An arc flash study is an engineering analysis in which your electrical distribution system is modeled in specialized software such as SKM Power*Tools or EasyPower. The model calculates incident energy at each piece of equipment, determines the arc flash boundary, and identifies the personal protective equipment a worker must wear to work on or near it. The engineer then reviews the results and adjusts protective device settings or recommends mitigation where incident energy is higher than it needs to be.
The deliverable is a sealed report, time current curve plots, and a label on every piece of equipment telling a worker exactly what they are standing in front of.
When an arc flash study is required
Existing facilities
OSHA is the law. It requires employers to protect workers from electrical hazards, and NFPA 70E is the standard describing how.
Employees working in areas where there are potential electrical hazards shall be provided with, and shall use, electrical protective equipment that is appropriate for the specific parts of the body to be protected and for the work to be performed.
An arc flash risk assessment shall be performed to identify arc flash hazards, estimate the likelihood of occurrence of injury and the potential severity of injury, and determine whether additional protective measures are required, including the use of PPE.
The assessment shall be reviewed at intervals not to exceed five years, and updated when a change in the electrical distribution system could affect the results.
New construction
When Division 26 05 73 — Power System Studies — is part of the specifications package, it requires both a protective device coordination study and an arc flash study. These are normally completed before electrical equipment is ordered, because the calculations depend on final equipment ratings, protective devices, and system configuration. Running them early means the system is properly coordinated and incident energy is evaluated before procurement rather than after.
The Authority Having Jurisdiction — typically the electrical inspector — may withhold approval and the Certificate of Occupancy until arc flash labels are installed. On a project running to schedule, that turns a study into a critical path item.
Electrical equipment likely to require examination, adjustment, servicing, or maintenance while energized must be field marked to warn qualified persons of potential arc flash hazards.
What triggers a re-study
Beyond the five-year review, the results change whenever the system changes. Call us if any of the following has happened since your last study:
- A utility service upgrade or a new or replaced transformer
- Solar PV or battery energy storage added behind the meter — on-site generation contributes fault current and can change incident energy
- Protective device settings changed, or breakers or fuses replaced with different types
- New switchgear, switchboards, MCCs, or panelboards added
- A building addition, a new feeder, or a significant load change
- Labels that are faded, missing, or reference an older edition of NFPA 70E
How to choose a company for arc flash studies
The market has a wide quality range and the differences are not obvious from a proposal. Three things worth verifying before you sign anything:
1. A licensed P.E. Electrical Engineer seals the final report
This is the single most important question. The study's output determines what a person wears when they open an energized enclosure. Ask for the license number.
2. Every panel appears in the coordination study
Each panel should show up in the time current curve (TCC) plots. If the TCCs only cover main gear and the branch panels were assumed rather than modeled, the coordination has not actually been evaluated.
3. Ask who is doing the data collection
Data collection is the major hurdle on nearly every project. Frequently the correct system information is not gathered because the field work was handed to electricians who were never trained on what the engineer needs. Missing conductor lengths, unrecorded breaker settings, and guessed transformer impedances all propagate straight into the incident energy numbers.
Phase Engineering always sends a P.E. Electrical Engineer to gather data, with an electrician as support to open panel covers. The person who has to defend the model is the person who collects the inputs.
What you receive
- Short circuit study — available fault current at every bus, with equipment ratings evaluated against it
- Protective device coordination study with time current curve plots
- Incident energy analysis and arc flash boundaries
- Arc flash labels meeting NFPA 70E and NEC 110.16, printed and installed
- Equipment evaluation and mitigation recommendations, explained to your team rather than mailed over
- A report sealed by a California licensed Professional Engineer
- The system model, so future changes can be evaluated without starting over
Arc flash labels
Common questions
Is an arc flash study required by law?
OSHA requires employers to protect workers from electrical hazards, and NFPA 70E 130.5 requires an arc flash risk assessment to determine what protection is needed. The assessment is how you demonstrate compliance.
How often does the study need updating?
At intervals not exceeding five years, and sooner whenever the distribution system changes in a way that could affect the results.
Do you work outside the Central Valley?
Yes. We are based in Visalia and work throughout California. The modeling is done from the data; what has to be local is the site visit, and we travel for it.
Talk to the engineer who does the work
No sales team. You speak directly with a California licensed Professional Engineer about your equipment, your schedule, and what the study will actually cost.