On Fri, 25 Oct 2019 14:15:01 -0700 (PDT), DManzaluni
wrote:


Where is this flat located? What model load center is installed?
WHat circuit breaker is currently installed??????

Sorry, not sure of these technical details but I sure feel more comfortable trusting your statement that it is unusual to put a 15 amp cb on wiring sized for 20 amps, rather than my super's supposition that 'all wiring behind the box is the same'!

By the way, I should mention that when the cb trips, it does so after a minute or so of the microwave being turned on. It doesnt happen immediately.
Then we KNOW it is overload, not surge. What goes out with the
microwave when the breaker trips? List EVERYTHING on the circuit - and
with it ALL turned off/unplugged does it still trip?