Our current fifth wheel, as well as our previous one, is wired for 30 amp service. For the most part that’s adequate for our needs. But it didn’t take us too long to learn that 30 amp service has it’s limitations. Especially in the summer when we need the air conditioner.
There are several appliances on most RVs that few RVing newbies consider, the 1500 watt roof air conditioner which draws around 12 amps, the heating element in the refrigerator draws about the same when it’s on electric as does the electric heating element in the water heater.
Most larger RVs are wired with two circuits, usually one circuit down each side, with a 20 amp breaker protecting each circuit. Any two of the appliances above running on a circuit will likely trip a 20 amp breaker. For example, if you have the air conditioner on and decide to use the microwave on that same circuit, you will likely trip the breaker.
Keep in mind that though you are able to run up to 20 amps on a circuit you will have to limit usage to 10 amps on the other circuit since the RV itself is protected by a 30 amp circuit breaker. Fortunately, RV manufacturers generally balance amperage requirements between circuits. For example, they may place the air conditioner on a circuit with a string of outlets while the other circuit will have the refrigerator and water heater and kitchen outlets.
To get a better handle on what your appliance load is, check the owners manuals you have or the stickers on the appliances to see the watts or amps they have listed. Watts divided by volts gives amps used. Shore power is 120 volts (or thereabouts) so a 700 Watt microwave is drawing about 6amps. It takes a little math, but it is simple math.
You may trip a breaker a few times until you learn what combination of appliances you can run at the same time but it’s not rocket science and you’ll soon learn how to live within the limitations.