Designing system when panels are up to 400 feet from cabin

mydogclintonmydogclinton Registered Users Posts: 4
I recently completed a renovation and expansion of a cabin in Vermont, and specifically designed it to be powered by an off-grid solar energy system. There is no power going to the cabin and I have lived with a generator for years. As we plan on using the cabin more often and - now that it is larger - with friends I am prepared to build a system.

Initially, I thought of installing panels on a south facing roof, but the area is wooded and it would require clearing too many trees for my liking. The alternative is a large field 350 feet from the cabin.

I estimate my monthly energy consumption at 90kw and based on Strafford's location estimate a solar panel array size of 1.3kw. Most of my energy need is AC with the exception of a DC powered Novacool fridge

Initially, I was prepared to purchase and install a 24V system with (6) Solarworld 240W mono panels, (8 ) trojan 6v L16re batteries and an Outback Flexpower One system, with a Honda eu3000 as a backup generator. But from what I have read going to a 48volt array is preferred for a long wire length from the house. Does that now mean the rest of the system needs to be 48 volt as well - the battery pack, and the Flewpower system and that I would would need a step down for the fridge? Or can I step down the voltage coming from the array to fit a system that is primarily 24volt? What is feasible and optimal?

Thanks

Comments

  • BB.BB. Super Moderators, Administrators Posts: 31,765 admin
    Re: Designing system when panels are up to 400 feet from cabin

    In general, you want to send energy at the highest system voltage you can for long distances... And, generally, you have two major options.

    First is to use a relatively high voltage MPPT charge controller (you can get controller with Vmp-array support upwards of 200 volts, or even one that will operate at around ~400 Volts Vmp-array--for a lot of extra money).

    The second is to build out your system (panels, charger, batteries, 120/240 VAC split phase inverter) at the site of the solar array and run it to your home.

    If you do not have a well nearby (or other AC power needing devices), I probably would look at the remote array, local to the house batteries/electronics/generator first (saves you having to walk 350 feet every time you want to check the battery bank, etc.).

    A 90 kWH per month load is not very large--I will use 100 kWH per month for the numbers here (round, and a little extra power if needed)... So, first the array of 1.3kW using PV Watts for Burlington VT, fixed array, 0.52 typical off grid system efficiency:
    "Station Identification"
    "City:","Burlington"
    "State:","Vermont"
    "Lat (deg N):", 44.47
    "Long (deg W):", 73.15
    "Elev (m): ", 104
    "PV System Specifications"
    "DC Rating:"," 1.3 kW"
    "DC to AC Derate Factor:"," 0.520"
    "AC Rating:"," 0.7 kW"
    "Array Type: Fixed Tilt"
    "Array Tilt:"," 44.5"
    "Array Azimuth:","180.0"

    "Energy Specifications"
    "Cost of Electricity:","12.9 cents/kWh"

    "Results"
    "Month", "Solar Radiation (kWh/m^2/day)", "AC Energy (kWh)", "Energy Value ($)"
    1, 3.12, 68, 8.77
    2, 4.01, 79, 10.19
    3, 4.91, 104, 13.42
    4, 5.05, 97, 12.51
    5, 5.51, 104, 13.42
    6, 5.42, 97, 12.51
    7, 5.47, 100, 12.90
    8, 5.46, 101, 13.03
    9, 4.70, 87, 11.22
    10, 3.79, 74, 9.55
    11, 2.37, 45, 5.80
    12, 2.15, 44, 5.68
    "Year", 4.33, 999, 128.87

    So--you need of 90kWH per month is a bit light for about 1/2 the year--Is the proposed array large enough for your needs at this point?

    I have to go right now, but here are two solar charge controllers that operate at higher Vmp-array voltages for you to review:

    Midnite classic (250-300 VDC max)
    Xantrex XW MPPT 80 Amp 600VDC Solar Charge Controller (600 VDC max)

    And look at these couple of 120/240 VAC split phase inverters, or even the single 120 VAC inverters (if not remote installed at the array site and no need for 240 VAC):

    Magnum Energy Sine Wave Inverters & Accessories

    If you do not need 2kW+ of inverter power (i.e., no refrigerator, washer, etc.)--Then we can talk about something way smaller (many people do pretty well with a 300 watt TSW 12 volt inverter for their off grid needs):

    MorningStar TSW 300 Watt 12 VDC inverter with "sleep" mode

    --At this point, if this is a near full time off grid residence with fridge, I would be suggesting an array almost 2x larger than you have suggested.

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
  • CariboocootCariboocoot Banned Posts: 17,615 ✭✭
    Re: Designing system when panels are up to 400 feet from cabin

    Welcome to the forum.

    And welcome to the world of high(er) Voltage power transmission.

    350 Feet is quite a ways, even with a nominal 48 Volt array.

    Those Solar World panels have a Vmp around 30 and an Imp of about 8. This means you won't actually get a 48 Volt array out of them, as that would require a Vmp of 70, not 60 (two in series). You can put three in series for a 90 Volt array. In two parallel strings you'd have a current around 16 Amps. Even that is going to require 4 AWG or larger to keep the Voltage drop minimal. That's a lot of expensive wire.

    Alternatives:

    Put all the gear at the panel site and run 240 VAC to the cabin. Depending on how much power you need from the inverter (say 4kW max or around 16 Amps) this would reduce the wire size needed for the 350 foot run to 8 AWG (with acceptable losses).

    Run all the panels in series for a high Voltage DC array of 180 Vmp and 8 Imp. This would also require 8 AWG and a high Voltage MPPT controller like the MidNite Classic 250 (even that would shut down in cold temps due to high Voc) or the very expensive Xantrex XW MPPT 80 - 600.

    (Double-check those V-drop calculations as I did them "on the fly" so they are only approximations.)

    I don't understand your question about "step down for the 'frige"; you're not thinking of an all DC system, are you? That would not be my choice. The 120 VAC install is far simpler and easier to get anything you want for, even if you do have to allocate for feeding the inverter.

    BTW, your proposed battery bank is 320+ Amp hours @ 48 Volts. Your proposed array is a bit lean for that in my opinion. About 7% peak charge rate on 320 (not sure exactly which L16's you're planning on). I'd try for a larger array if possible; the sun does not shine brightly all the time.
  • vtmapsvtmaps Solar Expert Posts: 3,738 ✭✭✭✭
    Re: Designing system when panels are up to 400 feet from cabin
    Alternatives:
    Put all the gear at the panel site and run 240 VAC to the cabin. Depending on how much power you need from the inverter (say 4kW max or around 16 Amps) this would reduce the wire size needed for the 350 foot run to 8 AWG (with acceptable losses).

    There is a lot to be said for having your gear and batteries in an outbuilding. I have my gear and batteries in a garage 50 ft from my house. Most equipment makes audible noise and RF noise, and can be quite annoying if it is in your house.

    To run 240 volt AC with the system you describe, you will need step up and step down transformers. If you go that route (240 volt AC), you might consider looking at the Magnum inverters (BB. gave you a link in his response).

    --vtMaps
    4 X 235watt Samsung, Midnite ePanel, Outback VFX3524 FM60 & mate, 4 Interstate L16, trimetric, Honda eu2000i
  • mydogclintonmydogclinton Registered Users Posts: 4
    Re: Designing system when panels are up to 400 feet from cabin

    Hi Bill, thanks for your comments:

    As you say I rather not walk through the woods 350 feet every time I want to check my batteries. I would rather keep the batteries, inverter, and charge controller at the house. And I do have a fridge and an soft start water pump so do need an inverter to handle that load.

    I was curious about the PV Watts calculation you provided. You question whether the array was large enough to handle my electricity needs. I did the calculation myself because I was surprised at your results. Strafford is closer and is the same latitude as Concord NH and a better comparison to Burlington so that accounted for some of the difference. But the DC to AC derate ratio you used was .52 as opposed to the "standard ".77" That's interesting. Could you explain?

    Thanks again,

    John
  • mtdocmtdoc Solar Expert Posts: 600 ✭✭
    Re: Designing system when panels are up to 400 feet from cabin
    As you say I rather not walk through the woods 350 feet every time I want to check my batteries. I would rather keep the batteries, inverter, and charge controller at the house.

    Just an FYI - there are a few ways you could remotely monitor batteries and system with equipment 400 ft away. An Outback FP1 system includes a FNDC battery monitor. The Mate has a serial port that can be connected remotely at your power shack to a cheap, used laptop and Cat-5 cable then run with your AC wiring to the cabin for monitoring on a computer. There are also ways to do this without the second computer. Some extra cost there but minimal and much less than it will cost to send large gauge copper for DC wiring that distance. The remote monitoring is also something you may want in any case to allow you to monitor your system while away from the cabin.
  • CariboocootCariboocoot Banned Posts: 17,615 ✭✭
    Re: Designing system when panels are up to 400 feet from cabin
    Hi Bill, thanks for your comments:

    As you say I rather not walk through the woods 350 feet every time I want to check my batteries. I would rather keep the batteries, inverter, and charge controller at the house. And I do have a fridge and an soft start water pump so do need an inverter to handle that load.

    I was curious about the PV Watts calculation you provided. You question whether the array was large enough to handle my electricity needs. I did the calculation myself because I was surprised at your results. Strafford is closer and is the same latitude as Concord NH and a better comparison to Burlington so that accounted for some of the difference. But the DC to AC derate ratio you used was .52 as opposed to the "standard ".77" That's interesting. Could you explain?

    Thanks again,

    John

    The over-all derating factor for an off-grid system is 0.52. That's from panel 'nameplate' to AC Watt hours. So if you have a 2kW array and 4 hours "equivalent good sun" you get: 2kW * 4 hours * 0.52 = 4160 Watt hours per day.

    The 0.77 derating is for panels & MPPT charge controller or panels & GT inverter. So if you have a 2kW array on a GT inverter you can expect it to perform as 1540 Watts in good sun on average.

    The big difference between the two comes down to storage. A GT inverter always has someplace to send the power. Once batteries are full, on the other hand, the power potential of the panels goes unrealized.

    PV Watts is really designed for GT systems, not off-grid. But it does give you some relative idea of what to expect.

    How did you calculate your load requirements? If you didn't measure the equipment you intend to use under 'real world' conditions with a Kill-A-Watt chances are that power usage figure is wrong.
  • icarusicarus Solar Expert Posts: 5,433 ✭✭✭✭
    Re: Designing system when panels are up to 400 feet from cabin

    Put the batteries and the DC equipment close to the array, then send higher voltage Ac tithe house. Step down to run the fridge as needed. Consider changing out the fridge, as modern energy star fridges are reasonably priced, and quite efficient.

    Tony
  • mydogclintonmydogclinton Registered Users Posts: 4
    Re: Designing system when panels are up to 400 feet from cabin

    Hi,

    Thanks for the reply. I live in Vermont and its pretty cold here in the winter. My understanding is that cold temperature exposure would limit the life of the batteries. So for that reason I figured placing them in a warm room (I built an utility room as an extension onto the cabin) was preferred. Of your alternatives I prefer paralelling the panels and purchasing the Xantrex.

    ANd you are not the only person who mentioned the array might be on the small side. I am considering then to go bigger, though how much bigger is not decided.

    Thanks, John
    Welcome to the forum.

    And welcome to the world of high(er) Voltage power transmission.

    350 Feet is quite a ways, even with a nominal 48 Volt array.

    Those Solar World panels have a Vmp around 30 and an Imp of about 8. This means you won't actually get a 48 Volt array out of them, as that would require a Vmp of 70, not 60 (two in series). You can put three in series for a 90 Volt array. In two parallel strings you'd have a current around 16 Amps. Even that is going to require 4 AWG or larger to keep the Voltage drop minimal. That's a lot of expensive wire.

    Alternatives:

    Put all the gear at the panel site and run 240 VAC to the cabin. Depending on how much power you need from the inverter (say 4kW max or around 16 Amps) this would reduce the wire size needed for the 350 foot run to 8 AWG (with acceptable losses).

    Run all the panels in series for a high Voltage DC array of 180 Vmp and 8 Imp. This would also require 8 AWG and a high Voltage MPPT controller like the MidNite Classic 250 (even that would shut down in cold temps due to high Voc) or the very expensive Xantrex XW MPPT 80 - 600.

    (Double-check those V-drop calculations as I did them "on the fly" so they are only approximations.)

    I don't understand your question about "step down for the 'frige"; you're not thinking of an all DC system, are you? That would not be my choice. The 120 VAC install is far simpler and easier to get anything you want for, even if you do have to allocate for feeding the inverter.

    BTW, your proposed battery bank is 320+ Amp hours @ 48 Volts. Your proposed array is a bit lean for that in my opinion. About 7% peak charge rate on 320 (not sure exactly which L16's you're planning on). I'd try for a larger array if possible; the sun does not shine brightly all the time.
  • CariboocootCariboocoot Banned Posts: 17,615 ✭✭
    Re: Designing system when panels are up to 400 feet from cabin
    Hi,

    Thanks for the reply. I live in Vermont and its pretty cold here in the winter. My understanding is that cold temperature exposure would limit the life of the batteries. So for that reason I figured placing them in a warm room (I built an utility room as an extension onto the cabin) was preferred.

    Cold temps won't shorten battery life, but will reduce capacity while cold. It actually slows down the chemical reaction that creates the power, so slower = longer life but at the expense of some of that power as capacity.

    As long as the batteries are kept charged they won't freeze, and usually there's enough activity to keep them above ambient with a bit of insulation around them. What batteries really like is a consistent temperature around 20C/68F.
    Of your alternatives I prefer paralelling the panels and purchasing the Xantrex.

    ANd you are not the only person who mentioned the array might be on the small side. I am considering then to go bigger, though how much bigger is not decided.

    Thanks, John

    Actually you mean placing the panels in series to increase the Voltage, not parallel. :D
    A MidNite Classic 250 will handle up to 250 Volts, with a Voc max of 298 on a 48 Volt system. They're about half the price of the Xantrex XW 600 MPPT 80, so consider all the options and work it out "on paper" before you spend the $.
  • nielniel Solar Expert Posts: 10,300 ✭✭✭✭
    Re: Designing system when panels are up to 400 feet from cabin

    i think the dc high voltage is an option and he is going to need some heavy copper wire no matter what.

    i did some calculating for him and the classic 250 will accommodate 5 of those pvs in series as 6 would go into hypervoc at a mere 17 degrees f and you want power when it's cold so 5 is max in series. this would be good on a 350ft run of #6 copper (700ft total) wire and would be under 2% v drop loss. the problem with that is 5 pvs is not enough for him. to expand on this would mean 5 more pvs for a total of 10 in 2 strings of 5. this is 2400w stc and would require 700ft of #2 to stay under 2% v drop loss, but using #3 (now common from what i understand for service entrances) would also meet the under 2% v drop loss mark. to go #4 would go over, but not by much at about 2.25% v drop loss.

    to go with 2 strings of 3 (6 pvs total with 1440w stc) would present a vmp of 91.8v at 15.74a total. to get that under 2% would involve 700ft of #0. ouch!!! now #2 would go to 2.4% v drop loss. only consolation is that you can use the classic 150.

    if you go 2 strings of 4 pvs in series you would need a total of 8 pvs for a 1920w stc array. the classic 200 would suffice for this pv arrangement. (might be close enough to the .52 derating to suit your ac loads)(also note if using agms then the charge efficiency of these batteries would bring the overall derating to i think about .57 and bill can correct me on that if i'm wrong) anyway, this would give a vmp of 122.4v at 15.74a total. this would require 700ft of #2 to stay under 2%. going with #3 would also put it about 2.25% v drop loss.

    the bottom line here is you need to come as close as you can by maybe cutting down some more trees. cutting another 50ft of trees going towards your dwelling will shave 100ft of wire off your requirements and can change things significantly. that 100ft cut off for a total of 600ft would bring the v drop loss of the 2 strings of 4 pvs to under 2% with #3 wire and #4 would be 2.45% v drop loss. i used the v drop calculator in my signature line and the midnite string calculator.

    edit to add: i noticed i misremembered the run length that it was 400ft and not 350ft so to reach my figures you'd need to cut about 25ft of trees. sorry about that, but it still gives you a pretty good idea of what you face.
  • vtmapsvtmaps Solar Expert Posts: 3,738 ✭✭✭✭
    Re: Designing system when panels are up to 400 feet from cabin
    niel wrote: »
    the bottom line here is you need to come as close as you can by maybe cutting down some more trees. cutting another 50ft of trees going towards your dwelling....

    Another desirable way to shave 50 ft off the run is to put a power shed between the house and the array. 50 ft from the house would still be convenient for checking the batteries. There are many advantages to having a power shed. The two that impress me the most are safety and freedom from audible and RF noise.

    Safety: If you spend a year on this forum, you will read about generators burning up. You will read about lightning frying inverters and other electronics. Some lightning arrestors explode when doing their job, do you want them in your house? You will learn about the odors that emanate from batteries. Its good to mount your electronics on a fireproof wall so that when they get very hot from arcs (and insulation starts burning) they don't burn down the house.

    Freedom from noise: Speaks for itself... you must search and read some of the threads here from folks who lie awake listening to the relays in their controllers clacking. Some inverters make a lot of audible hum. (ask not for whom the inverter hums, it hums for thee). And there are a few good threads on how difficult it is to use your radios in the vicinity of your power electronics.

    Don't worry about your batteries being too cold. Line your battery box with 2 inches of foam insulation (remove in summer) and your batteries will be fine. If you use them enough (which warms them up) they will stay quite a bit warmer than ambient. They will have reduced capacity and longer life. The capacity loss is temporary, in the summer their capacity returns. Probably the best way to set up a power shed is to berm it into the side of a hill (almost no flat land in Strafford VT) and let the batteries be warmed by the earth. Batteries in a root cellar temperature environment, in an insulated battery box will maintain ideal temperature.

    The earth berm also helps the batteries stay cool in summer. Batteries above 75° F will have increased capacity (to a point), increased self discharge, and reduced life.

    You can have all of your control & monitoring electronics in your house. You need to run two conduits between the house and the shed, one for your power (120 or 240 volts AC), and one conduit for control, monitoring, and/or DC power (I think you mentioned 24 v DC refrigeration).

    --vtMaps
    4 X 235watt Samsung, Midnite ePanel, Outback VFX3524 FM60 & mate, 4 Interstate L16, trimetric, Honda eu2000i
  • Eric LEric L Solar Expert Posts: 262 ✭✭
    Re: Designing system when panels are up to 400 feet from cabin

    I just want to second what vtmaps said. A small shed will cost money but might allow you to save a bit going with smaller wire. And of course the shed would give you added storage space if you need it.

    Like you, I had many trees around my house that I didn't want to remove but a clearing nearby. I put a shed half-way with my system, which has an approximately 240 foot run from panels to the house distribution panel. For the rest of the distance I ran the panels in series for higher voltage and used Midnite controllers. I was ultimately able to use #8 AWG wire from the panels to the controllers with less than a 3% loss -- a huge savings in wire right there. It's nice not having the off-gassing from the batteries in the house, and not having the noise or the added fire potential of the equipment in the house either.

    Also, doing it his way means no significant modifications to my house for the solar; the only connection to the system is an AC line that goes to a transfer switch. This may not be an issue for you, but I like having everything easily reversible if I ever sold my house.
  • GreenPowerManiacGreenPowerManiac Solar Expert Posts: 453 ✭✭✭
    Re: Designing system when panels are up to 400 feet from cabin

    Easiest and cheapest way to run that distance is inverting to A/C from your source, then running at least 6-3 underground wire to a load center in the garage or home.
    Nature's Design & Green Energy on FaceBook : Stop by and "Like" us anytime.. Many up-to-date articles about Renewables every day.
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  • mydogclintonmydogclinton Registered Users Posts: 4
    Re: Designing system when panels are up to 400 feet from cabin

    Eric, Thanks for your post. This sounds interesting for sure. I do have some questions. The distance between the panels and your home is 240 feet, and the shed is let's say half-way. Ok, based on that here on my questions:

    Q: did you run #8 AWG from the shed to the house
    Q: When you say AC was running from the shed to the house, I am assuming that was 240v AC?
    Q: Ever have an issue with hig Voc/

    Thanks, John
  • gww1gww1 Solar Expert Posts: 963 ✭✭
    Re: Designing system when panels are up to 400 feet from cabin

    I am running 200' and intend on using aluminum service wire as it is cheaper even though larger gage wire. Does this cause problims and would this also be an option as opposed to copper?
    thanks
    gww
  • BB.BB. Super Moderators, Administrators Posts: 31,765 admin
    Re: Designing system when panels are up to 400 feet from cabin

    Get an approved Aluminum to Copper connector (typically crimp pre-lubricated with anti-corrosion paste). An electrician should be able to help you there (and have the proper crimping tool). Usually you would attach copper pigtails for connections to your breakers/system bus bars. I would avoid inserting aluminum wiring into the typical breakers/bus bars--If you do use aluminum directly, make sure they are rated for use with aluminum wiring).

    Don't use standard copper to copper connection methods with Copper/Aluminum connections.

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
  • gww1gww1 Solar Expert Posts: 963 ✭✭
    Re: Designing system when panels are up to 400 feet from cabin

    Bill
    Other wise OK? Alum. is deffinatly much cheaper for the wire with less voltage drop for 200' run.
    thanks
    gww
  • Eric LEric L Solar Expert Posts: 262 ✭✭
    Re: Designing system when panels are up to 400 feet from cabin
    Q: did you run #8 AWG from the shed to the house
    Yes.
    Q: When you say AC was running from the shed to the house, I am assuming that was 240v AC?
    Right. At 240 v, #8 will take the maximum output of my inverter at a less than 3% loss.
    Q: Ever have an issue with hig Voc/
    No, but I live in Alabama and so don't have temps below about 15 F.
    Midnite solar has a string-sizing tool for use with their controllers:

    http://www.midnitesolar.com/sizingTool/index.php
  • SurfpathSurfpath Solar Expert Posts: 417 ✭✭✭
    Re: Designing system when panels are up to 400 feet from cabin
    mtdoc wrote: »
    Just an FYI - there are a few ways you could remotely monitor batteries and system with equipment 400 ft away. An Outback FP1 system includes a FNDC battery monitor. The Mate has a serial port that can be connected remotely at your power shack to a cheap, used laptop and Cat-5 cable then run with your AC wiring to the cabin for monitoring on a computer. There are also ways to do this without the second computer. Some extra cost there but minimal and much less than it will cost to send large gauge copper for DC wiring that distance. The remote monitoring is also something you may want in any case to allow you to monitor your system while away from the cabin.

    Hi and welcome,
    As mtdoc says you can monitor your system from the Mate serial port using a PC. You can also take your Mate off the Flexpower 1 panel and have it mounted in your cabin. From the Outback website: the maximum Mate Cat5 "cable length is 1000' (300 m)." Just another option.
    -SP
    Outback Flexpower 1 (FM80, VFX3048E-230v, Mate, FlexNetDC) 2,730watts of "Grid-type" PV, 370 AmpHrs Trojan RE-B's, Honda 2000 watt genny, 100% off grid.
  • nielniel Solar Expert Posts: 10,300 ✭✭✭✭
    Re: Designing system when panels are up to 400 feet from cabin

    i think some of you are misunderstanding what are acceptable losses. you should not be running up to 3% from pvs to cc, batteries, and inverter, plus 3% from inverter to the house. it should be less than this, (<5% total) but it is a tough situation too and won't easily be very efficient without bigger investment. be sure to properly calculate for the aluminum gauge wire you are using as the resistance of al is greater for a given gauge # than copper.
  • vtmapsvtmaps Solar Expert Posts: 3,738 ✭✭✭✭
    Re: Designing system when panels are up to 400 feet from cabin
    gww1 wrote: »
    Alum. is definitely much cheaper for the wire with less voltage drop for 200' run.

    Don't be so sure. By the time you add on the cost of those special connectors it may not be as cheap.

    In case your copper-aluminum transitions get a bit hot, its a good idea to house those transitions in a metal box that is located in a fireproof area.

    Depending on the gauges involved, you may also need a larger size conduit for the aluminum.

    I'm not saying that aluminum isn't the way to go, but I suspect that at a 200 ft run, copper might still be competitive. Has anyone developed a rule of thumb that says at what distance aluminum is cheaper than copper?

    --vtMaps
    4 X 235watt Samsung, Midnite ePanel, Outback VFX3524 FM60 & mate, 4 Interstate L16, trimetric, Honda eu2000i
  • CariboocootCariboocoot Banned Posts: 17,615 ✭✭
    Re: Designing system when panels are up to 400 feet from cabin
    vtmaps wrote: »
    Has anyone developed a rule of thumb that says at what distance aluminum is cheaper than copper?

    --vtMaps

    Kind of difficult to do with prices varying from place to place and day to day.
    Up here you'd be hard-pressed to find a deal on aluminium wiring.
    Which is not to say copper is inexpensive.
  • gww1gww1 Solar Expert Posts: 963 ✭✭
    Re: Designing system when panels are up to 400 feet from cabin

    I have been pricing direct burial 2/0 copper and 4/0 aluminum on the internet and on ebay and the price differance was almost double and mostly even more.

    If I buy direct burial is there any use of conduit for the underground portion? I got these sizes from an online voltage caculator for a 200' run 88 volts 36 amps if I remember correctly.

    Around $900 for 4 wires 200' ea 4/0 gage alum. not counting the connectors
    Thanks
    gww
  • inetdoginetdog Solar Expert Posts: 3,123 ✭✭✭✭
    Re: Designing system when panels are up to 400 feet from cabin
    gww1 wrote: »
    If I buy direct burial is there any use of conduit for the underground portion?
    Thanks
    gww

    The main reason for putting direct burial wire in conduit would be to protect it from mechanical damage. The NEC and/or your local codes may specify the minimum distance below the surface you must bury the cable (you cannot just run it exposed because it may not be rated for UV exposure). At a minimum, you will need to protect the wiring between the point where it comes out of the ground to the point were it is terminated inside an enclosure of some kind. Depending on where you are burying it (soil, traffic, likely digging, etc.) you may still want to put in conduit or just a PVC sleeve for the whole length.
    SMA SB 3000, old BP panels.
  • gww1gww1 Solar Expert Posts: 963 ✭✭
    Re: Designing system when panels are up to 400 feet from cabin

    inetdog
    Thanks for the answer. I would like to meet nec but won't be inspected. I was just going to use a trencher and go below the frost line.
    I am hoping this is good enough.
    Thanks
    gww
  • solarvicsolarvic Solar Expert Posts: 1,060 ✭✭✭✭
    Re: Designing system when panels are up to 400 feet from cabin

    I don,t know if groundhogs well chew into direct burial cable or not. I had to replace my satelite ribbon cable 3 times because of groundhogs. The last time I had to put new wire on I put used cat litter in with the cable. Had 3 different people saving thier used cat litter. Must have worked as the groundhogs stay away from where I have the cable buried and I haven,t had any more ground hog damage. Now they chewed my sparkplug wires on my Geo Prizm and I have replaced them 4 times. :Dsolarvic:D
  • inetdoginetdog Solar Expert Posts: 3,123 ✭✭✭✭
    Re: Designing system when panels are up to 400 feet from cabin
    gww1 wrote: »
    inetdog
    Thanks for the answer. I would like to meet nec but won't be inspected. I was just going to use a trencher and go below the frost line.
    I am hoping this is good enough.
    Thanks
    gww

    Since you do not have to worry about inspection, just do what is needed to protect the wires from attack by people, squirrels, etc. That will meet the spirit of the NEC.
    SMA SB 3000, old BP panels.
  • gww1gww1 Solar Expert Posts: 963 ✭✭
    Re: Designing system when panels are up to 400 feet from cabin

    solarvic and inetdog
    Thanks for the answers. I had squirils eat the wires on my truck. I could watch them climb under the truck. Have had horses eat the wires off a tractor.
    Thanks again
    gww
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