Phase Academy Interactive Power Systems Lab

SCCR, AIC & Fault Current Compliance Checker

Educational checker. Compares entered values; does not calculate AFC, verify listings, verify series ratings, or replace engineering/AHJ review.

Compliance Dashboard

Adjust inputs on the left to begin.

Fault Current vs Rating Comparison

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Sensitivity: What If AFC Changes?

See how compliance status shifts as available fault current varies from 25% to 200% of current value.

Equipment Comparison Explorer — Numeric Comparison Only

This explorer compares numbers only. It does not verify voltage rating, equipment type, listing, series rating, or manufacturer conditions.

Why This Matters

Every piece of electrical equipment has a maximum fault current it can safely interrupt or withstand. When available fault current at the point of installation exceeds that rating, the equipment may not clear the fault safely — creating risk of arc flash, fire, or catastrophic failure.

  • AIC applies to overcurrent protective devices — breakers and fuses must interrupt the maximum available fault current.
  • SCCR applies to assemblies — components must withstand fault current until upstream protection clears it.
  • The NEC requires equipment to be rated for available fault current at its installation point. Not optional, not approximate.
Short-circuit ratings matter most on the day something goes very wrong. That is exactly when you want them to be correct.
Educational Disclaimer: This tool checks entered values only. It does not calculate available fault current, verify manufacturer listings, verify series ratings, or replace engineering/AHJ review.

Step-by-Step Calculation Trace

The code path matters. The answer did not appear by magic.

Assumptions

    Compliance Result

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    Equipment Summary

    Current-Limiting Impact (Educational Visualization)

    Current-limiting credit is manufacturer/listing-specific. Generic percentage reductions are not valid for compliance.

    Mitigation Concepts

    When available fault current exceeds equipment ratings, these are general approaches.

    Current-Limiting Devices

    Current-limiting fuses/breakers can reduce peak let-through. Actual values are manufacturer-specific and require documented listed combinations.

    Higher-Rated Equipment

    Replace with units rated at or above available fault current. Direct but may have cost implications.

    Series-Rated Combinations

    Tested series-rated pairs can achieve higher combined SCCR. Both must be tested together and applied per the listing.

    Reduce Available Fault Current

    Higher-impedance transformers, reactors, or feeder reconfiguration. Requires engineering study.

    Educational Disclaimer: This tool is for learning only. Real compliance needs manufacturer data, a proper short-circuit study, and AHJ coordination.

    NEC Reference Panel

    Paraphrased educational summary only. Consult the adopted NEC edition and AHJ.

    AIC vs. SCCR — What Is the Difference?

    AIC (Ampere Interrupting Capacity)

    Applies to overcurrent protective devices — breakers and fuses. The max fault current the device can safely interrupt. If exceeded, the device may fail catastrophically. Cited under NEC 110.9.

    SCCR (Short-Circuit Current Rating)

    Applies to assemblies and equipment — panels, switchboards, MCCs, control panels, HVAC. The max fault current the assembly can withstand with its protective device operating. Limited by the weakest component. Cited under NEC 110.10 plus the applicable equipment article.

    A panelboard with a 65kA AIC main breaker but 22kA marked assembly SCCR is a 22kA SCCR panel — not 65kA. The weakest link determines the assembly rating unless a higher assembly rating is established by manufacturer/listing documentation.

    Code Logic Flow

    1. Determine available fault current at each equipment installation point.
    2. Identify equipment rating type — AIC for protective devices, SCCR for assemblies.
    3. Confirm voltage basis — the marked rating must apply at the system voltage.
    4. Compare: Rating must meet or exceed available fault current.
    5. Document: Field-mark available fault current at required equipment.
    6. Mitigate if necessary: documented current-limiting devices, higher-rated equipment, or tested series combinations.

    What to Notice

    • The ratio matters more than the absolute number. 10kA against 10kA-rated equipment is more dangerous than 40kA against 65kA-rated equipment.
    • Margin provides safety for unknowns. Available fault current can change from utility upgrades or transformer replacements.
    • Current-limiting is powerful but specific. A CL fuse only helps if it's the right type, right location, and tested for the combination.
    • SCCR is only as strong as the weakest component. A high-AIC breaker does not raise the SCCR of the entire assembly.

    Common Mistakes

    1. Confusing AIC and SCCR. A 65kA AIC breaker in a 10kA SCCR panel does not make the panel 65kA rated.
    2. Ignoring available fault current. Proceeding without a fault study means you're hoping equipment is rated high enough. Hope is not an engineering method.
    3. Assuming utility fault current doesn't change. Substation upgrades or new feeders upstream can increase fault current at your service entrance.
    4. Selecting equipment before knowing fault duty. Equipment should be selected after available fault current is known. Retrofitting is always more expensive.
    5. Applying generic CL percentages. Current-limiting credit is manufacturer/listing-specific; a generic "55%" is not valid for compliance.

    Interactive: Explore Equipment Ratings

    Numeric comparison only. Does not verify voltage rating, equipment type, listing, or manufacturer conditions.
    22kA

    Knowledge Quiz

    Test your understanding. Select the best answer for each question.

    Educational Disclaimer: This tool is for learning only. If available fault current exceeds the rating, optimism is not an approved mitigation method.

    Design Challenge Mode

    You are given a real-world scenario with constraints. Your job: select equipment ratings and protection strategies that achieve compliance. The system will grade your design.

    Note: These challenges use simplified models. Real designs require coordination studies, manufacturer data, and AHJ review.