Date & Time: 13/09/2025, approximately 22:00 Location: [User’s installation site] System Overview The installation consists of the following components: SMA 5000TL inverter, connected to AC Out1. MPPT 450/100 DC/DC converter, directly charging the battery bank. Three Multiplus II units, …

First and foremost, a heartfelt thank you to everyone who provided support. The issue has been resolved — it turned out to be a faulty residual-current device, which has now been replaced and the problems are gone. Thanks again!:smiling_face: :smiling_face:

Ok so in change over is that neutral linked? Where is your CT for the grid in as I didn’t think they could play nice on 3 phase without it?

If you’re asking about the grid meter, this is handled by the three Multiplus units themselves. Here’s a representation of my installation. SMA invert comes on when sun start shinning. [image]

Yes wasn’t aware they could do it accurately enough as a 3 phase setup, have you tested the system since ie by using test function of the rcd instead of the switch to simulate the same issue that happened with the lightning? Have you done an RCD test with a meter to make sure they trigger as manufa…

I’d like to run these tests again over the weekend. It worked three months ago during a test and also during a grid outage. But now, with this nearby lightning strike, it didn’t. Which transfer switch are you using?

The transfer switch on the ac out side of the multi’s, @BjoernK did say something about taking one rcd out I’m not sure how your regs are but not having as many RCD’s would make it less susceptible to nuisance tripping. I imagine it’s due to the lighting and testing was all done from the switch rat…

Be careful as I see an EV charger down the line ultimately that needs a type B protecting against higher DC leakage not sure what else is protected by that RCD ie heat pump, not knowing the regs I’ll refrain from answering that question as it’s too dependent on a lot of parts ie what else that RCD p…

Typ B is only needed for DC residual currents. As the Multiplus has a transformer, a DC residual current is not possible. Don’t know the rest of your PV system, but either for the Multiplus nor for the grid you don’t need a B-Type RCD. To your problem: When the system worked before, also in a gri…

[image] Jetlag: Typ B is only needed for DC residual currents. As the Multiplus has a transformer, a DC residual current is not possible. Don’t know the rest of your PV system, but either for the Multiplus nor for the grid you don’t need a B-Type RCD. To your problem: When the system worked b…

Don’t know where you are located and if a SPD is not required by regulations, but anyway it would be usefull to be better protected. Regarding your problem, - Why did you say, or how did you recognize, that the MP2 are pushing still energy to the “system”. You did not answer the question from Björn…

Backup system did not activate during the grid outage

Q&A and troubleshooting

Erik2 (EC) 17 September 2025 07:30 23

My RCD on the grid side is a Type A, I noticed that yesterday, and the one on the load side is a Type B.
I was thinking of swapping them, so that the Type B is on the grid side.
What do you think about that?

Updated drawing

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Backup system did not activate during the grid outage

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