Over panelling question

[FMaz008]

Hello!

I'm from Canada. I had a solar array professionally installed a few years back:
- 22 Longi 430w panels (specs attached)
- Connected as 2 strings to a
- 10kw Fronius Primo Inverter (Specs)

I'm looking at adding 6 panels. What's available locally are QPeak 480w panels. (Specs attached)

My idea would be for String 1 to have 14 Longi panels and string2 would have 8 Longi panels and the 6 new panels.

As I understand, the new panels would operate at 430w.

I've requested a quote for this expansion, and I was quoted 10k CAD, for 6 panels. As a reference, the entire setup costed me 17k. Inflation they said before reducing their price to 8k.

So I'm looking at doing it myself, but I'm struggling to find good info regarding overpanelling.

Is my plan sound? Are there pitfalls I should be careful about?

I'm honestly not too sure what question to ask.

I feel confident in doing the physical mounting of the pannels onto the roof. But the electrical part worries me.

For one: can the inverter handle 6 more panels? I'm assuming yes since that's what they quoted me.

For two: is it just a matter of reconnecting panels to make the new strings and grounding the new section to the existing one?

 

[12VoltInstalls]

You have to factor maximum series fuse ratings, and personally I’d make the new panels have their own SCC and leave what’s working stay in harmony with itself. You can only use the watts not the grouping. My opinion. Ymmv

 

[FMaz008]

You have to factor maximum series fuse ratings, and personally I’d make the new panels have their own SCC and leave what’s working stay in harmony with itself. You can only use the watts not the grouping. My opinion. Ymmv

I'm not sure I'm following about the SCC part. My panels don't have microcontrollers (if that's what we are talking about)

I'm all for creating a 3rd string, but the inverter only has 2 MPPT inputs.

 

[12VoltInstalls]

I'm not sure I'm following about the SCC part. My panels don't have microcontrollers (if that's what we are talking about)

No, a Solar Charge Controller. It’s what us built in to your:

I'm all for creating a 3rd string, but the inverter All In One only has 2 MPPT inputs.

An inverter takes DC aka battery voltage and converts it to 120- or 240AC voltage.

Your unit with “2 MPPT inputs” is likely a machine that contains one or sometimes two Solar Charge Controller(s), an inverter, often an AC transfer switch, and typically a utility battery charger. Known usually as an All In One (AIO) or ‘hybrid inverter.’

Since the two existing strings are balanced and working, I suggested adding an SCC to handle the new panels only. This keeps things balanced and adds amp capacity from the panels if your existing panels are at or near maximum capacity for solar charging.

What you refer to as “microcontrollers” I believe you actually mean as microinverters which take DC panel voltage and invert it ‘locally’ at one or several panels before sending that AC voltage to whatever distribution/grid tie device. That’s not what I was referring to.
I hope this has adequate details and makes some sense.

 

[FMaz008]

No, a Solar Charge Controller. It’s what us built in to your:

An inverter takes DC aka battery voltage and converts it to 120- or 240AC voltage.

Your unit with “2 MPPT inputs” is likely a machine that contains one or sometimes two Solar Charge Controller(s), an inverter, often an AC transfer switch, and typically a utility battery charger. Known usually as an All In One (AIO) or ‘hybrid inverter.’

Since the two existing strings are balanced and working, I suggested adding an SCC to handle the new panels only. This keeps things balanced and adds amp capacity from the panels if your existing panels are at or near maximum capacity for solar charging.

What you refer to as “microcontrollers” I believe you actually mean as microinverters which take DC panel voltage and invert it ‘locally’ at one or several panels before sending that AC voltage to whatever distribution/grid tie device. That’s not what I was referring to.
I hope this has adequate details and makes some sense.

Wow, thank you so much for this detailled and extremely helpful answer! It really clarified things for me.

So in other words, it would be possible to add a new string of panels, with their dedicated solar charge controller, and took that up to the inverter part of my AIO hybrid inverter.

Am I following your thoughts process right?

If so, what input of the AIO will the SCC typically plug into?

 

[Q-Dog]

Does your setup have batteries? Isn't the Fronius a grid-tie string inverter?

 

[FMaz008]

Does your setup have batteries? Isn't the Fronius a grid-tie string inverter?

No battery. It is grid tied, yes.

 

[Q-Dog]

I don't know much about Fronius. Perhaps you can contact them and see if they have a recommendation on overpaneling. Does your grid tie agreement with the power company allow you to add more capacity?

All the stuff about Solar Charge controllers don't apply to you since you don't have any batteries to charge.

 

[12VoltInstalls]

So in other words, it would be possible to add a new string of panels, with their dedicated solar charge controller, and took that up to the inverter part of my AIO hybrid inverter.

Am I following your thoughts process right?

No- the additional SCC connects directly to your battery busbar, not the AIO

 

[12VoltInstalls]

thank you so much for this detailled and extremely helpful answer

?
Well please make sure you fill out my positive feedback survey. I’m working on qualifying for the $2500 participation bonus

 

[Q-Dog]

No- the additional SCC connects directly to your battery busbar, not the AIO

OP does not have batteries ... Grid tie only.

 

[SamDeleted]

I'd get whoever gave you that 10k quote to explain their plan , and then just copy it

 

[FMaz008]

I'd get whoever gave you that 10k quote to explain their plan , and then just copy it

That's what I was thinking of doing. And what I described. But 12VoltInstalls seems to say it's a bad idea to mess with the existing strings.

I'm trying to clarify how his suggestion can be implemented in my grid-tied setup.

 

[SamDeleted]

That's what I was thinking of doing. And what I described. But 12VoltInstalls seems to say it's a bad idea to mess with the existing strings.

I'm trying to clarify how his suggestion can be implemented in my grid-tied setup.

Well I'd HOPE you could trust your professionals ?. They are trying to charge top dollar , so surely they know what they're doing????

 

[Q-Dog]

That's what I was thinking of doing. And what I described. But 12VoltInstalls seems to say it's a bad idea to mess with the existing strings.

I'm trying to clarify how his suggestion can be implemented in my grid-tied setup.

His suggestion can't be implemented because you don't have batteries. (But you could add an off grid or hybrid inverter and batteries. Is this what you want to do?)

You already have over 9000 watts going into a 10K string inverter. So, You need to find out if your Fronius can be overpanelled and if so, how much.

If it can be overpanelled, what are you hoping to accomplish? If the inverter can handle your proposed almost 3000 watts of more panels, those panels are mostly wasted if the Fronius can only pass through 10k watts.

And there is still the question of will your power company let you inject more power into their grid? Or will you have to consume the extra power as you make it?

 

[Hedges]

How are panels oriented?

9000W of panels could produce 6300W peak and have extended hours of production, if the array was two strings about 90 degrees apart (e.g. due West and due East, each 45 degree slope.) Then inverter would not be overpaneled.

You may be able to put two (identical length/voltage) strings in parallel into a single MPPT input. Depends on how much current they produce. Again, multiple orientations would reduce peak current produced.

It is best of all panels in a single series string are same current.
And best if two strings in parallel are same or similar voltage.

 

[12VoltInstalls]

How are panels oriented?

9000W of panels could produce 6300W peak and have extended hours of production, if the array was two strings about 90 degrees apart (e.g. due West and due East, each 45 degree slope.) Then inverter would not be overpaneled.


best if all panels in a single series string are same current.
And best if two strings in parallel are same or similar voltage.

But 12VoltInstalls seems to say it's a bad idea to mess with the existing strings.

I meant that they are in harmony and every panel in the string is the same as noted by hedges

I'm trying to clarify how his suggestion can be implemented in my grid-tied setup.

Does your gridtie device not support batteries? I guess I’m stuck on the mindset of batteries and assumed you had a complete system. Foreign idea to me to have a gajillion watts of panels and be dead if the grid is out.