A disconnecting means of adequate capacity for at least ___ percent of the input required for the momentary rating or ___ percent of the input required for the long-time rating of medical X-ray equipment, whichever is greater, shall be provided in the supply circuit.

• A. 80 100
• B. 80 125
• C. 125 125
• D. 50 100

Answer: (D)

Sizing a disconnecting means for medical X-ray equipment must cover both momentary and long-time current demands. For the momentary rating, the disconnect only needs to handle at least half of the input current. For the long-time rating, it must handle the full input current. The rule “whichever is greater” means you choose the higher of these two requirements. In practice, the long-time rating dominates, so the disconnect should be capable of interrupting 100% of the input current. Therefore, the required capacities are 50% for momentary and 100% for long-time, whichever is greater. This is why the correct values are 50 percent and 100 percent.