Generator Neutral Bonding Plug (Update)

I invented and promoted this simple gadget that allows an inverter generator to power an EMS surge protector. (Rerun from Jan 2023)

Dear Readers,

In response to several inquiries about how to make your own neutral/ground generator bonding plug, here’s the full DIY article I wrote more than 12 years ago.

UPDATE:

SOME GENERATORS NOW INCLUDE A GFCI BREAKER ON THE 20-AMP OUTLET THAT MAY TRIP WITH A NEUTRAL BONDING PLUG

I have a design for a generator dogbone adapter that includes the Neutral/Ground bond in the twist-lock plug. That should work under all circumstances.

When a portable generator won’t power your RV

See my video on testing for a floating neutral by clicking on the picture below.

I received this email from a reader who wants to power his RV from a Honda portable generator.

“I have a 2011 Fleetwood 40-footer. I’m trying to get my Honda EU3000 generator to power up the motorhome for a few items. My display after plugging in will show NO LOAD. This generator will power anything else I try such as a 30-foot trailer with one air conditioner, compressor, etc. I also have a Coleman 5000 and that will power up the motorhome.

I have an adapter cord 50-amp female going to 30-amp (3 prong) male. The Honda worked with my 2002 Monaco hooking the same way. The reason I like to use the Honda is when I am at the track this time of year, there is no need to run the motorhome generator since there is no need for air conditioning. I have called Honda and they were no help. —John Z., Purcellville, VA.”

Basic neutral/ground bonding theory

John, all RV electrical systems are wired with their Ground and Neutral buses floated (unbonded from each other). There are lots of good reasons for this, most specifically that it’s an NEC and RVIA code requirement that the safety ground wire never carries any load current. Also, there can be only one Neutral-to-Ground bonding point in any distributed electrical system in the USA.

Now, when you’re plugging your RV into power from a building (your garage outlet) or campground (pedestal outlet), your RV has its Neutral and Ground buses “bonded” (connected) together externally as part of the service panel’s earthed safety ground system. Again, lots of good reasons for this, but the fact is you can only have a single N-G bonding point according to the National Electrical Code and RVIA building codes.

When a floating neutral generator won’t work…

So when your RV is powered by its on-board generator, this N-G bond connection is created by the transfer switch set to generator mode. But when the transfer switch is set to receive shore power, your RV expects the external power source to bond its Ground and Neutral wires together.

Now, if you have an inline voltage monitor system from a manufacturer such as Surge Guard or Progressive Industries, your voltage monitor is checking for the Neutral and Ground voltages to be very close to each other, probably within 30 volts or so.

This works well if your RV is plugged into shore power that’s properly grounded and bonded, but this voltage protector can be tripped off by plugging your RV shore power plug into a portable generator without an internal Neutral-Ground bond. If you don’t have a EMS voltage monitoring device on your RV, then you may never know that your generator has a floated neutral (unbonded N-G bus).

Generator types

Contractor-type generators such as your Coleman 5000 are generally N-G bonded internally, which is why it runs your RV just fine. However, many portable inverter generators from companies such as Yamaha and Honda (your EU3000, specifically) have floated Neutrals (no internal Neutral-Ground bond) since they expect an external N-G bond to happen somewhere else. And while RV-approved generators may have an internal N-G bond, it seems that many of the most popular portable inverter generators from Honda, Predator and Yamaha have floating neutrals.

Honda help desk couldn’t help

I discussed this very point with Honda engineering, and they confirmed that their inverter generators have floated Neutrals and they simply say that you should follow all local electrical codes for bonding and grounding. So your EU3000 isn’t providing the Neutral-Gtound bond that your RV requires to think it’s getting properly grounded power, while your Coleman 5000 has a Neutral-Ground bond already so it operates your RV properly. Seems crazy, but that appears to be the scenario.

DIY your own…

It’s pretty simple to wire a special “Neutral-Ground bond” jumper plug for inverter generator which will allow you to power your RV through its EMS voltage protection device. You can obtain or make a dummy 15-amp “Edison” plug with the Neutral (white) and Ground (green) screws jumped together with a piece of 12- or 14-gauge wire (see photo below).

This G-N jumper plug can be plugged into one of the generator’s unused 15- or 20-amp outlets, and the entire generator’s electrical system will be N-G bonded. You can then use the other 20-amp Edison outlet or the 30-amp outlet to power the RV.

Just be sure to mark this plug specifically for its intended purpose. It won’t really hurt anything if it’s plugged into a correctly wired home outlet. But it will create a secondary N-G bonding point that could induce ground loop currents and create hum or buzz in a sound system. Doing that will also guarantee any GFCI outlet in the branch circuit to trip with even a few mA of load current.

Buy one that’s factory made

If you’re not 100% comfortable wiring your own N-G bonding plug, then you can buy one from Amazon for less than $10 HERE.

I keep one in my gig-bag for when I have to power sound systems from a Honda generator, and it works great for that application as well. But if you don’t have any sort of EMS/Advanced surge protector, or you’re not powering sensitive electronics, you probably don’t need an N-G bonding plug at all. But when you need it, you’ll really need it.

Note that this is a generator N-G bonding plug which should only be plugged into into a portable generator while powering your RV. It must never be used to create a bootleg ground in a residential or RV outlet that was not properly wired with a ground conductor.

Some of the products above have affiliate links. This means that, at zero cost to you, I will earn a commission if you click through the link and finalize a purchase.

Let’s play safe out there…. Mike