Install Advice

larrybc1
larrybc1 Solar Expert Posts: 44 ✭
in Off Grid Solar & Battery Systems #1
Hi all...Just wanted to make sure I am on the right track..I have 25 evergreen 210 watt panels that I am going to put together as follows:
2 strings of 5 panels in series to one fm80 controller and 3 strings of 5 in series to the other controller--the specs check out fine on the voc and vmp..
I have 2 combiner boxes..
so in each series of 5 panels i connect the positive of one panel to the negative of the next panel..and then run the combined positive and negative wire to the combiner box..and do this for each series..then I figured to use awg 2 or 4 wire to make the run from the combiner box to the charge controller--about 75 feet..thks for the help..larry
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  • Cariboocoot
    Cariboocoot Banned Posts: 17,615 ✭✭✭
    #2
    Re: Install Advice

    This had better be a 48 Volt system with 3150 Watts on one FM80.

    Series string of panels: (+) to (-) 'til you get 'em all connected.
    These are the "12 Volt" Evergreens? String Vmp @ 87.5 and Imp @ 12?
    If so your two string set will have an Imp of 24 and the three string set an Imp of 36.
    Get those combined current numbers and do a V-drop check on the wire size for the 75' run from combiner to controller. The two string set would work with 6AWG (unless you plan on adding a third later) and 4AWG should be fine for the other. But double check this before buying a lot of expensive wire.

    Someone is bound to suggest some other configuration possibilities involving higher array Voltage and smaller wire. But I don't see how without dropping or adding panels. Whatcha need a 5250 Watt array for anyhow? :p That's good for about 842 Amp hours @ 48 Volts or up to 20 kW hours stored capacity!
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  • niel
    niel Solar Expert Posts: 10,300 ✭✭✭✭
    #3
    Re: Install Advice

    larry,
    this you may already know and it may be a review for you. with 2 controllers you need to separate those pvs so they are only to one cc. that means 2 totally separate solar systems feeding to the same battery and therefore 2 pv combiners and 2 separate home runs to their prospective ccs. either #4 or #2 will suffice for 2 separate runs for a 48v battery bank, but you cannot combine them into a single home run.

    also, depending upon how cold it gets at your place you could be in danger of coming close to the max operating voltage of the cc. the mx60 as i recall was in the area of 135v or 140v and i'm not sure if that is the same for the fm series now or not. others can be more specific on this.
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  • vtmaps
    vtmaps Solar Expert Posts: 3,741 ✭✭✭✭
    #4
    Re: Install Advice
    niel wrote: »
    with 2 controllers you need <snip> and therefore 2 pv combiners and ....

    Niel, in the OP he said that he had two combiner boxes. I also was wondering if he knew that he needed two home runs to the two controllers... he didn't mention that explicitly. --vtMaps
    4 X 235watt Samsung, Midnite ePanel, Outback VFX3524 FM60 & mate, 4 Interstate L16, trimetric, Honda eu2000i
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  • Cariboocoot
    Cariboocoot Banned Posts: 17,615 ✭✭✭
    #5
    Re: Install Advice

    FM60/80's max input Voltage is the same as the MX60 series: 150. It shuts down before that (different MX60's had different shutdown Voltages).

    This is an important point as some Evergreen 210 Watt panels have a Voc of 23.1 and some 22.8: multiply by five and you get 115.5 and 114 respectively. Throw in cold weather and it could be a problem, depending on which panels and how cold. Up here the 23.1 version would be shutting down the controller frequently during Winter.
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  • niel
    niel Solar Expert Posts: 10,300 ✭✭✭✭
    #6
    Re: Install Advice
    vtmaps wrote: »
    Niel, in the OP he said that he had two combiner boxes. I also was wondering if he knew that he needed two home runs to the two controllers... he didn't mention that explicitly. --vtMaps

    i did say much of that is review just so we were on the same page as i led up to it with a train of thought. i am hoping he meant for 2 separate home runs back to the ccs and had to be sure.

    marc,
    a 55 degree c differential is not unreasonable for the lowest it has gone to for my area so the 55 degrees at .0034% per degree c means a 18.7% increase so the voc of each pv at 22.8v x 5 = 114v. 114v x 1.187 = 135.318v.

    oops my error as evergreen lists .0031% for the voc, but it's still close.
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  • Cariboocoot
    Cariboocoot Banned Posts: 17,615 ✭✭✭
    #7
    Re: Install Advice

    Yes, and we don't know precisely which Evergreen panel it is. Like I said, I found two "210 Watt Evergreen" panels with quite different ratings on them.

    That's why it's always best to have the particular panel's specs. :D
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  • larrybc1
    larrybc1 Solar Expert Posts: 44 ✭
    #8
    Re: Install Advice
    niel wrote: »
    larry,
    this you may already know and it may be a review for you. with 2 controllers you need to separate those pvs so they are only to one cc. that means 2 totally separate solar systems feeding to the same battery and therefore 2 pv combiners and 2 separate home runs to their prospective ccs. either #4 or #2 will suffice for 2 separate runs for a 48v battery bank, but you cannot combine them into a single home run.

    also, depending upon how cold it gets at your place you could be in danger of coming close to the max operating voltage of the cc. the mx60 as i recall was in the area of 135v or 140v and i'm not sure if that is the same for the fm series now or not. others can be more specific on this.
    Hi Niel..I have 2 fm 80 charge controllers and 2 combiner boxes..so will run the 2x5 to 1 box and then 1 charge controller and then the 3x5 to the other combiner box and cc..so they are both seperate systems and seperate home runs..so #4 or #2 will work?..will be a 48 volt syste..no probelm with temperature as I am in the Philippines and no cold temps.
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  • larrybc1
    larrybc1 Solar Expert Posts: 44 ✭
    #9
    Re: Install Advice

    hi Cariboocoot..I will be in the Philippines so no cold weather probems..voc is 22.8.
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  • niel
    niel Solar Expert Posts: 10,300 ✭✭✭✭
    #10
    Re: Install Advice

    larry,
    correct either wire gauge will work and of course #2 works at lowering losses better than #4 so if you can, go #2, but #4 will suffice if costs of the #2 is enough of a factor. keep in mind you will have losses in the wires from the pvs to the combiners and from the ccs to the batteries as well and these losses are additive to the losses of the home runs for the entire system loss. the one with 3 strings in it will show the most losses due to higher currents flowing in the wire and if you want to, you can place the #2 on this home run while the other 2 stringer home run gets #4.

    also know the 3 stringed one will need fused at each pv string input to be combined.
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  • larrybc1
    larrybc1 Solar Expert Posts: 44 ✭
    #11
    Re: Install Advice
    niel wrote: »
    larry,
    correct either wire gauge will work and of course #2 works at lowering losses better than #4 so if you can, go #2, but #4 will suffice if costs of the #2 is enough of a factor. keep in mind you will have losses in the wires from the pvs to the combiners and from the ccs to the batteries as well and these losses are additive to the losses of the home runs for the entire system loss. the one with 3 strings in it will show the most losses due to higher currents flowing in the wire and if you want to, you can place the #2 on this home run while the other 2 stringer home run gets #4.

    also know the 3 stringed one will need fused at each pv string input to be combined.

    Ok so i need to put a fuse on the 3 string one PRIOR to the combiner box? The combiner box has the fuses in it?? Exactly how will this be done..thks for the info larry
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  • niel
    niel Solar Expert Posts: 10,300 ✭✭✭✭
    #12
    Re: Install Advice

    good as not all boxes utilize fuses or breakers. each string will attach to a fuse in the box and from there go to be combined.

    technically the 2 string box is not required to be fused, but it doesn't hurt anything either.
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