Residental service conductor size

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JdoubleU

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Does this look right to size my wire? 200 amp service single family dwelling using ser cable AL. 200 x .83 = 166. 310.15(B)(16). 60 degree column for aluminum would be 250 KCmil. If this is true why do most use 4/0, 4/0, 4/0, 2/0?
 
JdoubleU said:
Does this look right to size my wire? 200 amp service single family dwelling using ser cable AL. 200 x .83 = 166. 310.15(B)(16). 60 degree column for aluminum would be 250 KCmil. If this is true why do most use 4/0, 4/0, 4/0, 2/0?
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Before the last code the NEC stated that 4/0 could be used for single family dwelling and the table never mentioned having to look at any column in particular and didn't take into consideration any de-rating factors. The 83% now considers the de-rating
 
You have zeroed in on a controversial Code Section that has been cussed and discussed a length since Art 338.10 was modified in 2008. There was debate prior to 310.15(B)(7) being changed to the "83%" rule. Meanwhile 338.10 was modified to SE only being 60° when installed in insulation.
FWIW, I would agree with your post if the SE is insulation and taking into account 310.15(A)(2) exception.
In most installs the 75° ampacity can be used as Jumper pointed out
 
augie47 said:
You have zeroed in on a controversial Code Section that has been cussed and discussed a length since Art 338.10 was modified in 2008. There was debate prior to 310.15(B)(7) being changed to the "83%" rule. Meanwhile 338.10 was modified to SE only being 60° when installed in insulation.
FWIW, I would agree with your post if the SE is insulation and taking into account 310.15(A)(2) exception.
In most installs the 75° ampacity can be used as Jumper pointed out
Click to expand...

Yes, this has been changing over the code cycles and led to a lot of confusion. Under the 2014 the OP is right that if he could not meet 310.15(A)(2) he would have to use the 60 degree column. Under the 2017 4/0 will work as 338.10(B)(4) language has been changed to allow use at 75 degree in insulation if larger than #10.
 
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