We are having some varied opinions on a couple of issues. According to 310.15(B) (6), Table 310.15(B) (6) allows 4/0 Aluminum Type SE to be installed to serve a 200 amp dwelling service.
338.10 (B) (4) (a) requires Type SE service-entrance cable used for interior wiring (feeders or branch circuits) to comply with the installation requirements of Part II of Article 334 (specifically 334.80).
4/0 Aluminum in the 60 degree column is rated for 150 amps (a standard fuse or breaker size).
Would a 4 wire 4/0 Type SE (SER) be permitted to be installed through the attic of a dwelling, protected by an exterior 200 amp main breaker to feed the service panel that carries the entire load of the dwelling, or would a 300 kcmil Aluminum SE cable be required.
Would not “215.2 (A) (3) Individual Dwelling Unit or Mobile Home Conductors. Feeder conductors for individual dwelling units or mobile homes need not be larger than service conductors. Paragraph 310.15(B)(6) shall be permitted to be used for conductor size.” allow the SE cable to be the same size as the Aluminum 4/0 THHN/THWN/MTW that would be installed in the riser and the nipple between the meter and the main breaker.
How are you guys looking at this?

TY
Neal Burdick
City of Tampa
Construction Inspector

I believe the feeder that is simply an extension of the service entrance beyond a disconnect/OC device is still covered by 310.15(B)(6).


seems pretty unambiguous.

I agree with Gregg.

I doesn't make sense nor seems to be the intent of the code to require the feeder extending to the inside portion of the dwelling to be sized larger than the service-entrance or per 310.16 instead of 310.15(B)(6).

It seems to be an unitended consequence of requiring SE cables to comply with the 334.80 requirement, which for the most part is a good thing. I just don't think it should apply to feeders that would otherwise be pemitted to be sized under 310.15(B)(6).

However, any other feeder, other than the "main power feeder", would have to comply with 334.80 / 310.16 for sure.

I agree. #4/0 al SER feeders from the 200 amp main to the distribution panel or subpanel are clearly intended. Attic ambient temperature in Florida attics should be considered and say 140*F is 0.71 derating of 300KcMil al. XHHW @ 90*C is 255amps x 0.71 = 179amps on a 200amp MCB...I know that the City of Lakeland will not allow PVC conduit in attics...right Terry? It amazes me that the old clothbraided Romex with paper and rubber wrapped conductors is still in service in many Florida attics...

How does the city of Lakeland get to amend NFPA 70 without going through Tallahassee?

BTW I am impressed with how well the old Romex does hold up in a Florida attic. I have removed some recently that was installed for 45 years and it is still in pretty good shape. The insulation looks good but the paper jacket seems a little more brittle than it was, new.

I don't think Lakeland is actually amending the NEC but just strickly enforcing Section 352.12(D) limiting PVC installations to 122 degrees F.

There are numerous incidents thruout the country where the AHJ directs specific limitations not in the book. I would list them under 'judgement calls' or 'grandfather clauses'. Truth is that whenever one crosses a jurisdictional line some rules change. A contractor could argue based upon adopted Code but most will choose to expedite the project and make the required changes....I did. I am fully in favor of uniform Code and inforcement but am realistic in that training and judgement varies greatly. The intelligent contractor calls ahead to the jurisdiction to inquire of any 'local Codes'.

Thanks Bryan, I never thought about that. I have questioned derating in attics tho.

I suppose if you really used a sharp pencil on thee 122f thing there are lots of places you can't use RNC. Pretty much anywhere the sun hits it for one.

The utility companies along with the FL solar institute have done studies on attic temps.
You would be surprised on how much it varies from the bottom cord to the top cord of the truss.
And it varies quit a bit on how much ventilation the attic has.
Along the bottom cord(where most all the wiring is) it is not as hot as you may think.

Progress energy has a statement on attic temps.


HERE is a report by the Florida Solar Center.

I agree, If the wiring is on the home side of the insulation it might not be much warmer than the ceiling