300.19

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300.19 Supporting Conductors in Vertical Raceways.

(A) Spacing Intervals — Maximum. Conductors in vertical raceways shall be supported if the vertical rise exceeds the values in Table 300.19(A). One cable support shall be provided at the top of the vertical raceway or as close to the top as practical. Intermediate supports shall be provided as necessary to limit supported conductor lengths to not greater than those values specified in Table 300.19(A). See related UL

Conductors in long vertical runs must be supported if the vertical rise exceeds the values in Table 300.19(A). This requirement prevents the weight of the conductors from damaging the insulation where they leave the conduit and prevents the conductors from being pulled out of the terminals. Support bushings or cleats such as those shown in Exhibits 300.16 and 300.17 may be used, in addition to many other types of grips manufactured for this purpose.

Application Example

A vertical raceway contains 1/0 AWG copper conductors. Using Table 300.19(A), if the vertical run is not greater than 100 ft, 300.19(A) requires one cable support near the top of the run. For longer vertical runs, 300.19(A) requires intermediate supports to limit the supported length to the table values. If the vertical run is less than 100 ft, cable supports are not required.

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Exhibit 300.16 A support bushing, located at the top of a vertical conduit at a cabinet or pull box, used to prevent the weight of the conductors from damaging insulation or placing strain on termination points.

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Exhibit 300.17 Support cleats used to prevent the weight of vertical conductors from damaging insulation or placing strain on termination points.


Exception: Steel wire armor cable shall be supported at the top of the riser with a cable support that clamps the steel wire armor. A safety device shall be permitted at the lower end of the riser to hold the cable in the event there is slippage of the cable in the wire-armored cable support. Additional wedge-type supports shall be permitted to relieve the strain on the equipment terminals caused by expansion of the cable under load.

Table 300.19(A) Spacings for Conductor Supports

This table is available as a PDF. Click here to view.



Changed From 2008

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Table 300.19(A): Column heading revised for consistency with the terminology used in the section.


(B) Fire-Rated Cables and Conductors. Support methods and spacing intervals for fire-rated cables and conductors shall comply with any restrictions provided in the listing of the electrical circuit protective system used and in no case shall exceed the values in Table 300.19(A). See related UL

Electrical circuit protective systems using fire-rated cable assemblies, generally require more frequent and robust support systems. For example, one manufacturer of Type MI fire-rated cable requires that vertical runs of a two-hour fire-rated assembly be supported every 4 ft, varying substantially from the support requirements of Table 300.19(A).


(C) Support Methods. One of the following methods of support shall be used:

(1)
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By clamping devices constructed of or employing insulating wedges inserted in the ends of the raceways. Where clamping of insulation does not adequately support the cable, the conductor also shall be clamped. See related UL

(2)
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By inserting boxes at the required intervals in which insulating supports are installed and secured in a satisfactory manner to withstand the weight of the conductors attached thereto, the boxes being provided with covers. See related UL

(3)
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In junction boxes, by deflecting the cables not less than 90 degrees and carrying them horizontally to a distance not less than twice the diameter of the cable, the cables being carried on two or more insulating supports and additionally secured thereto by tie wires if desired. Where this method is used, cables shall be supported at intervals not greater than 20 percent of those mentioned in the preceding tabulation. See related UL

(4)
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By a method of equal effectiveness.


Ok, I continue to study through the NEC knowing that I am still a novice. I am particularly interested in section A. This part in particular, "One cable support shall be provided at the top of the vertical raceway or as close to the top as practical." The included notes state this, "
Application Example

A vertical raceway contains 1/0 AWG copper conductors. Using Table 300.19(A), if the vertical run is not greater than 100 ft, 300.19(A) requires one cable support near the top of the run. Are there any exceptions to this or does this mean that ALL panels, pull boxes, etc etc must have the aforementioned supports? Just want to make sure that I am considering everything correctly before I go and start making trouble :angel:


 

infinity

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So what you're saying is that any verticle run requires support at the top based on the example you've provided?

Application Example

A vertical raceway contains 1/0 AWG copper conductors. Using Table 300.19(A), if the vertical run is not greater than 100 ft, 300.19(A) requires one cable support near the top of the run. For longer vertical runs, 300.19(A) requires intermediate supports to limit the supported length to the table values. If the vertical run is less than 100 ft, cable supports are not required.
 
So what you're saying is that any verticle run requires support at the top based on the example you've provided?

:blink: errrr ummmm hmmmmm

No not me!!!! That is directly from the NEC and that is what it says. I am just digging for knowledge from those who have traversed the deep dark recesses of electricity!!:cool:

I am just wanting to make sure that there are no exceptions to where this rule will apply. To me(take that for what it's worth) it seems to mean that anytime the conductors come into an enclosure via vertical raceway it would require a support bushing at the entry point, or near to, of that enclosure. and any length over 100' would require added support for the conductors.
 

Strathead

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Location
Ocala, Florida, USA
Occupation
Electrician/Estimator/Project Manager/Superintendent
300.19 Supporting Conductors in Vertical Raceways.

(A) Spacing Intervals ? Maximum. Conductors in vertical raceways shall be supported if the vertical rise exceeds the values in Table 300.19(A). A vertical raceway contains 1/0 AWG copper conductors. Using Table 300.19(A), if the vertical run is not greater than 100 ft, 300.19(A) requires one cable support near the top of the run. Are there any exceptions to this or does this mean that ALL panels, pull boxes, etc etc must have the aforementioned supports? Just want to make sure that I am considering everything correctly before I go and start making trouble :angel:



I am not sure if I am reading your question correctly. If so, then no, as it clearly states you only need support wor 1/0 copper if the run exceeds 100 feet. If the run is 105 feet then you need 2 supports, if the run is 99 feet then you legally don't need a support, but may opt to put one in anyway. Does that answer your question?
 
I am not sure if I am reading your question correctly. If so, then no, as it clearly states you only need support wor 1/0 copper if the run exceeds 100 feet. If the run is 105 feet then you need 2 supports, if the run is 99 feet then you legally don't need a support, but may opt to put one in anyway. Does that answer your question?

Not quite, the 1/0 is just an example. The code is contained in the very first post I made. The first time I read it I caught on to this statement, "Conductors in vertical raceways shall be supported if the vertical rise exceeds the values in Table 300.19(A)". So I took that to mean that the work we were doing was up to code because 99.9% of our work the vertical part is on a couple of feet at most, but then in the added notes of the NEC plus I read this,"Using Table 300.19(A), if the vertical run is not greater than 100 ft, 300.19(A) requires one cable support near the top of the run.". Then all of a sudden "if the vertical run is not greater than 100ft, 300.19 requires one cable support near the top of the run???


Just looking for clarification. Do you always need one support, or must it first exceed the 100ft?????
 

don_resqcapt19

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Illinois
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retired electrician
I don't see anything in the code language that says you need any vertical supports when the vertical run is less than the lengths shown in the table. The NEC plus is not an official interpretation of code rules.
 
The reason my interest got sparked was, in reading Practical Electrical Wiring by Herbert Richter and Frederick Hartwell, I came across a portion in the book which makes reference to this code and its application. I just reread the section and think that I have a bit clearer grasp of the full scope of the code.

Thanks everyone for your prompt replies. They are greatly appreciated.
 

Strathead

Senior Member
Location
Ocala, Florida, USA
Occupation
Electrician/Estimator/Project Manager/Superintendent
Not quite, the 1/0 is just an example. The code is contained in the very first post I made. The first time I read it I caught on to this statement, "Conductors in vertical raceways shall be supported if the vertical rise exceeds the values in Table 300.19(A)". So I took that to mean that the work we were doing was up to code because 99.9% of our work the vertical part is on a couple of feet at most, but then in the added notes of the NEC plus I read this,"Using Table 300.19(A), if the vertical run is not greater than 100 ft, 300.19(A) requires one cable support near the top of the run.". Then all of a sudden "if the vertical run is not greater than 100ft, 300.19 requires one cable support near the top of the run???


Just looking for clarification. Do you always need one support, or must it first exceed the 100ft?????

I can't disagree that this is poorly written. Since you will basically go from needing no supports for anything less than 100 feet to at least 2 supports for anything over 100 feet, but that is what it says. You, or perhaps Dennis may want to move this over to the proposal section of the code, because every time I read it my head spins a little more. For example, if your run is 105 feet, then 2 supports would be required. Wouldn't it be practical for one to be at 55 feet and the other to be at 105? Also, since the supports that I am familiar with eliminate virtually all vertical force on the cable above the point you install them, shouldn't they be installed to prevent a vertical length any longer than xxx which it is clearly not written to prevent.
 
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