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Wire size

Posted by greenmile (My Page) on
Wed, Oct 6, 10 at 15:19

I've tried looking at every electrical wire chart on the internet, but somehow they never seem to answer this question for me.
How big of wire or cable (probably aluminum) would one need to travel 1000' to a 100 amp panel? This would be for a small cabin. Probably air conditioning, but no electric heat or range.

Follow-Up Postings:

RE: Wire size

"How big of wire or cable (probably aluminum) would one need to travel 1000' to a 100 amp panel?"

You have not found the answer because you have omitted required details.

Copper or aluminum wire?

Is the wire in air?
In conduit?
Directly buried?

What insulation temperature rating are you planning on using?

All the information is present in the NEC, but you need to know all the conditions of installation.

RE: Wire size

Big wire. :-)

If it's just a small cabin with lighting and general purpose receptacles plus window a/c unit (or two) you sure as heck don't need a 100 amp sub-panel. The bigger the panel, the larger gauge wire you need which translates into more money.

RE: Wire size

Most people around here seem to use aluminum buried directly in the ground. I have no idea what an insulation temperature rating is. If I did I probably wouldn't need to be on a board like this asking questions.

RE: Wire size

First of all, he already stated Al wire.
Most importantly you need to state how many amps of current you will need. Just because it's a 100A panel doesn't mean you will need 100A.

RE: Wire size

probably more money than you could imagine plus the wire
could be 0000 al.Your better off getting hydro to put in poles.Remember it's both ways. So now your talking 2000 ft.
That's over 1/4 mile. Bottom line is probably not going to happen. Are you sure of your measurements ? They run a hydro pole every 200 feet. If it's a cabin your better off
with a small generator and Coleman lamps. No offence but do
you have any idea of what 1000 feet looks like ? I have 5 1/2 achers 200 feet wide. I'm 400 feet from the road and
880 feet to the river. I can hardly see the river from here.I have 2 hydro poles for my 400 feet. Your talking one hell of a wire and BIG bucks. Just my input. No offence.

RE: Wire size

Size 00 aluminum cable should allow you to run a 60 amp, 1,000 ft underground service with a 7.5% voltage drop. Reduce that to a 40 amp service and it's a size 1 cable.
A 5% voltage drop with 60 amps, would be a size 0000 cable, as would a 100 amp service with 7.5% drop.

RE: Wire size

Don't forget about trenching $$$

RE: Wire size

I've gotten a lot of advice from this board in the past, but hadn't been back in awhile. It has certainly taken a turn for the worse. I can't believe all the arrogance and condescension. Do I know what a 1000 feet looks like? Yes, and I also know how to spell "offense".

Thank you Randy for at least trying to answer the question.

RE: Wire size

When I worked for the POCO, we had a customer that built
a small cabin in the woods and wanted to get power to it.
When I told him all of his options and the big bucks
most of them were, he opted for a meter pole, 100 feet
from our road pole. He then buried, in conduit,
1250ft of 250MCM aluminum. The problem came when he
tried to get an inspection. The inspector wouldn't
issue an inspection, stating the voltage drop would
be too great. I called the inspector and asked where
in the code this rule was. The next day the inspection
came in. He got hooked up and now, more than 10 years
later, no one's heard a peep.

RE: Wire size

Voltage Drop formula is:


Voltage Drop should be less than 5% for feeders.

That said:

1000ft of run with 100amps aluminum cable would require at least 400kcmil Al conductors to meet the 5% maximum voltage drop for feeders.

Or you could use parallel 4/0 Al cable to achieve the same goal.

RE: Wire size

Odd option:

1- install cable rated for load, ignoring voltage drop. Install active voltage correction on load end.

2- transformer on each end.

Both are expensive options, but so is that much cable. I haven't done the math, but one of these options may actually be comparable in cost.

RE: Wire size

greenmile, you got offended by that? Wow.

"all the arrogance and condescension"??? It was one post that was a BIT sarcastic.

If that bothered you that much I am surprised you spend any time at all on internet boards. I hope you are not this thin skinned in the real world.

Everyone else here has genuinely tried to help, even kalining in his own way. What more do you want?

I have stayed out of this because I have seen this scenario many times. Rarely does the person want to hear the correct answers given. Running secondary (120/240v) that far is NOT a good idea for several reasons.

RE: Wire size

I don't know if active voltage correction is appropriate for this. It might be, but my impression is that transformers would be a cheaper way to go. Also probably more commonly used in this application therefore more pleasing to he inspector. At least that is the case in my neck of the woods.

On another note, I have to agree with whoever pointed out that the demand didn't seem to require a 100A service. Maybe a disc. Near the road, with 60 or even as little as 30 or 40a feeders to a sub in the cabin would be more appropriate.

RE: ego size

On another note(prepare for rant):

Greenmile wrote
"Yes, and I also know how to spell "offense"."

Just so you know, you only make yourself look bad when you incorrectly correct someones spelling. Offence is a correct alternative spelling. Used in British and Canadian English. And since the poster is Canadian, you were out of line. I would also like to point out that you probably didn't post here expecting responses from English majors, but (hopefully) qualified electricians. Maybe if you can afford to run a 100A service 1000' to your vacation property, you should PAY for the advice of a qualified electrical contractor.

Free advice often exacts its own price.

RE: Wire size

"I don't know if active voltage correction is appropriate for this. It might be, but my impression is that transformers would be a cheaper way to go."

A buck-boost could easily account for some excessive voltage drop. the problem is that they are really only effective for a constant load (allows the correct taps to be selected).

1000 ft of trenching at required depth is going to be a chore.
Using rigid metal or intermediate metallic conduit would greatly reduce the trench depth, possibly enough to make up for the increased conduit cost over less protective types of conduit.

Trenching through areas with lots of tree roots is a real chore without large equipment (and that requires clearing trees).

RE: Wire size

Bottom line is that there are no low cost solutions. None! With that behind us, the two best choices are (1) pay the POCO to run their primary line to the cabin or (2) install your own step-up transformer after the meter, install your own conductors suitable for the stepped-up voltage and the reduced amperage involved, then a step-down transformer at the cabin.

RE: Wire size

Some food for thought. I've seen quite a few of these
little cabins, over time, expand into full size homes.

RE: Wire size

You might consider solar, especially if your needs are modest. I don't think your 1000' is anything close to the break-even distance (the point at which it's cheaper to buy a PV system than to extend the utility line), but if you already have any inclination in that direction - well, the more it costs to get utility power to your cabin, the better PV looks.

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