RVs come in many forms and sizes.  The type and size of the electric service is often relative to the size of the RV.  Today, most smaller RVs come with a 30 amp service. Larger RVs often have a 50 amp service. There is a significant difference between these 2 services.  To understand the differences and why an RV may have a 50 amp service it helps to understand the electrical grid supplying power to the campground. 

 

The electric grid that supplies power consists of 2 hot legs and a neutral.  The current cycles with a frequency of 60 hz which is 60 times per second. Each of the hot legs has a voltage of 120VAC.  For large appliances like an electric oven, a clothes dryer, a well pump or a household hot water heater, the two hot legs are connected to the appliance to supply 240VAC.  This is 2 times the 120VAC from each leg.  The advantage to this is that with a higher voltage, less current can be used.  This allows for smaller wires to be run. 

 

In your house you have the two hot legs and the neutral entering your main breaker panel. You also have a separate ground wire. One 120VAC leg supplies ½ of your panel and the other supplies the other ½. In your RV you will have the same thing if you have a 50 amp service.  If you only have a 30 amp service you will only have one of the legs.  Your campground will have split their 120VAC legs to evenly distribute the loads.  At a 50 amp pedestal, you may see a 50 amp receptacle for a 4 wire plug. The 4 wires for the 50 amp receptacle are 2 hot legs, 1 neutral and 1 ground. Notice in the image to the left that the 50 amp breakers are joined. They trip at the same time. 

 You may also see a 30 amp receptacle for a 3 wire plug. The 30 amp receptacle is 1 hot leg, 1 neutral and 1 ground. 

This panel also has a 20 amp service on the right.

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If you have a 30 amp service in your RV, then you simply have 1-120VAC leg run through a 30 amp main breaker that runs all of the 120VAC components in the RV. If you have a 50 amp service, then you will have 2-120VAC legs, each run through a 50 amp main breaker. With the 50 amp service you will have the loads divided among each leg. This may also be called a split phase.  For example, if you have 2 air-conditioners, one will generally run off 1 leg and the second will run off the other.  

 

One significant difference between a 30 amp service and a 50 amp service is the amount of power.  A 50 amp service does not just have 20 amps more.  You technically have 70 amps more.  The reason is because you have 2 legs, each able to supply 50 amps. The 30 amp service only has 1 leg that is able to supply 30 amps.  Let’s look at this in terms of power.  Power is amps time volts.  A 30 amp service can supply a max of 30 amps X 120 volts = 3,600 watts. A 50 amp service and supply a max of 50 amps X 120 volts + 50 amps X 120 volts= 12,000 watts.  So a 50 amp service can supply 3.33 times the power of the 30 amp service. 

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If you have a 50 amp service but only have a 30 amp service available you will need an adapter.  What is nice about this adapter is it will combine both legs of the 50 amps together.  This will convert your 50 amp service into a 30 amp service. All of your breakers will be live and everything in your RV should work.  Just NOT at the same time!!!!  You are now limited to 30 amps! Speaking of adapters.  Get some!!!  I never complain that I have too many adapters.