Calculator Inputs
Example Data Table
| Scenario | Method | Voltage | Fault Current | Clearing Time | Working Distance | Incident Energy | Boundary |
|---|---|---|---|---|---|---|---|
| Panel inspection | Direct | 480 V | 20.00 kA | 0.20 s | 18 in | 8.00 cal/cm² | 46.48 in |
| Switchboard troubleshooting | Direct | 600 V | 30.00 kA | 0.10 s | 24 in | 5.50 cal/cm² | 51.38 in |
| Temporary feeder check | Screening | 480 V | 18.00 kA | 0.15 s | 18 in | 6.40 cal/cm² | 41.57 in |
Formula Used
Arc Flash Boundary = Working Distance × √(Incident Energy at Working Distance ÷ Boundary Energy)
Estimated Arcing Current = Bolted Fault Current × Arcing Current Factor
Incident Energy ≈ [√3 × Voltage × Arcing Current × Clearing Time × Efficiency × Enclosure Factor] ÷ [4π × Distance² × 4.184]
This page is intended for screening, comparison, and documentation support. Use a qualified engineering study when labels, energized work permits, settings, or compliance decisions require formal calculations.
How to Use This Calculator
- Choose Direct mode when a label or study already gives incident energy at the working distance.
- Choose Screening mode when you want a fast planning estimate from available system values.
- Enter the working distance and confirm the correct unit before running the calculation.
- Review the boundary, incident energy, exposure band, and suggested minimum arc rating.
- Use the chart and export buttons to document comparisons, toolbox talks, or permit preparation notes.
Frequently Asked Questions
8 FAQs1) What is an arc flash boundary?
It is the distance where incident energy drops to the selected threshold, often 1.2 cal/cm². Outside that point, burn exposure is lower, but shock, blast, and task hazards can still remain.
2) Is this a full engineering study?
No. This page is a screening and documentation helper. Final labels, PPE decisions, and energized work planning should come from a qualified study using the applicable standard, equipment details, and protective device data.
3) Why are there two calculation methods?
Direct mode is best when incident energy at working distance is already known from a study or label. Screening mode helps compare scenarios quickly when only current, time, voltage, and distance are available.
4) How does distance affect the result?
The direct curve uses inverse-square scaling, so moving farther from the source lowers incident energy quickly. Small increases in working distance can materially reduce exposure and help shrink the calculated boundary.
5) Which inputs matter most in screening mode?
Clearing time, arcing current, working distance, and enclosure factor usually move results the most. Longer faults and closer working distances raise estimated incident energy very quickly.
6) Can I change the boundary threshold?
Yes. The default is 1.2 cal/cm², but you can enter another threshold for internal comparison, special procedures, or alternate study assumptions. Keep your documentation consistent with site policy.
7) Is construction the only use case?
No. The page fits temporary power, plant maintenance, switchboards, panels, MCCs, and retrofit work. The category is construction-focused, but the calculator can support many energized equipment planning discussions.
8) What unit options are supported?
You can enter working distance in inches, centimeters, millimeters, feet, or meters. Results are displayed in multiple units so crews, reports, and permits can use the most familiar format.