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RVelectricity – Generator neutral bonding basics

Dear Mike,
I know your NoShockZone article on generator bonding is getting “dated” at this point, but I just wanted to say THANK YOU for publishing it. This problem has “puzzled” me for a decade now and I’ve looked at many online articles in the past – to no avail. There is so much bad information on the Internet, and the manufacturers really aren’t any help at all.

I wasn’t sure what to trust, but I read this and watched your YouTube video and it made perfect sense. I made up one of your plugs this morning and tested it on my Honda 2000 Companion generator. It worked like magic. I have to run out and get some gas, and then I’m going to fire up my Champion 3500 watt inverter and test the plug on it. I have no reason to expect that it won’t work the same way.

This is a simple and cheap fix for a nagging problem. It should be a “feature” article adopted by all of the online forums. —Bill Burgess

Dear Bill (and a few hundred others),
Thanks Bill. And even though I first wrote about this floating neutral issue and designed a simple solution for generator neutral bonding back in 2013, it’s still a very popular article on my NoShockZone.org blog, and has received nearly 85,000 views since I wrote it (and more than 14,000 views this year so far). Here are the basics of what my Neutral/Ground bonding plug does, and how to make one. I’ll cover more of what RV neutral bonding is in my RVelectricity newsletter this Sunday, so make sure you subscribe to it.

Here’s the basic generator neutral bonding article reprinted with better pictures of how to build my bonding plug. And be sure to read the Sunday edition of RVelectricity. See you then….


When a portable generator won’t power your RV

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 am 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

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, and there can be only one Ground-To-Neutral 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 Ground and Neutral buses “bonded” (connected) together externally as part of the service panel’s earthed safety ground system. Again, lots of 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.

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 TRC or Progressive Industries, your voltage monitor is checking for the Neutral and Ground voltages to be very close to each other, probably within 3 volts or so. This works well if you’re 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 voltage protection device on your RV, then you may never know that your generator has a floated neutral (unbonded N-G bus).

Here’s a really simple test you can do to see if your generator has a floating neutral. Just plug in a basic 3-light tester that you can buy from any big box store for $5 or less, and see if it shows an open ground. If you get an open ground indication, then the generator likely has a floating neutral and needs a N-G bonding plug to work with an intelligent/EMS surge protector. If you get the proper indicator lights showing it has a ground, then you don’t need an external N-G bonding plug. See my video on testing generators for a floating neutral here.

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 and Yamaha have floating neutrals.

I discussed this very point with Honda engineering, and they confirmed that their inverter generators have floated Neutrals and simply say that you should follow all local electrical codes for bonding-grounding. So your EU3000 isn’t providing the Neutral-Ground 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.

And be aware that there are some really inexpensive Chinese generators that are neither fish nor fowl. That is, they don’t have a floating neutral, nor do they have a bonded neutral. Instead they make 60-volts AC on the hot wire, and 60-volts AC on the neutral wire. Sorry, but I don’t have a fix for that one.

It’s pretty simple to wire your own special “Neutral-Ground Bond” jumper cable for your Honda or Yamaha generator which will allow you to power your RV through its voltage protection device. You can obtain or make a dummy 15- or 20-amp “Edison” plug with the Neutral (white) and Ground (green) screws connected together with a piece of 12- or 14-gauge stranded wire (see photos on the left and below right and left).

Just be sure that you jumper the Green (Ground Screw) to the White (Neutral Screw). The color of your jumper wire can be white, green or bare copper since this is jumping the Ground and Neutral bus together.

This N-G jumper plug can be plugged into one of the generator’s unused 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 (photo right). 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.

Note this is a generator-only N-G bonding plug which should be only plugged into a portable generator while powering your RV. NEVER plug this into an internal outlet in your RV as that would create a potentially dangerous code violation.

Finally, if you’re not comfortable “rolling your own,” you can purchase a ready-made version of my Generator N-G Bonding Plug from Micro-Air.

Let’s play safe out there….

 

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.

 

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Blake
14 days ago

Hi Mike,
My ’21 F150 truck has a 2kw pro power onboard floating neutral generator. It throws a ground fault indicator whenever I use it to try and charge an otherwise perfectly functional portable battery (which does not trip GFCI’s in the house, and which passed an ohm test). Would this plug work to ground the F150’s generator and bypass the GFI error, or would this be like plugging it into an internal outlet in the RV that could cause a code violation error?
Thanks.

Mike Sokol
13 days ago
Reply to  Blake

I have an idea…. Let me think on it a bit.

Tony Infante
3 months ago

Hi Mike
I have a Westinghouse i2500 inverter generator for backup power on my 30 amp travel trailer. I’ve read your articles about the N-G bonding plug and purchased the south wire plug on your recommendation. Works as you described and I have two yellow lights on my plug in tester. My question is if I use the generator to power my home refrigerator during power outage do I need to use the bonding plug? Thanks for all of the great information you share with all of us.
Tony Infante

John
3 months ago

“And be aware that there are some really inexpensive Chinese generators that are neither fish nor fowl. That is, they don’t have a floating neutral, nor do they have a bonded neutral. Instead they make 60-volts AC on the hot wire, and 60-volts AC on the neutral wire. Sorry, but I don’t have a fix for that one.”

Hi. I’ve encountered this a few times, and it can be dangerous if the generator is connected to a grounded system that has a ground-neutral tie in it. The best thing I have found is to use a two-prong plug in only… don’t connect to the generator ground at all and make sure that the generator itself is not grounded including anything metal on the generator being in contact with the actual earth or conductive materials.

-J

MikeO
6 months ago

Thanks Mike,

I have this situation with a Progressive Industries RRT-50 circuit tester. My inverter generator only has one 30 Amp L5-30R receptacle, and 1 NEMA 5-20R receptacle. I use the L5-30R for connecting to my travel trailer. Surge protector does not include this floating neutral monitoring, so no operational issue so far. I have made the neutral-ground bonding plug, it resolves the issue.

Since I only have 1 NEMA 5-20R receptacle on the generator, the bonding plug takes my “spare” plug in out of availability. Can that receptacle be providing the neutral & ground bond, and still be used?

Can I:
1) make an short “extension cord” that bonds neutral & ground at the plug end (next to the inverter/generator) and then power something on that extension cord?
or
2) do neutral & ground bonding in the plug of the cord that inserts into the L5-30R receptacle, and then use that cord to provide service to my travel trailer?

Great article!

Ted
11 months ago

Thanks, Mike. Before I retired, I was working at Tacoma Power in Tacoma Wa. At the time, I was using my EU3000is Honda to run my Artic Fox 28F TT. Worked fine until I added the Surge Guard 35530 Hardwire Model.
Then, you know the story. My Surge Guard 35530 was not happy! A bit of internet search revealed an “edison plug” was needed. I asked my electrical inspector – coworker if they had heard of and “edison plug”, and they said no. I was somewhat dubious if it would solve the problem. But, alas it did!
My 40 some years of employment were in the telephony industry, as a central office technician, half of it for ma bell. Lots of low voltage DC, but not much AC.
Once I learned about the single N-G connection point, it remined me of something we did in the central office. A “single point ground” in an entire central office to avoid ground loops, and the resulting AC hum that will likely result. Thanks for what you do! Good article.

Linda J Hughes-Belford
11 months ago

Hi Mike, I have watched your video on grounding a floating neutral.

I have a duramax 4850 dual fuel generator, with a metal frame around it, and the manual instructs me to ground it to the ground with a copper stake.

Obviously, this would be a hassle when camping.

I do not have a surge protector on my travel trailer, so I am not concerned with that aspect of the neutral ground situation. My question is instead one of safety. With combining my neutral and ground afford protection akin to grounding my generator to earth. Are there any precautions I should take? .

Thanks in advance.

joe florio
1 year ago

I have 2, 2000, hondas, that i hook up with parallel cables, how do i use the floating neutral plug. Thank you

Michael
1 year ago

I have a Hughes Autoformer which reports a ground fault. I have made a grounding plug but it still does not like it. It either reports a ground fault or that wires are reversed depending on whether I’m using one of my Westinghouse 2200s or they are in parallel. Not sure what else to try…

Steve Audet
1 year ago

I tried a bonding plug on my inverter as the one for sale above was listed for inverters as well as generators. The inverter detected ground fault and went into protective load.

Steve Audet
1 year ago

Dear Mike.
 I have a motorhome that I wanted to use an inverter to power a plug that the shore power plug would plug into.  That way no additional internal wiring and modifications would be needed to provide AC power to my rig.  The shore power cord utilizes a built in Progressive EMS that does not like the unbonded Renogy 2000w inverter and shows an ungrounded condition and will not connect. 
 I liked this design as I would be either plugged into the inverter powered plug or shore power. One plug can only be plugged into one place at a time
Then I ran into the floating ground problem that the EMS didn’t like, the same as your generator article fixes.  My inverter has a wired output on the front as well as two 110v outlets.
Do you think that a N-G bonding plug in one of the outlets on the front of the inverter would work on this situation as well?  

Captain Bazza
9 months ago
Reply to  Steve Audet

I’m sad to report that it didn’t on my inverter.

Rueben
1 year ago

I have a Honda EG 2200x generator that is making 60-volts AC on the hot wire, and 60-volts AC on the neutral wire. My surge protector in the RV is telling me I have a wiring fault? How do I ground it?

Phill
1 year ago
Reply to  Rueben

Hey i think by adding this neutral to ground plug on the 120v generator outlet will fix this its worth a try also ground the generator with a ground rod if it has a lug to do so. Also much thanks to the author this helped me a ton.

Mark
2 months ago
Reply to  Rueben

Rueben, I think you will only succeed in introducing 60 volts to all grounds and chassis in your RV creating a potentially dangerous situation. That is if the generator doesn’t detect this short to ground and just shut down. Like Mike said, he doesn’t have a fix for the 60/60 Chinese generators.

Matthew Gusenius
1 year ago

Could you leave the generator attached and transfer back to shore power?

The transfer switch will physically cut the hot and neutral going to the generator, but the ground would still be there. If the bonding plug is still inserted, or the generator is internally bonded, that would make the neutral line a part of the grounding for shore power. I would hope that the ground going to the shore power pedestal would be the path of least resistance in a short, but you never know.

Tim Ferrari
1 year ago

Hey mike!! Thanks for sharing!

What if I have one of the 240v inverters with 2 hots and a ground? Is it possible to use this into a panel? Run a hot to each slot, ground to chassis and just not use the neutral? Or how can this work? or can u buy something to create a neutral? Let me know! Thanks!

Jeff Arthur
2 years ago

If using 2 Honda 2000’s will only one of these need a cheater/grounding plug ? Or one for each unit ?

Retired firefighter Tom
2 years ago

After I had installed a power monitor system in a new 5th wheel back in 1997 I learned that it would not allow my portable generator to power the RV. Checking the error codes I made a plug as you described and the generator then worked. It was a good thing that a Home Depot was less than a block away. I didn’t know the “whys” until your article. Thanks for the explanation. it makes sense now why it didn’t work the first time.

Bob Godfrey
2 years ago

Many thanks for sharing your knowledge with us all Mike, I always manage to learn something from your articles proving that you truly can teach an old dog a few tricks!