Field guide
Arc Flash Labels for Electrical Panels and Panelboards
Is a label required?
Yes, in almost every non-dwelling case. Panelboards and electrical panels are the textbook trigger for NEC 2026 §110.16 and NFPA 70E §130.5(H): they are opened for breaker additions, troubleshooting, and testing while energized as a matter of routine. NEC 2026 removed the old 1,000 A threshold, so the detailed-label requirement now reaches essentially all non-dwelling service and feeder equipment — a 100 A lighting panel is in scope the same way a 1,200 A switchboard is. The only honest exception is equipment that will never be worked energized, and "we always de-energize" is a claim the assessment record should back up, since verifying de-energization is itself energized work.
What the label shows for this equipment
A compliant panel label shows: nominal system voltage (e.g. 208Y/120 V or 480Y/277 V), incident energy in cal/cm² at the stated working distance, the arc-flash boundary, the PPE level (category or required rating), the assessment completion date (mandatory under NEC 2026), available fault current with its as-of date, and a study or label ID for traceability. For panelboards, the working distance is typically 455 mm (18 in) and the electrode configuration is usually VCB — vertical conductors in a metal box — unless the panel has a termination barrier (VCBB).
NFPA 70E table-method rows for this class
| Equipment class row | Max fault current | Max clearing time | PPE category |
|---|---|---|---|
| Panelboards and other equipment rated 240 V and below | 25 kA | 0.03 s (2 cycles) | 1 |
| Panelboards and other equipment rated above 240 V up to 600 V | 25 kA | 0.03 s | 2 |
Rows come from NFPA 70E-2018 Table 130.7(C)(15)(a), cells cross-verified against multiple independent reproductions. If your fault current or clearing time exceeds the row, the table does not apply — an IEEE 1584-2018 calculation is the path, which is what the calculator runs.
Notes specific to this equipment
Panelboards are where the table method usually fits — modest fault current and fast molded-case breakers keep many panels inside the 25 kA / 0.03 s rows. Two common ways panels fall out of the table: a stiff service pushing available fault current past 25 kA, or a main breaker whose instantaneous setting clears slower than two cycles at the arcing current. Both are calculation cases, not guessing cases. Multi-section switchboards get a label per section when the sections differ electrically.
What to collect before you calculate
Per panel: nominal voltage and phase, available fault current at the panel (from the utility letter, nameplate estimate, or point-to-point calculation — our fault-current guide covers all three), the upstream protective device type and settings for clearing time at the arcing current, conductor gap and enclosure dimensions if known, and the electrode configuration. A photo of the panel schedule and the main breaker faceplate, taken during a de-energized look, answers most of it.
Other equipment guides
Get the label numbers for your equipment in the free arc flash calculator — panel specs in, a reviewable record and label preview out. The master field list lives at arc flash label requirements; sizes and stock at the arc flash label template page.
Direct answers
Frequently asked questions
Do electrical panels need arc flash labels?
Yes, in non-dwelling buildings, when the panel is likely to be examined, adjusted, serviced, or maintained while energized. NEC 2026 §110.16 applies the detailed-label rule to essentially all non-dwelling service and feeder equipment, and panelboards are the most common case of it.
What PPE category is a typical panelboard?
Under the NFPA 70E table method: Category 1 for equipment rated 240 V and below (up to 25 kA, 0.03 s clearing) and Category 2 for equipment above 240 V up to 600 V (same caps). Outside those caps the category must come from an incident-energy calculation.
What working distance is used for panel work?
Our worked examples use 455 mm (18 in), the common low-voltage working-distance assumption for panel work in IEEE 1584-2018 calculations. The label states the distance its incident-energy value is computed at.
Source trail
Sources
Standards references identify the applicable document or section where possible. Standards text may require licensed access. Report a factual issue through the process on our corrections page.