Arc Flash Incident Energy Estimator
How much energy would an arc release, and how far does the danger reach? Every applicable published method is worked out and the highest one is used, so this errs toward more protection rather than less.
SCREENING ESTIMATE
Built on the published NFPA 70E Annex D methods. This is NOT an IEEE 1584-2018 study and does not replace one. Do not select PPE from this number alone.
The system
Line to line, at the equipment
V
From a short-circuit study — not a guess
kA
Advanced / Custom Input — the system
Used only to look up the clearing time on the device curve.
%
The onset of a second-degree burn on bare skin.
cal/cm²
The equipment
Sets a typical working distance and whether the arc is enclosed
Arc to your face and chest — not to your hands
in
Advanced / Custom Input — the equipment
An enclosure focuses the energy outward, which makes it worse.
Recorded on the result for reference. The published Annex D equations do not take it as an input.
mm
How fast does it clear?
This is the single biggest lever there is. Incident energy is directly proportional to clearing time — halve the time and you halve the energy.
Sets a typical clearing time — replace it with the real one
Read off the device curve AT the arcing current
s
Advanced / Custom Input — timing
Relay time plus the breaker's own opening time. Added to the figure above.
s
Some studies cap at 2 s on the basis that a person can move away. Use 0 for no cap.
s
The PPE you have
The ATPV or EBT on the label. Leave at 0 to skip the check.
cal/cm²
Advanced / Custom Input — the category thresholds
cal/cm²
cal/cm²
cal/cm²
Above this, NFPA 70E does not permit energized work at all.
cal/cm²
Result
Put in the voltage, the bolted fault current and the clearing time, then press “Estimate the incident energy”.
Screening estimate only, built on the published NFPA 70E Annex D methods — not an IEEE 1584-2018 study. Do not select PPE from this number alone. A qualified engineer must carry out the arc flash risk assessment, and de-energizing remains the only method that removes the hazard.