Generator bonding and grounding
In previous posts we have discussed what is meant by “bonding” in an electrical distribution system. This is an important concept. If it seems like I am dwelling on this, I want to make sure we are clear on what bonding means.
The ground wire system and the neutral wire system are two separate wire systems. By code, they are to be connected together at ONE point and only one point. If there is more than one bonding point in the wiring system, you can create ground faults, circulating currents and possibly prevent a breaker from tripping if there is a short circuit. If there is no bond, it is also possible that a breaker will not trip.
The breaker panel in your RV is classified as a sub-panel. As such there is NO bond in the panel and the neutral/ground wiring systems in your RV are NOT connected to each other anywhere in the RV. This is because when you plug in your shore power cord, you become part of the campground electrical system which IS bonded, again, at ONE point in the entire campground, generally at the campground main breaker panel.
If you have a generator that is permanently installed in your RV, such as is typical in Class A motorhomes, the generator has a bond between the neutral and the ground, such that when the transfer switch switches, the isolated neutral and ground systems get connected together.
If, however, you use a portable generator, sitting on the ground or in the back of your pickup truck, a problem occurs. Typically portable generators are made with isolated grounds and neutrals, meaning the ground and the neutral are not bonded in the generator. Since the ground and the neutral are also not bonded in the RV, this creates a code violation and a possible safety hazard which needs to be corrected.
This problem cannot be corrected by driving a ground rod into the dirt, and connecting it to the generator, and it cannot be corrected by connecting the generator case to the motorhome frame. Neither of these procedures connects the neutral to the ground. The only way this can be accomplished is to properly connect the neutral wire to the ground wire with a properly sized and properly connected bond wire installed at the proper location in the electrical system.
When considering solutions to this problem, it is probably not a good idea to consider installing a bonding wire in the breaker panel. Remember, when you unplug the generator and plug into a shore power outlet, the shore power outlet will provide a proper bond and if you have another bond in your breaker panel, you have a new code violation.
The best place to create a neutral/ground bond is at the generator itself.
By doing the bonding at the generator, you preserve the ground/neutral isolation within the RV electrical system. I have been reading instruction manuals for various manufacturers generators and have concluded that they are not too clear on this whole subject. So far I have not seen any of the manuals that even address the subject of neutral/ground bonding. About the only subject that is mentioned is the actual grounding of the generator case which is a whole other subject not connected (no pun intended) to this subject.
Since the manufacturers seem to ignore this subject we are left on our own to solve the problem. If I had a portable generator to be used to power my RV, the first thing I would do, if there was no procedure described in the manual, would be to contact the manufacturer and ask them what they would recommend, and then ask them for the recommendation in writing. Remember we are talking about a potential safety hazard here. The reason I recommend getting it in writing is because we don’t want to have any potential warranty issues.
Of course there is the strong possibility that the manufacturer will not provide a recommended bonding procedure which leaves you on your own to make one up. Assuming you are using the portable generator to power your RV ONLY, and if it were my generator, I would take the case apart and install a permanent jumper between the ground and the neutral wires inside the case. The reason I say this is because if you also plan to use the generator as an emergency power source for your home, the bond wire will need to be removed in order to be in code compliance.
For a 30 amp generator, the bonding wire should be at least a #10 wire. For a 50 amp, 240/120 volt generator, the bonding wire should be at least a #6. I can’t give you specific installation instructions because every generator is different. If you are comfortable doing electrical work, follow the basic suggestions above. If you are not comfortable, I would suggest contacting a generator repair shop to have it done. Keep in mind that this is a subject that creates a great deal of confusion and there is no guarantee that the shop you chose will even understand what you are asking. If they shop you talk to seems confused about your request, search out another shop until you talk with someone who sounds comfortable with your request.
Finally for this post anyway, I would suggest you verify that the modification is done properly. In our next post, we will discuss how you should do this test. Until then,
happy camping,
Larry
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Larry,
I just want to clarify that the whole reason you want to cover this is because of potential safety issues, correct? If that’s the case, consider a scenario where someone has bonded both circuits together in the generator-the way you describe. Now, that person has plugged an appliance into an outlet in the rv, and the appliance is not polarized. Suppose the gen. is outside- maybe sitting in water or in a damp environment. What happens if someone touches it?
Your thoughts?
Drew
Your articles on generators – is there anyway to check that an error has been made in connecting up a generator that a layman can do without taking things apart or hiring an electrical expert? Since improper connections are hazardous we would like to be sure our generator wiring is safe and hope there is a test(s) or observations which would alert us to a problem.
Many thanks.
I tried connecting my Honda 2000 to my 2005 Beaver Coach and the coach would not take power from the portable generator. When I spoke to a rep at Monaco they were somewhat reluctant to discuss the topic for liability reasons, but did tell me that if I knew a qualified elec to make up a short extention cord connecting ( I think ) the common and the ground in the cord, called a floating ground that would resolve the issue. I did have a short cord made up and now everything works very well. I only use the cord when I connect to the coach.
The person that made up the cord stated that the only concern cound be that in very wet conditions while the generator was running and I was standing outside in the rain and touched the coach I may feel a slight tingle. I have tried this and never have felt anything. Your thoughts…….
Here’s the “scoop” on Honda invertors generators, other brands also, and cheap invertors. NIETHER side of the 120AC circuit is “ground”. I covered this in another post. A Honda
EU1000 like I have, and the EU2000 (which NOW sells for less than I paid for my EU1000) has 120 across the 120V AC outlet. From EITHER side to ground is 60 volts. It is imperative no effort be made to ‘ground’ either side of the 120V outlet. Shore power and my klunky Onan have the residential type of wiring where one side is ground. It is absolutely IMPOSSIBLE to hook up a Honda or similar inverter to the “shore power” input of the coach. On my coach, I have two separate 120V AC circuits, one exclusively for the Honda.
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As I said in my previous post, I knew this condition existed and attempted to run my refrigerator on the Honda. I carefully made sure the 120V circuit in the refrigerator was not grounded to the coach on either side of the 120V input. WRONG MOVE! I forgot about the 12V DC circuit in the refrigerator and essentially put 60V AC into the 12V refer circuit. Holy smokin’ refer, Batman! Extensive damage to the electronics and wiring which I was able to repair. Norcold will not / did not disclose / didn’t know the value of any of the resistors, some of which went supernova. The wiring between the two circuit boards was total toast. After much experimentation, I FINALLY was able to get everything up and running again. Actually more luck than skill. The resistors I replaced are now on the outside of the electronics box (think rat’s nest of wiring) as there wasn’t room to put them back on the board.
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I have two sets of 120V outlets: [1] Coach and [2] Honda. I love the Honda, as it’s so quiet even the tent campers don’t usually complain. My Onan? Hah!
If you are going to use the generator for something other than just power for your RV I think that the short cord that Lorne had made up sounds like the right way to go. You probably have to have some adapter to connect the RV cord to the generator plugs anyhow. Make the short cord your “adapter” as well as your bond. That way you will never forget to use it when you use the generator with your RV and you never use it by mistake when you connect the generator to your house wiring.
JUST A THOUGHT—-EVERY COACH WITH AN INSTALLED GENERATOR RUNNING AND PROPERLY BONDED TO “GROUND”, IS NOT NECESSARILY AT GROUND POTENTIAL BECAUSE THERE IS NO CONNECTION TO EARTH GROUND. THEORETICALLY THE COACH GROUND CAN BE AT A HIGH POTENTIAL TO EARTH AND ANYONE STANDING THEREON. IN A DRY CLIMATE YOU CAN ACTUALLY MEASURE THIS IF THE GROUND IS DAMP. THIS POTENTIAL HAS A STATIC COMPONENT AS WELL AS THE GENERATED PART AND IS PROBABLY NOT ENOUGH TO ELECTRACUTE, BUT STILL….
LARRY D
With regard to neutral/ground bonding, Lorne and Bill have the right idea. You can use a short adaptor cord with the neutral connected to the ground in the cord plug. This allows you to use the generator for emergency power for a house and still use the generator for power for your RV. Good suggestion.
Larry
Drew, your scenario is complex. First of all, bonding of neutral to ground has little or nothing to do with your scenario. Consider this: all currently produced electrical devices fall into two or three categories: first you have the kind with three prong plugs which cannot be plugged in the wrong way. With this kind of plug, there is no way that a properly wired outlet can cause you to get shocked. Second you have the devices that have a cord with a polarized plug. This is the plug that has one blade wider than the other. This type of plug also forces you to insert the plug so that the device is properly connected. Lastly we have devices which are double insulated, which prevents you from getting shocked if the plug is inserted the wrong way. All three of these scenarios will prevent electrical shocks when using a properly wired outlet. I define a properly wired outlet as one which is connected to a properly bonded power system.
Larry
Darth, I am very surprised by your comments about the Honda generator. The voltages you describe are very typical of a system that has a floating neutral, meaning the neutral is not bonded to the ground. As I have discussed in my posts, this is pretty much standard proceedure in the generator manufacturing business. However, in a standard house wiring system the ground IS bonded to the neutral. So, when you hook up a Honda generator to a house, by default, you connect the neutral to the ground. I can guarantee that this will work. Yet, you are telling me, in essence, that it doesn’t work and I wonder what I am missing.
Larry
Wayne, there are several checks you can make on your generator and your shore power system to determine if it is connected properly. You will need a multimeter of course. I will be explaining those checks in a future post.
Larry
Just for the record the patch cord we made up is only used on the coach. I was concerned about possibly damaging my fridge but have had no problems. I always start the Honda and let in run for a couple of mins before connecting to the coach. We switch the fridge to LP and shut down the battery charger before connecting as well. That leaves plenty of power from the Honda to run the TV’s , Sat , and microwave for short periods. I have run my Honda on the coach for around 350 hours now that we made the patch cord up with no issues…… Before the patch cord the coach would not take any power from the Honda…..
Thanks Lorne
Lorne, just to clarify, you are running a Honda 2000, with a patch cord that bonds the neutral to the ground on the generator and you are running it successfully. Is that correct? I would have predicted that it would be successful and would be surprised if it were not.
Larry
Hey Larry
Yes that is the case. I had a short extension cord made and they crossed two terminals with a small copper jumper at one end of the extension cord only. I can now run power to my 2005 Beaver Coach from the Honda 2000 and everything works just fine. Monaco were the folks that told me how this was done but they would not make the cord up for me but instead advised me to have a qualified elec make one up……… Lorne
I personally don’t think too much about grounding. I prefer to use the generator ungrounded. If the power has no potential to the ground and you contact on of the wires you don’t recieve a shock. the only way would be between both wires(the lineoff the generator) because of no ground no shock. We used 480 volt 3 phase power ungrounded in a quarry I worked at and never had an incident.. It wasn’t until MSHA( the mining branch of OSHA) made the owner ground everything that we started having problems. I’ve seen the bushing on a transformer burn up and without the centertap seen voltages go wild and all the ground rods in the world wouldn’t have made a differance. NO Potential to gound.
Lorne/Larry: so do I have this right:
the female end of the short patch cord is wired normally to receive the cord from the coach. The other male end of the patch cord has the white neutral wire cross-connected to the ground lug (green), thus creating a neutral-ground bond near/at the generator.
Dave, that is exactly correct. What you described will accomplish the necessary and required ground to neutral bonding.
Larry
Thomas, there are so many incorrect statements and so much mis-information in your comment that I considered deleting it. Instead, I am going to leave it up as an example of the kind of post that creates confusion on forums and blogs. For qualifications, I am an electrical engineer, a licensed electrical contractor, and I have an MSHA safety training certificate. I work in several mines and perform the MSHA required ground testing for my customers. I know why this test is performed and I also know why the required grounding is proper and produces safer working conditions. None of the conditions your describe were caused by proper grounding, period.
Finally, while I appreciate your opinion, my posts have NOT been discussing grounding. My posts have been discussing BONDING!! A totally different subject.
Larry.
RV LAD, I have read over your comment and I have a question. You state, “THEORETICALLY THE COACH GROUND CAN BE AT A HIGH POTENTIAL TO EARTH”. Can you please explain how this can happen? I have thought about it and I can’t come up with an explanation on how it would happen and I am curious what you were thinking of when you wrote it. I’m sure others on here are also interested.
Thanks,
Larry
Ok, try this! I have 2 Honda 2000 i generators and I am using 2 short extension cords (12ga, 3 prong plug) connected into a standard 30A rv receptical. Now before everyone gets all excited about shock hazard, I never unplug either of the cords while a generator is running.
Question is: Will bonding at the receptical have any negative effects on the generators syncing up with each other or is there any other ramification to bonding this way?
Ok stupid me. RECEPTACLE is how I was supposed to spell RECEPTACLE.
No, I will not tell you what school I went to!
Al, I am not an expert on Honda generators, but I suspect that you could bond them as we described and be ok. I would check with Honda to verify that it is ok. I assume you have them sync’d properly.
BTW, don’t be so hard on yourself and what school did you go to?
Larry
Larry, as I understand your post and these follow up comments, I can attach my Honda 2000 to my RV but first I should connect the ground and the neutral in the cord running from the Honda to the RV. I have a system where I have isolated the Air Conditioner in the RV with an IOTA ITS-30R Transfer Switch leading to a separate outlet for the generator to plug into. If I just modify the cord it sounds like it should work. Is there any testing with a multimeter that would confirm this before I power it up? Thanks John
John, your understanding is correct. To verify your connection, I will assume your cord ends in a standard 15 or 20 amp plug. I understand that this is the plug you use to power your A/C on the RV. If all that is correct, you will need a multimeter to make the checks you want. First, notice on the end plug that there are three “holes”, two slots and a “round” hole. One of the two slots is taller than the other. That would be the slot on the left as you look at the plug receptacle. The taller slot is the neutral and the shorter slot is the hot. The round hole is the ground. With your multimeter set to read ohms or continuity, and with the cord unplugged from the generator, you should read continuity between the ground and the neutral. You should also read infinity between the hot and the neutral. Next, plug the cord into the generator and fire it up. With the multimeter in the AC volts setting, and set to read at least 130 volts AC, check the voltage from hot to neutral and read about 120vac. Then check from hot to ground and read the same voltage. Now read from neutral to ground and you should have 0 vac. If these checks are ok, you should be safe to plug in your A/C. Any questions, please let me know.
Larry
Larry-thanks for the reply! Got out of HS in 1953 so I guess some stuff just goes away.
I am an OLD electronics tech-computers-not a power guy and thanks again.
Larry,
Maybe my response sounds complex- but it’s not. If everything is bonded the way you describe, and someone plugs an older non-polarized device into an outlet, you will get shocked if you come in contact with the ground circuit. Depending on the appliance, this could also happen if the neutral blade was trimmed to make it fit into an older outlet/extention cord, etc. My point is– If you make your rv/gen combo work like your house wiring, these scenarios are possible. I prefer to simply use my Progressive surge protector/circuit analyzer, and keep everything maintained. (Really, I also see very few if any stand alone generators in use these days to power rv’s)
This is a great forum, and it really makes you think about the responses.
Drew
Drew, I disagree with your premise. If your electrical system is properly bonded and grounded, and then you plug in a non-polarized device the wrong way, it is possible to get a shock from the device. However, if you have a non-bonded system, and you do the same thing, you will still get a shock! It is not the bonding that gets you shocked, it is plugging in a non-polarized device the wrong way that is dangerous.
You seem to believe that plugging in a non-polarized device can somehow energize the ground system and I disagree with that statement.
However, this is still a free country and you are free to do whatever you want with your system. Just remember, if it is wired incorrectly, regardless of how well you maintain it, it is a dangerous system that can shock someone, and there is much less chance of an electrical shock in a properly wired system.
Larry
thanks for sharing, i loved your post and its very useful, im glad i run to it..
Glad you enjoyed it and glad it helped.
Larry,
I was researching a similar topic (non-RV related) and ran into this forum. I haven’t been able to find a solution for my issue so perhaps you can give me some advice.
I have a small off grid cabin currently being powered by a photovoltaic system. Even though I do have a small AC load center, I am not making the neutral to ground bond in it. This is because my inverter has its neutral bonded to ground internally and I chose to use this as my bonding point. So far so good…
Now I just decided to incorporate a small Honda EU2000i generator into the system as a backup or to use when I need to power bigger loads (my inverter is just 700 watts). I am planning on using an IOTA auto transfer switch to handle the switching between inverter and generator.
My problem is that unlike my inverter, the generator does not have an internal neutral to ground bond. I understand I need to figure out a way to make this bond somewhere else besides the AC load center since this is also used when the inverter is operating.
Will the use of a custom made cord like the one being mention on this post work for my set up? I guess I will have to enter the transfer switch with the already bonded cord so I can use the rest of the system like it is already.
Does this make sense?
Can you think of a better way to do it?
I would appreciate any suggestions.
Thanks.
Ernesto, what you describe is what I would suggest. If you bond the generator on the generator input side of the transfer switch, you can continue to use the neutral/ground bond in your inverter. The important point is that there is to be ONE and only one bond in the entire electrical system and it is to be as close as possible to the source overcurrent protection device, such as a circuit breaker or fuse.
Thanks Larry.
Your response brings up another question:
I currently have a grounding rod buried and wired to my inverter’s chassis. Do I need to have a separate grounding rod for the generator wired to its chassis? or will the inverter ground connection work for the generator circuit even if the inverter is switched out by the transfer switch?
Now that I think about it, since both ground wires (inverter and generator) are bonded at the transfer switch, the ground rod for the inverter will work also for the generator, right?
Thank you very much!
I still don’t understand the point of bonding unless the Generator is actually grounded to mother earth in some way. Please enlighten me.