310.15(A)(2) Applies In Panelboards?

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Dennis Alwon

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I don't see how that can affect the ampacity. I also don't see what 30.15(A)(2) has to do with space in a panelboard
 

kwired

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I think the exception says you don't have to, unless you have more than 10 feet or more than 10 percent of circuit within the panelboard.
 

George Stolz

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I see it as applying to raceways and cables, but I fail to see how it could apply to the interior of a panelboard. IMO, the exception kwired mentioned begins taking effect at the raceway connector.

I just saw a graphic that indicated otherwise, confused me.
 

don_resqcapt19

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I see it as applying to raceways and cables, but I fail to see how it could apply to the interior of a panelboard. IMO, the exception kwired mentioned begins taking effect at the raceway connector.

I just saw a graphic that indicated otherwise, confused me.
It very clearly applies in the panel.
(2) Adjustment Factors.
(a) More Than Three Current-Carrying Conductors in a Raceway or Cable. Where the number of current-carrying conductors in a raceway or cable exceeds three, or where single conductors or multiconductor cables are installed without maintaining spacing for a continuous length longer than 600 mm (24 in.) and are not installed in raceways, the allowable ampacity of each conductor shall be reduced as shown in Table 310.15(B)(2)(a). Each current-carrying conductor of a paralleled set of conductors shall be counted as a current-carrying conductor.
 

Dennis Alwon

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IMO, Don's comment makes some sense however, the heading states more than 3 current carrying conductors in a raceway or cable... If that where the case every main distribution panel could easily warrant de-rating. I have never seen it interpreted that way as I don't believe it is the intent-- same situation for trough, jb's etc.
 

iwire

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I agree with Don that it applies to panel-boards and such.

But it really does not change anything, first of all the conductors are rarely bundled for more than 24" in a panel board, yes of course sometimes but not often.

Second as mentioned the 10%/10' rule pretty much makes it a moot point in all but the largest panels.
 

infinity

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I agree with Don and Bob, it does apply to panels and switchgear, etc. I've heard inspectors tell EC's to remove cable ties in panels for this reason. Guess they're not familiar with the 10'/10% exception.
 

George Stolz

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IMO, Don's comment makes some sense however, the heading states more than 3 current carrying conductors in a raceway or cable.
Bingo. I think the text that Don highlighted refers to cables.

(3) Adjustment Factors.
(a) More Than Three Current-Carrying Conductors in a
Raceway or Cable.
Where the number of current-carrying
conductors in a raceway or cable exceeds three
, or where
single conductors or multiconductor cables are installed
without maintaining spacing for a continuous length longer
than 600 mm (24 in.) and are not installed in raceways
, the
allowable ampacity of each conductor shall be reduced as
shown in Table 310.15(B)(3)(a). Each current-carrying conductor
of a paralleled set of conductors shall be counted as
a current-carrying conductor.
The title is "raceway or cable." The first scenario covers single conductors contained in a wiring method, and the second scenario covers cables that are not installed within a raceway for physical protection. (Edit: ) An example of a chapter 3 wiring method employing single conductors rather than cable would be USE within a trench.

A panelboard is not a raceway, particularly when the conductors originate inside that panelboard.

Thoughts? :)
 

don_resqcapt19

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Bingo. I think the text that Don highlighted refers to cables.
I agree that the heading for the section does not match the wording of the section, however the section I highlighted refers to both single conductors and cables.
(2) Adjustment Factors.
(a) More Than Three Current-Carrying Conductors in a Raceway or Cable. Where the number of current-carrying conductors in a raceway or cable exceeds three, or where single conductors or multiconductor cables are installed without maintaining spacing for a continuous length longer than 600 mm (24 in.) and are not installed in raceways, the allowable ampacity of each conductor shall be reduced as shown in Table 310.15(B)(2)(a). Each current-carrying conductor of a paralleled set of conductors shall be counted as a current-carrying conductor.
You said the panel is not a raceway and so it is my opinion that the section applies to single conductors no matter where they are installed. Maybe a proposal for the 2014 code to change the heading would clear this issue up.
 
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Dennis Alwon

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Well I see it can go either way but it is clear to me that it is NOT clear as to whether a panel was the intent. Single conductors are not always in a raceway...
 

infinity

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Are there not single conductors that are not in a raceway and not in a panel?


Sure, they're in junction boxes and as George mentioned trenches, etc. But if the section in question only applies to raceways and cables why mention single conductors not in raceways? The argument seems to be that this only applies to raceways and cables as per the wording in (3)(a).
 

Dennis Alwon

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Sure, they're in junction boxes and as George mentioned trenches, etc. But if the section in question only applies to raceways and cables why mention single conductors not in raceways? The argument seems to be that this only applies to raceways and cables as per the wording in (3)(a).

I have no idea why it is mentioned in here other than in reference to similar installs when not in a raceway. IMO, a panel was not the intent but that is only my opinion. My presumption is that they wanted to make sure de-rating also applied to non raceways.

Lets say we have a large distribution panel with 6 mains that feed 6 - 3 phase panels next to the distribution panel. All the conductor runs are 20' or less. Now if there is 3' of wire in the main distribution panel and 4 conductors per run we have at least 18 CCC in the panel.

10% of 20' is 2' and we have 3' in the panel. This is less than 10' so we must derate all those feeders at 50%. Do you think this is the intent?
 

infinity

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Lets say we have a large distribution panel with 6 mains that feed 6 - 3 phase panels next to the distribution panel. All the conductor runs are 20' or less. Now if there is 3' of wire in the main distribution panel and 4 conductors per run we have at least 18 CCC in the panel.

10% of 20' is 2' and we have 3' in the panel. This is less than 10' so we must derate all those feeders at 50%. Do you think this is the intent?

Your assumption is that these conductors meet the definition of bundled for more than 24". If they're not all physically tied together then IMO derating would not apply.
 

kwired

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NE Nebraska
I have no idea why it is mentioned in here other than in reference to similar installs when not in a raceway. IMO, a panel was not the intent but that is only my opinion. My presumption is that they wanted to make sure de-rating also applied to non raceways.

Lets say we have a large distribution panel with 6 mains that feed 6 - 3 phase panels next to the distribution panel. All the conductor runs are 20' or less. Now if there is 3' of wire in the main distribution panel and 4 conductors per run we have at least 18 CCC in the panel.

10% of 20' is 2' and we have 3' in the panel. This is less than 10' so we must derate all those feeders at 50%. Do you think this is the intent?

If they are all bundled together I think it needs consideration.

Most of the time each feeder will be bundled separately and have some space between bundles.
 

Dennis Alwon

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If they are all bundled together I think it needs consideration.

Most of the time each feeder will be bundled separately and have some space between bundles.

Well the question was asked about a panelboard. All the conductors are together but there always seems to be a space here and there so the question becomes what is bundling? and how much space is needed.

So after thinking about this I would say that if they are bundled in a panel then it would apply. I was not thinking that George was asking about bundling but rather whether the panel was considered for derating even if they were not bundled.
 

kwired

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NE Nebraska
Well the question was asked about a panelboard. All the conductors are together but there always seems to be a space here and there so the question becomes what is bundling? and how much space is needed.

So after thinking about this I would say that if they are bundled in a panel then it would apply. I was not thinking that George was asking about bundling but rather whether the panel was considered for derating even if they were not bundled.

Aux gutters and wireways do not require derating for number of conductors if there are not more than 30 current carrying conductors. They also have a 20 percent fill requirement where raceways is 40 percent fill.

Where wiring space in a panelboard is used as a wireway pretty much same rules apply.

Can you call the space in the panelboard the same as a wireway? Maybe not. There are some similarities though.
 
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