50 amp coach on 30 amp power

Well depending out side temps you could get by with one heater, or just use your furnace.
That said if you excede 30 amps you will likely trip either the the Post breaker, or the main in your coach.

If you exceed the 30 amps the circuit breaker on the pedestal should pop and shut off power to the coach. If we are on a 30 amp site we switch the water heater to propane only, set the inverter/charger to only use 5 amps to charge the batteries, and set the reefer to propane only (if it's an absorption type). This will allow more power to be used on other items without popping the breaker on the pedestal. Our air conditioners are also heat pumps and we have found them to be the most efficient way to heat the unit as long as outside temps are above 40°. If below 40°, we use the furnace(s) which use very little electricity. Electric heaters are about the most inefficient way you can heat a coach.

2oldman wrote:
I don't know, but why don't you use the furnace?

Probably because electricity to run the heaters is included in the cost of the site, but propane costs extra. That's why I do it.

If you exceed the 30 amps, then the circuit breaker on the pedestal should trip.

Several things can happen.
IF....you have the adapter at or near to the supply pole, nothing bad should happen to the RV equipment.
BUT.....
The adapter might overheat.
The 30 amp receptacle might overheat.
The 30 amp breaker at the supply outlet might trip.

It is really NOT good to exceed a 25 amp draw on a 30 amp service because you don't know how good the feed really is.

I don't know, but why don't you use the furnace?