Conduit Fill Exceptions

[Ravenvalor]

Is there still the exception in the conduit fill article where one can stuff to the gills a conduit as long as it is 24" or less in residential. Can someone please point me to the article?

Thank you,

 

[infinity]

Stuffed to the gills no but if a nipple is 24" or less then the fill ratio goes up to 60% from the typical 40%. Also there is no derating required {310.15(B)(3)(a)}. Also look at Chapter 9, Notes to Tables #4.

 

[Dennis Alwon]

Also if the raceway is a sleeve and 24 inches or less then you can fill it up.

 

[petersonra]

Stuffed to the gills no but if a nipple is 24" or less then the fill ratio goes up to 60% from the typical 40%. Also there is no derating required {310.15(B)(3)(a)}. Also look at Chapter 9, Notes to Tables #4.

60% is pretty close to being stuffed to the gills though.

 

[infinity]

Also if the raceway is a sleeve and 24 inches or less then you can fill it up.

So you mean that if you use a section of raceway as a sleeve but not a raceway? You still cannot exceed 60% fill if it's a raceway.

 

[Dennis Alwon]

So you mean that if you use a section of raceway as a sleeve but not a raceway? You still cannot exceed 60% fill if it's a raceway.

No I was saying you can exceed 60%--- as much as you can fit in it.

 

[electrofelon]

60% is pretty close to being stuffed to the gills though.

https://en.wikipedia.org/wiki/Circle_packing_in_a_circle

 

[electrofelon]

......and if anyone wants more, a lot more, see: http://hydra.nat.uni-magdeburg.de/packing/cci/cci.html. One can get the density arbitrarily close to ~.9069 as the number of circles approaches infinity.

 

[infinity]

No I was saying you can exceed 60%--- as much as you can fit in it.

What about the section I posted in post #2?

Notes to Tables:

(4) Where conduit or tubing nipples having a maximum
length not to exceed 600 mm (24 in.) are installed
between boxes, cabinets, and similar enclosures, the
nipples shall be permitted to be filled to 60 percent of
their total cross-sectional area, and 310.15(B)(3)(a)
adjustment factors need not apply to this condition.

 

[Dennis Alwon]

That Note says between boxes and enclosures--- a sleeve is not between boxes

 

[LarryFine]

One can get the density arbitrarily close to ~.9069 as the number of circles approaches infinity.

A sort of "circular resolution."

 

[infinity]

That Note says between boxes and enclosures--- a sleeve is not between boxes

Agreed, that's why I asked for clarification as to whether or not you were referring to a raceway used as a sleeve or an actual raceway.

 

[Carultch]

No I was saying you can exceed 60%--- as much as you can fit in it.

Unless your wires have cross sections shaped like pie wedges instead of circles, you probably won't be able to pack it much further beyond 60% in practice. The 60% rule is probably based on 3-wires packed in a triangular arrangement, which can pack up to 64% fill by area, with the 4% margin of error. Plus, you've got irregularities from the fact that the wire has factory curvature and isn't a straight rod, and it will be hard to maintain a bundle of wires packed in a theoretically optimal packing of the circles.

Obviously, for 2 identical conductors, you can't possibly even fill it to 60%. Packed wall-to-wall, they fill at 50%, which is why 2-conductors uniquely have the 31% fill rule for raceways in general.

 

[Ravenvalor]

Agreed, that's why I asked for clarification as to whether or not you were referring to a raceway used as a sleeve or an actual raceway.

Thanks for all of the great input. I did not find the definition of sleeve in the NEC. Would it perhaps be something made out of any common type of material (wood) but it is not a raceway? If so, only cables can be installed in it and not individual conductors?

Thanks again for the great help.

 

[infinity]

Thanks for all of the great input. I did not find the definition of sleeve in the NEC. Would it perhaps be something made out of any common type of material (wood) but it is not a raceway? If so, only cables can be installed in it and not individual conductors?

Thanks again for the great help.

A sleeve can be constructed from just about anything. It's common to use a short section of raceway to make them but you could make one out of plumbers pipe if you wanted.

Yes if you have individual condcutors then they must be in a raceway unless they are permitted to be run in free air..