Possibly off-topic, but have you come across any good resources for understanding how to design such a system? We need a 22kWp PV rig to be self-sufficient (we use 22kWh/day, and in December we'll get the equivalent of one full hour of sunshine). I was speaking to folks at Joju at Fully Charged Live/Grand Designs Live (I can't remember which, they were one day after the other) and they said that there's a maximum load that you can put on each phase, so it could start getting tricky. Additionally one building might be a holiday let, which might further confuse things.
I like to try and understand things from first principles (which is why I've had the dubious pleasure of reading the entire National Planning Policy Framework, Local Plan, Draft Local Plan, AONB Management Plan, Kent Design Guide...) so if there's any accessible starting point you know of to learn about this stuff, I'd be really grateful if you could point me in the right direction.
No actually, sorry.
... in my experience, I've had to learn a lot, and in some instances guide the electricians in the retro-fit design of our house... it took some creative thinking and a bit of planning.
Our house originally was on a looped supply single phase (L1) which had to be removed. But I didn't want that setup (L1) to change as we already had two Powerwalls on (L1) backing it all up through a Tesla Gateway 2, also wired single phase on (L1), and a Solar Array. The house still has it's own single phase consumer unit.
I then had a 7 kW Zappi charger installed directly onto the Gateway 2 unit on the Grid Tied side. This allows us to charge the cars directly from the Tesla Powerwalls at 7kW (removing the excess Solar minimum limit of 1.4kW). This generally means nothing is exported to the grid and we use all the Solar regardless of how much trickles into the Powerwalls.
Then I installed a 32amp Commando Socket on the Tesla Gateway 2 backup side. This means during a Grid blackout we have access to emergency car charging at 7kW.
When 3 Phase was installed we had the 3 phase distribution board installed outside, on the kitchen wall. So when we extend the kitchen we can get access to 3 phase power for fancy kitchen appliances.
This also meant the two 22kW chargers could be wired into this distribution unit, taking advantage of a staggered primary phase.
Ie... First Zappi 22kW wired on primary phase L2 (looks like L2,L3,L1)
Second Zappi 22kW wired on primary phase L3 (looks like L3, L2, L1)
This means during heavy load balancing, each charger could automatically default to it's own 7kW phase. One charger on L1, one charger on L2, one charger on L3.
With the house and backup set on (L1), we're introducing new loads setup on L2 and L3 ... like Heat Pumps (I use plural as we have an Air to Air Heat Pump, and I may install a Air to Water version as well). But anything on L2 or L3 is not backed up on Powerwalls.
So all in all, it works great. Some real heavy lifting, all our house is on backup, and most of it is done at cheap rate on Smart Meter and Ev Tariff.
