A few weeks ago I started a series of articles on bonding and grounding of portable generators when used with RVs. Those articles stirred up quite a bit of conversation which is a good thing. We still have a couple of subjects to cover in this discussion so let’s get started with checking your generator to determine if it is already bonded. Remember, when we talk about bonding in the context of this subject, we are talking about connecting the neutral of the generator to the ground of the generator. Also remember that this specific bonding is to be done in only one place according to national electrical code.
In order to determine if your generator is already bonded you will need a multimeter which is capable of checking ohms or continuity. Keep in mind that continuity is a specific check of resistance, except the resistance for “continuity” is zero or very low. Next you will have to identify the neutral and the ground contacts on the generator output. Most likely we are talking about a generator that has either 120vac, 20 amp output or 120vac, 30 amp output connectors. The typical 30 amp receptacle has three connections as shown in the photograph of a TT-30R. Looking at this receptacle, the ground connection is at the top and looks like it is round. The two slanted slots at the bottom are the hot and the neutral connections, with the neutral being the slot on the right and the hot being the slot on the left. In order to determine if your generator is bonded properly for use on an RV, you should check for continuity between the neutral connection and the ground connection. If you are using the ohms setting on the multimeter, set the meter to the lowest ohms range and check for zero ohms between the two connections.
If your generator is bonded properly per the above test, there is nothing else you need to do because your generator is bonded.
Next time we will explain how to accomplish the necessary bonding if needed and discuss proper grounding of a portable generator.
Anonymous
My dad wants our family to be prepared in case of an emergency. It was explained here that when considering a generator, it should be bonded for continuity. Furthermore, it’s recommended to consult electricians for quality grounding portable generators.
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Mark R. Owen
I tried to find a way to contact the blog author, directly, but I was unsuccessful. Someone quoted me this blog presuming they should tamper with their portable generator to bond the neutral to the ground. THIS IS A DANGEROUS NOTION ON A FLOATING GROUND SYSTEM!!! This article should be _removed_ and a retraction published.
An RV electrical system should be attached to the grid as a sub-panel. Bonding an RV electrical system and then attaching it to the grid (through a campground electrical distribution system) is a fire hazard and increases the chance of electrocution through the camper frame.
Bonding neutral to earth-ground presumes that there is a low-resistance earth ground available. In an RV situation where you would want to use a generator, THIS IS NEVER GOING TO HAPPEN. Ipso, facto, don’t attempt to bond your generator’s neutral!!!
The generators that RVers are typically using are classified as “backup” generators. Backup generators have a floating neutral because it is anticipated that they are going to be attached to your residence (through the appropriate manual or automatic switch) to your residence’s electrical system that already has an earth ground and bonded neutral. To use a bonded neutral generator in such an application (without a switch that also switches out the neutrals) would be a fire hazard and would likely cause the GFCI devices in the house to trip.
If you want to increase the protection factor when using a generator with an RV, install GFCI devices. Specific circuit devices are more practical than trying to use a main panel-breaker GFCI or a device that is located outside the camper for a ‘blanket’ effect. Heavy motor circuits such as air conditioners, or, 12-volt converters, are bad candidates for being GFCI protected as there are likely to be nuisance trippings. A nuisance tripping on a refrigerator circuit can be costly. Refrigerator circuits should probably only be protected by GFCI devices if an automatic backup power source kicks in when grid or generator power goes off. GFCI devices are not fool-proof but will deal with most of the unique hazards of using a floating-neutral generator with an RV. There is no magic bullet that will turn your RV into a living space that entirely meets residential code. So, DON’T MESS WITH YOUR GENERATOR’s WIRING !!!
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Lamar F
I am new to the RV world and just purchased a 5th wheel 35ft LIGHT by OPEN RANGE and have a question about using a portable generator if i had to stop for the night at a rest stop are someplace. the rv can use 30 or 50 amp service, and my question is if i purchased the Honda 25 amp whisper generator for the back of my truck could i run my 20 amp A/C on that generator and would i need to ground the generator.
Larry Cad
Rob, you state that if your RV is not plugged into shore power, then it is covered by the OSHA directive.
I’m not certain how you arrive at this conclusion, but I would be more inclined to think the generator would be covered by installation requirements for an auxiliary generator for a residence, unless you are doing construction on your RV! 🙂
Second, I do not understand your advice not to plug into shore power and run your generator at the same time. Of course, this would depend on if you have a properly functioning transfer switch, a point you didn’t mention.
Third, I stand by my advice that if you have a generator connected to your RV, the neutral should be bonded to ground in order to provide a proper, and safe path for fault current to flow.
Larry
Rob Fauchon
Further research shows up more when you read the OSSHA regulations regarding generators used on construction sites. If your RV is not plugged into shore power, then it is covered by this directive. Basically :
1.do not plug your RV into shore power and your generator at the same time.
2. Understand the reason for a. Bonding and b. Grounding.
3. Understand the construction of your generator, does it have a center tapped transformer or not? Is the center tap grounded to the frame? Is the neutral bonded to the ground?
4.Floating neutral systems are not bonded to the frame.
5. Ground to Earth is the lightning arrestor system.
Having said that, your little silent Honda will best serve you as a separate system that you don’t have to ground to mother earth. Just pug in your appliance and go.
Rob
Just a thought. What’s the point of bonding, if the generator isn’t grounded to mother earth?
Erich Riesenberg
Hello – Just came across your posts on generators. I am trying hard to figure out if mine is grounded. Have you written that post? Thank you.
larrycad
Kurt, you are correct. I was lazy when I described the hole because I felt my description was accurate enough to discern between the “sorta round hole” versus the slots! Certainly didn’t mean to create confusion. 🙂
Larry
Kurt Hammerschmidt
You mention that the ground is the top round hole. I believe you meant the top with the bottom of the hole rounded and not the completely round hole on that receptacle.