Hello,
does anyone please have experience with measuring using the Victron VM-3P75CT? It overreports compared to reality (invoices).
For example:
Purchase (Victron): 38 kWh / Purchase (Invoice): 22 kWh
Sale (Victron): 430 kWh / Sale (Invoice): 293 kWh
I have ESS, 3x Multiplus II 5000 in 3phase, Cerbo GX MKII, VM-3P75CT, all on actual firmware.
Thank you.
Small differences are always there, but yours are huge. This indicates, that your meter is running with a different vectoring method than your energy providers meter.
If you have one in a “per-phase” mode, and the other in a “saldating” mode, the numbers will not fit together.
Since you cannot change the behaviour of your grid providers counting, you should get to know, which is the correct vectoring method to be configured on the VM-3P75CT to match your main meter.
Since your VM-3P75CT values are > than the providers values in both directions, I would assume your VM-3P75CT is running with individual phase-counting (probably delivery-default applicable for most countries), but should be saldating. (i.e. in Saldating mode, having a “-200 / 200” on two phases would be 0, in individual mode, it will count 200 import and 200 export at the same time.)
Hi, in the Czech Republic the energy supplier charges each phase separately. So I have set individual phase measurement in ESS. In VM-3P75CT I have set 3 phases and arithmetic. I checked the CT coils and they are closed and tightened correctly, I have connected them correctly CT1 to input 1 etc. The system works well, but the power displayed by Victron does not suit me.
That then sounds about right.
As said, small differences are normal, but on your side they are to big to just be some sort of measurement inaccuracy.
So, beside the placement of the CTs, you should review the voltage sense wires for correct association.
What is your setpoint?
The small amount purchased: Can you trace that down to a few concrete “events /days”, where you needed energy from grid - or is is it more a ~1kWh recorded as purchase every day?
Hi, I replaced the VM-3P75CT with an EM540 and the situation is the same, Victron still “overmeasures” by 30-40 percent. This made me think that the electricity meter from the distribution network to the house is faulty. Then I actually found out that the electricity meter from the distributor does not measure phase 1. This would explain the lower invoices for purchasing and selling energy. It also means that Victron measures correctly. I contacted the distributor to replace the electricity meter. Once it is done, I will share the result with you. I am also glad that I used the new EM540, I think it was not a waste of a purchase for me, I think it has much better measurement and Victron can regulate better than with the VM-3P75CT.
Hi, I had my energy supplier replace the electricity meter, and it actually turned out that the original one was not measuring one phase. Therefore, the problem was not with the VM-3P75CT, which I also replaced with the EM540. Now the EM540 and the new energy supplier’s meter show only a small single-digit kWh deviation, e.g., EM540 184 kWh and the supplier’s meter 182 kWh. This issue is therefore resolved. Thank you.
Good to know where the problem was but not good for your pocket as they will now be charging you for the three phases not just the two.
Yes, but it will be beneficial when selling energy because I am selling on 3 phases. Now they will finally pay me for all 3 phases. 
