All the CU's I have seen have the bus bar at the bottom, is there a good reason for this or is it just convention?
I'm configuring some DC supplies through a small DIN rail box and it would make much more sense to have the bus-bar at the top. If there's no very good reason for the bus-bar at the bottom then I'll put it at the top. Presumably the MCBs don't mind which way the current flows through them, similarly for the main switch.
Something to do with gravity in a failure ?
Crabtree used to have their busbar along the top, Schneider do one now with the same config for their AFDD boards.
There has recently been a change to introduce MCBs/RCDs which *are* directional, designed to be used where PV, batteries, generators or EVs with V2L are used ... such devices would have Lin/Lout/Nin/Nout markings on the terminals ...
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