multi-azimuth installation

[maricopa]

Hello,

I just found this forum today and have spent some time searching for an answer to my question, but no luck.

I am looking at a residential grid-tied system, and have had a couple of companies come out and measure. We have a complex roof (multiple dormers) so the maximum system size is limited.

One company proposes two arrays - one south facing and one west facing. I know the west facing one will be of less use in the morning, but I'm also concerned about the use of a single inverter. I've heard and read that two arrays feeding a single inverter must be generating close to the same amount of power, otherwise the lesser of the two is essentially shut off/unused.

When I questioned the company on this, they said that their Fronius inverter is more advanced and can handle this scenario and allows both arrays to be used regardless of whether they are operating at similar levels.

Does anyone have any insight into this? I searched Fronius' site but didn't really see any spec or feature that relates to this.

Thanks!

[Mike90250]

If they are wrong, you get to buy a 2nd inverter from them.

There is actually no way, a inverter, can track 2 different array orientations, unless it has 2 MPPT units, one for each input. Or unless it has a multi-day learning program. (none do, you are hearing sales pitch BS) What is possible, is 2 strings, closely matched, on one inverter.

You can use the PV watts site for your location and array, and run 2 sets of calcs, and then add both together. If the inverter can match that, you are doing OK

[DaveC]

The Fronius inverters have a single MPPT. The only grid tie inverters that I am aware of that have multiple MPPT systems are the Magnatek Aurora (which had 2) and the old Sharp Sunvista (which had 3 MPP Trackers I think). I would not recommend putting an array with multiple azimuths on a single mppt inverter. I would recommend using two inverters.