Michael Hayes
Member
any one know how many 1" innerducts will fit in a 3" sch-40 pvc conduit? I assume 3?
1" innerduct
- Thread starter Michael Hayes
- Start date
- Status
RichB
Senior Member
- Location
- Tacoma, Wa
- Occupation
- Electrician/Electrical Inspector
never ran 3" before but we do ALOT of 4" and we get 4 in that so I would assume you are correct with 3
masterinbama
Senior Member
- Location
- Huntsville Alabama
I figure it like individual conductors in conduit.
1" innerduct (smooth wall) O.D. = 1.33 x 3 = 3.99
3" conduit area 40% fill is 3.54"
3" conduit area 53% fill is 4.67
In my opinion it's possible but it will be tricky. BTW there is not much difference for corrugated wall duct.
1" innerduct (smooth wall) O.D. = 1.33 x 3 = 3.99
3" conduit area 40% fill is 3.54"
3" conduit area 53% fill is 4.67
In my opinion it's possible but it will be tricky. BTW there is not much difference for corrugated wall duct.
The big question is, how long is the run. A short section (sleeve through the wall)you can get three in but on a long run it won't make it. A 1" corrigated duct has an O.D of 1.35 ". Thats 1.43 sq" x 3 for a total of 4.29 sq". 3" pvc at 40%= 2.907 sq". If you have a circle compas and draw it out, you'll see how close it is to maximum fill.
There are some calculators on some web sites that only allow (1) 1" duct in a three inch raceway.
4" pvc has a 5.022 sq" fill. Keep in mind you have to get the swivel and pulling head through the conduit also.
Rick
Last edited:
Twoskinsoneman
Senior Member
- Location
- West Virginia, USA NEC: 2020
- Occupation
- Facility Senior Electrician
Okay dumb question, what is the purpose of inner ducting?
Do you have to derate based on all the wires of the three inner ducts as if in one duct?
Do you have to derate based on all the wires of the three inner ducts as if in one duct?
- Location
- Massachusetts
The few times I have put multiple inner ducts in EMT it was for data contractors to pull fiber optic cables in at a later date.
We would run four inner ducts in 4" EMT. I guess this makes it so a single cable can be added or changed without risk of damage to the others. I really don't know.
We did the same thing. Had a 3 or 4 inch conduit to every room in the building with a bunch of fiber in it. This fiber was a little large (100u) because it was installed before things standardized on 64.5u fiber. We wanted some single mode fiber and some 62u fiber. But it was impossible to pull new ones through or pull just some of them out.
So everything was pulled out and 3 innerducts were installed. One has "secure" fibers, one has "nonsecure" fibers, and the 3rd was empty for future capabilities. Because of the huge amount of time required to terminate and polish each fiber, management never wanted to have to pay for that again. Should we have to replace the secure or non secure fibers, you can remove everything from one innerduct without messing up the others.
So everything was pulled out and 3 innerducts were installed. One has "secure" fibers, one has "nonsecure" fibers, and the 3rd was empty for future capabilities. Because of the huge amount of time required to terminate and polish each fiber, management never wanted to have to pay for that again. Should we have to replace the secure or non secure fibers, you can remove everything from one innerduct without messing up the others.
- Status