Wiring under a double-wide.

[Coppersmith]

When running UF in the crawl space under a double-wide is it allowed to just lie on top of the dirt, or is it required to be supported above it? From what I've seen passed by inspectors, PVC conduit is allowed to just sit on the surface. Seems like this is the same thing.

 

[petersonra]

I thought this was an interesting question. So I looked in the code under UF cable. I see no requirements to support or secure it at all.

I think you might get some kickback from those claiming it is subject to damage under the trailer though.

 

[Coppersmith]

I think you might get some kickback from those claiming it is subject to damage under the trailer though.

This double-wide and most I encounter have a skirt that encloses the crawl space. The only possible physical damage is from rodent activity and that is just as likely in an attic where NM is strung hither and yon.

 

[jumper]

I imagine an inspector could want it treated as NM installed in any other crawlspace.

340.10 Uses Permitted. Type UF cable shall be permitted
as follows:

(4) Installed as nonmetallic-sheathed cable. Where so installed,
the installation and conductor requirements
shall comply with Parts II and III of Article 334 and
shall be of the multiconductor type.

 

[Coppersmith]

I imagine an inspector could want it treated as NM installed in any other crawlspace.

340.10 Uses Permitted. Type UF cable shall be permitted
as follows:

(4) Installed as nonmetallic-sheathed cable. Where so installed,
the installation and conductor requirements
shall comply with Parts II and III of Article 334 and
shall be of the multiconductor type.

Being permitted is not the same as being required. Since it's a direct burial cable, I would think ground contact would be allowed even if it's not buried below ground. It's physically protected by the crawl space except I suppose by people crawling, but this is no different than walking an attic and stepping on exposed NM strewn across the tops of trusses. (Which, of course, everyone here avoids. )

Is the NM in crawl spaces supported to keep it off the ground due to it being a dry space wiring method? Or due to other considerations?

 

[user 100]

Being permitted is not the same as being required.

What 340.10(4) is saying is that you are permitted to use UF in place of NM, and that when you do, it has to comply with the 334 rules for NM.

IOWs, if NM would be allowed for the job, but you use UF instead, you would have to support it like you would if you used NM.

 

[ptonsparky]

NM, and subsequently the UF, is not required to be supported where fished. 334.30(B)(1).

Does your install meet that definition?

 

[Coppersmith]

NM, and subsequently the UF, is not required to be supported where fished. 334.30(B)(1).

Does your install meet that definition?

It might be possible to make a case that it was fished, but probably not in my opinion. I did fish it using a 30 foot long PVC pole to the general area where I needed it (just to avoid some effort and dirt). Then I crawled in (lowest point 12") about 6 feet in to cut through the insulation and poke the cable through the hole I cut in the floor. I did not support the wire because there was a continuous fabric covering (dipping down mostly) under the entire trailer that I didn't want to penetrate. I also could not see through the covering or even reliably feel where good support points would be.

 

[augie47]

You might check 550.15(H). A lot depends on underpinning or lack thereof as that can effect damage & moisture.

 

[zbang]

Since it's a direct burial cable,

spread some dirt over and call it buried ?

 

[Galt]

Don't sound like you have many options.

 

[Little Bill]

Beam clamps!
I suppose you could somehow secure the UF to the clamps but I would just strap some PVC to the clamps and run the UF in that.

 

[Coppersmith]

spread some dirt over and call it buried ?

Actually, that's sort of my point. Table 300.5 says direct burial cables under a building require a zero inch depth. Zero inch means lying on the surface which is why I think I'm correct here.

 

[Smart $]

Actually, that's sort of my point. Table 300.5 says direct burial cables under a building require a zero inch depth. Zero inch means lying on the surface which is why I think I'm correct here.

It also notes "in raceway" in all columns but Columns 2 & 3, the "in raceway" columns.

 

[LarrywdH]

Could you support the cable to treated 4x4's like a roof?