Conduit Bodies calculation

[gmayeux]

What is the NEC method for sizing conduit bodies (LB's,T's in particular) to meet bending radius and allowable fill, is there two seperate calculations,i believe 314.28 A(2) deals with the bending, but not sure how to determine conductor fill. thanks,

 

[jumper]

314.16(C) Conduit Bodies.
(1) General. Conduit bodies enclosing 6 AWG conductors
or smaller, other than short-radius conduit bodies as described
in 314.5, shall have a cross-sectional area not less
than twice the cross-sectional area of the largest conduit or
tubing to which they can be attached. The maximum number
of conductors permitted shall be the maximum number
permitted by Table 1 of Chapter 9 for the conduit or tubing
to which it is attached.


Large conduit bodies are usually stamped with max.

 

[gmayeux]

i did forget to mention, i was looking for calculations for #6 AWG and larger,and while i do realize the stamping on the body, in the design phase, and or to check if the conduit body size is going to be the same as the conduit size listed on a drawing.

 

[jumper]

What brand name?

I found this for Crouse-Hinds.

http://www.stateelectric.com/formcalc/wirefill.asp

 

[kwired]

A conduit body with a max conductor size has likely taken into account the bending radius when determining this size. If it is same size as the conduit it connected to it will not have a problem with cross sectional area.

If the conduit body contains splices or taps then we have to consider the volume of the body for conductors smaller than 4 AWG. If you have splices or taps in conductors 4 AWG or larger - it would have to be 6 or 8 times the diameter of raceway in length just like a pull or junction box. You don't want a conduit body even if allowed in most cases if splicing those larger conductors.

 

[don_resqcapt19]

There are no calculations for that when using conductors larger than #4 in conduit body. The maximum number and size of the conductors is marked on the conduit body and if you want to use a different combination of conductors, you are stuck with finding a conduit body that meets the size rules found in 314.28(A)(1) or (2).