Generator use while on shore power…

Will anything bad happen if you run your generator at the same time you’re plugged into shore power?

Dear Mike

Wonder if you could give me some advice concerning a generator. I know that you’re supposed to exercise your generators every so often just to make sure that they run properly.

The question I have— when you’re running your generator to exercise it. Should you unplug your RV from electrical current? Secondary question would be can you do any damage to your RV if you leave it plugged into an outlet while running your generator? - Mark R

Hey Mark,

Great question. There’s nothing to worry about since all RVs with an on-board generator will have a way to separate generator power from shore power.

So you don’t have to unplug your RV from shore power while exercising the generator, and you won’t damage your RV if you leave it plugged into shore power while running on generator power.

The Automatic Transfer Switch (ATS)

While some RVs will have an interior power plug you swap between shore and generator power, the vast majority will have something called an ATS, which is short for Automatic Transfer Switch. Here’s what’s acturally happening inside of each relay (called a contactor).

As you can see from the wiring diagram below, there’s a pair of relays with an interlock of some kind, which automatically selects between shore or generator power. Sometimes called a Generator Transfer switch, here’s a look at how they’re wired.

A few definitions:

• The job of the ATS is to be a traffic cop between the pedestal shore power and your on-board generator power

• They come in two sizes: 30-amp and 50-amp RV power

• They can also include a built-in surge protector

• Some also have EMS under/over voltage protection

• There’s a 20- to 40-second delay after the generator starts up to wait for the AC power to stabilize before transferring over to it

• The default is generally to use shore power unless the generator is running

• More complex ATS systems can start your generator automatically if shore power fails

Let’s play safe out there… Mike