110.4 Voltages
Electrical equipment must have a voltage rating not less than the nominal voltage of the circuit it is connected to. A 240 V-rated component cannot simply be assumed suitable on a higher-voltage system.
110.5 Conductors
Current-carrying conductors are generally copper, aluminum, or copper-clad aluminum. Unless otherwise permitted, conductor sizing requirements are based on copper. A #4 copper conductor and a #4 aluminum conductor do not automatically have the same allowable ampacity.
110.6–110.8
Conductor sizes are expressed in AWG or circular mils. As AWG numbers get smaller, conductor size gets larger. Completed wiring must be free from short circuits, ground faults, and improper connections to ground. Only wiring methods recognized as suitable by the NEC may be used.
Field tip
When reviewing an existing feeder, do not document only “3-#4 conductors.” Also verify copper or aluminum, insulation type, voltage, wiring method, condition, and termination compatibility. Next: 110.9–110.10.
Code basis
NEC 2026 Article 110 education from the owner-provided Daily Code Talk. Confirm adopted edition. Not a feeder design.