Electrical Conduit

[Beavers]

I haven't read up on electrical stuff, and I'm pretty clueless about it at the moment.  I figure I have plenty of time to learn before I get to the wiring stage on my house though.

While I have the mini-excavator rented to dig my footings I want to dig the trench for the water line, and would also like to put in conduit from the power pole to the house.  The run would be about 80'.  I tried using the link that Mountain Don posted for the conduit calculator, but I don't even know enough to make it work. 

What size/type of conduit should I get so that down the road either myself or the power company can run the wire to the house?

Thanks,
Beavers

BTW- The house will be the 14x24, with a future addition planned.  Also a shop/garage with power tools.  I have no idea what kind of loads, ect.  Not sure if that makes a difference on conduit size. 

[MountainDon]

I would start with asking the power company about this. They may very well have their own requirements, they may not, but no sense doing something that they won't approve. There may be a "standard" way of doing this but it's their power company and they can have their own rules. Sorry I wasn't more help than being a buck passer.

[muldoon]

To size, you would need to size the requirements.  If you intend to have 200 amp service at the pole (which is pretty common), you need to work out how power you want ran to your house.  I bought a 100amp subpanel for my use but power it via a 70amp two pole breaker in the pole.  That gives 70amp at 220 volts. (think 140amp at 110).   That equates out to plenty of power.  I used 2 20 amp 110 cirucuits, and 1 15 amp 110 circuit and have tons left over. 

The reason you need to size it because higher amps require thicker cable which then requires larger conduit.
70 amp wire is #4 wire
NEC ampacity chart http://www.affordable-solar.com/wire.charts.htm

220 service requires 4 wires, all THWN, the W is important and means it is ok in wet use - conduit is wet.

Then go to NEC conduit fill rate table
http://www.westernextralite.com/resources.asp?key=47

#4 wires - you can put 4 #4 wires in a 1 inch conduit, however the 1 1/4th gives you some added room. 

Hope this helps.

[lockman]

When I ran my underground lines, the power company had a sheet with requirements they gave me. It had to be 2.5" sch 40 conduit, 36" deep.... the sweeps at each end had to be sch 80. Also, I had to make sure there was a pull line in it.

[Beavers]

Thanks Guys!

I'll give the power company a call and see what their requirements are.

[davidj]

Then go to NEC conduit fill rate table
http://www.westernextralite.com/resources.asp?key=47

#4 wires - you can put 4 #4 wires in a 1 inch conduit, however the 1 1/4th gives you some added room.

I think that's for metal conduit - there are different, but similar, tables for PVC (which you're likely to be using if going underground).  Here's an (unverified) table for PVC:

http://www.jhlarson.com/ind_tables/fill/pvcfill.htm

I think it's still 4 x #4 in 1 inch schedule 40 PVC but the count is different for some of the other sizes and for schedule 80.

[muldoon]

Thanks Davidj, I didnt realize the distinction, just googled for the chart and posted the first hit that looked right.  It still comes out the same 4 in 1" and 7 in 1.25". 

Another few things to be sure of when you run that conduit.
1) It needs to be buried 18 inches deep. 
2) try to avoid any bends in the conduit, use sweeps if you need to.  no 90's for sure!
3) You can use schedule 40 pvc underground, however the piece that comes up from the ground needs to be schedule 80.  (Any piece of pvc conduit that is exposed to sunlight should be 80 for UV protection, it will last much longer.)
4) you cannot bury junction boxes or make splices underground.  The cable should be whole in the wet environment as that pvc may very well (likely) be filled with water from time to time. 
5) The ground wire does not need to be as heavy duty as the other conductors.  for example using #4 for the power, you can easily use #6 ground and possibly #8 ground. 
6) According to NEC, each building in a separate structure not connected by grounded pipe (hard pipe water line) should have an independant ground rod.  (Even tho you have a ground line running back to the pole, its apparently not the same).  Some electricians disagree with this and say it's not needed.  I personally do not have the expertise to know the right answer so choose to follow NEC. 

Those are some things to consider when you plan out your work.  I wish I had known them back on day one. 

[Redoverfarm]

Ours is similar to Lockman but they require at minimun 3" Sch 40 at 36".  Any other utility such as a telphone has to have a minimun of 12" seperation with a warning ribbon if buried in the same trench. 

[ballen]

North Eastern PA (Penelec) required 3" schedule 40 for a 3600 foot grid tie recently installed with 3 juction boxes along the way.  Luckily, the seller of the property paid for it:-)