Cable derating equation
Independent correction factors multiply the reference ampacity.
Iz,corrected = Iz,reference × Ca × Cg × Ci × Cswhere:
- Iz
- Cable current-carrying capacity[A]
- Ca
- Ambient-temperature factor
- Cg
- Grouping factor
- Ci
- Installation factor
- Cs
- Soil thermal factor
Replace screening factors with values from the adopted installation table.
How to use the Cable Derating Factor Calculator
Combine ambient-temperature, grouping, installation, and soil factors to estimate corrected cable ampacity. Start by choosing the operating mode, then enter values from nameplates, measurements, or project documents in the units shown. The result updates immediately and keeps intermediate quantities visible for review.
- Confirm the system and calculation mode.
- Enter measured or manufacturer-rated values.
- Review the primary result and intermediate metrics.
- Continue with the related protection or equipment-selection checks.
Calculation method and validation
The equations and symbol definitions above show the complete calculation basis. Inputs are checked before calculation so zero, negative, incompatible, or physically impossible combinations are flagged instead of silently producing a misleading result.
How to interpret the result
Use the main result as a starting value and read every supporting metric. Factors are typical screening values, not a reproduction of a complete IEC 60364-5-52 national table All grouped circuits are substantially loaded A passing or recommended result means the entered mathematical conditions are satisfied; it does not certify the complete installation or a particular product combination.
- Factors are typical screening values, not a reproduction of a complete IEC 60364-5-52 national table
- All grouped circuits are substantially loaded
Selection limits and next checks
Preliminary engineering estimate only. Verify the final design against the current applicable standard, local rules, manufacturer data, and project conditions. Compare the output with the current applicable standard, local rules, exact VIOX product datasheet, environmental conditions, protection coordination, and the engineer's project requirements before procurement or installation.
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Assumptions
- Factors are typical screening values, not a reproduction of a complete IEC 60364-5-52 national table
- All grouped circuits are substantially loaded
Important Warnings
- Preliminary engineering estimate only. Verify the final design against the current applicable standard, local rules, manufacturer data, and project conditions.