shore power 110 or 220

myredracer wrote:
There are some non-electrical professionals here making incorrect statements.

The pedestals have both 120 and 240 volts available but almost all RVs are designed to operate everything at 120 volts. FWIW it's 120 & 240 not 110 or 220 and you always want to be operating at as close to 120 volts as possible.

And the reason that 50 amp RVs normally do not have 240 volt appliances is to allow the shore power cord to be plugged into a 30 amp, 120 volt pedestal. The NEC currently only requires 20 percent of an "RV park" to have 50 amp pedestals. As of 2005, only 5 percent of an RV park was required to have 50 amp pedestals. Finding a 50 amp pedestal in a CG can be very hard in the high season. Some CGs may have exceeded code requirements, but the majority have built to min. code requirements. Old RV parks may even have NO 50 amp pedestals.

If you plug a 50 amp RV into a 30 amp pedestal using an adapter, the RV's panel and shore power cord will have both hot sides of the 120/240 volt circuit connected together inside the adapter as shown in the 1st diagram below. Although you end up having 50 amps at 120 volts available up to the point of the pedestal, the 30 amp breaker in the pedestal limits you to 30 amps. No technical reason why you couldn't use 240 volt appliances but if plugged into a 30 amp pedestal they sure wouldn't work very well at 120 volts...

IMO it's very wrong for RV manufacturers to be selling 50 amp RVs to people when they don't tell buyers idea how hard it is to find a 50 amp pedestal in a CG.

Hank MI wrote:
All I can say is WOW!

No neutral canceling can occur at your breaker panel. That means the neutral line must be capable of carrying 100 amps and need to be twice as large as the hot legs.

On this comment, this is incorrect. The current on the hots in a 120/240 volt cancel out on the neutral. For ex., if one leg was drawing 40 amps and the other 20 amps, the current on the neutral would be 20 amps. If both hot legs were carrying the same 40 amps, the neutral would have zero amps flowing in it. A neutral is there to handle the highest imbalanced current in a 120/240 volt circuit and the neutral wire is normally sized to match that of the hot legs. In some cases, code allows a reduced neutral size like on a service into a building.

Circuits that are 120/240 volts are not normally referred to as having phases although the current is flowing 180 degrees apart. A 120/240 circuit is 240 volts with a center tap grounded at exactly 1/2 way as in the 2nd diagram and the current in each 240 volt leg flows in the opposite direction and alternates one way to the other at 60 times/second.

There are a few RV parks (CGs) out there that have been wired at 120/208 volts which is more often seen in industrial and commercial facilities. If did in fact have anything in your RV that is designed to operate at 240 volts (dryer for ex.) it would only produce 75 percent of it's rating but anything rated at 120 volts would be unaffected.

You misunderstood what I was saying. I said if both hot legs were in phase, meaning supplied from the same source hot leg then no neutral canceling would take place. If the 2 hot legs are 180* out of phase then neutral canceling would take place. People keep insisting the 50 amp supply is 2 120v supplies. Technically and by code it's a 240v supply as the 2 hot legs are 180* out of phase. As i said earlier it's no different than the service coming into your house. Almost everything in your house runs off 120v, one of the 2 hot legs. It's quite possible to have no 240v loads at home.

Why people keep insisting that the RV 50 amp supply is some how different is beyond me. It's a 240v 50 amp supply. How the 2 hot legs are used to supply 120v or possibly together to supply 240v is irrelevant. Same thing occurs in your home but it's still a 240v supply.