I’ve got a MultiplusII 5kVA configured in AC coupling with a Fronius inverter connected to some solar panels.
Since I’ve been having some issues with the power readings from the house loads, I was looking at the installation wiring. There’s something that caught my attention and I can’t really make sense of it: I can’t understand why the rccb and mcb are wired this way, if the current never flows to the Fronius but instead flows FROM the Fronius to the Victron or the house loads. As far as I know, these MCBs are directional, so the way they’re wired matters, and they protect what’s downstream. What am I missing?
For reference is this one: https://www.se.com/id/en/product/A9K27225/miniature-circuit-breaker-ik60n-2p-25a-c-curve/
There are more MCBs between the house loads and the closest rccb, I just omitted those for simplicity.
An mcb is to protect the wiring and equipment connected, most are not directional, some are. I cant find anything about directionality from the one in your link about it…
An rccb is to protect humans
If your drawing is corect i would be more concerned about your ac out being connected to grid?!
Thanks for the feedback! I’m starting to think it might be bidirectional, otherwise the wiring doesn’t make much sense.
As for the grid connected to the AC out: keep in mind that is just a switch the installer set up to bypass the entire solar setup. Under normal operation that line is not connected. However, if you select to bypass the solar installation in the changeover switch and keep the Fronius mcb disconnected, are there any potential issues? The current should flow to the house loads and not towards the MP2. Maybe an extra mcb between the MP2 and rccb to isolate the MP2?
Thank you! And it would just be left in the central position, when the grid changeover switch was in the bypass position?
I’m just curious to know why a 3 pos switch would be needed instead of the 2 pos one, if placed in the green circled area. The AC out would be either connected or not.
I’ve got another question about the MP2 in the AC coupling setup.
This MP2 has a 50A transfer switch in the AC in, additionally it can invert around 4kW (either battery or solar if PV was directly hooked to it). Is it fair to say then that the MP2 can delivery up to 15.5kW on the AC out? That is, if I were pulling all 50A from the grid (11.5kW) plus inverting at max. capacity ~4kW.
My concern is that the installer used 6mm2 wire from the iPF K40 to the house rccb without additional protection (the others are even thinner, 4mm2 in the MP AC-in & out). The house loads could be easily pulling 9kW: 3kW from the Fronius, 3kW from the grid and 3kW from the battery. This means 26A could be flowing through the AC-out on a 4mm2 wire (with no protection) and what’s worse, 39A on a 6mm2 rated for 25A with no protection.
This is what we need to pass inspection, second column is “max current” and last column is the required MCB. I’m going off of this, that’s why I expressed some concern.
Ok, got it. Wirings aside, is my understanding of what the AC out can potentially deliver correct? That is, whatever pulls from the AC in (grid) plus whatever is inverting (solar or battery)?
