Conduit Size?

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The Iceman

Senior Member
Location
Florida
I have a copper wire size and conduit quick reference table, and when you get up to and over 60 amps, the conduit size is larger with the grounding wire than without the grounding wire. For example 60 amps, 4 wire cu. calls for 4 #6, 3/4" EMT conduit, but 60 amps, 4 wire with ground cu. calls for 4 #6, and 1 #10 ground, 1" EMT conduit. I thought you don't count the grounding conductor for pipe fill. Can anyone show me what code I'm missing, or is this table wrong?
 

480sparky

Senior Member
Location
Iowegia
You don't count it for derating.

Raceway fill is a matter of simple mathematics.... how many little circles will fit into a big circle. The ground wire still counts as a little circle.
 

infinity

Moderator
Staff member
Location
New Jersey
Occupation
Journeyman Electrician
Very simple, if it fills the pipe it counts.

Table 1 Percent of Cross Section of Conduit and Tubing for Conductors
Notes to Tables
(3) Equipment grounding or bonding conductors, where installed, shall be included when calculating conduit or tubing fill. The actual dimensions of the equipment grounding or bonding conductor (insulated or bare) shall be used in the calculation.
 

celtic

Senior Member
Location
NJ
All of the 3xx.22 articles tell us to use Table 1, Chapter 9
Note 3 to Chapter 9 states:
Equipment grounding or bonding conductors, where installed, shall be included when calculating conduit or tubing fill. The actual dimensions of the equipment grounding or bonding conductor (insulated or bare) shall be used in the calculation.
 

Jerverso

Member
Location
Albuquerque, NM
I was thinking of a New Mexico code.
(6) Section 250.118. Types of Equipment grounding conductors. See this section of the NEC and add the following new subsection: (15) an equipment grounding conductor shall be installed in all branch circuit and feeder raceways on or above a roof. The equipment grounding conductor shall be sized in accordance with table 250.122.
 

celtic

Senior Member
Location
NJ
I was thinking of a New Mexico code.



I was thinking you have no State in your profile...how was anyone to know you were talking about NM's amended NEC?

:smile:

(6) Section 250.118. Types of Equipment grounding conductors. See this section of the NEC and add the following new subsection: (15) an equipment grounding conductor shall be installed in all branch circuit and feeder raceways on or above a roof. The equipment grounding conductor shall be sized in accordance with table 250.122.

I wonder why it applies only to roof work?
 

e57

Senior Member
I wonder why it applies only to roof work?
Rusted or damage by roofers down the line - I have been 'asked' to do the same here from time to time - at one point in time it actually was in at least one local code here too, but don't think it made it back in later cycles.
 

480sparky

Senior Member
Location
Iowegia
I hate to ask a dumb question but on the calculator they show a JAM ratio.

What is that?

Think of three wires in a conduit. They should be, by NEC calculation, under the 40% fill, as long as they are pulled in in a triangluar form. But once they get all 3 in a row, their combined diameters exceeed the inside diameter of the raceway.

Click here.
 
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