Running Electric

[miohman]

I am looking to run electric 2600 feet and need 80 amps at the end of the line. I have been told to step it up to 480 single phase for the run and I won't need nearly the wire size. How do i do the calculation on what size transformer I will need? How many amps of 480 do I need to run 80 amps of 240/120?

Thanks

[Super Sapper]

Amps are amps, you will need the same at 120 or 480. On 480 you're dividing it up on 3 wires instead of one, on 240 it will be divided by 2. You will have some loss in the length of the run so 3 wires of whatever wire size is needed to run 30 amps 2600 feet.

[everbuddy]

I think you meant that watts are watts. If you step it up to 480v single phase you would need half the amps to have the same power.

[lpakiz]

Right on the watts. 80 amps at 110 can be had with 40 amps on 220. The wire could be exactly half the size.
Not sure how to break 440 down to 110, but I think it can be done.

[maple flats]

Correct. The amps will be half. You still have an expensive wiring job. This is why the utility runs 13,000V lines to the final transformer before a residential hook up. You will likely need to step it up higher that 480 or the wire needed will break the bank. I'll do some calculations this evening and give some examples.

[unc23win]

There are number of sites like the following that can help calculate the size of wire needed. You need to know how much loss you will have over that distance. I would guess the transformer stepping up an down would be the electric companies doing on your $. It will be a pricey endeavor for sure. 500 MCM Aluminum wire is about $2 a foot.

http://www.paigewire.com/pumpWireCalc.aspx?AspxAutoDetectCookieSupport=1

https://www.platt.com/platt-electric-supply/XHHW-Compact-Stranded-500-MCM/Multiple/500XHHWABLA4000MCR/product.aspx?zpid=70243

[BreezyHill]

You should also look into a gen set. I run two of them for our feed mill...Cat 100K and a Gas 45 Kw. The gas can run on Propane or Gasoline depending on the cost of them at any given time. The 45 was a state bid and was only $376 with under 600 hours on it and the Cat was a military bid. $1800 with around 1200 hours. The Cat is self contained weighs in around 5 ton. This can be gotten on a single axle trailer that is like a semi dolly rig. They are more costly since anybody with a full size pickup can drag the around.

Both are 3phase units but also make single phase as well.

Very nice to power the entire farm when the grid goes down. Just throw two switches and the farm lights come back on.

Ben

[maple flats]

Here's some calculations to chew on. At 2600' with copper wire for 480V you need 400 Kcmil to end up with 9.81 voltage drop, bring that back to 240 V you then have 4.9V loss less the inefficiency of the 2 transformers. If you use aluminum wire you need 750 Kcmil for the same loss. Wire over 4/0 is sized in Kcmil. 400 Kcmil is special order in lengths over 2500', 2500' is $5.87/ft. Going aluminum, 750 Kcmil aluminum is also special order over 2500', and at 2500' or less it is $2.99/ft.
Now if you can find a transformer to step up to 960V, you could use 2 ga. copper if overhead, 1 ga. if burried. For the copper, overhead, it would be $32/ft each conductor and std coils are up to 5000' long and it can be cut to order. I suggest you try to get the step down transformer with adjustability. That way, at the end you can set the voltage to be at 240 or even 245. Motors will run cooler on that.