Sq/in to cur. mil.

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chris kennedy

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Miami Fla.
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60 yr old tool twisting electrician
Getting a headache. Need to convert this(conduit body fill).

Ugly's pg 134.

Sq/in ? 1.273239 ? 10 to the 6th power.(10,000,000)

This should give me cir. mils but no.


500 THHN = .7073in? ? 1.273239 ? 10,000,000 =9,005,619

Wheres the 500 mcm in that?
 
First, you have one too many zeros. 10 to the sixth is one million, or 1,000,000. So your final answer should have been closer to 900,000. Are you, by chance, using the overall conductor size, including the insulation, in your figure of .7073? I don't have my book handy, so I can't check it out.
 
Circular mil refers to the area of the conductor only.

The area referred to in Table 5 refers to the area of the copper PLUS the insulation. To find the area of just the conductor, use Table 8.
 
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charlie b said:
Are you, by chance, using the overall conductor size, including the insulation, in your figure of .7073?
Yes, .7073 is from chapter 9 tbl 5.

What I'm trying to figure out is if I have for example a 2" LB marked:

Max 3 4/0

And need to compare total cir. mils to the 4 2/0 I need to install but am slightly over can I compare cir. mil. to cu/in?

Before anyone says just up size the LB, when I get into 4" conduit I have to use gutters instead. Just thinking too much here I guess.
 
chris kennedy said:
What I'm trying to figure out is if I have for example a 2" LB marked:

Max 3 4/0

And need to compare total cir. mils to the 4 2/0 I need to install but am slightly over can I compare cir. mil. to cu/in?

Is that even allowed or required?

I am asking, I really don't know.
 
You cannot convert square in to cubic inches or vise versa, Its not possible , A square in is area and cubic inch is a volume, The easiest way I have found is to go online and google max number of conductors in conduit body, Appleton and crouse and hinds are the most common brands.
 
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duluthelectrical said:
You cannot convert square in to cubic inches or vise versa, Its not possible , A square in is area and cubic inch is a volume, The easiest way I have found is to go online and good max number of conductors in conduit body, Appleton and crouse and hinds are the most common brands.

He's trying to convert square inches to circular mils. Both are measurements of area.
 
iwire said:
Is that even allowed or required?

I am asking, I really don't know.
Just a calc for what works. If I have an LB that says Max 3-4/0s I will go to Tbl 8 and see the cir. mils are 634,800.

I want to put 4 1/0's in that LB and that comes to 422,400. IMO no problem.

I deal with alot of 4" conduit and the LB's arent listed for the conductors allowed in the raceway and it makes me wonder.
 
[URL="http://tbn0.google.com/images?q=tbn:OXGY5FmF05oqiM:http://www.gearseds.com/curriculum/images/figures/web_onecircular_mil.gif"]http://tbn0.google.com/images?q=tbn:OXGY5FmF05oqiM:http://www.gearseds.com/curriculum/images/figures/web_onecircular_mil.gif[/URL]

[URL="http://tbn0.google.com/images?q=tbn:bO46R3xRtKCfWM:http://upload.wikimedia.org/wikipedia/en/4/47/Circmil.jpg"]http://tbn0.google.com/images?q=tbn:bO46R3xRtKCfWM:http://upload.wikimedia.org/wikipedia/en/4/47/Circmil.jpg[/URL]

32NE0313.GIF

If a wire has a cross-sectional diameter of 1 mil, by definition, the circular mil area (CMA) is A = D2, or A = 12, or A = 1 circular mil. To determine the square mil area of the same wire, apply the formula A = pi X r2; therefore, A = 3.14 X (.5)2 (.5 representing half the diameter).

From this place here
 
cadpoint said:
32NE0313.GIF

If a wire has a cross-sectional diameter of 1 mil, by definition, the circular mil area (CMA) is A = D2, or A = 12, or A = 1 circular mil. To determine the square mil area of the same wire, apply the formula A = pi X r2; therefore, A = 3.14 X (.5)2 (.5 representing half the diameter)...
Aye... circular mils, while it is an area measure, is circular :roll: , not square. Thus square area of one circular mil is .5? mils ? Pi = 0.7853981634 sq mils.
1 cmil = 0.0007853981634 sq. in.​
I think I got that right :wink:
 
Look at it this way:

Look at it this way:

chris kennedy said:
Getting a headache. Need to convert this(conduit body fill).

Ugly's pg 134.

Sq/in ? 1.273239 ? 10 to the 6th power.(10,000,000)

This should give me cir. mils but no.

500 THHN = .7073in? ? 1.273239 ? 10,000,000 =9,005,619

Wheres the 500 mcm in that?

Area of one CM is,

1 CM = (pi/4) x (10^-3)^2
= 0.79 x 10^-6 sq. in.

1 sq. in. = 1.27 x 10^6 CM

UGLI is right.
 
I only posted the first link of google for 1 circular mil = .001"

But to answer another thread - they make Square Wire !

A Dime is Ten mils, ten dimes is an inch, what my friend is saying ...>>
We just had the argument / conversation about what the size limit stamp means,
welp ... manufactures state the limit, I don't think they made any bad assumptions
on the type of insulation, I'm sure its a mean size though.

Just cause I can, I'm posting another link to muddy the water... from here

|
sdef_definition.gif
- The circular mil is a unit of area used especially when denoting
|the cross-sectional size of a wire or cable. It is the equivalent area of a
|circle whose diameter is 0.001 (10-3) inch, or approximately 0.7854
|millionths of a square inch (or 2.5 x 10-7 times pi).

|In plane geometry, area always varies in direct proportion to the square
|of the linear dimension. Thus, if wire A is twice the diameter of wire B,
|then wire A has four times the cross-sectional area, in circular mils, of B.
|If wire C is 1/5 of the diameter of wire D, then C has 1/25 the cross-
|sectional area, in circular mils, of D. In this respect, the circular mil is like
|any other unit for measurement of area.

|Because the circular mil is, as its name implies, based on a circular unit of
|measure rather than a rectangular unit, conversions between circular mils
|and square units such as the meter squared (m2) or centimeter squared
(cm2) can be awkward. To convert circular mils approximately to meters
|squared (m2), multiply by 5.066 x 10-10. Conversely, multiply by 1.974 x
|109. To convert circular mils approximately to centimeters squared
| (cm2), multiply by 5.066 x 10-6. Conversely, multiply by 1.974 x 105.

Can you develop the A=B/C problem yet, Chris ?
 
???

???

Most conduit bodies I remember have the # and size of 'XHHW' conductors.

Using Table 5 of Chapter 9 I get:

4/0 conductor has a sq. in. area of .3197 x 3 (conductors) = .9591

Assuming you are installing THWN conductors:

2/0 conductor has a sq. in. area of .2223 x 4 (conductors) = .8892

The (4) 2/0 conductors take up less space than the (3) 4/0 conductors so you are good to go.
 
Chris, don't get confused about circular mils as listed in the tables. It does not include the space between the strands or insulation but is the wire area only.

For example:
500 kcmil has 37 strands with a diameter of 0.116 inches each. This is 37 x 116^2 = 497.872 or 500 kcmil. The problem is that the total conductor is bigger than that. The 37-strand conductor has a diameter of 0.813 inches or equivalently 813^2 = 661.0 kcmil. The 500 kcmil THHN in table 5 has a diameter of 0.949 or equivalently 949^2 = 900.6 kcmil.

Why not just use the area given and forget the circular mils? For your question (assuming THHN):
3 x 4/0 = 3 x 0.3237 in^2 = 0.9711 in^2
4 x 2/0 = 4 x 0.2223 in^2 = 0.8892 in^2 = looks okay but there is a question about the space between the cable and the packing factor but that is another post.

If you want to use circular mils:
3 x 4/0 (642 mil dia) = 3 x 642^2 = 1236.5 kcmil
4 x 2/0 (532 mil dia) = 4 x 532^2 = 1132.1 kcmil = looks okay with caveat above.
 
mivey said:
Chris, don't get confused about circular mils as listed in the tables. It does not include the space between the strands or insulation but is the wire area only.

Suppose he's got compressed strands?


banana.gif

(I feel like the Eric Idles' charactor who says in the Monty Python Self-Defense skit, "What about a man with a pointed stick?")
 
480sparky said:
Suppose he's got compressed strands?


banana.gif

(I feel like the Eric Idles' charactor who says in the Monty Python Self-Defense skit, "What about a man with a pointed stick?")
Then see table 5A
 
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