Originally Posted by rsscully
Assuming you have a 30 amp service in your camper at 120 volts you have ~3600 usable watts. You could only run 2 heaters at a time on high and consume 3000 watts leaving only 600 to run everything else in your camper. Those two heaters would also have to be on separate circuits(breakers), probably 15 amp each and capable of 1800 watts per circuit. If it was a 20 amp then you would have ~2400 usable watts on that circuit. But you still have only 3600 watts available for the entire system. Drawing more watts/amps then a particular circuit is capable of will quickly overheat the wiring and trip the breaker.
disclaimer: I am not an electrician
Someone else may be able to describe the situation more accurately.
Excellent post rsscully, electrician or not.
Here is the boring part, but once you understand it, then you will have a better understanding of how much stuff you can turn on at a time...either per circuit, or per total.
Watts = Voltage X amps
or another way to look at is
Amps = Watts divided by voltage
Taking what you know from the heaters tag:
Amps = 1500 watts (high setting) divided by 120 volts
So doing the math, it takes 12.5 amps to run the heater on 1500 (high) watts or 6.25 amps on the 750 (low) watts.
Most subcircuits in your travel trailers are going to be controlled by subcircuit 15 amp breakers, so you cannot exceed 15 amps per subcircuit by much if everything is correct. Depending on how your particular RV is wired, it could possibly have about all the outlets on the same subcircuit....or could have some outlets on one subcircuit and some on another.
So what this means, then EVERYTHING on that subcircuit needs to stay at/below 15 amps to keep the subcircuit breaker from tripping. You also have a master power circuit which can be 30 amps on some TT....and thus all the subcircuits added together cannot exceed 30 amps, or they trip the master 30 amp circuit breaker.
You have to practice power management, and not exceed the amps per subcircuit or master circuit. This includes televisions, microwaves, coffee pots, hair dryers, space heaters, water heater elements, air conditioners, and so forth as for anything in your RV that operates off of 120 volt power.