Cable Tray Rung Spacing

[Humble2000]

Dear Friends,
Is there a formula to calculate the ladder type cable tray
rung spacing?
I know that they come in 6"-9"-12"-24" spacing and 12" is most popular;however what is the rule of tumb or formula that is used for this purpose?
Any feedback is apprceited.

 

[cuky2000]

Consult the NEC Article 318. Also check if the enclose link could help

http://www.chalfantcabletray.com/cgi-bin/cabletray_2Config.asp

 

[resqcapt19]

If you are using the 2002 or 2005 NEC the cable article number is 392. Many of the Chapter 3 articles were re-numbered for the 2002 edition of the NEC.
Don

 

[rbalex]

I would also refer to the Cable Tray Institute's site:

http://www.cabletrays.com/

For practical consideration, single conductors #1/0 to #4/0 may only be installed where the rung space is 9" or less. See [NEC 2005]392.3(B)(1)(a). Otherwise I know of no particular restrictions.

 

[waross]

Try this link.

http://alliedsupport.com/literature/pdf/CT_NEMA.PDF

STANDARDS
NEMA STANDARDS
VE 1-1991
REV. NOVEMBER 1993
Scope
This standard covers continuous, complete, metallic systems of ladder,
trough, solid-bottom or channel cable tray intended for, but not limited to,
the support of power, control and signal cables.

4. Rung Spacing on Straight Sections - 6", 9", 12", or
18" (152mm, 229mm, 305mm, or 457mm) on centers.
5. Radii - 12", 24", and 36" (305mm, 610mm, and 914mm).

18" spacing may not be available from all manufacturers.
yours