I was looking to clarify some conflicting information I’ve read or heard about conductor ampacities.
I use the NEC ampacities chart as a guideline for matching breakers with wire gauges and determining the maximum amperes for which a wire is rated. They have it all laid out for many different gauges of wire, but some are not in the chart.
The InterNACHI course on this subject refers to the NEC chart, but they also show another chart (2nd page of attached file) which seems to conflict with this chart, which is one source of my confusion. If I understand correctly, is the first chart only for SE wires and the second chart for branch wiring and feeders to sub panels?
Ultimately, I am trying to fill in the maximum breaker size for the wires below:
#6 CU I see a lot and usually paired with a 60 amp breaker. I’ve seen it a couple of times with 70amp breaker and have been told this is fine, but according to InterNACHI chart it is not so i called it out in an abundance of caution. The other sizes are less common and the few times I’ve seen them it was clear the breaker was either OK or undersized, but I’d like to know for certain once and for all.
Thanks in advance.
Wiring Ampacities.pdf (31.0 KB)