Maximum oversizing an SMA Tripower 4.0

[akke]

Hello,

I want to add more panels on my roof but local regulations won't allow me to go past a limit of 10kW of total inverter power.
I already have an SMA Sunny Boy 2.0 on a separate circuit (garden house) and 2x SMA Tripower 4.0 inverters for the panels on my house.

The Sunny boy 2.0 circuit will be left unchanged but I want to add more panels to my Tripower 4.0 inverters.

Right now I have:

Inverter 1:
String A: 9x 355Wp
String B: 8x 355Wp

Inverter 2:
String A: 8x 355Wp
String B: 8x 355Wp


Now I want to add 6x 375Wp and 8x 425Wp panels and I wanted to connect it like this:

Inverter 1:
String A: 16x 355Wp
String B: 1x 355 + 6x 375Wp

Inverter 2:
String A: 16x 355Wp
String B: 8x 425Wp


All panels do have a Tigo TS4-A-O optimizer. So it shouldn't be a problem for the 355Wp to be connected in series with the 375Wp panels, right?
I can't do 17x355Wp because the voltage for that string will be higher than 750V, which is not allowed in Belgium.


If I add this in Sunny Designer, it's not throwing any errors. (see attachments).
So, I guess it's okay to do so?

The panels will be oversized quite a lot; That's why I prefer to get your opinions before I start working on it already..

Does it sound okay to do?

 

[akke]

Anyone?

 

[akke]

It looks like I’m alone here, talking to myself ?
Where is everybody? Moved to a better place that I don’t know of?

 

[akke]

wtf

 

[billt1827]

Not sure what your question is.
If Sunny designer says that it's OK then I'd say that it is OK.

 

[akke]

I wanted to double check if it is in fact okay. I will be oversizing it by quite a lot and maybe I’m not thinking about something that could be a problem.

On the other hand. If Sunny Designer says it is fine it should be fine, like you said…

 

[Hedges]

Never exceed max Voc, even when adjusted higher for record cold, according to temperature coefficient of PV panel.

High Imp and Isc is OK, but exceeding max short circuit current would be a problem if you connected array backwards (clamping diode would overheat.)

If you connect different panels in series, estimate voltages add but lowest current panel will determine current from all panels. Should be fine with 5% to 10% difference in current, but if 30% to 50%, excessive current could damage bypass diodes in panels.

I like to connect two PV strings of same/similar voltage in parallel, but orient them differently. You can do the same with different orientations as separate strings/arrays into separate MPPT inputs. For some inverters, e.g. US model Sunny Boy -41, MPPT A and MPPT B can be paralleled (but not MPPT C). that gives more flexibility on max current.