calculation

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 Question by raghavendra B.H posted 11 Aug 2005
 calculation
Hi,

How many cat5e( dia of cable 5square mm ) cables can be layed in a 100mm/50mm raceway. explain clearly with an example. above i have mentioned the dia of the cable

Regards

Raghavedra B.H
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 Answer by Joseph Golan posted 13 Aug 2005
Dear raghavendra,

Depending where you are there many be codes in effect to limit the number of cable in the tray. If you are in the US and your local area has adopted the NEC, there is a limit of a 50% fill which due to air spaces is about 100% of the area.
I find this rule to be very fair and is fairly accurate in design of a pathways system for all areas.

Your cable having a diameter of 5mm and the area calculation is Pi(r)squared
3.14x (2.5)squared=19.66 Sq mm

The tray 100% capacity is 50mmx100mm=5,000 Sq mm
Take 1/2 for the 50% rule = 2,500 Sq mm
Then divide theu seable space by the area of a cable 2,500/19.66= approximately 125 cables.

You should also consult with: the manufacturer of the tray and cable for loading (weight calculation) to determine the safe installation and distance between supports; and the cable manufacturer to insure that there will not be a crushing effect on the bottom cables.

Sincerely,
Joseph Golan, RCDD

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