# #4 cu for 100a sub-panel



## 3xdad (Jan 25, 2011)

still is fine for single phase resi. 310.15(B)(7) 2011

Or are you referring to the 100% load thing?


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## Julius793 (Nov 29, 2011)

3xdad said:


> still is fine for single phase resi. 310.15(B)(7) 2011
> 
> Or are you referring to the 100% load thing?


Isn't that table only for the main feeder and not for a sub?


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## 3xdad (Jan 25, 2011)

i consider the panels that 4 wire feeders supply to be sub panels, but i get what you are say'in.

Others will correct if i'm wrong, but the way i understand it is, lets say you have a 100 amp meter main with no other circuit spaces. Then you can use #4Cu for the feeder to what i would call a sub panel because that feeder will carry 100% of the load and does not need to be larger than the SEC's.

If you have a meter combo with the 100 amp disco and circuit spaces in the service equipment and you want to take a 100 amp feeder to a sub, then yeah, #3Cu.

To answer your original question, yeah, i think that just changed with the 2011.


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## kbatku (Oct 18, 2011)

You can only "uprate" #4 if it's the main service. Subpanels - no bueno. It's only good for what - 85 amps? 

And yes, it "used to be OK" because the inspectors hadn't caught on yet (or something) . Now they'll call it all day long...


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## Cletis (Aug 20, 2010)

*ref*



3xdad said:


> i consider the panels that 4 wire feeders supply to be sub panels, but i get what you are say'in.
> 
> Others will correct if i'm wrong, but the way i understand it is, lets say you have a 100 amp meter main with no other circuit spaces. Then you can use #4Cu for the feeder to what i would call a sub panel because that feeder will carry 100% of the load and does not need to be larger than the SEC's.
> 
> ...


Code ref? Look at my feeder thread as well. It is a main feed thru. Is that in 215 somewhere??


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## Dennis Alwon (May 9, 2009)

kbatku said:


> You can only "uprate" #4 if it's the main service. Subpanels - no bueno. It's only good for what - 85 amps?
> 
> And yes, it "used to be OK" because the inspectors hadn't caught on yet (or something) . Now they'll call it all day long...


This is not correct. 3Xdad has it correct. If the subpanels carries the entire load of the dwelling then the panel may use T. 310.15(B)(6) otherwise you have to use T. 310.16. Ref. art. 310(15)(B)(6)- 2008------------ (B)(7) in 2011


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## Dennis Alwon (May 9, 2009)

I had to move the other posts to the appropriate thread. Sorry


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## kbatku (Oct 18, 2011)

Thanks Dennis -I didn't read closely enough. I was thinking of a subpanel coming off another panel (duh!). My bad.


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