Underground Electrical Service Question

horse7 · Jul 10, 2010

Many years ago when I put in my meter, there was no specification on having a slip joint or other means for ameliorating the effects of heave. So I mounted the meter (which comes up by itself between the ground mounted transformer and the house) on a plate with machined vertical slots, having lags going through the slots to the mounting wood. Basically I figured I needed something and rolled my own. Now they have codes to cover the potential problem.

The slots are only 2-3" long, and I've had to remount the lags a couple of times between heave and settling of the 5' deep trench.

If I had to do the underground over again, the one thing I'd do is check different secondary conductors, one brand of 4/0 was way stiffer than the other brand, causing a lot of extra effort for installation. I had figured they'd all be about the same... one brand worked reasonably easily in 2" LBs, other one was a PITA (with a mallet) [used sweeps outside, but inside needed LBs to drop to the distribution panels.].

captaincrab55 · Jul 10, 2010

Raspy said:
My utility wanted a pull rope installed and some even want the official thing (can't remember the name) pulled through to prove the conduit is clear.
.

Mandrel is the word for today, that is if I spelled it right....

Raspy · Jul 10, 2010

Captain,

Yeah, I think that's it. Thanks.

A short cable with eyes on each end and a few very thick flat washers in the middle.

Sheesh, brain fade.

John

captaincrab55 · Jul 11, 2010

Raspy said:
Captain,

Yeah, I think that's it. Thanks.

A short cable with eyes on each end and a few very thick flat washers in the middle.

Sheesh, brain fade.

John

John, Your quite welcome... I can't get the word "Mandrel" out of my mind, after running a job installing a several new underground services for a Hospital in Annapolis, Maryland... Power Co. required a mandrel to be pulled in all PVC conduit.. Installed about 15,000' of 6" PVC conduit and pulled a 6" mandrel in all the conduit...

crazyal · Jul 11, 2010

Wow things are different from state to state. I had to run 1400' of service line to the meter then another 350' from the meter to the house. In Vermont (or maybe it was a power company requirement) the service line had to have a vault every 600'. I could do the trenching and install the 2 1/2" conduit but they provided and installed the cable. they also installed a transformer on top of the last vault and ran the wire to the meter.

From the meter the power company no longer cared. In VT there is no inspection so you can do what you want from the meter on but when you go to sell the house if it's not to code good luck. I figured it out on my own but a good friend is an electrician so before I did anything. For me, 200 amp service and a run of over 300' 4/0 alum is not thick enough so I had to go with mcm350 (it's been a few years so I could be off a little). But I think code was the outside diameter of cable could only be 40% of the inside diameter of the conduit so I had to use 3". I also had to use slip joints everywhere the conduit penetrated the ground where it could freeze. Since the conduit comes into the house through my cellar slab I didn't need one there but everywhere else I did. I think my buddy said the 40% rule was to allow the wire to move inside the conduit to compensate for the frost movement.

The service line to the meter had to be 3' down and if anything else was to be buried in the same trench it had to be at least 1 foot apart. It was either 1' or 2' down there needed to be a red "warning powerline" tape buried into the hole. On the house side it only had to be 2' down.

I would go to a local electrical supply shop (not Lowes) and ask. They may be able to help you or know of an electrician who will give you answers for a reasonable price (I doubt you'll find free unless you know one).

crazyal · Jul 11, 2010

I would also note the 90s, or sweeps come in two styles. There are tight or sharp bends and then a more gradual style. If I remember correctly I couldn't use the sharp bends, something about pulling cable through them.

Again I did my house and just recently my garage myself but would recommend you talk to a pro. There are rules of thumb as to what size wire you need for the service load you are installing all over the internet but the correct way is to figure it out with max current vs distance. Doing it wrong, even if no inspection is required, could prove very costly even if it's able to handle the load you put on it without a problem.