sub-panel feeder code section?

[iwire]

Oh I don't mind, I'm actually having fun with this one, no name calling so far.

If I remember correctly you own big guns, I will not be name calling. :grin:

Right and also because the coductors almost never see full demand load approaching their ampacity

I sure don't see a bunch of homes burning down over this issue.

Here is what the CMP said about the changes for the 2008.

Panel Statement: The panel agrees that the present wording is ambiguous. It is the panel’s intent that this allowance apply only to conductors carrying 100% of the dwelling unit’s diversified load.

"Revised in the '96 code, Note 3 now permits the main feeder to a dwelling unit to be sized based on the conductor sizes in the the Table for Note 3, even if other loads, such as ac units and pool loads, are fed from the same service." That's from the "96 handbook.

Handbook, shmandbook that ain't code. :grin:

 

[cowboyjwc]

If I remember correctly you own big guns, I will not be name calling. :grin:





I sure don't see a bunch of homes burning down over this issue.

Here is what the CMP said about the changes for the 2008.







Handbook, shmandbook that ain't code. :grin:

A bunch of them and I have a mean wife, which is partially the reason for the guns.:grin:

Me either and I don't see a lot of it anyways most of the time the old panel is removed or made into a j-box.

I know I know and I expected that when I typed it, but I've been to seminars and meetings where Mark Earley and/or Jeff Sargent have taught and I give them enough respect to think they might have the insight into what the intents of the codes are. But heck, I've been wrong before, see first answer.

 

[Pierre C Belarge]

A bunch of them and I have a mean wife, which is partially the reason for the guns.:grin:

John
That is a good laugh...good enough that now I will go to sleep.

 

[cowboyjwc]

Ok, to be fair, I called the electrical inspector in another jurisdiction who also teaches the code class at the local college and he said I was correct.

Now not to gloat, I want you to ask around and see what you come up with.

 

[Dennis Alwon]

Ok, to be fair, I called the electrical inspector in another jurisdiction who also teaches the code class at the local college and he said I was correct.

Now not to gloat, I want you to ask around and see what you come up with.

Gloat all you want. Why Not? I don't agree with your answer but I respect it. Around here (every jurisdiction I work in) you would not be gloating but getting a red tag.

Can you give a red tag to an ionspector???:grin:

 

[cowboyjwc]

Can you give a red tag to an ionspector???:grin:

We could trade them. :grin:

I once threated the Gas Company with a red tag if they didn't fix something after we had told them twice, they said go ahead, but trust us it's going to be a long cold winter at your house. LOL

 

[iwire]

Ok, to be fair, I called the electrical inspector in another jurisdiction who also teaches the code class at the local college and he said I was correct.

Is he teaching the 2005 or 2008?

I know he did not see the CMP statement.:grin:

 

[glene77is]

iWire,


Any chance of using a diagram?
I wonder if you guys are talking about the exact same thing.

In years past, I have taken a diagram/drawing to the Code office
and had an opinion given (before installation).

 

[Dennis Alwon]

iWire,
Any chance of using a diagram?
I wonder if you guys are talking about the exact same thing.

In years past, I have taken a diagram/drawing to the Code office
and had an opinion given (before installation).

We are talking about the same thing. We have had this argument many times but to me it is very clear with the wording in art. 310.15(B)(6). It is even highlighted in the 2008.

 

[electricmanscott]

We are talking about the same thing. We have had this argument many times but to me it is very clear with the wording in art. 310.15(B)(6). It is even highlighted in the 2008.

I'm with you Dennis. I don't see how this can be so misinterpreted by so many. It's pretty clear.

 

[norcal]

Here is a copy & paste from the 2008 NEC, it's unchanged from the 2005 edition.


(6) 120/240-Volt, 3-Wire, Single-Phase Dwelling Services
and Feeders. For individual dwelling units of onefamily,
two-family, and multifamily dwellings, conductors,
as listed in Table 310.15(B)(6), shall be permitted as
120/240-volt, 3-wire, single-phase service-entrance conductors,
service-lateral conductors, and feeder conductors
that serve as the main power feeder to each dwelling unit
and are installed in raceway or cable with or without an
equipment grounding conductor. For application of this section,
the main power feeder shall be the feeder between the main disconnect and the panelboard that supplies, either by
branch circuits or by feeders, or both, all loads that are part
or associated with the dwelling unit. The feeder conductors
to a dwelling unit shall not be required to have an allowable
ampacity rating greater than their service-entrance conductors.
The grounded conductor shall be permitted to be
smaller than the ungrounded conductors, provided the requirements
of 215.2, 220.61, and 230.42 are met.


Unless a panel is carrying the entire load in a dwelling there is no way that undersizing the conductors allowed by 301.15(B)(6) is allowed.

 

[Dennis Alwon]

Here is a copy & paste from the 2008 NEC, it's unchanged from the 2005 edition.

The highlighted section below is what changed from 2005 to 2008.

310.15(B)(6) 120/240-Volt, 3-Wire, Single-Phase Dwelling Services
and Feeders. For individual dwelling units of onefamily,
two-family, and multifamily dwellings, conductors,
as listed in Table 310.15(B)(6), shall be permitted as
120/240-volt, 3-wire, single-phase service-entrance conductors,
service-lateral conductors, and feeder conductors
that serve as the main power feeder to each dwelling unit
and are installed in raceway or cable with or without an
equipment grounding conductor. For application of this section,
the main power feeder shall be the feeder between the main disconnect and the panelboard that supplies, either by
branch circuits or by feeders, or both, all loads that are part
or associated with the dwelling unit. The feeder conductors
to a dwelling unit shall not be required to have an allowable
ampacity rating greater than their service-entrance conductors.
The grounded conductor shall be permitted to be
smaller than the ungrounded conductors, provided the requirements
of 215.2, 220.61, and 230.42 are met.

 

[roger]

Here is a copy & paste from the 2008 NEC, it's unchanged from the 2005 edition.

Well, actually there was a small change in the wording as shown below.



2005

(6) 120/240-Volt, 3-Wire, Single-Phase Dwelling Services and Feeders For individual dwelling units of one family, two-family, and multifamily dwellings, conductors, as listed in Table 310.15(B)(6), shall be permitted as 120/240-volt, 3-wire, single-phase service-entrance conductors, service lateral conductors, and feeder conductors that serve as the main power feeder to each dwelling unit and are installed in raceway or cable with or without an equipment grounding conductor. For application of this section, the main power feeder shall be the feeder(s) between the main disconnect and the lighting and appliance branch-circuit panelboards(s). The feeder conductors to a dwelling unit shall not be required to have an allowable ampacity rating greater than their service-entrance conductors. The grounded conductor shall be permitted to be smaller than the ungrounded conductors, provided the requirements of 215.2, 220.61, and 230.42 are met.

2008

(6) 120/240-Volt, 3-Wire, Single-Phase Dwelling Services and Feeders. For individual dwelling units of one-family, two-family, and multifamily dwellings, conductors, as listed in Table 310.15(B)(6), shall be permitted as 120/240-volt, 3-wire, single-phase service-entrance conductors, service-lateral conductors, and feeder conductors that serve as the main power feeder to each dwelling unit and are installed in raceway or cable with or without an equipment grounding conductor. For application of this section, the main power feeder shall be the feeder between the main disconnect and the panelboard that supplies, either by branch circuits or by feeders, or both, all loads that are part or associated with the dwelling unit. The feeder conductors to a dwelling unit shall not be required to have an allowable ampacity rating greater than their service-entrance conductors. The grounded conductor shall be permitted to be smaller than the ungrounded conductors, provided the requirements of 215.2, 220.61, and 230.42 are met.

Unless a panel is carrying the entire load in a dwelling there is no way that undersizing the conductors allowed by 301.15(B)(6) is allowed.

And I agree.

Roger

 

[roger]

Sorry Dennis, I didn't see your post.

Roger

 

[cowboyjwc]

He said the same thing I did that it's been in the code since '93, which cycle he's teaching doesn't matter.

I know it's been misinterpreted, I can't understand how all of you can be so wrong.

(6) 120/240-Volt, 3-Wire, Single-Phase Dwelling Services and Feeders. For individual dwelling units of one-family, two-family, and multifamily dwellings, conductors, as listed in Table 310.15(B)(6), shall be permitted as 120/240-volt, 3-wire, single-phase service-entrance conductors, service-lateral conductors, and feeder conductors that serve as the main power feeder to each dwelling unit and are installed in raceway or cable with or without an equipment grounding conductor. For application of this section, the main power feeder shall be the feeder between the main disconnect and the panelboard that supplies, either by branch circuits or by feeders, or both, all loads that are part or associated with the dwelling unit. The feeder conductors to a dwelling unit shall not be required to have an allowable ampacity rating greater than their service-entrance conductors. The grounded conductor shall be permitted to be smaller than the ungrounded conductors, provided the requirements of 215.2, 220.61, and 230.42 are met.

Remember that a pool is not associated with the dwelling unit a pool is a seperate structure.

 

[roger]

Remember that a pool is not associated with the dwelling unit a pool is a seperate structure.

Exactly, and that is another reason 310.15(B)(6) can not be used, you need to remember that a pool is not a dwelling.

(6) 120/240-Volt, 3-Wire, Single-Phase Dwelling Services and Feeders

310.15(B)(6) is only for a dwelling, nothing else.

Roger

 

[Pierre C Belarge]

John
You have just been duly demoted...until you step away from the dark side of the code



I too cannot understand how this is so misunderstood.

and John...who cares about the '93 NEC. What is relevant is the '08.

 

[brentk]

I will say that this is a section I have never spent the time really thinking about. To me it has been the "accepted way to do things" that 310.15(B)(6) would not be used beyond the service entrance conductors. However I can see Johns point.

Example:
A 200 amp service disconnect panel on the outside of the dwelling, an A/C unit sits alongside and is fed from this panel. There is also the "normal" 200 amp panel inside the dwelling being fed from this service disconnect as well. Because the feeders going to the panel inside the dwelling are not required to be larger than the service entrance conductors the sizing according to 310.15(B)(6) is acceptable.

 

[Dennis Alwon]

Because the feeders going to the panel inside the dwelling are not required to be larger than the service entrance conductors the sizing according to 310.15(B)(6) is acceptable.

Here is the exact wording.

The feeder conductors to a dwelling unit shall not be required to have an allowable ampacity rating greater than their service-entrance conductors.

Now if you install a 200 amp service with 2/0 copper, per T. 310.15(B)(6), and we install an 8 cir. panel with feed thru lugs, then we can install 2/0 copper to the interior panel. Now feed an a/c unit from the exterior box then, IMO, you must use 3/0 copper to the interior panel.

I agree it makes no sense but here is why. The paragraph above states the feeder does not have to have an allowable ampacity greater than the service. Well when the feeder is wired to a subpanel that does not carry the entire load of the house then T. 310.15(B)(6) cannot be use and 310.16 must be used. The wire may be larger in size but the allowable ampacity is not greater.

Now you say what about 215.2(A)(3)

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.

What does larger mean. Can I now use, in the same scenario as above, a 2/0 aluminimum because that is not larger than 2/0 copper. Or must I use 4/0 aluminum which is larger than my 2/0 copper conductors.

This article tells us we can use art. 310.15(B)(6) not T. 310.15(B)(6). If the article allows it then we can use the Table.

I know my point is bizarre but I truly believe that art. 215.2(A)(3) was never changed when article 310.15.(B)(6) was changed. I think it was an oversight but still not clear enough.

This, of course, is a different issue than using T. 310.15(B)(6) for any sub panel. I hope we all see that that is not allowed.

Okay, I am done with the soap.

 

[brentk]

I will add that while I see Johns perspective here, I will continue doing things as usual. This is definitely NOT an issue to me that is worth seeing a red tag over and then trying to convince the inspector that it should be accepted or ultimately have to change out.

On another note I would like to thank everyone for the insightful debate on issues. Since joining the forum I have just browsed a fair bit without joining in too much and I appreciate being able to learn about different portions of electrical work I have not had the opportunity to experience first hand.