RVelectricity – Just Ask Mike (J.A.M.): How to Neutral/Ground bond parallel generators

2
RV Electricity

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. This week I discuss a generator Neutral/Ground bonding plug.


Dear Mike,

I have a Honda 2000i generator. When I plug in the bonding plug, everything works great and my EMS does not complain when powering my travel trailer.

But if I plug in a second Honda generator using the parallel wire kit, do both generators need the neutral ground plug? Or will one suffice since they are now wired together? Thanks. —Jon

Dear Jon,

You’re in luck, since I’m the guy who invented the generator Neutral/Ground Bonding plug some 10 years ago. But first, here’s a quick review of what a Neutral/Ground Bonding plug is, and why you might need one to use an inverter generator with your EMS/Advanced Surge Protector.

Just the basics about inverter generators…

All modern inverter generators have what’s called a floating neutral. That is, the neutral and ground connections inside of the generator are isolated from each other. That’s fine for most things, until you use your portable inverter generator to power an RV via an EMS/advanced surge protector from Hughes, Progressive or Southwire. That’s when the confusion begins.

No ground?

Because these EMS/advanced surge protectors are monitoring the ground connection for a fault, when you plug one into a generator with the neutral and ground isolated from each other, the Electrical Management System “brain” thinks you have a broken ground wire that could cause a hot-skin voltage on your RV. Therefore, it shuts off the relay that allows the power to go to the RV. If you plug a basic 3-light outlet tester into an inverter generator with a floating neutral, it indeed shows you an open ground. Remember, this has nothing to do with a ground rod in the dirt, which no RV with a built-in or portable generator needs.

What then?

In fact, this is how the campground pedestal normally supplies the ground to your RV’s shore power cord.

Well, I knew that all onboard RV generators had a neutral-ground bond in place via the ATS (Automatic Transfer Switch). So I postulated that a simple male Edison plug with the neutral and ground wire bonded together would create the correct Neutral-to-Ground reference voltage, and stop the EMS from tripping off.  And, indeed, it works exactly as I envisioned it.

Warning: This generator bonding plug must only be plugged into the generator outlet, NOT into an outlet in your RV. 

No, I’m not fooling anything or creating a dangerous electrical situation. In fact, it appears that my simple Neutral/Ground Bonding plug will be formally allowed in the next 2023 National Electrical Code Book. Pretty neat, eh?

What about bonding parallel generators?

Well, that’s really simple, as well. If you have two generators hooked together with a parallel cable kit, you only need to put the Neutral bonding plug in the “Companion” generator (the one with the 30-amp twist-lock plug), and hook up everything else normally.

Then the generator bonding plug will properly “bond” both generators together, and your EMS will see the proper Neutral-Ground bond it’s expecting. So all will be well. In a nutshell, to connect two inverter generators in parallel, you only need one Generator Bonding Plug, typically installed on the Master or Companion generator.

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.
Join Mike’s popular and informative Facebook group.
And you don’t want to miss Mike’s webcasts on his YouTube channel.

For information on how to support RVelectricity and No~Shock~Zone articles, seminars and videos, please click the I Like Mike Campaign

##RVDT1586;##RVT998

Subscribe
Notify of

This site uses Akismet to reduce spam. Learn how your comment data is processed.

2 Comments
Newest
Oldest
Inline Feedbacks
View all comments
Ray
6 days ago

Good article as usual. I have a follow up question. I note that you say in the article “Remember, this has nothing to do with a ground rod in the dirt, which no RV with a built-in or portable generator needs.” I use your bonding plug as it is necessary to get the EMS to allow service. But my portable generator also has a connection for a grounding rod. Am I correct in assuming that because the RV frame acts as the ground, via the bonding plug, the grounding rod is no longer necessary?

Irv
11 days ago

Thanks!