Arc Flash Calculator

No -- treat this as an illustrative, educational estimate only, not a substitute for a qualified arc flash study. This calculator uses a simplified version of the IEEE 1584 low-voltage equations and does not account for electrode configuration, enclosure type, grounding configuration, or several other factors a real study requires. Real PPE selection for energized electrical work should be based on a facility-specific arc flash study performed to the current IEEE 1584 and NFPA 70E editions by a qualified engineer, using your actual fault current and protective device data.

Incident energy is roughly proportional to how long the arc is allowed to burn before the protective device (breaker or fuse) clears the fault, so doubling the clearing time roughly doubles the modeled incident energy. This is exactly why fast-clearing devices -- current-limiting fuses and instantaneous-trip breaker settings -- are such an effective real-world arc flash mitigation strategy: cutting clearing time in half can cut incident energy roughly in half too, often more than any change in PPE could compensate for.

Incident energy falls off with distance following a power-law relationship (an exponent greater than 1 in the underlying formula), meaning it drops off faster than a simple inverse relationship would suggest -- a modest increase in working distance produces a disproportionately large drop in the energy a worker's face and body would receive. This is why NFPA 70E-specified minimum approach and working distances are a genuine, physically grounded safety control, not just a conservative rule of thumb.

The arc flash protection boundary is defined as the specific distance from the arc source where incident energy drops to 1.2 cal/cm² (the threshold for a second-degree burn) -- it's a property of the arc itself (fault current, clearing time, voltage class, and gap), not of where you happen to be standing when you evaluate the calculator. The working distance input instead tells the calculator where YOU are relative to that boundary, which is why it changes the incident energy you'd personally receive, not the boundary's own location.

This simplified model primarily uses system voltage to select which set of low-voltage or medium-voltage equations applies (the two use different constants), rather than scaling incident energy continuously with the exact voltage value within one voltage class the way the full IEEE 1584 equations do. This is a known simplification of this tool, not a claim that voltage doesn't matter in a real arc flash study -- it is one more reason this calculator is illustrative only and not a substitute for a full study.