PVC 90Deg. 25foot radious

[Smart $]

...

i've yet to see an inspector count a schwoop as a 90.

Same here.

FWIW, the NEC says field bends shall be made with bending equipment identified for the purpose (e.g. 352.24). A "swoop", by my understanding of the slang terminology, is made without using any equipment, relying solely on the flexibility of the conduit itself.

However, I'm currently doubting a 25' radius in 6" PVC is a swoop.

 

[kwired]

If this run were 2" PVC I could see it being "swooped", but four "swooped" 90 deg bends in only 365 feet with 6 inch pipe is a little hard to believe, 6 inch is going to take some distance to deflect if you don't use bending equipment, heat it up or something.



I don't know how to do the pulling tension calculations, but if you are making a turn, no matter how gradual that turn may be you still have some extra drag between the conductor and the side wall of the pipe as compared to a straight run.


I also wondered if OP possibly meant 25" radius instead of 25', but that would be a pretty short radius for 6 inch pipe and would be less than allowed by Ch9 table 2.

 

[Szavala]

The reason of this issue is the existing service have (12) service feeder same size, and a couple weeks ago one of the feeder was shorted out all three phases with neutral inside of the 6" PVC, the existing conduit are encased in concrete and I see it impossible to install a pull box because on top of this encased duck bank run control conduit with wires and communication conduit, how I see the 25' swipes are made of (4) conduits with 22.5 swipes

 

[kwired]

The reason of this issue is the existing service have (12) service feeder same size, and a couple weeks ago one of the feeder was shorted out all three phases with neutral inside of the 6" PVC, the existing conduit are encased in concrete and I see it impossible to install a pull box because on top of this encased duck bank run control conduit with wires and communication conduit, how I see the 25' swipes are made of (4) conduits with 22.5 swipes

Might want to consider if too many bends has contributed to the conductor failure? I can't tell you it did, but something to look into.

 

[kingpb]

Without knowledge of the exact run and bends it would not be possible to do a pulling tension or sidewall pressure calculation.

Explain to owner you can attempt the pull, however there is no guarantee it will work. About the best you can do is to set-up the new cable pull with appropriate pullers, knowing the maximum allowable tension for the cable you are installing, keep an eye on the gauge and make sure you never exceed it. If you hit the maximum, stop the pull.

The problem you have is that all the parallel conductors must be the same length so to install a new run in another route is out of the question. Can you derate the service and use the conductors you have and make that the maximum and adjust protection devices?

Have you tried to pull the old conductors out? If you havn't my guess is they won't budge, and I'll bet the existing cables were damaged on install and the short was the result over time.

Just remember anything can be accomplished with the right amount of time and money.