Every conductor has resistance, and current flowing through resistance produces heat. Push too much current and the conductor gets too hot, which damages insulation and shortens its life. The continuous current a conductor can carry while staying within safe temperature limits is its ampacity.
Ampacity is not a single number stamped on the wire. It depends on the conductor material and size, the insulation rating, and most of all on how well the conductor sheds heat to its surroundings.
That last factor surprises people. The same cable carries less current safely when it is buried in conduit than when it hangs in open air, because soil and conduit trap heat while open air carries it away. Ambient temperature matters too: a hot day lowers ampacity.
Current through resistance makes heat, and ampacity is the current a conductor carries while staying within its safe temperature. The same cable sheds heat well in open air but traps it in conduit and soil -- so it carries less current safely underground.
When you size a circuit, you are matching the expected current to a conductor whose ampacity, in its real installed conditions, comfortably exceeds it.
How a utility builds and protects its distribution grid sets the baseline for every equipment order that follows. The Feeder tracks the infrastructure investment and modernization programs reshaping that baseline, free, every week.
Question 1 of 2
What ultimately limits how much current a conductor can carry continuously?
Educational material only. This is not engineering, safety, or procurement
advice. Confirm any value against manufacturer documentation and a licensed
professional before specifying equipment.