conduit sizing for cables

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Ivan Young

Member
Location
Simpsonville, South Carolina
Gentlemen, I am an apprentice preparing to take my exam soon and was wondering if you can help me with a question . I am familar with going to table 8 for conductors of the same size and type amd going to table 5 for conductors of different size and type and then going to table 4 to size the conduit. What about multi-wire cables, where would I go to size the conduit?
Thanks.
 
LEO2854

LEO2854

Esteemed Member
Location
Ma
Ivan Young said:
Gentlemen, I am an apprentice preparing to take my exam soon and was wondering if you can help me with a question . I am familar with going to table 8 for conductors of the same size and type amd going to table 5 for conductors of different size and type and then going to table 4 to size the conduit. What about multi-wire cables, where would I go to size the conduit?
Thanks.
Click to expand...


Look at the first page of Chapter 9.

(9) A multiconductor cable or flexible cord of two or more
conductors shall be treated as a single conductor for
calculating percentage conduit fill area. For cables that
have elliptical cross sections, the cross-sectional area
calculation shall be based on using the major diameter
of the ellipse as a circle diameter.
Click to expand...
 
I

Ivan Young

Member
Location
Simpsonville, South Carolina
Thank you Leo, I see it. I made a mistake in my typing. For wires of the same size and type Annex C should be used. If you have a cable with say three conductors so you treat it as one conductor. One with say twelve conductors you treat it as one conductor. I understand the part about treating it as one conductor, but how do you determine the size of that one conductor, is there a special table for it?
 
LEO2854

LEO2854

Esteemed Member
Location
Ma
Ivan Young said:
Thank you Leo, I see it. I made a mistake in my typing. For wires of the same size and type Annex C should be used. If you have a cable with say three conductors so you treat it as one conductor. One with say twelve conductors you treat it as one conductor. I understand the part about treating it as one conductor, but how do you determine the size of that one conductor, is there a special table for it?
Click to expand...

That is a good question and the answer is probably right in front of me but i can not find it..at the moment.:blink:
 
T

texie

Senior Member
Location
Fort Collins, Colorado
Occupation
Electrician, Contractor, Inspector
Ivan Young said:
Thank you Leo, I see it. I made a mistake in my typing. For wires of the same size and type Annex C should be used. If you have a cable with say three conductors so you treat it as one conductor. One with say twelve conductors you treat it as one conductor. I understand the part about treating it as one conductor, but how do you determine the size of that one conductor, is there a special table for it?
Click to expand...

In the field I just measure the diameter or get the spec from the manufacturer and do the math for fill. But for testing purposes I've never seen an exam where they didn't tell you the diameter of the cable as there are no standard cables like wire.
 
infinity

infinity

Moderator
Staff member
Location
New Jersey
Occupation
Journeyman Electrician
If you read Leo's code section it tells you that you use the diameter of the cable as if it were a single conductor. It also tells you that if you have a flat cable, like 2-wire NM, that you would use the largest diameter of the cable and then calculate as if it were round.
 
D

dkeaux@gmail.com

Member
Location
Greensburg, KY.~ USA
Measure the OD of the cable Square it then multiply that by .7854 then divide by 100% area of your conduit size
53% max fill for a single cable



Ivan Young said:
Gentlemen, I am an apprentice preparing to take my exam soon and was wondering if you can help me with a question . I am familar with going to table 8 for conductors of the same size and type amd going to table 5 for conductors of different size and type and then going to table 4 to size the conduit. What about multi-wire cables, where would I go to size the conduit?
Thanks.
Click to expand...
 
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