120-Volt Electrical Basics: Part 1

It is important to understand the basics of 120-volt power and how it supplies components in your RV. The power pedestal or “Shoreline Power” at the campground typically has three connections for 50 amp, 30 amp, and 15 amp power.

The 50 amp plug in is for larger coaches to supply 240 volts, 120 volts per “leg” to supply power for two roof air conditioners and other appliances.

The 30 amp plug provides 120-volt power limited to 30 amps so typically only one roof air conditioner can be use at a time. The 15 amp plug in is similar to a residential outlet and is only used for smaller trailers.

The 120-volt shoreline power comes into your rig to the distribution center which has a main breaker and then circuit breakers for 120-volt appliances, outlets, and the converter.

Each circuit breaker should be labeled with the component it powers and the amp capacity of the breaker. Power is supplied from the distribution center to the appliances and outlets by an electrical commonly referred to as Romex that has conductors or wires inside a protective sheeting known as the cable. For most appliances there would be three wires, hot, neutral, and ground very similar to the electrical connection in your home.

Any outlet located close to a water source such as the kitchen sink, bathroom sink and shower, or outside outlet must be protected by a ground fault circuit interrupter or GFCI. This outlet is a device that shuts off an electric power circuit when it detects that current is flowing in an unintended path such as through water or a person. It is used to reduce the risk of electric shock, which can cause the heart to stop or cause burns. They can also prevent some fires, like when a live wire touches a metal conduit.

Typically RV manufactures will use the recognized GFCI outlet with test/reset buttons in one location, then another Romex wire is connected to that same GFCI outlet on the second set of terminals and is routed to other outlets which is called “ganged” as there could be several outlets connected in this same fashion just like the outlets in your garage or living room of your home. If you have a GFCI outlet at the first connection, all other outlets on the circuit are protected by the GFCI but will usually not have the test/reset button and are known as “dummy plates”. They should have a GFCI Protected sticker on them, but that does not always stay on.

This means you could have one or two GFCI test/reset outlets on different circuits and if that outlets trips, or becomes defective, the other outlets on that “gang” or circuit will not get power. It’s a good idea to test which outlets are on what GFCI main outlet. Get a non-contact voltage tester from any home improvement store and press the test button on the GFCI outlet. Now use the non-contact voltage tester to verify what outlets do not have power. These will be connected or “ganged” to that outlet.

Back to the distribution panel, another 120-volt power supply goes to the converter or battery charger which also has it’s own circuit breakers. This provides a 12-volt charge to the deep cycle house batteries as they become depleted and will also have an amp draw that you will need to be aware of if you are on a 15 amp or 30 amp shoreline source. Newer models can draw up to 9 amps to provide more charging power but does limit the use of other appliances on the lower amp systems.

That is an overview of the 120-volt electrical system in your RV. It is similar to the set up in your home, with just a few differences, and the addition of a 12-volt converter thrown into the mix. Coming up next, we’ll learn to understand the power power requirements of your rig, and how to manage it!

Discussion
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13 Responses to “120-Volt Electrical Basics: Part 1”
  1. raph

    RV Make: holiday rambler, RV Model: ambasador, RV Year: 2001

    how do you change head light lens

    Reply
    • paul light

      RV Make: thor, RV Model: windsport, RV Year: 2001, Brand: dewald hydraulic, Model Number: ser. 11320

      slide out rooms

      Reply
  2. Jerome Imbriani4

    RV Make: Keystone, RV Model: Springdale SP287RB18, RV Year: 2018

    If, when using your air conditioner and another high usage appliance such as a toaster, you trip a breaker on the campground pedestal, can you cause damage to your RV or its appliances. What about the RV circuit breaker or fuse.

    Reply
    • Customer Service

      Hello Jerome,

      You typically will not cause damage to your RV as the voltage is shut off when the shoreline breaker trips. What can happen is when you are drawing more than 30 amps before the breaker trips, your shoreline cord can get hot if you are not using a dedicated 30 amp cord, so make sure if you are using an extension cord, it is rated for your power!

      Thanks,
      David RVRC Video Membership

      Reply
  3. Billy

    RV Make: Cougar, RV Model: High Country, RV Year: 2013

    How to stop the slide out from jumping up and down while going in or out. This is cable type

    Reply
    • Customer Service

      Hello Billy,

      I would start by inspecting the cables and chain inside access by taking off the upper decorative frame of the room. There you will find the motor, chains, pulleys, and cables. If it’s sagging below factory recommendations, it will jump at it pulls up the tension and catches up. Attached is the service manual from the BAL Accuslide. Also check underneath the inside and outside to make sure the rollers are moving freely and you don’t have anything obstructing from the inside.

      Thanks,
      David
      RV Repair Club Video Membership

      Reply
  4. gfhetherington

    RV Make: Forest River, RV Model: Rockwood Class C, RV Year: 1993

    How to replace the main door

    Reply
  5. dlfreeman17

    RV Make: Thor, RV Model: Hurricane, RV Year: 2004, Brand: Intellitec, Model Number: 00-00524-400

    When I start engine it shuts off in a few minutes and then no key or dash power. Could it be my ignition lockout relay?

    Reply
    • Customer Service

      Hello,

      To provide more specific troubleshooting information on your ignition issue, we need the make, model, and year of your rig or tow vehicle? Also, will it attempt to start after letting it sit for a period of time? Or is it in shut down now with no start?

      Thanks,

      David
      RV Repair Club Video Membership

      Reply
  6. Brian

    RV Make: 91 Fleetwood, RV Model: Pace arrow, RV Year: 91

    Not geetting power from shoreline .

    Reply
    • Customer Service

      Hi Brian,

      It depends on what kind of shore cord you have, if you have the kind that pulls out of the wall it is typically connected directly to the power distribution center. You would have to check the voltage coming into the main breaker. If there is voltage at the power pedestal and nothing coming in, there could be a break in the cord wiring and would need replaced. If your shore chord attaches to the outside of the wall, check for voltage coming from just the cord itself when plugged into the pedestal and not the camper. If that is fine, plug it into the camper and check voltage at the breaker, if not voltage at the breaker than the outside wall connection is either bad or has bad connections on the rear side of it. If there is no access inside to the back of the shore connection, you will have to pull it off the wall from the outside and check the connections. The first thing to really do is make sure power is being sent to the cord. If using an adapter or extension cord, the problem could lie in there. The best thing to do is trace the voltage going through the unit to try and track down the problem.

      I hope this helps!

      Dan
      RV Repair Club Video Membership

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      Reply
  7. shellypatrick1

    RV Make: Coachman , RV Model: Encore , RV Year: 2006

    I need to know where the wiring and fuse is for my passenger power seat

    Reply
    • Customer Service

      Hello,

      The wires for the seat are going to be under the seat. They then go to the fuse panel with the rest of the dashboard and front console components. I have seen some with in line fuses just under the seat. The fuse panel can be located in the chassis owners manual. They are in different locations for all chassis. Some manufactures offer online wire diagrams, Winnebago does this. You may be able to get others by contacting the manufacture of your RV.

      I’m sorry I can’t give you an exact location but I hope this helps!

      Dan
      RV Repair Club Video Membership

      Reply