# Conduit fill question

• posted

I have a question for the experienced electricians in the group. I need to run a #4-3 type SER cable through an underground conduit. I can find tables in the NEC that cover conduit fill limits for single conductors, but not for cabled conductors. Is the cable considered a single wire for this purpose or 4 wires? Thanks

• posted

Per note 9 NEC 2002 Chpt 9 Tables, multiconductor cables are to treated as single conductor cable. Do get the correct cross section area from manufacturer specs.

• posted

The cross section is the diameter, based on the widest dimension. If it gets twisted that will be the swept area when you pull it in.

• posted

There is a table in the back of the book for cross sectional area. Find out what it is for one wire, multiply by 4, then check the other table for 40% fill area.

• posted

snipped-for-privacy@nospamcox.net (newsreader) wrote in :

I thought that was correct, just wanted a second opinion. Per Mfr. diameter is .77" so I can use 3" conduit to meet 40% fill maximum. Thanks to all who responded.

• posted

Well .77 is way too high for #4 wire.

You are looking for area in SQ INCHES from table 5A sect 70-887 if it is aluminum. For copper it is in table 5 sect 70-884.

Copper = .0824 Aluminum = .0881

.0881 X 4 conductors = .3524

According to table 4, sect 70-882, you can use an 1-1/4" Conduit.

AEC Electric & Controls Michael R snipped-for-privacy@sbcglobalremovethiscrap.net

• posted

I think cross section is by area, not diameter. Therfore: ((.77^2)/(.4))^1/2 = 1.217. So, 1-1/4 inch conduit should be OK.

• posted

I chuckle every time I hear the question....How many #12s can you put in a half inch pipe. Someone asks.......What's the record?

I know you wanted a serious answer. Sorry I don't have one. :)

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Depends on how many bends and LB's. I think I may have set a few records...

MLR

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With, or without insulation? ;-)

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