On Monday, 5 March 2018 20:13:32 UTC, ARW wrote:
You then use different phases with B20 MCBs at DB1, feed them through
13A SFCUs with 2.5mmT&E and join them at the load side of the SFCUs
about 30m away with some more 2.5mm T&E.

Join what to what? Phase to phase?

I'll guess the 3PH MCB as it has overcurrent on two phases.

Owain