iwire,
The code never says "just breakers", it talks about ALL overcurrent protective devices. Actually, all fuses and breakers are tested by UL at their 100% rating. The "3hour derating" comes in when the protective devices are mounted into enclosure.
My question: are protective devices designed to protect wires sized for continuous and non-continuous loads OR are wires sized because of the performance of protective devices? (i.e. which is the chicken and which is the egg)
