By Mike Sokol
Welcome to my J.A.M. (Just Ask Mike) Session, a weekly column where I answer your basic electrical questions. If you’re a newbie who’s never plugged in a shore power cord (or ask – what’s a shore power cord?), or wonder why your daughter’s hair dryer keeps tripping the circuit breaker, this column is for you. Send your questions to Mike Sokol at mike (at) noshockzone.org with the subject line – JAM.
People are always talking about how a bad ground on an RV can cause problems such as a hot-skin condition. So how exactly is an RV grounded? I don’t see a ground rod anywhere. I’m pretty stupid when it comes to electricity, so can you please explain? —Sam (the Sham)
You don’t mind if I call you Sammy, do you???? [From the editor: You can call him Sammy if he can call you Mikey.] This is a great question that confuses a lot of electricians and even electrical engineers at times, so don’t feel stupid. I’ll show you how your RV is supposed to get its ground connection if it’s properly wired. But since this is a J.A.M. session I’ll save the in-depth explanation for another time.
Just the basics
Yup, your RV doesn’t have to have any sort of ground rod to be “grounded” since the green conductor in your power cord (technically called the EGC for Equipment Grounding Conductor) provides that grounding path.
In fact, a ground rod is a pretty poor ground since the dirt beneath our feet isn’t a great conductor of electricity. Certainly it’s conductive enough to get shocked, but it’s not enough of a conductor to trip a circuit breaker.
How do I know this? Well, first of all it’s written right into the electrical code and all my engineering textbooks. But I recently did an experiment where I confirmed just how much fault current an 8-foot ground rod could get rid of, and it’s not much more than a few amperes. So if a ground rod doesn’t actually ground your RV, what does?
Your RV’s electrical ground is dependent on the aforementioned green ground conductor in your shore power cord being properly connected to the service panel’s neutral/ground bonding point either at your house or the main electrical service panel of the campground your RV is plugged into.
Note that the campsite power pedestal doesn’t require a ground rod, nor should it have a ground/neutral bond (that green screw). That neutral bond is only allowed to occur at one place, which is inside of the main service panel. Note in the diagram that this connection is also where the bare copper wire from the power company service panel’s ground rod is connected to. So it’s actually a Ground/Neutral/Earth bonding point where they all come together. And that’s what your RV chassis is eventually connected to.
So this is a great reason to maintain your shore power cords properly, including any dogbone adapters or extension cords. Never use a damaged electrical cord or connector since it can cause all kinds of problems.
OK, everyone. Remember that electricity is a useful and powerful force, so we all need to pay attention to safety precautions while using it.
Let’s play safe out there….
Mike Sokol is an electrical and professional sound expert with 50+ years in the industry. His excellent book RV Electrical Safety is available at Amazon.com. For more info on Mike’s qualifications as an electrical expert, click here.
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