SER cable for 200A subpanel that does not feed entire dwelling

[tortuga]

Am I correct that it is generally no longer possible to run a Aluminum 200A SER cable for a feeder that does not serve an entire dwelling and would be required to run through some insulation in an attic?
The Scenario:
I have a 200A meter/main service disconnect that also has room for 8 breakers that will be installed on the exterior of a dwelling.
It has feed thru lugs for a indoor 200A panel. That loadcenter is called out a ways inside the dwelling.
Since some outdoor loads and the range will be landed in the outdoor meter/main the "entire" dwelling will not be supplied from the feeder.
338.10(B) States we must use 60C column for ampacity if contact with insulation.
Now the cable is going in an attic space and could possibly be run above the insulation.
Assume the AHJ will interpret it as in contact with insulation for this discussion.
SER is not made over 250kcmil
http://www.southwire.com/ProductCatalog/XTEInterfaceServlet?contentKey=prodcatsheet273

310.15(B)(16) lists 250kcmil AL at 170A under 60C
240.6 States 175 is a standard size breaker.
So we would need a 300kcmil SER cable to use the feed through lugs protected by the 200A main.
So if you want to run a 200A feeder in thermal insulation it has to be in conduit of some type.

Just need to think this through

Thoughts?

 

[Dennis Alwon]

This has been an issue and I agree with what you are saying. First off you need to know what code cycle you are under. If SER is allowed at 75C then IMO, if you run the wire ontop of the joist that is not an issue. Now where you penetrate the attic the ser will be in insulation but art. 310.15(A)(2) will probably allow that without de-rating.

BTW, this is why I usually run conduit.

 

[augie47]

When faced with the scenario you present, I am beginning to see more E/Cs install 125 amp or 150 amp breakers in the outside load centers to feed an interior panel.

 

[MasterTheNEC]

Be aware that Section 338.10(B)(4)(a) does not say "in contact with" it says "Where installed in" thermal insulation. Either an oversight or intended, it does not have the same language that you see like in Section 334.80 and how you are referencing it. In regards to the use of Section 310.15(A)(2), it is applicable for the portions of the Type SE Cable that will be installed "IN" thermal insulation if needing the relief of that section and you know how to apply it.

You are correct in your assumption that it would not comply with Section 310.15(B)(7).

However, you could simple make it a feeder on a circuit breaker and keep in mind that the next size up rules can be applied as long as the calculated load does not exceed the ampacity rating of the conductor. For example, a 4/0 AL SER has an ampacity at the 75 degree column of 180 amps and assuming the use of 310.15(A)(2) gets you past those small portions where you need to get through the insulation into the attic space.....so if you accept that Section 310.15(A)(2) applies then you still have a conductor that is good for 180 amps @ 75 C that can be terminated on a 200A OCPD per Section 240.6(A) and 240.4(B)....just don't exceed 180 amps of load on the conductors. (keep in mind nothing was mentioned about ambient temperature corrections in the attic space...because it was not asked)

P.S. Don't overlook the rules for Feeders in Article 215 either...most notably Section 215.2(A)(1)(a) and (b).....good luck on your installation.

 

[tortuga]

This has been an issue and I agree with what you are saying. First off you need to know what code cycle you are under.

2014

BTW, this is why I usually run conduit.

Yes I agree

Be aware that Section 338.10(B)(4)(a) does not say "in contact with" it says "Where installed in" thermal insulation. Either an oversight or intended, it does not have the same language that you see like in Section 334.80

Excellent point! Thank you.

and how you are referencing it. In regards to the use of Section 310.15(A)(2), it is applicable for the portions of the Type SE Cable that will be installed "IN" thermal insulation if needing the relief of that section and you know how to apply it.

You are correct in your assumption that it would not comply with Section 310.15(B)(7).

However, you could simple make it a feeder on a circuit breaker and keep in mind that the next size up rules can be applied as long as the calculated load does not exceed the ampacity rating of the conductor. For example, a 4/0 AL SER has an ampacity at the 75 degree column of 180 amps and assuming the use of 310.15(A)(2) gets you past those small portions where you need to get through the insulation into the attic space.....so if you accept that Section 310.15(A)(2) applies then you still have a conductor that is good for 180 amps @ 75 C that can be terminated on a 200A OCPD per Section 240.6(A) and 240.4(B)....just don't exceed 180 amps of load on the conductors.

Yes good points, it would be a feeder since there would be a 200A main ahead.

(keep in mind nothing was mentioned about ambient temperature corrections in the attic space...because it was not asked)

P.S. Don't overlook the rules for Feeders in Article 215 either...most notably Section 215.2(A)(1)(a) and (b).....good luck on your installation.

Yes that is a consideration, I am sure the load calc would be around 100A or less, home owners and general contractors are just used to seeing 200A panels and those feed thru lugs work so well, however since there would be a 200A panel outside. If It looks like we have to run "in" insulation I could easily run the numbers and do as Augie suggested a 2/0 ser cable on a 125A breaker ( the largest Siemens that I can install in the outdoor loadcenter)

Thank you all for you insights