How to wire 3 to 1 phase switch + bypass (European grid)

This is a solution for emergency cases when no power available and loads are within 1200W.

I have 3 phase power in my apartment and Multiplus II 48/1600 inverter/charger for backup. The idea is to put 2 switches (3+3 and 3+3 with extra module) in the middle after the main switch like this (Scenario 1). When they're both in position "I", all 3 phases work as usual, Multiplus isolated.





When grid power is gone, I can manually switch both to position II (Scenario 2). Now the apartment is powered from L3 that is backed up by Multiplus.



1. What happens if the first switch is turned to position "I" before the bypass by mistake (Scenario 3)? In this case N goes through Multiplus, but all 3 phases connected.



I see 4 possibilities if load applied to other phases:

• Multiplus is fried;
• Multiplus falls to error mode;
• works fine if total loads are within 16A (Multiplus transfer switch limitation);
• all works fine.

I'm not an electrician and made this scheme intuitively.

2. I'd appreciate if someone could share a ready-made solution.

If anyone is interested, here's my solution with ABB OT63F4C I-0-II switch (4+4). There're also special switches for this purpose like Sontheimer ULO63/4T/NS/Z101/F976 or Kraus & Naimer KG20A K950 VE2 F437.

You're feeding one phase of inverter output to L1, L2, L3?

That results in I(N) = I(L1) + I(L2) + I(L3), which may be excessive current.

We have the same issue in the US for "multi-wire branch circuit".

Hedges said:

You're feeding one phase of inverter output to L1, L2, L3?

That results in I(N) = I(L1) + I(L2) + I(L3), which may be excessive current.

We have the same issue in the US for "multi-wire branch circuit".

Click to expand...

I have only single phase loads and this is for super emergency cases, like war in my case.
When the switch in position "I" - all 3 phases work as usual, inverter/charger can work as a charger only from L1.
Position "II" - the whole apartment feeds from L1 that is backed by inverter/charger with battery. L2, L3 inputs isolated.

I posted the same thread in community.victronenergy.com, topic "3 phase to 1 switch + bypass wiring", not sure if direct links allowed by the policy here.

You can post links, just no "affiliate links", which have extra characters at the end used to direct royalty payments.

Multiplus II 48/1600 - 1600VA?
Not a problem, current output much less than ampacity of a wire.