Which requirement states that the disconnecting means must be capable of being locked in either closed or open positions?

• A. Arc-flash hazard
• B. Locking disconnecting means
• C. Enclosure-type number mark
• D. Accidental contact prevention

Answer: (B)

Locking the disconnecting means is about keeping the switch in a safe state during maintenance. If the disconnect can be locked in the open or closed position, a worker or supervisor can apply a padlock (and tag) to prevent anyone from energizing the circuit while service is being performed. This directly supports lockout/tagout procedures and stops accidental re-energization.

The other options don’t address this practical safety control: arc-flash hazard concerns the energy release risk, not the ability to physically lock the device; enclosure-type number mark deals with labeling, not operation locking; accidental contact prevention focuses on guarding or insulation, not on securing the disconnect against being turned on/off.