Need input on noob's 19kWh array design - will this work?

[gator11]

Hi, I’m in the early stages of researching/planning a future gird-tied/net metered residential PV array. It will be on the larger side for residential. I am in FL, and I have a nice sunny spot that I’ve measured at 900-1000w/m^2 for hours at a time where the panels will be installed on a purpose-built pavilion with ideal southern exposure and azimuth angle. I have a rough idea what I would like to do, but need some input on if it is feasible and/or what other hardware I will need to end up with a commissionable Enphase system…

40x 590w panels (Q-cell, may change)

40x IQ8P (240v), 475w max continuous AC output (although, have only been able to find the 3P versions here in the US so far – hopefully the IQ8P’s are sourceable)

125 AMP PV input subpanel w/ 5x 20A branch PV circuits (8 PV/IQ8P’s per breaker)

125 AMP breaker in main panel, fed from PV subpanel

A Gateway somewhere in the mix, not sure where, but seems like it will find all IQ8’s as long as it’s in the loop somewhere?

Also, I should probably mention, the only reason I chose to leave out a Combiner Box 4/5 is that it seems (again, if I’m understanding correctly) that it’s just a nice-to-have clean aggregation of PV input subpanel, gateway, and a few other non-critical bells and whistles – not to mention the main breaker on it is 80A – so at 40*475w IQ8P’s I could be at near 100% load on the Combiner Box since its main is 80A @ 240 – which seems less than ideal (for my system, 100A+ would be more suitable, of course).

Then, if I understand, it seems like the IQ8’s ship in interactive (anti-islanding) mode, so I guess I don’t need a System Controller unless I intend to add a battery down the line? Or am I totally misunderstanding?

And if I do choose to add a battery down the line, can I add in the System Controller 3 (placed between meter & panel mains) and battery at a later date?

If so, assuming I sandwich my System Controller 3 between the utility meter & panel mains (I have 2x 200A panels with their mains on the outside wall, and the load panels on the inside garage wall) - will the System Controller 3 properly work that way (as an ATS/islander/battery manager), or would I have to rewire things? And if that’s where the SC3 is placed, since it would be ahead of my current neutral/ground bond, I assume I would need to unbond the original main panels, and create the bond at the SC3?

I’m a complete noob to this solar stuff, please tell me what I’m missing. Thanks!

 

[BentleyJ]

You will need some kind of combiner box because the Enphase cables are limited to the number of microinverters that can go on a 20A circuit. Also should have the Enphase communication device which comes installed in the Enphase combiner box.

What is the amperage rating of the breaker panel you are going to feed into? Your proposed 40 panel system will have an STC rating of 23.6kW. That's 98Amps so the breaker panel has to be sized based on the 120% rule.

For example, a 225A panel (bus bar rating) down graded to a 175A breaker can still only accept 95A of solar.

 

[gator11]

Okay, thank you for the reply!

So my understanding was that I could use a subpanel to aggregate the PV array circuits in 20A groups (8PV's per group/circuit), and then use a standalone Gateway device for management. Are you saying the IQ8P inverter circuits won't work that way, and I must use a Combiner Box with built-in Gateway? In which case, I'd need two Combiner Boxes for this setup?

Regarding the amp rating of the PV subpanel I was planning (125A PV subpanel main breaker, with 5x 20A circuits each w/ 8PV/IQ8's connected via IQ-12AWG wire from the array - then the 125A sub panel main will be tied into a 200A main panel via a second 125A breaker in the main panel).

I guess this may be moot if I can't use my own subpanel to tie in the PV circuits... But my thought was the max DC current of the PV's would be irrelevant since the inverters would only ever send a maximum AC current of 480w@240v per inverter * 40PV's=19,200watts. So the maximum (albeit clipped) load into the subpanel would be 19,200w/240v = 80A. So in my mind I was oversizing the 120% rule by a little bit by using the 125A breakers.

Am I way off here?