Steamdonkey2011
Member
- Location
- Boise, Id
I?ve done a fair amount of searching in this forum and other resources and have not been able to understand why the NEC appears to ignore the temp rating of terminations when applying ampacity adjustment factors to conductors. Under conditions where ampacity adjustments aren?t required, the current flowing though a 90 degree conductor connected to 75 degree termination must not exceed the value shown in the 75 degree column in the conductor ampacity table. In this situation it appears the operating temperature of the conductor is limited to the rating of the termination, which makes perfect sense.
In the case where adjustment factors apply, it?s possible to have conductors operating at temps over 75 degrees if the starting point for the ampacity calculation is the 90 degree ampacity rating of the conductor. This would seem to overheat the 75 degree termination. Stated alternatively, if 200 Amps is flowing through each of six #4/0 copper conductors sharing a conduit, the insulation temp rating would need to be 90 degrees. If this operating condition would overheat 75 degree insulation then why wouldn?t it overheat 75 degree terminations?
Is there a flaw in my logic or am I just overthinking the issue?
In the case where adjustment factors apply, it?s possible to have conductors operating at temps over 75 degrees if the starting point for the ampacity calculation is the 90 degree ampacity rating of the conductor. This would seem to overheat the 75 degree termination. Stated alternatively, if 200 Amps is flowing through each of six #4/0 copper conductors sharing a conduit, the insulation temp rating would need to be 90 degrees. If this operating condition would overheat 75 degree insulation then why wouldn?t it overheat 75 degree terminations?
Is there a flaw in my logic or am I just overthinking the issue?