sub panel

[jim123]

installing a 100 amp sub panel from a 200 main panel. Using scr #2 alumimun 4 wire, are these wires consider a feeder or a branch circuit? Running the wires in the attic . Do I have to derate these wires because of the heat in the attic?

 

[augie47]

Welcome

Check your definitions in Art 100. A branch circuit originates at the LAST OCP device.
In most jurisdictions, 338.10 is taken into account, so your #2 AL has a connection ampacity of 75 amps. You are allowed to use the 90? ampacity for derating, so you atiic would probably not take the 90? rating to below the allowable 75 amps.

 

[ceb58]

installing a 100 amp sub panel from a 200 main panel. Using scr #2 alumimun 4 wire, are these wires consider a feeder or a branch circuit? Running the wires in the attic . Do I have to derate these wires because of the heat in the attic?

Feeders
#2 is fine as long as your OCP is not over 75 amps.
Depending on your location then derating will kick in

 

[liquidtite]

i thought d rateing was for more than 3 ccc,s in a conduit

 

[infinity]

i thought d rateing was for more than 3 ccc,s in a conduit

What they're really referencing is Ambient Temperature Correction Factors {Table 310.15(B)(2)(a)} for the attic space. We tend to use the word derating in a very broad sense.

 

[liquidtite]

ok i understand know