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How Does an RV Automatic Transfer Switch Work? (Detailed Explanation)

Written by Stephen Ryan / Fact checked by William Turner

how does an rv automatic transfer switch works

Have you ever asked yourself, how does an RV automatic transfer switch work? If you did, you are not alone. Many first-time RV owners are clueless about how an ATS operates to keep their RV electric appliances working when switching between pedestal power and generator energy.

In short, the ATS directs the flow of electricity from either the generator or shore power to the RV’s circuit breaker panel. Knowing how the device works ensures a more pleasant RVing experience, keeping you, your family, and your ride safe.

Join me in learning and appreciating the inner workings of an ATS and how it can benefit your RV adventures.

Table of Contents

How Does an RV Get Power to Run its Electric Appliances

Did you know that your motorhome has a 120-volt generator supplying electricity to your appliances? It is different from your RV’s 12-volt battery that runs the vehicle’s electrical system, including the water pump, lighting, vehicle controls, and more.

Your motorhome’s generator supplies electricity to your TV, refrigerator, water heater, microwave, and other modern comforts. You also get to run your RV’s rooftop air conditioning unit. That is why RVing is like bringing your house on the road.

Generators draw their power from your motorhome’s 12-volt battery. In turn, the alternator converts your RV engine’s mechanical power into electrical energy to recharge the battery. If there is a problem with this automotive component, there is a chance your battery will not hold a charge.

When on the road, the engine continuously supplies mechanical power to the alternator for conversion into electricity, storing it in the battery. From here, some of the battery power goes to the generator so you can enjoy all the modern comforts of living.

Suppose you park your vehicle at the campgrounds and plug the shore power cord into a pedestal. The electric appliances draw their power from this fixed power station. When you drive to your next destination, an RV transfer switch activates the generator to let you enjoy a more comfortable ride.

Hence, your RV’s electric appliances draw power from two sources – the generator when you are somewhere without shore power, and a public utility electric station we call a pedestal.

All RV electric appliances connect to a circuit breaker panel, supplied by either shore power or generator energy.

Older RV models have a power cord hardwired to the circuit breaker panel. When the motorhome owner drives in the campground, he plugs the power cord into the pedestal. If the RV owner decides to go, he unplugs the cord and plugs into the motorhome’s generator.

Plugging and unplugging from the pedestal and generator is a tedious process. A motorhome transfer switch simplifies that by automatically directing the flow of electric current from the pedestal to the RV generator, and vice versa.

What is the Usual Layout of an RV Automatic Transfer Switch

A typical RV automatic transfer switch wiring diagram shows you a three-way switch consisting of one output and two input ports.

The output port connects a cable to the circuit breaker panel’s inputs. One of the input ports connects the shore power cord, while the other links to the motorhome’s generator.

When you plug the shore power cord into a pedestal, electric current runs from the public utility station to the switch and the circuit breaker panel to operate the different RV appliances.

As soon as you unplug the shore power cable, the switch draws power from the generator and directs it to the circuit breaker panel.

How Does It Work

We can look at an RV power transfer switch as a traffic policeman, directing electricity from one direction to another. Electricity can only come from one of two sources: shore power or generator.

Motorhome transfer switches prioritize electricity coming from the generator. A logic-controlled sensor activates the device to draw power from one source to another.

If the controller senses that the generator’s charge is insufficient to supply the power requirements of the RV’s electric appliances, it switches to shore power. However, transferring to shore power can only happen if there is a connection between the RV and the power pedestal.

Once the controller detects the generator is at its optimal 120-volt capacity, the ATS switches back to generator input. Meanwhile, the switch drops the connection with the shore power.

Some RV models prioritize shore power, moving the generator as a backup. The motorhome’s AC electrical system switches to shore power when you plug it into a pedestal. If there is a power outage, the switch automatically drops the shore power connection and links to the generator.

It is an efficient system that allows RV owners to enjoy the comforts of home on the road.

There is another type of switch that RV owners have to flip manually. Manual transfer switches have the same fundamental function as automatic ones. The only difference is you must toggle the switch between shore power and generator energy.

It is an inexpensive device but not as convenient as automatic switches.

Why is There a Delay When Switching


First-time RV owners often wonder why their generators do not start instantly right after disconnecting the shore power. Most ATS devices have a built-in 1.5 to 2-second delay timer.

The delay is necessary, ensuring the generator has sufficient power to supply the RV’s AC electrical requirements. The automatic transfer switch still allows trace electricity to pass from the shore power before cutting it off completely.

Why Do You Need an Automatic Transfer Switch

There are many reasons why an automatic transfer switch is a must-have for any RV owner. Not only does it simplify the process of drawing energy from a pedestal or external power source and the onboard generator. It also makes it safer to do so.

Built into the ATS is a gate-like mechanism that prevents electrical back-feeding. This phenomenon occurs if electricity flows in reverse – from the circuit to the source.

Back-feeding can occur when you connect a circuit to a generator during a power outage. Without the switch, the generator also sends electricity to the pedestal. Someone can get hurt if he inadvertently touches the pedestal.

The switch prevents back-feeding from happening and safeguards anyone who goes near or touches the pedestal.

Without the switch, shore power can also overload your RV’s electrical system upon power restoration. There are now two power sources – the generator and the pedestal. The sudden surge of electricity can also over-burden the generator. Overloading the RV circuitry and generator can lead to electrical fires.

An automatic transfer switch solves this problem by ensuring a one-way flow of electricity. If the generator is working, electricity will go straight to the RV circuitry. The same is true when connected to shore power. Electricity will never interfere with the generator’s function.

We can consider an automatic transfer switch as a safety device, allowing us to sleep comfortably in our RVs at the campground. We rest better knowing our motorhome’s electrical system is working optimally and safely.


How does an RV automatic transfer switch work? The ATS is a simple device that guarantees electrical safety in your motorhome. It directs the flow of electricity from either the generator or shore power to the RV’s circuit breaker panel. It also prevents back-feeding, allowing us to sleep soundly at night.

Roving the countryside is more fun if you can assure everyone’s safety onboard your motorhome. The generator lets you enjoy comfortable amenities on the road, which you get to continue using shore power at the campgrounds. Switching between the two is more hassle-free because of the ATS.

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