wire size and distance

[gregd]

Trying to run house trailer and office trailer;
I was wondering if anyone knows if I can run wires 600' to run lights,ref,computer,A/C(aproxx 30A), and what size wire should I run? Also if I am using a generator for main power(no utilities near by) should i drive a ground rod and bond the neut to the ground of the gen?

 

[rosco]

Look up "wire Ampacety" (sometyhing like that spelling) One of the charts I found for the NEC said #4AWG, but probably #3AWG would be better. Assuming 30 amps is the total. That is expensive wire. Can you move the Genny closer? I believe you need the ground rod, not sure about bonding the neutral.

 

[Isaac-1]

Sure you can do it if your bank account is big enough, seriously though there are a lot of details you have left out.

Ike

 

[derf]

It would probably be cheaper to buy a generator than to try and run 30A 600 feet. Copper is expensive.

 

[Speddmon]

The problem with running cables a long distance is the voltage drop involved. The internal resistance of the wire creates the drop. But, the more amperage you put through the wire means more heat...which means more resistance, and more drop.

There are simple plug in voltage drop calculators on the internet all over. But quite simply, to run 30 amps at 120 volts 600 feet from the source and keep the voltage drop less than 3%, you would need to use a #3/0 conductor for the feed.

Can you say impractical?

 

[4x4 Forever]

But quite simply, to run 30 amps at 120 volts 600 feet from the source and keep the voltage drop less than 3%, you would need to use a #3/0 conductor for the feed.

Can you say impractical?

Nope, but I can see someone crying...I did when I had to buy only 48' of the stuff!

 

[bmwsyc]

I did an install where site power was about 720 feet away from some out buildings. I looked at copper prices and passed out...when I came to, I looked at 2-2-4 Aluminum USE cable...much cheaper and lighter. I have it fused at 60 amps. At the time, I think I did the voltage drop calculations and it worked out okay. The trenching was probably the hardest work I've done as an electrician...it was a side job. It has been over five years and the line has been tapped into by the owner a few times as new building have gone up. Biggest thing is to use anti-oxident with the aluminum wire, don't mix aluminum and copper, and make sure equipment that the aluminum is connected to is rated for use with aluminum wire.

not sure if there are pictures of the grounds, but it was here: http://www.ahlmans.com/

under "more pictures" on main page. From "gun store" to "fort ahlman"

 

[cbvet]

You really need to move generator closer.
Then #10 wire would be sufficient for 30 amps.
Ground the generator & each building.

 

[SCSG-G4]

Might be cheaper in the long run (no pun intended) to have the local power company run a line and a transformer. That way they can tap off the transformer to get the correct voltage and amp capacity at the 'end of the line'. Bigger wire means less voltage drop at full amp capacity, but also much bigger cost. AL is going to be much cheaper than CU, and put it in plastic conduit, not direct buried, to save the expense of re-trenching WHEN you get a failure. I only worked for a power company for 37 years.

 

[Isaac-1]

If this really is a remote site and must be powered by a single generator a pair of transformers could be used (one at each end, sort of like the power company does) to allow you to greatly reduce wire size, the same way the phone company does. Remember transformers are for the most part bidirectional devices, and at only 30 amps you could use fair small ones..

Ike

 

[Speddmon]

Might be cheaper in the long run (no pun intended) to have the local power company run a line and a transformer. That way they can tap off the transformer to get the correct voltage and amp capacity at the 'end of the line'. Bigger wire means less voltage drop at full amp capacity, but also much bigger cost. AL is going to be much cheaper than CU, and put it in plastic conduit, not direct buried, to save the expense of re-trenching WHEN you get a failure. I only worked for a power company for 37 years.

Excellent point Mike. I try to tell everybody not to direct bury any wire. It's not a matter of "if" you'll have a failure with t, it's a matter of "when". Cause it's gonna happen sometime.

If this really is a remote site and must be powered by a single generator a pair of transformers could be used (one at each end, sort of like the power company does) to allow you to greatly reduce wire size, the same way the phone company does. Remember transformers are for the most part bidirectional devices, and at only 30 amps you could use fair small ones..

Ike

Ike, another good idea. I just ran the voltage drop with 480 volts at 600 feet with a 7.5 amp load at the end. 7.5 amps at 480 volts is about 30 amps at 120 volts after you transform the voltage back to 120. You could get by with #10 wire for the run, but the expense of the transformers could get a but much. Unless the OP knows somewhere to get them cheaply.

Add to that the fact that now you'll have to deal with 480 volts rather than 120...more dangerous. And the complexity of hooking up 2 transformers to step up and back down the voltage. All of this not for an amateur...still IMPRACTICAL. Move the generator closer!!!

 

[gregd]

thanks for the replies, the A/C itself would be 30A total amps would be 50-60A, I was going to use alum. overhead which would dissipate the heat better.
Though about using 2 transformers also, but still wondered how big wire between them and the cost of them.
Cant move the genny closer because it will be too far from the house then. power co wants $50000 to run lines plus $500 month min bill.
It may be cheaper to get 2 gens.

 

[ETN550]

Might be cheaper in the long run (no pun intended) to have the local power company run a line and a transformer. That way they can tap off the transformer to get the correct voltage and amp capacity at the 'end of the line'. Bigger wire means less voltage drop at full amp capacity, but also much bigger cost. AL is going to be much cheaper than CU, and put it in plastic conduit, not direct buried, to save the expense of re-trenching WHEN you get a failure. I only worked for a power company for 37 years.

Yup I work for a power company now and we are replacing all secondary direct burried wire in our system that we installed in the 1970's and early 80's. Mostly to housing subdivisions and condo complexes. We have a total of hundreds of miles of it failing or suspect. We are going back with bored in conduit and pulling new wire. At first we just did the failures, but the fix takes time and we were failing so much we could not keep up plus we had to rig temporary power. Now it is all coming out within the next few years.

 

[derf]

thanks for the replies, the A/C itself would be 30A total amps would be 50-60A, I was going to use alum. overhead which would dissipate the heat better.
Though about using 2 transformers also, but still wondered how big wire between them and the cost of them.
Cant move the genny closer because it will be too far from the house then. power co wants $50000 to run lines plus $500 month min bill.
It may be cheaper to get 2 gens.

It would probably be cheaper to buy a generator than to try and run 30A 600 feet. Copper is expensive.

^ This. If you have one large gen by the house then a smaller, portable gen at the other location would give you flexibility. 50-60 Amps, however, is not really in the realm of portable unless you have it trailer mounted. I don't see how it could be cheaper to run CU or AL wire (either above or under ground) than a second gen set. Transformers can reduce wire size in the runs but they are just big, heavy, expensive boxes full of CU.
What size gen do you have at the house that can run the house and have 50-60 Amps extra to send to the other place?
Edit: I suppose you are thinking either/or instead of both.

 

[steelandcanvas]

Excellent point Mike. I try to tell everybody not to direct bury any wire. It's not a matter of "if" you'll have a failure with t, it's a matter of "when". Cause it's gonna happen sometime.

Tom and Mike are totally spot-on! Years ago while doing service work, I constantly told my customers I would not install direct bury wire, unless you wanted to see me again in the next few years to replace it. THWN and PVC is the only way to go.

 

[NEIOWA]

...but the expense of the transformers could get a but much. Unless the OP knows somewhere to get them cheaply.

If you shop some equipment auctions at machine shops, small manufacturers, etc (of the few left) you can find small transformer (in service) for scrap price or less.

 

[Rambling Wreck]

Another option to consider would be to go with smaller wire ran in parallel. You would just have to do a cost comparison and see what kind of deals you could get to determine if it would be cheaper. If the power company wants $50,000 and a $500 min bill/month, then your 600' must be through solid rock, across a gas main, and over a railroad crossing. I think whoever came up with that number was way, way, way off the mark. As far as burying wire goes, totally up to you and your budget. Some folks swear by it (mainly EMC's and electric cities) others don't bother with it unless it is at a street crossing (many investor owned utilities). If you do decide to place it in conduit, I would try to get a reel of flex conduit and I would put in a spare run for comm or anything else that the future may hold. For wire sizing, voltage drop calculations and other useful information, I find American Wire Gauge table and AWG Electrical Current Load Limits with skin depth frequencies to be very helpful.

 

[212sparky]

#2 over head triplex would work. just have to remember you have to keep the sag point roughly 18 feet above ground. It will require 5 or 6, 35 foot poles installed, Insulators on each pole and down guys on each end. If you have more than one building you are feeding, treat each one as its own service so you bond the neutral at each of the first disconnect per structure. If you used 480 volts to distribute you could get away with #6 Triplex. If you go below ground you could get away with 2/0 aluminum in conduit because of the ambient temp of the ground and correction factor for line loss. PM me if you have any other questions.