Main electric service line too long?

[LarryRB]

this coming spring I will do underground electric for the sister in law.. I already got the permit from the electric company.. Here, on the Ma/Ct state lines, 4" schedule 40 is required for any run 200 ft or longer, and at 42" down minimum.. Anything less, only causes aggravation later. I do a lot of trenching for underground electric and never once saw anything below the sch40/4,even on very short runs,,,

 

[Woodzy]

When I built my home shop in Michigan I called to get thier opinion. I'm about 450 feet off the road and they recommended that they set four poles, install a transformer, and then run underground from the pole to the barn. I've heard horror stories about cost of setting poles & long run but I was only charged for the cost to go from the last pole to the barn. It was around $52.00. Seemed like a bargin to me. They showed up and had it all finished in about 6 hours. Now if I ever build a house, I can run off both the same tranformer - plenty of power!!!.

 

[ktm250rider]

</font><font color="blue" class="small">( My electrician is going to thread 10' lengths of pvc conduit 2 1/2" in diameter onto the 4-ought wire, and then glue them together. )</font>
I would NOT do that. The glue and primer can deteriorate the cable sheathing and cause major problems. Run the conduit first, then pull the wire.
Dont do what I did, and only run half of the conduit. I ran out of time and had to back fill my trench so I could continue work on the house. Well after the 20" of rain in NH the past couple of weeks, I now have to find a way to get the water out of my conduit. The trench was completely full of water.

 

[woodlot]

All conduit will eventually fill with water, its inevitable. I wouldn't worry about it.

 

[ericbx1500]

My electrician is going to thread 10' lengths of pvc conduit 2 1/2" in diameter onto the 4-ought wire, and then glue them together. )



as others have said just dont get sloppy with the glue. I did mine this way. I only ran 8 guage 130' by myself.

 

[MikeD74T]

I've had good luck pulling water from buried conduit by pushing in a garden hose and sucking the water thru it with a wet vac. often a wet vac won't lift a column of water through the full size vacuum hose but will through the smaller garden hose. And you don't want to buy 100' of 2" vacuum hose.

 

[flusher]

I had about 400' of 230V/200A service installed last Aug for my new house.
I dug the trench (4"W x 24"D) with a rented Ditch Witch and my electrical contractor installed 2"ID Schedule 80 PVC conduit in the trench.
I used my B7510HST/LA302 FEL to push soil in the first 30 ft at each end of the trench to keep the conduit from jumping out of the trench when the cables were pulled.
He used an electric winch (stuck into the 3" receiver hitch of his truck) to pull two 4/0 copper hot lines and one 2/0 copper neutral. The three cables were pulled together and that part of the job took less than an hour once he started pulling.
He hammered 10' ground rods into the soil at the ends of the trench. He did the entire job in about 8 hours over two days.

 

[BobRip]

If the AC has a running current of 30 amps it can pull 3 to 6 times that current when starting. That's up to 180 amps. You will notice this!

I would be worried about an electrician who wants to thread the conduit on. One of the purposes of conduit is for easy removal of damaged wire. You could not do that with the proposed conduit size.

Bob Rip

 

[GaryBDavis]

I’ve got a similar installation planned. I’ve got my 320Amp meter base and two 200Amp mains laid out on the shop table and wiring them now. I’m going to place the meter loop half way between the shop and house. The underground runs to the house and shop will be about 100 to 125 feet each. I’ll put in 2 inch conduit and 3/0 cable.

I’ve done quite a few installations, but not one exactly like this and the grounding scheme comes to mind. Since the 200Amp mains, which are mounted on unistrut beside the meter base and utility pole, have breaker slots for the well house, gate, etc, I’ll need a ground rod at the pole where they are installed. I’ll run ground wires from each main panel and the meter base to a ¾”x8’ ground rod as required by the electric company. However, for the house and shop, I’m planning on each of them having a separate ground rod. I know I can’t tie the grounds together unless I bury bare solid wire in the trench outside the conduit. I guess my question is “Is this the desired grounding scheme?” I’m using isolated ground bus bars at each of the three locations.

One last note is my generator hook up. I’ll have to post pictures of it when I’m done. I’ve got a Midwest generator inlet box that has a cool angled inlet plug and a “in use” 3R cover. I’m using Square D QO series mains and their Generator Interlock Kits which allow me to use a double pole 50amp feedback breaker. These kits allow you to turn on only one of the two breakers – the main or the feedback. Both of the feedback breakers are tied to the generator inlet. That part of the setup looks pretty good.

 

[jimgerken]

I guess I am baffled. Why would you use conduit? Around here, code is apparently to use wires suitable for direct burial. I have seen even the high-voltage runs done this way (no conduit, just the wires in a trench). Why are you all putting down conduit? /forums/images/graemlins/confused.gif

 

[BobReeves]

I ran conduit from the meter to the house and shop (both 150 ft runs) for two reasons. If ever need to replace the wire I can do it without trenching and conduit doesn't need to be buried as deep. For the price of 2 inch PVC it was an easy decision. The funny part is I have direct burial cable in the conduit.

 

[LarryRB]

</font><font color="blue" class="small">( I guess I am baffled. Why would you use conduit? Around here, code is apparently to use wires suitable for direct burial. I have seen even the high-voltage runs done this way (no conduit, just the wires in a trench). Why are you all putting down conduit? /forums/images/graemlins/confused.gif )</font>
For one, it is our code that schedule 40 be used. Second, we have a gazillion rocks and boulders that constantly work their way upwards from underground, and that is the reason for piping...

 

[rswyan]

</font><font color="blue" class="small">( The funny part is I have direct burial cable in the conduit. )</font>
I'm doing the same thing - 2" schedule 40 PVC with 4/0 4/0 2/0 URD.

For me the big advantage will be not having to bury it so deep - I have to cross 1 culvert and a pair of french drain lines, all of which are buried fairly close to the surface.

 

[GaryBDavis]

Okay, I need to make sure I understand the 4/0 for the lines and 2/0 for the neutral. I’ve heard that the NEC allows you to use a neutral that is two sizes smaller than the lines. I’m guessing this applies only to main feeds for 240V single phase.

I’ve always run the same size neutral as it stands to reason that you have as much current going through the line as you do through the neutral - for 120V circuits that is. I’m guessing that the reason they let you run a smaller neutral is because the loads are supposed to be fairly balanced load between the two 120V lines. Since they are 180 degrees out of phase, their currents cancel out on the neutral line. The 220V circuits don’t even use the neutral.

Is this right or is there another reason?

 

[BobReeves]

I agree the nutral doesn't need to be any larger than the feed lines. The nutral only sees(carries) one phase at any given time.

 

[rswyan]

Gary,

I can't comment on your questions regarding the reduced neutral - it sounds good to me - but then I'm not an electrician and have limited knowledge in the area .... where's Inspector507 when you need him .... ? /forums/images/graemlins/grin.gif

I'm just operating off what I was told would work for my particular situation.

 

[midlf]

correct. some balance between the two legs is assumed thus allowing for a reduced neutral. If you have a situation where you know this not true then a larger neutral is needed. Very unlikely in a residential type situation.