Words of Wisdom: “…most people think that to have “RV” type shore power you need those special 30/50 amp plugs. I have a 115v plug. The male end of an extension cord (heavy gauge) that I have cable tied to the inside of my receiver hitch so it’s hidden.” – Captain_Dapper1)
Shore power (“grid power”, “mains”, “wall outlet power”) is AC power derived from the electric grid. Shore power can run AC loads directly in campers so equipped, but more commonly it powers a converter/charger that runs the 12v house system.
20A power receptacles are similar but the “hot” leg has an additional spur.5) This arrangement allows 15A plugs to go into 20A receptacles but prevents the heavier duty 20A plugs from being used in a 15A circuit. Boondockers and vandwellers will likely set up their shore power to run on the 15A. Because of the backward-compatible 20A socket they will be able to use their 15A plugs at both 15A and 20A hookups.
The 20A outlet is rated for 2400W.6)
Note: using a 10A circuit breaker on the RVs AC breaker box will prevent tripping a residential circuit breaker when the RVer might not have access to reset it. A 15A breaker might or might not, depending on whether the RV or residential breaker trips first.
A 'dweller can safely power a 15A RV from a 30A outlet with an adapter. 15A Extension cords should be 12-14ga for 50' cords and 10-12ga for 100' cords.
Mike Sokol of RV electrical fame, says:
if there’s a 20-amp circuit breaker and 12-gauge wire feeding a 15-amp outlet, it’s actually rated for 20-amps of current. There’s an exception in the code as well as UL allowing this, so don’t worry. If you’re on a 20-amp breaker with 12-gauge wiring, then you have a 20-amp circuit, even if it’s using a NEMA 5-15 outlet.7)
The RV can also run off a 15A/20A outlet with an adapter but would have to be careful about loads (heavy loads like a single A/C unit, electric cooktop, or microwave would have to be run one at a time).
50A to 30A adapters will use one leg of the outlet to feed the RV with 50A.
A shore power port is designed to let you plug power cables into the side of your van or RV. As discussed above, RVs typically use 30A/50A service – they use this kind of port.
Vans typically use 15A ports. Some are pre-cabled so you can plug the inside cable to a power strip, breaker box, or other distribution device. A converter/charger can then be wired to the distribution point.
Before plugging into shore power the RVer may want to test the receptacle for “good ground, open circuits, reversed polarity and safe voltage.”14) Note that the tester reports conditions at the time of testing; it might tell you if voltage is too high right now but not protect the RV if the voltage spikes later on.
Dogbone surge protectors are inexpensive, but they are generally only good for one surge (or maybe several small ones). More full-featured surge protectors will disconnect power to the RV in over/undervolt conditions and will reconnect after a certain period of stability.