Adding separate DB to existing system, with separate metering


I currently have 2 x MultiPlus-II 48/5000/70-48 in parallel, driving a single phase to my house. The 3-phase board in the house is “bridged” so I drive the whole house off that single feed.

I have a granny flat that I would like to add to the system, driving just a few essentials - fridge, a few plugs for electronics including a TV and their fibre and wifi kit. The flat currently has it’s own municipal feed so the essentials will be completely removed from that municipal feed and put onto mine, hence me wanting to separately meter it so they pay for what they use, municipal and solar. I have plenty of daytime solar - average about 30kWh and a really big battery bank (long story, but it’s “big”)

My system current has a ET340 to meter power to the house but using just the one phase on the ET340. I installed this in the event I want to convert to 3-phase later.

I want to add a meter to the flat essentials I am putting on my MPIIs and batteries during load shedding. My reading says I can put in an ET112, after the isolator and breaker I will install on their feed, connected to my Cerbo GX on a spare USB port. As far as I can see I can connect two ETs, as long as I change the modbus address on the second ET to another number using the UCS Desktop configuration software.

Not worried about separating how much usage I register to the main house, I will put all the power through the ET340 first.

Has anyone done this, any catches or reasons to NOT do this, before I spend the tin on an ET112. Or anything I have left out, such as the ET340 being an essential single metering device for the whole system - if that question makes sense?

Obviously happy to clarify and to take advice.

Addresses 1 and 2 are supported. No more.

Configure the second meter with an “AC load” role. Two grid meters are a little… undefined. System might follow the wrong one. You can have as many AC loads as you want.