Limited Approach Boundary Calculator

A Limited Approach Boundary Calculator compares an entered project distance with a recorded reference distance and returns the distance difference. Its electrical purpose is document control and distance verification: it shows whether two recorded boundary distances can be compared on the same unit basis and how far the entered value is above or below the reference value.

The result supports approach-boundary worksheet review, electrical work planning, and source-record reconciliation. It does not establish a required Limited Approach Boundary, determine shock protection requirements, or authorize entry into an approach boundary.

For the displayed calculation, the calculator returns:

• Reference distance: 42 in
• Entered distance: 48 in
• Distance difference: 6 in
• Record comparison: Entered values comparable

A positive difference means the Entered distance is greater than the Reference distance. A negative difference means the Entered distance is less than the Reference distance.

Recorded Boundary Inputs

The calculator uses the following field names to preserve the project record and distinguish arithmetic from the underlying electrical safety determination.

Field	Function in the comparison
Method and version	Records the worksheet method used for the comparison, such as worksheet-v1
Voltage basis	Records the stated voltage basis, such as Line to line
Nominal voltage (V)	Records the nominal system voltage associated with the source documentation
Recorded reference distance (entered unit)	Supplies the source-reference distance to be converted for comparison
Reference unit	Identifies the unit used for the Recorded reference distance, such as ft
Entered distance (entered unit)	Supplies the project-record distance being checked
Entered unit	Identifies the unit used for the Entered distance, such as in
Qualified-person record	Records whether the source documentation includes the required field
Source reference	Identifies the source record used for the comparison

The Voltage basis and Nominal voltage (V) provide electrical context, but the displayed comparison does not derive a boundary from voltage. It converts the two recorded distances to inches and calculates their difference.

A value in the source record may be associated with energized equipment, a branch circuit, feeder, service equipment, switchgear, motor controller, panelboard, or other electrical distribution equipment. The calculator does not identify equipment construction, exposed energized parts, available fault current, arc-flash condition, or any equipment-specific access restriction.

Distance Conversion Formula

The comparison uses inches as the common unit.

\(\displaystyle \text{reference distance in} = \text{Recorded reference distance converted to inches}\)

\(\displaystyle \text{entered distance in} = \text{Entered distance converted to inches}\)

\(\displaystyle \text{distance difference} = \text{entered distance in} - \text{reference distance in}\)

\(\displaystyle \text{mode status} = \text{entered values comparable when the source record is complete}\)

For feet-to-inches conversion:

\(\displaystyle \text{distance in} = \text{distance ft} \times 12\)

The calculator’s Mode boundary type is limited. Its Calculation basis is a comparison of recorded distances, not a calculation of a required electrical approach boundary.

Calculation Example

The recorded values are:

Input	Value
Method and version	worksheet-v1
Voltage basis	Line to line
Nominal voltage (V)	480
Recorded reference distance (entered unit)	3.5
Reference unit	ft
Entered distance (entered unit)	48
Entered unit	in
Qualified-person record	Recorded
Source reference	record-b

First, convert the Recorded reference distance:

\(\displaystyle 3.5\text{ ft} \times 12 = 42\text{ in}\)

Then compare the Entered distance with the converted reference:

\(\displaystyle 48\text{ in} - 42\text{ in} = 6\text{ in}\)

The calculator result is therefore Distance difference: 6 in.

The Entered distance is 6 inches greater than the Reference distance. Because the source fields are recorded and the distances have been converted to a common unit, the result identifies the Record comparison as “Entered values comparable” and the Source note as “Source recorded.”

Electrical Use and Limits

This Limited Approach Boundary Calculator is appropriate when a project record needs to compare a stated distance against a documented reference distance. Typical uses include checking worksheet entries, reconciling a field measurement to a source record, reviewing a work-planning package, or identifying a mismatch before an electrical safety decision is finalized.

The output must not be treated as a field-established boundary. A 6-inch difference does not indicate compliance, noncompliance, safe approach distance, permissible entry, qualified-person status, or an energized-work authorization. The calculator does not determine the applicable approach boundary from the Nominal voltage (V), even though voltage is recorded in the worksheet.

The actual electrical safety decision must be verified from the governing source documentation, equipment condition, work scope, employer electrical safety program, and applicable requirements enforced by the AHJ or responsible authority. Confirm the voltage basis, nominal voltage, equipment identification, source reference, and whether the documentation is complete before relying on the recorded distance for job planning.

Where the comparison is used with conductor work, termination work, raceway installation, motor control equipment, feeder modifications, or voltage-drop review, keep those calculations separate. Ampacity, AWG or kcmil conductor selection, terminal rating, insulation temperature rating, current-carrying conductor adjustment factors, correction factors, raceway fill, and voltage-drop calculations require their own verified installation inputs and are not produced by this boundary comparison.