Formula Used
This calculator uses a planning model based on electrical energy release and distance spreading.
Arcing current: Ia = Ibf × Rv × Rg × M
Voltage ratio: Rv = clamp(0.50 + 0.08 log10(V / 208) − 0.0009(G − 25), 0.35, 0.95)
Arc time: t = max(direct arc time, clearing cycles / frequency)
Incident energy: E = (V × Ia × t × F) / (4πD² × 4.184)
Arc flash boundary: Boundary = D × √(E / 1.2)
V is volts. Ia is amperes. t is seconds. D is working distance in centimeters.
E is incident energy in cal/cm². F is the combined enclosure, electrode, equipment, and gap factor.
How To Use This Calculator
- Enter the line voltage and available bolted fault current.
- Add the conductor gap and normal working distance.
- Enter the expected arc duration or protective device cycles.
- Select enclosure, electrode, grounding, and equipment options.
- Press the calculate button and review the result above the form.
- Download the CSV or PDF file for a simple record.
Example Data Table
| Scenario |
Voltage |
Fault Current |
Gap |
Distance |
Arc Time |
Use Case |
| Panelboard |
480 V |
20 kA |
32 mm |
18 in |
100 ms |
Low voltage service planning |
| Switchgear |
600 V |
35 kA |
50 mm |
24 in |
200 ms |
Main gear comparison |
| Transformer Secondary |
415 V |
28 kA |
38 mm |
18 in |
80 ms |
Maintenance mode review |
Arc Flash Incident Energy Guide
Why Incident Energy Matters
Arc flash incident energy shows the heat that can reach a worker during an electrical arc. It is often shown in calories per square centimeter. A higher value means a higher burn hazard. This calculator helps you study that hazard with clear inputs. It is useful during early planning, training, and equipment review.
How The Estimate Works
The tool estimates arcing current from bolted fault current. It then estimates released electrical energy during the clearing time. Working distance reduces exposure because energy spreads before it reaches the worker. Enclosures, electrode direction, and grounding can increase or reduce the value. These options make the estimate more practical than a simple current and time check.
Reading The Result
The result includes estimated arcing current, incident energy, and arc flash boundary. The boundary is the distance where energy falls to 1.2 cal/cm². That level is commonly used as the start of a second degree burn hazard. The result also shows a planning category. This helps teams compare scenarios quickly.
Input Quality Matters
Use the calculator by entering realistic equipment data. Start with the line voltage, available fault current, and working distance. Add the protective device clearing time. If you know breaker cycles, enter them too. The larger time is used, so delayed tripping is not missed. Select the enclosure and electrode options that match the equipment.
Use It As Planning Support
The formula is a planning model. It is not a replacement for a formal arc flash study. Real studies may need detailed conductor gaps, enclosure dimensions, protective device curves, motor contribution, and current limiting effects. They may also need recognized standards and field verification. Always review final labels with a qualified professional.
Practical Review Steps
The best use of this page is comparison. Try shorter clearing times. Test larger working distances. Compare open and enclosed equipment. Review how each change affects energy and boundary. This supports safer maintenance planning. It also helps explain why coordination, labeling, and correct protection matter.
Export And Record Assumptions
Save the CSV for records. Export the PDF for simple review. Keep assumptions with every result. Clear assumptions make later engineering review easier. Review labels after every equipment change.
FAQs
What is arc flash incident energy?
It is the heat energy expected at a working distance during an arc flash. It is usually shown in cal/cm². Higher values mean greater burn risk.
Is this a final arc flash study?
No. This is a planning calculator. A final study should use verified equipment data, protective device curves, field conditions, and qualified engineering review.
Why is working distance important?
Energy spreads as distance increases. A larger working distance usually lowers incident energy. Short distances can increase exposure sharply.
What is bolted fault current?
It is the available short circuit current before arc behavior is considered. The calculator estimates arcing current from this value.
Why enter protective device cycles?
Cycles help estimate clearing time. The calculator compares cycle time with entered arc time and uses the larger value for caution.
What does the arc flash boundary mean?
It is the estimated distance where incident energy falls to 1.2 cal/cm². It helps define a planning boundary around energized equipment.
Why do enclosure and electrode options matter?
Enclosures and electrode direction can focus arc energy. These options adjust the estimate so it better reflects practical equipment layouts.
Can I export the result?
Yes. After calculation, use the CSV button for spreadsheet records or the PDF button for a simple printable summary.