Conduits or ducts should be properly constructed having
smooth walls and of adequate size as determined by the overall cable diameter and
recommended percentage of fill of conduit area.
.
Dimensions
of conduit
|
Nominal size
conduit inches |
Internal diameter
inches |
Area
square inches |
.... 1
....1 1/4
.... 1 1/2
....2 |
1.049
1.380
1.610
2.067 |
0.86.......
1.50.......
2.04.......
3.36....... |
....2 1/2
....3
....3 1/2
....4 |
2.469
3.068
3.548
4.026 |
4.79.......
7.38.......
9.90.......
12.72....... |
....5
....6 |
5.047
6.065 |
20.00.......
28.89....... |
For groups or combinations of cables it is recommended that the conduit or tubing be of
such size that the sum of the cross-sectional areas of the individual cables will not be
more than the percentage of the interior cross-sectional area of the conduit or tubing as
shown in the following tables.
Maximum
percent internal
area of conduit or tubing
|
Number of cables |
| |
1 |
2 |
3 |
4 |
Over 4 |
Cables
(not lead-covered) |
53 |
31 |
40 |
40 |
40 |
Lead-covered
cables |
55 |
30 |
40 |
38 |
35 |
|
.... |
Maximum
percent internal
diameter of conduit or tubing
|
Number of cables
|
| |
1 |
2 |
3 |
4 |
Cables
(not lead-covered) |
72.8 |
39.3 |
36.5 |
31.6 |
Lead-covered
cables |
74.2 |
38.7 |
36.5 |
30.8 |
|
Maximum
allowable diameter
(in inches) of individual cables
in given size of conduit
|
Non-metallic
jacketed cable —
all cables of same outside diameter |
Nominal
size
conduit |
Number of cables
having same O.D. |
1 |
2* |
3* |
4* |
..1/2
..3/4
..1
..1 1/4 |
0.453
0.600
0.763
1.010 |
0.244
0.324
0.412
0.542 |
0.227
0.301
0.383
0.504 |
0.197
0.260
0.332
0.436 |
..1 1/2
..2
..2 1/2
..3 |
1.173
1.505
1.797
2.234 |
0.633
0.812
0.970
1.206 |
0.588
0.754
0.901
1.120 |
0.509
0.653
0.780
0.970 |
..3 1/2
..4
..5
..6 |
2.583
2.930
3.675
4.416 |
1.395
1.583
1.985
2.385 |
1.296
1.470
1.844
2.215 |
1.121
1.273
1.595
1.916 |
NOTE: To determine the size conduit required for any number (n) of equal
diameter cables in excess of four, multiply the diameter of one cable by .
This will give the “equivalent” diameter of four
such cables and the conduit size required for (n) cables may then be found by using the
column for four cables.
* These diameters are based on percent fill only. The Jam
Ratio, Conduit OD to Cable ID, should be checked to avoid possible jamming.
|
