Problems with MultiPlus-II system

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1

hello,

I have a connection problem with my MultiPlus-II GX.

As we live in a four-flat building, I only have the consumer unit

with RCDs, etc. in the utility room. Due to a lack of space, the

system is installed in the garage. The three-core cable from the Multi to the consumer unit

was installed and connected by the electrician.

The system consists of: 12 × 480 W PV panels on various roofs, Cerbo GX, MultiPlus-II GX, 2× MPPT 150/70, 1× MPPT 250/100, SmartShunt, and a VM-3P75CT energy meter. The system is configured as ESS.

I connected the VM-3P75CT current transformers under the main RCD to L1, L2 and L3, in the correct orientation, and the others to the 16 A circuit breakers.

The electrician connected the Multi’s feed-in cable via a separate RCD to the L3 that feeds into the main RCD.

Now I have the following problem!!

When I switch the system on, a cascading effect seems to build up.

The Multi keeps feeding in more and more current, even though the VM shows much lower consumption.

It ramps up to full power and feeds everything into the grid until the battery is empty.

If I remove a current transformer from L1, L2 or L3 and clamp it around the Multi’s incoming cable, everything works as intended on two phases, but the corresponding phase is then not included in the measurement.

Where is the fault??

2

A single MP II must always be connected to PHASE 1!!

3

Is the RCD for protection, or is it on the mains side?

4

What kind of MP II do you have?

And how is it connected … presumably via AC-in, right?

If the grid connection is then between the main connection and the connection to the house/flat .. you don’t need an additional RCD, but “only” a fuse.

5

Hi Holger,

First of all, many thanks for your reply.

I have connected a 24V/3000 MP II via AC-in.

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6

Hello again, the 16 A fuses shown in the drawing are meant to represent the house’s sub-distribution board.

7

The tap for the MultiPlus must be downstream of the VM-3P75CT’s measuring transformers so that it also measures the MultiPlus’s power.
This should also be shown in the instructions.

8

And connect MP II to PHASE 1

9

There is no Phase 1 — the MP2 simply has to be on the same phase as the one the electricity meter also identifies as Phase 1.

If necessary, swap the wiring at the electricity meter.

Perhaps Victron will make this configurable in the future? It would simplify many installations.

10

It’s already available on the RS6000. However, I can’t imagine such a feature being added later for the MP2.

11

It’s not that complicated—and the problem only occurs with the meters suggested by Victron.

With Shelly, or even simply reading the household meter via SML, it doesn’t matter; you can assign the phase to be regulated.

12

Yes, on the one hand it would be nice if you could configure that, but on the other hand, what’s the problem with simply building it correctly?
So why not just connect the MultiPlus to L1, as required by Victron?

13

You can see the problems with the OP: MP2 goes into the garage, the electrician connects the sub-meter, and the garage connection doesn’t correspond to L1 on the sub-meter.

Explaining something like that to an electrician is often very tedious.