NEW SYSTEM RCBO; fighting with each other

Q&A and troubleshooting
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1

i have a Multiplus2 with some initial connection issues

I have a 50A RCBO feeding the AC IN this is connected to the GRID and sits in the Consumer unit BUT is NOT connected to the consumer unit it is connected directly to THE GRID and nothing else.

IN the Consumer Unit there is a 20A RCBO that feeds my solar inverter

MY solar system is a Solar Edge FIT system and I have an ET112 energy meter measuring the solar output this is connected before the solar FIT Meter {I think}

This ET112 was initially showing a minus figure but once I reversed the feed wires it now registers properly and these figures match what my solar inverter is outputting using the Solar Edge app

BUT these two RCBO’s seem to be fighting with each other and I am told that this is because of a wiring misconfiguration issue

The solar system feeds THE GRID after going though a solar FIT meter that measures solar energy generated so i can get paid for my solar generation.

Now am being told that my solar inverter output should be connected to AC Out 1 to avoid this conflict

Now AC Out 1 feeds the consumer unit so where do I connect the output of the Solar FIT meter

I also have a change over switch that connects the GRID OR the MULTIPLUS 2 to the consumer unit so IF I have problems with the Victron/Pylontech Battery Storage System I can run the house on the GRID and isolate the BSS for any upgrades maintenance ETC

many thanks

David

2

I tried to block this out for you so we can have a look.

Solar should go to the RCBO the FIT meter then the grid.
You have an RCBO on AC in and AC out goes to the consumer unit and in there is a change over switch?

The ET112 needs to be connected to the grid and it needs to be negative so the multiplus sees there is excess power going to the grid. When the power is negative the multiplus will use the internal charger to charge the battery.

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If you have a look at my 24V ESS the grid is negative the system cant even see the solar it just sees there is excess energy going out I have 2 x 5000W inverters grid tied on 2 phases. There is about 8A of solar going in from an MPPT the rest is 25A from the internal charger.
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3

First thanks for your input and reply

The solar output is going to the FIT meter the RCBO for my solar is ONLY there powering the Solar Edge solar inverter

You have an RCBO on AC in and AC out goes to the consumer unit and in there is a change over switch?

YES CORRECT see my detailed new reply/post

Can I not configure the system to see the ET112 measuring solar energy and that triggering charging the batteries

NOW LOOKIE HERE
what i discovered when I googled my problem

PLUS a Write-Up of my system

BSS

The issue of a Victron MultiPlus-II and an AC solar inverter “fighting” each other, even on separate RCBOs, is a common problem in AC-coupled systems and

typically stems from incorrect wiring or configuration issues, especially concerning system synchronization and earthing, rather than the separate breakers themselves.

The MultiPlus-II is designed to manage AC power, and if the AC solar inverter is not correctly integrated into the system’s control loop, conflicts arise.

Likely Causes and Solutions

The primary reason for this conflict is often a misconfiguration in how the MultiPlus-II manages the AC input/output and coordinates with the external AC solar inverter.

  • Incorrect AC-Coupling Setup: The MultiPlus-II needs to be aware of the AC solar inverter’s presence and generation capabilities to manage power flow correctly. If they are on completely separate circuits with no communication or shared reference, they operate independently, leading to conflicts.

    • Solution: Ensure the AC solar inverter is connected to the AC output (AC Out 1) of the MultiPlus-II, not the AC input or a completely separate circuit. When the grid fails, the MultiPlus-II creates a local micro-grid and needs the solar inverter’s output to be on its output side to manage its frequency and voltage. The MultiPlus cannot manage an inverter on its AC input when off-grid.

  • Missing or Misconfigured Energy Meter/ESS Assistant: The Victron Energy Storage System (ESS) assistant and a grid meter (like an ET112 energy meter) are essential for the MultiPlus to measure the power flow at the grid connection point and control the AC solar inverter via frequency shifting.

    • Solution: Install and configure a Victron grid meter at the main AC input (before any loads or PV inverter connection) and configure it as the ‘Grid meter’ in the GX device (e.g., Cerbo GX). This allows the system to balance power and prevent backfeed issues.

  • Grounding/Earthing Issues: When the MultiPlus switches between grid-connected and inverting modes, the neutral-to-ground bond inside the unit is switched by a relay. If both inverters are on separate circuits with different grounding points or RCDs, this can cause nuisance tripping or “fighting” due to ground loops or unexpected leakage currents.

    • Solution: Adhere to Victron’s recommended wiring diagrams for AC coupling. Use double-pole RCBOs/breakers for complete isolation of both Live and Neutral lines where necessary to ensure proper neutral management.

  • Firmware Mismatch: Outdated firmware can lead to communication errors and unexpected behavior between devices.

    • Solution: Update the firmware on all connected Victron devices (MultiPlus-II, GX device, MPPTs if applicable) to the latest versions using the Victron Configurator or VRM portal.

  • Configuration Settings (Weak AC, UPS mode):

    • Solution: In the MultiPlus-II’s settings (via VEConfigure), try enabling “Accept wide AC frequency” and “Weak AC” options. This can help the MultiPlus better synchronize with the potentially unstable waveform from the AC inverter or generator sources. Also, ensure the UPS function is not interfering if unnecessary for your application.

MY SYSTEM CONFIGURATION

GRID CONNECTIONS

G. 1 This connection is to the change over switch (mains on side)

G. 2 This connection is to a 50A RCBO (to power the inverter AC IN connection)

G. 3 This connection is from the output of my Solar Edge solar system (VIA the FIT Meter)

MULTIPLUS II CONNECTIONS

AC IN This is connected to G2 (the 50A RCBO connected to the grid) via a 100A AC Isolator located beside the Multiplus 11 inverter

AC1 OUT This is connected to G1 (the change over switch {mains off side}) via a 100A AC Isolator located beside the Multiplus 11 inverter

AC2 OUT NO CONNECTION

DC Positive This is connected to the Lynx 1000 distributor via a DC isolator

DC Negative This is connected to the Lynx 1000 distributor

VE-BUS This is connected to the CERBO GX

CERBO GX CONNECTIONS

48V power in from the Lynx 1000 distributor

VE-BUS from the Multiplus II

VE-CAN from Master Pylontech US5000 battery

RS485 USB connection from ET112

HDMI connection for GX Touch 70 screen

USB power feed to GX Touch 70 screen

CONSUMER UNIT CONNECTIONS

Change over switch (common feeding consumer unit)

20A RCBO power feed to the Solar Edge solar inverter

ET112 CONNECTIONS

RS485 cable

Power lines to the solar FIT meter

SOLAR EDGE CONNECTIONS

AC power in from 20A RCBO in Consumer Unit

AC power out to AC isolator

AC power to ET 112

AC power from ET112 to FIT Meter

FIT Meter to grid (G3 connection)

I think that is everything and I do hope that i got everything correct!! So my basic question stands how do I connect my Solar Edge AC output so that these RCBO’s are not in any conflict

My ET112 is working great NOW and is measuring the Solar energy BUT DO I NEED to MOVE THE ET112 to measure the GRID or do I need another ET112 to measure the grid for this system to work and let me see my solar energy and for the RCBO conflict to go away

4

FIXED THAT PROBLEM

We could find nothing wrong with the wiring and i was contemplating just leaving the solar disconnected BUT as a short term fix we replaced the RCBOs with ELCBs

Trying to figure out where the problem lay we first we replaced the solar 20A RCBO but then the inverter 50A RCBO tripped so we replaced that one as well

MY BAD I thought the solar breaker was powering the Solar Edge solar inverter when in fact it was/is the AC output from the Solar Edge solar inverter

AND that solar 20A breaker is connected to the consumer unit as is AC OUT 1 {via the change over switch} so that Solar Edge solar inverter is installed and wired correctly meeting Victron AC connection requirements

BUT we now have a NEW problem however I am exhausted after a day of playing with my BSS and I will post about this new further problem soon.

5

You need a sensor ( et112 / CT or compatible sensor ) that detects whole system inport / export to grid.

Example- i think is correct - if sensor is only detecting ac coupled FIT solar, as soon as this starts producing power the multiplus will use this amount of power to charge batteries as its being told there is excess power to use, but if ac has loads - this wont be taken into account and will be from grid.
Or if ac coupled solar isn’t producing anything, the multiplus will simply sit idle.

When sensor is detecting whole system - fitted on grid before any loads / solar, the multiplus will balance the whole system to whatever the grid set point is set to.

Extra sensors can be installed wherever you want them, but multi plus needs to know what the whole system is using or exporting.

A drawing of your system would help determine if my assumptions above are correct.

6

Thanks for your input however I will be putting on a Victron Current Transformer 5m Wire 100A 50mA (the clamp on one} on the MAIN AC OUT line to the GRID probably before the double pole Circuit Breaker downstream of the smart meter OR upstream of the smart meter before the 100A main grid fuse

What free software can I download and use for displaying a wiring diagram

Also I would like to be able to show VE components in this system diagram. I can download VE component pictures without too much difficulty

BUT I now have other more serious problems.

Just about to open a new thread about them.

7

Where is the earth neutural bond for the system? If you have one on AC in to the multiplus and then created another in the consumer unit on AC out that would cause problems. The multiplus has a relay that connects ground to neutural when there is no AC in so you dont need to connect neutural to earth in the AC out consumer unit for the RCD to work. You might have 2 neutural to earth bonds.

8

many thanks I sent this to my electrician and he thinks that we might have this issue

9

SORTED

It was a neutral problem which is why the RCBO’s were tripping

The electrician was a little out of his depth here {he is a great guy BUT this was his first BSS and Victron Energy Bits and Bobs system}

The problem was the miss wiring of the Grid. The Grid Neutral was connected to the Consumer Unit Neutral Busbar

ALL SORTED and working well charging the batteries and inverting to run the house and acting as a UPS when I disconnect the Grid

BUT VRM is showing the power to the grid fluctuating all over the place from -60W to 30W

I do NOT have a CT on the Grid connections and my VE Multiplus II suppliers ‘technical guy’ says this is ‘normal’ not something to be concerned about AND that fitting a CT to the Grid will not stop this.

Things are good but i think I will need to add two more Pylontech US5000 batteries. For sure one and I have room in my 19” rack cabinet for one more US5000 battery so that will be the first upgrade

Changing to Octopus GO at midnight tonight and have programmed the inverter to charge the batteries from 00:30 for 5 hours and being a late bedder certainly tonight I will connect my Nissan Leaf to the power outlet in the drive.

The Nissan Leaf has a big problem synchronising the two onboard clocks one is the cars ECU clock and the other is the GPS derived clock, unless you can synchronise them you cannot set up a scheduled charging profile

I will wait a few weeks before considering a Smart EV charger for my Nissan Leaf {RATHER EXPENSIVE with I would expect a long ROI {OMG the BSS has a much longer ROI} but then I can change to Octopus Intelligent GO} and to see how much battery capacity I truly need. Past figures {I have an octopus mini and the app} both great for looking at my energy usage show a max daily usage of 25 kWh

SO SORTED thanks for all you input, for sure that got me thinking and then helping my electrician understand how he had miss wired the A/C power lines. Replacing the RCBO’’s with ELCB’s indicated that it was not a problem on the ground side so that helped me focus on where the problem lay and then talking to my electrician he quickly understood where the problem was and today in 10 minutes it was fixed and another 30 or so minutes testing out all the functionality with the various Multiplus II A/C and DC configurations