/ Field knowledge · NEC 110.14
A correctly sized conductor can still fail at the lug.
Termination devices must be identified for the conductor material. Copper and aluminum are not automatically interchangeable. One lug does not automatically mean two conductors. 90°C insulation does not automatically allow the 90°C ampacity column — the lowest applicable terminal rating controls. Torque to the manufacturer’s indicated value. Sparky Edition #022. This page does not invent 110.26 working-space dimensions.
Packet: 110.14 PDF · ES. Source: Sparky #022. Conductors: 110.4–110.8. SCCR: 110.9–110.10. Environment: 110.11–110.13.
- 110.14(A): terminals identified for more than one conductor if you land two.
- 110.14(B): splices identified for the material and application, insulated.
- 110.14(C): many terminations are 60°C or 75°C even when the wire is 90°C.
- 110.14(D): too loose overheats; too tight damages the terminal or conductor.
Tool: Terminal, temperature, or torque?
90°C THHN on a 75°C breaker, two conductors in a lug not identified for it, no torque recorded
Feeder sized. Termination wrong.
What to send
Equipment terminal rating, conductor material and size, and whether more than one conductor lands on the lug.
If 90°C insulation is being treated as 90°C ampacity
Send the terminal rating, the conductor, and whether more than one lands on the lug. Masterbuild will say whether 110.14 still has no torque path — not whether the AHJ will accept a substitution.
Send Project Background+1 (786) 398-6940 · osmany.portal@masterbuildconsulting.com
Masterbuild provides engineering services under a written scope. Not a feeder calculation and not a 110.26 working-space determination. Confirm adopted 110.14. This is not legal advice.