338.10

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338.10

  • 338.10 will apply and service cables meet 60? ampacity (ie: 300 mkcmil AL for 200 amp)

    Votes: 2 12.5%
  • 310.15(B)(6) takes precedence and 4/0 Al may be used on interior service cables for 200 amp

    Votes: 14 87.5%

  • Total voters
    16
  • Poll closed .
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augie47

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Staff member
Location
Tennessee
Occupation
State Electrical Inspector (Retired)
In a recent thead there was a discussion on application of 338.10 ('08 Code) http://forums.mikeholt.com/showthread.php?t=107984&highlight=338.10
Opinions varied concerning having to use the 60? ampacity rating on interior SER that was used full load service or feeder, or being able to apply 310.15(B)(6) irrespective if 338.10
I am curious as to how many inspectors plan to enforce the 60? ampacity rating on "feeder that supply all loads associated with dwelling units" or allow ampacities per 310.15(B)(6)
 
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raider1

Senior Member
Staff member
Location
Logan, Utah
If the feeder meets all the requirements of 310.15(B)(6) then you are permitted to use the Table 310.15(B)(6) to size the main power feeder.

If the feeder does not meet the requirements for a main power feeder as specified in 310.15(B)(6) then you must use the 60 degree column of 310.16 for the ampacity of the feeder.

Chris
 

elohr46

Senior Member
Location
square one
If the feeder meets all the requirements of 310.15(B)(6) then you are permitted to use the Table 310.15(B)(6) to size the main power feeder.

If the feeder does not meet the requirements for a main power feeder as specified in 310.15(B)(6) then you must use the 60 degree column of 310.16 for the ampacity of the feeder.

Chris


I agree with this post. 2008 nec
 

charlie b

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Location
Lockport, IL
Occupation
Retired Electrical Engineer
I still don't understand the problem. 338.10(B)(4) talks about installation methods, not ampacity. It does lead you to 334, and there is a discussion of ampacity there (334.80). But that discussion is limited to types NM, NMC, and NMS, and nothing causes that discussion to apply to SE or SEU.

I also don't understand why you are (and have been) talking about 300 MCM AL in the same sentences as a 200 amp service, since it is only good for 190 amps.

I don't see anything in 338.10 that would prevent us from applying 310.15(B)(6), provided only that we meet the restrictions of that article (i.e., the service or feeder must supply all loads in the dwelling unit). So I suppose I am agreeing with Chris and (saints preserve us!:wink:) with Bob.
 
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Dennis Alwon

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Location
Chapel Hill, NC
Occupation
Retired Electrical Contractor
Gus if you look at T310.15(B)(6) heading it includes se cable. Given the entire load of the house then the table stands alone. The table does not state only 90 C wiring. I believe it is an over site however since there are no conductors listed as 60 C in that heading. I would not be surprised if that changes in the next cycle if they don't recind the se cable rule in 338.10.
 

Dennis Alwon

Moderator
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Location
Chapel Hill, NC
Occupation
Retired Electrical Contractor
SE is still rated 90C.

You are correct, of course, but my understandiing is that entering the building where the cable runs thru the insulation etc. was the reason for the change. If this is indeed the intent then I believe there could be some changes in the future in regards to this. In other words, the se cable will affect feeders as well as se cable used as service conductors.
 

iwire

Moderator
Staff member
Location
Massachusetts
You are correct, of course, but my understandiing is that entering the building where the cable runs thru the insulation etc. was the reason for the change. If this is indeed the intent then I believe there could be some changes in the future in regards to this. In other words, the se cable will affect feeders as well as se cable used as service conductors.

You lost me. :confused: (not hard some days:smile:)

It is my understanding the issue with interior cables with non-metallic sheath construction is they get buried in insulation and you get heat build up. That is not something that can happen with service entrance conductors given the nearest the point of entrance requirements.

That said, I see the NEC as only becoming more restrictive with temperature limitations so who knows. :smile:
 

Dennis Alwon

Moderator
Staff member
Location
Chapel Hill, NC
Occupation
Retired Electrical Contractor
It is my understanding the issue with interior cables with non-metallic sheath construction is they get buried in insulation and you get heat build up. That is not something that can happen with service entrance conductors given the nearest the point of entrance requirements.

I think it can be buried in insulation and often is around here esp. if the panel is on an exterior wall and a few feet higher than the meter.
 

augie47

Moderator
Staff member
Location
Tennessee
Occupation
State Electrical Inspector (Retired)
Gus if you look at T310.15(B)(6) heading it includes se cable. Given the entire load of the house then the table stands alone. The table does not state only 90 C wiring. I believe it is an over site however since there are no conductors listed as 60 C in that heading. I would not be surprised if that changes in the next cycle if they don't recind the se cable rule in 338.10.

I agree Dennis. As noted in post #1, this goes back to an earlier post ( http://forums.mikeholt.com/showthread.php?t=107984&highlight=338.10 )
in which John Minick of CMP1 made a point that the 60? rating must be taken into account and a 4/0 AL "full load" feeder was not suffcient.
I posted the poll simply to see how many agreed with that interpretation.
Jeff Posey of Southwire summed it up by saying it was a mess and the CMP memebers associated with Southwire were working on it.
It was and is not my intent to rehash the original post.
I happen to agree with Mr. Minick, but apparently we are very much in a minority on the Forum :D
 
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