Direct burial wire - do you sift all rocks out?

[bloomingtonmike]

I am direct burying wire to the shop. Have trenched 24 inches and have rocks in the dirt. Does it hurt to put those rocks back in the trench. Should I fill with black dirt first? 4/0,4/0,2/0,4 mobile home urd is the wire. Trench bends do not make conduit easy.

 

[Charles (in GA)]

Use sand or clean dirt around the wires. Rocks will get up against the wires and eventually eat thru the insulation. I'd put at least 6 inches or so of clean dirt/sand on top before putting the rocky soil back in.

Charles

 

[pattenp]

Your wire is either Mobile Home Feeder (MHF) or it's URD also know as UD. There's a difference as to where MHF can be installed vs. URD.

 

[malibu101]

Around here we use "screenings". It is the fines that are leftover from crushing stone.
They are fine so they will not hurt what they are covering, they level out relatively easy, compact easily, and if in the future you dig around it you will see the different material covering the wire/pipe before ripping it out.

Lay cable trace marker ribbon (or even caution tape if it's all you have) a few inches below finish grade so again future diggers will see it and know there is something below.

 

[wyliesdiesels]

Wow 4/0. U must have some serious loads or long wire run!

 

[arrowhead]

Well since you using direct bury cable anyway, why not just use conduit for the straight lengths and no fittings? That way you only have to worry about the exposed cable around the bends being protected by sifted dirt, the rest will be protected by the conduit.

 

[joe_padavano]

I still struggle with the concept of paying for direct burial cable then also paying for conduit. Yes, I use conduit where required, like under road ways, but otherwise, I just put the wire in the trench. Stone dust under and over the wire solves the rock problem.

 

[Speedy Petey]

Wow 4/0. U must have some serious loads or long wire run!

Or a 200A service.

 

[Speedy Petey]

NO WAY I'd use direct bury service cable in anything but sandy soil, or bedded in a lot of fine material.

If the trench is that bad they should have dug it better.

 

[Speedy Petey]

I still struggle with the concept of paying for direct burial cable then also paying for conduit. Yes, I use conduit where required, like under road ways, but otherwise, I just put the wire in the trench. Stone dust under and over the wire solves the rock problem.

But you're OK with paying for the stone dust and the labor and machines to spread it???

How much "extra" do you pay for DB cable??? I use URD in conduit all the time. It's easier and the same price as individual conductors, and I don't have to mess with stone dust unless the soil is really bad.

 

[wyliesdiesels]

Well since you using direct bury cable anyway, why not just use conduit for the straight lengths and no fittings? That way you only have to worry about the exposed cable around the bends being protected by sifted dirt, the rest will be protected by the conduit.

Thats makes no sense! Why would someone go through all that trouble just to half *** the conduit? If im using conduit Im gonna glue it together fittings and all.

Or a 200A service.

My point exactly. 200a is A LOT of equipment! Probably overkill!

 

[Speedy Petey]

My point exactly. 200a is A LOT of equipment! Probably overkill!

Yeah, good point. To most people, bigger is always better.

 

[arrowhead]

Thats makes no sense! Why would someone go through all that trouble just to half *** the conduit? If im using conduit Im gonna glue it together fittings and all.

Well if you read his posts, the trench layout makes putting fittings on the conduit next to impossible. He's using direct bury cable anyway, so slipping straight lengths of conduit where possible is just some extra insurance against chaffing with the poor back fill material he has. Why is that half assed?

 

[wyliesdiesels]

Well if you read his posts, the trench layout makes putting fittings on the conduit next to impossible. He's using direct bury cable anyway, so slipping straight lengths of conduit where possible is just some extra insurance against chaffing with the poor back fill material he has. Why is that half assed?

Should have made the trench better! And conduit is designed to be a complete system. Just think if that cable ever has to be replaced. If the conduit is complete then all u have to do is pull out the old and pull in the new. The way he suggests, he would have to redig the trench. And URD does fail especially with rocks.

 

[arrowhead]

Should have made the trench better! And conduit is designed to be a complete system. Just think if that cable ever has to be replaced. If the conduit is complete then all u have to do is pull out the old and pull in the new. The way he suggests, he would have to redig the trench. And URD does fail especially with rocks.

That's great Monday morning quarterbacking and all, but your not really helping him solve the problem. He asked if all the soil needs to be sifted and I gave him an alternate solution so he could work with what he had.

 

[Falcon67]

No rocks. Friends just had their house floor jackhammered to fix a pipe leak. They have been there 20+ years at least, cause was a bitty rock that was in the sand pad under the concrete floor resting against the pipe. Took a long time, but it eventually drilled a hole in the pipe.

 

[Charles (in GA)]

Loook at the wire closely. If it has a yellow or yellow striped neutral, it is almost certainly URD and NOT MHF. MHF will have a white stripe neutral.

USE is forbidden by code from being used above ground for any reason except to junction to another type of cable, and is never allowed inside a building, not even 6 inchs inside. The wire must be marked with other markings such as the RHW/RHH. URD is usually dual rated as USE, but NOT rated otherwise (see Southwire spec sheet for UD)

MHF is almost identical looking wire, but has a white stripe neutral, and can be run inside a building (in conduit or proper raceway) in addition to being direct buried or buried in conduit. MHF is also multi-rated as USE-2/RHH/RHW

Charles

 

[Aceman]

I've repaired A LOT of DB aluminum cable.

Installing DB cable in rocky soil without conduit is a mistake. It only takes one little nick in the cable....

 

[joe_padavano]

But you're OK with paying for the stone dust and the labor and machines to spread it???

A load of stone dust isn't very expensive and the "labor and machines to spread it" are me and my tractor. MUCH faster and easier than laying out and gluing conduit, then dragging the cable through it. I actually did exactly this with 4/0-4/0-4/0-2/0 where the direct burial had to run under a gravel road. I only needed to run about 50 ft of conduit, and it was a ROYAL PAIN. The remaining 400 ft went MUCH faster (and yes, the 4/0 was for voltage drop over that long run).

 

[Speedy Petey]

A load of stone dust isn't very expensive and the "labor and machines to spread it" are me and my tractor.

Then IMO your opinion is not very valid to someone either DIYing this or paying to have it done. Not everyone has cheap access to material and obviously not everyone has a machine.
For a typical electrical contractor it is far easier and safer to go the conduit route.

 

[Norcal]

Then IMO your opinion is not very valid to someone either DIYing this or paying to have it done. Not everyone has cheap access to material and obviously not everyone has a machine.
For a typical electrical contractor it is far easier and safer to go the conduit route.

Conduit is cheap insurance in my opinion.

 

[rburke65]

Did a direct berial for my neighbor as he didn't want to spend the money for conduit. About 10 years later we were redoing it in conduit as we lost a leg due to rocks I guess. I would do the conduit......And as always.....just my opinion.

 

[bloomingtonmike]

I did conduit - you guys scared me. Got it installed the last couple days with the help of my wife and a couple friends. Just finished burying most of it. Need to do the connections at the ends still and install the elbow and conduit and bury at the shop end.

Working on the csst gas line now.

 

[bloomingtonmike]

My point exactly. 200a is A LOT of equipment! Probably overkill!

What do you consider a LOT of equipment? Ever been to a techshop/makerspace? I am building my own personal one and own 80% to the machines already.

A taste of some of the equipment here:
http://www.garagejournal.com/forum/showthread.php?t=256669

 

[AP514]

Conduit is cheap insurance in my opinion.

+1


Save now PAY later.....

 

[kaffine]

Put several inches of sand in the bottom before the wire. Put the wire in and cover with sand making sure the wire stays away from the side of the trench. The wire should be surrounded by several inches of sand on all sides. Then any large rocks get removed before backfilling the rest of the way. I would put warning tape on top of the sand and again 6 inches or so below final grade. If I was only going to put one warning it would be the top one. Also draw a map of the run and keep a copy.

 

[Falcon67]

What do you consider a LOT of equipment? Ever been to a techshop/makerspace? I am building my own personal one and own 80% to the machines already.

Eh, just your regular CNC vertical mill, shaper, big giant lathe and stuff. Everybody has those. Well, they wish.

The main deal is - better do whatever best now, because re-doing it a PITA. It's a big pain to back up or change directions, but really less of a total pain now than later. Nice machines, don't skimp too much on feeding them.

Idea - since you have a giant band saw - use the sand as noted, slice some 2" PCV longways and lay it in the trench, then lay the wire, then sand. Or slice some 3" or 4" and lay the wire in that bedded in sand, cover with the other half. Keeps the rocks out and you'd have something to hit before the wire should you be digging in the area in the future.

 

[volleyball]

I did conduit - you guys scared me. Got it installed the last couple days with the help of my wife and a couple friends. Just finished burying most of it. Need to do the connections at the ends still and install the elbow and conduit and bury at the shop end.

Working on the csst gas line now.

After the gas line, run some coax and cat 6 cable above the electric and csst.