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Joined: Apr 2002
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Aldav:
You could 'seal' the PVC conduit that's in the ground BUT there will still be water/condensation in the conduit. AS the green box is buried, with the cover at grade, it will collect water/condensation.

The splices have to be made with connectors that are suitable/listed for the location. That said, over time corrosion will WIN, no matter what you, or me, or anyone else does.

I serviced parking lot lighting for 30+ years and that's the first place we would check. I avoided (as much as possibel) quazite boxes, tried only to use them as a pull box, or when I had to, dug 5' & backfilled with gravel; not that doing so would guarantee drainage.

Silicone loaded wirenuts (Ideal) help; splices 'high' in the box help; but there is no 'cure' for long term.



John
2017 / 2014 NEC & Related Books and Study Guides
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aldav53 Offline OP
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I agree, all you can do, surprised there isn't anything code wise against it.


The Golden Rule - "The man with the gold makes the rule"
Joined: Jan 2005
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I can't help but relate to your confusion ... I felt the same whae I first worked with handholes ... but it comes down to this: different environments require different techniques. "In the ground" is a different environment from "in the rain" or "subject to damage," or "indoors."

There are also no waivers granted to the laws of physics.

Start from this point: stuff in the ground WILL get wet, and WILL get stepped on. Now, let's figure how to deal with these facts.

First, use stuff that won't rust, crumble, or corrode away. SO degrades quickly in even slightly alkaline soil, so we can't use it. Water + air + iron = rust, so even steel isn't enough near the surface. Romex isn't very rock or shovel resistant - better think "UF."

Now, for the wire .... do you want to use something whose "rust" is an insulator - or a good conductor? Copper oxide is a pretty decent conductor; aluminum oxide isn't.

SO ... we've settled on plastic pipe with copper wires in it. What are we to do about junctions?

Since you'll need to reach down into the hole - remember, you need to BURY the pipe, so a small box on the surface won't do - our "box" needs to be large enough for your arm to enter. Maybe both arms. Since, when you're not working on the wires, that box will be walked on, mowed over, driven on ... the box needs to have some strength. It also needs to be held in place.

The boxes are held in place by the earth around them - note the flanges, or tapered sides some have - as well as that gravel under them. Any weight applied to the cover gets transmitted to a large area of the ground, so the box stays in place.

Sure, water will enter. That gravel also helps the water drain away. Remember, water will find it's way IN ... let's make sure it has a way OUT. Now all we need to do is seal the actual connections against water.

We do this with various splice kits, or connectors.

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aldav53 Offline OP
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Thats all well and good, but goes against other things like running romex outdoors up in an eve of a home, or in pipe. This isn't legal because of damp locations, which is nothing compared to the underground J-box with no bottom and splices made.
Guess thats one of those code issues that'll never be really clear.

Also, years ago we use to run romex in residential garages, in open studs, and it was legal, the inspectors passed it always. Maybe that code changed by now.


The Golden Rule - "The man with the gold makes the rule"
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I hope I didn't mislead you ... Romex is NOT allowed for direct burial. With my example, I meant to compare the light construction of romex, to the far heavier - if in many ways similar - construction of UF cable.

Joined: Jul 2004
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I wonder how many thousands of miles of Romex is working quite happily in wet and direct buried applications. If you ever get very far out of town you see Romex used for everything.


Greg Fretwell
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aldav53 Offline OP
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probably true..


The Golden Rule - "The man with the gold makes the rule"
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I've never seen a junction box underground that didn't have water in it. Maybe you could develop the first. Some forms of electrical work need regular maintenance, underground connections tend to fail over time, thats just the way it is. I try to avoid them at all costs but.....

Joined: Apr 2002
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Reno:
A very eloquent explanation.

Greg:
Ya also find nmc 'in-town' at a lot of places it shouldn't be.

As I mention to those that inquire.....I'm not the writer of the rules (NEC), I am only the enforcer. The best comment I heard recently from a HVAC tech..."the wet paper helps keep the two insulated conductors cool"!! Best part was he was real serious about that. (12's on a 50 amp MOCP/39.5 FLA Cu.)



John
Joined: Nov 2000
Posts: 2,148
R
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Originally Posted by aldav53
Hard to believe the THHN-THWN is good for wet locations since the wires corroded and shorted out. I had to replace them.

If the wire was corroded within the raceway, then it was damaged when it was installed and the damage let the water under the insulation. If the corrosion was at the splices, they were either the wrong splices or not properly installed.


Don(resqcapt19)
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