Cable Tray Wiring Layout

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d8mitche

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Location
Toronto, Ontario, Canada
Hi,

I was wondering if it is permissible to stack wires/cables in a cable tray. The NEC tables only show column width which leads me to believe that stacking is not allowed. We will be running a mix of wires from 12AWG Stranded to Fiber Optics to Ethernet to RF Coaxial cables all in the same tray.

I also don't want to run into interference issues. We only have so much space to work with and I could use some advice on how to fit everything in. So, my two main questions would be: 1) Can I stack cables within the tray? 2) How do I avoid interference between Power and Communication Cables?

Any advice would be greatly appreciated!
 
Smart $

Smart $

Esteemed Member
Location
Ohio
d8mitche said:
Hi,

I was wondering if it is permissible to stack wires/cables in a cable tray. The NEC tables only show column width which leads me to believe that stacking is not allowed. We will be running a mix of wires from 12AWG Stranded to Fiber Optics to Ethernet to RF Coaxial cables all in the same tray.

I also don't want to run into interference issues. We only have so much space to work with and I could use some advice on how to fit everything in. So, my two main questions would be: 1) Can I stack cables within the tray? 2) How do I avoid interference between Power and Communication Cables?

Any advice would be greatly appreciated!
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For the size and type conductors you've indicated, single layering is not required. You will need to install a barrier (i.e. tray divider) between power and communications.

Minimum width in Table is based on 20% fill... so you need to total up your cross sectional areas (CSA) of power and communications cabling both together and separately, determine overall minimum width by combined total CSA, and place your barrier based on the separate CSA's.

Avoid interference by distance between types.
 
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Smart $

Smart $

Esteemed Member
Location
Ohio
d8mitche said:
Thank you very much!

Another question if I may, In terms of Power, we are going to have some 24VDC along with 120VAC. Do we require a separate divider/barrier for this as well??

Thanks again!
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Quite possibly... meaning most likely yes. There are particulars involved which lend to a reply more wordy than I care to type at present :)blink:). For starters, read through Article 725. There may be other Chapter 7 and/or Chapter 8 Articles which apply, too. Would have to get into specifics for the installation to make that determination...
 
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copper chopper

Senior Member
Location
wisconsin
Dont forget to bond the entire cable tray with a # 6 copper wire to the egc. and try to lay out your run so that its 6 inches above lights or in between light rows.:sick:
 
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GoldDigger

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Staff member
Location
Placerville, CA, USA
Occupation
Retired PV System Designer
Smart $ said:
Does it make a difference as far as "stacking" (i.e. layering)? I realize stacking and/or multi-conductor cable may make a difference with ampacity adjustment.
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Well, if you are worried about derating because you are not maintaining space between current carrying conductors, would putting a fiber-optic cable (with adequate insulation rating) between two current-carrying wires constitute spacing? Or does the spacing have to be free air? (such as putting one layer in chairs above the bottom layer)
 
augie47

augie47

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Tennessee
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Am I missing something ? In terms of power wiring, is 1/0 not the smallest single conductor allowed ?
 
don_resqcapt19

don_resqcapt19

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Staff member
Location
Illinois
Occupation
retired electrician
augie47 said:
Am I missing something ? In terms of power wiring, is 1/0 not the smallest single conductor allowed ?
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That was the reason for my question. My reading of the OP is that single conductor #12 is being installed in the tray. That was prohibited starting with the 1968 code.
 
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