Approach Boundary Worksheet Calculator

The Approach Boundary Worksheet Calculator compares a project-record distance with a documented reference distance. Its primary result is the signed distance difference after both values are converted to inches.

This record-comparison calculation supports electrical safety documentation, design-package review, and work-planning records where an approach distance has already been established by a separate source. It can identify whether two entries are directly comparable, whether the source record was documented, and whether the project record differs from the reference.

The calculator does not calculate a required approach boundary, establish an energized-work limit, authorize entry into an electrical hazard area, or determine whether a person is qualified to perform work.

Recorded Distance Inputs

The worksheet uses the following record fields:

Field	Purpose
Boundary record type	Identifies the type of distance record being compared. The example uses Approach record.
Method and version	Records the source method associated with the distances, such as worksheet-v1.
Voltage basis	Records the voltage basis used in the source record, such as Line to line.
Nominal voltage (V)	Records the nominal system voltage associated with the boundary documentation.
Reference distance (entered unit)	The distance from the source method or reference record.
Reference unit	The unit assigned to the reference distance.
Entered distance (entered unit)	The project, field, drawing, or work-package distance being compared.
Entered unit	The unit assigned to the entered distance.
Qualified-person record	Records whether source documentation includes this field.
Source reference	Identifies the source record, calculation package, drawing note, or other documented reference.

The voltage and qualified-person entries are documentation fields, not calculation variables in the displayed distance comparison. They preserve the context of the source record so that a reviewer can determine whether the two distance entries belong to the same electrical condition and documentation basis.

A nominal voltage record should not be treated as proof that the source distance applies to every enclosure, conductor arrangement, work task, or energized condition in a project. Electrical distribution equipment can have similar nominal voltages while presenting different access, exposure, equipment-condition, and work-scope conditions.

Distance Difference Formula

The calculator converts the two recorded distances to inches and subtracts the reference distance from the entered distance:

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

For records already entered in inches:

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

A positive result means the entered distance is greater than the reference distance. A negative result means the entered distance is less than the reference distance. A result of zero means the two recorded distances match after unit conversion.

The calculator reports:

• Reference distance in the selected record unit
• Entered distance in the selected record unit
• Distance difference in inches
• Source note, such as Source recorded
• Record comparison, such as Entered values comparable

The result is a comparison of documented values. It is not an approach-boundary determination.

Calculation Example

For the example record:

Input	Entered Value
Boundary record type	Approach record
Method and version	worksheet-v1
Voltage basis	Line to line
Nominal voltage (V)	480
Reference distance	42 in
Entered distance	48 in
Qualified-person record	Recorded
Source reference	record-a

The calculation is:

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

Result: 6 in

The Entered distance is 6 inches greater than the Reference distance. With both distances entered in inches and associated with the same documented method and version, the worksheet can report the record comparison as Entered values comparable.

A record reviewer can use that difference to locate mismatched plan notes, work instructions, clearance entries, or source-document revisions. The worksheet does not indicate that 48 inches is permitted, required, safer, or code-compliant.

Source Completeness and Comparability

The calculator’s Source note and Record comparison help separate arithmetic agreement from record quality.

Source recorded indicates that a source reference was entered. It does not validate the source method, confirm that the reference remains current, or verify that it applies to the exact equipment and work condition.

Entered values comparable indicates that the records can be compared using the worksheet’s documented inputs and unit conversion. It does not establish that the underlying electrical conditions are equivalent. The reviewer must verify that the records use the same method and version, voltage basis, equipment context, and intended application.

For example, two approach records may both identify 480 V line-to-line systems, yet one may refer to a different equipment lineup, task scope, source condition, access arrangement, or documentation basis. A matching voltage entry alone does not make the records interchangeable.

Electrical Work Planning Limits

Approach-boundary documentation is separate from routine electrical design calculations such as conductor ampacity, AWG or kcmil selection, terminal temperature limitations, correction factors, adjustment factors for current-carrying conductors, raceway fill, voltage-drop review, motor feeder calculations, and branch-circuit load calculations.

Those calculations answer different questions:

• Ampacity calculations evaluate conductor loading and applicable temperature or adjustment conditions.
• Raceway-fill calculations evaluate conductor space within a raceway.
• Voltage-drop calculations evaluate conductor performance over a circuit length.
• Approach-boundary records document a distance associated with a separate safety method or source record.

Do not use the calculated distance difference to modify conductor sizing, feeder routing, branch-circuit design, raceway layout, bending space, working space, or equipment clearances unless the governing design or safety documentation specifically directs that use.

The applicable electrical safety procedure, project requirements, equipment documentation, employer program, and AHJ or other governing authority must be checked separately when an actual approach boundary, energized-work restriction, access limit, qualification determination, or compliance decision is required.

Where the governing record is a broader electrical safe-work distance calculation, review the Electrical Safe Work Distance Calculator separately rather than combining its assumptions with this comparison worksheet.