|DIY Solutions for RVs and beyond
Notes on Electrical 110/240 Volt Shore Power
Here is a little review of the basics that help get our RVs energized with Household type electricalMost motor homes and travel trailers have what is called "A 30 Amp 110 Volt Shore Power Cord". This cord is usually a heavy extension containing 3, #10 gage wires, one end is wired directly to the RV and the other end terminates at a male plug designed for connecting to a 30 amp 110volt receptacle. This plug/receptacle combination is oddly shaped, as there are 2 angled flat prongs for the power circuit and one round prong, which is the Ground Connection. Lots of time this plug is mistaken for older type 220/230-volt electric dryer or electric range connection and a receptacle or adapter is wired up and when connected to the higher voltage it is likely to damage the RV’s electric components, and create a dangerous situation. This happens often enough to mention here and is one of the first things to pass on to someone new to camping vehicles.
An alternative is the Dog Bone type adapter given it’s name for having the shape more or less of what with a stretch of imagination could be compared to a large bone. Dog bone adapters eliminate strain by being flexible and usually are of higher electrical quality.
Larger Motor homes and travel trailers may be equipped with a 50-amp power cord that has 3 #6 wires for power and 1 #8 wire for ground. This power set up is said to have 2 legs, (or circuits) of 110 volts each. The plug is the now standard 4 prong 50 amp 240 volt type found on modern electric ranges. All kinds of power adapters are available for this plug configuration, the most important thing to note is that most adapters, dog bone or other simply put the same 110 volt power from the 110 volt wall receptacle on to both legs, (circuits) of the power cord. This limits total usable power to the power available at the wall receptacle or outlet. 50-amp service can be connected to a properly wired 50-amp 240-volt receptacle, which will utilize the 2 legs of 110 volts. Typically there is no 240-volt electrical equipment installed in production RVs until we get into the bigger rigs, Bus conversions, custom units, etc. So for the most part we see 110-volt washer dryers, air conditioners, and electric cooking appliances.
In any case there are many possible configurations to manage power inside the RV as well as many devices designed to help with power management tasks. Throw into the mix an onboard 110-volt generator and manage to be totally self-sufficient. The most interesting system is the load shedding power management system that will disconnect or "shed" circuits in a prioritized order. This system asks you to select your available power and will prevent overloading by monitoring total amp load and disconnects circuits so you wont trip a circuit breaker from your source of power.
The big topic is safety mostly concerning the use of extension cords to connect your RV to a source of power. It is always stressed that you use a proper 3-wire extension cord of appropriate size "Wire Gage". The ground prong not only connects the RV to ground at the power source it also aligns the other prongs as to be in proper polarity. Now one of the most important things about the internal wiring of a RV is that the neutral wire is floating, or in other words is not connected or "Bonded" to Ground. One of the reasons why is that if anything were making a connection between the RV’s ground and neutral circuits and the polarity of the extension cord was reversed, or that the polarity of the source power was reversed, the RV would have a HOT SKIN condition or meaning that anything connected to electrical ground via the wiring including the vehicle chassis the siding if metal, door frames, etc. could be on the Hot or dangerous side of the 110-volt. This is aggravated by how well the tires insulate the RV from earth ground. This scenario may seem a little far-fetched but Hot Skin conditions happen and there is still a lot of backwards wiring out there.
When planning any electrical switching for your RV always switch the Neutral as well as the Hot or "Hots".
In most cases the internal wiring of your properly installed onboard Genset has its Neutral bonded to Ground. This case the source ground "The Genset", and the RV Ground is electrically the same.
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