FoxESS Community - Owners & Installers Forum

Hello. I have a Fox ESS 3.6kW unit already, with 6 panels on the main house.

I'd like to add another identical system to an outbuilding, i.e. a second Fox ESS 3.6kW inverter fed by another 6 new panels. This outbuilding already has a chunky underground cable to feed its power supply. I'm hoping that the new solar system can be connected into the consumer unit in the outbuilding, from where it would shove its power back up the existing cable into the main home consumer unit via the existing cable and connection.

I'm hoping that this would work, as it's essentially the same as two neighbouring houses each having its own system?

Or is there a whole world of complication that I don't know about? I do appreciate that it would need DNO approval, hopefully this won't be an issue but I need to know if it's possible before I apply.

I don't have any batteries, and have no plans to add any. I've read about RS485 comms between inverters, but all the discussions here and elsewhere seem to include batteries. is this still required if batteries aren't used?

Many thanks in advance.

I don't know the technical ins and outs too well, but you will need a G99 prior to the work being done as you seem well aware.

Next is the inverters need to be put into parallel mode I think it's called, as they need to work in tandem. Biggest hurdle will be communications between the two, so you will need to run a data cable between both inverters. I don't know if you just need a single CT clamp, or an additional one for the new Inverter. Hopefully someone with more technical knowledge can answer to clear this up.

Assuming the cable to the outbuilding is rated for the extra power and it is connected to the same single supply meter it will work, obviously it will affect your DNO approvals as 2 inverters will need G99 approval (i.e. > 3.68kW, 16A export)

Solar only inverters do not (typically) have CT clamps to measure the power flow, they just output at full power - however depending on what your DNO allows they may need some throttling to meet your export limit which does require one fitting (a single pair low voltage cable).

There is no requirement for RS485 unless your DNO gives you an export limit and the distance is too far to run a CT cable (typically 25 metres is the maximum) in which case you have to run an RS485 pair and install a meter instead - but as you already have an 3.6kW inverter in the main building it is likely if you do have to restrict your export that will be the only inverter that would need to limit it’s export and so no extra cabling needed to the outbuilding.

If they were hybrid inverters (i.e. with battery) you would have to run communications between them so they can load balance between themselves.

Thanks Dave, much better than my post