question

Matthias Pallhuber avatar image
Matthias Pallhuber asked

VM-3P75CT as Grid Meter Showing reversed signs

I am having a setup which is using a MP 2 to connect a battery to the house. Only AC1 is connected to the grid. I have a VM-3P75CT connected through CAN BUS which is sitting right after the grid meter. Instructions would have said that VM-3P75CT is picked up automatically by CERBO but i had to adjust the CAN port protocol. I found through trial and error that one working on 250k rate is bringing the energy meter to the device list.


What i now experience, even though we have triple checked the the correct direction of energy clamps, is that the meter is showing a minus value in VRM when taking from grid. I somehow believe this is wrong because then the battery control does not work.

Does someone have an idea what setting i could do different?

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Energy Meter
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3 Answers
ldoes (Victron Energy) avatar image
ldoes (Victron Energy) answered ·

Hi @Matthias Pallhuber, thank you for the remark about VE.CAN instruction in the manual. I'll pass this on so we can improve it.

Just to make sure: Is the direction of the array on the CTs pointing from the grid connection towards the inverter/charger? Also, are you running the latest firmware version of the VM-3P75CT? If not, please update it to the latest version (v1.06 at time of writing).

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Matthias Pallhuber avatar image
Matthias Pallhuber answered ·

thank you for your prompt reply. No we have not update the energy meter yet. I would not have assumed that this changes the direction of the flow but we can do this.

For wiring we followed below instructions: AC source is in our case the GRID. AC loads is consumers but also the AC IN from MP2. So, yes I believe this is correctly wired.

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ldoes (Victron Energy) avatar image ldoes (Victron Energy) ♦♦ commented ·

Hi @Matthias Pallhuber, one possibility is that the CTs are clamped on the wrong phase wires. If this is difficult to identify by eye, you can troubleshoot by hooking up all the CTs over the same wire and checking the measured power. The measured power with the largest magnitude (likely) corresponds to that phase.

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empunkt avatar image
empunkt answered ·

I had a similar issue (I guess) after replacing my broken EM24. The VM-3P75CT is installed between grid and AC IN. I also interpreted the instruction like grid is source in this scenario, but this appeared to be wrong. After hours of checking all connections, firmware versions, direction of the clamps, etc. I switched the direction of the clamps and voila, system was back to normal immediately.
So I think this scenario is missing in the instruction, instruction is wrong or at least subject of interpretation, like on AC IN "source" is the converter.

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