310.15(b)(6)

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So how do you plan on handling it? Asume worst case scenario and charge and wire for it or have a sit down with local inspector to gauge his/her interprtation and hope they see it as 215.2 seems to?
 
Dennis Alwon said:
Thom, I will tell you this, no matter what we think, Ron our head state inspector says the larger conductor is necessary. I argued with him for 1/2 hr. on it but I was unaware of art. 215.2. Personally I think (uh oh- me thinking) that art. 310.15(B)(6) got changed years ago but no one every changed 215.2. This is a total guess on my part.
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I think 215.2 backs up 310.15 (B) (6) in this context.
200amp meter base back to back with 1 200amp panel. The panel would be for all of the appliance and lighting load.

Now if you had a 200amp meter combo feeding 1 200amp panel with ser then you could not use the table for wire size and would need to up size to 350. Reason being the meter combo would void the other panel's standing as being the only one to supply appliance and lighting load.

The only fuzzy thing to me would be if there were a 200amp meter feeding a single 200amp outside disconnect that in turned fed the appliance and lighting panel.
 
ceb58 said:
I think 215.2 backs up 310.15 (B) (6) in this context.
200amp meter base back to back with 1 200amp panel. The panel would be for all of the appliance and lighting load.

Now if you had a 200amp meter combo feeding 1 200amp panel with ser then you could not use the table for wire size and would need to up size to 350. Reason being the meter combo would void the other panel's standing as being the only one to supply appliance and lighting load.

The only fuzzy thing to me would be if there were a 200amp meter feeding a single 200amp outside disconnect that in turned fed the appliance and lighting panel.
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It would be a feeder sized according to the applicable interpretation. How's that for for nice and fuzzy. :D

In all seriousness, I think 215.2 can bail you out in a single 200 amp service with remote located house panel. The 200 amp feeder would not have to be larger than your SE conductors, even in an SE cable as was pointed out because it is specifficly mentioned in 310.15. Now, when you have 400 amp service or larger with multiple 200 amp disconnecting means and feeders, the same mercy no longer exists because your house panel feeders are not going to be as large as your SE conductors. My remaining confusion is that when 310.15 talks about "for the purpose of this section..." the main feeder shall take on the entire load, the wording does include plural usage of branch circuits or feeders, implying more than one can serve the entire load. Were are back to fuzzy again. :smile: My guess is the intent was not to be multiples but a singular feeder. At least the rest of the NEC is plain and to the point. :rolleyes::D
 
When you stop and add some logical thinking to this, Why would ANY conductor in the building or on the whole property have to be any larger then the SE conductors ? With the exception of derating for temp. or VD.
 
acrwc10 said:
When you stop and add some logical thinking to this, Why would ANY conductor in the building or on the whole property have to be any larger then the SE conductors ? With the exception of derating for temp. or VD.
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That is exactly the point we are making. The fact that se cable is used as a feeder inside means the wire must be derated to the 60C and if the entire load of the house is not on the se cable then it cannot have advantage of 310.15(B)(6) and must use 310.15. Thus the wire would have to be a larger conductor size to equal the ampacity of the service conductors.
 
Dennis Alwon said:
That is exactly the point we are making. The fact that se cable is used as a feeder inside means the wire must be derated to the 60C and if the entire load of the house is not on the se cable then it cannot have advantage of 310.15(B)(6) and must use 310.15. Thus the wire would have to be a larger conductor size to equal the ampacity of the service conductors.
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But if SE is listed as an allowable cable in this table, does that not override 338 ampacities the same as it does for THHN or any other?
 
O.K. guys, this may not settle it for you, but it does for me.
I may be biased, but, to me, the final autority on all things NEC is Mr.** Chairman of CMP* In 40 years I've met no one who "knows code" better.
I was fortunate enough to get an opinion from him.

His answer is a bit lenghty but as follows (underrlined empahsis by me):

"215.2(A)(3) for individual dwelling unit or mobile home conductors states that "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." Therefore, all
things being equal this is correct. However, what if the feeder conductors were run 200 feet from service to a secondary disconnect outside the mobile home and a requirement for voltage drop was imposed and the service conductors were required to be 4/0 aluminum (180 amp calculated load) to the service disconnect and the feeder conductors were increased in size to 250 kcmil to compensate for voltage drop.
Does this impinge on 210.2(A)(3) - no. Also, what if a feeder from a
service is run through an area with a high ambient temperature such as 120-degrees F such as an attic of a dwelling. The same 4/0 conductors may be required to be increased as they now only have an allowable ampacity of 135 amperes. Does this impinge on 215.2(A)(3) - no.
Therefore, everything may not equal between service and feeder conductors in all cases and the feeder conductors may have to be increased to remain equal in either "allowable ampacity" or "rating" to the service conductors. That is the problem with the questions you have posed."
(my question)
Question 1
Service is 4/0 AL.
Outside disconnect/overcurrent with interior SER to Loadcenter.
Is a 4/0 AL SER allowable as the interior SER (using 215.2 and
310.15(B)(6) and thus ignoring the ampacity limitation on 338.10)

(***) "215.2 and 310.15(B)(6) are what they are. 310.15(B)(6) allows a "rating" of 200 amperes for 4/0 aluminum conductors. This "rating" is not an allowable ampacity such as is provided in Table 310.16 but is
what it is - just a rating. Therefore, again, everything being equal
215.2(A)(3) states that "Feeder conductors for individual dwelling units or mobile homes need not be larger than service conductors." However, we are not equal where SE cable is utilized as the feeder wiring method to the secondary distribution panelboard inside the dwelling. See
338.10(B)(4)(a) that states "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." Note that the exclusion of 334.80 per the 2005 NEC is not excluded in the 2008 NEC in this section. This is because the code panel believes that SE cable is susceptible to having the same conductor heat dissipation problems as NM cable when run in the interior of buildings in attics and walls and especially where such cable is embedded in insulation. Therefore, 4/0 aluminum SE cable has to be sized from the 60-degree ampacity column of Table 310.16 which only allows it to have an allowable ampacity of 150 amps. Therefore, if the calculated load is 180 amps the 4/0 aluminum cable would not be acceptable and a 300 kcmil aluminum conductor at 190 amperes' would be
required per Table 310.16. Again, all things are not equal between the
service on the exterior of the dwelling and the feeder run through the interior of the dwelling."

He went on to expalin that in the 2nd situation where we had part of the dwelling load fed from the outside disconenct, that 3120.16 was not applicable and that 60? ampacity had to be applied.

Pretty much elimintes 4/0 AL SER doesn't it ?
 
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While that is a perfectly reasonable analysis, I wish they would convey these thoughts in code language. The code is already rather complicated, but they should be able to find a way to cover this situation so things are "more equal". Maybe just removing SE from the list in table 310.15(B)(6), or restricting it to exterior use only, would be enough to do it, but the whole ambient temperature thing puts a cloud of confusion on 310.15(B)(6).
 
I agree. Probably why this is Pg 5 of the thread.
I dread the idea of enforcement on this. How many supply house stock 300kcmil SER ?
 
I'm not so sure the words in the holy scribbling back up the enforcement of what that guy's opinion is:-?:-?:-?

I would love to know if there is any documented case where,.. after following article 220 ,. there has been a rash of problems with a 4/0 se cable being used the way that millions are employed right now????
 
M. D. said:
I'm not so sure the words in the holy scribbling back up the enforcement of what that guy's opinion is:-?:-?:-?
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True, but, it's obviously controversial, and where can one go beyond the Chairman of a CMP to get clarification. In a legal battle I'd hate to present my meger credentials against his, plus, (I know this makes me biased), he has set me on the correct road many times in my nspection life
M. D. said:
I would love to know if there is any documented case where,.. after following article 220 ,. there has been a rash of problems with a 4/0 se cable being used the way that millions are employed right now????
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I would think that challange woud fit a majority of the Code changes.
He explained the thinking of the CMP, and agree or disagree, they make the calls.
 
so,.. I'm searching around for the one true answer and I find this ,,..Good Grief

http://www.iaei.org/subscriber/magazine/08_e/SeptemberULQuestionCorner.pdf

This pertains to meter socket listings

...this Code section provides a different ampacity table
for “3-wire, single-phase dwelling services and feeders.”
Requirements for wire bending space and the conduc-
tor size a terminal is rated to terminate are reduced to
account for the reduced size conductor.
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.......NEC Table 310.16 would require 3/0 Copper for 200
A service, while UL 414 would allow 2/0 if marked for
this application [which is in agreement with conductor
ampacities provided in NEC Table 310.15(B)(6)]. These
meter sockets have not been evaluated for applications
that go beyond this limitation.
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bump ,. wire bending space ?? resi meter cans ??? reduced ?? terminals ??listed ??

No comments:-?
 
M. D. said:
bump ,. wire bending space ?? resi meter cans ??? reduced ?? terminals ??listed ??

No comments:-?
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Yes, this is a holy mess. I brought this whole scenario up before Jan. 1 , 2008 and no one here seemed to think it was an issue. I bet by 2011 some of these issues will be resolved. I hope.
 
Dennis Alwon said:
Yes, this is a holy mess. I brought this whole scenario up before Jan. 1 , 2008 and no one here seemed to think it was an issue. I bet by 2011 some of these issues will be resolved. I hope.
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We are still under 2005 in my area, so I get a little relief from the 60 degree column on SE used in side. I think some very valid points have been made here that reinforce you can not ignore derating when conditions apply that call for derating ( like the location of, or length of a conductor ) There are lots of times where you can use 310.15(B)(6) just not all installations.
 
Dennis Alwon said:
The fact that se cable is used as a feeder inside means the wire must be derated to the 60C and if the entire load of the house is not on the se cable then it cannot have advantage of 310.15(B)(6) and must use 310.15. Thus the wire would have to be a larger conductor size to equal the ampacity of the service conductors.
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Dennis - I'm confused. My code books [ 2005, 2008, 338.10(B)(4)(a)] say
SE used inside must comply with Parts I & II of Art. 334 - excluding 334.80.

334.80 is the section that limits conductors to a 60 degree rating - if this section is excluded for the use of SE inside a dwelling, then would not the full ampacity of the SE conductor be permitted?

T310.16 indicates 4/0 AL SE conductors [XHHW in my area] have an ampacity value of 180A.

Where have I gone wrong in my reasoning? Your help would be appreciated.
 
Okay -- this was such an interesting thread I thought I would bring it back to life again.

Art. 215.2(A)(3) says what it says-- that the feeder conductors need not be larger than service conductors.

Now I believe that is taken way too literally. Think of it like this.
Scenario: I use a 2/0 copper service entrance conductor from my meter to my first MDP (this panel has feed thru lugs and one branch circuit for say an A/C unit). Now I want to use the feed thru lugs to feed anoother 200 amp panel.

Based on a literal interpretation (that many of us are using) we could use 2/0 aluminum because it is the same size as the 2/0 copper. Now we know that cannot be true so how can we argue the fact that a 3/0 copper would be needed to feed the interior panel. Yes it is larger in size but it is obvious the art. is talking about ampacity, IMO.

Does this help?
 
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