−---
−title: Arc-Flash Hazard Analysis
−category: Electrical / Power Studies
−toc_depth: 3
−description: >
− When to use: Engineering analysis to calculate incident energy and the arc-flash boundary at every piece of electrical equipment where workers may interact with the equipment while it is energized or while it could be placed into an electrically safe work condition. Applies to AC systems from 208V through medium voltage, in commercial, institutional, industrial, and healthcare facilities. The study produces equipment labels, PPE specifications, and the documentation that supports an NFPA 70E-compliant electrical safety program.
− Not intended for: Short-circuit analysis on its own (see [[sync/short-circuit-study]]), protective device coordination on its own (see [[sync/protective-coordination-study]]), DC system arc-flash analysis (covered by NFPA 70E Article 130.5 informational annexes rather than IEEE 1584), arc-flash analysis of utility-owned equipment upstream of the service point, or development of the site's electrical safety work practices program itself (the study is an input to the program, not a substitute for it).
−---
−
−# Scope
−
−This specification covers the engineering analysis required to determine the incident energy exposure and arc-flash boundary at each location in an electrical power system where a worker may interact with energized equipment, and to produce the equipment labels and the supporting documentation required by NFPA 70E and NFPA 70 (NEC). The analysis shall be performed using the calculation methodology of IEEE 1584, current edition, supplemented for conditions outside the IEEE 1584 model range by methods identified in NFPA 70E Annex D.
−
−An arc-flash hazard analysis is not a stand-alone study. Incident energy at any bus depends on both the arcing current at that bus (a short-circuit problem) and on the clearing time of the protective device upstream (a coordination problem). The arc-flash study shall be performed only after the short-circuit study per [[sync/short-circuit-study]] and the protective device coordination study per [[sync/protective-coordination-study]] are complete and the protective device settings are finalized. Re-running the arc-flash calculation with assumed device settings and reconciling later is a common source of error and shall not be done; an arc-flash label is only valid when the device that clears the arc has been set to the values used in the calculation.
−
−The study deliverable is twofold. First, a calculation report that documents the system model, the input data, the methodology, and the results bus-by-bus. Second, a set of physical labels installed on the equipment so that a worker about to open a door or remove a cover can read, in front of the equipment, the incident energy at the working distance, the arc-flash boundary, the nominal voltage, and the PPE required to perform the intended task. Both deliverables are required; neither substitutes for the other.
−
−This standard does not establish the site's electrical safety program. It produces the technical inputs that the safety program relies on. The Owner remains responsible for adopting NFPA 70E (or an equivalent standard), training qualified workers, establishing energized-work permitting, providing and maintaining PPE, and reviewing the analysis on the schedule required by NFPA 70E. Coordinate work practices and training with [[sync/electrical-safety-program]].
−
−Coordinate equipment scope with [[sync/low-voltage-switchgear]], [[sync/medium-voltage-switchgear]], [[sync/low-voltage-switchboards]], [[sync/low-voltage-panelboards]], [[sync/motor-control-centers]], and [[sync/dry-type-transformers]]. The arc-flash study includes every piece of equipment specified by those standards that is within the analysis voltage threshold.
−
−# Referenced Standards
−
−Analysis, labeling, and documentation shall comply with the latest adopted edition of the following standards and codes. Where the contract documents, the adopted edition of NFPA 70, or a referenced standard conflict, the more stringent requirement shall govern unless the Engineer of Record directs otherwise in writing.
−
−| Standard | Title |
−|----------|-------|
−| IEEE 1584 | Guide for Performing Arc-Flash Hazard Calculations |
−| IEEE 1584.1 | Guide for the Specification of Scope and Deliverable Requirements for an Arc-Flash Hazard Calculation Study in Accordance with IEEE Std 1584 |
−| NFPA 70 | National Electrical Code (Articles 110.16, 130.5, 240.87) |
−| NFPA 70E | Standard for Electrical Safety in the Workplace |
−| OSHA 29 CFR 1910.269 | Electric Power Generation, Transmission, and Distribution |
−| OSHA 29 CFR 1910.333 | Selection and Use of Work Practices |
−| OSHA 29 CFR 1910.335 | Safeguards for Personnel Protection |
−| IEEE 551 | Recommended Practice for Calculating AC Short-Circuit Currents in Industrial and Commercial Power Systems (Violet Book) |
−| ANSI/IEEE C37.010 | Application Guide for AC High-Voltage Circuit Breakers Rated on a Symmetrical Current Basis |
−| ANSI/IEEE C37.13 | Low-Voltage AC Power Circuit Breakers Used in Enclosures |
−| IEEE 242 | Recommended Practice for Protection and Coordination of Industrial and Commercial Power Systems (Buff Book) |
−| ANSI Z535.4 | Product Safety Signs and Labels |
−| UL 969 | Marking and Labeling Systems |
−
−NFPA 70E is the dominant authority for the worker-facing portion of the analysis (PPE, boundaries, labels, work practices). IEEE 1584 is the dominant authority for the calculation methodology that produces the incident energy and boundary values used by NFPA 70E. OSHA 29 CFR Subpart S references both and is the enforceable federal requirement in the United States.
−
−# Submittals
−
−## Action Submittals
−
−Contractor or the Engineer of Record shall submit the following for review prior to performing the analysis. The objective is to confirm the analyst, the methodology, and the scope before fieldwork or modeling effort is committed, so that disagreements over scope do not surface only after the report is delivered.
−
−- Qualifications of the analyst, including degree, professional engineering registration, and a record of comparable completed studies
−- Identification of the calculation software, version, and the IEEE 1584 model edition the software implements
−- A scope statement listing every bus, switchboard, panelboard, motor control center, switchgear lineup, transformer, and other equipment to be included, and explicit identification of any equipment excluded from the study with justification
−- A list of source data the analyst will rely on, including utility short-circuit data, equipment nameplates, conductor sizes and lengths, and protective device settings
−- A field-survey plan for any data that must be collected on site
−- A draft single-line diagram showing the level of detail to be modeled, including where the model terminates at downstream branches
−- A proposed label format compliant with NFPA 70E 130.5(H) and any Owner-specific label requirements
−- A schedule milestone for delivery of the calculation report, draft labels, and final labels
−
−```datasheet
−label: Action Submittals Required
−type: checkbox
−options:
− - "Analyst qualifications and PE registration"
− - "Calculation software identification and version"
− - "Study scope statement (included / excluded equipment)"
− - "Source data list and field-survey plan"
− - "Draft single-line diagram for modeling"
− - "Proposed label format and content"
− - "Delivery schedule"
−default: "Analyst qualifications and PE registration"
−```
−
−## Closeout Submittals
−
−Contractor shall provide the following at substantial completion. The closeout submittal is the documentation that the Owner will rely on for the life of the installation, and shall be delivered in a form that can be re-opened and edited when the study is updated.
−
−- Final arc-flash calculation report, sealed by a registered professional engineer
−- Native calculation-software project file (not only a PDF export) so that future updates can be performed without rebuilding the model
−- Final single-line diagram with bus identifiers matching the report and the labels
−- Bus-by-bus results table including bolted-fault current, arcing current, arc duration, working distance, incident energy at the working distance, arc-flash boundary, and the required PPE category or arc-rating
−- A copy of each installed label with its corresponding bus identifier
−- Photographs of installed labels on each piece of equipment
−- A statement of the date of the study, the protective device settings the calculation assumed, and the utility fault current the calculation assumed
−
−# Quality Assurance
−
−## Analyst Qualifications
−
−The arc-flash analysis shall be performed under the responsible charge of a registered professional engineer with documented experience performing arc-flash studies to IEEE 1584. The analyst shall have completed a minimum of five comparable studies for facilities of similar size and voltage class, and shall be familiar with both the calculation methodology and the practical realities of field data collection.
−
−The analyst is not required to be the same engineer who designed the electrical system, and there are arguments both ways. An independent analyst brings fresh eyes and is less likely to confirm the designer's assumptions; the designer of record has the most complete knowledge of the system and the fewest unknowns. Either is acceptable provided the qualifications are met.
−
−```datasheet
−label: Analyst Relationship to Design Team
−type: radio
−options:
− - "Engineer of Record performs the study"
− - "Independent third-party engineer performs the study"
− - "Manufacturer-provided study (subject to independent review)"
−default: "Independent third-party engineer performs the study"
−```
−
−A manufacturer-provided study, where the switchgear or distribution equipment manufacturer offers an arc-flash study as part of the equipment package, is acceptable only where the manufacturer also models the upstream utility source and the downstream branches that affect arcing current. A study limited to the manufacturer's own equipment lineup is not a complete facility study.
−
−## Calculation Software
−
−The analysis shall be performed in a software package that implements the IEEE 1584 calculation method to the edition specified in this standard. Hand calculations and spreadsheet implementations are not acceptable for a facility study because the IEEE 1584-2018 model has more than thirty equations selected and weighted by voltage range and electrode configuration, and propagating an error through a spreadsheet is too easy.
−
−```datasheet
−label: IEEE 1584 Calculation Edition
−type: radio
−options:
− - "IEEE 1584-2018 (current edition)"
− - "IEEE 1584-2002 with 2004a amendment (legacy)"
−default: "IEEE 1584-2018 (current edition)"
−```
−
−The 2018 edition shall be used for new studies. The 2002 edition's two-equation model has been replaced by a substantially different model that incorporates electrode configuration, enclosure size, and a broader empirical test database. Where an existing site has a 2002-edition study on file, the next periodic review shall convert the study to the 2018 model rather than continuing to update under the superseded edition. The 2002 model is identified here only so that a legacy study can be recognized on inspection; it shall not be the basis of a new analysis.
−
−# Methodology
−
−## IEEE 1584-2018 Model
−
−The IEEE 1584-2018 model calculates the arcing current, the arc duration, the incident energy at a working distance, and the arc-flash boundary as a function of bolted-fault current, system voltage, electrode configuration, enclosure dimensions, electrode gap, and working distance. The model is empirical, derived from arc-flash test data over a defined range of conditions, and is valid only within that range. For conditions outside the model range — for example, voltages below 208V, single-phase systems, DC systems, or open-air arcs in configurations not tested — alternative methods from NFPA 70E Annex D shall be applied and identified in the report.
−
−The voltage range of the 2018 model is 208V to 15kV. The bolted-fault-current range is 500A to 106kA for low-voltage equipment and 200A to 65kA for medium-voltage equipment. The electrode gap range is 6mm to 76mm (0.25 in. to 3 in.) for low voltage and 19mm to 254mm (0.75 in. to 10 in.) for medium voltage. The analyst shall confirm that every bus modeled lies within these ranges and shall document the alternative method used for any bus that does not.
−
−## Electrode Configuration
−
−IEEE 1584-2018 introduced explicit electrode configuration as an input to the calculation. The five configurations and their typical application are:
−
−| Configuration | Description | Typical Application |
−|---------------|-------------|---------------------|
−| VCB | Vertical electrodes inside a metal box enclosure | Most LV switchgear and switchboards |
−| VCBB | Vertical electrodes terminated in an insulating barrier inside a metal box | LV equipment with barrier between bus and cable compartment |
−| HCB | Horizontal electrodes inside a metal box enclosure | Some LV switchgear designs; many MV configurations |
−| VOA | Vertical electrodes in open air | Open-frame substations, exposed bus, cable terminations in open air |
−| HOA | Horizontal electrodes in open air | Open-frame substations with horizontal bus |
−
−For identical electrical conditions, electrode configuration alone can change the calculated incident energy by a factor of four or more. The analyst shall select the configuration that matches the actual equipment construction, not the most conservative configuration as a default. Selecting VCBB for every bus inflates incident energy uniformly, masks the equipment where mitigation would actually pay off, and drives unnecessary PPE category increases. The configuration shall be documented in the bus-by-bus results table.
−
−```datasheet
−label: Electrode Configuration Selection Basis
−type: radio
−options:
− - "Per equipment construction (specific configuration for each bus)"
− - "Conservative default (VCBB for all LV, HCB for all MV)"
−default: "Per equipment construction (specific configuration for each bus)"
−```
−
−## Maximum and Minimum Arcing Current
−
−The analysis shall be performed at both the maximum and the minimum arcing current at each bus. Maximum arcing current produces the worst-case incident energy when the upstream device trips on its instantaneous element. Minimum arcing current — IEEE 1584-2018 specifies a 0.85 multiplier on the calculated arcing current for low voltage and 0.96 for medium voltage — is the lower-bound case in which the upstream device may not see enough current to trip instantaneously and clears instead on a longer time-delay band. The lower-bound case frequently produces a higher incident energy than the maximum case because the arc burns longer. The reported value at each bus shall be the higher of the two.
−
−This dual calculation is a frequent point of error in legacy 2002-edition studies, which used a single arcing-current value. A 2018-edition study that does not show both values in the bus-by-bus results has not been performed correctly.
−
−## Arc Duration
−
−Arc duration is the time from arc initiation to the moment the upstream device interrupts the current. It is the dominant variable in incident energy: doubling the duration doubles the incident energy. Arc duration shall be determined from the protective device's time-current characteristic at the calculated arcing current, plus the device's interrupting time.
−
−- For an instantaneous trip, duration is the relay or trip-unit operate time plus the breaker interrupting time, typically 3 to 5 cycles total for low-voltage power circuit breakers and 5 to 8 cycles for medium-voltage breakers
−- For a time-delayed trip, duration is the time read off the upstream device's time-current curve at the arcing current
−- Where the upstream device does not clear within 2 seconds, NFPA 70E permits the analysis to assume a 2-second maximum on the basis that a worker can typically move out of the arc-flash zone in 2 seconds; the analyst shall document any bus where the 2-second cap is applied and shall flag those locations because the cap is a worker-movement assumption, not a device characteristic
−
−```datasheet
−label: 2-Second Maximum Arc Duration Cap
−type: radio
−options:
− - "Apply per IEEE 1584 / NFPA 70E (worker can move away)"
− - "Do not apply (use actual device clearing time)"
−default: "Apply per IEEE 1584 / NFPA 70E (worker can move away)"
−```
−
−The 2-second cap is defensible for accessible above-ground equipment in a normal working position. It is not defensible for a worker in a pit, in a confined space, on a ladder, or in any other location from which escape in 2 seconds is unlikely. The Engineer shall identify any such location during the study and shall override the cap for those buses.
−
−## Working Distance
−
−Working distance is the distance from the arc source to the worker's face and chest. Incident energy at the working distance is what the label reports and what the PPE shall protect against. IEEE 1584 provides typical working distances by equipment class.
−
−| Equipment Class | Typical Working Distance |
−|-----------------|--------------------------|
−| Low-voltage MCC and panelboards | 18 in. (455 mm) |
−| Low-voltage switchgear and switchboards | 24 in. (610 mm) |
−| Medium-voltage switchgear | 36 in. (910 mm) |
−| Cable | 18 in. (455 mm) |
−
−```datasheet
−label: Working Distance Basis
−type: radio
−options:
− - "IEEE 1584 typical values by equipment class"
− - "Task-specific working distance (justified per task)"
−default: "IEEE 1584 typical values by equipment class"
−```
−
−A task-specific working distance shorter than the typical value shall be used where the task being performed places the worker closer to the arc source than the typical value assumes. Voltage testing through a closed door at a near-distance window is the common example. The label shall report the incident energy at the working distance assumed in the calculation, and that distance shall be stated on the label.
−
−## Modeling Boundary
−
−The model shall extend from the utility source down to the lowest level of distribution at which workers will perform energized tasks. For most commercial and institutional buildings, the lowest level is the branch-circuit panelboard. For industrial facilities, the lowest level may be the individual motor disconnect or the MCC bucket. Equipment below the modeling boundary may be analyzed by inference from its upstream device, provided the inference is documented and the worker-facing label is conservative.
−
−```datasheet
−label: Downstream Modeling Limit
−type: select
−options:
− - "Every branch-circuit panelboard"
− - "Every MCC bucket and motor disconnect"
− - "Every distribution panelboard 100A and above"
− - "Every piece of equipment 240V and above"
− - "Project-specific (see scope statement)"
−default: "Every branch-circuit panelboard"
−```
−
−The Engineer shall set the downstream limit consistent with the work that will actually be performed energized. If electricians will open a 20A branch-circuit panelboard energized, that panelboard shall be modeled and labeled. If a class of equipment will never be opened energized, modeling and labeling it adds clutter and cost; the equipment shall instead be labeled with a generic warning and an instruction to de-energize before opening.
−
−## Equipment Below 240V
−
−IEEE 1584-2018 deprecated the 2002 edition's exemption for equipment below 240V served by transformers smaller than 125kVA. The 2018 edition recognizes that arcs can sustain at 208V given sufficient available current, and the analyst shall model these buses by the 2018 method. Where the calculated incident energy is low enough that the equipment does not need a hazard label, the equipment shall still be modeled in the report and the low-energy result documented; the report shall not assert that the equipment is exempt.
−
−# Input Data Requirements
−
−## Upstream of the Service
−
−```datasheet
−label: Utility Source Fault Current Data
−type: select
−options:
− - "Utility-provided three-phase and single-line-to-ground available fault current at the service"
− - "Utility-provided infinite-bus equivalent (with documented system X/R)"
− - "Assumed value pending utility confirmation"
−default: "Utility-provided three-phase and single-line-to-ground available fault current at the service"
−```
−
−Utility fault current shall be obtained in writing from the serving utility. An assumed value is acceptable for a preliminary study only and shall be reconciled before the labels are produced. The utility data shall include both the maximum available fault current (typically corresponding to the utility's design source) and, where the utility can provide it, a minimum available fault current corresponding to a single-source contingency on the utility side. The minimum value drives the minimum-arcing-current case described above.
−
−## Equipment Data
−
−The analyst shall collect, for every piece of modeled equipment, the data required by the IEEE 1584 model:
−
−- Nominal voltage and configuration (3-phase 3-wire, 3-phase 4-wire)
−- Frame size and short-circuit current rating
−- Enclosure dimensions (height, width, depth) where the equipment is enclosed
−- Bus gap (electrode spacing) per the manufacturer's published data
−- Electrode configuration (per the table above)
−- Conductor size, type, and length from the upstream source
−- Transformer kVA, impedance, and connection where transformers are within the model
−
−Enclosure dimensions and bus gap are new requirements introduced by the 2018 edition. They shall be obtained from the equipment manufacturer's published data or, where the equipment is in service and not documented, from physical measurement of representative units.
−
−```datasheet
−label: Equipment Data Collection Method
−type: radio
−options:
− - "Field survey by the analyst"
− - "Owner-provided equipment list (verified by spot-check field survey)"
− - "Manufacturer shop drawings (new construction)"
−default: "Field survey by the analyst"
−```
−
−For new construction, manufacturer shop drawings are the authoritative source. For an existing facility, a field survey by the analyst is the safest approach because nameplate ratings and as-installed configurations frequently diverge from the original record drawings.
−
−## Protective Device Settings
−
−Protective device settings shall be the as-set values from the coordination study, confirmed by field verification. The arc-flash analyst shall not assume settings or take settings from a design submittal that has not been confirmed in the field. Where the field verification finds a device set differently than the coordination study assumed, the discrepancy shall be resolved — either by adjusting the device to the studied setting or by re-running the arc-flash calculation with the as-found setting — before labels are produced.
−
−```datasheet
−label: Protective Device Setting Verification
−type: radio
−options:
− - "Field-verified settings (every device in the model)"
− - "Coordination-study settings (assumed installed correctly)"
−default: "Field-verified settings (every device in the model)"
−```
−
−# Maintenance Mode Analysis
−
−## Energy Reduction Methods
−
−Many modern circuit breakers and protective relays support an arc-energy reduction mode that, while engaged, reduces clearing time on the device's instantaneous element. NFPA 70 Article 240.87 requires that any circuit breaker rated 1200A or more, or any breaker with a continuous current setting of 1200A or more, employ one of the following methods to reduce arcing duration:
−
−- Zone-selective interlocking (ZSI)
−- Differential relaying
−- Energy-reducing maintenance switching (ERMS, also called arc-reduction maintenance switch or ARMS) with a local status indicator
−- Energy-reducing active arc-flash mitigation system
−- An instantaneous trip setting less than the available arcing current
−- An instantaneous override setting less than the available arcing current
−- An approved equivalent means
−
−```datasheet
−label: Arc Energy Reduction Method Applied to 1200A+ Breakers
−type: select
−options:
− - "Zone-selective interlocking (ZSI)"
− - "Differential relaying (87)"
− - "Energy-reducing maintenance switching (ERMS)"
− - "Energy-reducing active arc-flash mitigation system"
− - "Instantaneous trip setting below available arcing current"
− - "Approved equivalent"
−default: "Zone-selective interlocking (ZSI)"
−```
−
−Where ERMS is employed, the device has two distinct states: normal operation and maintenance mode. Incident energy is different in each state, and the analysis shall calculate and report both. The label shall show the incident energy in both states or, where the equipment is wired to require ERMS engagement before doors can be opened, shall show only the maintenance-mode value with a notation that the equipment requires ERMS engagement prior to interaction.
−
−```datasheet
−label: ERMS Reporting on Label
−type: radio
−options:
− - "Show both normal and maintenance-mode incident energy"
− - "Show maintenance-mode value only (ERMS required to interact)"
− - "Show normal-mode value only (ERMS not provided)"
−default: "Show both normal and maintenance-mode incident energy"
−```
−
−ZSI does not have a worker-engaged state in the same way ERMS does — it operates continuously — but the analysis shall confirm that ZSI is in fact active in the as-installed wiring. A ZSI scheme that has been disabled or whose interlock signal has been disconnected (a not-uncommon finding during field surveys) provides no benefit. The arc-flash report shall identify ZSI buses and recommend periodic functional verification of the interlock.
−
−## Other Operating States
−
−The analysis shall consider operating states that affect available fault current and clearing time:
−
−- Alternate-source operation (generator running, normal source unavailable)
−- Tie-breaker closed on multi-source systems
−- Bypass operation of a UPS or static switch
−- Maintenance bypass of a paralleling switchgear
−
−```datasheet
−label: Alternate Operating States Analyzed
−type: checkbox
−options:
− - "Normal utility source"
− - "Standby generator (utility unavailable)"
− - "Multi-source with tie closed"
− - "UPS bypass"
− - "Maintenance bypass / paralleling switchgear"
−default: "Normal utility source"
−```
−
−The reported incident energy at each bus shall be the worst-case value across all credible operating states. Where a state produces a higher incident energy only briefly during a transfer (for example, a momentary parallel during open-transition transfer testing), the analyst shall document the state and may exclude it if it is not a state in which workers will perform energized tasks.
−
−# Equipment Labeling Requirements
−
−## Required Label Content
−
−Per NFPA 70E 130.5(H), each piece of equipment within the scope of the study shall be field-marked with a label containing, at a minimum, the nominal system voltage, the arc-flash boundary, and at least one of the following: available incident energy and corresponding working distance, minimum arc rating of clothing, site-specific level of PPE, or hazard/risk category from the NFPA 70E task tables.
−
−This standard requires the incident-energy method for all labels. The PPE-category method is a tabular shortcut intended for sites that have not performed an engineering study, and a site that has performed the study should report its actual results.
−
−```datasheet
−label: Label Method
−type: radio
−options:
− - "Incident energy analysis method (engineered values)"
− - "PPE category method (NFPA 70E task tables)"
−default: "Incident energy analysis method (engineered values)"
−```
−
−```datasheet
−label: Minimum Label Content
−type: checkbox
−options:
− - "Nominal system voltage"
− - "Arc-flash boundary (distance)"
− - "Available incident energy (cal/cm²)"
− - "Working distance for the reported incident energy"
− - "Minimum arc rating of required PPE (cal/cm²)"
− - "Site-specific PPE description"
− - "Equipment identifier matching the single-line diagram"
− - "Date of the study"
− - "Engineer's seal or study report reference"
−default: "Nominal system voltage"
−```
−
−The 2024 edition of NFPA 70E explicitly prohibits showing both an incident-energy value and a PPE category from the task tables on the same label, because the two represent fundamentally different selection methods and showing both invites confusion. The label shall use one method consistently.
−
−## Label Format and Hazard Word
−
−The hazard signal word on the label shall be selected per ANSI Z535.4 and NFPA 70E based on the incident energy:
−
−| Incident Energy | Signal Word |
−|-----------------|-------------|
−| Up to 1.2 cal/cm² | CAUTION (no PPE required for typical tasks; verify the no-hazard task assumption) |
−| 1.2 to 40 cal/cm² | WARNING |
−| Greater than 40 cal/cm² | DANGER — no safe PPE available; equipment shall not be worked energized |
−
−```datasheet
−label: Label Signal Word Application
−type: radio
−options:
− - "Per ANSI Z535.4 / incident-energy thresholds above"
− - "Uniform WARNING on all labels (legacy practice)"
−default: "Per ANSI Z535.4 / incident-energy thresholds above"
−```
−
−Buses with incident energy above 40 cal/cm² are commonly labeled DANGER with a notation that no commercially available PPE provides reliable protection at that energy level. The Owner shall identify these buses in the electrical safety program and shall require de-energization before any work is performed.
−
−## Label Construction
−
−The label shall be of sufficient durability for the environment in which it is installed, per the 2024 edition of NFPA 70E. A label in a humid mechanical room, an outdoor switchyard, a chemical-process area, or a high-temperature switchgear room shall be specified for those conditions and shall not fade, peel, or become unreadable within the periodic review interval.
−
−```datasheet
−label: Label Material
−type: select
−options:
− - "Polyester with adhesive backing (indoor, conditioned space)"
− - "Vinyl with UV-resistant overlaminate (indoor industrial / unconditioned)"
− - "Engraved phenolic plate, mechanically fastened (outdoor / harsh environment)"
− - "Stainless steel with engraved or etched lettering (outdoor / corrosive)"
−default: "Polyester with adhesive backing (indoor, conditioned space)"
−```
−
−Adhesive-backed labels in unconditioned spaces commonly fail within five years from heat cycling and ultraviolet exposure. For outdoor switchyards, generator yards, and rooftop equipment, an engraved phenolic plate or stainless-steel label mechanically fastened to the equipment is the only construction with a useful life that matches the analysis review interval.
−
−```datasheet
−label: Label Mounting Method
−type: radio
−options:
− - "Adhesive on cleaned, dry equipment surface"
− - "Mechanical fasteners (screws or rivets)"
− - "Magnetic mount (movable equipment only)"
−default: "Adhesive on cleaned, dry equipment surface"
−```
−
−## Label Location
−
−Labels shall be installed on each piece of equipment in a location where they are visible to a worker before that worker opens, racks, or otherwise interacts with the equipment energized. For lineup equipment such as switchgear and motor control centers, a label shall be applied to each section, each individually drawable breaker, and each MCC bucket — not only to the equipment as a whole — because a worker may interact with one bucket without ever approaching the rest of the lineup.
−
−```datasheet
−label: Label Granularity
−type: select
−options:
− - "Per equipment lineup only"
− - "Per section (vertical section of switchgear, column of MCC)"
− - "Per individual device (each breaker, each bucket)"
−default: "Per section (vertical section of switchgear, column of MCC)"
−```
−
−Per-section labeling is the practical compromise for most installations and is the basis for the cost and label-count estimates in the study. Per-device labeling is required by some Owner safety programs and shall be specified at the start of the project; retrofitting per-device labels after a per-section study has been completed approximately doubles the label count and is best avoided.
−
−The label location on each piece of equipment shall be repeatable and shall not be obscured by handles, hinges, latches, or routine maintenance hardware. Where the equipment door swings outward, the label shall be on the door at the worker's eye level; where the worker approaches the equipment from the side, the label shall be on the side panel.
−
−[[drawing: Label placement details on representative equipment types — switchgear section, MCC column, panelboard cover, transformer enclosure]]
−
−# Deliverables
−
−The deliverable set for the arc-flash study comprises three artifacts that shall be consistent with each other in every value.
−
−## Calculation Report
−
−The report shall include, at minimum:
−
−- Executive summary identifying the highest-incident-energy buses and the buses where incident energy exceeds 40 cal/cm²
−- System description with single-line diagram, bus identifiers, and the modeling boundary
−- Utility data source and date
−- Equipment data sources (field survey, manufacturer data, shop drawings)
−- Protective device settings table with the source of each setting (coordination study, field-verified, etc.)
−- Methodology statement identifying the IEEE 1584 edition, electrode configurations applied, working distances used, and any departures from the standard methodology
−- Bus-by-bus results table with bolted-fault current, arcing current (both max and min cases), arc duration, working distance, incident energy at the working distance, arc-flash boundary, label signal word, and required PPE
−- Mitigation recommendations for any bus where reasonable design changes could lower the incident energy meaningfully
−- Statement of assumptions and the conditions under which the study shall be reviewed or re-run
−- Engineer's seal and signature
−
−## Labels
−
−The physical labels shall match the report values exactly. A discrepancy between the report and a label is a finding against the study and shall be corrected before closeout.
−
−## Single-Line Diagram
−
−The single-line diagram delivered with the study shall identify every modeled bus by the same identifier used on the labels and in the report. The diagram shall be maintained as a controlled document for the life of the facility and shall be updated whenever the study is updated.
−
−# Worker Training Coordination
−
−The arc-flash study is an input to the Owner's electrical safety program, not a substitute for it. NFPA 70E requires that workers who perform tasks on or near energized equipment be trained as qualified persons, that they be familiar with the labels installed on equipment they will interact with, and that they be retrained at intervals not exceeding three years.
−
−The Contractor's responsibility under this standard ends at the delivery of the labels and the report. The Owner is responsible for incorporating the study results into worker training, energized-work permitting, PPE selection, and the periodic-review schedule. The study shall identify, in its mitigation recommendations, any task-specific PPE that requires specification of a particular arc-rating beyond commodity electrical PPE; the Owner shall procure that PPE before workers are permitted to perform the affected tasks.
−
−```datasheet
−label: Owner Training Coordination
−type: checkbox
−options:
− - "Worker training on label interpretation"
− - "Energized-work permitting procedure references study"
− - "PPE inventory matched to study results"
− - "Periodic-review schedule established"
−default: "Worker training on label interpretation"
−```
−
−# Re-Study Triggers
−
−NFPA 70E 130.5(G) requires that the arc-flash risk assessment be reviewed periodically at intervals not exceeding five years, and reviewed whenever changes occur that could affect the analysis. The Owner shall maintain a record of the study date on every label and shall track the next review date in the facility records.
−
−A review at the five-year interval is not necessarily a full recalculation. The reviewer shall confirm that none of the conditions below has changed since the prior study. Where none has changed, the existing study and labels remain in effect and the next review date is set five years forward. Where any condition has changed, the affected portion of the study shall be re-run and new labels produced for the affected buses.
−
−```datasheet
−label: Conditions Triggering Re-Study Before the Five-Year Interval
−type: checkbox
−options:
− - "Utility available fault current change (notified by utility)"
− - "Service or main equipment replacement or upgrade"
− - "Protective device settings change (any device in the model)"
− - "Protective device replacement (new make or model)"
− - "Addition of significant new load (motors, transformers, generation)"
− - "Addition or removal of on-site generation"
− - "Configuration change (tie operation, bypass routing)"
− - "Discovery of a field condition inconsistent with the modeled assumptions"
−default: "Utility available fault current change (notified by utility)"
−```
−
−Utility fault current change is the trigger most commonly missed. Utilities increase available fault current as they reinforce their distribution system, and the increase is not always communicated to the customer. As part of the five-year review, the Owner shall request updated available fault current data from the serving utility and compare it to the value used in the study; any material increase requires re-running the study.
−
−A protective device replacement is the second commonly missed trigger. A breaker swapped in kind during routine maintenance is rarely a problem; a breaker replaced with one of different manufacture or trip-unit family may have substantially different clearing characteristics and shall be re-evaluated. The Owner's maintenance procedures shall include notification of the responsible engineer when a protective device in the arc-flash model is replaced.
−
−```datasheet
−label: Periodic Review Interval
−type: select
−options:
− - "5 years (NFPA 70E maximum)"
− - "3 years (conservative)"
− - "Annual (high-change facilities)"
−default: "5 years (NFPA 70E maximum)"
−```
−
−A 5-year interval is the NFPA 70E maximum and is appropriate for stable facilities with documented change-management procedures. A shorter interval is appropriate where the facility undergoes frequent reconfiguration, where on-site generation is added incrementally, or where the Owner's change-management procedures do not reliably capture electrical-system modifications.
−
−# Mitigation Hierarchy
−
−The study report shall identify mitigation options for buses with incident energy that would require Category 3 (25 cal/cm²) or higher PPE, or that exceed 40 cal/cm². Mitigation shall be evaluated in the following order, which corresponds to the hierarchy of controls in NFPA 70E and reflects effectiveness from most to least:
−
−1. Eliminate the need to work on the equipment energized (de-energize, lock out, verify)
−2. Substitute the equipment for a design with lower arcing characteristics (arc-resistant switchgear, current-limiting fuses upstream)
−3. Engineer the protective system for faster clearing (faster instantaneous, ZSI, ERMS, differential)
−4. Administrative controls (restrict tasks, increase working distance, require remote operation)
−5. PPE (last line of defense)
−
−```datasheet
−label: Mitigation Recommendations Provided In Report
−type: radio
−options:
− - "For every bus exceeding 8 cal/cm²"
− - "For every bus exceeding 25 cal/cm²"
− - "For every bus exceeding 40 cal/cm² only"
−default: "For every bus exceeding 25 cal/cm²"
−```
−
−The report shall present mitigation as engineering recommendations, not as design changes. The Owner and Engineer of Record shall decide which recommendations to implement; the analyst's role is to identify the options and the order-of-magnitude reduction each would achieve. Where a mitigation recommendation is adopted, the affected portion of the study shall be re-run with the changed conditions and new labels produced.
−
−# Field Verification
−
−Before the labels are released for installation, the Contractor shall verify that the field conditions match the study assumptions. The verification shall include, at minimum:
−
−- Protective device settings read at each device in the model and compared to the report's setting table
−- Available fault current at the service compared to the utility data used in the study
−- Equipment identifiers on the equipment match the identifiers used in the report
−- Any ERMS or similar maintenance-mode switches are functional and wired as the report assumes
−- Any ZSI interlock signals are continuous through every device in the scheme
−
−```datasheet
−label: Pre-Installation Verification
−type: checkbox
−options:
− - "Protective device settings verified at every device"
− - "Utility fault current re-confirmed at study delivery"
− - "Equipment identifier reconciliation"
− - "ERMS functional verification"
− - "ZSI continuity verification"
−default: "Protective device settings verified at every device"
−```
−
−Any discrepancy found during verification shall be resolved before labels are installed. Installing a label that does not match the as-installed condition is worse than no label at all, because it creates a false sense of protection.
−
−# Delivery, Storage, and Handling
−
−The calculation report, the native software project file, and the photographic record of installed labels shall be delivered to the Owner in both printed and electronic form. The electronic form shall be on durable media or in a managed document repository that the Owner controls. Reliance on a contractor's cloud storage account for the only copy of the study is not acceptable; the Owner shall be able to retrieve and edit the study without contacting the original analyst.
−
−Spare labels — at least one duplicate of each installed label — shall be delivered to the Owner for replacement of labels damaged in service. Spare labels shall be stored in the main electrical room or in another location identified in the closeout documentation.
−
−# Warranty
−
−The analyst shall warrant the analysis for accuracy at the time of issue, against the input data provided and the standards in force. The analyst is not responsible for changes in field conditions, utility fault current, or protective device settings that occur after the study is issued; those are the Owner's responsibility under the periodic-review program.
−
−```datasheet
−label: Analyst Warranty Period
−type: select
−options:
− - "1 year from report issue"
− - "Through the project warranty period"
− - "Through the first periodic review"
−default: "1 year from report issue"
−```
−
−The Contractor shall warrant the physical installation of the labels — adhesion, location, and correspondence between label content and the report — for the project warranty period. Labels that detach, fade, or are found to disagree with the report during the warranty period shall be replaced at no cost to the Owner.
+---
+title: Arc-Flash Hazard Analysis
+category: Electrical / Power Studies
+toc_depth: 3
+description: >
+ When to use: Engineering analysis to calculate incident energy and the arc-flash boundary at every piece of electrical equipment where workers may interact with the equipment while it is energized or while it could be placed into an electrically safe work condition. Applies to AC systems from 208V through medium voltage, in commercial, institutional, industrial, and healthcare facilities. The study produces equipment labels, PPE specifications, and the documentation that supports an NFPA 70E-compliant electrical safety program.
+ Not intended for: Short-circuit analysis on its own (see [[sync/short-circuit-study]]), protective device coordination on its own (see [[sync/protective-coordination-study]]), DC system arc-flash analysis (covered by NFPA 70E Article 130.5 informational annexes rather than IEEE 1584), arc-flash analysis of utility-owned equipment upstream of the service point, or development of the site's electrical safety work practices program itself (the study is an input to the program, not a substitute for it).
+---
+
+# Scope {toc}
+
+## This specification covers the engineering analysis required to determine the incident energy exposure and arc-flash boundary at each location in an electrical power system where a worker may interact with energized equipment, and to produce the equipment labels and the supporting documentation required by NFPA 70E and NFPA 70 (NEC).
+
+## The analysis shall be performed using the calculation methodology of IEEE 1584, current edition, supplemented for conditions outside the IEEE 1584 model range by methods identified in NFPA 70E Annex D.
+
+## An arc-flash hazard analysis is not a stand-alone study because incident energy at any bus depends on both the arcing current at that bus (a short-circuit problem) and on the clearing time of the protective device upstream (a coordination problem). {note}
+
+## The arc-flash study shall be performed only after the short-circuit study per [[sync/short-circuit-study]] and the protective device coordination study per [[sync/protective-coordination-study]] are complete and the protective device settings are finalized.
+
+## The arc-flash calculation shall not be re-run with assumed device settings and reconciled later, because an arc-flash label is only valid when the device that clears the arc has been set to the values used in the calculation.
+
+## The study deliverable is twofold: a calculation report documenting the system model, input data, methodology, and bus-by-bus results, and a set of physical labels installed on the equipment. {note}
+
+## The study shall produce a calculation report that documents the system model, the input data, the methodology, and the results bus-by-bus.
+
+## The study shall produce a set of physical labels installed on the equipment so that a worker about to open a door or remove a cover can read, in front of the equipment, the incident energy at the working distance, the arc-flash boundary, the nominal voltage, and the PPE required to perform the intended task.
+
+## Both the calculation report and the physical labels are required; neither substitutes for the other.
+
+## This standard does not establish the site's electrical safety program; it produces the technical inputs that the safety program relies on. {note}
+
+## The Owner remains responsible for adopting NFPA 70E (or an equivalent standard), training qualified workers, establishing energized-work permitting, providing and maintaining PPE, and reviewing the analysis on the schedule required by NFPA 70E.
+
+## Work practices and training shall be coordinated with [[sync/electrical-safety-program]].
+
+## Equipment scope shall be coordinated with [[sync/low-voltage-switchgear]], [[sync/medium-voltage-switchgear]], [[sync/low-voltage-switchboards]], [[sync/low-voltage-panelboards]], [[sync/motor-control-centers]], and [[sync/dry-type-transformers]].
+
+## The arc-flash study shall include every piece of equipment specified by the coordinated equipment standards that is within the analysis voltage threshold.
+
+# Referenced Standards {toc}
+
+## Analysis, labeling, and documentation shall comply with the latest adopted edition of the following standards and codes.
+
+| Standard | Title |
+|----------|-------|
+| IEEE 1584 | Guide for Performing Arc-Flash Hazard Calculations |
+| IEEE 1584.1 | Guide for the Specification of Scope and Deliverable Requirements for an Arc-Flash Hazard Calculation Study in Accordance with IEEE Std 1584 |
+| NFPA 70 | National Electrical Code (Articles 110.16, 130.5, 240.87) |
+| NFPA 70E | Standard for Electrical Safety in the Workplace |
+| OSHA 29 CFR 1910.269 | Electric Power Generation, Transmission, and Distribution |
+| OSHA 29 CFR 1910.333 | Selection and Use of Work Practices |
+| OSHA 29 CFR 1910.335 | Safeguards for Personnel Protection |
+| IEEE 551 | Recommended Practice for Calculating AC Short-Circuit Currents in Industrial and Commercial Power Systems (Violet Book) |
+| ANSI/IEEE C37.010 | Application Guide for AC High-Voltage Circuit Breakers Rated on a Symmetrical Current Basis |
+| ANSI/IEEE C37.13 | Low-Voltage AC Power Circuit Breakers Used in Enclosures |
+| IEEE 242 | Recommended Practice for Protection and Coordination of Industrial and Commercial Power Systems (Buff Book) |
+| ANSI Z535.4 | Product Safety Signs and Labels |
+| UL 969 | Marking and Labeling Systems |
+
+## Where the contract documents, the adopted edition of NFPA 70, or a referenced standard conflict, the more stringent requirement shall govern unless the Engineer of Record directs otherwise in writing.
+
+## NFPA 70E is the dominant authority for the worker-facing portion of the analysis (PPE, boundaries, labels, work practices), IEEE 1584 is the dominant authority for the calculation methodology, and OSHA 29 CFR Subpart S references both and is the enforceable federal requirement in the United States. {note}
+
+# Submittals {toc}
+
+## Action Submittals {toc}
+
+### Contractor or the Engineer of Record shall submit the following for review prior to performing the analysis, so that disagreements over scope do not surface only after the report is delivered:
+
+- Qualifications of the analyst, including degree, professional engineering registration, and a record of comparable completed studies
+- Identification of the calculation software, version, and the IEEE 1584 model edition the software implements
+- A scope statement listing every bus, switchboard, panelboard, motor control center, switchgear lineup, transformer, and other equipment to be included, and explicit identification of any equipment excluded from the study with justification
+- A list of source data the analyst will rely on, including utility short-circuit data, equipment nameplates, conductor sizes and lengths, and protective device settings
+- A field-survey plan for any data that must be collected on site
+- A draft single-line diagram showing the level of detail to be modeled, including where the model terminates at downstream branches
+- A proposed label format compliant with NFPA 70E 130.5(H) and any Owner-specific label requirements
+- A schedule milestone for delivery of the calculation report, draft labels, and final labels
+
+```datasheet
+label: Action Submittals Required
+type: checkbox
+options:
+ - "Analyst qualifications and PE registration"
+ - "Calculation software identification and version"
+ - "Study scope statement (included / excluded equipment)"
+ - "Source data list and field-survey plan"
+ - "Draft single-line diagram for modeling"
+ - "Proposed label format and content"
+ - "Delivery schedule"
+default: "Analyst qualifications and PE registration"
+```
+
+## Closeout Submittals {toc}
+
+### Contractor shall provide the following at substantial completion, delivered in a form that can be re-opened and edited when the study is updated:
+
+- Final arc-flash calculation report, sealed by a registered professional engineer
+- Native calculation-software project file (not only a PDF export) so that future updates can be performed without rebuilding the model
+- Final single-line diagram with bus identifiers matching the report and the labels
+- Bus-by-bus results table including bolted-fault current, arcing current, arc duration, working distance, incident energy at the working distance, arc-flash boundary, and the required PPE category or arc-rating
+- A copy of each installed label with its corresponding bus identifier
+- Photographs of installed labels on each piece of equipment
+- A statement of the date of the study, the protective device settings the calculation assumed, and the utility fault current the calculation assumed
+
+```datasheet
+label: Closeout Submittals Required
+type: checkbox
+options:
+ - "Final sealed arc-flash calculation report"
+ - "Native calculation-software project file"
+ - "Final single-line diagram with matching bus identifiers"
+ - "Bus-by-bus results table"
+ - "Copy of each installed label with bus identifier"
+ - "Photographs of installed labels"
+ - "Statement of study date and assumed settings / fault current"
+default: [Final sealed arc-flash calculation report, Native calculation-software project file, Final single-line diagram with matching bus identifiers, Bus-by-bus results table, Copy of each installed label with bus identifier, Photographs of installed labels, Statement of study date and assumed settings / fault current]
+```
+
+# Quality Assurance {toc}
+
+## Analyst Qualifications {toc}
+
+```datasheet
+label: Analyst Relationship to Design Team
+type: radio
+options:
+ - "Engineer of Record performs the study"
+ - "Independent third-party engineer performs the study"
+ - "Manufacturer-provided study (subject to independent review)"
+default: "Independent third-party engineer performs the study"
+```
+
+### The arc-flash analysis shall be performed under the responsible charge of a registered professional engineer with documented experience performing arc-flash studies to IEEE 1584.
+
+### The analyst shall have completed a minimum of five comparable studies for facilities of similar size and voltage class.
+
+### The analyst shall be familiar with both the calculation methodology and the practical realities of field data collection.
+
+### The analyst is not required to be the same engineer who designed the electrical system; an independent analyst brings fresh eyes while the designer of record has the most complete knowledge of the system, and either is acceptable provided the qualifications are met. {note}
+
+### A manufacturer-provided study is acceptable only where the manufacturer also models the upstream utility source and the downstream branches that affect arcing current.
+
+### A study limited to the manufacturer's own equipment lineup is not a complete facility study.
+
+## Calculation Software {toc}
+
+```datasheet
+label: IEEE 1584 Calculation Edition
+type: radio
+options:
+ - "IEEE 1584-2018 (current edition)"
+ - "IEEE 1584-2002 with 2004a amendment (legacy)"
+default: "IEEE 1584-2018 (current edition)"
+```
+
+### The analysis shall be performed in a software package that implements the IEEE 1584 calculation method to the edition specified in this standard.
+
+### Hand calculations and spreadsheet implementations are not acceptable for a facility study.
+
+### The IEEE 1584-2018 model has more than thirty equations selected and weighted by voltage range and electrode configuration, and propagating an error through a spreadsheet is too easy. {note}
+
+### The 2018 edition shall be used for new studies.
+
+### Where an existing site has a 2002-edition study on file, the next periodic review shall convert the study to the 2018 model rather than continuing to update under the superseded edition.
+
+### The 2002 edition's two-equation model has been replaced by a substantially different model that incorporates electrode configuration, enclosure size, and a broader empirical test database, and is identified here only so that a legacy study can be recognized on inspection. {note}
+
+### The 2002 model shall not be the basis of a new analysis.
+
+# Methodology {toc}
+
+## IEEE 1584-2018 Model {toc}
+
+### The IEEE 1584-2018 model calculates the arcing current, the arc duration, the incident energy at a working distance, and the arc-flash boundary as a function of bolted-fault current, system voltage, electrode configuration, enclosure dimensions, electrode gap, and working distance. {note}
+### The model is empirical and is valid only within the range of conditions from which it was derived. {note}
+
+### For conditions outside the model range — for example, voltages below 208V, single-phase systems, DC systems, or open-air arcs in configurations not tested — alternative methods from NFPA 70E Annex D shall be applied and identified in the report.
+
+### The voltage range of the 2018 model is 208V to 15kV. {note}
+
+### The bolted-fault-current range is 500A to 106kA for low-voltage equipment and 200A to 65kA for medium-voltage equipment. {note}
+
+### The electrode gap range is 6mm to 76mm (0.25 in. to 3 in.) for low voltage and 19mm to 254mm (0.75 in. to 10 in.) for medium voltage. {note}
+
+### The analyst shall confirm that every bus modeled lies within the model's voltage, bolted-fault-current, and electrode-gap ranges.
+
+### The analyst shall document the alternative method used for any bus that does not lie within the model's ranges.
+
+## Electrode Configuration {toc}
+
+### IEEE 1584-2018 introduced explicit electrode configuration as an input to the calculation. {note}
+### The five configurations and their typical application are: {note}
+
+| Configuration | Description | Typical Application |
+|---------------|-------------|---------------------|
+| VCB | Vertical electrodes inside a metal box enclosure | Most LV switchgear and switchboards |
+| VCBB | Vertical electrodes terminated in an insulating barrier inside a metal box | LV equipment with barrier between bus and cable compartment |
+| HCB | Horizontal electrodes inside a metal box enclosure | Some LV switchgear designs; many MV configurations |
+| VOA | Vertical electrodes in open air | Open-frame substations, exposed bus, cable terminations in open air |
+| HOA | Horizontal electrodes in open air | Open-frame substations with horizontal bus |
+
+```datasheet
+label: Electrode Configuration Selection Basis
+type: radio
+options:
+ - "Per equipment construction (specific configuration for each bus)"
+ - "Conservative default (VCBB for all LV, HCB for all MV)"
+default: "Per equipment construction (specific configuration for each bus)"
+```
+
+### For identical electrical conditions, electrode configuration alone can change the calculated incident energy by a factor of four or more, and selecting VCBB for every bus inflates incident energy uniformly, masks the equipment where mitigation would pay off, and drives unnecessary PPE category increases. {note}
+
+### The analyst shall select the electrode configuration that matches the actual equipment construction, not the most conservative configuration as a default.
+
+### The electrode configuration shall be documented in the bus-by-bus results table.
+
+## Maximum and Minimum Arcing Current {toc}
+
+### The analysis shall be performed at both the maximum and the minimum arcing current at each bus.
+
+### Maximum arcing current produces the worst-case incident energy when the upstream device trips on its instantaneous element, while minimum arcing current — a 0.85 multiplier for low voltage and 0.96 for medium voltage — is the lower-bound case in which the upstream device may clear on a longer time-delay band and the arc burns longer. {note}
+
+### The reported value at each bus shall be the higher of the maximum-arcing-current and minimum-arcing-current results.
+
+### A 2018-edition study that does not show both the maximum and minimum arcing-current values in the bus-by-bus results has not been performed correctly.
+
+### The dual maximum/minimum calculation is a frequent point of error in legacy 2002-edition studies, which used a single arcing-current value. {note}
+
+## Arc Duration {toc}
+
+### Arc duration is the time from arc initiation to the moment the upstream device interrupts the current. {note}
+### It is the dominant variable in incident energy: doubling the duration doubles the incident energy. {note}
+
+```datasheet
+label: 2-Second Maximum Arc Duration Cap
+type: radio
+options:
+ - "Apply per IEEE 1584 / NFPA 70E (worker can move away)"
+ - "Do not apply (use actual device clearing time)"
+default: "Apply per IEEE 1584 / NFPA 70E (worker can move away)"
+```
+
+### Arc duration shall be determined from the protective device's time-current characteristic at the calculated arcing current, plus the device's interrupting time.
+
+### For an instantaneous trip, duration is the relay or trip-unit operate time plus the breaker interrupting time, typically 3 to 5 cycles total for low-voltage power circuit breakers and 5 to 8 cycles for medium-voltage breakers.
+
+### For a time-delayed trip, duration is the time read off the upstream device's time-current curve at the arcing current.
+
+### Where the upstream device does not clear within 2 seconds, NFPA 70E permits the analysis to assume a 2-second maximum on the basis that a worker can typically move out of the arc-flash zone in 2 seconds.
+
+### The analyst shall document any bus where the 2-second cap is applied and shall flag those locations because the cap is a worker-movement assumption, not a device characteristic.
+
+### The 2-second cap is defensible for accessible above-ground equipment in a normal working position, but not for a worker in a pit, in a confined space, on a ladder, or in any other location from which escape in 2 seconds is unlikely. {note}
+
+### The Engineer shall identify any location from which escape in 2 seconds is unlikely during the study and shall override the 2-second cap for those buses.
+
+## Working Distance {toc}
+
+### Working distance is the distance from the arc source to the worker's face and chest. {note}
+### Incident energy at the working distance is what the label reports and what the PPE shall protect against.
+### IEEE 1584 provides typical working distances by equipment class. {note}
+
+| Equipment Class | Typical Working Distance |
+|-----------------|--------------------------|
+| Low-voltage MCC and panelboards | 18 in. (455 mm) |
+| Low-voltage switchgear and switchboards | 24 in. (610 mm) |
+| Medium-voltage switchgear | 36 in. (910 mm) |
+| Cable | 18 in. (455 mm) |
+
+```datasheet
+label: Working Distance Basis
+type: radio
+options:
+ - "IEEE 1584 typical values by equipment class"
+ - "Task-specific working distance (justified per task)"
+default: "IEEE 1584 typical values by equipment class"
+```
+
+### A task-specific working distance shorter than the typical value shall be used where the task being performed places the worker closer to the arc source than the typical value assumes.
+
+### The label shall report the incident energy at the working distance assumed in the calculation, and that distance shall be stated on the label.
+
+## Modeling Boundary {toc}
+
+```datasheet
+label: Downstream Modeling Limit
+type: select
+options:
+ - "Every branch-circuit panelboard"
+ - "Every MCC bucket and motor disconnect"
+ - "Every distribution panelboard 100A and above"
+ - "Every piece of equipment 240V and above"
+ - "Project-specific (see scope statement)"
+default: "Every branch-circuit panelboard"
+```
+
+### The model shall extend from the utility source down to the lowest level of distribution at which workers will perform energized tasks.
+
+### Equipment below the modeling boundary may be analyzed by inference from its upstream device, provided the inference is documented and the worker-facing label is conservative.
+
+### The Engineer shall set the downstream limit consistent with the work that will actually be performed energized.
+
+### Where a class of equipment will never be opened energized, that equipment shall instead be labeled with a generic warning and an instruction to de-energize before opening.
+
+## Equipment Below 240V {toc}
+
+### The analyst shall model buses below 240V by the 2018 method, because the 2018 edition deprecated the 2002 edition's exemption for equipment below 240V served by transformers smaller than 125kVA and recognizes that arcs can sustain at 208V given sufficient available current.
+
+### Where the calculated incident energy is low enough that the equipment does not need a hazard label, the equipment shall still be modeled in the report and the low-energy result documented.
+
+### The report shall not assert that equipment below 240V is exempt.
+
+# Input Data Requirements {toc}
+
+## Upstream of the Service {toc}
+
+```datasheet
+label: Utility Source Fault Current Data
+type: select
+options:
+ - "Utility-provided three-phase and single-line-to-ground available fault current at the service"
+ - "Utility-provided infinite-bus equivalent (with documented system X/R)"
+ - "Assumed value pending utility confirmation"
+default: "Utility-provided three-phase and single-line-to-ground available fault current at the service"
+```
+
+### Utility fault current shall be obtained in writing from the serving utility.
+
+### An assumed value is acceptable for a preliminary study only and shall be reconciled before the labels are produced.
+
+### The utility data shall include both the maximum available fault current and, where the utility can provide it, a minimum available fault current corresponding to a single-source contingency on the utility side, which drives the minimum-arcing-current case.
+
+## Equipment Data {toc}
+
+### The analyst shall collect, for every piece of modeled equipment, the data required by the IEEE 1584 model:
+
+- Nominal voltage and configuration (3-phase 3-wire, 3-phase 4-wire)
+- Frame size and short-circuit current rating
+- Enclosure dimensions (height, width, depth) where the equipment is enclosed
+- Bus gap (electrode spacing) per the manufacturer's published data
+- Electrode configuration (per the table above)
+- Conductor size, type, and length from the upstream source
+- Transformer kVA, impedance, and connection where transformers are within the model
+
+```datasheet
+label: Equipment Data Collection Method
+type: radio
+options:
+ - "Field survey by the analyst"
+ - "Owner-provided equipment list (verified by spot-check field survey)"
+ - "Manufacturer shop drawings (new construction)"
+default: "Field survey by the analyst"
+```
+
+### Enclosure dimensions and bus gap, new requirements introduced by the 2018 edition, shall be obtained from the equipment manufacturer's published data or, where the equipment is in service and not documented, from physical measurement of representative units.
+
+### For new construction, manufacturer shop drawings are the authoritative source. {note}
+
+### For an existing facility, a field survey by the analyst is the safest approach because nameplate ratings and as-installed configurations frequently diverge from the original record drawings. {note}
+
+## Protective Device Settings {toc}
+
+```datasheet
+label: Protective Device Setting Verification
+type: radio
+options:
+ - "Field-verified settings (every device in the model)"
+ - "Coordination-study settings (assumed installed correctly)"
+default: "Field-verified settings (every device in the model)"
+```
+
+### Protective device settings shall be the as-set values from the coordination study, confirmed by field verification.
+
+### The arc-flash analyst shall not assume settings or take settings from a design submittal that has not been confirmed in the field.
+
+### Where the field verification finds a device set differently than the coordination study assumed, the discrepancy shall be resolved — either by adjusting the device to the studied setting or by re-running the arc-flash calculation with the as-found setting — before labels are produced.
+
+# Maintenance Mode Analysis {toc}
+
+## Energy Reduction Methods {toc}
+
+### NFPA 70 Article 240.87 requires that any circuit breaker rated 1200A or more, or any breaker with a continuous current setting of 1200A or more, employ one of the following methods to reduce arcing duration: {note}
+
+- Zone-selective interlocking (ZSI)
+- Differential relaying
+- Energy-reducing maintenance switching (ERMS, also called arc-reduction maintenance switch or ARMS) with a local status indicator
+- Energy-reducing active arc-flash mitigation system
+- An instantaneous trip setting less than the available arcing current
+- An instantaneous override setting less than the available arcing current
+- An approved equivalent means
+
+```datasheet
+label: Arc Energy Reduction Method Applied to 1200A+ Breakers
+type: select
+options:
+ - "Zone-selective interlocking (ZSI)"
+ - "Differential relaying (87)"
+ - "Energy-reducing maintenance switching (ERMS)"
+ - "Energy-reducing active arc-flash mitigation system"
+ - "Instantaneous trip setting below available arcing current"
+ - "Approved equivalent"
+default: "Zone-selective interlocking (ZSI)"
+```
+
+```datasheet
+label: ERMS Reporting on Label
+type: radio
+options:
+ - "Show both normal and maintenance-mode incident energy"
+ - "Show maintenance-mode value only (ERMS required to interact)"
+ - "Show normal-mode value only (ERMS not provided)"
+default: "Show both normal and maintenance-mode incident energy"
+```
+
+### Where ERMS is employed, the device has two distinct states with different incident energy, and the analysis shall calculate and report the incident energy in both the normal-operation and maintenance-mode states.
+
+### The label shall show the incident energy in both states or, where the equipment is wired to require ERMS engagement before doors can be opened, shall show only the maintenance-mode value with a notation that the equipment requires ERMS engagement prior to interaction.
+
+### ZSI operates continuously and does not have a worker-engaged state in the same way ERMS does, but a ZSI scheme that has been disabled or whose interlock signal has been disconnected provides no benefit. {note}
+
+### The analysis shall confirm that ZSI is in fact active in the as-installed wiring.
+
+### The arc-flash report shall identify ZSI buses and recommend periodic functional verification of the interlock.
+
+## Other Operating States {toc}
+
+### The analysis shall consider operating states that affect available fault current and clearing time:
+
+- Alternate-source operation (generator running, normal source unavailable)
+- Tie-breaker closed on multi-source systems
+- Bypass operation of a UPS or static switch
+- Maintenance bypass of a paralleling switchgear
+
+```datasheet
+label: Alternate Operating States Analyzed
+type: checkbox
+options:
+ - "Normal utility source"
+ - "Standby generator (utility unavailable)"
+ - "Multi-source with tie closed"
+ - "UPS bypass"
+ - "Maintenance bypass / paralleling switchgear"
+default: "Normal utility source"
+```
+
+### The reported incident energy at each bus shall be the worst-case value across all credible operating states.
+
+### Where a state produces a higher incident energy only briefly during a transfer, the analyst shall document the state and may exclude it if it is not a state in which workers will perform energized tasks.
+
+# Equipment Labeling Requirements {toc}
+
+## Required Label Content {toc}
+
+```datasheet
+label: Label Method
+type: radio
+options:
+ - "Incident energy analysis method (engineered values)"
+ - "PPE category method (NFPA 70E task tables)"
+default: "Incident energy analysis method (engineered values)"
+```
+
+```datasheet
+label: Minimum Label Content
+type: checkbox
+options:
+ - "Nominal system voltage"
+ - "Arc-flash boundary (distance)"
+ - "Available incident energy (cal/cm²)"
+ - "Working distance for the reported incident energy"
+ - "Minimum arc rating of required PPE (cal/cm²)"
+ - "Site-specific PPE description"
+ - "Equipment identifier matching the single-line diagram"
+ - "Date of the study"
+ - "Engineer's seal or study report reference"
+default: "Nominal system voltage"
+```
+
+### Per NFPA 70E 130.5(H), each piece of equipment within the scope of the study shall be field-marked with a label containing, at a minimum, the nominal system voltage, the arc-flash boundary, and at least one of the following: available incident energy and corresponding working distance, minimum arc rating of clothing, site-specific level of PPE, or hazard/risk category from the NFPA 70E task tables.
+
+### This standard requires the incident-energy method for all labels, because a site that has performed the engineering study should report its actual results rather than the PPE-category tabular shortcut. {note}
+
+### The label shall use one selection method consistently, because the 2024 edition of NFPA 70E explicitly prohibits showing both an incident-energy value and a PPE category from the task tables on the same label.
+
+## Label Format and Hazard Word {toc}
+
+### The hazard signal word on the label shall be selected per ANSI Z535.4 and NFPA 70E based on the incident energy:
+
+| Incident Energy | Signal Word |
+|-----------------|-------------|
+| Up to 1.2 cal/cm² | CAUTION (no PPE required for typical tasks; verify the no-hazard task assumption) |
+| 1.2 to 40 cal/cm² | WARNING |
+| Greater than 40 cal/cm² | DANGER — no safe PPE available; equipment shall not be worked energized |
+
+```datasheet
+label: Label Signal Word Application
+type: radio
+options:
+ - "Per ANSI Z535.4 / incident-energy thresholds above"
+ - "Uniform WARNING on all labels (legacy practice)"
+default: "Per ANSI Z535.4 / incident-energy thresholds above"
+```
+
+### Buses with incident energy above 40 cal/cm² shall be labeled DANGER with a notation that no commercially available PPE provides reliable protection at that energy level.
+
+### The Owner shall identify the buses with incident energy above 40 cal/cm² in the electrical safety program and shall require de-energization before any work is performed.
+
+## Label Construction {toc}
+
+```datasheet
+label: Label Material
+type: select
+options:
+ - "Polyester with adhesive backing (indoor, conditioned space)"
+ - "Vinyl with UV-resistant overlaminate (indoor industrial / unconditioned)"
+ - "Engraved phenolic plate, mechanically fastened (outdoor / harsh environment)"
+ - "Stainless steel with engraved or etched lettering (outdoor / corrosive)"
+default: "Polyester with adhesive backing (indoor, conditioned space)"
+```
+
+```datasheet
+label: Label Mounting Method
+type: radio
+options:
+ - "Adhesive on cleaned, dry equipment surface"
+ - "Mechanical fasteners (screws or rivets)"
+ - "Magnetic mount (movable equipment only)"
+default: "Adhesive on cleaned, dry equipment surface"
+```
+
+### A label in a humid mechanical room, an outdoor switchyard, a chemical-process area, or a high-temperature switchgear room shall be of sufficient durability for that environment per the 2024 edition of NFPA 70E, and shall not fade, peel, or become unreadable within the periodic review interval.
+
+### Adhesive-backed labels in unconditioned spaces commonly fail within five years from heat cycling and ultraviolet exposure. {note}
+
+### For outdoor switchyards, generator yards, and rooftop equipment, an engraved phenolic plate or stainless-steel label mechanically fastened to the equipment shall be specified.
+
+## Label Location {toc}
+
+```datasheet
+label: Label Granularity
+type: select
+options:
+ - "Per equipment lineup only"
+ - "Per section (vertical section of switchgear, column of MCC)"
+ - "Per individual device (each breaker, each bucket)"
+default: "Per section (vertical section of switchgear, column of MCC)"
+```
+
+### Labels shall be installed on each piece of equipment in a location where they are visible to a worker before that worker opens, racks, or otherwise interacts with the equipment energized.
+
+### For lineup equipment such as switchgear and motor control centers, a label shall be applied to each section, each individually drawable breaker, and each MCC bucket — not only to the equipment as a whole.
+
+### Per-section labeling is the practical compromise for most installations and is the basis for the cost and label-count estimates in the study. {note}
+
+### Per-device labeling shall be specified at the start of the project where it is required by the Owner's safety program, because retrofitting per-device labels after a per-section study approximately doubles the label count.
+
+### The label location on each piece of equipment shall be repeatable and shall not be obscured by handles, hinges, latches, or routine maintenance hardware.
+
+### Where the equipment door swings outward, the label shall be on the door at the worker's eye level; where the worker approaches the equipment from the side, the label shall be on the side panel.
+
+### Label placement details shall be provided on representative equipment types — switchgear section, MCC column, panelboard cover, transformer enclosure. [[drawing: Label placement details on representative equipment types — switchgear section, MCC column, panelboard cover, transformer enclosure]]
+
+# Deliverables {toc}
+
+## The deliverable set for the arc-flash study comprises three artifacts that shall be consistent with each other in every value.
+
+## Calculation Report {toc}
+
+### The report shall include, at minimum:
+
+- Executive summary identifying the highest-incident-energy buses and the buses where incident energy exceeds 40 cal/cm²
+- System description with single-line diagram, bus identifiers, and the modeling boundary
+- Utility data source and date
+- Equipment data sources (field survey, manufacturer data, shop drawings)
+- Protective device settings table with the source of each setting (coordination study, field-verified, etc.)
+- Methodology statement identifying the IEEE 1584 edition, electrode configurations applied, working distances used, and any departures from the standard methodology
+- Bus-by-bus results table with bolted-fault current, arcing current (both max and min cases), arc duration, working distance, incident energy at the working distance, arc-flash boundary, label signal word, and required PPE
+- Mitigation recommendations for any bus where reasonable design changes could lower the incident energy meaningfully
+- Statement of assumptions and the conditions under which the study shall be reviewed or re-run
+- Engineer's seal and signature
+
+## Labels {toc}
+
+### The physical labels shall match the report values exactly.
+
+### A discrepancy between the report and a label is a finding against the study and shall be corrected before closeout.
+
+## Single-Line Diagram {toc}
+
+### The single-line diagram delivered with the study shall identify every modeled bus by the same identifier used on the labels and in the report.
+
+### The single-line diagram shall be maintained as a controlled document for the life of the facility and shall be updated whenever the study is updated.
+
+# Worker Training Coordination {toc}
+
+```datasheet
+label: Owner Training Coordination
+type: checkbox
+options:
+ - "Worker training on label interpretation"
+ - "Energized-work permitting procedure references study"
+ - "PPE inventory matched to study results"
+ - "Periodic-review schedule established"
+default: "Worker training on label interpretation"
+```
+
+## The arc-flash study is an input to the Owner's electrical safety program, not a substitute for it. {note}
+
+## NFPA 70E requires that workers who perform tasks on or near energized equipment be trained as qualified persons, that they be familiar with the labels installed on equipment they will interact with, and that they be retrained at intervals not exceeding three years.
+
+## The Contractor's responsibility under this standard ends at the delivery of the labels and the report.
+
+## The Owner is responsible for incorporating the study results into worker training, energized-work permitting, PPE selection, and the periodic-review schedule.
+
+## The study shall identify, in its mitigation recommendations, any task-specific PPE that requires specification of a particular arc-rating beyond commodity electrical PPE.
+
+## The Owner shall procure any task-specific PPE identified by the study before workers are permitted to perform the affected tasks.
+
+# Re-Study Triggers {toc}
+
+## NFPA 70E 130.5(G) requires that the arc-flash risk assessment be reviewed periodically at intervals not exceeding five years, and reviewed whenever changes occur that could affect the analysis. {note}
+
+```datasheet
+label: Conditions Triggering Re-Study Before the Five-Year Interval
+type: checkbox
+options:
+ - "Utility available fault current change (notified by utility)"
+ - "Service or main equipment replacement or upgrade"
+ - "Protective device settings change (any device in the model)"
+ - "Protective device replacement (new make or model)"
+ - "Addition of significant new load (motors, transformers, generation)"
+ - "Addition or removal of on-site generation"
+ - "Configuration change (tie operation, bypass routing)"
+ - "Discovery of a field condition inconsistent with the modeled assumptions"
+default: "Utility available fault current change (notified by utility)"
+```
+
+```datasheet
+label: Periodic Review Interval
+type: select
+options:
+ - "5 years (NFPA 70E maximum)"
+ - "3 years (conservative)"
+ - "Annual (high-change facilities)"
+default: "5 years (NFPA 70E maximum)"
+```
+
+## The Owner shall maintain a record of the study date on every label and shall track the next review date in the facility records.
+
+## A review at the five-year interval is not necessarily a full recalculation; the reviewer shall confirm that none of the re-study trigger conditions has changed since the prior study.
+
+## Where any re-study trigger condition has changed, the affected portion of the study shall be re-run and new labels produced for the affected buses.
+
+## As part of the five-year review, the Owner shall request updated available fault current data from the serving utility and compare it to the value used in the study.
+
+## Any material increase in utility available fault current requires re-running the study.
+
+## Utility fault current change is the trigger most commonly missed, because utilities increase available fault current as they reinforce their distribution system and the increase is not always communicated to the customer. {note}
+
+## The Owner's maintenance procedures shall include notification of the responsible engineer when a protective device in the arc-flash model is replaced.
+
+## A protective device replacement is the second commonly missed trigger, because a breaker replaced with one of different manufacture or trip-unit family may have substantially different clearing characteristics. {note}
+
+## A 5-year interval is the NFPA 70E maximum and is appropriate for stable facilities with documented change-management procedures, while a shorter interval is appropriate where the facility undergoes frequent reconfiguration or change-management procedures do not reliably capture electrical-system modifications. {note}
+
+# Mitigation Hierarchy {toc}
+
+## The study report shall identify mitigation options for buses with incident energy that would require Category 3 (25 cal/cm²) or higher PPE, or that exceed 40 cal/cm².
+## Mitigation shall be evaluated in the following order, which corresponds to the hierarchy of controls in NFPA 70E and reflects effectiveness from most to least:
+
+1. Eliminate the need to work on the equipment energized (de-energize, lock out, verify)
+2. Substitute the equipment for a design with lower arcing characteristics (arc-resistant switchgear, current-limiting fuses upstream)
+3. Engineer the protective system for faster clearing (faster instantaneous, ZSI, ERMS, differential)
+4. Administrative controls (restrict tasks, increase working distance, require remote operation)
+5. PPE (last line of defense)
+
+```datasheet
+label: Mitigation Recommendations Provided In Report
+type: radio
+options:
+ - "For every bus exceeding 8 cal/cm²"
+ - "For every bus exceeding 25 cal/cm²"
+ - "For every bus exceeding 40 cal/cm² only"
+default: "For every bus exceeding 25 cal/cm²"
+```
+
+## The report shall present mitigation as engineering recommendations, not as design changes.
+
+## The Owner and Engineer of Record shall decide which recommendations to implement; the analyst's role is to identify the options and the order-of-magnitude reduction each would achieve.
+
+## Where a mitigation recommendation is adopted, the affected portion of the study shall be re-run with the changed conditions and new labels produced.
+
+# Field Verification {toc}
+
+## Before the labels are released for installation, the Contractor shall verify that the field conditions match the study assumptions.
+## The verification shall include, at minimum:
+
+- Protective device settings read at each device in the model and compared to the report's setting table
+- Available fault current at the service compared to the utility data used in the study
+- Equipment identifiers on the equipment match the identifiers used in the report
+- Any ERMS or similar maintenance-mode switches are functional and wired as the report assumes
+- Any ZSI interlock signals are continuous through every device in the scheme
+
+```datasheet
+label: Pre-Installation Verification
+type: checkbox
+options:
+ - "Protective device settings verified at every device"
+ - "Utility fault current re-confirmed at study delivery"
+ - "Equipment identifier reconciliation"
+ - "ERMS functional verification"
+ - "ZSI continuity verification"
+default: "Protective device settings verified at every device"
+```
+
+## Any discrepancy found during verification shall be resolved before labels are installed.
+
+## Installing a label that does not match the as-installed condition is worse than no label at all, because it creates a false sense of protection. {note}
+
+# Delivery, Storage, and Handling {toc}
+
+## The calculation report, the native software project file, and the photographic record of installed labels shall be delivered to the Owner in both printed and electronic form.
+
+## The electronic form shall be on durable media or in a managed document repository that the Owner controls.
+
+## Reliance on a contractor's cloud storage account for the only copy of the study is not acceptable; the Owner shall be able to retrieve and edit the study without contacting the original analyst.
+
+## Spare labels — at least one duplicate of each installed label — shall be delivered to the Owner for replacement of labels damaged in service.
+
+## Spare labels shall be stored in the main electrical room or in another location identified in the closeout documentation.
+
+# Warranty {toc}
+
+```datasheet
+label: Analyst Warranty Period
+type: select
+options:
+ - "1 year from report issue"
+ - "Through the project warranty period"
+ - "Through the first periodic review"
+default: "1 year from report issue"
+```
+
+## The analyst shall warrant the analysis for accuracy at the time of issue, against the input data provided and the standards in force.
+
+## The analyst is not responsible for changes in field conditions, utility fault current, or protective device settings that occur after the study is issued; those are the Owner's responsibility under the periodic-review program.
+
+## The Contractor shall warrant the physical installation of the labels — adhesion, location, and correspondence between label content and the report — for the project warranty period.
+
+## Labels that detach, fade, or are found to disagree with the report during the warranty period shall be replaced at no cost to the Owner.