TC-ER in Conduit Body

Status
Not open for further replies.

kenaslan

Senior Member
Location
Billings MT
I was wondering if there was a chart anywhere that shows conduit body fills using TC-ER. I can find plenty on XHHW. A typical 3/C #12 is 0.428" dia and an area of .14387 sq/in. A 3/4" Form 35 LB has a cable capacity of 7.50" cubed. Per table 314.16(B) a #6awg requires 5.00" cubed and has an area of 0.059. the 3C #12 is 2.548 of the #6. So I am assuming I would multiply the 2.548 by 5.00 for a required min volume of 12.19" cubed that come out to a 1" LB with a max wire fill of 12.50" , or am I all messed up?
 
You will have a problem with 336.24 if you try to put it a conduit body that small.

That being said, the wire fill rules don't apply to conductors 4 AWG and larger. The code does not really address wire fill for cables, but in my opinion the rules in 314.28 apply to this cable based on the OD.
 
From a previous thread I found this document which addresses this issue from both an NEC and UL compliance standpoint.

The document can be found here : http://www.carlonsales.com/techinfo/codesstandards/CS-LB_Conduit_Body_Wirefill.pdf

3/C #12 Dia 0.428"
Bending Radius NEC 336.24 (4x) 1.712"
3/4" LFMC fill per Ssouthwire 26.84%
3/4" Form 35 LB Wire Capacity per O-Z/Gedney is 7.5 cu in
Table 314.16(B) #6 awg Volume allowance is 5.00 cu in
#6 XHHW Area 0.059 sq in
3/C #12 Cable equivalent to 7.254 #6

Min volume required 36.27 cu in ?
 
From a previous thread I found this document which addresses this issue from both an NEC and UL compliance standpoint.

The document can be found here : http://www.carlonsales.com/techinfo/codesstandards/CS-LB_Conduit_Body_Wirefill.pdf

3/C #12 Dia 0.428"
Bending Radius NEC 336.24 (4x) 1.712"
3/4" LFMC fill per Ssouthwire 26.84%
3/4" Form 35 LB Wire Capacity per O-Z/Gedney is 7.5 cu in
Table 314.16(B) #6 awg Volume allowance is 5.00 cu in
#6 XHHW Area 0.059 sq in
3/C #12 Cable equivalent to 7.254 #6

Min volume required 36.27 cu in ?
That calculation is the one used in 314.28(A)(3) for smaller dimension conduit bodies. If is not based on the volume of the conduit body, but one the volume of the maximum number and size of conductors marked on the conduit body. Since this rule only applies to conductors 4 AWG and bigger, you won't find that type of marking on a 3/4" conduit body. The marking in the picture below is the marking you need to do the calculations in the document you posted.
1693521416512.png
 
I don't think you'll find a chart but since the bending radius is 5x if you oversize it to 6x you can find conduit body charts for larger size wires for various bending whether pull through or L or T. The closest large wire size that would L through that manufacturers chart could correspond approximately but again it would vary by manufacturer and design. The Mongol style will have more bending radius.
 
I was wondering if there was a chart anywhere that shows conduit body fills using TC-ER. I can find plenty on XHHW. A typical 3/C #12 is 0.428" dia and an area of .14387 sq/in.
My cheater method with several tray cables in a conduit is
sq/in. can be converted to circular mil's then if under 250 pick the closest wire size. (CH9 table 8)
Then I just use the tables for that wire.

.14387 sq/in. can be converted to 183181 circular mil's which lands right between a 3/0 and a 4/0
So to be a little conservative on fill treat it like a 4/0
 
Status
Not open for further replies.
Top