The NFPA 70E informational note to Table 130.7(C)(15)(a) lists the typical fault clearing time for insulated case circuit breakers as 'none of the above'.

• A. 1 s
• B. 0.5 s
• C. 2 s
• D. None of the above

Answer: (D)

Fault clearing time for protective devices can strongly influence the arc flash energy you’re exposed to, but for insulated-case circuit breakers there isn’t a single, fixed value that applies to all devices. These breakers rely on both thermal and magnetic trip elements, and the exact time to interrupt a fault depends on the specific breaker design, the fault current level, and how the protection scheme is coordinated. Because of that variability, there isn’t a universal number like 1 second, 0.5 second, or 2 seconds that represents all insulated-case breakers. The informational note is signaling that you should not apply a fixed time to ICCBs; instead, you should use the device’s time-current data or manufacturer information to determine the actual clearing time for a given fault scenario. This is important when estimating incident energy and selecting PPE, since the clearing time directly affects the energy released during the arc.