Yep, you're right, and that's normal (though not all main breakers are 30 amp).

Look at your house's breaker box, and you'll see the same thing. If you add up all the individual breakers (other than the main), you'll end up with a lot bigger number than the main breaker is rated for. That's fine, since what you really want to do is to prevent the mains coming into your house from bursting into flames.

And FWIW, it's the same in a car, where you have a big fuse protecting a host of circuits that collectively can draw a LOT more amps than the main fuse could supply.

The end result is safe - no circuit, including the mains, are going to be overloaded with the properly sized breaker box design. Just because you COULD turn on everything in the coach at once doesn't mean it was designed to let you do that without popping the main breaker.

Rich Mondor wrote: "if you combine the A/C and fridge i gather you'd pop the main breaker like this coach will."

Rich, I gather you have a non-GMC finished coach, eg Coachman or the like. But even a little 30 amp main breaker should easily run a roof A/C and a refrigerator at the same time. Roof A/C takes about 15 amps (except at start-up), and the refer should only take a few amps, whether it's the old AC/DC Norcold compressor type or the more common Propane/Electric absorbtion type. If you're sure nothing else is pulling power and these two things are popping your main breaker, I'd check for 1) voltage drop from an undersized extension or shore power cord, or 2) a bad main breaker. (Yes, they can wear out if tripped many times.)
FWIW, I commonly run my refer, buzz box, and one roof A/C on a 30 amp circuit, via a 100' extension cord to my barn, but it's a big 6AWG cord. I have also run both roof A/Cs on a 30 amp service until the park manager yelled at me for running up his electric bill. (When does 30 amp service not allow you 30 amps? At the Royal Gorge KOA!)
I have an AC voltmeter in my coach, and usually shed load if it gets down to 100 volts.
HTH

Matt,

Reading your answer "Be aware that there is a neutral and an safety ground, and they are not the same as in a dwelling. There should be bars for both and neither should be bonded to the box itself. The real safety ground (Green) should be be bonded to the either the ground at the generator frame or the shore power source. This is necessary to preclude a "Hot Skin" condition where the entire coach has a voltage that is above ground."

Are you saying the ground from the shore cable should be kept electrically isolated from the coach body? That is what I'm reading anyway. The ground bar in my OEM electrical box is fastened directly to the box while the Neutral bar is isolated from the box and is not connected to the ground bar. The Neutral and Ground should be connected at the source of power of course. But I believe the ground cable of the shore power should be connected (bonded) to the coach frame and body. The ground wire should also be connected to the case (box) of every appliance (A/C) and electrical outlet as well as the outlet box. Otherwise what is going to protect you if a "Hot Skin" condition does occur?

Maybe I just read it wrong?