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ESS Grid Metering internal vs external meter - understanding questions

In my ESS the 3phase Multis are connected to the Grid on AC-in - No Load on AC-in
All Load is connected on AC-out 1.
Fronius Inverter also on AC-out 1.
MPPT RS-450 on 48V side.
EM-24 Energy Meter and VM3P75 (for Test purposes) are installed on AC-in.

When I select internal Grid Metering - only AC Loads are shown on CX.
When I select external Grid Metering - CX shows my Load on critical Load and addtionaly AC-Loads are shown (almost 0 or close to zero).

Question A: is this the normal behavior or is it possible to have only AC-Load on the display when i select external metering (if there is no load connected to AC-in).

Question B: what are the pros and cons internal vs. external metering if i have no Load on AC-in.
Is the internal regulation by the Multi the fastest and most precise or is there any advantage using the external meter - my understanding - the regulation than has to go via the CX device.

Question C: if using external Meter - is the faster update interval of the new VM3P75 bringing any improvements.


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Jason - UK answered ·

@manfred@pumberger.at

Question A = Yes, this is normal. When you have any grid meter connected and set up correctly within the settings, it will show any loads you have before the MP as grid loads, and any loads you have on the AC-OUT will be shown as critical loads.

If you don't want to see grid loads, remove the grid meter from the list of connected devices.

Question B = Using a external grid meter allows you to many different things. If you have PV on the grid side, you can correctly see that shown on VRM and its contributions. Obviously if you have loads before the MP, you can see them separate to your critical loads. You can also choose to power the grid loads from the MP inverter as well as critical loads, or just critical loads only within the settings. Please note there is no internal 'meter', only a CT sensor.

Question C = yes and no. Any connected grid meter has latency but the one you mention has very low latency compare to others.

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manfred-1 avatar image manfred-1 commented ·
Jason, thank you very much for your answer.

I understand, that there are many things possible witht an external meter.
As in my installation there is no load connected on ACin and there is already a Fronius Metering installed on Grid side - my question is, if than it has any advantage to insall a Victron external meter?
If we compare internal vs external with EM-24 vs external wth the new VM3P75 only under the aspect of ESS regulation - is than the internal regulation by the Multi the best and fastest option, because not going via the CX?

Regards

Manfred



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