210.19 (A)(1) and 215.2 (A)(1)

[erodriguez]

Can someone please explain (in detail) the "before the application of any adjustment or correction factors" when determining the allowable ampacity of branch circuit and feeder conductors. Thank you.

 

[bdarnell]

You may or may not have to derate the conductor's ampacity based on the number of current carrying conductors in a raceway and also based on the ambient temperature at which the conductors will be operating.

These are the adjustment and correction factors.

 

[erodriguez]

Let me re-phase that...let's take a scenario with a branch circuit conductor that has continuous and non-continuous loads in a conduit with six additional current carrying conductors in an ambient tempature of 100-degrees F. In this case "adjustment or correction factors" are required. Do you apply these adjustments or correction factors before or after you calculate 125% of the continuous and 100% of the non-continuous?

 

[bdarnell]

After. You calculate the conductor size, then apply the correction factors.

And, yes, you do have to "double derate". Number of conductors and ambient. In either order - makes no difference.

 

[charlie b]

You are discussing two different things. You do one, then you do the other, as Brad said.

First, you determine the load. That's when the 125% and 100% come into play. That tells you what ampacity the conductors are going to have to have.

Then you pick a conductor, and see if it has the necessary ampacity. In determining the conductor's ampacity, you have to apply the derating factors.