310.15(B)(7) for sizing a sub-feeder that serves same dwelling?

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TedElectric

TedElectric

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Location
Florida
Occupation
Electrical Contractor
Hello all!
First time poster here but longtime fan of this forum.
I have a 200amp, main breaker, exterior panel on an existing home. We are in the process of re-wiring entire house to get rid of all cloth wiring. Anyway, we will have a new 100-amp sub-panel that will feed off the original 200. It will serve the kitchen and laundry room. The calculated load of sub-panel came out to be 80 amps. The service cable will be approximately a 15-foot run. That said, was I wrong in using "83% rule"? I submitted a drawing to local municipality showing a #2 Al SER cable feeding said panel and it was accepted. The more a think about it though, I believe it may incorrect since the panel will not be carrying the entire load of residence as stated in 310.15(B)(7).
Any input would be much appreciated.

Thank You!
Ted
 
You are correct you cannot use the table but just install a 90 amp breaker and you are good to go. BTW, welcome to the forum
 
LarryFine said:
Replacing the feeder may well be cheaper than a new breaker.
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Yes on a 15' run probably so unless he can swap the breaker out. Also if the wire is in the wall and covered it might not be that easy but certainly and option. Since he is an electrician I suspect he'll figure that out. haha
 
We have not pulled the feeder yet. Walls still open, just want to do the right / best thing. Leaning toward #1 AL cable with 100-amp breaker.

Thank You all for your input!
 
TedElectric said:
We have not pulled the feeder yet. Walls still open, just want to do the right / best thing. Leaning toward #1 AL cable with 100-amp breaker.

Thank You all for your input!
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The #1 AL is not readily accessible in my area so I usually go with the 90 amp breaker on the #2 AL. None the supply houses carry #1 for some reason, and not sure why.
 
Yes, I was concerned about availability. We are having a fit trying to find some supplies right now, very stressful.
We were in luck today though! My helper scored a 20' cut of 1-1-1-3 service cable and a 100-amp breaker at the local supply house. The service change will go down tomorrow morning, along with pulling/landing the sub-feeder! Again, thank you all for the input and advice.
 
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