So, I need to know WHICH breaker is tripping when using both the AC and the microwave.
If it is the MAIN; it is indeed a "total amps used" issue.
If it is the Microwave, then there could be a problem with the microwave or a low campground voltage issue.
Same with the Air Conditioner. If the Air Conditioner breaker alone is tripping, you most likely have low voltage from the campground. Since the Air Conditioner's motors need "Watts" to turn over, low voltage will require more amps than normal to start up.
P (in Watts) = E (in Volts) times I (in Amps).
An Air Conditioner that needs 1800 Watts at 120 volts "to run" needs a constant 15 amps to do it. During startup, that same Air Conditioner could need a momentary amp blast of 20-22 amps (normally not long enough to trip the breaker).
Now drop the voltage to 110 volts. The Air Conditioner still needs 1800 Watts to run, so it will draw 16.4 amps now. That Start Up draw of 20 amps at 120 volts now becomes almost 22 amps and if it needs 22 amps it becomes 24 amps. That may be enough to trip that breaker.
A hard start capacitor can help by lowering the need for these momentary peak amps and your AC will start without tripping the breaker.
I have seen campground voltages below 105 volts during 100 degree weather when the campground feeds are aluminum wire.
As to your second question, your camper will need to be completely rewired to include a new power center and all new feed wires rated for 50 amps on each leg including the new one.
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