Termination Temperature Ampacity Limit (NEC 110.14(C))
Usable ampacity is the lesser of the termination column and the derated 90 C value.
Example
You enter
- 90 C ampacity (Table 310.16) 260
- 75 C ampacity 230
- 60 C ampacity 195
- Lowest termination rating 75
- Circuit over 100 A? true
- Combined ambient/fill derate (1.0 = none) 0.8
You get
- Termination-column ampacity 230
- Derated 90 C value 208 A
- Governing ampacity 208
Details, formula, and sources
The NEC 110.14(C) termination rule: the usable ampacity is the LESSER of the lowest-rated termination column (60 or 75 C) and the derated 90 C value. The 90 C column is for the ambient/fill derating math only -- it never reaches the terminals. Circuits <= 100 A default to 60 C unless listed 75 C; over 100 A use 75 C.
termination_ampacity = over_100a ? amp_75c : (termination_rating == 75 ? amp_75c : amp_60c); derated_90c = amp_90c x derate_factor; governing = min(termination_ampacity, derated_90c).
NEC 2023 (NFPA 70). 110.14(C) (temperature limitations of terminations) with Table 310.16.
Free read-only access at nfpa.org/freeaccess.
Estimate. AHJ and licensed electrician govern. Verify against the NEC edition adopted in your jurisdiction.
Field names used by the API: amp_90c, amp_75c, amp_60c, termination_rating, over_100a, derate_factor, termination_ampacity_a, derated_90c_a, governing_a
- 90 C for derating only the 90 C column may be used only for the ambient and fill derating math, not for the final termination currentNEC 2023 110.14(C)
- Termination column by size at or below 100 A use 60 C unless all terminations and conductors are listed 75 C; above 100 A use 75 CNEC 2023 110.14(C)(1)