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Electrical Code for Wire In Conduit

electrical-wires-in-couduits Summary: National Electrical Code Appendix C Table C1 - Shows how the Maximum Number of Wires in Conduits including EMT, Electrical metallic Tubing. This information is based upon NEC Table 1, Chapter 9.

Safe Practices for Installing Electrical Wire into Conduit


Maximum Number of Wire Conductors

It is very important to understand the limitations when installing wire into conduit.

Facts About Wires in Conduit:

Wire insulation is rated upon the amount of heat it can safely withstand.

Electricity passing through wires will generate heat.

Wire fill inside conduit must never exceed the specified amount to prevent overheating of the wires inside the conduit.





Maximum Number of Conductors in
EMT - Electrical Metallic Tubing

Type

Conductor

EMT Conduit Trade Size (in.)

THHN,
THWN,
THWN-2

Size
(AWG /
kcmil)

½

¾

1

2

3

4

14
12
10
8
12
9
5
3
22
16
10
6
35
26
16
9
61
45
28
16
84
61
38
22
138
101
63
36
241
176
111
64
364
266
167
96
476
347
219
126
608
443
279
161

6
4
3
2
1

2
1
1
1
1

4
2
1
1
1

7
4
3
3
1

12
7
6
5
4

16
10
8
7
5

26
16
13
11
8

46
28
24
20
15

69
43
36
30
22

91
56
47
40
29

116
71
60
51
37

1/0
2/0
3/0
4/0
250

1
0
0
0
0

1
1
1
1
0

1
1
1
1
1

3
2
1
1
1

4
3
3
2
1

7
6
5
4
3

12
10
8
7
6

19
16
13
11
9

25
20
17
14
11

32
26
22
18
15

300
350
400
500
600

0
0
0
0
0

0
0
0
0
0

1
1
0
0
0

1
1
1
1
1

1
1
1
1
1

3
2
1
1
1

5
4
4
3
2

7
6
6
5
4

10
9
8
6
5

13
11
10
8
7

700
750
800
900
1000

0
0
0
0
0

0
0
0
0
0

0
0
0
0
0

1
0
0
0
0

1
1
1
1
1

1
1
1
1
1

2
1
1
1
1

3
3
3
3
2

4
4
4
3
3

6
5
5
4
4


The Basics of Electrical Wires in Conduits


IMPORTANT: The amount of wire fill inside any electrical conduit does not imply how many wires can be stuffed into the conduit, but rather how many wires of the right type may be safely installed to prevent overheating of the electrical wiring.




A conduit that will be used for an electrical project must be approved for the application.

The type of electrical wire to be installed into the conduit must be approved for the project as well, with special attention given to the type of insulation. For example, some types of insulation may not be used for underground projects.

There are several different types of wire insulation which will have a determination about the application the wire may be used for. The temperature rating is just one factor to consider when selecting a wire type.

The amount of wire fill inside a conduit must be configured properly to prevent overheating of the wire, which is why conduit fill tables are very important.

While using a wire fill table for electrical conduit it is best to size the conduit up to the next incremental size to be sure the conduit is not overfilled, and it will make pulling in the wires much easier.





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