How generator neutral-ground bonding for an RV works

How generator neutral-ground bonding for an RV works

 

Hi Mike,
First off, let me thank you for all the hard work you’ve put into No~Shock~Zone. It has been so educational as a new trailer owner and a new father who will soon be taking my son camping for the first time. Thank you!

I am an electrical utility worker in a power plant and have a decent understanding of electrical grounding, induced currents, fault currents, ground potentials, etc. Before reading your article, I didn’t know that my trailer neutral and ground were isolated “floating” the trailer. Now having read your articles I understand both why this is done and the code requirements to do so. I also am clear on the neutral–ground (N-G) bond that exists from the shore power “pedestal” power supply. 

Where I am still slightly unclear is when it comes to my Yamaha EF2000IS that I just bought. I know it has a floating neutral and the generator now labels this very clearly. I understand the function of the neutral-ground bond plug described in your article and how it allows a user to use a floating neutral generator with an Electrical Management System (EMS). My confusion is around if there is no EMS on the trailer. Many people I know just run their floating neutral generator into their trailers with no issues having the whole system floating. It seems some people see this as not creating a hazard and some feel the opposite.

Aside from the code that requires one neutral-ground bond per distributed system, what exactly are the implications of either N-G bonding my generator versus leaving everything floating? From my work experience I feel like it’s a no brainer to N-G bond the generator when feeding my trailer; however, does this make everything safer, i.e., how does the N-G plug affect the function of the electrical protections within the generator/trailer? Or conversely, by not N-G bonding the generator when feeding the trailer, is the trailer like a “hand drill” and by keeping things floating prevents fault currents from returning through ground to the source (usually that’s what we want)? 

Sorry if I’m overthinking this. Once again, thank you so much for everything you have done with No~Shock~Zone – very, very grateful!!! —Kris Homell 

Hi Kris,
Thanks very much.

Honda EU2000i Generator

So here’s how generator Neutral-Ground bonding for an RV works. If you’re powering a single RV that doesn’t have any sort of EMS (Electrical Management System), then the RV’s electrical system doesn’t know or care. If that’s the case, then it’s absolutely fine to just plug your shore power line into an isolated neutral generator. As you’ve noted, most of the inverter generators have floating neutrals, so that’s perfectly safe.

And if you use a contractor generator that already has a bonded neutral, that will be fine as well. Most portable generators over 5kW (kilowatts) fall into that category.

5kW portable generator

Where you get into trouble is when using a floating neutral generator on an RV with a smart Electrical Management System that detects a lost ground at a campsite hookup. Because a floating ground at a campground is so dangerous, EMS units from companies like Progressive Industries are just doing their job and shutting down the power to the RV. But again, since the neutral of the entire RV’s electrical system is floating, it’s not really dangerous and these generators don’t require a grounding rod at all.

Progressive Industries EMS unit

Now, for the final caveat. If you’re using a portable generator to distribute power to multiple RVs (or in my case, a stage full of rock musicians and a mixing console out in the field), then you must not only bond the neutral to the generator chassis, the chassis must be “earthed” to a grounding rod. That’s to prevent a failure in one RV’s electrical system from electrifying other RV chassis running from the same generator. I just wrote about that recently as a reflected hot-skin condition.

So the bottom line is this. If you don’t have an EMS in your RV, then you can use either a bonded or non-bonded neutral generator. If you DO have an EMS installed, then you’ll want to use a bonded neutral generator. And the easiest way to neutral bond something like a Honda generator is using the Generator Neutral Bonding plug available from Progressive Industries, or you can wire it yourself from my articles on No~Shock~Zone.

I do believe that any RV that plugs into unknown pedestal power (don’t we all) should have some sort of EMS protection. Note that this EMS product is more than a mere “surge-strip” to prevent electrical spikes from entering your system. A proper Electrical Management System will not only protect you from lost grounds, it will also shut down the AC power going to the RV if it goes over or under voltage. Accidentally connecting your RV to a TT-30 pedestal receptacle that’s been miswired for 240-volts instead of 120 volts is a very expensive mistake.

Let’s play safe out there…. —Mike Sokol

Mike Sokol is an electrical and professional sound expert with 40 years in the industry. Visit NoShockZone.org for more electrical safety tips. His excellent book RV Electrical Safety is available at Amazon.com. For more info on Mike’s qualifications as an electrical expert, click here.

##RVT791

 

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