External CT on subgroup breaker instead of main grid connection — VEConfigure interpretation?

Q&A and troubleshooting
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1

I have a MultiPlus-II GX 48/4500 in an ESS/DESS setup. The inverter, PV inverter (~2500W) and loads are all on a single 16A subgroup in the garage. There is no possibility to run a separate cable to the main distribution panel.
I want to use the external CT (100A:50mA) clamped around the 16A subgroup cable to implement PowerControl, so the MP respects the 16A breaker limit regardless of what the PV inverter is producing or consuming.
A VM-3P75CT is installed at the main grid connection for DESS.
My question: does VEConfigure treat the external CT purely as “measure the current at this point and use it for PowerControl/PowerAssist” — or does it assume the CT is always at the main grid connection? Are there any known issues or limitations when using the CT on a subgroup rather than the main grid feed?

2

@RikHa You have to select the grid meter as below. There can only be one source of truth. Why the 3P75CT if all the loads are on the sub as you wrote? Also, are the loads and PV on the ACOUT of the Multiplus ?

3

Not everything is on the subgroup. The MP and PV inverter (~2500W) are on the 16A subgroup in the garage. The rest of the house (lighting, sockets, etc.) is on other circuits, all fed from the same 35A main connection.

The VM-3P75CT on the main connection is needed for DESS to see total household consumption and optimize accordingly.

The external CT on the 16A subgroup would be purely for PowerControl — to prevent the 16A breaker from tripping regardless of what the PV inverter is producing or consuming at any given moment.

So the question remains: can the external CT and the VM-3P75CT coexist, each serving their own purpose?

4

I have both an energy meter and CT installed and use the CT as my primary grid meter as it offers the best system ramp up speeds. A CT can only ever be a grid meter as you cannot assign different roles to it as with external meters e.g. my EM530. The energy meter is not used by the system and only displays and records data for comparisons. You can set an inverter limit to 3.68kW or a G98 gridcode depending on your location, but be at risk of the PV inverter together with the multiplus output tripping the circuit breaker which is what you are trying to avoid.