Article 376.22 Metallic Wireway Fill

Status
Not open for further replies.
Are there ANY provisions for metallic wireway fill being above 20%. An electrical contractor is telling me that you can go as high as 70% if there are no current carrying conductors. I cannot find this in the code. I find derating charts IF there are current carrying conductors, but nothing that changes the 20% fill rule.
 
If your conductors don't carry current, why bother installing them? More info on the install is in order here.

376.22 states..."Conductors for signaling circuits or controller conductors between a motor and its starter and used only for starting duty shall not be considered as current-carrying conductors"

I guess maybe that's why you would install them.
 

mweaver

Senior Member
Sparkycontrols,

In answer to your question: “Are there ANY provisions for metallic wireway fill being above 20%.” …The answer is no (at least not that I am aware of…).


As I understand wireway fill…

Metallic wireway fill is governed under Section 376.22(A) and is actually directed at areas of conductor concentration inside the wireway. This area of conductor concentration considers ALL conductors within the wireway. This includes current-carrying, non current-carrying, control wiring and spares. The language for exactly which conductors the fill requirement is directed at is all encompassing (…It is considering all of them…).


You are correct in your statement: “I find derating charts IF there are current carrying conductors, but nothing that changes the 20% fill rule.”


The requirements for wireway conductor adjustment factors in Section 376.22(B) have no bearing on the fill requirements of Section 376.22(A). In that I mean non current-carrying conductors as well as spares are a consideration in wireway fill.

The fill requirements for wireway differ from other raceways in that conductors can enter and exit the wireway anywhere along its length. For this reason, the fill for wireway is directed at areas of conductor concentration. All areas of conductor concentration are limited to 20% of the wireway cross sectional area at any particular point along the length of the wireway.

A 4 inch by 4inch wireway has a cross sectional area 16 square inches (wireway length has no bearing on the cross sectional area…). At any given location along the wireway length the cross sectional area of ALL conductors within the wireway cannot exceed 20% or 3.2 square inches for a 4inch by 4inch wireway.

As Mr. Belarge noted, Section 376.56(A) permits the areas of concentration for conductor splices and taps to be as much as 75% of the cross sectional area of the wireway, not the conductors themselves, which are governed under 376.22(A)… … Staggering splices and taps can impact (and potentially reduce) an individual area of splice concentration within the wireway.

Your EC may have been thinking of Section 376.56(A) when he noted a 70% fill, but the requirements of Section 376.56(A) do not alleviate the requirements of Section 376.22(A) for the 20% fill.

I do hope this is helpful…

mweaver
 
Last edited:

chris kennedy

Senior Member
Location
Miami Fla.
Occupation
60 yr old tool twisting electrician
376.22 states..."Conductors for signaling circuits or controller conductors between a motor and its starter and used only for starting duty shall not be considered as current-carrying conductors"

I guess maybe that's why you would install them.

Very good, thank you. You have that many of this type conductor in one wireway?
 

chris kennedy

Senior Member
Location
Miami Fla.
Occupation
60 yr old tool twisting electrician
376.22 states..."Conductors for signaling circuits or controller conductors between a motor and its starter and used only for starting duty shall not be considered as current-carrying conductors"

I smell a conflict.

ARTICLE 725 Class 1, Class 2, and Class 3 Remote-Control, Signaling, and Power-Limited Circuits
725.3 Other Articles.
Circuits and equipment shall comply with the articles or sections listed in 725.3(A) through (G). Only those sections of Article 300 referenced in this article shall apply to Class 1, Class 2, and Class 3 circuits.

(A) Number and Size of Conductors in Raceway. Section 300.17.
Raceway. An enclosed channel of metal or nonmetallic materials designed expressly for holding wires, cables, or busbars, with additional functions as permitted in this Code. Raceways include, but are not limited to, rigid metal conduit, rigid nonmetallic conduit, intermediate metal conduit, liquidtight flexible conduit, flexible metallic tubing, flexible metal conduit, electrical nonmetallic tubing, electrical metallic tubing, underfloor raceways, cellular concrete floor raceways, cellular metal floor raceways, surface raceways, wireways, and busways.
 
Status
Not open for further replies.
Top