⚠️ Disclaimer: This calculator provides estimates for educational purposes using a simplified IEEE 1584 model. Do not use for actual arc flash labeling or PPE selection. A full arc flash study by a licensed engineer using IEEE 1584-2018 software (ETAP, SKM, EasyPower) is required for compliance with NFPA 70E and OSHA 1910.269.
When to use: Arc flash analysis is required by NFPA 70E for any energized electrical work. The analysis determines incident energy (cal/cm²) — the amount of thermal energy that could contact a worker at a given working distance. This determines the required PPE category and establishes the arc flash boundary (the distance where a worker would receive a 1.2 cal/cm² second-degree burn). Results must be posted on equipment labels per NFPA 70E 130.5.
Arc flash analysis is required by NFPA 70E before performing energized electrical work. This calculator estimates incident energy (cal/cm²) and arc flash boundary (AFB) using a simplified IEEE 1584-2018 empirical model, helping engineers understand PPE category requirements for electrical equipment up to 15 kV.
IEEE 1584-2018 defines incident energy using empirical formulas derived from lab testing at voltages from 208 V to 15 kV. Incident energy (cal/cm²) depends on arcing current (kA), fault clearing time (ms), working distance (cm), bus gap (mm), and system voltage. The arc flash boundary (AFB) is the distance where incident energy equals 1.2 cal/cm² — the threshold for a second-degree burn. A complete study requires full IEEE 1584-2018 software (ETAP, SKM, EasyPower) by a licensed engineer.
NFPA 70E defines four PPE categories based on incident energy:
Category 0: up to 1.2 cal/cm² — arc-rated clothing minimum Category 1: 1.2–4 cal/cm² — arc rating ≥ 4 cal/cm² Category 2: 4–8 cal/cm² — arc rating ≥ 8 cal/cm² Category 3: 8–25 cal/cm² — arc rating ≥ 25 cal/cm² Category 4: 25–40 cal/cm² — arc rating ≥ 40 cal/cm²
Incident energy exceeding 40 cal/cm² means work must be performed de-energized (LOTO). All of this information must be posted on equipment labels per NFPA 70E 130.5(H).
The two most effective mitigations are reducing fault clearing time and increasing working distance. Zone-selective interlocking (ZSI) and high-speed current-limiting fuses dramatically reduce incident energy at 480 V. Bus differential protection reduces clearing time on medium voltage equipment. Arc flash reduction maintenance switches (ARMS) provide a temporary low-energy mode during maintenance work.
Enter system voltage, available arcing current (kA), fault clearing time in milliseconds, bus gap, and working distance. The calculator returns incident energy in cal/cm², arc flash boundary in meters, and required PPE category. Typical working distances: 60 cm for 480 V panelboards, 90 cm for 480 V switchgear and MCCs, 105 cm for 4,160 V switchgear.
Incident energy is the thermal energy (cal/cm²) delivered to a worker's face and chest at a specific working distance from an arcing fault. IEEE 1584-2018 defines the calculation method based on system voltage, arcing current, fault clearing time, bus gap, and working distance.
The most effective mitigations are reducing fault clearing time (use zone-selective interlocking, high-speed current-limiting fuses, or arc flash reduction maintenance mode) and increasing working distance. Current-limiting fuses at 480 V can reduce incident energy by 80–90% compared to standard circuit breakers.
It depends on available fault current and clearing time. Many 480 V MCC and panelboard buses fall in Category 2 (4–8 cal/cm²) but can reach Category 3 or higher near the main service if clearing time is slow. A full IEEE 1584-2018 arc flash study is required for actual equipment labeling under NFPA 70E.
This tool uses a simplified IEEE 1584 model for educational and planning purposes only. NFPA 70E and OSHA 1910.269 require a complete arc flash risk assessment using IEEE 1584-2018 software (ETAP, SKM, EasyPower) by a licensed electrical engineer for equipment labeling and PPE selection.
The arc flash boundary is the distance from an arcing fault at which a person could receive a second-degree burn (1.2 cal/cm² incident energy). Anyone within the AFB must wear appropriate PPE. NFPA 70E 130.5 requires the AFB, incident energy, and PPE category to be posted on equipment warning labels.
Try our Electrical Studio
More calculators, simulators, and guides for this discipline.