exam study guide question ampacities derating

[will1955]

I have just started the Mike Holt volume one Art 90-480 study guide. On page 16 figure 100-4 they are referring to derating the ampacities of a wire. I found the table for the 115 allowable amps. I found the table for the derating for the number of conductors in the raceway (.87). I cannot figure out what the other derating number is for(.80).

 

[charlie b]

Most of us do not have a copy of that book. Can you give us more information?

 

[infinity]

I don't have that book but is it possible that the .87 is for ambient temperature adjustment from Table 310.15(B)(2)(a) Ambient Temperature Correction Factors Based on 30°C (86°F)?

Welcome to the Forum.

 

[Smart $]

...is it possible that the .87 is for ambient temperature [correction] ...

That'd be my guess... and the .80 (4-6@80%) is for the number-of-conductors adjustment.