450' wiring conduit -how to assemble?

[lhfarm]

This is the continuation of my on going project to get power to the barn. To date, I've had two estimates that differ by $800 and have now called the power company for their advice. The power company, based on a phone conversation, is going to recommend a new 320 amp meter base and a 200 amp cutoff at the meter. For background the power comes into the garage, where the meter is located. 200 amp service runs under ground into the house.

The first bid was no conduit, 2/0 feed from a breaker in the garage panel. Second bid is for conduit, but basically the same setup. The power company says no less than 4/0 and in conduit for our soil conditions (rocks).

The cheapest trenching is $1/foot, but I've got a BH (why I'm in this forum). So I'm going to dig the trench and lay the conduit. I've search the board and found one good discussion, but I unclear of how I should proceed. Do I dig the trench (12" bucket) to the required 2' depth and then start assembling the conduit (2" 10' sections) on the ground, then lower them into the trench. Or do I glue them up in the trench? Should I dig 10', install a section (capping it to keep the dirt out) and back filling as I go?

I'm sure the part of the higher priced bid was for using the guys cable pulling equipment, because he mentioned the distance and the need for specail pulling equipment. Am I going to need him to pull the cable for me or will a rope, cable lube and my back be able to pull 4/0 that far?

Any advice appreicated. If I haven't made it clear, I'll try to answer questions too.

Thanks,

 

[kennyd]

I like to trench and lay pipe as you go, so you can back fill as you go also. That way there is not a long trench open if you get bad weather or have kids that could get hurt.

Just glue it well, then suck a string through with your shop-vac, then use the string to pull a 1/4" rope.

 

[tommu56]

I suggest as kdenny said on the dig open 20ft up put 1 length in and dig another 10ft add another length of pipe that way the only 20 ft of trench is open at a time.

or dig enough that you can put pipe in and back fill in about 4 hrs and repeat and leave 5 to 10 ft open for next day.

I usually put an extra conduit in for phone or cable and I bed the pipe in screenings because of the rock in my area it protects the pipe from the back fill process.

And it helps when digging again you hit the screenings and get out the shovel and dig hand.

tom

 

[John47]

I dug my trenches, laid the plastic conduit out alongside, then fed the cable through each length, lowered them into the trench and glued them together. Heavy single core cable is stiff!! I didn't encounter any problems that way.
I ran one run from the power pole to my shop, and one to the house, each with 200 amp service.

 

[jinmared]

when I ran my wiring to my shed I dug the ditch then I laid out my wire along side of the
ditch , then I ran the 2 inch gray electrical plastic conduit down the wire and glued it up as I went along. I used 4.0 4.0 2.0 wire .when it was all glued up and cured over night I then rolled it into the ditch. The conduit is really flexible and went in the ditch with little effort on my part. The conduit I used I got at Home Depot and it had a socket on one end that you inserted the end of the next piece into after gluing , therefore no couplings to use. It is gray in color and is approved for in ground use by the Electrical code in my state (WA).

 

[CurlyDave]

I dug my trenches, laid the plastic conduit out alongside, then fed the cable through each length, lowered them into the trench and glued them together. Heavy single core cable is stiff!! I didn't encounter any problems that way.
I ran one run from the power pole to my shop, and one to the house, each with 200 amp service.

I think John has it right. 450' is a long way to pull cable, especially with heavy wire. Dig your trench, piling all the spoils to the same side. Lay out your cable on the other side, slide conduit sections over the cable and glue as you go. This has the advantage of allowing you to inspect the cable before you install the conduit. I would hate to be pulling cable and 430' into a 450' pull discover that there is a flaw in the insulation...

You are going to do a lot of walking sliding those sections of conduit over the cable. The way I figure it, with 10 ft sections, you will make 45 trips, an average of 225 ft, plus another return tip each time to get another section. This is over 20,000 feet, nearly 4 miles.

If you start with half the conduit at each end, and walk to the middle to start the gluing, you only walk half that distance. Use 20' pieces instead of 10' and you halve the number of trips again, getting it down to only a mile of walking.

 

[Illini22]

4/0 phases with a 2/0 nuetral is the correct wire size. personally I would go with direct bury al.. Just over 2.00 a foot at menards. Same cable as many, many utilities use. Going direct bury is much cheaper and yes easier to fix. very easy to find a fault in a direct bury cable. If cable gets hit you can just splice where it occurred. You wouldn't be repairing your service entrance that got ripped off the wall.

 

[JB4310]

I had a 200 amp service brought UG 100+ ft to my house, we dug the wholw trench and put the pipe together in the trench.

Used 3" pipe for the service (4/0) we used two 2 inchers just for phone and cable. Put phone and cable in one 2" and left one for future use.
Not sure but 2" pipe may be small for that wire gauge, hope you have no bends in the run
We did that shop vac trick with the string like Kenny mentioned, I was skeptical about how well it would work, I held the string ball on a stick, we had balled up something at the end of the string to fit snug in the pipe, man as soon as we turned the vacuum on that string was through that 100FT in just a second or 2.

JB.

 

[EddieWalker]

Be sure you do exactly what the power company requires. Wire size and conduit size are factored together and making any changes will cause problems.

That said, dig the entire trench. You will find that it's tricky to get a smooth bottom. Since this is conduit and not water or drain line, you can get away with a rougher bottom then you'd want for the other two types of lines. Still, you'll want to walk the line after it's dug and clean it up with a shovel. Be sure to put the dirt on the side that you want it for backfilling. You don't want to use the backhoe to fill the trench. It's too slow. I've used the box blade with good results and also my loader bucket.

I then unroll the wire along the trench, but not in the trench. Once unrolled, it will curl at the ends some, but mostly lay flat. Then decide what end you want the bells on the conduit. Start at either end and slide the conduit over the wire to the halfway point. Then just keep sliding down one piece at a time from either end until you get to the point where you add your sweeping 90's and connect it to the boxes at either end.

The pros will install the conduit first the suck a line through it with a vacuum. Usually a plastic bag at the end of the line will help with the suction of the line. Then when the line is through the pipe, they use it to pull a heavier line through that will be strong enough to pull the cable. Then pull the cable through the line with whatever you have that has enough power to do this. If you don't have a winch or something like that, the tractor might work. Greasing the wire will help, but it's still an effort and the wire is heavy. Very heavy!!!

By myself, I can do just about any sized line the way I described. Pulling wire through conduit is also doable, but allot more effort and requires an way to actually pull that wire. To me, it's more work and effort that way to get the same results.

Good luck,
Eddie

 

[Uncle Doug]

I worked as a industrial electrician in a prior life.

Will you be pulling the wire or the power company? There are certain requirements as far as conduit size for each combination of wire sizes. Also they may require a pull point some where in the middle of the run with a junction or splice box. Some building codes may also require the conduit be encased in red concrete but usally on private rural property it is not required.

That length of run and wire size would be more than a one man job to pull the wire after running the conduit. Now days they use a material called "Mule tape" to pull the cable with. In the old days we used a grass bull rope of at least 1/2 inch. Nylon ropes will streach or snap. Not sure how these new climbing ropes would work.

Use the shop vac to suck a string, I use either a small sponge or something very light weight tied on the string. then pull in a smaller rope then larger rope. To pull the cable you might want to see if you can rent a Greenlee wire tugger. If you can support a roller above the conduit outlet you can use a pickup or backhoe to pull the rope. This would require several guys on the other end to handle the cables. Also you and buy some "wire soap" to apply on the cables as they feed it in to help it slide inside the the conduit. Do not try this length of run without some soap as there will to much friction and could damage the cables.

I know it requires a open trench but to do it as a one man job the easiest way is dig the trench then roll out the wire and slide the conduit on from one end and glue as you go. This would require many trips up and down the length of trench over uneven ground.

A backhoe sounds good as you already have one but the rental trenchers work real good as long as it is not one of those walk behind ones. The riders we used were quick and would go through rock driveways.

Either way its a big project so best of luck.