LOOONNNGGG Underground Cable Run

[robiefield]

I've got a huge job coming up, and I could use advice on technique.

After years of petitioning, the Power Company has consented to provide electricity to my isolated acreage in the VA mountains.

I have agreed to trench 36" underground from my service drop location to the nearest power pole, and put in 3" conduit with pull rope so that when the Power Co comes, they only need to pull the main feed (600A) cable from the nearest pole to my service drop.

Here's what makes it interesting: This is not going to be like pulling Cat5 through 40-50 feet. It's going to be a 1500 foot-long distance. With BEEG honking cable. Power Co has to pull the cable (thank Dog) but what is the best way to set up rope to pull through 1500 feet of 3" schedule 40 electrical conduit in a trench?

How do the pros do this? In 30 50-foot segments? 15 100-foot segments? Clearly I can't get a 1500 foot rope (and if I could, can you imagine trying to pull a cable that big that far? Ay yi yi...)

If I want the PowerCo guys to be able to work uninterrupted, do I need 30 50-foot ropes? What seemed conceptually simple (how hard can it be, you thread rope through a 3" pipe) becomes not so simple when I get to the details.

Who's been there? What's the right way to do this (besides subbing the job out)? I'm all ears, friends. Can you help me figure this one out?

 

[moeh1]

Haven't pulled that far, so no help. I'd recommend you use schedule 80 conduit at each end where you come up, so you have less to worry about.

 

[robiefield]

Useful information: the 1500 foot run is for all practical purposes straight and can be accomplished using only 10 foot long straight electrical PVC conduit pipe.

Also am I correct in thinking that Sch 40 PVC Elec conduit (flared at one end, no connectors required) can be press fit when joined, or should I plan on gluing 150 junctions together during the process?

The PowerCo will pull the cable and do the connection work so I am not trying to play with electricity that I should not be fooling with. I am just a dyed-in-the wool DIY guy who isn't afraid of doing tedious dirty work in lieu of paying someone to do tedious dirty work. If I can understand the proper technique, I don't think I need 20 years of experience to thread a rope through empty 3" pipe a few feet at a time.

I *do* need the advice of someone with experience about what type and size of rope to use, and what lengths to use, and how to string together the individual segments, assuming that one 1500 foot rope pull is not realistically feasible.

I'm not the smartest guy in the world, but I learned to follow instructions pretty well in engineering school.

 

[robiefield]

I'd recommend you use schedule 80 conduit at each end where you come up, so you have less to worry about.

I can see the logic behind that. Sch 80 for the whole run would be breathtakingly expensive and overkill, but I can see where the 90 ells at each end (and possibly the single length of vertical conduit exiting the ground at each end) being Sch 80 making sense.

I'd imagine the 90 ells at each end would only be added after the long straight run has had the cable pulled through. No sense in making the job harder by putting the ells on until after the long haul is pulled.

I recollect Sch 40 and Sch 80 have common OD but Sch 80 is thicker and has a smaller ID than Sch 40. It makes me wonder if 3" Sch 80 ells would properly fit to a 3" Sch 40 run...

 

[RippySkippy]

snipped...

Also am I correct in thinking that Sch 40 PVC Elec conduit (flared at one end, no connectors required) can be press fit when joined, or should I plan on gluing 150 junctions together during the process?

I wouldn't take the risk of NOT gluing the joints, when the pipe is assembled on grade, then lowered into the trench, it will take no time at all to do it and do it correctly. One of the first calls I would make is to a electrical supply shop and see if you could locate 20' sticks...half the joints and fuss. Here's the Carlon part numbers...

... I learned to follow instructions pretty well....

I'm with ya.....

 

[RippySkippy]

... makes me wonder if 3" Sch 80 ells would properly fit to a 3" Sch 40 run...

Specs for fittings...

 

[Just Bill]

Why don't you have more poles set?
1/4 + mile is a long way to pull cable especially 600a.
I would prime and glue the joints to keep the water out.
Call the power company and ask what is needed.
Too small might be a wreck but too large would be a waste of money.

 

[Danno1]

.


How about putting pull boxes at 500 and 1000 feet? Rope comes in 600 ft rolls. Either that or learn how to splice rope.

Also, I think I'd check w the elco to see what size/type of rope they want to find in there.


.

 

[tcartwri]

If it's direct burial cable, you can use drainage pipe instead of 150 pieces of shedule 40.

Personally, I would find out what they specify for poles and have a seperate contractor put them in, with a transformer at your end.

 

[oldnslo]

Conduit comes in spools so there would be a lot less joints. My son worked for a directional boring company and they pulled up to 6" conduit in 500 ft lengths. Might want to do a little checking around with electrical supply houses etc. They also have rope/line made for pulling cable.

I would also check with your electrical company because here the code calls for steel elbows at both ends for that size wire.

Roy

 

[ch47dpilot]

first 1500' I'm assuming high voltage lines. May have to much of a voltage drop if it's 220. Second when you set up the conduit make sure male end is on the same end as the wire being pulled. I found if the wire goes from female end to male end it can get hung up but if you go from male to female it slides though. So you need to know if they plan to have the wire spool at your service drop or the pole.

 

[beppington]

I would think that if the power co has to pull the cable, they would be very specific as to what you must provide for them. That was my recent experience.

And, actually, my power co direct-buried (36" deep, with a trenching machine) their cable from the road-side power pole to the new transformer set near my future home site, about a 450' run.

However, before they began that, I was required to install a disconnect/ meter panel of very specific specs/ dimensions, with an empty 3" gray PVC conduit between the panel & the transformer, buried 36" deep, & with specific large-radius sweeps (24" I think it was), & with a pull string.

Now the distance from my new transformer to my disconnect/ meter panel is only about 10' ... but it surprises me that your power co wouldn't just direct-bury the cable from the road to your service drop.

 

[Gizmo2]

I would call the electric company also.
I also think...
Where the conduit comes out of the ground needs to be schedule 80.
Cable can not be run in conduit I think it has to be individual conductors.
I would plan on adding pull boxes.
You may need a tractor to pull the cable. A lot of friction in 1500 feet.

 

[HoustonBrama]

The Power company is not going to use your rope to pull the wires. What they will do is use your rope to pull THEIR rope the length of the pull. Then they will use thier rope to pull the wire. Your county code should dictate type of conduit you need.

 

[beppington]

The Power company is not going to use your rope to pull the wires. What they will do is use your rope to pull THEIR rope the length of the pull. Then they will use thier rope to pull the wire. Your county code should dictate type of conduit you need.

I would still call the power co ... & prob the county, too ... as they don't always agree perfectly, especially in an unusual situation; he said it took years of petitioning to get it OK'd. We're all just guessing here, & 1,500' is potentially a looonnnggg something needing to be replaced because of a guess.

 

[Bigkrank]

The Power company is not going to use your rope to pull the wires. What they will do is use your rope to pull THEIR rope the length of the pull. Then they will use thier rope to pull the wire. Your county code should dictate type of conduit you need.

Did it a couple times. Here they had me put twine string in the conduit and they used it to pull their rope thru. On the double 400 amp run I put it in 5" plastic drainage tile. The others were 3" plastic conduit & 4" drainage. 4" drainage tile is the norm around here unless it goes under a driveway. Thats also what the power company uses when they do it themselves.

 

[leonz]

I've got a huge job coming up, and I could use advice on technique.

After years of petitioning, the Power Company has consented to provide electricity to my isolated acreage in the VA mountains.

I have agreed to trench 36" underground from my service drop location to the nearest power pole, and put in 3" conduit with pull rope so that when the Power Co comes, they only need to pull the main feed (600A) cable from the nearest pole to my service drop.

Here's what makes it interesting: This is not going to be like pulling Cat5 through 40-50 feet. It's going to be a 1500 foot-long distance. With BEEG honking cable. Power Co has to pull the cable (thank Dog) but what is the best way to set up rope to pull through 1500 feet of 3" schedule 40 electrical conduit in a trench?


How do the pros do this? In 30 50-foot segments? 15 100-foot segments? Clearly I can't get a 1500 foot rope (and if I could, can you imagine trying to pull a cable that big that far? Ay yi yi...)

If I want the PowerCo guys to be able to work uninterrupted, do I need 30 50-foot ropes? What seemed conceptually simple (how hard can it be, you thread rope through a 3" pipe) becomes not so simple when I get to the details.

Who's been there? What's the right way to do this (besides subbing the job out)? I'm all ears, friends. Can you help me figure this one out?

Before this snake gets out of hand you are going to have to rethink the entire issue!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!

You will need a 600 foot spool of pulling rope and a cable puller if you can rent one as they will charge you for it anyway.

Assuming you will be coming down from 4,000 volts single
phase to 220 volts single phase.

1/0 gauge or 2/0 guage 600 amphere feeder line wire with ground.



A three wire strand with 2 insulated conductors for the hot and neutral legs and a bare aluminum coated copper ground cable as line wire number three.


At the least you will need three junctions at 500 foot intervals to pull the 3 wire feeder cable.

The trench will have to be widened to allow room for the winch and the labor
at the junctions.

You also have to leave the trench open for the inspector before and after the pulling job is done.


You will either have to have/own a 600 foot wire tape or hire a contractor that can fire a projectile/ pipe ball throught the conduit to the open end at 500 feet to allow pulling a wire tape after the ball pulls the nylon twine through and then a cable pulling rope and then a Kellums clamp to secure the wire bundle in the conduit to pull it through.(also known as a chinese finger puzzle)

You will also need a substantial amount of cable lubricant being 5 to ten gallons or more in pails to do this as well as the smallest amount of damage on the insulation jacket will affect the cables ability for winching.


Your looking at 20.9 percent voltage drop with a 600 volt 100 amp circuit alone!!!!!!!


I think you should seriously think about having a transformer and a few poles added to this mess to avoid the line drop issues.

Otherwise the only economical method is high amperage locomotive sized storage batteries from DEKA and a generator with or without solar panels which will cost you less money to begin with.

 

[wrooster]

I would prime and glue the joints to keep the water out.

You can prime and glue those joints to NASA-grade perfection but the conduit is still going to fill with water. Due to the ground temperature, the air in the conduit is cooler than the ambient air. The result is condensation. Ask any electrician who has installed conduit and come back two months later to pull the wire... for this reason, the NEC classifies buried conduit as a "wet location", and accordingly you need to employ water resistant wire (e.g. THWN/THWN-2).

Wrooster

 

[jonyyuma]

This is a pole job, don't understand why it is not overhead. None of this practical, are you using 480 volts? Don't understand your power co saying this is okay. Voltage drop is going to be a problem, and you sure don't want a cable fault. The price of the wire???

 

[hr3]

Before this snake gets out of hand you are going to have to rethink the entire issue!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!! !!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!

You will need a 600 foot spool of pulling rope and a cable puller if you can rent one as they will charge you for it anyway.

Assuming you will be coming down from 4,000 volts single
phase to 220 volts single phase.

1/0 gauge or 2/0 guage 600 amphere feeder line wire with ground.



A three wire strand with 2 insulated conductors for the hot and neutral legs and a bare aluminum coated copper ground cable as line wire number three.


At the least you will need three junctions at 500 foot intervals to pull the 3 wire feeder cable.

The trench will have to be widened to allow room for the winch and the labor
at the junctions.

You also have to leave the trench open for the inspector before and after the pulling job is done.


You will either have to have/own a 600 foot wire tape or hire a contractor that can fire a projectile/ pipe ball throught the conduit to the open end at 500 feet to allow pulling a wire tape after the ball pulls the nylon twine through and then a cable pulling rope and then a Kellums clamp to secure the wire bundle in the conduit to pull it through.(also known as a chinese finger puzzle)

You will also need a substantial amount of cable lubricant being 5 to ten gallons or more in pails to do this as well as the smallest amount of damage on the insulation jacket will affect the cables ability for winching.


Your looking at 20.9 percent voltage drop with a 600 volt 100 amp circuit alone!!!!!!!


I think you should seriously think about having a transformer and a few poles added to this mess to avoid the line drop issues.

Otherwise the only economical method is high amperage locomotive sized storage batteries from DEKA and a generator with or without solar panels which will cost you less money to begin with.

:confused2:.. Go to your local utility that is going to do the work and "ASK" what they want and what they are planning to supply,, Some of the infomation here is going to out in left field somewhere,,