Pulling cable through occupied Ductbank Conduit

CaptainKu

New member
Location
Kansas City
Is there a rule of thumb out there for pulling cable past cable in ductbank? I have a a bunch of 4" conduit on site that we have additional circuits that need to be pulled through them and I am trying to figure out if there is a fill % where it is to risky to pull past that could harm the cable. For example I have a 300' run of 4" conduit at 16% fill and need to pull a small 4 pair cable through it past existing cable and I am trying to figure out at what point is pulling past cable to risky and if it is even legal to do according to the NEC. I know it depends on a lot of factors such as the number of bends and type of cable but was curious if there is a general rule you use to go about this.

Thanks!
 

Fulthrotl

~Autocorrect is My Worst Enema.~
Is there a rule of thumb out there for pulling cable past cable in ductbank? I have a a bunch of 4" conduit on site that we have additional circuits that need to be pulled through them and I am trying to figure out if there is a fill % where it is to risky to pull past that could harm the cable. For example I have a 300' run of 4" conduit at 16% fill and need to pull a small 4 pair cable through it past existing cable and I am trying to figure out at what point is pulling past cable to risky and if it is even legal to do according to the NEC. I know it depends on a lot of factors such as the number of bends and type of cable but was curious if there is a general rule you use to go about this.

Thanks!

this is a swag deal.
some basic questions are needed to be asked here.

is this data cabling?

4 pair implies either data cable, or some mulitwire
control cable, such as you might find in a utility switchyard.

doesn't seem to be power cabling. power cable wouldn't likely
be 16% fill on a 4" pipe.

is there a pull string in the pipe with the existing cable?

first thing to see is if you can pull the string out, and pull a muletape
into the conduit in it's place. the other issue is if there is such a string,
is it spiraled thru the cables, as is very common.

if no string, or it's broken or rotted, which is common, you need to
make a parachute and see if you can fish a string thru the pipe along
with the existing cable. you can buy a parachute from greenlee, and
use it with a vacuum and compressor to blow in a string, then pull in
a muletape with the string.

i'd do this first, as it won't hurt the existing cables by pulling a string
that can cut thru pvc jackets. guaranteed if you destroy one cable, it'll
be the data backbone from the server to the world.

assuming data, i'd try to use that muletape to pull in two innerducts
into the pipe, then fish thru one of those, leaving the other for a spare,
again with a muletape in it. then you won't kill the existing cabling.

so, shoot some info back, and the internet will respond with answers.
some will be good, some will suck. but, they are free.
 

don_resqcapt19

Moderator
Staff member
Location
Illinois
Occupation
retired electrician
I would never use a small rope or string in a raceway of that length to pull in anything. There is too much risk of the rope or string cutting into the insulation on the existing conductors. A long time ago, I got in the habit of installing an extra conductor to be used for a future pull.
 
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