WHAT ELSE is running on that same circuit? Resistance elements (things that make HEAT from electricity) are very big users of juice. Too many on one circuit trips the breaker: Here's how to trip your breakers:
Have your Water heater on electric instead of gas
Use a microwave full blast
Run a small heater while also running a heat pump on HEAT.
Blow dryer going?
Toaster, electric skillet, induction burner or other electric cooking device.
The heater all by itself shouldn't pop the breaker - unless it's loose or defective - but add two of the others on top and Kablowee!
Here is a test - If you have a long heavy duty extension cord and your fantastic fan has a pull out screen, pull the screen, open the fan cover -but keep the fan off, thread the cord out to the power stand and plug it into the 15/20 amp outlet. Close down the lid on the fantastic fan as far as it'll go manually. Plug in the heater and crank it on high. Turn on whatever else you normally were using when the heater popped the breaker. If the breaker on the campground's power hookup blows before you add any other load, the heater is definitely at fault. If the other appliances cause the breaker on the pole to pop, then you've exceeded the voltage at the plug in point. If something still blows the breaker IN the trailer... having isolated the fan would prove the problem is in the trailer wiring, not the fan.
If the fan runs fine on a separate feed... you're just not used to having to conserve electricity. You went over 30 amps and the circuit breaker did what it's supposed to do to prevent fires.
Yesterday is history,
Tomorrow is a mystery,
Today is a gift,
that's why they call it the present.