Agree with nearly all (all except the "not drawing enough" part) of the above. Particularly Doug, and RV tech who takes the time to share his experience with us.
Wanted to comment that we had and older 30A coach with 13500 A/C and Atwood "gas" (standing pilot type) water heater that had a 120 VAC element (OEM not HottRodd etc.) And a small counter top microwave. With that setup we could run "all electric" on 30A. A/C, hot water, microwave, converter, coffee maker.
Current 30a coach has 15000 A/C (Coleman Mach as was the old 13500), a Suburban DSI/Electric water heater, and the common Samsung microwave. We have to "load shed" all the time in summer. Can run A/C plus any ONE plug-in 120 VAC resistive appliance (coffee maker, waffle iron, toaster...) but NOT A/C plus Microwave or Water Heater.
Breaker panel in the old coach used full-sized GE residential style breakers and I never had to replace one. Coach we have now uses paired Cutler-Hammer breakers. Main and A/C are in a single 30/20 and I believe one side heats the other and causes it to be extra sensitive.
As an A/C ages, compressor develops higher resistance and draws more amps. Also increases load on RUN capacitor. If the RUN capacitor's weak, it'll draw still more. If you don't have a Start Assist on your A/C, adding one could help. If it has an assist that uses a PTC resistor, replacing with an electronic or relay type can also help. Many of us use SUPCO SPP6e, an electronic start assist with only two wires to hook p.
Chris Bryant is our other regular RV Tech contributor. He has lots of information for DIY work on his website (BryantRV.com). He also posted a blog item (I can't find anymore) about cleaning the rooftop A/C. To do a complete cleaning, the sheet metal "nose" of the unit (once plastic shroud removed) comes off. That exposes the Evaporator Coil, Condensate Pan, and Drain Holes. Cleaning both coils reduces amperage use. Chris claims by 2A. Won't help startup but still worthwhile. Cleaning the other coil (the Condenser), by the outdoor fan, helps, but Evaporator is the one that gets fouled with dust, cat hair, mold, etc.
If you do the cleaning and want to send a pic of the Capacitors (probably under another access cover) we can tell what you have. Should be either two single capacitors, two terminals each, one as Fan Run and the other Compressor Run. Or a dual capacitor (three terminals) that handles both. Above that, there might be Start Assist, usually a plastic capacitor while the RUN ones are metal.
