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-   -   Fence to support conduit? (http://www.diychatroom.com/f18/fence-support-conduit-5771/)

Nomad 01-06-2007 03:17 PM

Fence to support conduit?
 
I've seen DIY jobs of conduit on fencing done before and have checked the NEC and can't see how it is explicitly prohibited but it certainly seems questionable. Practically it seems it would depend on how sturdy the fence is, how much power is being run and how much traffic the area gets.

I'm looking at doing a 20A run that is to run right along a new wood fence. The ground is packed with mature roots so taking advantage of the very sturdy fence with 4" wood posts seemed like something that worth checking into but I can't find any info after much searching.

I've been looking in article 225 of 2005 NEC code but must be missing something.

Any help is appreciated- thanks.

jwhite 01-06-2007 03:48 PM

I would say that using the fence for support is fine, as long as you closely follow the fence. I mean to say this: The side of the fence usually facing into your yard will have the posts. The wiring method will likely be secured to the side of the fence facing your yard also. That would leave a 4 or 6 inch space between the fence and the conduit. This is likely to be problematic regarding future damage.

What would you plan for a wiring method?

Type UF cable would need protection from physical harm.

RNC (commonly called PVC) would need supports every 3 foot for sizes below 1 inch. Most fence posts are on 8 foot centers. If you keep offsetting back to the fence then out to the pole, you will need a J box roughly every six offsets or three poles.

I would look into how difficult it would be to drill holes in the posts large enough for the conduit. I would take a 1 x 2 stip of wood and add it behind where I wanted to run the condut. then I would sleeve the conduit through the holes, and use one hole straps for support. I would also support the conduit about twice as often as needed.

Nomad 01-07-2007 12:40 AM

Thanks for the reply. I was wanting to do RNC - for protection I'd add an extra run of 2x4's the whole length just above the conduit, foot for foot it's better than digging. Drilling holes in the posts would be doable but cutting treated wood always requires extra effort- I was planning on running 3/4" RNC too so it's a lot of drilling. I'll relook at the possibilities however so I appreciate the perspective.

I've spec'ed out a good deal of interior work but little exterior- why the periodic J-box?

jwhite 01-07-2007 08:27 AM

Quote:

Originally Posted by Nomad (Post 29201)
why the periodic J-box?

My proposal would be to closely follow the fence so that kids or other things are less likely to hang on the conduit, which would cause damage. Since as the conduit runs, the posts stick out in the way, this would require offsetting around the fence posts.

Code is 360 deg of bends in any one run of condut between pull points. this is so that you do not dammage the wires while pulling them in.

The most comfortable offset bend is 30 deg. Two are required per offset for a total of 60 deg per fence post.

If you are using PVC you probably will only find 40 deg bends. Making such a shalllow offset will be hard without a heat blanket. IMO a 2 x 4 that is itself not supported for 8 foot at a time would be damaged in a short time. that is why I suggested drilling the posts and running the conduit streight. for 3/4 conduit you would need a nice streight 1 1/4 inch hole.


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