320/400 service

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ofourcobra

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Hey guys doing a project and I have to upgrade the service from 200 to 320/400. I will have a 320/400 meter socket and enter the house with 2-4/0 alum SEUs, one to feed existing 200 amp panel directly adjacent to the meter, and the other to feed a 200 disconnect for a subpanel that will be located on the other side of the house . My issue is with the size of the SER I will be running to the panel on other side of the house , since it will be in insulation and run through 20 feet of hot attic . I've combed through the forums to figure it out on my own but I'm still confused on this whole thing . I'm in mass and we are on the 2017 if that helps , thanks in advance .


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The 2017 has changed things and it is now rated 75C. Remember that even at 75C 4/0 is only rated 180 amps so you really are limited to 360 amps. You still can use 200 amp breakers based on 240.4(B)


338.10(4) Installation Methods for Branch Circuits and Feeders.
(a) Interior Installations. In addition to the provisions of
this article, Type SE service-entrance cable used for interior
wiring shall comply with the installation requirements of Part II
of Article 334, excluding 334.80.
For Type SE cable with ungrounded conductor sizes 10 AWG
and smaller, where installed in thermal insulation, the ampacity
shall be in accordance with 60°C (140°F) conductor temperature
rating. The maximum conductor temperature rating shall
be permitted to be used for ampacity adjustment and correction
purposes, if the final derated ampacity does not exceed
that for a 60°C (140°F) rated conductor
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Dennis Alwon said:
The 2017 has changed things and it is now rated 75C. Remember that even at 75C 4/0 is only rated 180 amps so you really are limited to 360 amps. You still can use 200 amp breakers based on 240.4(B)
Click to expand...

Is this for 1 or 7 seu's in parallel and does this mean calculated load must be 360 or less with 2-4/0 seu al's ?


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Minus what ever temperature correction I get for running through the attic as well?


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