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Ampacity Calculator

This calculator checks conductor ampacity using entered ampacity values and adjustment factors. Verify base ampacity, correction factors, adjustment factors, terminal temperature limits, and installation conditions against the adopted code and project requirements.

Job Information

Project nameLocationPrepared byDateNotes

Main Inputs

Ampacity calculation modeTable-based ampacity lookup requires verified conductor ampacity data. Use Manual ampacity check for now.Design load current (A)Use the load current the conductors must carry. Do not use breaker size unless the breaker size is the actual design basis.Base ampacity per conductor before adjustments (A)Enter the conductor ampacity before ambient correction, conductor-count adjustment, or other project factors.Equipment / terminal ampacity limit per conductor (A)Enter the maximum ampacity allowed by the applicable equipment termination temperature rating.Parallel conductors per phase or polarityEnter 1 for a single conductor set. Enter the number of parallel conductors per phase or polarity when parallel conductors are used.

Advanced Inputs

Use these when the job has project-specific assumptions, manufacturer data, or review conditions.

Conductor sizeOptional documentation field. Manual ampacity value is still used for the calculation.Conductor materialOptional documentation field unless verified lookup logic is implemented.Insulation typeOptional documentation field unless verified lookup logic is implemented.Terminal temperature ratingOptional documentation field. Verify the actual equipment termination rating.Ambient temperature input modeAutomatic factor lookup requires verified table data. Manual factor entry is currently used.Ambient correction factorUse 1.0 if no ambient temperature correction is required.Current-carrying conductor input modeAutomatic factor lookup requires verified table data. Manual factor entry is currently used.Current-carrying conductor adjustment factorUse 1.0 unless conductor-count adjustment or bundling derating applies.Other project / installation adjustment factorUse for documented project, equipment, or installation multipliers not captured above.

Result

Pass

Status

Pass - Verify Inputs

Design load current is below the calculated allowable ampacity, but base ampacity and adjustment factors must be verified.

Adjusted ampacity before terminal limit

100.0 A

Equipment / terminal limit

100.0 A

Allowable ampacity per conductor

100.0 A

Total allowable ampacity

100.0 A

Load utilization

80.0%

Remaining capacity

20.0 A

Governing limit

Equal

Practical Next Steps

Use the result as a design check, then verify the assumptions shown in the warnings and references.
Save or export the result with the project record if the inputs match the current design.
Recalculate when field routing, equipment selections, loads, or owner criteria change.

Confirm current-carrying conductor count, ambient conditions, terminal ratings, insulation ratings, and installation conditions.

Base ampacity was entered manually. Verify the value against the applicable conductor ampacity table, manufacturer data, and project requirements.

Adjustment factors were entered manually. Verify ambient correction, current-carrying conductor adjustment, and other project factors.

Manual ampacity value is being used. Verify that the entered ampacity matches the selected conductor size, material, insulation, and terminal rating.

Save and Export

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Calculation Breakdown

Input Summary

Design load current: 80.0 A
Base ampacity per conductor: 100.0 A
Parallel conductors per phase/polarity: 1
Equipment / terminal ampacity limit: 100.0 A

Adjustment Factors

Ambient correction factor: 1.00
Current-carrying conductor adjustment factor: 1.00
Other project / installation factor: 1.00

Ampacity Calculation

Adjusted ampacity: 100 x 1 x 1 x 1 = 100.0 A
Allowable ampacity per conductor: lesser of adjusted ampacity and terminal limit = 100.0 A
Total allowable ampacity: 100.0 A x 1 = 100.0 A

Load Check

Design load current: 80.0 A
Load utilization: 80.0%
Remaining capacity: 20.0 A
Result: Pass - Verify Inputs

Code and Design References

NEC Article 310 and applicable ampacity tables

Base ampacity, temperature correction, conductor-count adjustment, terminal limitations, and installation conditions must be selected from the adopted code and manufacturer data.

This calculator uses user-entered ampacity values and factors until verified table lookup data is implemented.