Correct voltage for 50 amp service

westernrvparkowner wrote:
You would think natural selection would have thinned the herd on all the incorrect posts about 50 amp service, but NOOOO. A 50 amp RV service is wired exactly the same as a 4 wire 240 volt dryer or range plug. There are two hot wires both providing 120 volts. There is neutral wire and a ground. The two hot leads are out of 120 degrees out of phase, and when you measure across them you get 240 volts. In residential wiring, there is NO single wire carrying 240 volts, 240 volt appliances use the fact the two separate hot wires are out of phase and realize the 240 volt potential by combining the leads inside the appliance.
As for how the adapters work, a 30 amp (at the pedestal 3 wires) to a 50 amp (coach plug with 4 wires) ties the two hot leads coming from the RV to the single 120 volt power source at the pedestal. A 50 amp (at the pedestal 4 wire) to a 30 amp (coach 3 wires) just connects one of the two hot leads at the pedestal to the hot wire going to the coach. The other hot line from the pedestal is not connected to anything, it is just an insulated blank inside the adapter.
The only thing in a home service you need to watch out for is the older 3 wire 240 connection. They were used for boilers, welders and certain electrical heaters. They are out of favor and new service almost always use 4 wire receptacles. A 3 wire 240 receptacle look a lot like a 30 amp receptacle but there is actually no neutral wire. There is two hot 120 volt lines and a ground. The ground pin on 3 wire 240 volt home wiring is different than the ground pin on a RV 30 amp service that has only one hot wire and a neutral in addition to the ground. A 30 amp RV plug will not fit into a home 3 wire 240 volt outlet without using a whole lot of brute force to deform the ground pin. A good safety step is to learn how to use a simple multimeter. They are very cheap, simple and safe and very good insurance against improper wiring.