Metal Wireways "straight pulls"

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Strathead

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How do the experts here interpret 376.23(B)? Specifically straight pulls shall comply with 314.28(A)(1). Surely they aren't saying that a wireway has to be 8 times the conduit size if the wires come in on side to the far left and out the other side on the far right, but how do we get there. I suspect it has to do with 372.28(A), but how do we apply it? At what point would the pull become a deflected pull and how do you validate this in the code? Am I even asking this clearly? I have some suppositions, but I don'w want to poison the question before I see some answers.

Also, what does, "where the direction of the metal wireway is deflected greater than 30 degrees mean in 372.23(A)
 
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Straight pulls are exactly as you stated. If you have a 2" conduit going in and out the opposite sides then it is 8 x 2 = 16" minimum length of the trough. The width only needs to be wide enough for the conduit.

The code is looking at the maximum size wires that may be pulled in the conduit and having a safe install (no damage to the wire)
 
And I always order them wide so my big fat paws can reach in. Stuff like that I go for the men over saving $2.
 
Dennis Alwon said:
Straight pulls are exactly as you stated. If you have a 2" conduit going in and out the opposite sides then it is 8 x 2 = 16" minimum length of the trough. The width only needs to be wide enough for the conduit.

The code is looking at the maximum size wires that may be pulled in the conduit and having a safe install (no damage to the wire)
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I suspect that the code is requiring that spacing to allow bending room to pull the wire/cable in from one side then re-pull it out the other side, rather than pulling straight through without using the trough as a pull point.
If the incoming and outgoing conduits are not directly in line with each other, then the 8x may be needed even for a straight through pull.
 
Dennis Alwon said:
Straight pulls are exactly as you stated. If you have a 2" conduit going in and out the opposite sides then it is 8 x 2 = 16" minimum length of the trough. The width only needs to be wide enough for the conduit.

The code is looking at the maximum size wires that may be pulled in the conduit and having a safe install (no damage to the wire)
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Width of trough is what I am looking for. Here is a crude representation of what I am describing. Dimension A can't be 8 times the conduit diameter.
View attachment New Document.pdf
 
Strathead said:
Width of trough is what I am looking for. Here is a crude representation of what I am describing. Dimension A can't be 8 times the conduit diameter.
View attachment 21435
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The 8x dimension would be A in your diagram. From the entry wall to the exit wall.
If A cannot practically be 8x the conduit diameter, then IMHO you cannot use that trough configuration.
There is no limit on the horizontal dimension or the horizontal offset, although if they are not lined up vertically, I would say that you have a deflection to worry about.
 
GoldDigger said:
The 8x dimension would be A in your diagram. From the entry wall to the exit wall.
If A cannot practically be 8x the conduit diameter, then IMHO you cannot use that trough configuration.
There is no limit on the horizontal dimension or the horizontal offset, although if they are not lined up vertically, I would say that you have a deflection to worry about.
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Note that you start with the nominal "trade size" of the conduit, not any particular ID or OD dimension.
 
GoldDigger said:
The 8x dimension would be A in your diagram. From the entry wall to the exit wall.
If A cannot practically be 8x the conduit diameter, then IMHO you cannot use that trough configuration.
There is no limit on the horizontal dimension or the horizontal offset, although if they are not lined up vertically, I would say that you have a deflection to worry about.
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Unless I misunderstand you that is not a practical answer. The installation I drew is not uncommon. I makes sense that you can't make a straight pull, but when you deflect the conductors the only thing that makes sense is the width has to be per 314.28. I can have 6 feet between the incoming and outgoing conduits and dimension A has zero to do with the relationship between the incoming and the outgoing.
 
I thought there would be more input from the brains here. The application I am describing is quite typical. Overhead service comes in to the top of a wireway and then is tapped to multiple conduits for meter out of the bottom. If it was an underground service, then one would use deflection for the width and 6 times the diameter for the horizontal distance. It a case like this common sense says it wouldn't matter whether the wires left from the same side or the opposite side the stress on the wire would be similar.
 
I think that (A) may apply.

376-23a0-02web.gif
 
jumper said:
I think that (A) may apply.

376-23a0-02web.gif
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I definitely believe that is basically how it is, but how do we get there? That reference is 2011 and I am not sure the wording hasn't changed since, but if those wires leave the box without splicing you couldn't use 376.23(A) you would have to use 376.23(B).. By the way, I do see where you are right in the examples I gave, as it isn't being used as a pull box, but as a splice box instead. If (B) has to apply to a pull box, then this is another example of a VERY bad code in my opinion. The other example I refer to is the requirement that the entering and exiting conduits in a pull box have to be 6 times the diameter apart. If I enter the box in the lower left corner then I loop the conductors all the way around the box and pull them out of a conduit in the same corner that is probably the best pull available in regards to damaging the conductors, but it is not allowed per 314.
 
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I am answering this because I want to keep it alive. Someone has to have some input on how we can use a gutter as described within the current codes.
 
tkb said:
I don’t see how that would be compliant with the 8x rule.
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And yet it is an installation that is done all the time. When you look at the Mike Holt picture that was provided, it makes no sense not to allow the installation turned up one way and down the other with separation than it does to allow them both turned the same way. I don't disagree with you that it appears that way in the code. If so, I can't grasp why is hasn't created a proposed change, unless it is a nuance that has been missed for at least two code cycles.
 
Strathead said:
I thought there would be more input from the brains here. The application I am describing is quite typical. Overhead service comes in to the top of a wireway and then is tapped to multiple conduits for meter out of the bottom. If it was an underground service, then one would use deflection for the width and 6 times the diameter for the horizontal distance. It a case like this common sense says it wouldn't matter whether the wires left from the same side or the opposite side the stress on the wire would be similar.
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It is my opinion, that the 8X applies and yes, I know that there are thousands of installations where that rule has not been complied with. I tried to put a rule in that the 8x would apply only where the conductors extend at least 15' beyond the wireway in both conduits, but that was rejected.
Public Input No. 2798-NFPA 70-2014 [ Section No. 376.23(B) ] Original Hide Markup

(B) Metallic Wireways Used as Pull Boxes.

Where insulated conductors 4 AWG or larger are pulled through a extend 4.5m (15 ft) or more in both directions from the wireway, the distance between raceway and cable entries enclosing the same conductor shall not be less than that required by 314.28(A) (1) for straight pulls and 314.28(A) (2) for angle pulls. When transposing cable size into raceway size, the minimum metric designator (trade size) raceway required for the number and size of conductors in the cable shall be used.






Statement of Problem and Substantiation for Public Input

It is common practice to install wireways at equipment where the distances between conductor entry/exit points do not comply with the rules found in 314.28(A) (1) or (2). The current code rule does not permit this application. Most inspection authorities permit the installation of wireways containing conductors sized #4 and larger without requiring compliance with the rules in 314.28, where the wireway has been installed adjacent to equipment such as switchboards, panelboards or transformers. The rules in 314.28 are designed to minimize damage to the conductors as they are being installed. The risk of conductor damage where the conductors are installed without compliance with 314.28 is small where the conductor does not extend a long distance from the wireway.
Submitter Information Verification
Submitter Full Name: DON GANIERE
Organization:
[ Not Specified ]
Submittal Date: Wed Oct 29 15:00:56 EDT 2014
Committee Statement

Resolution:
No substantiation was submitted to show that damage to conductors is unlikely for raceway and cable entry spacings not meeting the requirements of 376.23(B)(1) & (2).
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blue = new text, red = deleted text
 
don_resqcapt19 said:
It is my opinion, that the 8X applies and yes, I know that there are thousands of installations where that rule has not been complied with. I tried to put a rule in that the 8x would apply only where the conductors extend at least 15' beyond the wireway in both conduits, but that was rejected.


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I have never gotten involved in code change suggestions. For this bad rule though, here is what I think is valid in thought but not exact words. Where conductors enter one side and exit the opposite side of a wireway and the deflection is less than 6 times the conduit diameter, the installation shall comply with 314.28(A) (1). Otherwise they shall comply with table 312.6(A) one wire per terminal.

I guess another way would be to make the 6 times rule an exception
exception where conductors enter one side and exit the opposite side of a wireway and the deflection is a minimum of 6 times the conduit diameter per 314.28 (A) (2) the width shall comply with table 312.6(A) one wire per terminal.

Justification for this is that, if I come in the end I can go out either side 6 times the diameter. If I come on one side I can exit the same side 6 times the diameter. So I come in one side, deflect 6 times the diameter I should be able to exit the other side that far with the same stress on the conductor.
 
314.28(A)(1) does not define the notion of "straight pulls". When the entry and exit are on parallel walls, but they are offset by more than the distance between those walls, I find it reasonable to exclude that from the category of "straight pull". It is more angled than straight. In which case only the 6x rule would apply, not the 8x rule.

Cheers, Wayne
 
wwhitney said:
314.28(A)(1) does not define the notion of "straight pulls". When the entry and exit are on parallel walls, but they are offset by more than the distance between those walls, I find it reasonable to exclude that from the category of "straight pull". It is more angled than straight. In which case only the 6x rule would apply, not the 8x rule.

Cheers, Wayne
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I find it reasonable, but I don't find it a position that can be in any way justified with code references. I had hoped that there might be some obscure code or interpretation that I was missing, but Don's post pretty much clarifies it for me. I guess one approach is to install wireways with reason, and if you run across an inspection department that nails you, just cut the wire and put a butt splice in. Then is will be two conductors. That, of course, just reinforces the weakness of this code.
 
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