Air conditioning overcurrent protective devices can never exceed what percentage of the motor-rated load current or the branch circuit selection current (whichever is greater)?

• A. 120%
• B. 150%
• C. 225%
• D. 300%

Answer: (C)

The best choice in this scenario is that air conditioning overcurrent protective devices must never exceed 225% of the motor-rated load current or the branch circuit selection current, whichever is greater. This standard is established in the National Electrical Code (NEC) to ensure that the overcurrent protection can accommodate the inrush current that motors experience when starting.

The rationale behind allowing this level of overcurrent protection is that during startup, motors can draw several times their rated current, especially in the case of hermetic compressors found in air conditioning units. The 225% threshold provides enough headroom to handle these temporary spikes without tripping the overcurrent device prematurely, while still offering protection against prolonged overloads or faults.

In contrast, the other percentages mentioned, like 120%, 150%, and 300%, either do not provide sufficient allowance for motor starting currents or exceed the standards typically recognized for safe operation. Therefore, the established margin of 225% acts as a balance between operational needs and safety regulations, ensuring motors can run effectively without risking damage or safety hazards.