Calculator Inputs
Example Data Table
| Case | Voltage (V) | Fault (kA) | Time (s) | Distance (mm) | Equipment | Incident Energy (cal/cm²) | Boundary (mm) | Suggested PPE |
|---|---|---|---|---|---|---|---|---|
| LV Switchgear Feeder | 480 | 35.00 | 0.200 | 457 | Low Voltage Switchgear | 4.84 | 1,178 | Suggested PPE band 2 |
| MCC Bucket | 480 | 22.00 | 0.100 | 455 | Motor Control Center | 1.22 | 459 | Suggested PPE band 1 |
| Panelboard Service | 240 | 10.00 | 0.080 | 455 | Panelboard | 0.15 | 112 | Below 1.2 cal/cm² screening threshold |
| Open Air Disconnect | 600 | 15.00 | 0.150 | 610 | Open Air Equipment | 0.36 | 271 | Below 1.2 cal/cm² screening threshold |
Formula Used
Arcing current is estimated from bolted fault current and adjusted by voltage, gap, equipment type, and electrode orientation.
Iarc = Ibf × Arc Ratio
Arc Ratio = (0.80 + 0.00025 × V) × (25 / Gap)0.04 × equipment factor × orientation factor
E = 1.25 × (V / 480)0.82 × (Iarc / 20)1.05 × (t / 0.20) × (610 / D)1.473 × adjustment factors
Boundary = Working Distance × (Incident Energy / Threshold)1 / 1.473
The adjustment factors include enclosure style, grounding method, X/R ratio, electrode orientation, and maintenance condition. This model is intentionally conservative for education and screening, but it is not a certified standard calculation.
How to Use This Calculator
Enter the system voltage, available bolted fault current, and the protective device clearing time. These three inputs control the base severity of the event.
Set the working distance and electrode gap to reflect the equipment and task. Shorter distances and longer durations usually raise incident energy sharply.
Choose the equipment type, enclosure style, grounding method, and electrode orientation. These inputs tune the estimate to the construction of the equipment.
Adjust the X/R ratio and maintenance factor if you want a more conservative screening result. Then press the calculate button to see energy, boundary, and PPE guidance.
Use the CSV and PDF buttons to export the result for review packs, training notes, or maintenance planning records.
FAQs
1) What does this arc flash calculator estimate?
It estimates arcing current, incident energy, flash boundary, arc power, and a suggested PPE band. The page is meant for engineering screening, comparison, and planning rather than formal labeling.
2) Is this result suitable for compliance labeling?
No. Use a qualified professional and a formal study method for equipment labels, energized work permits, and final PPE decisions. This tool is a preliminary estimate only.
3) Why does clearing time matter so much?
Incident energy rises almost directly with arc duration. If the breaker or fuse clears faster, the total heat exposure drops quickly and the boundary usually becomes smaller.
4) How does working distance affect the result?
Energy falls as distance increases. Even moderate changes in working distance can lower exposure significantly, which is why racking tools and remote operation are valuable controls.
5) Why are equipment and enclosure options included?
Different constructions channel arc products differently. Enclosures can focus pressure and plasma, while open air arrangements often let energy spread out more broadly.
6) What is the maintenance factor for?
It lets you tune the estimate for cleaner or poorer equipment condition. Higher values make the screening result more conservative when maintenance quality is uncertain.
7) What does the flash boundary represent?
It is the estimated distance where incident energy falls to the selected threshold. Many studies use 1.2 cal/cm², but you can change that threshold for internal reviews.
8) Can I use this for medium-voltage systems?
It can provide a rough screening estimate across a wide voltage range, but medium-voltage applications should be checked with a rigorous study because assumptions become more sensitive.