FoxESS Community - Owners & Installers Forum

Hi, I am wanting to expand my solar capabilities.
Currently we have around 4kx of panels on east/west roof in a 50/50 split (2x5 panels)
I have an option to cover a South facing extension in more panels, possibly up to double the current capacity, probably more like 8 panels
Can you recommend which inverter is the most cost effective swap.
Current one is a H1-3.7-E.
The inputs are all in use so I would need 8kw with more inputs than the current.
Would I be best to install the new panels in series or parallel with each other?
I don't plan any further upgrades beyond this so just need the cheapest suitable option.

The inputs are all in use so I would need 8kw with more inputs than the current.

I have the 7kW KH7, which also has 3 MPPTs. Both the KH7 and KH8 (8kW) inverter would require a G99 application (which you'd probably need anyway).

An alternative with the H1 inverter range would be to put optimisers onto the panels on one of the strings, so that you can combine two roof aspects together into one MPPT.

From a cost viewpoint, I'm not sure which is the most cost effective, the H1 range is cheaper, but the optimisers do also cost money. TBH I prefer the KH7 or 8 approach.

Thanks, I am leaning toward the 8kw, need to price everything up before I look into the approval for it.

Hi,
You may want to find out if there are individual string limits for the 8kw,
as it has 3 MPPTs they suggest balancing the strings as much as possible.
And as i found from recent experience, there are upper limits per string on each MPPT.
You may want to get the latest data sheet and see how you can plan your layout.

16A (normal) or 20A (short-circuit),
and 80 to 500v MPPT range (600v open circuit).

So up to 8kWp on a single MPPT, and a max of 16kWp (STC) or 12kWp (actual) overall.


https://www.fox-ess.com/Public/Uploads/ ... 250912.pdf

Looking at the Aiko 495W panels as an example, 41.1v open circuit, 34.5v mppt, 15A short circuit, 14.35A mppt, at 25c.

So ballpark 14 panels on a single string, although probably 13 once you calculate the cold-day voltage. 8 panels should be no problem at all.

The specs may say they can take full load of single string, but that has not been my experience
3.6kw F3600 was clipping at 3kw, (checked with another inverter panels OK) and the only reason i suspected it was a string limit was few posts on Australian forums where the is a much larger user base.
Split the strings and it ran at 3.6/3.8kw OK.

F3600 is very different to the hybrid KH series. There's a 4kW limit per string on the F series, which is mentioned in the datasheet.

Yes i can see what the little * shows on the bottom of the data sheet, but the empirical data disagrees This is not 4kw!
the installer that fitted my system has said there is new guidance on string sizing that came out recently (last few weeks) and will now have to split the larger of my 2 systems into 2 stings to stop the clipping!
And the only reason i suspected string sizing was from a few posts on the H series from Australia that have had the same issues.
the Data sheets may not be 100% accurate?