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Underground Elec - direct-burial vs in conduit
I am trying to figure out how I want to approach bringing 1700 ft. of primary elec. cable from the road back to a transformer-box near my house. I have talked w/ a reputable electrician who has recommended direct-burial rather than encasing the wire in conduit. He says that as long as you do not have stoney soil, (which I dont) that this is the way to go. Much less money and easier to install. He also said that if there ever is a break in the wire, it is much easier to detect, and fix if it is not in conduit. Anyone have any thoughts/opinions on this?
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Underground Elec - direct-burial vs in conduit
When I ran 400' of wire to my barn for my 220V welder, the electrician I asked said that to be to code it was supposed to be in conduit. However, he said that taking the situation into consideration (on my own property; I would know not to dig near it, etc) that he would use direct burial (UF) wire. That is what I used and haven't had any problems. The outer insulation on that stuff is really tough.
Good luck,
Bill
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Underground Elec - direct-burial vs in conduit
When I built my house last year I had to run 800ft undergroud from the main line to a transformer in my yard a 10,00 volt line. The power company laid the line and just rolled it off the reel right into the ditch no conduit. Do not know what kind of wire it was about 5in in diameter. They did the same with the line from the transformer to the house panel 220v just rolled it off and buried it.
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Underground Elec - direct-burial vs in conduit
Back a while for my entrance, I was instructed that via conduit, the depth of the dig could be less at 18" vs 24" for direct burial. Further regarding stones, DB required 6" of clean sand top and bottom. Just my .02 worth.
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Underground Elec - direct-burial vs in conduit
Conduit will allow you to pull the cable out and replace it. IF THERE EVER is a problem which in most cases is unlikely.
Bury a blank empty conduit also. You never know what you may want to pull thru it later. ( Fiber, cable, TV etc)
A extra conduit should not break the bank and will save you time money and digging up the yard in the future
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Underground Elec - direct-burial vs in conduit
Our local utility company (PSNH) had details on-line which required conduit for our 550' pull to our transformer. From that point we elected to place the meter near the transformer (i.e. not on house) and continue with a 140' pull & conduit into the house.
The utility inspected the conduit in-place before backfilling. So its probably up to the electric utility re: direct burial. I'd say go with conduit and maybe 1 or 2 intermediate pull-boxes.
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Underground Elec - direct-burial vs in conduit
For my house (1100 feet off the road) we dug a 4ft. deep trench, laid the electric line in the bottom, backfilled about 9" or so, and then laid the water pipe. It took some work to make sure everything was leveled out, but it seemed to work well. Personally, I wouldn't waste time or money with conduit.
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Underground Elec - direct-burial vs in conduit
Jim Brown,
What kind of armor was on that MV line?
I've installed conduit many times for medium or high voltage lines and in every case, they encased it in red concrete, so as to warn/protect future backhoe operators (or whoever) that might come in contact with it...That higher voltage stuff is extremely dangerous and will destroy anything or anyone who gets a hold of it...It doesn't just shock / kill you, it literally 'blows you up' !!!
Never heard of 10kv though (usually it was 4160, 16kv, 34.5kv, etc), so maybe they got something different going on where you're at..
As to which I'd go with...it would depend on the distance....in conduit, it's easier to replace, but direct burial can be 'repaired'....
At 1700 feet, repair would be much cheaper than replacement, I would think...Usually if there is a fault in UG cable, they will disconnect it, and hook up a signal generator to one end...then they can follow the cable from above ground using a detector (looks like a metal detector). HWere the signal stops, is your fault...You dig it up and then they make these special splicing kits, which include these molds which you fill with expoxy to create an unimpeachable container for the splice...
There are also test devices that allow you to hook up to one end, and they will tell you the distance from that end to the fault, but you have to know the exact path of the cable to make that info useful..
So for runs of a couple hundred feet or less, I would lean towards conduit, but anything longer, I would go the Direct Burial route....
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Underground Elec - direct-burial vs in conduit
There was heavy hard rubber insulation on the outside of all the strands that each had their own heavy insulation. Our local electric company put it in...maybe all "codes" are not like they are here in rural southern Indiana however. I know that property inside city limits have higher standards than in the country, even here.
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Underground Elec - direct-burial vs in conduit
MacDaddy,
1700 ft is too long to run secondary, 120/240 volts. The utility company will install primary conductor to a stepdown transformer. This is not an installation for the property owner, however, the utility may require or allow the property owner to dig the trench. Normally, this will be 30" to 36" deep.
If its an option I would strongly recommend installation in conduit, PVC schedule 40 is normally used. Concrete encasement is overkill, except under pavement. A red caution tape will be installed about 12" above the conduit.
Primary electric cable doesn't just break. Problems are created by animals, trees, humans on backholes, and lightning.
Normal primary phase to ground voltages are 2400, 4800, 7200 & 7620 volts. The three phase voltage is 4160, 8320, 12470, & 13,200, respectivity. Some RECC's use a 14KV phase to ground voltage, but its not as common as the others. Also, most utilities are or have phased out the 2400/4160 voltage.
Hopes this helps and isn't too late. Dave
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