Arc Flash Boundary Calculator

An arc-flash boundary worksheet may be associated with an incident-energy study, but the worksheet performs a narrower record comparison. It compares a reviewed Reference distance with an Entered distance and reports the signed and absolute differences.

The primary output is the Distance difference, expressed in inches. A positive result means the entered distance is greater than the reviewed reference distance. A negative result means the entered distance is closer than the reviewed reference distance. The Absolute distance difference removes the direction and reports only the magnitude of the separation.

This distance-comparison record can support review of labels, work planning notes, equipment records, job briefings, or an arc-flash study file. It does not calculate incident energy, determine an arc-flash boundary, establish PPE requirements, or approve an energized-work distance.

Distance Comparison Inputs

The worksheet uses three fields:

Field	Electrical record purpose
Reference distance	The distance from the reviewed source record used as the comparison baseline
Entered distance	The distance being checked against the reviewed reference value
Source reference	The record identifier documenting where the distance values came from

Both distance fields are entered in inches. The source record should identify the reviewed arc-flash documentation clearly enough for the electrical team, safety reviewer, facility representative, or AHJ-facing project file to trace the value back to its source.

For example, a source reference such as arc-flash-record-a can identify the reviewed study record, equipment file, or controlled project document that supplied the comparison distance.

Calculation Basis

The worksheet uses direct subtraction:

\(\displaystyle \Delta d = d_{\mathrm{entered}} - d_{\mathrm{reference}}\)

It also reports the unsigned distance:

\(lvertDelta drvert = \left|d_{\mathrm{entered}} – d_{\mathrm{reference}}\right|\)

The signed output preserves direction. The absolute output provides a simple tolerance or variance figure for documentation.

Result	Meaning
Distance difference = 0 in	The entered and reference distances match
Distance difference > 0 in	The entered distance is farther from the source than the reference distance
Distance difference < 0 in	The entered distance is closer to the source than the reference distance
Absolute distance difference	The total difference without regard to whether the entered value is closer or farther

Calculation Example

A reviewed source record lists a Reference distance of 18 in. A field record, work-planning sheet, or separate equipment entry lists an Entered distance of 24 in.

Input	Value
Reference distance	18 in
Entered distance	24 in
Source reference	arc-flash-record-a

\(\displaystyle \Delta d = 24 \mathrm{in} - 18 \mathrm{in} = 6 \mathrm{in}\)

[lvertDelta drvert = |6 mathrm{in}| = 6 mathrm{in}]

The worksheet result is:

Result	Value
Reference distance	18 in
Entered distance	24 in
Distance difference	6 in
Absolute distance difference	6 in
Record comparison	Source recorded

The entered value is 6 in farther than the reviewed reference distance. The result documents a comparison only; it does not establish whether 18 in or 24 in is the applicable working distance, arc-flash boundary, restricted approach boundary, or shock-protection distance.

Arc-Flash Study Limits

A complete arc-flash hazard assessment requires electrical-system and equipment information beyond two distance values. Depending on the study method and project scope, that work can involve available fault current, protective-device characteristics, clearing time, equipment configuration, conductor and enclosure parameters, working distance, incident energy, labeling assumptions, and the specific task being performed.

No such inputs are present in this worksheet. Therefore, the Boundary result remains: entered-value worksheet only; no incident-energy, boundary, equipment, task, or project determination is made.

Do not use the distance difference as a substitute for an engineered arc-flash study, equipment label, energized electrical work permit, PPE category determination, approach-boundary determination, or site-specific safety procedure. Verify the governing record, equipment identification, and applicable safety requirements with the responsible electrical authority, qualified person, and AHJ where applicable.

For a record-to-record comparison with method and source compatibility checks, review the Arc Flash Study Scenario Comparison Calculator.