Arc flash analysis has been required by NFPA 70E since the 2000 edition as a condition of establishing safe work practices for energized electrical work. What changed over the following two decades is that plan review authorities in a growing number of jurisdictions began requiring arc flash incident energy calculations as part of the commercial electrical permit submittal, not just as a jobsite safety document. The shift caught many engineering firms off guard because arc flash analysis had historically been treated as something that happened after construction, not before permitting.
The result is a category of permit correction comments that engineering firms encounter without expecting to, particularly on medium-voltage services, large commercial switchgear, and projects that require work on energized equipment during construction or commissioning.
When Arc Flash Documentation Is Required for Permit
There is no uniform threshold across all jurisdictions. The NEC itself does not mandate that arc flash analysis results appear on permit drawings, but NFPA 70E Section 130.5 requires that an arc flash risk assessment be performed before work on or near energized electrical conductors or circuit parts. Some AHJs have incorporated NFPA 70E by reference into their commercial permit requirements, which extends the arc flash risk assessment obligation to the permit drawings for projects where energized work is foreseeable.
In practice, jurisdictions that require arc flash documentation on permit drawings typically apply the requirement to services above 480V, services above 1000A at 480V/277V, projects with medium-voltage switchgear or unit substations, and projects that include standby or emergency power systems with transfer switching equipment. Industrial facilities, data centers, healthcare facilities, and large commercial buildings with on-site generation are the most common project types where arc flash documentation becomes a permit requirement rather than a post-construction task.
The most reliable approach before any commercial permit submission is to check the jurisdiction's published submittal requirements directly, not to rely on what was or was not required on a previous project in the same jurisdiction. Arc flash documentation requirements have been added to commercial permit checklists in several major building departments in the past few years, and the change is often not publicized outside of permit office communications.
What the Calculation Must Show
When arc flash documentation is required for permit, the standard that governs the calculation is IEEE 1584, which provides the empirical equations for incident energy analysis. The current edition is IEEE 1584-2018, which introduced a more complex calculation method than the 2002 edition and requires additional system parameters to produce results. An arc flash study submitted using the simplified tables from the 2002 edition may be rejected if the jurisdiction specifies the 2018 edition.
The minimum documentation that plan reviewers expect to see includes the available short-circuit current at each analyzed bus, the clearing time for the upstream overcurrent device, the incident energy in cal/cm2 at the working distance, the arc flash boundary in feet or inches, and the required personal protective equipment (PPE) category or arc rating derived from those values. Bus labels on the arc flash study must match the panel and bus designations used on the single-line diagram and panel schedules. Mismatched labels generate immediate requests for clarification.
Some jurisdictions also require that arc flash labels be called out on the drawings, indicating where physical labels will be installed on equipment per NFPA 70E Section 130.5(H). The label content requirements under that section include the arc flash boundary, the incident energy and working distance, the minimum arc rating of required PPE, the nominal system voltage, and the available incident energy at the equipment.
The Most Common Calculation Gaps
The first gap is using utility-published impedance data without documenting the source. The available short-circuit current at the service entrance depends on the utility system impedance at the service delivery point. Engineers who use published utility impedance values without a written coordination letter or utility-supplied data sheet cannot substantiate the fault current value in plan review if the plan checker asks. Always obtain the available fault current value from the serving utility in writing and include that reference in the arc flash study documentation.
The second gap is using overcurrent device clearing time data that does not match the actual devices specified. The incident energy result is sensitive to clearing time. A calculation that assumes a circuit breaker clears in 0.05 seconds will produce a significantly lower incident energy than a calculation that uses the actual clearing time from the manufacturer's time-current curve for the specific device and trip setting shown in the panel schedule. When the arc flash study clearing times cannot be tied directly to the overcurrent devices on the permit drawings, the calculation is not verifiable and the plan checker will flag it.
The third gap is treating arc flash analysis as a separate deliverable from the permit drawings rather than as an integrated part of the drawing set. Arc flash study results that are submitted as a separate standalone report, without cross-reference to the single-line diagram and panel schedules, create a verification burden that most plan checkers will respond to with a correction comment requesting that the data be shown on the permit drawings or clearly keyed to them.
New Construction vs. Existing System Additions
For new construction, the arc flash analysis is performed on the as-designed system, using the equipment ratings and overcurrent device settings that appear on the permit drawings. For additions or modifications to existing systems, the analysis must account for the combined fault current contribution of the existing system and the new equipment. This requires information about the existing system that may not be readily available, particularly for older installations without up-to-date as-built drawings.
Plan reviewers for additions and modifications to existing systems will look for confirmation that the arc flash analysis reflects the post-modification system configuration, not just the new equipment in isolation. Submissions that analyze only the new section of the system without addressing the impact on the existing distribution equipment are a consistent source of correction comments for renovation and expansion projects.
What This Requirement Actually Reflects
The shift toward requiring arc flash documentation at permit review reflects a broader change in how building departments view the permit process. The permit review is not only a code compliance check. It is also a verification that the installation will be safe to operate and maintain. Arc flash analysis is one of the most direct tools available for quantifying the electrical hazards that workers will encounter when maintaining the installed system.
We are not saying that every commercial project needs a full IEEE 1584-2018 study in the permit package. Whether arc flash documentation is required, and at what level of detail, depends entirely on the jurisdiction and the project scope. But for projects where it is required, understanding what plan reviewers are looking for before the drawings go to permit is substantially cheaper than discovering the gaps during plan check.
