My inverter was installed for me to get everything tested before connecting the battery (the electrician changed my consumer unit at the same time). The inverter was happily running and I had done most of the configuration.
The electrician came back to disconnect the TNS Earth (as I had a TT Earth installed for island mode, and by chance grid TNS earth was poor) and change my main switch (in meter box to time delay RCD) - this work was all in the meter cabinet and 10m from any house wiring.
At some point in this process of disconnecting power (2 hours), my inverter is now tripping my 40A MCB that feeds the AC In. The battery is still not connected, and no load is currently connected to AC Out (however it was working ok with a load on AC Out previously). In Charger only mode, or normal mode, when the inverter turns on it causes a large spark in the 40A MCB and as a result it trips.
I have read on this forum that I need a battery connected, but I cannot understand why everything was working fine before? Nothing that changed would have an impact on the inverter…
I have also seen some people on the victron forums complain of this issue, but Im not clear what the solution is as there was no solution posted? (E.g. here - Multiplus 2 trips breaker - VictronEnergy with @mattfr)
Oh yes it has, you now have a new breaker, which may well be much more sensitive than the old breaker.
The Multiplus has a large bank of capacitors on the DC input. Without a battery installed, the first thing that happens when the Multiplus closes the input relay is a large inrush current charging these capacitors. Perhaps the old breaker allowed this inrush current through and the new one does not. Power it up with the battery first, ideally with a precharge circuit.
Its a 100mA Slow RCD on Grid input, and this has never triggered, the only thing that keeps tripping is the 40A MCB that feeds the AC In on the inverter (all RCBOs are downstream of inverter - but again even if I move the ‘essential loads’ to be grid provided the Multiplus still trips the MCB)
For the sake of providing some clarity to future users, when the battery is connected then everything works as predicted, with no blowing of my MCB.
I really think this should be mentioned more clearly in the manual as it really isnt mentioned, and to be honest it sounds like a fairly crucial requirement. Either way I’d love to know why the inverter behaviour changed, despite there being no attributable change in configuration/setup, but I guess it is unlikely I’ll get this.