Ambient Temp adjustment

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Cjx3

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Tacoma
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Electrician
Ok guys. Struggling with this question in the exam prep book.
5 thwn-2 10awg
Roof top under 7/8”
Ambient temp of 94*
310.15 B 2 days 60* adjustment
And 310.15 C 1 says 80% with 4-6 conductors.
The book says 60* adjustment is 58% per 310.15 B 1

but i can’t see how they come up with that 58%.
Can anyone help walk me through it?
94* looks like it’s a .96 adjustment. And 60* looks like 1.08

help!? Thx
 
Cjx3 said:
Ok guys. Struggling with this question in the exam prep book.
5 thwn-2 10awg
Roof top under 7/8”
Ambient temp of 94*
310.15 B 2 days 60* adjustment
And 310.15 C 1 says 80% with 4-6 conductors.
The book says 60* adjustment is 58% per 310.15 B 1

but i can’t see how they come up with that 58%.
Can anyone help walk me through it?
94* looks like it’s a .96 adjustment. And 60* looks like 1.08

help!? Thx
Click to expand...
94 degrees + 60 degrees = 154 degrees.
The temperature correction factor for 154 deg F is 0.58 for THWN-2
 
Cjx3 said:
Wow. Ok. I did not see that at all. You just add the 2!?
Thanks 🤯
Click to expand...
Where the distance above the roof to the bottom of the raceway is less than 23 mm (7⁄8 in.), a temperature adder of 33°C (60°F) shall be added to the outdoor temperature to determine the applicable ambient temperature for application of the correction factors
 
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