Today I want to discuss the difference between a 30-amp and 50-amp RV electrical service in simple terms. Let’s get started.
The plug on the power cord with a 30 amp service has 3-prongs.
At the campground power pedestal there is a 120-volt hot wire, a neutral wire and a ground wire. Using a simple equation, 120-volts multiplied by 30-amps equals 3,600 watts. This means an RV with a 30-amp electrical service cannot exceed a maximum of 3,600 watts or 30-amps. A 30-amp electrical service is used on RVs that don’t have large electrical demands or load requirements. There is typically one roof air conditioner, a microwave or a convection oven, a refrigerator, a television and several outlets throughout the RV to power 120-volt appliances and devices. Larger RVs and RVs equipped with two or more roof air conditioners, residential style appliances, entertainment centers and washers and dryers come equipped with a 50-amp electrical service. On an RV with a 50-amp service the plug on the power cord has 4 prongs.
This is a 50-amp campground receptacle. There are two 50-amp 120-volt hot wires, a neutral wire and a ground wire. This is referred to as a 120/240 split phase service. In simple terms the two 50-amp, 120-volt hot feeds are used to supply two separate 50-amp 120-volt legs to the RV’s power distribution box. The electrical load in the RV is balanced between these two 50-amp 120-volt feeds. Using our equation, 120-volts multiplied by 50-amps equals 6,000 watts, and because there are two 50-amp 120-volt lines the wattage is doubled for a maximum of 12000 watts. That is a huge difference when compared to a 30-amp service with a maximum of 3,600 watts. And that is why you can use more electricity in an RV with a 50-amp service than you can in an RV with a 30-amp service.
If you measure the voltage across both hot leads at the receptacle you will get a reading of 240-volts, but it’s important to understand that a 50-amp RV service uses the two separate 50-amp 120-volt hot legs to supply power to the RV.
A question I get asked frequently is, if you plug a 30-amp RV into a 50-amp service using a 30 to 50-amp adapter will it increase the amperage in the RV. The answer is no. Your RV is still a 30-amp service, you are simply using an adapter so your 30-amp 3-prong plug can plug into a 50-amp 4-prong plug service. On the other hand, if your RV has a 50-amp service and you use a 50 to 30-amp adapter to plug into a 30-amp receptacle at the campground you limit what you can use in the RV to 3,600 watts.
Not to confuse the topic, but I want to mention that some higher end RVs do have appliances that run on 240-volts. All of that is made possible by the way the unit is wired.
But, almost all RVs with a 50-amp service are wired such that the two 50-amp, 120-volt lines are used separately. In other words, some of the appliances are wired to one hot leg of the 50-amp service and the remaining appliances are wired to the other hot leg of the 50-amp service.
That explains why there are two 50-amp breakers at the pedestal and power center – one for each hot leg. But even though there are two breakers marked “50”, they do not operate independently. The entire circuit will trip if one line is overloaded.
Finally, this is another good reason to have a 50-amp surge protector with voltage protection on your 50-amp rig. It tests both lines (L1 & L2) of the 50-amp service and protects all your appliances regardless of which 50-amp leg they are on.
If you have a 30-amp RV service watch my video titled “Living on 30-Amps”
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