Understanding an RV Electrical System – How Does It Work?

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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