so let me run this by you in a different scenario so I understand it.
Its 47 amps, but lets say its a continuous load. so 47x1.25 is 58.75amps
this would take the conductor upto a #6 in the 90C column.
As we are working with the terminations at 75C I would double check the 75C column and as a #6 is ok upto 65A in the 75C I would still be ok to work with a #6 for the 58.75A continuous load right>?
I'm new so just wanted to make sure that its ok to post questions liek this that I struggle with. Is there any kind of extra curriculum you can recommend for me to?
Essentially correct... but let's try to give you an even better understanding.
First, let's clarify that the 47A in your example is the calculated load. In many instances, the calculated load in amperes differs from actual or nameplate value. Code compliance is always based on calculated load [Article 220]. Calculated load does not include 125% factoring for continuous loads when determining conductor and overcurrent protection ratings [e.g. 210.19(A)(1), 215.2(A)(1)].
The reason I bring this up is highlighted red in the quote of your post above. Being a continuous load it will be factored by 125% in the conductor and overcurrent protection rating determination... but that does not change the the value of the calculated load (47A in your example). And the reason I am emphasizing this is because, as you've already realized, conductor sizing is two part... but the 125% factoring for continuous load applies only to the minimum size determination for termination temperature limitation, i.e. the 75?C comparison to table values in your example.
125% factoring does not apply to the conductor ampacity determination. Conductor ampacity is only required to equal or exceed the calculated load value (47A)... after applying adjustment and correction to the table value for the conductor insulation type and conditions of use imposed under 310.15(B), i.e. corrected for ambient temperature, adjusted for number of conductors within the raceway or cable, etc...
Then there's a third part that enters circuit compliance determination: The conductor must be protected by the overcurrent device at its adjusted and corrected ampacity. We can get into that if need be once you grasp the preceding.
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As to recommendations for extra curriculum, there's plenty of documentation available, be it books or on the internet, some better than others... but IMO the best is to just continue to participate in forum discussions (here?
), because you'll get feedback and experience differing points of view.
