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Country Discussion Topics
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230' of electrical
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Chris Mainka    Posted 02-08-2004 at 14:28:40       [Reply]  [Send Email]
Hi Everyone - I went and measured the distance to my barn and way overestimated the distance. Its only 230' to the barn. If I run 70 amps to the barn at this distance can some one tell me what size to run.

Thanks Chris


basod    Posted 02-19-2004 at 22:17:25       [Reply]  [Send Email]
If you want to find out what cable to use and don't have the fancy calculator its relatively simple calculations. Every conductor has a resistance (R) usually measured in ohms/100ft. I use my Ugly's electrical reference book to find the resistance but NEC may publish something online, or electrical supplier can provide you with it. Getting to the math though, the principle resides in the sum of the rises equals the sum of the drops (goes ins=goes outs). I'd guess you're running a 220volt supply w/70amp main. To make it easy we'll say you're conductor has 0.2ohms resistance/100ft. Ohm's Law V=I*R the voltage drop for 230ft is 230ft/100ft=2.3, 2.3*0.2ohms=0.46ohms of resistance. Then 70A*0.46=32.2volts, so you'll have a voltage drop of 32.2 volts over the run resulting in a terminal voltage of supply-drop.or
220-32.2=187.8V and to find what your equivalent nominal 120V rating would be (one hot and the nuetral) divide the 220V rating by the sqaure root of 3 or 1.732 so for a true 220V circuit 220/1.732= 127V or in the case of the 230Ft run 187.8/1.732=108V It'll make your lights burn a little dimmer but horsepower rating on motors are reduced and welders will try to draw more current to achieve the same Kw output resulting in frequenlty tripped breakers.


basod    Posted 02-19-2004 at 22:17:59       [Reply]  [No Email]



Willy-N    Posted 02-08-2004 at 18:09:53       [Reply]  [No Email]
My run to my barn was 420 ft and I used 2/0, 2/0, #1 alum for it to feed my 100 amp panel. I figure I can run a welder at 50 amps no problem if I wanted to. Right now it is for the lights, stock tank heater and a reffer in the tack room. Works great. Ran it underground direct burial cable. Mark H.


Willy-N    Posted 02-08-2004 at 15:36:11       [Reply]  [No Email]
You will need 2/0, 2/0, #1 alum and that will give you a maxium of 4.4 volt drop with a 70 amp load and you will be with in code requirements. If you wanted to use copper it would be #1, #1, #4 and that would give you a 4.2 volt drop on the same load. The alum is cheaper to use. Mark H.


Lazy Al    Posted 02-08-2004 at 15:14:45       [Reply]  [No Email]
Mark's got that little calulator that tells you that . What I wanted to add is if you do run it in PVC put steel 90's in because the rope that you pull the wire in with will burn a groove in a PVC 90 then you'll have a mess that way .
Al


Chris Mainka    Posted 02-08-2004 at 16:49:11       [Reply]  [Send Email]
Thanks for all your help guys - and Mark that is one great calculator.


Willy-N    Posted 02-08-2004 at 18:03:15       [Reply]  [No Email]
Paid $180.00 for it when they first came out. It has a lot of formulas other than Math, it is like a small electrical computer. Mark H.


toolman    Posted 02-08-2004 at 16:28:21       [Reply]  [No Email]
why don,t you just get direct burial and a load of sand , save messing around with that condiut.


LesWV    Posted 02-08-2004 at 17:59:11       [Reply]  [Send Email]
To bad that the NEC Article 310 will not approve #1 Super Flex "BLACK" Copper Welding Cable can not be used to run Branch service. For a 250' coil can be gotten for around $220.00 or .87 cents a per foot and #4 sales for $125.00 for 250' or .50 cent per foot.
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Just to add a small tip from my CATV conctrating days when dealing with new construction.

Dig your ditch.

Pull your cables and lay them on the ground from the starting point to the end point.

Lay out the (in your case) SCH 80 conduit.

1/4" rope attached to a stick such as a broom stick. Or two 1/2" PVC pipe coupled together.

If your wire comes on or can be placed on a reel (water hose reel) the next part will be no sweat.

Start with the longest straight run.
Slide the 1/4" rope through the first piece of conduit. Pull the wire through. Go to the second piece of conduit and do the same. Continue until you have the wire running through the entire lenght of all the straight conduit pieces.

When you come to the risers.
Slip the 90 over the wire. Then down into place on the conduit.

Once everything is fitted and in place the way that you want it.

Glue or press the SCH 80 peices together.

Place it in the ditch a bury.

Putting the wiring through one piece of conduit at a time sure beats the heck and mess out of tring to pull it for the entire 250' lenght and through two or three 90's.



basod    Posted 02-19-2004 at 22:37:25       [Reply]  [No Email]
wire lube it was invented for a reason. and laying conduit does not have to be so time consuming. buy conduit big enough to stick a ping-pong ball in. Tie a string through a small hole in the ball and blow the ball through the conduit with compressed air tie the end of your string to your pulling rope and lube the rope with wire pulling lube it will keep you from burning 90's. pull your rope through and then be sure to tape the heck out of the wire to rope connection. Invite buddies over and offer beer in barn, they'll pitch in... I think. Don't use a come along. this stretchs the wire and can damage insulation resulting in shorts like mentioned in other reply. Oh yeah wire lube is available at any electrical supply, get a big tub and spread liberally on cable as feeding it into the conduit.


dave 50 8n    Posted 02-08-2004 at 22:53:19       [Reply]  [No Email]
I'm not an electrician, but would two 45's be better to run than a 90? It'd take more of an arc, but that's the idea for an easier pull.

I reran the wire from my garage to my wellhouse the other day/night. Tried to pull it back from inside the garage...pull...pull...pull. Dang, wasn't coming. So, I got serious and got my come along and wire grabber and hooked it up to one of my ceiling joists.

The joists began to creak and splinter. Whoa. So I gave up. I later found out, while grubbing around under the deck, that the wire had come from the wellhouse out of a pipe and had been stapled to the deck...it went 90 degrees from there to inside the garage.

Note: The reason I had to replace the wire was that the flat, 4/5 wire cable they used had gotten hung up on a metal 90 and nicked the insulation...over the years it finally shorted out. I replaced it w/underground wire.


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