Seems to me, if you are using a GTI system, that puts out 220vac,
you will have to cut into both hot sides of the 220vac, between the GTI and the grid.
You would insert that meter into that cut. (In series like a Killavolt meter).
So, the meter would be powered by the grid 24/7..?.
One side is going to be just a pass-thru, and a common for the internal DC PS & an AC voltage measurement point.
The other side (red?) will be tapped for voltage measurement, and the internal DC PS.
That side will likely have a non-contact current sensor. (like a clamp sensor).
But it could have a plain old resistor sensor, like a Killavolt.
The only problem I see is your meter board would not have a ground or neutral. (floating).
And part of the board would be electrically 'hot', relative to ground.
If you put the meter in a metal box, you could ground it to neutral..
Not gonna be UL approved..
