wire size 100a service 500' from 200a main

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Old 11-20-08, 02:04 PM
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wire size 100a service 500' from 200a main

Hello all,
I want to run a 100A service to a cabin from my shop. The shop has 200A service. I plan to install a 100A breaker in the shop panel, go through the wall to the outside in conduit, continuing in conduit 3' below ground to the cabin where the conduit goes through the wall to a 100A panel. The total run from panel to panel is 500 feet. My question is what size wire and conduit should I use? I will use aluminimum because the present economy prevents me from mortgaging my shop to buy copper. Thanks for your help
 
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Old 11-20-08, 02:20 PM
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The minimum conduit size is 2", but 2-1/2" or 3" will be a lot easier to pull given the really long distance. You should check around at the supply houses for underground duct which is a continuous HDPE pipe on a roll so you don't have to glue 50 lengths of rigid conduit.

I would recommend #4/0 aluminum conductors for the hot, hot, neutral wires and #4 aluminum for the ground wire.

This provides you a 3.5% voltage drop at full load which is just outside of the 3% tolerance, but not worth jumping up to the next wire size 250 kcmil.

Hopefully your run is a bit under 500' so you can buy your wire on 500' spools.

A pull this long would be handy to have someone with underground pulling experience around. The 500' of 4/0 conductors puts quite a bit of tension on the pull line, plus the spools will be pretty heavy to move around and handle -- each one will be about 150 lbs.
 
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Old 11-20-08, 03:42 PM
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If your going bury it down 3' why not use direct burial wire? No pulling needed. Save money on the pipe to boot! You will just need some pipe for the two ends.
 
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Old 11-20-08, 04:34 PM
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Hello

You'll likely have a difficult time making such a long pull in conduit. You may need to consider a handhole especially if you plan to make turns. Set the reels in the middle and pull both ways. You may need to rent a tugger. There seems to be some downward price pressure on copper right now. So you may want to shop around and see whether you can get a better price. Im addition to the big box stores, I think Greybar will sell retail. You could check with them. Southwire has a handy calculator to use. Here's a link and a link for handholes to show you what I mean.

Voltage Drop Calculator

HandHole.com
 
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Old 11-20-08, 05:43 PM
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I would offer to help you pull that 4/0, but I'm sure I will be busy that day!
 
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Old 11-20-08, 06:20 PM
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Originally Posted by Bill190 View Post
I would offer to help you pull that 4/0, but I'm sure I will be busy that day!
Did I forget to mention my bad back? I also have a bad front too.
 
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Old 11-20-08, 07:19 PM
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I thinks it's worth asking how big your cabin is, square foot wise. What kind of loads will you have in the cabin? Range? Hot water tank? Dryer? Electric heat? If none or only one or two of these mentioned are or ever will be in the cabin, you might want to consider a smaller service. 500 feet is a long way and that's a lot of big cable if all you have a rustic bachelor type cabin for the inlaws to sleep in when they're in town. If you have a wood stove, an outhouse and a bbq, (where I live you see a lot of these) and there's no plan to build again or upgrade, you might only need a few 15 amp ccts. Even a 60 amp service will handle a fully functional bachelor suite. Maybe you've thought about this already, your post didn't mention though. Think about it before you buy. Take care, sid.
 
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Old 11-20-08, 07:55 PM
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I was thinking about the 100 amp breaker at the house panel and connecting 4/0 to this. I can picture wrestling with that wire and trying to get it to bend sideways into a breaker.

Do they make 100 amp breakers with 4/0 lugs?

And if not, what would be the best way to do this?

Use an al/cu splicer reducer lug and connect to the largest copper wire the breaker would accept?

Use a separate box for this?
 
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Old 11-20-08, 08:18 PM
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Yeah there is a way to reduce the conductor to fit in 100 amp breakers.




This item above is what we used on connecting diffrent size conductor and make sure you make a note in case someone else get a funny idea with this.

Oh yeah .,, you will need 10X18X6 [ H X W X D ] " pull " box it will come either NEMA 1 ( Indoor useage only ) or NEMA 3R ( can used either indoor or outdoor ) or 4X { this will cost a bit more but dang tough one }

Merci,Marc
 
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Old 11-21-08, 07:52 AM
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I recommend installing a few in-ground electrical boxes to help make pulling the wire easier.
 
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Old 11-21-08, 09:39 AM
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Actually saw an electrician on "This Old House" tie the pill rope to his pickup truck to pull the cable. Of course this also involved five gallon buckets of lube and a guy applying it. as the cable entered the conduit.
 
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Old 11-21-08, 02:35 PM
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Another few points to mention: You will need to get a rope in the pipe for the pull. That will need to be long enough for the entire pull (500'). The conduit will have to be complete before you pull in the wire. I would suggest using steel 90 degree elbows because the PVC will burn through from the rope and wire. I just want to say it again, use direct burial wire.
 
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Old 11-30-08, 09:13 AM
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Hi All and thanks for your responses! Lots of very good info there! Some additional details I did not post in the question (minimize confusion) are: I plan to use 4" courragated drain pipe (250' coils) for conduit, blow the string through with a plastic baseball and compressed air, pull the rope with the string, pull the wire AND a 1" water line with the rope. To prevent the edges of the wire and pipe from catching the courragations the rope will go through the bottom center of a 1 liter pop bottle to act as a shield over the head of the pull. All of this will be done on level ground, flex pipe tied to trees, pull rope tied to Bill190's pickup truck (actually am using 12volt winch). After the pull is complete the assembly will be drug across the ravine to BESIDE its final resting place. Then the track trencher does it's thing and the assembly pushed in and buried. I am considering building a second assembly consisting of cat5 wire, co-ax for tv,1" natural gas line, and 2 1" pex tubing lines (hot water heat) to put in the ditch with with the first but I think the cat5 and co-ax would be too close to the 4/0 and pick up interference. Well I have gone on long enough... Any thoughts?
 
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Old 11-30-08, 10:48 AM
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Corrugated drain pipe is not a listed raceway for electrical wire. It would not be legal to us it in such a manner.

You could skip putting the wire in it and just put the wire in the bottom of the trench direct burial. (I forgot if I mentioned direct burial or not )
 
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Old 12-01-08, 11:33 AM
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Originally Posted by xbank View Post
I plan to use 4" courragated drain pipe (250' coils) for conduit
Drain pipe is not a legal electrical raceway unless you use direct-burial conductors. You would need to use electrical HDPE duct, PVC conduit or direct burial conductors for the power. The other utilities may be okay in corrugated drain pipe.

Consider a tiered utility trench 4' deep. Water line at the bottom (depending on local frost line depth), backfill 12", direct burial electrical conductors at 3' deep, backfill 12", gas line 24" deep, backfill 12", phone, tv, cat 5 in conduit or direct burial at 12" deep. Gas line may require a separate trench, contact your gas company.

cat5 wire, co-ax for tv
You can't put low voltage cable in the same raceway as high voltage cable so you'll need another plan there. Also, maximum spec distance for ethernet on the cat5 is 100 meters (330 feet), so you might run into trouble without a powered repeater; it can work at that distance with quality cables and gear and no interference. Coax for cable TV would probably need a powered signal amplifier.

1" natural gas line
Contact your gas company for gas code in your area. You almost certainly can't bury it with the electrical wires, and it will need to be an approved material (usually yellow polyethylene pipe with welded terminations and protection sleeves on the ends) and have a tracer wire buried above, but not touching the line.

2 1" pex tubing lines (hot water heat)
Wouldn't you loose a heck of a lot of heat in the 500' trench? Have you thought about putting a boiler in the outbuilding or some other heat source utilizing the natural gas line?
 
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Old 12-02-08, 09:21 AM
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I like the tieried idea! The PEX tubing will still be in the corrugated pipe because it will be insulated between the ditch and the pipe. In fact that is what started this whole thing. Running the PEX over 500' in an insulated pipe is more cost effective than a second boiler both in the initial cost and monthly cost (efficiancy of 1 unit over 2). I have always planned to use direct burial wire just felt it would be better off inside the corrugated pipe. Do you suppose I could run the water line and the 4/0 in with the PEX? A frozen water line would no longer be a issue, but is it important that direct burial wire be in contact with the earth? You also mentioned using quality cable and no interferance with the cat 5 and co-ax. What would you recommend for the cat 5 and co-ax? Do you also have a feel for how far apart I need to keep the 4/0 away to minimize the interferance? Perhaps I should dig a second trench for the gas line, cat 5, and coax. This is a great site! You guys are a lot of help and you don't make me feel stupid like my brother does! Thanks for your support! Mark
 
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Old 12-02-08, 10:11 AM
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Originally Posted by xbank View Post
The PEX tubing will still be in the corrugated pipe because it will be insulated between the ditch and the pipe.
Is there some sort of foam or other insulation material on the PEX tube to prevent heat loss? It just seems to me like you'll be wasting an awful lot of energy heating up the soil and you might have cold water coming out of the end of the pipe.

In fact that is what started this whole thing. Running the PEX over 500' in an insulated pipe is more cost effective
How did you calculate heat loss to the soil?

than a second boiler both in the initial cost and monthly cost (efficiancy of 1 unit over 2).
What about natural gas fired forced air in the outbuilding or ceiling mounted nat. gas heater(s)? Or really save in installation costs and go with no PEX, no gas line and use electric baseboard and/or radiant heaters.

Do you suppose I could run the water line and the 4/0 in with the PEX?
I'd keep the power conductors by themselves.

What would you recommend for the cat 5 and co-ax?
You can get both with underground ratings -- some electrical supply houses carry them nowadays, or I'm sure you can buy online somewhere. It wouldn't be a terrible idea to put the low voltage stuff in a pipe of some sort so you can pull new if needed or when technology improves. Any type of pipe is okay, it doesn't need to be rated conduit.

Do you also have a feel for how far apart I need to keep the 4/0 away to minimize the interferance?
The rule of thumb is 12", and only cross data and power cables at right angles if possible.

Perhaps I should dig a second trench for the gas line, cat 5, and coax.
You might need to with the gas line -- some gas companies require dedicated trench for just the gas, or at least X inches of separation between gas and any other utility.

How deep can your trenching machine go? Did you plan to also run potable water and septic or will there be no bathroom in the shop?
 
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Old 09-01-09, 07:13 AM
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Just an update. I opted to run 2 trenches. 1 with the 4/0 the other with gas, cat5, and coax. I am running 2 boilers instead of the PEX underground. Again many thanks for all of the viewpoints!
 
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Old 09-01-09, 08:12 AM
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Thanks for the update. It's nice to know how the projects came out. Glad everything worked out, and I hope you're enjoying the cabin.
 
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