Running 5KV cabling on the ground

[clausb]

I am working on a radio tower project where we have to run 5K feeder up the side of a mountain, ~3500' to a tower site. Looking at using a special, URD cable with overall corrugated aluminum covering and a watertight plastic covering on top of that. Kind of a 5K URD liquid tight flex cable.

Anyone have any experience on this type of install? NEC does not really address cables on the ground - am I missing something?

 

[fmtjfw]

I can find nothing about "on the ground"

I can find nothing about "on the ground"

Table 300.50 note "2 Where solid rock prevents compliance with the cover depths specified in this table, the wiring shall be installed in a metal or nonmetallic raceway permitted for direct burial. The raceways shall be covered by a minimum of 50 mm (2 in.) of concrete extending down to rock."

Otherwise 30 inches deep and Table 300.50 d Underground direct-buried cables that are not encased or protected by concrete and are buried 750 mm (30 in.) or more below grade shall have their location identified by a warning ribbon that is placed in the trench at least 300 mm (12 in.) above the cables.

If in RMC or IMC 6 inches of cover.

 

[fmtjfw]

Do you have 3500 feet of right of way for this cable? Can you get the power company to run it for you or use a pole line?

If you strung the cable (with messenger) on poles you could come under art 399. It might be cheaper than all that concrete and ditching.

If you have this "just on the ground" what reliability do you expect?

Are you using fiber or microwave for the signal part, can you share a pole line with fiber???

 

[don_resqcapt19]

I don't think there is any code rule that says you can't install it by laying it on the ground and securing it per the cable article that applies.

 

[clausb]

I know this particular cable has been installed in this manner in the past at cell tower sites at the tops of mountains in the northeast. A pole line is not possible without cutting a wide path to ensure it does not get pulled down by trees in a storm. On the ground actually will give us more reliability. The only persons seeing and able to come in contact with the cable are hunters.

I am trying to ferret out the Code that might apply to this type of installation, but am coming up short. Plenty of code about buried wiring, but not much on exposed. I think the trick is to make sure that it is appropriate for the "where subject to damage" we see throughout the Code.

There is actually a URD cable laying on the ground on the same path we are going to follow; just that this installation we want to make sure all is meeting Code and acceptable to the AHJ (I do not think AHJ is aware of the existing line).

 

[clausb]

...article 328.10(6) is the answer. It allows the corrugated cable with overall water impervious coating (...per the requirements for MC cable) to be installed in accordance with 300.37.

 

[fmtjfw]

Very interesting

Very interesting

328 is MV cable.
I agree on the ground is "above ground". But you are using 328.10(6) to go to 300.37. 300.37 says MV can only be exposed in locations accessible to qualified people. The general run of the mill hunter is not a "qualified person" under the NEC / NFPA 70E.

300.37 Aboveground Wiring Methods. Aboveground conductors
shall be installed in rigid metal conduit, in intermediate
metal conduit, in electrical metallic tubing, in RTRC and
PVC conduit, in cable trays, in auxiliary gutters, as busways,
as cablebus, in other identified raceways, or as exposed
runs of metal-clad cable suitable for the use and purpose. In
locations accessible to qualified persons only, exposed runs
of Type MV cables, bare conductors, and bare busbars shall
also be permitted. Busbars shall be permitted to be either
copper or aluminum.

Here the question is your cable metal-clad cable suitable for the use and purpose
or does it fall under In locations accessible to qualified persons only, exposed runs
of Type MV cables

 

[fmtjfw]

Sunlight

Sunlight

The other thing to consider is if your cable is "listed" for use exposed to sunlight. I know some 5KV URD is.

 

[clausb]

I read 300-37 as two separate sentences having two separate statements, but I could be interpreting it the way it works best for me. I read the second sentence describing spaces or rooms where wiring is routed exposed, often times MV cables with exposed, energized terminations, like in older transformer vaults, accessible to qualified personnel only (in proper PPE, etc.).

I read the first sentence as being MV cables in raceway or metal-clad, routed where they are open to the public. Say, for example, routing down a pole along a sidewalk to underground.

 

[clausb]

...the outer plastic covering is sunlight resistant and cable is UL per Okonite.

 

[clausb]

To follow up, met with the inspector this afternoon. He was familiar with the cable from similar installations. All is good. The cable is a "custom" product from Okonite that they call Mountain Cable.