Hybrid Inverter and String Inverter in the Same System

Duine_Eigin

I'd just like to get some advice for a planned upgrade to my PV system. My current setup is 3kWp installed on a south-facing roof connected to a 3kW Sunnyboy inverter. It was a DIY install as part of a new build in 2018. I would now like to add a battery and some additional panels. The south-facing roof has no space to install additional panels but I do have space on the south-facing shed roof in the back garden.

The plan would be to replace the Sunnyboy inverter with a 3.6kW Solis hybrid inverter connected to 5-10kWh of batteries. I would like to move the Sunnyboy inverter to the shed and connect it to the 1-2kWp of new panels installed there (or sell it and install a smaller inverter if it would make financial sense). I am not sure however how the Solis inverter will react to a second inverter in the system. Just wondering if it's possible to install two such inverters in the system and if anyone has experience of doing this before? Thanks.

bullit_dodger

Your replacing your 3Kw Sunnyboy with a 3.6kw Solis. Why not replace that with a 6Kw hybrid Solis (which the batteries would be off of) and run the two strings into the 1 inverter? Distances might be a problem of course as you didn't mention how far away your shed is, but it would seem to be a more simple solution (and also future proof you for somewhat for future upgrades?)

Duine_Eigin

Thanks for the quick response.

The Sunnyboy is wired with 2.5sq so a 3.6kW inverter is the max size I'd like to go to with the current wiring. I also already have cat6 at the inverter so that will handle the CT clamp wiring. It would be a simple straight swap of the inverter with a possible MCB upgrade. Same with the shed, I already have 2.5sq SWA run out to it so if I locate the string inverter there, it will need no further wiring to my consumer unit. As the house is relatively still new (and airtight), I'm reluctant to run new wiring and put holes in walls when the wires are already there.

Also, I've been keeping an eye on my daytime electricity usage and it rarely spikes above 3.6kW at any one point in time. The 3.6kW Solis will be able to manage 99% of my daytime energy use.

Jonathan

I think @irishchris has a similar set up. Solis hybrid + string inverter.

irishchris

https://www.boards.ie/discussion/comment/118785578#Comment_118785578

Spot on, I have a 2.5kw goodwe string inverter and a 6kw Solis hybrid. No issues whatsoever. If anything they complement each other as if the non hybrid is producing excess the hybrid inverter picks it up and diverts it to charge its batteries along with its own power.

Duine_Eigin

That's good to hear, thanks irishchris. I didn't think the Solis would charge from excess AC. I figured it would only charge from its own DC input from the panels or from AC during a set time period. I take it that the Solis is picking up the excess by reading the grid export and you've no additional wiring or CT clamps to make this happen (ie both inverters aren't communicating with each other and are just feeding power to the house/grid)?

Do you have any diverter devices like a Zappi or an Eddi? I have both so I assume I will just need to loop the generation CT clamp around the live for each of the inverters. I'm pretty sure a second CT clamp would work too but I'd like to get away without having to buy another one.

irishchris

https://www.boards.ie/discussion/comment/118786862#Comment_118786862

Yep the Solis is realising the excess from its own grid clamp and there is no communication whatsoever between the inverters