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Joined: Feb 2004
Posts: 494
M
Member
Hi,
I am still trying to pin down the number of Siamese cables I can get in a 2 inch schedule 40 PVC and 2" EMT.

Here is what I have come up with thanks to the previous thread.

SIAMESE CONDUIT FILL CALUCLATION BASED ON 40% FILL

Siamese Cable/Combo (RG59 & 1 Pair #22 AWG 1/2" Diameter)

1/2"=0.50"
Pi R(squared)=(.50*.50)*3.14159=
.785" area.

40% of 2" EMT = 1.342"
1.342"/.785"=1.7 cables

40% of 2" Schedule 40=1.316"
1.316"/.785"= 1.6 cables

I measured the actual cable and it is 1/2".

this does not jive with the follwoing calculations done at Belden cables site:
http://bwccat.belden.com/ecat/images/ConCap.htm

something smells fishy..

Thanks for any replies..

-regards

Mustang

[This message has been edited by mustangelectric (edited 11-01-2004).]

2017 / 2014 NEC & Related Books and Study Guides
Joined: Jul 2004
Posts: 9,645
G
Member
The first thing I notice is you are squaring the diameter, not the radius.
They are getting around this by using 3.14/4 (.785) instead of pi.
Try it using .25 for the radius, squaring that and multiplying it by 3.14


Greg Fretwell
Joined: Jul 2004
Posts: 9,645
G
Member
If I was being lazy or didn't have a calculator I would look at table 5, pick a conductor the size of my cable (in your case 2/0 TFE,PFA,PFAH,Z is close enough for guv'mint work at .508), then use the conduit fill table in annex C.


Greg Fretwell
Joined: Feb 2004
Posts: 494
M
Member
Hi,
Thanks for the reply. I did that already but I know that there are different calcs for straight runs or runs with conduit bends and maybe some other factors I am not quite sure on when dealing with this type of cable.

The calculation I did was from a recent thread in the forum on the same subject.

I will look at the calculation again.

I am not sure if it is right.

Thanks

Greg

[This message has been edited by mustangelectric (edited 11-01-2004).]

Joined: Aug 2003
Posts: 1,374
R
Moderator
Mustang:

1/2" diameter cable has a radius of .25"

.25*.25=.0625
.0625*3.14=0.196

So, 0.196 is your cable's area.
At 40% your EMT has an area of 1.342
1.342/0.196=

6.8 cables allowed in the EMT.
6.7 cables allowed in the RNC.
[Linked Image]


Ryan Jackson,
Salt Lake City
Joined: Feb 2004
Posts: 494
M
Member
Hi,
Thanks for the replies. I see the error and appreciate the correction.

What is the difference in the calculation for the Siamese RG59 in a conduit with 3 90's? anybody know?

How do you calculate the Jam Ratio?

thanks again,

Mustang

[This message has been edited by mustangelectric (edited 11-01-2004).]

Joined: Aug 2003
Posts: 1,374
R
Moderator
The jam ratio is the inside diameter of the raceway divided by the outside diameter of the conductor. This value should be 2.8 to 3.2 according to industry representatives. [Linked Image]

[This message has been edited by Ryan_J (edited 11-01-2004).]


Ryan Jackson,
Salt Lake City
Joined: Feb 2004
Posts: 494
M
Member
Thanks for the great replies..very useful information..

-regards

Mustang


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