120 VAC power
Shore power is the electricity provided to the RV when the electrical cord is pugged into the campground electrical supply box.
The RV electrical cord connects directly to the circuit breaker panel and is controlled by the main circuit breaker. The electrical power is distributed from the breaker panel to all the various power outlets in the RV, through one or more circuits. Each of these circuits is protected by a circuit breaker of it's own.
RV Campground electrical supply outlets must be wired to code when installed to pass inspection. In a lot of parks, that was 20 or 30 years ago! As the receptacles wear out or break, the maintenance guy or owner replace them as needed. Whether they wire them back the way they were or not is up to the competance or knowledge of the replacer guy!
Polarity is important!
120 VAC circuit polarity tester
You can purchase a 120 volt circuit polarity tester for under ten dollars at a hardware store or electrical supply store. The device plugs into an electrical outlet and has three lights on it to tell you if there is a problem and where the problem is. Everyone should have one of these to test every campground shore power outlet BEFORE hooking up the coach to the power source. Incorrectly wired outlets are hazardous! If the tester shows a problem, do not plug your RV into the source - ask for a different site or move to another RV park!
Also, the electrical demands of the RV's in the park (25 years ago), is very different from the electrical requirements today. The park was wired to accomodate the demand at the time and may be woefully inadequate today. As each RV arrives and plugs in, the line voltage of the park electrical system may begin to drop, especially in hot weather, when air conditioners are running. If the voltage drops below about 105 VAC, your AC appliances could be damaged. There are low voltage monitors available in a variety of price ranges that sound an alarm if the voltage falls to a dangerous level.
Another problem is that the transformer that supplies the RV park may have had the voltage turned up to counteract the drop at peak demand. If there are few RV's in the park, the voltage may be too high, also endangering your equipment. An inexpensive voltmeter will enable you to monitor the voltage levels. There is a plug in model that continually shows the voltage on the line.
Ground Fault Interupter or GFI
A GFI is usually found in the bathroom and/or near the kitchen sink. It is a safety device to prevent electrical shock when an electrical appliance is used near a water source. A GFCI monitors the amount of current flowing in an appliance, and if there is any imbalance then it trips the circuit. It is able to sense a mismatch as small as 4 or 5 milliamps, and it can react as quickly as 1/30th of a second.
The GFI in your RV may protect several other outlets downline from the actual GFI outlet. If you find that several outlets are not working check the main circuit breakers and the GFI outlets. A GFI outlet has a "Test" button and a "Reset" button. To reset the GFI, press the reset button. If the GFI trips again then you have an electrical problem in the circuit. Do not use the outlet until the problem is corrected.
The 120 Volt AC circuits in the RV are protected by circuit breakers. These are the same as circuit breakers used in your house electrical system. If a short circuit happens or an overload occurs on the circuit, the circuit breaker will trip and interupt the current flow. As with any mechanical device, circuit breakers can wear out. If you have a circuit that constantly trips, measure the current flow with an ammeter to find the actual current flow. If the breaker trips at an amperage below its rated value, it is defective and should be replaced.
Generators are engine driven devices that provide 120 VAC power when a connection to a shore power source is not available. Repair of the generator is beyond the scope of this article.
Inverters are used when boon-docking to provide a limited supply of 120 volt AC power. They take the electrical energy developed through chemical reations in the battery bank and convert it to useable 110 volt AC current. The amount of current is limited by the battery storage capacity.