Another multiplus RCD/GFCI question

[victronitnerd]

I have almost got my installation fully mounted and wired up ahead of actually starting to program the inverter for my scenario. But after a quick test I need to change the way the circuit protection is setup as I have no selectivity when it comes to the RCD’s/Breaker’s tripping.

I note the MP manual says I need a 50a MCB upstream of the MP but I wanted additional protecion with an RCBO (GFCI) but testing RCD trips on the downstream circuits caused the upstream one to trip. My idea is to install 100ma ones that feed the MP which they gives earth fault protection to the MP but not to trip uneccesarily if a downstream circuit has a fault.

Anyone offer any guidance to what im proposing? or things to look out for.

Current setup:

Proposed changes (changed MP feeds to MCB’s and the isolation switches to 100ma RCDs):

[B51-technician (Alfredo)]

Hello @victronitnerd , I think we discussed your topic here in that post:

Earth/neutral bonding with multiplus

Hello @ShallowAl . Interesting question Cascading RCDs requires at least the right RCD types in terms of current and trigger delay. In the diagram attached (sorry for the german text, source ABB), you see a main RCD (in your words, the upstream RCD) and a cascaded RCD. The two curves and its areas should never interfere to avoid a double release. That’s the general part of the story from my point of view. Main RCDs as first ones in the cascade are “S” types (selective). I…

In a nutshell, cascading RCDs requires the right RCD types at the right position - in terms of current and trigger delay. Main RCDs, as first ones in the cascade, need to be “S” types (selective).

[victronitnerd]

Many thanks, I will look at that post and calculate the appropriate protective device.