LOOONNNGGG Underground Cable Run

ch47dpilot · Aug 9, 2011

Cat driver, did you suck a bag through or just tied a bag tie to the string?

RickB · Aug 9, 2011

I'd be thinking more along the lines of two 45's at each end to make the pull easier than one 90, particularly at the entering end. The schedule 80 upgrade should include the last and first length in the trench, connected to the elbows. I'd also spend a lot more time getting info from the local utility that has to pull the cable than a bunch of semi-anonymous folks here.

husband_dad_engineer · Aug 11, 2011

I'll be doing this same project in a few weeks, going 2000' from the road to a pad mount transformer for a new house and barn. I dig the 48" deep trench and the rural electric company takes care of everything else (conduit, junctions boxes, etc.). Luckily, I'll mostly be going through top soil (northeast OK).

It'll run from the pole at the county road, along the north side of the driveway easement, but then what? I'll also be running water along the same length, with 1' horizontal and vertical separation requirements. I'll put the electric trench closest to the driveway and the water line trench just north of that.

My question is, I've got the choice where the transformer will be, just a minimum of 15' and maximum of 200' from the structures. Where should I put it? Should I stick it between the house and barn to minimize the secondary run or put it 100' or so away from everything?

cttractor · Aug 11, 2011

rjgarr said:
My question is, I've got the choice where the transformer will be, just a minimum of 15' and maximum of 200' from the structures. Where should I put it? Should I stick it between the house and barn to minimize the secondary run or put it 100' or so away from everything?

If it were I, I'd put it in your 100' away location or similar. Transformers sometimes explode or catch on fire. It doesn't happen every day, but it does happen and I've seen transformer fires on pole units and in underground vaults happen enough that I would never want a pad-mount unit too close to anything I truly care about. If you want to see what this looks like, go to YouTube and search for transformer fires -- you'll likely see and learn more than you really wanted to know. Yes, Virginia, there are some scary things out there...

Illini22 · Aug 11, 2011

Even thou they eliminated pcb oil along time ago, they still have over 50 gallons of oil. The primary gushing sometimes expand and blow out so keep it away from your well.

RickB · Aug 11, 2011

liledgy said:
Even thou they eliminated pcb oil along time ago, they still have over 50 gallons of oil. The primary gushing sometimes expand and blow out so keep it away from your well.

The transformers used around here to step down underground primary voltage aren't big enough to hold 50 gallons of oil even if the housings were filled with nothing else. That said, I'd be looking for 50'-75' of separation from the transformer to any structure.

jonyyuma · Aug 11, 2011

RickB said:
The transformers used around here to step down underground primary voltage aren't big enough to hold 50 gallons of oil even if the housings were filled with nothing else. That said, I'd be looking for 50'-75' of separation from the transformer to any structure.

Since Rick-B is semi/anonymous too. Transformers come in many types and sizes..not all are underground....I would just allow a good distance, from structures and wells.. Wire is not cheap, but please don't use Aluminum type. Many will try to save on the initial cost, it just is not worth the risk...And Yeah , a lot of the primarys are aluminum. So there is 2 more cents.

Illini22 · Aug 11, 2011

Id be surprised if their is any decent sized utility putting any thing but aluminum in the ground for underground residential distribution. When you get into downtown areas you will see some lead covered paper and some copper. I don't care for to many things at menards but their 4/0 with a 2/0 neutral direct bury wire is exactly what many, many utilities and municipalities put in the ground. Very tough plastic like insulation. If it doesn't get damaged by others (co.s digging nearby) it will outlast all of us. Oh, the 4/0 at my house was put on in 1978.
Putting aluminum inside your house is a whole different animal and am not advocating that.

Lineman North Florida · Aug 11, 2011

jonyyuma said:
Since Rick-B is semi/anonymous too. Transformers come in many types and sizes..not all are underground....I would just allow a good distance, from structures and wells.. Wire is not cheap, but please don't use Aluminum type. Many will try to save on the initial cost, it just is not worth the risk...And Yeah , a lot of the primarys are aluminum. So there is 2 more cents.

All new construction for primary distribution and transmission is aluminum or acsr which is aluminum with a steel strand, that's underground and overhead, all residential secondary services that are installed by power company's are gonna be aluminum, if it's a copper service it's probably commercial that has been paid for by the customer. Aluminum services are not as good as copper but if installed in conduit most have a life expectancy of over 30 years.

Illini22 · Aug 12, 2011

My service is33 years old and its direct bury. And it's considered a youngster around here. Com ed was putting it'd in the ground before They made padmount transfoers or pedestals. They would install a culvert upright, 3' out of the ground and put an overhead transformer in there with a cutout and put a roof over it. The sad thing is they are still being used, when we have a burn out it's just easier to remove and replace rather than upgrade. Instate of pedestals they have crab joints on the lot lines.
This construction is what they did in the mid to early 60's.