If the water heater is on electric and wanting to run at the same time a 30 amp breaker will trip.
Are you referring to YOUR main breaker or the the pedestal breaker?
If you are tripping the pedestal breaker and the A/C and microwave is all that is in use the pedestal breaker is likely weak.
Take a good inventory of exactly what was running. Low battery pulling a lot from the converter? Outside outlet have a fry pan connected? Large fan outside? Just things to look for.
Chuck - Sparta, TN
2012 Jay Flight 22FB, 2 x Honda EU2000i
2013 GMC Yukon XL Denali AWD
EDUCATION is what you get when you read the fine print.....
EXPERIENCE is what you get when you don't.