Calculate available fault current at the load using the point-to-point method. Determine the required interrupting rating for circuit breakers and fuses per NEC 110.9.
Based on NEC Article 110.9
Short circuit current (available fault current) must be calculated at every point in the electrical system to ensure overcurrent protective devices have adequate Ampere Interrupting Capacity (AIC) per NEC 110.9. The point-to-point method uses conductor impedance and distance to estimate fault current downstream of the transformer.
This calculator provides estimates for reference purposes only. Results must be verified by a licensed electrician or electrical engineer before any installation.
NEC Reference: NEC 110.9 - Interrupting Rating
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For Reference Only: This calculator is provided for educational and informational purposes only. It is not intended to be a substitute for professional engineering design, advice, or certification.
Code Compliance: Calculations are based on the 2023 National Electrical Code (NEC®). However, local codes, amendments, and Authority Having Jurisdiction (AHJ) requirements vary by location and may supersede standard NEC requirements.
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