Inner duct fill

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DUCKMAN

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Does the code consider inner duct in any way when calculating conduit fill? I could not find any reference to it. I would think the addition of multiple inner-ducts to a conduit would reduce the amount of permissable fill, but I can't prove it. Any help would be appreciated.
 
Are you talking about filling innerduct or filling a conduit with innerduct?
 
mkoloj said:
Are you talking about filling innerduct or filling a conduit with innerduct?
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Filling the innerduct itself. For example, if I put four innerducts in a 4" EMT, is the amount of fill reduced from what Annex C or Chapter 9 tells me? Logic says yes, but I cannot find any reference to it.
 
infinity said:
You're talking about inner duct for fiber optic cables?
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I have never had a fill issue with fiber, I was thinking more on the lines of communication or PL circuits.
 
DUCKMAN said:
Filling the innerduct itself. For example, if I put four innerducts in a 4" EMT, is the amount of fill reduced from what Annex C or Chapter 9 tells me? Logic says yes, but I cannot find any reference to it.
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Fill would be based on the individual innerducts.

If you are within fill limits for the innerducts, you will automatically be ok for the 4"emt.
 
DUCKMAN said:
I have never had a fill issue with fiber, I was thinking more on the lines of communication or PL circuits.
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Are there fill limitation requirements for those types of cables?
 
:)
barbeer said:
Only physical impossibility!:D

Is the conduit run complete or just a sleeve?
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Don't most manufacturers have a maximum allowable pulling force? Aren't they supposed to be installed according to manufacturers instructions?

Wouldn't pulling force be the determining factor in what the fill could be?
 
barbeer said:
Only physical impossibility!:D

Is the conduit run complete or just a sleeve?
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It is a complete conduit system. The 4" emt runs between 2 data rooms. We pull PL circuits through some of the inner-duct, within the 4"
 
infinity said:
Are there fill limitation requirements for those types of cables?
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Article 725.3(A) requires compliance with 300.17
Article 800.110 Exception states that conduit fill does not apply

So it would be needed for PL circuits, but not communications circuits. OR at least that is what I think.
 
barbeer said:
Only physical impossibility!:D

Is the conduit run complete or just a sleeve?
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When I teach conduit or box fill, The question is "How many conductors can you put in a "whatever" , and the inevitable answer is "one more!".
 
DUCKMAN said:
Does the code consider inner duct in any way when calculating conduit fill? I could not find any reference to it. I would think the addition of multiple inner-ducts to a conduit would reduce the amount of permissable fill, but I can't prove it. Any help would be appreciated.
Click to expand...


I hate to bump my own thread, but I still do not have a clear answer to this question.
 
DUCKMAN said:
I hate to bump my own thread, but I still do not have a clear answer to this question.
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You won't find innerduct in the NEC.

3-4 1 &1/4 innerducts fit into a 4". 864 FOC is the largest that will fit into a 1 & 1/4 innerduct.
 
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