Arc Flash Calculator

Estimate arc flash incident energy, flash boundary, PPE category, and required cal rating per IEEE 1584.

Bolted Fault Current

Working Distance

NFPA 70E / IEEE 1584: switchgear 91 cm; MCC/panels 46 cm; open bus/switch 91–183 cm

Arc Duration

seconds

IEEE 1584: current-limiting fuse 0.008–0.017 s; electronic trip CB 0.05–0.1 s; thermal-mag CB 0.1–0.5 s

System Voltage

Gap Between Conductors

Tab to move between fields

Incident Energy

15.84 cal/cm²

PPE Category

Arc Flash Boundary2,216 mm

Required Cal Rating25 cal/cm²

How to Use This Calculator

Enter the Bolted Fault Current in amperes — obtain this from a short-circuit study or the utility's available fault current at the service entrance.
Enter the Working Distance in cm from the potential arc source to the worker's face: switchgear ≈ 91 cm, MCC/panel ≈ 46 cm.
Enter the Arc Duration in seconds — this is the clearing time of the upstream protective device (breaker trip time or fuse melt time).
Enter the System Voltage in volts and the Gap Between Conductors in mm: LV switchgear ≈ 32 mm, MCC ≈ 25 mm.
Read the Incident Energy in cal/cm² and the PPE Category (0–4) per NFPA 70E to select appropriate arc-rated PPE.
Note the Arc Flash Boundary in mm — workers within this distance must wear full arc-rated PPE; beyond it, only basic protection is required.

How the result changes with Working Distance

Bolted Fault Current: Available three-phase bolted fault current at the equipment.
Working Distance: Distance from potential arc source to worker per NFPA 70E Table 130.7(C)(15)(a) and IEEE 1584. Typical: open switchgear 91 cm (36"); MCCs/panels 46 cm (18"); motor control centers 46 cm; NEMA type panelboards 46 cm.
Arc Duration: Clearing time of the upstream protective device per NFPA 70E and IEEE 1584. Shorter clearing time reduces incident energy. Typical: electronic trip breaker 0.05–0.1 s; thermal-magnetic 0.1–0.5 s; current-limiting fuse 0.008–0.017 s.
System Voltage: Nominal system voltage at the equipment.
Gap Between Conductors: Gap between bus conductors. LV switchgear: 32 mm, MCC: 25 mm, panel: 25 mm.

Identify Input Parameters
4 parameters
Bolted Fault Current = 25000, Working Distance = 46, Arc Duration = 0.1, System Voltage = 480 = 5 input(s) provided
Calculate Incident Energy
Incident Energy = Math
15.84 = 15.84
Calculate PPE Category
3 = 3
Calculate Arc Flash Boundary
Arc Flash Boundary = Math
2216 = 2216
Calculate Required Cal Rating
Required Cal Rating
25 = 25

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