Multiple solar install question

[rossm]

I have a 5KW hybrid solar installation on my house. The inverter output feeds into a Henley block upstream of the main consumer unit and there's a 60A feed from the Henley block to a second consumer unit in an extension to the house. Lastly, there's a 40A feed from the second consumer unit to a third small consumer unit in a detached garage.

I'm thinking of adding a second 3KW hybrid installation in the garage. My assumption is that the second inverter could connect to the 40A feed from the house and the CT clamp go on the 40A live wire. The base load of the garage is around 200w so this would mean that the inverter would operate in "export" mode for most of the time once the battery is charged. The power "exported" back to the house would presumably be seen by the main inverter as reduced demand which would, in turn, operate in "export" mode once it's battery is charged. Come the end of the day both inverters would supply from their batteries to the lower SoC limit and then I'd be back fully on-grid.

The alternative would be to put a meter on the main supply and long-line an RS485 connection to the second inverter in the garage but - apart from being a headache to install (I'd probably use a RS485/Ethernet adaptor instead, but that's still more messing about) - I don't see that that would meaningfully change the operation.

Have I got something massively wrong here?

 

[binky]

Without the data connection to the main house meter tails your garage battery will only supply demand from within the garage. It may possibly be better to expand the house battery and just have a standard solar inverter in the garage. The garage array will still help charge up your house battery by reducing import demand to the whole property, so more surplus energy from the house array will be used to charge the house battery.

 

[rossm]

I think you're right - I'm always overthinking things. It will be a lot easier - and cheaper - to add another slave battery to the installed system and just put panels and micro-inverters on the garage.

Thanks for the insight.