pulling the plug

offgrid meoffgrid me Solar Expert Posts: 119 ✭✭
I recently bought a house in Maine that is off grid and am in the process of purchasing a PV system to run all my electrical needs. I just wanted to run it by you all to see if there are any glaring mistakes.
Important info
Location central Maine 45* latitude with a good southern exposure
Daily usage based on kill o watt meter and appliance ratings 4.3 kwh I have rounded this up in my math to 5kwh for future expansion.
System
20 205watt panels Voc22.3 Isc 11.93 4 strings of 5 ground mount @55* for best winter collection
Xantres 6048 inverter and system control panel
Outback fm80 mppt cc
450amp 48v battery bank
morning star 6 circuit combiner box and lightning arrester
misc breakers and disconnects for array, cc to battery, battery to inverter
17k generac propane standby generator.
I have already purchased the panels($1.67w shipped) and the generator
I was planning to use 4gauge copper from the array to the cc (200" round trip) do I need to also run #4 ground or can I install a ground rod at the array.
I am sure I will have many more questions as the system comes together

Comments

  • CariboocootCariboocoot Banned Posts: 17,615 ✭✭✭
    Re: pulling the plug

    Over-all, it looks like your system would work. A couple of observations and suggestions, though.

    First, have you looked at PV Watts http://www.nrel.gov/rredc/pvwatts/ to get an idea of what kind of solar harvest you can actually expect for your area?

    It seems you are basing your battery bank and array for 25% DOD, which is good. However, your array at 4100 Watts isn't likely to produce more than about 50 Amps output, so the FM80 is really overkill.

    Also, that 4 gauge wire run for 200 feet from the array to the charge controller is nasty. Have you done a Voltage drop calculation on it? www.solar-guppy.com/forum/download/voltage_drop_calculator.zip

    In light of those things, consider replacing the FM 80 with a MidNite Solar Classic 200 http://www.solar-electric.com/mnclassic.html That would allow you to run a much higher array Voltage and reduce the Voltage drop considerably. If I remember right, the MN Classic 200 will accept up to 248 Volts input. You could run your array as two strings of ten panels each. (If I've gotten confused about this someone correct me, please.)
  • PhotowhitPhotowhit Solar Expert Posts: 5,905 ✭✭✭✭✭
    Re: pulling the plug
    However, your array at 4100 Watts isn't likely to produce more than about 50 Amps output, so the FM80 is really overkill.

    Aren't you the one who always tells us those stories about the great frozen north and those wonderful days when panels produce their name plate or more?

    4000/48 (a long dark spell) >80

    Though I think the idea of the classic is excellent, and shows one of the ways that it will truely become a classic!
    Home system 4000 watt (Evergreen) array standing, with 2 Midnite Classic Lites,  Midnite E-panel, Magnum MS4024, Prosine 1800(now backup) and Exeltech 1100(former backup...lol), 660 ah 24v Forklift battery(now 10 years old). Off grid for 20 years (if I include 8 months on a bicycle).
    - Assorted other systems, pieces and to many panels in the closet to not do more projects.
  • stephendvstephendv Solar Expert Posts: 1,571 ✭✭
    Re: pulling the plug

    Regarding the Classic 200, it will work properly with a voltage of less than 200V. Between 200V and 248V it will stop charging, but won't burn out. More than 248V = smoke.
  • icarusicarus Solar Expert Posts: 5,436 ✭✭✭✭
    Re: pulling the plug

    General rule of thumb for off grid, take the name plate rating of the PV, divide that by two to account for all cumulative system loses, then multiply that number by 4 to represent the average number of hours of good sun one might likely expect on a daily bais over the course of the year.

    4100/2=2050*4=8200 wh/day.

    It is actually a bit worse in some ways. The first is that as the battery comes close to full, the controller will dial down, effectively losing capacity. The upside is that is a good time to time shift the discretionary power needs, like charging lap tops, tool batteries, running the crock pot etc.

    Tony
  • CariboocootCariboocoot Banned Posts: 17,615 ✭✭✭
    Re: pulling the plug
    Photowhit wrote: »
    Aren't you the one who always tells us those stories about the great frozen north and those wonderful days when panels produce their name plate or more?

    4000/48 (a long dark spell) >80

    Though I think the idea of the classic is excellent, and shows one of the ways that it will truely become a classic!

    Those days are rare and beautiful things. :cry: Maine is bound to be on the gray side much of the Winter, like the coast in BC.
  • offgrid meoffgrid me Solar Expert Posts: 119 ✭✭
    Re: pulling the plug

    I did a voltage calc and it said 2.4 % with #4 wire so this should be ok. Im still wondering about the grounding question. Any thoughts, I would love to only run 2 #4 wires @ $1 per foot. Being ground mount I do hope to be catching some reflected light from the snow and with the cold temps I may get close to rated output of panels in the winter hence the choice of the 80 amp cc. Central Maine actually has a higher insolation than Boston but yes there are a lot of grey days to contend with.
  • CariboocootCariboocoot Banned Posts: 17,615 ✭✭✭
    Re: pulling the plug

    With that kind of distance (200 feet) there should be no problem sinking a separate ground rod at the array site and running some 6 AWG to it from the panels. Normally a single grounding point is stressed, but that's so far as to be almost a different install! Remember it's for safety purposes, not functionality, so it should not be an issue.

    No doubt someone will disagree. Nothing starts lively discussions like grounding issues. :p
  • offgrid meoffgrid me Solar Expert Posts: 119 ✭✭
    Re: pulling the plug
    With that kind of distance (200 feet) there should be no problem sinking a separate ground rod at the array site and running some 6 AWG to it from the panels. Normally a single grounding point is stressed, but that's so far as to be almost a different install! Remember it's for safety purposes, not functionality, so it should not be an issue.

    No doubt someone will disagree. Nothing starts lively discussions like grounding issues. :p

    That 200 feet was total circuit length its about 100' to my garage/ pv room.
  • CariboocootCariboocoot Banned Posts: 17,615 ✭✭✭
    Re: pulling the plug
    offgrid me wrote: »
    That 200 feet was total circuit length its about 100' to my garage/ pv room.

    Still further away than the average neighbour's house in any city. ;)
  • Dave AngeliniDave Angelini Solar Expert Posts: 6,226 ✭✭✭✭✭
    Re: pulling the plug

    My free advice to you is to stick with Outback or Xantrex. Keep the system integrated as it was designed. These really are the only choices for people who are not guru's and like to play around with this stuff offgrid.
    "we go where power lines don't" Sierra Nevada mountain area
     http://members.sti.net/offgridsolar/
    E-mail [email protected]

  • icarusicarus Solar Expert Posts: 5,436 ✭✭✭✭
    Re: pulling the plug

    Why such big genertor? 17 kw is really pretty big given your PV size and battery bank size. My guess is that it may not e terribly fuel efficient since you are unlikely to load it above 50% capacity very often.

    Personally, I am not a big fan of generac units, but many have had good luck.

    Tony
  • offgrid meoffgrid me Solar Expert Posts: 119 ✭✭
    Re: pulling the plug
    icarus wrote: »
    Why such big genertor? 17 kw is really pretty big given your PV size and battery bank size. My guess is that it may not e terribly fuel efficient since you are unlikely to load it above 50% capacity very often.

    Personally, I am not a big fan of generac units, but many have had good luck.

    Tony

    I got it for a great price ($2500 with load panel and transfer switch new) and I figured the Inverter can take a 100amp continuous charge current. Should be good for a quick bulk charge in the mornings when needed. I can always use it for welding:D
  • offgrid meoffgrid me Solar Expert Posts: 119 ✭✭
    Re: pulling the plug
    Still further away than the average neighbour's house in any city. ;)

    Thats nothing. My property is over 1/4 mile long 8)
  • icarusicarus Solar Expert Posts: 5,436 ✭✭✭✭
    Re: pulling the plug

    100 Amos into 48 vdc is 4800 watts, add in charger loses, and you might be close to 1/3 of capacity. Fine for occasional charging, but if you are going to use it regularly, you are going to push a lot of waste fuel through it.

    T
  • BB.BB. Super Moderators, Administrators Posts: 32,800 admin
    Re: pulling the plug

    Also note that if you are planning on using 6kW/12kW surge from your XW 6048 inverter--You really should plan on 600 AH of battery bank at 48 VDC--Otherwise, limit your power to ~4.5kW/9kW surge...

    And I agree with Tony (Icarus)--You may wish to look for a genset about 1/2 that size or even a bit smaller (with propane conversion--if that make sense)... Perhaps, look in an RV Wreckers for a used Onan or other good quality genset.

    You probably will use 2x the amount of fuel per kWH generated if your battery bank is your primary reason for running the genset...

    If you have other loads (well pumping, irrigation, shop tools, etc.) that can be operated at the same time--then the large genset makes more sense to operate (fuel cost wise anyways).

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
  • SuperGreenSuperGreen Registered Users Posts: 18
    Re: pulling the plug
    BB. wrote: »
    Also note that if you are planning on using 6kW/12kW surge from your XW 6048 inverter--You really should plan on 600 AH of battery bank at 48 VDC--Otherwise, limit your power to ~4.5kW/9kW surge...

    And I agree with Tony (Icarus)--You may wish to look for a genset about 1/2 that size or even a bit smaller (with propane conversion--if that make sense)... Perhaps, look in an RV Wreckers for a used Onan or other good quality genset.

    You probably will use 2x the amount of fuel per kWH generated if your battery bank is your primary reason for running the genset...

    If you have other loads (well pumping, irrigation, shop tools, etc.) that can be operated at the same time--then the large genset makes more sense to operate (fuel cost wise anyways).

    -Bill
    I bought a 6500watt Propane generator it runs both 220 and 120 at the same time I get to run my water bottling plant and charge batteries at the same time works very well....the gen burns less than $2 per hour i love it.
    i own three battery chargers i could use some advice as to the best i can buy any recommendations
  • BB.BB. Super Moderators, Administrators Posts: 32,800 admin
    Re: pulling the plug

    If you are into the details of finding the "ideal" battery charger... Here is an example by "SteveK" that did that for his Honda eu2000i:

    Question about battery charger selection with EU2000 generator.

    Lots of good information there.

    -Bill

    PS: A recent thread about:

    Propane conversion kits

    -BB
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
  • offgrid meoffgrid me Solar Expert Posts: 119 ✭✭
    Re: pulling the plug
    BB. wrote: »
    Also note that if you are planning on using 6kW/12kW surge from your XW 6048 inverter--You really should plan on 600 AH of battery bank at 48 VDC--Otherwise, limit your power to ~4.5kW/9kW surge...

    And I agree with Tony (Icarus)--You may wish to look for a genset about 1/2 that size or even a bit smaller (with propane conversion--if that make sense)... Perhaps, look in an RV Wreckers for a used Onan or other good quality genset.

    You probably will use 2x the amount of fuel per kWH generated if your battery bank is your primary reason for running the genset...

    If you have other loads (well pumping, irrigation, shop tools, etc.) that can be operated at the same time--then the large genset makes more sense to operate (fuel cost wise anyways).

    -Bill
    I am a carpenter and plan to use the generator during construction of two additions that I have planned for the house. I will also be using it to power my shop. Maybe down the road when construction is complete I will look into a smaller unit just for charging purposes. I was looking at the xantrex 4548 but a solar guru reccomended the 6048 for its added capacity and minimal additional cost. The most I will be drawing at one time is 3500 watts unless I pull out the tools for some quick work and use the battery instead of starting the generator. Do think its a waste to spend the extra couple hundred on the larger inverter. I think they both have the same standby draw.
  • BB.BB. Super Moderators, Administrators Posts: 32,800 admin
    Re: pulling the plug

    No, it is not a waste--Just wanted to make sure that your loads and everything else is balanced.

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
  • halfcrazyhalfcrazy Solar Expert Posts: 720 ✭✭✭
    Re: pulling the plug

    Where in Central Maine I am in Central Maine as well and if you would like to see and play with any of this stuff you would be welcome to stop by and check out our off grid house I have a little of everything here including a few wind turbines. As well as a few Classic controllers.

    With those panels I would be tempted to go with a 200 volt Classic and wire them for high voltage to drop the wire size down.
  • peakbaggerpeakbagger Solar Expert Posts: 341 ✭✭✭
    Re: pulling the plug

    One word not mentioned - SNOW. If you are in central Maine, design the system to minimize snow deposition which generally menas less than ideal panel angles and make sure that you have an easy method to remove the snow when it inevitably collects on top of the panel.

    If you have multiple strings consider having one sacrificial string along the bottom row of the panels so that snow on the bottom of the array does not shut down all the strings.
  • offgrid meoffgrid me Solar Expert Posts: 119 ✭✭
    Re: pulling the plug
    peakbagger wrote: »
    One word not mentioned - SNOW. If you are in central Maine, design the system to minimize snow deposition which generally menas less than ideal panel angles and make sure that you have an easy method to remove the snow when it inevitably collects on top of the panel.

    If you have multiple strings consider having one sacrificial string along the bottom row of the panels so that snow on the bottom of the array does not shut down all the strings.
    Not to worry the bottom 2.5ft of racking is open and unused. It is ground mounted so snow removal should not be a problem. The panels are mounted at 55degrees for max winter production so snow should not collect on them. I have a camp up the road from where I am going to be living so I have been through a few maine winters. Thanks for the heads up though.
    Ned
  • Organic FarmerOrganic Farmer Solar Expert Posts: 128 ✭✭
    Re: pulling the plug

    Nice photo :)

    My immediate concern is the snow bank that may pile-up as it slides off the panels. I hope it worked out okay. I am in Penobscot county, and building mine to have a little more ground clearance.
  • nielniel Solar Expert Posts: 10,300 ✭✭✭✭
    Re: pulling the plug
    Nice photo :)

    My immediate concern is the snow bank that may pile-up as it slides off the panels. I hope it worked out okay. I am in Penobscot county, and building mine to have a little more ground clearance.

    you have a good point there as the runoff from 4 pvs in width will be sizable. a small snowfall could cover the bottom of the bottom pvs easily once it starts sliding down. the only consolation might be that it's all accessible.
  • offgrid meoffgrid me Solar Expert Posts: 119 ✭✭
    Re: pulling the plug

    No problems this last winter at all. I just plow across the bottom of the panels, and then hand shovel the small bit thats left. I have clear access on all 4 sides so clearing the snow away is easy. The panels are set to 55degrees so not much snow collects on them. I use an 18" squeegee attached to a long pole to pull any snow that sticks off the panels. The rest melts away as soon as the sun pokes out.
    Ned
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