Max distance from panels to charge controller

[f0xmulder]

Hello, I am new to solar, so please bare with me. I live in a rural area of N.C. and my house is surrounded by huge Oak and Pecan trees. We do not have county water, we solely rely on a well/pump, so this means when the power goes out, we have no water. I would like to completely take my water pump off the grid, and I am currently calculating my needs. My question is- What is the max distance you can have your panels from the charge controller/batteries, without having voltage drop. In order to get out from under the trees, I would need to have the panels about 300ft. away, in a pasture. Thanks for any input, F0x

[Sunking]

Depends on the current, voltage, and distance. You want to keep the loss to less than 2%. At 300 feet will be very large expensive copper wire. So all we know is the 1-way distance of 300 feet. What is the voltage and current?

For example lets say you have a 12 volt 100 watt panel. Voltage is 17 volts and current is 6 amps. Minimum size to be safely handle the current is 14 AWG copper, but it would not even operate at 300 feet distance. It would take 500 MCM copper cable to achieve 2% or less voltage drop.

Here is the fun part you are going to be tickled pink about.

• #14 AWG cost roughly 10-cents per foot and you need 600 feet or $60 but it will not even remotely work. FWIW #14 AWG in this example is good for about 10 feet 1-way, but you asked for 300 feet 1-way.
• 500 MCM cost roughly $9/ft and you need 600 feet or $5400 to make it work.

Told you it was really fun and exciting.

[russ]

A couple of calculators to try

http://www.powerstream.com/Wire_Size.htm

Wire size calculator http://www.freesunpower.com/wire_calc.php


Voltage drop calculator http://www.csgnetwork.com/voltagedropcalc.html

[f0xmulder]

Thanks for the info, back to the drawing board

[inetdog]

Hello, I am new to solar, so please bare with me. I live in a rural area of N.C. and my house is surrounded by huge Oak and Pecan trees. We do not have county water, we solely rely on a well/pump, so this means when the power goes out, we have no water. I would like to completely take my water pump off the grid, and I am currently calculating my needs. My question is- What is the max distance you can have your panels from the charge controller/batteries, without having voltage drop. In order to get out from under the trees, I would need to have the panels about 300ft. away, in a pasture. Thanks for any input, F0x

If the cost of copper staggers you, but you are still standing, take a good look at using aluminum instead. It will cost about 1/3 as much, even after allowing for having to use a larger gauge wire.

[f0xmulder]

Thanks for the tip, I will definitely look into the aluminum wire, I also plan on trying to figure a way to shorten the distance from panels to batteries.

[Sunking]

If the cost of copper staggers you, but you are still standing, take a good look at using aluminum instead.

Great advice dude. Instead of costing home $9/ft Cu, it will cost him $5/ft for 750 MCM Al or $3000. He goes from a cable the size of his wrist which he cannot possible terminate, to a cable the size the size of his biceps or ankles which he stands no chance of terminating.

Sorry, but the situation is silly to even attempt.

[Naptown]

OK stop
300' isn't that long of a distance. unless you are going 12V. ( I have 4KW grid tie systems at 700' from inverter but voltage is higher and amperage is lower)
I would suggest a an Midnight solar classic 250 CC that will allow him to run up to 250V into it.
This will drastically reduce the voltage drop and wire size required to run it.
Now for panels I would suggest minimum 72 or higher cell count modules to start at the highest voltage possible and string them in series to go up to the safe maximum temperature compensated array that can be created.
If voltage drop can be calculated in, perhaps going a bit over the max voltage on VOC at the coldest day on record may be plausible. It will require some very careful calculations however.

In his case however it may be better to install a hybrid grid tie system. This would allow both a higher voltage coming from the array, allow him to sell back excess energy to the utility, allow a smaller battery bank, and make the batteries last much longer than with daily use.
Taking the well completely off grid makes little sense from a strictly economic standpoint.

[inetdog]

Great advice dude. Instead of costing home $9/ft Cu, it will cost him $5/ft for 750 MCM Al or $3000. He goes from a cable the size of his wrist which he cannot possible terminate, to a cable the size the size of his biceps or ankles which he stands no chance of terminating.

Sorry, but the situation is silly to even attempt.

It is only too silly to attempt if you assume that he is talking about one panel at nominal 12 volts. I did not see that in the original post!

Once you raise the operating voltage by adding more panels, as Naptown suggested, the current stays the same, and the voltage drop for 14ga stays the same (still too high, admittedly) but becomes a much lower percentage of the operating voltage and therefore a lower percentage of the power is lost.

Yet another possible scenario (for either grid-tied or off-grid) is to put the inverter (grid tied) or the inverter, charge controller and batteries (off-grid) in a tastefully constructed "shack" near the panels and run 120 or 240 AC back to the house.

Knocking down a straw man without taking the time to suggest alternatives is giving valid information, but not helping to solve the problem if a solution exists.

[f0xmulder]

I was looking at 3 or 4, 24v/230 watt panels. I have never thought about a grid tied system, that is something to consider. I was checking things out this afternoon, and I could put the panels on top of an old tobacco barn. I never really thought about that barn because I didn't have a lot of confidence in the structural integrity. It seems sturdy enough, it's not like panels weigh a ton. That would knock the distance down to about 75'.

[inetdog]

I was looking at 3 or 4, 24v/230 watt panels. I have never thought about a grid tied system, that is something to consider. I was checking things out this afternoon, and I could put the panels on top of an old tobacco barn. I never really thought about that barn because I didn't have a lot of confidence in the structural integrity. It seems sturdy enough, it's not like panels weigh a ton. That would knock the distance down to about 75'.

Take a close look at the direction the roof faces (South would be best, of course), and also figure out the arc of the sun through the sky in summer and in winter to see whether you will be getting early morning or late afternoon shade. (If you do, it probably will not reduce your total production much!)

[Sunking]

OK stop
300' isn't that long of a distance. unless you are going 12V. ( I have 4KW grid tie systems at 700' from inverter but voltage is higher and amperage is lower)

Rich he said OFF GRID meaning battery. I agree using a Classic 250 is the way to go if he attempts this but that controller is $800. Personally and I am only guessing, is to put the CC and batteries where the panels are located, then use a 240 VAC inverter to power the well pump.

[Naptown]

Dereck
Agreed at 250V power is limited. Voltage drop can be substantial at that voltage and power and distance.
I also suggested a grid tie hybrid system to allow the well to be run during outages, allow for higher voltage and less losses, and also allow for sale back to the grid during the time that the grid is up.
Now the downside to this is that it will be expensive. much more than a propane generator or even a gasoline generator including fuel costs and maintenance.
BTW I use a Home Depot cheapie 5KW gas generator to power all my basic needs including Furnace, Propane HW(POWER VENT) well (275' head) lights, Fios (cant live without all of you on the internet) tv'S 2 refrigerators a freezer and the occasional sump pump discharge(rare unless it is raining a lot) plus one window shaker AC unit to allow the fat to sleep when it is hot.
Last time we were without power for 5 days I went through about 20 gallons of gasoline. Granted this was much more than the electric would have cost for the equivalent KWH but was worth it. Gas was a bit hard to find though, as the stations were without power and pumps also. but thinking ahead was the key to success.