two strings on same MPPTs, are they connected?

[Gareth J]

Am looking at buying a Solis 8kw single phase inverter but am wondering about the DC side of things. It's odd, as it has two MPPTs, one with one string at 12.5A and one with two strings at 25A total.

I want to simplify the wiring, particularly as I already have the right wire to do so and, if possible, run just two pairs of cables. There is no issue with shading.

So, will the strings on the dual stringed MPPT be connected inside the inverter you think? So I can effectively run the two strings down one pair of cables?

Not sure if there are terms I can search for that I'm missing.

[MoSTiE]

i've just looked a 2 Solis 8K data sheets and they are both different, this one is probably your best bet

https://www.itstechnologies.shop/produc ... r-inverter

[Stinsy]

Am looking at buying a Solis 8kw single phase inverter but am wondering about the DC side of things. It's odd, as it has two MPPTs, one with one string at 12.5A and one with two strings at 25A total.

I want to simplify the wiring, particularly as I already have the right wire to do so and, if possible, run just two pairs of cables. There is no issue with shading.

So, will the strings on the dual stringed MPPT be connected inside the inverter you think? So I can effectively run the two strings down one pair of cables?

Not sure if there are terms I can search for that I'm missing.

What panels are you installing and how many?

[Gareth J]

24x 415W Suntechs

[Tinbum]

More importantly what are the voltages on the two strings?

[Gareth J]

More importantly what are the voltages on the two strings?

Of course!

That will explain. I'm out at the minute but will check later. It's almost certainly going to be expecting separate strings of ~ 3300Wp. But whether or not the twin string MPPT can be fed with one string of ~6600Wp or can be connected in series, to split the load is I guess a question for solid. Would much prefer a simple one string per MPPT machine but finding one that's G100 at ~8kw is proving tricky.

[Stinsy]

24x 415W Suntechs

So Voc = 38.33V and Imp = 13.06A

If you put them all into a single string then you'd have a string voltage (Voc) of 919.92V and current (Imp) of 13.06A, the Voltage is in excess of the inverter's 600V max and you will definitely let the smoke out if you do that.

If you parallel up 2x strings of 12 panels you'd have a string voltage (Voc) of 459.96V and a string current (Imp) of 26.12A. This is what I'd recommend you do. Hook them up to the "25A" MPPT, don't worry about the current of the panels being higher than the inverter rating, it is a bit like plugging a 3A lamp into a 13A socket, you'll lose a smidge off the top in ideal conditions but only a teeny bit and ideal conditions don't occur very often.

You can leave the "12.5A" MPPT for future expansion.

[Gareth J]

24x 415W Suntechs

So Voc = 38.33V and Imp = 13.06A

If you put them all into a single string then you'd have a string voltage (Voc) of 919.92V and current (Imp) of 13.06A, the Voltage is in excess of the inverter's 600V max and you will definitely let the smoke out if you do that.

If you parallel up 2x strings of 12 panels you'd have a string voltage (Voc) of 459.96V and a string current (Imp) of 26.12A. This is what I'd recommend you do. Hook them up to the "25A" MPPT, don't worry about the current of the panels being higher than the inverter rating, it is a bit like plugging a 3A lamp into a 13A socket, you'll lose a smidge off the top in ideal conditions but only a teeny bit and ideal conditions don't occur very often.

You can leave the "12.5A" MPPT for future expansion.

That's interesting. And better than than my idea, which was;
To split the 24 panels into 3x8 panel strings.
Give 12.5A MPPT one string.
Combine the other two strings at the roof (In series I guess - I imagine paralleling might to horrible things if there is a potential difference between "equal" strings)
Feed the 25A side with either just the one, combined string (which is, as you point out over voltage anyway) or series the two inputs so the voltage of the combined string is shared between the two inputs. But who knows if the inverter will like that.