I'm sorry this doesn't have anything to do with this post. I don't know how to post a new topic,so if you can help me out. My question is. I'm studying for my journeyman's Electrician course. Mike Holt exam prep. Page 187 conductor ampacity example 1 . On the ambient temperature correction factor it says for 150 degrees it's .58 but when I look it up it says .50 Thanks
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Make sure you are using the correct table for the factory test ambient temperature rating of the conductor, which is usually 30C [86F]. Most applications in my familiar work, use Table 310.15(B)(2)(A). Avoid using the next table that is much larger and stands out visually, as it is for more exotic types of wire that are factory tested at 40C ambient. Draw an X through it, if it doesn't apply to your scope of work.
You can also use the square root formula, if desired. 310.15(B)(2). sqrt((Tc - Ta)/(Tc - T0)). It may get you slightly different results, because it is evaluated with more precision than the 5C temperature ranges in the tables.
Tc is the temp rating of the conductor, such as 90C [194 F]
Ta is the effective ambient temperature
T0 is the factory test ambient temperature, usually 30C [86 F]
