what is max distance in feet that i can run 2 wires from solar array to my cabin

offgridcabin2015

Hello experts. 

I will be building a 2000 watt array  four panels (q cells) wired in series and fused to combiner box to outback flex max 80.

the idea is to wire up the four panels to combiner box mounted  beneath the array (to save on wire) not really wanting to run all wires back to cabin . 

so the 2 wires left over from the array (out of the combiner box) to cabin  52 feet. 

is that acceptable?

Photowhit

We can look up the capacity for voltage on the FM80, but we don't know the specs on the solar panels VMP VOC and IMP.

If 72 cell panels, likely run them in 2x2 -  2 in series and those 2 in parallel, Then the issue will be allowable voltage drop. Running thick enough cables you can run a very long distance. Looks like you might have the 150 half cell panels with a VOC 51.7, VMP of 42.8 and an IMP 12.2.

2x2 should give you 2 strings with a VOC of around 104 volts and vmp of 85.6 and imp of 12.2 each and combined 24.4 amps.

104 volts should be under the FM80's 150 max voltage, 24.4 amps on 10 gauge wire for 60 feet (I like a little wiggle room, often the distance from the panel is ignored rather than from the combining box Which WOULD NOT BE NEEDED, rather you could just use 'Y' connectors. If it's a known area USE 2 wire can be directly buried without conduit.) would be a 4% voltage drop when pulling max from the array (which rarely if ever happens) I would call that acceptable. The difference in cost to go to 8 gauge wire would be very high.

offgridcabin2015

wow. Thankyou photowhit. 

1) i already have the combiner box. would just makes saftey since to install it 
    b) i had no idea how to wire that array without the combiner box.

2) correct me if i'm wrong , i was told the fx 80 like the volts rather than amp. meaning i'm to wire in series ONLY.   but if you suggest to do do 2x2, that means i'll need one 30amp breaker for that one pair of panels in parallel.   That's okies i can buy that. 

but seem that it's a go then. Thankyou for your wonderful help. 

anyone have any wiring tips for the Schednider 24v  4024?    I just have the inverter . (not buysing the ac / dc boxes) way to expensive for me. and my other inverter didn't have any of that . I just wire in fuse for batts and cut off turn dial manual switches for bats and each inverter has it's own cut off.

Note : i leave system off when at work and only turn on when home.

Thankyou so MUCH!!!

ps . not sure if q cells are 72 cells are not . but found chart for you.

Photowhit

offgridcabin2015 said:

2) correct me if i'm wrong , i was told the fx 80 like the volts rather than amp. meaning i'm to wire in series ONLY.   but if you suggest to do do 2x2, that means i'll need one 30amp breaker for that one pair of panels in parallel.   That's okies i can buy that. 

The FM80 has a maximum voltage of 150 volts.

So in series the 4 panels would be VOC of over 200 volts, so that would fry it.
A quick glace at the spec's look like the 150 cell panels, which I think is wired like 2 groups of cells in parallel. I think they are the specs from the panels I was looking at earlier.

When panels were expensive ($5+ per watt) we shot for less than 2% voltage drop. But I think the max going through the wiring and the rarity of the max as well as being well within the specs for 10 gauge as well as the large difference in price I'd stick with 10 gauge. Others will likely be along to check my work. I made a mistake once back in '72...lol (actually multiple times per hour is more likely).

I understand wanting to keep costs down, but get DC rated fuses! A DC breaker box which comes with a 175 amp DC breaker for your Inverter (Check specs, I think this would be correct) Would make a clean installation. It's nice to not see all the wires running all over the place and exposed connections. $267 list, might be cheaper if I/you sign in. It also has a DIN rail to mount your incoming solar and out going power from the charge controller to inverter and grounding busbar.

Mini - DC Disconnect Power Center with 175 Amp Breaker | Northern Arizona Wind & Sun (solar-electric.com)

offgridcabin2015

Thankyou . 

I want to go over the numbers with you based on the yellow circle above as those are my exact panels and i'll be following the Normal Chart NOT the stand test conditions. ok?

Here is my math i will show my work and my train of thought. 

VOC is 50.56 . So based on your advice of 2 panels in series that's 50.56*x2 is 10.12 so i'm good as flex max 80 does 150v .

isc short circuit is 9.07 x 1.25  fer cold is 11.3 so 15amp dc breaker / right?

Next 2 panels in paralell  , IMP is 8.43x2 as when in par (double amp , and volts STAY the same) so that is 16.86 x 1.25 for cold is 21.0 so either 25 or 30 dc breaker correct. 

So i can add that to my combiner box with  25 ( if they make em) or / 30  dc breaker . done.

Photowhit

offgridcabin2015 said:

isc short circuit is 9.07 x 1.25  fer cold is 11.3 so 15amp dc breaker / right?

I would use the series fuse they recommend for the panel. Looks like 20 amp in their manual;

Q_CELLS_Installation_Manual_Q.PEAK_DUO_XL-G10.2_G10.c_modules_series_2021-07_Rev01_NA (2).pdf

I would wire the combined lines with a 30 amp breaker, but you could go up to 40 amps with most wires. After they are combined, it's onlt the wires you are protecting.

Might consider a breaker between the charge controller and the inverter. It might help if you need to troubleshoot problems.

706jim

I have three panels located about 100' from my cabin (as well as a separate circuit with four more). I ran #14 wire using your standard house wiring to and from the controller. That is, the white, black and plain (uninsulated) ground conductors are paralleled together giving the equivalent of about a #8 or #10 wire going each way. Where it meets up with the second array, the wire size increases to #8 tripled which should be more or less equivalent to #4. Works just fine at that distance. All panels are in parallel giving me about 44 volts at the charge controller (and FM80) and a maximum as much as 70 amps. Nominal battery voltage is 24.

If you have to meet some legal wiring code, this setup is not for you but it works fine where I'm located on a remote island.

offgridcabin2015

hi 706jim i may try this can you provide me some sort of sketch plz  and thankyou. 

706jim

I will if I can figure out how to post an image on this forum. Haven't done it here before.

littleharbor2

706jim said:

I will if I can figure out how to post an image on this forum. Haven't done it here before.

There's a little photo icon above the comment line. Click on that and add a photo or scanned image of your drawing.