Conduit fill for communications cable

[Ansel]

I am trying to find the code in the NEC handbook for conduit fill for communications cable. I will be using Cat5e and/or 6 strand SMF optical cables. I have been using the 40% conduit fill from power cables requirement. Does anyone know the specific conduit fill for the communication cables and what code requirement am I suppose to use?

 

[Dennis Alwon]

I believe the Notes for Table 1 in Chapter 9 would be the pertinent section.

BTW, welcome to the forum

 

[Strathead]

What Dennis said. The actual codes are the percentage of fill, period. All the tables are merely a gift of the math done for you. Often they don't help for example when you need 3 #3/0 and a #6 ground in a conduit. So the 40% thing you are using is the code for three or more cables.

 

[luckylerado]

Assuming that your installation is only governed by NEC and no other standards apply, you should look to:

770.110(B)
800.110(B) and
830.110(B)

There is not a one size fits all answer without some additional info.
Most other standards will say to use Chapter 3 and Table 9 for fill and most LV cable manufactures give fill ratio tables based on Chapter 3 also.

 

[Ansel]

See 800.110(B) is saying that conduit fill Chapter 3 and Chapter 9 does not comply. I was told "I believe the Notes for Table 1 in Chapter 9 would be the pertinent section.
" from a previous post. Which do I follow? Since it doesn't have to follow Chapter 3 or Chapter 9, how do I know that percent fill I should use.

 

[hbiss]

See 800.110(B) is saying that conduit fill Chapter 3 and Chapter 9 does not comply. I was told "I believe the Notes for Table 1 in Chapter 9 would be the pertinent section.
" from a previous post. Which do I follow? Since it doesn't have to follow Chapter 3 or Chapter 9, how do I know that percent fill I should use.

The other posters were mistaken. 800.110(B) says it all. The NEC doesn't care about LV cable fill. Neither is it ever subject to inspection.

What should you do? You look to the cable manufacturers recommendations for the particular cable you will be using. All reputable cable manufactures will have fill tables that are based on a maximum allowable pulling tension so as not to damage the cable. This is completely different than the NEC which bases maximum fill on the dimension of the conductor(s).

It's quite possible that if you used a 40% fill based on the diameter of the cables you would have to apply too high of a pulling tension causing the cables to stretch. Of course other factors need to be considered also, like length of run, number of bends and what cable lube you use.

-Hal

 

[JFletcher]

Welcome to The Forum.

The other posters were mistaken. 800.110(B) says it all. The NEC doesn't care about LV cable fill. Neither is it ever subject to inspection.

What should you do? You look to the cable manufacturers recommendations for the particular cable you will be using. All reputable cable manufactures will have fill tables that are based on a maximum allowable pulling tension so as not to damage the cable. This is completely different than the NEC which bases maximum fill on the dimension of the conductor(s).

It's quite possible that if you used a 40% fill based on the diameter of the cables you would have to apply too high of a pulling tension causing the cables to stretch. Of course other factors need to be considered also, like length of run, number of bends and what cable lube you use.

-Hal

Completely correct... 800.110, last line of the paragraph says 'the raceway tables of chapter 3 in chapter 9 shall not apply". Using the manufacturer recommended fill, which may very well be 40%, is really only if you want their cable warranty. TDMM/ Bicsi/EIA/TIA standards only apply if the job spec requires you to follow them.

Not blowing 25 lb pulling Force is going to be more critical than conduit fill. The most important factor there is reducing number of quarter bends or 90 degree turns between pull points, second is copious amounts of wire lube.

Note that if you have to go through a fire rated wall, that conduit fill may be an issue with properly applying Firestop, or may require you to use a more expensive Firestop with conduit/ sleeves that are filled over 40% or 60%. We always use Hilti FS - 1 on such penetrations between the wire and conduit. I believe it allows a higher wire density or conduit fill than other fire stops

 

[luckylerado]

There are situations where the fill rules apply. The blanket statement that they do not is misleading. Read the sections.

 

[kwired]

:thumbsup:

The other posters were mistaken. 800.110(B) says it all. The NEC doesn't care about LV cable fill. Neither is it ever subject to inspection.

What should you do? You look to the cable manufacturers recommendations for the particular cable you will be using. All reputable cable manufactures will have fill tables that are based on a maximum allowable pulling tension so as not to damage the cable. This is completely different than the NEC which bases maximum fill on the dimension of the conductor(s).

It's quite possible that if you used a 40% fill based on the diameter of the cables you would have to apply too high of a pulling tension causing the cables to stretch. Of course other factors need to be considered also, like length of run, number of bends and what cable lube you use.

-Hal

Something like a 911 call center - lives may be at risk. Most other applications - something just doesn't work if it fails and not typically much threat to lives or property.

40% fill may be too much in some situations like when it comes to getting maximum performance out of a cable that got damaged from too much pulling tension being applied.Straight run you might be able to fill more then 40% and have little risks, put a few bends in it and now 40% causes too much pulling tension.

 

[JFletcher]

Anything that is mission critical like a 911 call center, the cable should be certified before the place is operational. And such places may very well go by the much more strict TDMM specs, which for starters only allows 100 ft and 2 bends between pull points.

 

[publicgood]

Beyond code considerations, future needs should be considered. Technology changes quickly.