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#92728 - 04/05/05 06:27 AM How to figure conduit size
Bill39 Offline

Registered: 11/28/01
Posts: 77
Loc: Indianapolis, IN, USA
I need to figure the proper conduit size for a group of communication cables. These are 3 diffent size cables and I have the OD of each. There will be a mixture of each in several conduits.

Where in the NEC (or elsewhere)do I find this? In the old codebooks I thought there were examples but I'm having trouble finding it in the new one.

Thanks in advance for your replies.

2014 / 2011 NEC & Related Books and Study Guides
#92729 - 04/05/05 07:56 AM Re: How to figure conduit size
George Little Offline

Registered: 01/18/04
Posts: 1492
Loc: Michigan USA
I'm looking at Chapter 9 Notes to Table 1 note #5 and I would calculate the area of your cables and abide by the percentages in Table 1.

Another item: Note #9 might impact on your measurements.

[This message has been edited by George Little (edited 04-05-2005).]
George Little

#92730 - 04/05/05 09:03 AM Re: How to figure conduit size
Yoopersup Offline

Registered: 03/04/03
Posts: 826
Loc: Michigan
ODxODx.7854 = sq. inch of cables.

Example Cad 5 =.215OD
.215 X .215 X .7854 = .0363051

#12 THHN OD = .111
.111 X .111 X .7854 = 0096769

When you got a mixture of Cables and only know ID use this then go to conduit fill charts.


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