Calculating total stranded kcmil

[Jpflex]

Ive been away from studying NEC code for a while but I wanted to get back into it.

I came across article 110.6 when trying to determine wire size in Kcmil for stranded conductors, the circular mill area for each strand must be multiplied by the number of strands to determine the circular mill area of the conductor.

If i remember correctly if 6 awg or larger is installed in conduit, it must be stranded

Also how is this sizing applied for stranded wire in general? If chapter 9 table 8 says 250 kcmil is 37 (quantity) is this quantity strands since strand numbers are not given elsewhere?

Then 250,000 mil x 37 strand (quantity) = 9,250,000 mills total

This doesnt make sence

A 14 AWG is 4110 mils for both 1 and 7 quantity, so is this done?

 

[infinity]

The kcmil area is based on the quantity and size of all of the strands added together. From your example if 250 kcmil has 37 strands all of the same size each strand would be 6757 CM.

 

[Jpflex]

The kcmil area is based on the quantity and size of all of the strands added together. From your example if 250 kcmil has 37 strands all of the same size each strand would be 6757 CM.

Yes but nec code hamd book 110.6 said to use ch 9 table 8 while using the cm of a single strand and multiply by the number of strands to obtain total kcmil size

However, if the total kcmil is provided in the table why does the nec say to multiply induvidual strand cm x strand number to get total kcmil?

 

[infinity]

Yes but nec code hamd book 110.6 said to use ch 9 table 8 while using the cm of a single strand and multiply by the number of strands to obtain total kcmil size

However, if the total kcmil is provided in the table why does the nec say to multiply induvidual strand cm x strand number to get total kcmil?

Can you post that wording from the NEC?

 

[marmathsen]

From NEC Handbook:
"Table 8 in Chapter 9 and its associated commentary provide the circular mil area for AWG-sized conductors. Where stranded conductors are used, the circular mil area of each strand must be multiplied by the number of strands to determine the circular mil area of the conductor."

250 kcmil wire has 37 strands.
Each strand has a diameter of 0.082 inches, or 82 mils.
82mils² = 6,724 circular mils per strand.
6,724 x 37 strands = 248,788 circular mils

 

[electrofelon]

Seems like that last sentence could be deleted, captain obvious. Also sometimes conductors are composed of different sized strands.

 

[don_resqcapt19]

Why would anyone other than the manufacturer need to do this type of calculation?

You simply use the kcmil number marked on the conductor, or for sizes smaller than 250 kcmil, you look it up Chapter 9, Table 8.

 

[wwhitney]

Why would anyone other than the manufacturer need to do this type of calculation?

What do you do when you've accidentally severed two of the 37 strands in the conductor and want to determine the ampacity of the remaining 35 strands? : - )

Cheers, Wayne

 

[Jpflex]

Why would anyone other than the manufacturer need to do this type of calculation?

You simply use the kcmil number marked on the conductor, or for sizes smaller than 250 kcmil, you look it up Chapter 9, Table 8.

The 2023 NEC handbook says that you must use chapter 9 table 8 to determine the cmil of 1 strand and multiply this by the numner of strands to determine the total kcmil of wire
Or cable. However i have always just read kcmil directly from ch9 table 8

Photos will not upload with my current job android phone

 

[wwhitney]

The 2023 NEC handbook says that you must use chapter 9 table 8 to determine the cmil of 1 strand and multiply this by the numner of strands to determine the total kcmil of wire or cable.

No, it does not, they are two separate statements. I will paraphrase the text from post #5 as: "Use the table. The table was made by taking the size of one strand and multiplying it by the number of strands."

The table doesn't actually have the size of one strand, it only has the total area, so you can't read the size of one strand directly off the table. You can compute the size of one strand by taking the total area from the table and dividing it by the number of strands.

Cheers, Wayne

 

[don_resqcapt19]

The 2023 NEC handbook says that you must use chapter 9 table 8 to determine the cmil of 1 strand and multiply this by the numner of strands to determine the total kcmil of wire
Or cable. However i have always just read kcmil directly from ch9 table 8

Photos will not upload with my current job android phone

The handbook is not code.

The commentary and supplementary materials in this
handbook are not a part of the NFPA Document and do not
constitute Formal Interpretations of the NFPA (which can be
obtained only through requests processed by the responsible
technical committees in accordance with the published
procedures of the NFPA). The commentary and supplementary
materials, therefore, solely reflect the personal opinions of the
editor or other contributors and do not necessarily represent the
official position of the NFPA or its technical committees.