Concrete Trench as Raceway

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beanland

beanland

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Vancouver, WA
I am seeking thoughts on the NEC code issues around concrete trench such as made by Trenwa or Utility Vault.

Does a 24" x 24" concrete trench with 4" concrete removable cover buried in the ground qualify as a raceway, or is it a cable tray?

If it is a raceway, can conductors be installed random-lay like in any conduit or must they be secured like in a cable tray?

Do I have to install the conductors in conduit in the trench? (A raceway in a raceway?)

Do the conductor fill (310.15) and ampacity (310.16) for raceways apply in something this large?

Since it has a removable cover, is it a gutter? Since concrete trenches are not UL listed, they cannot be gutters. And, they can extend more then 30 feet, too.

What specific parts of the NEC apply to in-ground concrete trenches?
 
Are you using the trenwa to run control wiring cables and fiber optics at a transmission sub-station ??

John
 
I only have a few more minutes then I have to run, If your using this where I believe you are , your going to be running control wiring and optics in it?

The conduits that carry the control wiring from equipment like the GCBU's into the trenwa and just stubbed in the the open bottom construction of the trenwa, then the control wiring and /or optics cables are run into a relay building and terminated on the control equipment, this is were I have seen their use.

I will stop back in tomorrow night when I get a chance but pushed for time now.

Later John
 
Trench Use

Trench Use

This is not a substation application, NEC would not apply there. This is across a parking lot. Lids will be H-20 load-rated. Wiring is power. Wiring is on the customer side of the meter so NEC applies. Customer wants the flexibility to tap into the trench in the future. Normally, I would suggest handholes and conduit but they like the concrete trench idea. I just see nothing in the NEC that addresses concrete trench like this. Would rather know beforehand about any hitches.
 
If I were an inspector I'd make you keep it off the ground, out of the water. Runnoff / leaks always permiate the trench.

I'd also feel more confindent in this work if I saw orderly spacing between wires. That might keep an inspector from interpreting cable tray requirements or other red flags.
 
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beanland,

Do a 'Trenwa' search,there site shows the cables laying on the bottom of

the sections,with the grounding on clips higher up off the bottom.
 
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