault the way an ungrounded circuit does in this specific hazardous location.