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Siamese Cable Fill Calculation #90150
11/01/04 01:22 PM
11/01/04 01:22 PM
M
mustangelectric  Offline OP
Member
Joined: Feb 2004
Posts: 494
Bentonville, AR
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).]


Electricity has no respect for ignorance!
2017 / 2014 NEC & Related Books and Study Guides
Re: Siamese Cable Fill Calculation #90151
11/01/04 03:19 PM
11/01/04 03:19 PM
G
gfretwell  Online Content

Member
Joined: Jul 2004
Posts: 9,348
Estero,Fl,usa
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
Re: Siamese Cable Fill Calculation #90152
11/01/04 03:38 PM
11/01/04 03:38 PM
G
gfretwell  Online Content

Member
Joined: Jul 2004
Posts: 9,348
Estero,Fl,usa
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
Re: Siamese Cable Fill Calculation #90153
11/01/04 03:48 PM
11/01/04 03:48 PM
M
mustangelectric  Offline OP
Member
Joined: Feb 2004
Posts: 494
Bentonville, AR
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).]


Electricity has no respect for ignorance!
Re: Siamese Cable Fill Calculation #90154
11/01/04 06:53 PM
11/01/04 06:53 PM
R
Ryan_J  Offline
Moderator
Joined: Aug 2003
Posts: 1,374
West Jordan, Utah, USA
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
Re: Siamese Cable Fill Calculation #90155
11/01/04 08:59 PM
11/01/04 08:59 PM
M
mustangelectric  Offline OP
Member
Joined: Feb 2004
Posts: 494
Bentonville, AR
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).]


Electricity has no respect for ignorance!
Re: Siamese Cable Fill Calculation #90156
11/01/04 09:27 PM
11/01/04 09:27 PM
R
Ryan_J  Offline
Moderator
Joined: Aug 2003
Posts: 1,374
West Jordan, Utah, USA
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
Re: Siamese Cable Fill Calculation #90157
11/02/04 10:07 AM
11/02/04 10:07 AM
M
mustangelectric  Offline OP
Member
Joined: Feb 2004
Posts: 494
Bentonville, AR
Thanks for the great replies..very useful information..

-regards

Mustang


Electricity has no respect for ignorance!

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