Is it necessary to have a separate indicator lamp to show that there is alternative power present in the DB if the inverter already has 'Mains on' and 'Inverting' indicator lights on it?

VisN I would prefer to do that and I do think that SANS will agree. My way of reasoning is that even when you trip the isolator/CB between your inverter and backup loads the lights on the inverter will stay on. This for me is not a correct indication of what is going on in the DB. I do my installs with 2 lights, 1 for mains and 1 for alternative power, and goes for both solar and generator installs.

 

Here is the SANS regulation.

a) supplies power only to certain circuits in a distribution board, a power-on
indicator (visible or audible) shall be provided on each such distribution
board as well as a notice indicating that the standby power main switch
shall also be switched off in an emergency,
b) only supplies a part of the electrical installation, the notice shall also be
displayed on each distribution board in that part of the installation (see
6.6.1.1(d)).