No you only need 2 for a SINGLE phase system. The circuit is for mine which is 3 phase. The problem is that if you put the clamp upstream of the distribution board, the wiring carries both current that you are consuming AND solar generated current that you are putting back to the grid.
The single CT is not smart enough to differentiate between the two so you need some way to differentiate them.
The blue arrow in the diagram is the supply wiring that would be existing to your DB. This is the one carrying both Consumption ADN solar current WHICH IT YOUR PROBLEM - as illustrated by the dotted red arrow which represents the Solamar current fed back to the grid. Mathematically you could think of this as (TOTAL CURRENT = CONSUMPTION CURRENT - SOLAR CURRENT) SOLAR CURRENT is negative as it flows in the opposite direction
The solid red line is the wire from the solar inverter to your DB. Now, you KNOW this only carries the solar current.
Now for the truck. If you measure the combined cuttent in the 2 wires, the solar cancels out!..
CONSUMPTION CURRENT = TOTAL CURRENT + SOLAR CURRENT …
But TOTAL CURRENT = CONSUMPTION CURRENT - SOLAR CURRENT.
Wiring wise, if you pass the solar wire through the consumption clamp the solar component in the consumption wire is cancelled out and you see only consumption. HOWEVER, YOU NEED TO BE CAREFUL WITH THE DIRECTION OF THE SOLAR WIRE OR YOU WILL DOUBLE THE SOLAR READING.
Just to confuse you further separate issue, with CT’s you need to be careful with electrical noise from the inverter (especially Fronius) which can stuff up the readings. You will quickly see this if the inverter says its generating power at night.
In any case you do need to check the power displayed against the electricity company meter. The difference can easily be 10% which makes nonsense of installing ct’s