What do you mean about preventing fires? 800 watts at 240 volts is only 3.3 amps. Are you saying there are German houses where you could plug a solar power system into an outlet whose wires would pose a fire risk if they carried 4 amps? Because I think the minimal rating for a German residential outlet is 16 amps, which would be 3520 watts at 220 volts.
While I agree that you can't just arbitrarily raise safety-based limits, not all "safety-based limits" are actually safety-based, and I'm pretty sure you've misidentified the safety concerns in this one.
That's 3.3 amps behind the breaker. So if your wiring is set up for 16 amps you can now draw 19.3 amps before the breaker kicks in. That's within the safety margin. But if you allow PV to feed in more you exceed the safety margins and can cause the wiring to overheat.
Hmm, I guess you're right. If your oven is plugged into a different breaker than the one where you plug in the solar panels, that doesn't happen, but most people won't know which outlet is on which circuit. Thank you for explaining!
caveat - 20 amps on a b16 breaker will take a very long time (minutes to hours) to trip; in practice, you may never see it tripping during normal usage, but yeah your walls will get a bit warmer.
While I agree that you can't just arbitrarily raise safety-based limits, not all "safety-based limits" are actually safety-based, and I'm pretty sure you've misidentified the safety concerns in this one.