Termination Temperature Ampacity Limit (NEC 110.14(C))

Usable ampacity is the lesser of the termination column and the derated 90 C value.

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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

Checked against published worked examples from: NEC 2023 110.14(C) with Table 310.16.

Details, formula, and sources

ScopeThe 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 default to 75 C, but a declared 60 C termination still governs.

Formula or tabletermination_ampacity = (termination_rating == 75 ? amp_75c : amp_60c); nec_default_column = over_100a ? 75 : 60 (reported, flags a 60 C termination above 100 A); derated_90c = amp_90c x derate_factor; governing = min(termination_ampacity, derated_90c).

Source and editionNEC 2023 (NFPA 70). 110.14(C) (temperature limitations of terminations) with Table 310.16.

Free accessFree read-only access at nfpa.org/freeaccess.

What governsEstimate. AHJ and licensed electrician govern. Verify against the NEC edition adopted in your jurisdiction.

API field namesamp_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)