Understanding an RV Electrical System – How Does It Work?

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How much power does it REALLY take to run an air conditioner in your RV? Why do appliances cause tripped breakers in your RV? Understanding an RV electrical system isn’t all that difficult. Let us explain… 

Campground Electrical Hookups

How Does My RV Electrical System Work?

Believe it or not, this is such a common question. Yet I’ve heard so many different explanations. Some people have described an RV electrical system with such complexity that I felt I needed a NASA engineer to help me set up my camper for the weekend. It’s a good thing I spent a major portion of my life as a qualified electrician with a pretty solid grasp on the subject. I also spent a portion of my teenage years working in car and truck shops learning the ins and outs of automobile electrical systems.

The Basics of an RV’s Electrical System

Your camper actually has 3 electrical systems. It has a 12 Volt DC Automotive Electrical System, a 12 Volt DC Camper system, and a 120 or 240 Volt AC Camper Electrical System.

RV Fuse Box 1

12 Volt DC Automotive Electrical System

The 12 Volt DC (Direct Current) automotive system controls the lighting on the outside of your camper that deals with driving (or towing) it around on the roads. This system originates with the tow vehicle for trailers, or the chassis on a class A or C units. The battery in the tow vehicle/chassis is 12 volts and provides the power needed to start the vehicle. It is charged by the alternator while the engine is running and provides the needed energy to power the headlights, marker lights, brake lights and signalling lights.

With a towed camper, this system is supplied to the camper via the cable connected at the hitch. Smaller units have a 4 wire connection and larger capacity vehicles will have a 6 or 7 wire connection. The 4 wire cable is usually found on smaller towing vehicles and is used for lighting only. The 6 or 7 wire cable is found on larger vehicles and includes wires that control the brakes on a trailer. Some trailers, usually under 2,000 lbs, do not need brakes, where as the larger tow behind trailers need to have their own brakes to assist in bringing the entire truck and trailer set up to a safe stop . This circuiting is intended for the roadway lighting (and, where applicable, the brakes) only and is not intended to supply power to the 12 Volt DC camper system.

Some vehicles’ trailer wiring will have a wire dedicated to charging the battery on a trailer, but this is generally for the emergency brake actuator battery. (A safety device that causes the trailer brakes to apply in the event that the trailer separates from the towing vehicle). This circuit can easily be overloaded if you tried to power anything additional from it. Overloading it would most likely blow a fuse in the towing vehicle or the chassis fuse box in a class A or C unit.

12 Volt DC Camper system

The 12 Volt DC camper electrical system originates with the battery(s) installed on the camper. While they can be charged from the vehicle electrical system, the batteries are primarily maintained by a charger connected to the camper’s AC (Alternating Current) electrical system. The system is broken up into circuits that are fed from the fuse block in the camper. Check the operator’s manual to find the location of the panel as well as any maintenance that may need to be done.

The 12 Volt camper electrical system provides power to many items in the camper, including:

  • interior lighting
  • exterior lighting
  • water pump
  • some USB outlets
  • the refrigerator (most refrigerators can be supplied by the 12 Volt DC system, the 120 Volt system and the propane)
  • the heater and the blower
  • the emergency warning devices (the carbon monoxide sensor and propane leak detector are also tied into the 12 Volt DC system)

It’s easy to overload the 12 Volt DC Camper System.

12 volt DC systems can be easily overloaded by adding additional items to the circuits. If you do not have experience with 12 volt DC circuits, do not add any new devices to the system without checking with a qualified person. If a fuse blows on a 12 volt circuit, do not replace it until you have found the problem. NEVER put the next size up fuse in.  Using the incorrect fuse size can create a fire hazard.

Boondocking and the 12 Volt DC System

For those that like to Boondock or camp at locations without electrical hookups, you can use the 12 volt system to operate most creature comforts. However, only for as long as the batteries are able to last. Having a small generator can maintain the batteries, if you are allowed to use them. Some camping areas without hookups limit the time you can use a generator, mostly to daylight hours.

RV Fuse Box 2

120 Volt AC (Alternating Current) System

The last source of power in your camper is the 120 volt AC (Alternating Current) system. This is just like the system in your house. It covers all of the outlets, the TV, the microwave, and the AC. It also covers half of the hot water heater (the other half runs off of propane). For those with washers and dryers, they are covered by the 120 volt system.

The 120 power in the camper is supplied by either a 20 amp or 30 amp cord that you plug in while setting up your camper at the site. If you have a 50 amp hookup, you are connected to 240 volts (Don’t worry, you still have 120 volts for your appliances). Again, it is no different than your house electricity, other than being limited to the total amount of power that is available to you.

Campers Use Breakers to Prevent Overloaded Circuits

The power in your camper is protected by a small electrical distribution unit. The unit has breakers for the AC power and fuses (like you find in a car) for your DC power. There are multiple AC circuits to protect the wiring within the camper. However, all of the camper circuits combined are limited by the breaker on the pedestal you plug into.

Why do appliances have a tendency to trip the RV breaker?

Your camper should have a separate circuit for the air conditioner, one for the hot water and another that usually covers all of the outlets including the microwave. This is why when you nuke your breakfast burrito while brewing your coffee, it tends to trip the breaker in the camper.

If this happens, let the breaker rest for a few minutes before turning it back on. (A breaker has a thin piece of metal inside that heats up as the load increases. This is what causes it to trip. You want to let this cool off before resetting it, otherwise it may trip shortly after turning it back on). If you have the air conditioner on while you’re nuking and brewing, you are most likely going to be heading outside to reset the breaker in the pedestal. Since coffee hasn’t brewed and you’re likely not fully awake, don’t forget to put pants on! You can thank me later.

Are certain kitchen appliances unsafe to use in a camper?

I have heard people say that it is dangerous to use a coffee maker or any other type of appliance in a camper. This is BA-LON-Y. We regularly use a coffee maker, an Instant Pot, a slow cooker, a toaster, an ice maker and my beautiful bride uses her hair dryer and flat iron. This is all acceptable as long as you stagger the use. We also only use the appliances while we are at the camper. It isn’t good practice to leave them on when it is unattended.

Instant Pot RV

How to avoid tripping your RV breaker

A good rule of thumb is never apply more than 80% of the amperage of a circuit breaker to a circuit (same for your house). So if the breaker that covers your counter top outlets has a 15 amp trip rating (the number on the breaker handle), you should never put more than 12 amps of load on it at once. This also goes for the breaker at the pedestal. If it is 30 amps, you should never apply more than 24 amps of load on it.

Here are some typical load examples for common appliances:

  • Microwave: 13-14 amps
  • Air Conditioner: 12-16 amps
  • Coffee Maker: 5-6 amps
  • Electric Water Heater: 9-13 amps
  • RV Refrigerator : 5-6 amps
  • Toaster: 7-11 amps
  • Instant Pot: 9-11 amps
  • Air Fryer: 10-12 amps
  • Countertop Ice Maker: 2-4 amps

Can tripped breakers damage an RV’s electrical system?

While tripping the breaker does not damage the electrical wiring itself (that’s the whole reason the breaker is there… to protect the wiring), it can eventually lead to a breaker that trips well below its rated capacity (nuisance tripping). The bigger hazard with RV electrical wiring is that it is always vibrating as you bounce down the road. This can lead to loose connections. A loose connection in an electrical system can lead to excessive heat at the connection. This may result in a fire.

It is not a bad idea to check, or have a qualified electrician check, all of the outlets and electrical connections every once in a while. 120 volts is enough to cause serious injury or even death. Make sure you know what you are doing before you begin doing any maintenance to your electrical system yourself.

Are Extension Cords Safe to Use in My RV?

A similar problem with RV wiring is melting the shore line. This is usually associated with a really long shore line or using it with an extension cord. Longer cords add resistance to a circuit and can cause overloading. Make sure if you use extension cords, you get a heavy gauge extension cord. The larger the actual copper conductor, the less the resistance.

I recommend at using at least a 12 gauge cord for any of your camper needs. 10 gauge is even better. Do not use 16 gauge cords. They don’t really aren’t meant to handle large loads. (The lower the gauge number, the larger the conductor. 10 is larger than 12, 12 is larger than 14, and so on). There is a reason the 16 gauge cords are less expensive. DO NOT use an extension cord on a 30 amp shore line without consulting a qualified person to ensure it is safe to do so.

Phoenix Cruiser RV at Campsite WM

RV Generator Safety

Some RVs have on-board generators that can supply power to the AC power outlets and devices. Generators are also protected by circuit breakers on the unit itself. Know where these breakers are in case your air conditioned breakfast adventure overloads the circuit.

When using a portable generator for power, make sure you set it up away from open doors and windows. You don’t want exhaust fumes building up and giving anyone carbon monoxide poisoning.

Final Thoughts on Understanding Your RV Electrical System

We have packed a lot of technical information in this post, but tried to keep it as understandable as possible. The electrical system in your RV is quite simple and very similar to your home, with the 12 volt stuff added in. You should be able to operate anything you would at home in your RV, just as long as you understand that you can’t do it all at once.

Again, I cannot stress enough, if you don’t have experience with and an understanding of electrical systems, do not do any maintenance or repairs on your own. It is worth your safety to pay someone to do this. So sit back, turn on the AC and enjoy!

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23 thoughts on “Understanding an RV Electrical System – How Does It Work?”

    • Typically, no. The circuit breakers should last the lifetime of the camper. You do not need to proactively replace breakers and there are no maintenance procedures for the type of breakers they use in campers (or homes for that matter), but that doesn’t mean they can’t fail. Breakers can be damaged by exposure to water or frequent condensation. They can also be damaged by being forced to trip too many times. The breakers used in campers are Thermal Magnetic Circuit Breakers and trip for one of two reasons; high load or dead short.

      The first way that they trip is by having too much plugged in and operating at the same time (high load). For example, a microwave and a toaster operating at the same time on one circuit. The high load heats up a little metal filament in the breaker. As it heats up, it contracts and releases a lock mechanism that then shuts off the breaker (trips it). If this occurs many, many times it can alter the physical properties of the filament and cause it to trip under small amounts of load (nuisance tripping). A breaker that trips under normal conditions should be replaced.

      The second way this type of breaker trips is when the wire connected to it shorts (or connects) directly to another power wire or ground. It can be from damaged wiring, a bad appliance or someone sticking a fork into the wall socket. When electricity is shorted, it produces a very fast and very large load, known to electricians as a High Inrush Current (like a power surge). The speed and force of the electricity creates a magnetic field around the wire. Inside the breaker is a second trip mechanism with a magnet. The magnetic field created by the inrush current offsets the pull of the magnet holding the trip mechanism and the mechanism opens the circuit (trips the breaker). If repeatedly tripped, this can cause that mechanism to weaken and prevent the circuit breaker from staying on. Occasionally, one large surge can damage the mechanism and require replacement of the breaker.

      If a breaker is not holding properly or nuisance tripping, not only should it be replaced, but the circuit itself should be inspected to ensure there are no other problems that could be causing it. Something as simple as a loose connection is enough to start a fire, don’t risk your life by googling how to replace your own breaker. If you are not familiar with electricity, hire a qualified electrician to investigate the problem.

    • For an average tow behind camper, fifth wheel, pop-up all of the breakers and fuses are located in a power distribution unit. A power distribution unit contains breakers (for 120 volt devices) and Fuses (for 12 volt devices). This can be located anywhere in the camper, but a favorite spot for many manufactures to put them is under one of the dining booth seats, facing the aisle or living space. There are electrical codes and manufacturing codes that dictate how much space should be maintained around them, so they are not usually “hidden” anywhere. They should be obvious and accessible. Our unit has a little plastic cover that folds down to reveal the breakers and fuses.

      The breakers and fuses should be labeled from the factory, as per most regulations. But… it does not mean it will be done or done in a way that is easy to understand. A breaker may be labeled “REC”, which means receptacle. It could be protecting a single receptacle in the bathroom, or it may be protecting every receptacle in the camper. Mounted appliances typically have their own breaker. These would include the refrigerator, the hot water heater and the air conditioning. Other items can be isolated or combined with multiple other devices. The microwave is commonly connected via an outlet and shared with many outlets in the camper.

      Driven units may have a power distribution box for the living space and fuse boxes for the chassis (driven part of the camper). Fuse boxes could be located under the dash, under the hood, or just about anywhere else. Units with Generators may have a separate box for the generator or may have a transfer switch that can choose between the power cord or the generator.

      DO NOT EVER remove a cover for a fuse box or power distribution unit if you do not have the experience and knowledge to do so. Many contain 120 volts or 240 volts. Accidental contact may cause major damage, severe injury or death. Something as simple as a loose connection is enough to start a fire, don’t risk your life by googling how to work on electrical systems. If you are not familiar with electricity, hire a qualified electrician to investigate the problem.

    • Thank you! We are so happy to hear that it was helpful. We tried to keep this article simple but still give a lot of info!

  1. Locating your breaker box or circuit breaker can help protect RV’s electrical system from many issues. This breaker panel will be within most RVs’ interior and mounted onto a wall close to their floor. You might even find it inside one of your RV’s external storage bays.

  2. Lightening struck near our house and now our camper’s electrical system seems to be shot (we had several appliances that no longer worked after the strike as well). It appears the lightning traveled through the wiring in the crawl space of our house. The camper was plugged into an outlet on the side of the house. We have submitted a claim on our home owners insurance, but I’m having trouble explaining to the adjuster how the strike affected the camper. Can you offer a layman’s explanation? Thanks.

    • Oh wow – that’s awful! Hmmm… as far as an easy-to-understand explanation, when you plug your RV into your house electric, your RV is basically an extension of the house’s electrical system. So anything that could affect or destroy your home electrical service could certainly affect your RV’s electrical system.

  3. I Have a 2020 Cedar Creek cottage model that after putting on my air conditioning which usually I do not use I have three sockets that do not work and I can’t seem to find what the problem is and I need help

    • A circuit breaker should always be replaced with a breaker that is the same size/amps as the one you’re replacing. If you aren’t sure how many amps your breaker is, definitely take it to an RV service technician to ensure you get the correct breaker installed.

  4. Hello,

    I have a 1995 28′ Ford Conversion Van that all the ac electric stopped working on after using it as a cooling station on a very hot day for backstage band access. While it would trip a house breaker (that is what is was plugged into) I could eventually (presumably after allowing stuff to cool slightly) get the air conditioner and ac power working by flipping the breaker back on and the third time I changed the circuit it was plugged into.

    After the third “fix” ac power never would work again.

    I have traced power to what I presume is called the power distribution unit in hopes of finding a shutoff circuit breaker for the entire system but alas it just feeds to the metal box that contains the AC power for the inside of the RV.

    Is it possible the power distribution unit failed and needs to be replaced? Any other options to consider.

    • It is possible that the unit failed.. but your best bet is to take it to an RV technician. While service can be pricey, they do know what they are looking at and know how to safely test and diagnose an electrical issue.

  5. I’m sorry I’m not replying,but need help, the fan in my panel box running constantly,I’ve been living in my tv and I haven’t had a battery in five months ,but everythings been working fine without it, today the fan turned on and hadn’t stopped, I went and bought a new battery it’s still running what is wrong HELP

    • Are the breakers in your trailer for the 120v power only? I am asking because when I have all the breakers turned off and not connected to shore power on the batteries (I am using 2 – 6v batteries connected in series) I still have power to my lights, fridge and pump. The issue I am having is that when we are done camping and our fresh water tank is empty the pump keeps running unless I disconnect batteries.The only way I can get the power off is to disconnect the batteries which seems odd to me because then how would the batteries recharge when I am towing the vehicle?

  6. Recently moved into our 2020 momentum toy hauler. We have an additional stand up freezer in the toy hauler garage. It’s cure plugged into outlet insight hauler. Should this be moved to separate extension cord? It’s not running all the time, and I touch cord to make sure it’s not warm. Is this an overload concern?

  7. This RV breaker box helped my car stay safe when I switch from onshore power to RV power. To wire a breaker box, I need a 50-amp breaker, a circuit breaker box, and several tools, such as a wire stripper, drill and bits, a screwdriver, and a craft knife. First, I choose where to place the breaker box reasonably. Position the breaker box on the wall and secure it with screws. Loosen the fastener securing the breaker box’s dead-front panel. Remove this section and touch the leads with a voltage meter to confirm there is no current. 

  8. I have a new 12v 24v rooftop Air conditioning unit installed, but I’m unsure whether or not it needs to be plugged into the power inverter or should it be wired direct to inverter batteries in the floor?

    I’m no good with electrical and do not have a wiring diagram. LoL


  9. An RV’s circuit breaker is typically located in one of two locations: either in a metal switch box near the main electrical panel or in the distribution center near the power converter. The disconnect switch may be located elsewhere, so it’s best to check the owner’s manual for your specific RV model.

  10. My large slide on 2015 Sprinter (Keystone) 5th Wheel stops when opening and closing. After less than a minute a I hear a click above the slide and it will allow it to run for a bit, then repeat. I was told it is likey not the motor but a resetting cuicuit breaker that is located near the battery. I am going to get it out of storage but looking for advice prior. Thanks in advance!


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