Adding panels to existing microinverter residential system.

[MPSTAPLES]

I have an existing residential system working with PG&E. It was designed using microinverters with the intent of adding 6 panels at a later date. Now is the later date but I would like to add them myself rather than going back to the original installation company. I understand the warranty might suffer if I add the 6 panels myself. System has been working find for over a years. No leaks. I'm willing to take the chance. I have spec'd out the hardware, matched the out put of the new panels, ordered the new microinverters, and will order the rail system soon. I'm assuming the original installation company will simply turn their nose up at me if I ask them to simply come out and hook the new panels up to the existing system.

I'm assuming that because the original system was put in with microinversters, the panels were wired in series. Is this a good assumption? Are there any big issues I should watch out for? I'd love to find a consultant that would help me out, but I've done searches for my area and don't see anyone. They are all companies -- who want the whole business or nothing.

 

[Hedges]

Microinverters means panels are isolated from each other, put their DC (maybe about 36VDC) into their microinverter which produces 120VAC or 240VAC.
The AC output of the microinverters are wired in parallel.

More microinverters of the same model, within whatever total quantity manufacturer specifies, should be easy to connect.
(I don't know about mix/match of different model same brand inverter, depends on what vendor says is compatible)

 

[MPSTAPLES]

Hedges, thank you for the reply. I was just watching a youtube on the installation of the enphase microinverters (which is what I will install). It actually looks easier than I thought. It's a plug and play thing that is wired in parallel. I don't see any way to wire it any differently even if you wanted to. Thank again.

 

[solar8484]

I believe PG&E only allows for 1KW add-on for the same permit so you may want to make sure adding 6 panels does not violate your PG&E permit.

 

[Hedges]

I believe PG&E only allows for 1KW add-on for the same permit so you may want to make sure adding 6 panels does not violate your PG&E permit.

Depending on model, 4 microinverters could be 1kW.

Me, I would consider two PV panels in parallel into each inverter. If oriented differently (AM vs. PM sun), that give more hours production with lower peak wattage than if both oriented the same. I think this works best if sum of the two panels rated are about 50% to 70% above inverter rating.