Today I got the very first accidental short-circuit in one of the circuits in my house since installing my Victron system (3*MPII 5k, 3*Pylontech US5000). No big deal, cut the 220V cable while trimming the hedge.
However, I was a bit disappointed to notice that in addition to the MCB of the involved circuit (B16, 1 phase), two other devices tripped:
The RCCB in my utility closet feeding the Victron MPIIs (B20, 3 phase, RCCB1 in the picture below)
The MCB near my Victron system feeding my home installation (B20, 3 phase, MCB1 in the picture below)
The result was that I had no electricity in my house at all, it should have been just the circuit to which my hedge trimmer was connected. Note that the cut cable had only two wires (just phase and neutral, no earth), so there was no earth fault.
Does anyone have suggestions to improve this situation ? My connection to the grid is 3*25A (with C-char fuses owned by the grid operator), every circuit in my house has a B16 MCB. Should I change RCCB1 and MCB1 to C20 or maybe B25 versions ? Not sure how to improve/introduce selectivity in my situation. All help would be much appreciated.
@PhilipZetten this is a job for an electrician too many factors at play for safety local regs, could there be something under lining issues with stuff before the multi like shared neutrals. My advice get an electrician to give it the once over they can then talk to you about selectivity.
I know not the answer you want but this part of what your asking for is AC design advice re selectivity local regs apply and would trump any advice given and the Health of the overall system needs to be checked if you believe that it should not have tripped. All the best
are they all the same brand and series type? This can give issues like this
Also there is no selectivity between 16A and 20A breakers, normally you would need a step in between (16A breaker end group should be on a 25A main breaker)
Didn’t know that having two different brands could cause these problems, interesting. RCCB1 in my utility closet is from Hager (AFM420G) and MCB1 near my Victron inverters is from ABB (SC 203-NA).
I’m indeed aware that there is no selectivity between 16A and 20A breakers, but I didn’t expect both MCB1 and RCCB1 to trip in addition to a circuit’s own MCB.
I think the solution is to replace MCB1 and RCCB1 with B25 versions. When designing my system I decided to use a B20 for MCB1 to reduce the risk of blowing the grid operator fuses (C25) in case of a short circuit. I’m not sure if I need to consider my grid operator fuses’ values for MCB1 (between my Victron inverters and my home installation). In some installations I read about previously, I noticed that the same or even a higher value than the grid operator’s fuse was used for such an MCB. For example: the MCB between the Victron inverters is 25A, even though the grid connection is also 25A. This might be OK in case the grid operator fuses have a C characteristic and the installed MCB a B characteristic. I didn’t want to risk blowing the grid operator fuses and therefore selected a B20 for both MCB1 and RCCB1.
Another option might be to use C20 versions for MCB1 and RCCB1.
WIth both options, I would expect that the risk of blowing the grid operator fuses is higher.
