Wireway Sizing Straight pull

[macmikeman]

I myself have to question that particular wireway, but not for any code reason. Why not run the 3 flex conduits strait to the xfmr in the first place and not worry about having a code violation? Save 50 bucks. P.S. if it was because of that rectangular ko in the bottom left side of the tranny, I know you know how to plug that.....

 

[infinity]

I myself have to question that particular wireway, but not for any code reason. Why not run the 3 flex conduits strait to the xfmr in the first place and not worry about having a code violation? Save 50 bucks. P.S. if it was because of that rectangular ko in the bottom left side of the tranny, I know you know how to plug that.....

If I remember correctly the transformer had some sort of label on the inside that prohibited the cable entry above a certain point so the conductors needed to enter near the bottom. That's why the wireway was used.

 

[macmikeman]

If I remember correctly the transformer had some sort of label on the inside that prohibited the cable entry above a certain point so the conductors needed to enter near the bottom. That's why the wireway was used.

And the reason why you were not able to make the 3 ko's in the panel lower in order to achieve that requirement was____________?

 

[yired29]

The exception to 310.15(A)(2) should take care of that since those bundled conductors were all well over 100'.

I like the rationale about the conductors being placed in an auxiliary gutter.

I always understood the exception to 310.15 (A) (2) was to deal with ambient temperature and the correction factors in table 310.16. 310.15 (B) (2) (a) deal with current carrying conductors.

 

[augie47]

320.15(A)(2) being under "General" would apply to all conditions.

 

[yired29]

320.15(A)(2) being under "General" would apply to all conditions.

Then when does chapter 9 note 4 matter. 2 foot nipples are always less than 10' 0r 10% which ever is less of the total run. Why cant they be 3 feet but inspectors will call this a violation.

 

[hardworkingstiff]

Then when does chapter 9 note 4 matter. 2 foot nipples are always less than 10' 0r 10% which ever is less of the total run. Why cant they be 3 feet but inspectors will call this a violation.

I believe you have a point here, I look forward to seeing rebuttals.

 

[infinity]

320.15(A)(2) being under "General" would apply to all conditions.

Then when does chapter 9 note 4 matter. 2 foot nipples are always less than 10' 0r 10% which ever is less of the total run. Why cant they be 3 feet but inspectors will call this a violation.

Augie has it right, this is a general rule regarding the ampacity of conductors.

A 3' nipple in the run would be no different than those conductors bundled for 3' or are running through a higher ambient temperature for 3'. In any case the exception to 310.15(A)(2) would still apply. I would assume that an inspector should know this but but I'm guessing that not all do.

 

[hardworkingstiff]

Augie has it right, this is a general rule regarding the ampacity of conductors.

A 3' nipple in the run would be no different than those conductors bundled for 3' or are running through a higher ambient temperature for 3'. In any case the exception to 310.15(A)(2) would still apply. I would assume that an inspector should know this but but I'm guessing that not all do.

Rob,

You are much more educated on the Code than I, but yired29 has a point and it makes sense to me. With most lengths of conductors, when would the 2' rule ever apply?

 

[iwire]

yired29 has a point and it makes sense to me. With most lengths of conductors, when would the 2' rule ever apply?

Picture a 42 circuit panel mounted beside a 42 circuit lighting controller.

Now run a few 2" nipples between them.

If the nipples are less then 24" long you can forget about derating.

If the nipples are longer then 24" you have derate because 310.15(A)(2) will not apply because the conductors are very short on each side of the nipple.

On the other hand in Robs picture the bundled part is much shorter then the unbundled part.

The reason these rules work is due to copper and aluminums great thermal conductivity. The longer section of conductors in Robs picture serve as a heat sink to the conductors that are bundled.

 

[Pierre C Belarge]

Rob,

You are much more educated on the Code than I, but yired29 has a point and it makes sense to me. With most lengths of conductors, when would the 2' rule ever apply?

I am lost, what is the 2' rule?

 

[hardworkingstiff]

I am lost, what is the 2' rule?

310.15(B)(2) is what I was looking at.

I guess it's not a "rule", just if a nipple or bundling is more than 2', derating is required (until I read this thread, now I know more).

 

[Jim W in Tampa]

Are the lugs rated for 2 conductors ?
Why did you need run parallel conductors?
Job looks fantastic otherwise.

 

[infinity]

Are the lugs rated for 2 conductors ?
Why did you need run parallel conductors?
Job looks fantastic otherwise.

Yes, the lugs on that breaker was equipped with 3 separate holes for three conductors. I think that we used 3 sets because the CB was about 1000 amps.

 

[infinity]

Rob,

You are much more educated on the Code than I, but yired29 has a point and it makes sense to me. With most lengths of conductors, when would the 2' rule ever apply?

The exception allows the heat sink effect of a long conductor run to make an allowance for heat dissipation. If those conductors are bundled within the panel for say 5' I would need at least 45' of un-bundled conductors in the raceways to make the 5' only 10% of the total run length. Since those runs are all well over 100' in length I could have up to 10' of conductors bundled together in the panel and the exception would still apply.

BTW Bob summed this up rather nicely.

 

[Arby2]

This is the very reason 366.58(B) should not have been added to the Code. It gives the impression that CMP 8 doesn't know what an auxiliary gutter is. By its very definition an auxiliary gutter can't be used as a pullbox. An auxiliary gutter is used to supplement the wiring space at equipment. When it is not used to supplement space at equipment, it is a wireway. CMP 8 has further blurred the lines between gutters and wireways. In the photograph the gutter can be viewed as supplementing the wiring space at the tranformer. The notion that this installation could be considered a code violation illustrates perfectly the flaw in the logic of CMP 8 when this rule was added to Article 366.

 

[Arby2]

This is why 366.58(B) should have never been added to the Code. It gives the impression that CMP 8 doesn't know what an auxiliary gutter is. The addition of this text during the 2005 Code cycle further blurs the lines between gutters and wireways. By its very definition an auxiliary gutter is used to supplement the wiring space of other equipment. If used as a pullbox it would be a wireway and not a gutter. In the photograph the gutter should be viewed as supplementing the wiring space at the transformer, therefore 366.58(A) applies. According to Table 312.6(A) the gutter provides sufficient space for this purpose.

I disagree with requiring the derating of conductors bundled together in the gutter space of a panelboard, that is unless there are more than 30 current carrying conductors bundled together. If you interpret the code to require the derating of these conductors, wouldn't 300.3 prevent their installation in the panelboard anyway?