3-Phase Fronius Inverter

Hi all

I need some assistance on information from two different sources, but about the same product.

They have both quoted to use Fronius 10.0-3-M
Quote 1: Total of 36 panels on three faces (east, north, west; east & west have 8 panels each)
Said we don’t need any optimisers or micro-inverters as we will generate power pretty much from sunrise to sunset

Quote 2: Total of 36 panels:- 6 on east; 14 on north; and 16 on west
This company stated we NEED optimisers to get 3 strings into 2, so we can connect it to the Fronius inverter, or lose the east panels and stick with 2 strings

Both quotes are similar in price, but Quote 2 says we need 6x optimisers at ~$120 each

System size is 13.3kW with the 10kW inverter, as mentioned above.

If anyone can shed some independent knowledge on this, please help.

Hi @jtm_bne_19

That’s an interesting one. Have you got designs from either or both of them that we could look at? What panels are they both proposing to use?


Thanks @Marty

I will try and get the designs on here in the next few days. As for the panels:

  • Quote 1: 370W Trina Solar Honey M (x36)
  • Quote 2: 370W Seraphim Energy Group (x36)

Quote 2 mentioned no matter what panels we get, we need to get 3 strings down to 2 for the Fronius inverter input, and the only way to do that is with optimisers.

There is a bit of a quirk with this one. Whilst the inverter does only have 2 MPPT inputs, and normally you can only have panels facing the same direction using a single MPPT input (i.e panels facing only two different directions in total). However, if you have panels facing the opposite direction to each other (I.e east and west), these can also go into the same MPPT input.

Don’t ask me the technical reasons behind it, but it is a thing, you can see more here:

I was surprised to learn this recently, so I’m not surprised that the installer is not aware, but you could point them to this thread.

Hope that helps,