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Electrical Engineer Explains - Generator Neutral-Ground Bonding
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- Опубліковано 18 лют 2022
- What to do when you want to connect your generator to your home panel through a back-fed circuit breaker. Discussion on neutral-ground bonding with diagrams and details of neutral current and fault current paths.
Fellow EE here, and let me say thank you for not only helping fix my issue, but for utilizing an approach that is outside of the box, not just one that copies a code book diagram.
Thanks. I spent a lot of time thinking about even sharing the concept. It works, technically, but it does feel weird. I'm finalizing the prep for a video on making the generator separately derived at will.
Well thought out and nice drawings from an engineer's perspective. Here is the perspective from a master electrician: You cannot utilize a generator with a bonded neutral unless you switch the neutral along with the power source, due to the objectionable current on the EGC (a generator is not a separately-derived system if the neutral is shared between the sources). It is a code violation to disconnect the EGC as shown, which results in the neutral providing the grounding path. Also, as a licensed electrician I cannot modify a listed generator to remove the bonded neutral as this defeats the listing. A 15 kW or 17.5 kW portable generator should be un-bonded so could be used with the type of panel-interlock switch shown. Another option would to install a Generac 30- or 50-amp HomeLink manual transfer switch, which properly switches the grounded conductor (neutral) along with the ungrounded conductors. This way a bonded-neutral generator can be used.
I certainly appreciate your input. Let me explain a bit more as this situation is not ideal, but sadly, very common. The primary question is which is worse: a lifted EGC on the gen side or two bonded neutrals when a panel backfeed is done. For this scenario, I prefer to lift N-G bond in the portable generator but wouldn't recommend that to a consumer for fear they would forget to reconnect when used in stand-alone mode.
I prefer multi-pole switches for individual branch loads, switches that break neutral connection as well as the hot conductor. The downside is the forced selection of which loads the owner wants on the genset and not the flexibility of any load in the home. In my previous video on the topic, I highlight the meter-socket transfer switch that safely lifts phase and neutral for the ideal scenario. I don't like that the EGC is lifted at the gen receptacle, but the portion that isn't bonded to the service panel is associated with conductors that are only energized when the portable generator is in use, which is why I show the receptacle enclosure bonded to the generator side and not the service panel side.
The ground (EGC) path is intended to be a path back to the neutral, and was added (in Code and practice) to protect from metal casings from being energized. The neutral is the primary return path to the source and the ground is the alternate/abnormal return path. I had to work through the diagrams to determine if the intent of Code was being satisfied - that a return path to the source to trip the overcurrent protection device exists for both scenarios: overcurrent and abnormal fault at any location. While it certainly seems weird that the neutral would be a path back to the source at the service panel N-G bond, electrically, it's identical to having the path back to the neutral at the generator N-G bond. Fault current on the EGC is always trying to get back to the neutral.
Thoughts?
@@richardvedvik979 Well thought out and I can see how this setup would indeed allow a ground-fault path to the source. As an electrician I cannot get past the code violation by lifting the EGC. However, that being said in my world the Authority Having Jurisdiction would have the authority to sign off on your setup, which would relieve me (as a contractor) of responsibility. As to whether an AHJ would agree to the code violation is up to debate. Reference NEC 250.142
@@bretgreen5314 Thanks for providing a reference. I looked at that section (and others in Art. 250) but I'll go back through the last 7 code cycles of handbooks to check for any additional commentary. I recall my focusing on the idea of running an EGC with supply side conductors, which is why the box is bonded from the generator side, but I think you're referring to the portion of time in which the grounded conductor is acting like a portion of the EGC for circuits in the home.
I’m
Thanks for this detailed well thought out explanation. I am in the process of planning a back fed panel and portable generator. While I have a background in electronics that causes me to think way too much about neutral bonding. I did not like the thought of unbonding at the generator. Now I will wonder about a difference in potential between two ground rods. I appreciate your efforts to clear up my thinking.
I just bought the same exact generator and was contemplating removing the new neutral bond from the genset but adding the ground rod outside and breaking the genset ground at the receptacle sounds like a much better proposition. It would allow portable generator use without restoring the neutral bond. Thank you sir!
I do have a plan to add a toggle switch that lets me switch the genset between bonded and floating neutral. I was waiting for the warranty to run out before publishing. :)
Thank you. I"ve spent countless hours trying to figure out how to go about this without removing the neutral in my generator. As you're aware, no one wants to talk about this method, they'd rather you go to a transfer switch that switches the neutral.
Thanks, it certainly is a topic that no one wants to address.
Fellow EE here. Thoughtful and very detailed thanks! People have asked about connecting an F150 Lightning, and there are also many like me with an F150 PowerBoost (hybrid) with a 7.2kw (4pin 30A connector) that have the same or similar question.
I'm planning a video specifically on bi-directional chargers and the challenges associated with them. Same concept applies to your application.
Great video, thanks! Also a EE here. I am dealing with this exact scenario to power the house from a F-150 Lightning. Instead of lifting the ground at the connection box from inside the house, it might solve the problem if we lift the ground from the generator. In case of any ground fault at any appliances in the house or the connection box itself, the neutral to ground bonding at the main panel will route the fault current through generator neutral. What do you guys think?
The problem with lifting the ground at the receptacle is what happens when the neutral is lifted? Then all the neutral current returns to the generator through the earth. The ground rods at the panel and at the generator are not isolated, they are just a big resistor. With an unbalanced load and a lifted neutral, the worms will get buzzed.
I saw a UA-cam where a guy learned that the generator neutral should not be grounded. He ungrounded it, and it started a fire in his house, and he had to call the fire department. For years, the neutral was lifted in his cable. It worked because the ground wire carried the current. Then when he disconnected the neutral from the ground, he had 80 volts on one phase, and 160 volts on the other. The surge protectors in his house melted and filled the house full of smoke. There wasn't much damage, just a lot of smoke.
So, what I did was disconnect the ground in the generator, like you showed. Then I made a 230V plug with the neutral connected to ground, and no cord, painted green, with a note attached, and I keep it in the safe. When I use the generator stand-alone in the woods, I just plug the plug into the socket and I am bonded again. Maybe there's a reason I shouldn't do that. But it's a whole lot easier than opening the generator and rewiring it.
I love your disclaimer. I agree with checking with your local authority.
I find it's best to just build a relationship with the local inspector, they are usually happy to work with people and appreciate honesty and an up-front approach.
I see this is old but as a 30yr electrical contractor I have to agree with you110% on this. In my mind I always said to myself why can't I just use the geny bond and bond everything metal between the geny and the geny outlet plug exactly as you did. To simple. Everything is then protected and to NEC legal on both ends (for most part). No potential for electrical faults on either side. My math works the same as yours. Problem solved. The other way recommend is by illiminating the bond jumper in the geny and now making it a floating neutral but this has consequences (ie) a customer then takes the said geny camping and electrocutes himself because he forgets to re-bond his or her geny. My own home and many more are connected like this and everything works perfect to include all GFI breakers- Gfi plugs in house and all GFIs on the geny side. Glad I found this gave me some relief coming from an electrcial engineer.
Thanks! I appreciate the comments.
Thank you so much for this video! I am a registered professional civil engineer, so I understand your reluctance to give too much "advice!" I have ordered a similar wattage generator which I was planning to backfeed like you have shown, but my problem is that I have two 200 amp panels for a single 400 amp feed. I have ordered and was planning to put generator interlocks on each panel with a 50 amp breaker for the generator feed. I had assumed I could just do a single feed from the generator plug into a junction box in the house with 6/3 wire and then just splice and Y the Black, Red and White wires to each panel. I had not thought about the neutral being connected still back through the service feed. I have searched and searched for an explanation on how to deal with this and I have found a lot of people asking the question, but no one answers it. I would love to see your analysis on this situation and if just doing a separate ground for the generator would take care of this also?
Can you share the generator you have chosen?
@@richardvedvik979 Sure, a refurbished Firman T07571 Tri Fuel. It will run most things in my house except for the Heat Pump...it is a 5 ton and no way it could start it up. Just want to be able to keep Refrigerators and Freezers going and have lights where I need them and the option to turn on and off what I want. I have a 3100 watt WEN Inverter that I bought about 4 years ago to use with my small 5th wheel. I had problems with it because the RV's Electrical Management System would not let it through to the RV because it would say it was ungrounded. I ended up having to make a plug where I connected the neutral to the ground in it to trick the EMS. I didn't know if something like that would work here. I think that would be similar to disconnecting the neutral / ground bond?
@@maccve Sorry for the delay, been a busy couple of weeks. If you have two 200A panels, do you share a 400A service or just have a single 200A service with the panels wired in parallel (or feed-thru for the second panel)?
If panel 1 is permanently connected to panel 2, you don't want to "Y" the feed from the generator because the conductor lengths won't be equal and thus the power won't be synchronized. If the connection between Panel 1 and Panel 2 is operable, it would have to be interlocked with the generator breakers AND the main. Unlikely that is doable with residential products.
If you have a single meter, the meter transfer switch plug that I feature in my first Gen connection video would be ideal. If you have two meters and the two panels are actually isolated, then you could use two meter transfer switches, one 30A and one 50A and utilize the two receptacles on your generator.
Amazingly good presentation on a topic not mentioned much elsewhere......and if it was shown elsewhere.....not as clear as this one here !!!......SUPER !!!!
YES....the bonding question is very vague and not very good elsewhere.....
Thanks! My next video will be explaining how to add a toggle switch for a selectable bond.
@@richardvedvik979 👍
Excellent video. It's a lot to take in all at once and thank you for sharing.
Thank you, I understand it's intense and a larger screen (32" or bigger) is preferred for viewing, while pausing the video to spend the time needed to trace out what i'm describing. I kept it moving quickly to prevent it from being too long, despite being fairly dense.
Came up with same exact answer yesterday after some thought retired building engineer
Thanks for trying. This video was made by an engineer for engineers. Need to highlight or point to changes from slide to slide. I'm in IT and I very often talk too techy for my users. Especially my wife!
Yea, it's a very technical topic. This was a more in-depth follow-up to another video of mine that stayed high-level on types of generators. And this went very in-depth to explain neutral-ground bonding and show the steps I took to analyze a solution to a common problem. It went deep intentionally. Maybe a "nerd alert" warning would have been helpful!
Right. Would be nice to highlight exactly what part or circuit is being referenced in each diagram.
@@motorvaderlapstrake7238 thanks for the feedback, I do highlight each path. However, I do understand that it's difficult to see. I'll try a different method in the future, I have ideas for other ways to show wiring colors
@@richardvedvik979 Thanks, and we do appreciate the info and the effort!
Great video. I did the same set up. After watching this I may need to consider changing the ground at the generator receptacle. I don’t have a junction box between the outdoor receptacle and the breaker in the box.
Thanks for the comment. The video is intended to step though the process to allow you to evaluate your own installation and consider each of the pathways I explain. I had to draw it out to "see" it, which helped greatly in understanding what the best course of action was.
Richard, I really appreciate the time you put into this video. Very informative! I have a question on a boat installation I'm doing. The boat is quite large and has two 3 phase generators onboard. Both generators are designed in the system to work simultaneously at sea to power loads specified by the captain. To prevent backfeeding of the two generator sources is achieved by using contactors for each load section in the main panel with a mechanical and electrical interlock. Neutrals from both generators are connected together in the main panel (isolated from the metal enclosure) and the grounding conductors from each generator are bonded together and to the main panel enclosure. In this case I believe I am correct by bonding the grounding and neutral conductor ONCE only at the primary generator for the entire system and not bonding N-G at the second generator. I still have my N-G bond at generator 1 so always have a path for fault current keeping in line with the NEC guidance of bonding N-G once and only once in any non-seperately derived electrical system. I would appreciate your thoughts.
Hi, Chris. That sounds like an awesome project. I'd love to see a one-line diagram to verify my thoughts. Any chance you could message me on LinkedIn so we can chat offline? www.linkedin.com/in/richard-vedvik-308a6218/
Hey Richard - Thank you so much for this content. I have been searching far and wide solutions to connecting two sources to a load but without utilizing a relay or some switch for the ground.. As in your solution @ 12:58 - The issue in my mind is like this - Lets say you have the generator running and supplying right, The utility is switched off via the transfer switch. However the neutral wire is still going to the utility.. This means that when the utility comes back on while you have the generator running and supplying load to the Home - you essentially are connecting two neutral wires of two different power sources together.. Each of these power sources have their own potential on the N wire.. Logically it seems wrong that one would have two different power sources connecting their neutral wires together.. I saw an exact same connection you are describing here.. Even if you were to take a neutral transfer switch - you would then have to bond @ both sources - you would still have both source's N wire connected only now they would be connected via the earth wire. The following link is the exact connection you describe only that its animated which might be easier to view than a circuit diagram. Thank you again - any help will greatly be appreicated. ua-cam.com/video/kXGs3QLF_sg/v-deo.html
I haven't ignored your message, but wanted to put time into the response. I'll reply in detail later this week.
Whale, from a layman's perspective, I got lost in the weeds. Mostly because it was difficult to unpack the flow represented in the diagrams without an electrical background, or a cursor to follow. Diagrams changed before I could mentally trace-out what you were describing.
Something so "alien" and complicated that a dozen or so schematics are required to parse it out, needs to have some form of "pointer" employed in order to reap the benefits of your presentation. Not all of us watching are er electrical engineers with the skill to read schematics............at a glance, anyway. 😊
Fair point. I expect people to need to pause the video to catch up with what I'm saying as I prefer to keep videos moving along. It is a high-level conversation, for sure. But the high-level is intentional because this topic is somewhat controversial and if I didn't go into the weeds, I would be blasted with a lot of negative comments from folks that hadn't done the match or in-depth study. It really did take me a lot of time to decide to even publish this video. The cliff notes are that only one neutral-ground bond can exist in the entire electrical system. That applies to sub-panels and connected generators. Each system is unique, and my goal is to provide the tools for self-analysis.
I have a main disconnect panel outside by the meter where neutral and ground are bonded.
I have another panel inside my garage with all my breakers where neutral busbar and ground busbar are separated (not bonded).
Is it okay to connect generator’s neural and ground wires to the corresponding busbars in the inside panel? I am assuming that even though they are not bonded in the inside panel, the fact that they are bonded at the main disconnect is sufficient? FYI, my generator has floating neutral. Thanks
With a floating neutral, you could utilize the bond in the main disconnect, sure. The issue will come with mechanically interlocking the generator breaker and the main breaker. We do this with key interlocks when the breakers are remote.
As a retired Sr. Design Engineer with 35 years of experience, I have designed numerous electrical systems (mostly commercial or industrial) with generators ranging from 10KW up to (90) 2750kW in one building. I too am a PE. I agree with 99% of your video. Here are the parts that are concerning. The purpose of grounding electrodes (ground rods included) are not for reference but for the dissipation of surges caused by lightning. Confirmed personally with Mike Holt. The second thing is your resolve of lifting the equipment ground in the box. Does it do what you contend? Yes. Is it as required by NEC? No. You correctly showed and stated that with a non separately derived system, you remove the neutral ground bond in the generator. How do you know if the generator is a separately derived system? If the neutral is broken and transferred to the generator along with the ungrounded conductors, that is separately derived. If it remains connected to utility, then non separately derived. The connection of the neutral to ground bond in a generator does not change based on generator size. So, the bond should be removed, and the equipment ground at the box connected, in my opinion. Respectfully, Kevin
Thank you for the comments. I agree that lifting the N-G bond at the generator is the correct solution, which I do mention. But then, the portable generator cannot be used stand-alone. When weighing risks to the general public, my concern was most people would not modify the N-G bond properly, nor would they want to render their portable generator inoperable unless connected to the home.
My video is not intended for permanently installed generators, which should with have a switched neutral transfer switch or a lifted N-G bond.
A neighbor down the street had a generac system installed and there was a mistake made which resulted in damaged appliances and wiring. I think he said it had to do with grounding and or neutral wiring. As I am getting ready to hook up my portable generator I want to make sure that don't happen. Any ideas what that could have been the mistake? thanks
It is hard to say what happened to that installation without seeing the actual wiring, but what I describe in this video is usually neglected in residential installations. Most of the permanently installed Generac systems have a transfer switch and most electricans get the neutral bonding correct (i.e. lift the bond in the generator if they have a 2-pole switch and keep the bond in the generator if they have a 3-pole switch). Sadly, accidents happen and what we are discussing is really an advanced topic.
A portable generator needs to take this video into consideration. Ideally, it does not lift the ground at the receptacle but instead lifts the neutral-ground bond at the generator. I will post a video on that shortly.
Awesome explanation...thanks
I have a 20 year old portable generator that has served me well and still runs.
I am considering an open frame inverter generator because several of my new appliances are wifi enabled.
The generator you bought is less less expensive than the unit I am considering. Generac claims it is safe for sensitive electronics.
Is the inverter generator worth the extra money?
I would argue that the method at 7:50 isn't solving anything, and in some ways presents an extra hazard. Since you still have the neutral and ground bonded at the generator, any voltage drop that occurs across the neutral wire as a result of load current will now be on the frame of the generator as referenced to the earth. This is the actual danger of the "problem" with the parallel paths issue that was the premise for breaking the ground connection in the first place. In addition, this voltage drop has now been doubled due to not having parallel neutral current paths.
In addition, consider the situation that there is an open circuit on the neutral going back to the generator, and there is an unbalanced load in the home. Now, one of the legs in the panel will shoot to 240V, and the other that had load on it down to about zero. Since the center tap of the generator is bonded to the frame of the generator and the inlet, you now have up to 120V to ground on the generator frame and inlet, which is a hazard. Not to mention that half the stuff in your house that was on the lightly loaded leg is now fried after being exposed to 240V. If the parallel paths had been allowed to remain, this open neutral condition wouldn't have done anything unless the ground also opened up. Your method allows a single bad connection or open neutral wire to create dangerous touch voltages and damage loads in the home. What are your thoughts on this take?
Thank you for the detailed comment, I appreciate the presented scenarios.
Your first part discusses trading voltage drop for ~30 feet of adequately-sized neutral conductor length for intentional current on bonded and grounded metal surfaces at all times. I would counter that the safety concern of two neutral-ground bonds (prohibited by NEC) is worse than the voltage drop on the neutral (since your thought experiment is if it's better to have the ground be a second neutral current path). Using the ground as a redundant neutral, intentionally, would mean we have shock potential at all metal surfaces between (and including) the panel and the generator frame. Even touching the receptacle enclosure would expose you to shock potential since current is intentionally present (and given low impedance bonding, normal neutral current would be split evenly between neutral conductors and grounded metal surfaces).
To your point, we know that all homes are unbalanced and thus all homes have current on the neutral, back to source. An open neutral is bad, regardless of where it occurs, but it's also uncommon and unintentional, whereas using equipment grounding conductors (EGC) as redundant neutral current pathways is an alternative that guarantees an unsafe (and illegal) situation. I'm aware of the implications of what I propose, hence my disclaimer, but it's not a topic that's openly discussed despite being very common.
What I propose is not an ideal solution, but a "lesser of two evils". Certainly, the preferred solution is a floating neutral at the generator and then the generator grounding conductor is bonded to the home's grounding bar, using the home's ground rod as well. And for those with bonded neutral generators, a multi-pole transfer switch is preferred, which I do mention.
Thoughts?
@@richardvedvik979 Hmm, I would agree that while breaking the path on the EGC does prevent the objectionable current on that conductor, it does not reduce any shock hazard. I would argue that a shock hazard exists wherever there is a voltage difference between two points that could be touched, and not inherently because of current on the EGC. The current on the EGC is the symptom of the main problem, which is the neutral-ground bonds in two places. By removing that current path through the EGC, it does not reduce any shock hazard, and actually increases it. Can you give an example of how current on the EGC actually creates a shock hazard that can is fixed by breaking the path? It seems to me that since the neutral ground bond is in two locations, there is no longer a functionally separate EGC and neutral. The neutral becomes a shared EGC/neutral, and by breaking one of the paths it just reduces the number of failures that need to happen before dangerous touch voltages appear. It becomes a question of whether you want a single shared neutral/EGC or redundant ones in parallel. To me it seems the redundant ones in parallel is the lesser of two evils. The real solution is to undo the bond at the generator as you say.
Just found your channel!! Awesome!!.. Can you do a vid( if you havent already) on off grid feeding a cabin w a generator... There seems to be a dif of opinion on grounding rod w generator if its already bonded.. Love the channel sir..
Thank you! You have an interesting idea. It's unique and specific, but something I can tackle. I also need to do videos on off-grid solar or other off-grid renewable energy sources. I like your concept and have added it to the list.
Will disconnecting the ground at the generator's 30 amp receptacle safely eliminate the dual fault current path and allow the 120 volt generator outlets to remain safe for use in the field?
Do not disconnect at the generator receptacle as that ground path is required for safety. What I discuss in this video is to not modify the generator. Disconnecting the ground coming from the home panel, at the receptacle tied to the home panel, is what allows for a fault path back to the generator. Because the breaker feeding the generator receptacle must be mechanically interlocked with the main breaker, it is not possible to energize this receptacle from the panel. But a ground fault path is required back to the generator (source).
Great video. One question if I may. I have a generlink connection into my meter if familiar with those. My generator is bonded. I can’t lift the ground as it’s connected to the meter through a proprietary cable that connects to the meter. Could I make a short cord and not connect the ground prong to the ground of the generator or something like that inline? It’s an inverter generator and I haven’t found out yet where I can unbond and I would rather not if I am able to make it safe when stand alone. Any advice would be appreciated.
Sorry for the delay. I have a more recent video where I show how I modified my generator to be able to lift the neutral-ground bond, allowing the generator to switch between bonded and floating. I have a simple toggle switch that lets me choose.
Do you like the Generlink? I mention that solution in another video. I would be concerned with modifying the cord since we do want the meter casing bonded to the source - so you really don't want to lift the ground in the Generlink. However, does the Generlink switch the neutral? If so, then you have no concern.
This Generac generator has neutral bonded to ground. I have a Honda generator and like most Honda generators neutral is not bonded to ground so in my case I would connect to the house panel with the standard connections including the ground wire.
Hi Richard. My generators, neutral, and ground are bonded . I'm using a 3 wire 50 amp cord connecting to an L-14 outlet Ieaving the ground prong unused. My planning is to use two wires for hot's and one for neutral for a 240-volt circuit. Should I run a ground from the generator to the receptacle outlet box only. Recommendations, only of course. Thanks Terry
At first, it seems like your situation is as I describe in my video and that I would recommend running a ground from the generator and lifting the ground from the panel. Let's assume the generator receptacle casing is energized by the generator (which is the only way it should be energized), in this case, fault current (hot to metal enclosure) will flow on an EGC (ground) to the panel, across that bonding jumper, onto the neutral, then back to the generator. It is a longer path, but it is a path. You're good, as is, by my estimation.
Richard had question about my generator. In the owner manual it says the neutral is bonded to frame. I am using a transfer switch that switches individual branch circuits. So either the brach power wire is supplied either by generator or by utility. The neutral and grounds are not switched. Only the power wire is switched. I am using a pvc inlet box and pvc conduit to my transfer switch panel. So if I understand you. To elininate the ground loop I would need to disconnect the ground comming from my generator either at the inlet box or some where before my service panel. I have a 6/3 with ground comming from inlet box to my transfer switch panel. The neutral from that 6/3 passes through to the neutral/ ground bar in my service panel. The ground from the 6/3 passes through to the neutral/ground bar in service panel.
Thanks for the comment. In your setup, you have two neutral-ground bonds with the generator connected. The ideal solution is to break the neutral-ground bond in the generator and leave the wiring as-is. But if you do this, you won't be able to use the generator in a stand-alone mode. The other solution is as I show in this video and that would be breaking the ground connection at the connection between generator and building.
Hi Richard- I have the 7.4KW F-150 and tried to connect to the house and I have this problem. The F150 Gen gets tripped. I think that this solution would be perfect by taking the ground rod from the generator receptacle to the ground. I am not sure why you have the rod by the generator instead of having it by the receptacle, but I would love to have your feedback on this. Thanks!
Sorry for the delay, been a busy month. I show the ground rod at the generator but it certainly could be at the receptacle! Thanks!
Richard wonderful channel! 2Q? I have a Duromax XP12000DX which I connect to an inlet box that goes to my sub panel in the garage when needed. Inlet connects to a two pole 50 amp breaker, and neutral to neutral bar. Ground bar separated. When in use main switch turned off in main panel/house and sub panel breaker turned on. The inlet box is ground at the sub panel. Q1 do I have a stable connection? Is there any back feed to the street via the neutral connection from the main panel that should be concern about?
Thanks! I understand why you did what you did. What size is the garage feed breaker in the home? There is a risk of accidentally paralleling the utility and generator with your configuration. I understand you know to turn main off first, but the possibility is a concern. No worry about the neutral back-feeding. Your generator should have the neutral -ground bond open.
Good video Richard. I have a question about using a Ford lightning to back up my residence with a 200 amp service. They make a home integration system which is automatic and fairly expensive. My electrical service has been pretty reliable but if I have the truck I would like to be able power essential circuits if there should be a longer term outage and am willing to do it manually exactly as you had described. Can I use an interlock system as you described or would it be better to use a power transfer switch? To make it more complicated is I also have solar panels with micro inverters. Is there a way to do this manually and use the truck to activate the solar panels as well as recharge the truck simultaneously? My understanding is the truck is a bonded neutral system. I realize this makes me sound like I’m preparing for Armageddon but hey, you never know. I’ve not been able to find out if the automatic system by Ford will integrate with solar from a third party solar company. Any advice is appreciated.
Sorry for the delay, this is a more complicated question. If you use a mechanical interlock from the truck's onboard inverter, you may be able to activate the solar panel micro inverters. That will depend on what the output of the inverter actually looks like (in a voltage vs time format) and how many harmonics are in the output. The decision to backfeed or use a transfer switch depends on the output rating of the inverter system. If it's 30A or smaller, a transfer switch may be overkill. If it's 50A then a transfer switch makes sense. I have another question like this and I have the research on my to-do list to delve deeper.
Great video Richard, thank you for sharing your knowledge. I was wondering what recommendations you have if I am back feeding a sub panel with a portable generator? Obviously the neutral and ground are already separated in a sub panel so should I leave the neutral/ground bond in the generator? Would it be a good idea to ground the generator chassis as well?
(50 amp generator receptacle, Westinghouse 9500 DF, interlock installed on main breaker of sub panel)
Thanks for the question. Back-feeding a sub panel is tricky. This is because you can't use the generator to also back-feed the house since there isn't a way to do the mechanical interlock. If you have a mechanical interlock between the generator sub-feed and the sub-panel main, then it's safe... but is that your intent? One neutral-ground bond is required in the system and in the case of a sub-panel, that bond exists in the main panel in the house.
Richard, Thanks for making this video. Lots of questions for my scenario :). In my setup, the load center with the main breaker is on the outside of the cabin and I was intending to add the generator receptacle near it, mount it 2" away from the load center. Am I correct that the technique mentioned here of lifting the ground bond in the receptacle won't work in this case because being outside, rain could cause the two separate grounds between the load center and the generator receptacle to conduct? If this is a problem, what would the solution be? Is the only option without using a transfer switch to unbond the ground and neutral in the generator? If so, is the grounding rod not necessary for the generator or is it still a good idea to have it, even though it's grounded through the cord? Also, for the XF8500EFI, what size breaker did you put in your load center and what size plug in your generator receptacle, given that this generator only has a 30 A 240 output plug, even though it technically can support a total of 35 Amps and more for peak loads. Since the generator has a 30 amp breaker, do you just match that value with the breaker in the load center. Also what type of circuit breaker did you use? Does a GFCI breaker work for a generator in all of these configurations (N-G bond split in generator or House ground not attached to N-G bonded generator)? Thanks!
Thanks! I would remove N-G bond in the generator and have an alternate ground from generator frame to service ground (if not using a ground rod and assuming the existing service has a ground rod currently).
I used #10 wire, a 30A/2P breaker and 30A connection receptacle to match the 30A twist lock on the generator.
Great video! I think I am getting it but just to clarify. If I have a neutral bonded generator and am only switching the 2 hot legs at the house then I have 2 options. Either Unbond the generator OR lift the ground conductor from the generator to the house and then ground the generator to its own rod. Does that sound correct? Is one of them preferred over the other? Thanks!
Lifting neutral-ground bond at the generator is preferred and the legal way to do it. My method is borderline (best alternative) but technically safe.
Just remember to reconnect the bond when running stand alone.
running a predator 9500 generator for whole house thru an interlock, i was told to also ground my generator to the same grounding rod that grounds my house. can you give me your opinion, just want to be safe for generator and house,thanks
The local AHJ or inspector needs to be consulted, but the case you want to make is to prevent two neutral-ground bonds in the system when running on the generator, since that can energize grounded parts. A second ground rod is recommended, not the same ground rod. We want our reference to be earth, that is what grounding does, but we don't want a low impedance path between grounding points on separately derived systems.
Richard,
Thank you for this information.
I have an Eylander Electric Meterbase combo which has the power inlet L-14 30 plug mounted on the bottom of the steel enclosure and uses a breaker interlock to switch power from utility to generator.
I have a Generac XT 8000 EFI with a bonded neutral and a 10 ft. SO cord to attach from the generator outlet to the meterbase inlet.
I want to leave the neutral bonded for warranty and insurance purposes.
It appears to me, for drawing purposes, I would want to draw a ground rod attached to the generator frame and leave the ground wire from the SO cord capped off inside the meterbase enclosure and I am wondering if you would see that as a correct drawing.
Also, it appears that the NEC requires a back fed breaker to be mechanically secured to the buss bar, ie bolt on or clamped but not the pressure fit type.
Thank you fr your time and knowledge.
Thank you for the comment! The mechanical interlock kit is UL Listed and secured to the dead front. Of course, someone can remove the dead front but then they can also remove breakers or move wires, so the Listing assumes a legal installation with a dead front on for plug-in breakers.
In your case, if you want to leave the neutral bonded in the generator, AND your meter base has a solid neutral (not switched), then you read the diagram correct. The ground rod is optional, if your home already includes a ground rod, since the generator will be able to use the home's ground rod.
Can I run 10/2 to the gen connect box from my panel since I'm lifting the ground anyways? Just using the bare ground wire as the neutral (similar to hot water heater)
I would not use the bare conductor as the neutral, as it will be too easy to accidentally bond it. The other reason I like 10/3 + GND is it offers the future ability to run a separately derived generator. My next video will explain how to lift the N-G bond in the portable generator (it's fairly easy) and offer a solution to add a toggle switch on the generator for bonded or lifted operation.
I'm going to hook my bonded generator to a electrical panel with multiple outlets on different breakers so i don't have to unplug cords , just turn on / off breakers the panel inside the house is wired as sub box with neutral and ground separated. So i would have to use a separate ground rod to generator or can i connect to same ground rod outside that house panel used? Hope this makes sense??? This panel isn't hooked to my service!!
Makes sense. You don't want the bonded generator to create a separate ground loop in the system. It's good your subpanel has a separate neutral bus and ground bus. In this case, I would treat it the same as my video. The main panel has the only neutral-ground bond, the ground is isolated at the generator receptacle, and a separate ground rod is installed for the generator (tied to the generator receptacle).
You can also refer to my updated video where I modify my portable generator to be floating or bonded. ua-cam.com/video/FvHQNGu7Xa8/v-deo.html
11:33 The inside panel is not connected to my electrical box. I'm using a electrical panel as 😢a distribution center for several outlets on different breakers to turn on and off as needed
Using a 30amp twist lock cord and a 30amp inlet box on the panel to juice it up (not connected to my service)
Hello Richard, I am doing something almost like your example here, about wanting the ability and flexibility to power my whole house by merely selecting the breakers I want to use during an emergency. I have an outside Main Panel with 12 breakers, all of them 2 pole 30A breakers...so 6 pairs of 30A breakers. 5 of these pairs feeds high current loads (Dryer, oven, cooktop, and 2 A/Cs), the last pair feeds a subpanel in the garage with 6/3 w/G Romex.
In an emergency, I am not interested in feeding the 5 high current loads, I want to use a generator to feed (6/3 w/G Romex) the subpanel only and from there select the loads I want (all single pole 20A breakers). I am using a 3PDT safety switch to alternate from Utility to Generator source with one load (the sub-panel). Assuming that my generator is bonded, the safety switch is grounded but not bonded, I should be ok. Do you agree?
I think I understand your situation. Let me ponder it for the evening and reply tomorrow.
@@richardvedvik979 Thanks for taking the time to think about it.
A few more details:
the Main Panel and Gen source are bonded,
the SubPanel (Load) is not bonded (of course),
the gen receptacle is grounded,
and the safety switch has a ground bus for all incoming grounds.
Hello, a great video - thank you! A question I have, if it can be answered, is what if a person is connecting the generator to a sub-panel with an interlock kit to power an outbuilding that already has the ground separated from the neutral in the panel? Would floating the ground on a bonded generator still be required or recommended?
The out building cannot have a neutral bond, it uses the neutral-bond at the main panel. Therefore, when connecting the generator the same situation as I describe applies. Both the out building and the generator will use the neutral-ground bond in the main panel. Ideally, you'd use a transfer switch to break the neutral connection then you can run the generator bonded as a separately derived system.
Is there a minimum required distance between the ground rod from the generator and the ground rod/water main from the home? I suspect with a bonded generator and a bonded panel, a parallel path situation--even with a break of ground at receptacle box--could still exist causing breakers to not trip in a fault condition.
I should have taken time to explain that a second ground rod is not required if the existing home is legally grounded already. I showed it just in case the existing home lacked a ground rod itself. It was also a bit of a CYA because manufacturers will say to provide one. I believe that if the home already has a ground rod, having one for the generator is not required.
Richard I Have a bonded Neutral to frame generator. I used 8/3 wire with copper ground wired to an interlock 30 amp 2 pole breaker in the panel. I disconnect the ground in the generator 30 amp metal inlet box from the panel and insulate it so I wont have a double bonding. Do i still need a separate ground rod wired to the generator grounding lug?
Nice work. You do not need a separate ground rod for the generator if the home already has a ground rod.
@@richardvedvik979 Thanks for the very informative video.
Nice job with this video. I have a mobile grounding question. In a camper, with shore power disconnected, should a floating neutral inverter be bonded to ground or not? The inverter chassis is grounded to the camper frame, but there is no ground rod since it is mobile.
Thanks, always follow the rule that there should be one, and only one, neutral-ground bond in the system. In each scenario, assess where your one N-G bond is, then anything else that connects needs to be a "floating neutral" as that equipment relies on the one N-G bond in the system.
Great video! I have a question that I hope you can help. I’m wanting to reuse wiring from an old hot tub for a generator inlet. The problem I’m running into is the wiring is only two hots and a ground and no neutral wire. Is there a way to make this work safely?
Sadly, it is not recommended that you try to make that work if the ground is a bare wire and not insulated. If the ground wire is insulated (green), and if the generator has an internal neutral-ground bond, then maybe you could recolor the wire with white electrical tape and use the method I explained. Obviously, moving the old hot tub breaker to the top for an interlock with the main is needed.
@@richardvedvik979 Thank you for replying. The ground unfortunately isn’t insulated. I guess I have to rewire.
Great explanation Richard. I have removed the bond at the generator. Standard interlock, so neutral is not switched. Generator is now not to be used stand-alone. Does this then mean the 20 amp receptacles are not to be used when the generator is supplying the house through the 30 amp outlet? Also, it seems the additional ground rod for the generator is allowed but not necessary? Is there any danger to the generator ground rod use? It seems to me that if the 30 amp is connected to the house, the use of the 20 amp receptacles would be okay.
As you suspect, it is fine to use the 20 amp receptacles when the generator is connected to the home since it uses the home's neutral-ground bond. You are also correct that the additional ground rod is not required if the home already has a ground rod.
When energizing from the utility why not just unplug the 4 prong plug at the generator receptacle since you're not using the genset? Then there's no extra paths... Then when you are using the genset, make sure it's not bonded at the genset. BTW, you show a ground rod at the genset in some slides. Ground rods are for lightning strikes. Are you afraid that lightning is going to hit the generator? If lightning hits the house while using the genset, it's going to blow up the genset anyway!!!
Thanks for the questions! I'll start with the second one first - we aren't using ground rods for lightning, we use them for voltage reference stability. The reason we have two grounding paths in homes (two rods or a rod and a metal water service pipe) is to be redundant in case one is lifted. What can happen in homes with only water pipe bonding for grounding is plumbing work can break that connection (or a meter jumper connection failure) and the voltages seen in the home will vary wildly. Same reason for the generator. Now, in those images the dedicated ground rod would be redundant since we're actually using the home's ground rod for reference, but in the event we have an issue with the neutral connection, we'd like to have a solid reference.
For the first question, the generator is usually unplugged, that I agree. But the situation of two neutral-ground bonds exists whenever the generator is connected. I explained what happens with the utility as a source just to be complete in my analysis, but it's not what we're interested in. What we are concerned about is unsafe conditions when the generator is connected and we can have some current passing through metal surfaces, allowing for a potential path through the human body if conditions are right.
In your opinion does this all hold true for a 120 Volt Floating Neutral 37.5 Amp 3 wire connection, with no ground rod at generator.
We only want one N-G bond. If you have a floating neutral, you would connect all three wires to the panel.
Thanks@@richardvedvik979
The video presents logical and clear reasoning on this important topic of safety. However, I disagree with the suggestion to separate the grounding system. According to the National Electrical Code (NEC), the grounding system should always be connected as a whole. All grounding rods are connected to the same earth, and metal pipes such as water, gas, and electrical conduits are also all connected. It is not guaranteed that separating the ground will be effective, as it is likely that they will still be connected somewhere, especially when a grounding rod for a generator is used. To properly connect a neutral bonded generator, such as an F-150, to a home, a three-pole transfer switch like the Generac 6852 (manual version only, as the automatic version does not switch the neutral) should be used to properly separate the neutral.
I certainly agree that the best solution is a 3-pole transfer switch. Professionally, I design separately-derived systems whenever possible. I evaluate existing hospital campuses to determine multi-generator bonding scenarios.
That said, telling everyday people to spend thousands of dollars to connect their several hundred dollar portable generator is not realistic.
This video is intended to meet people where they are at. I am providing a safe solution that is free, and is much better than leaving two neutral-ground bonds. People back-feed panels way more frequently than they install 3-pole transfer switches. Consider this solution for the intended audience.
I'm very familiar with NEC Art. 250 as well as IEEE Green Book. That is why this solution lifts the ground from the panel since the panel cannot energize the enclosure.
Thanks for the comment!
I’m going to get a gas powered, portable generator that I’ll be using to power my house during power outages but I also want to be able to use for other things. Would it be wise to put a switch on it that would allow me to bond or float the neutral as needed?
I didn't recommend this because it affects the warranty, but I agree that a switch on the neutral-ground bond seems like a nice way to solve the problem and allow for both scenarios. You'll need an adequately sized switch, a 30A SPST in my case, that is mounted to avoid inadvertent bonding to the frame, and the cables should be adequately insulated as they leave the generator casing.
@@richardvedvik979 Thank you for the advice.
Well for my generator the 50 Amp Receptacle is not bonded but all the other receptacles are. This is very important to what you are saying but does not violate the required bonding for other applications.
Thanks for sharing. In each scenario, the location of the one neutral-ground bond should be known and additional N-G bonds should be avoided while still allowing for a short-circuit path to the source.
@dvedvik979 Well bonding is very important to me as while my generator is fed via a circuit breaker the power is being fed into a pair of 120 volt inverter chargers which are then connected to an autotransformer which feeds the power panel that powers my emergency circuits. Mains power also feeds those inverter chargers and it is these inverter chargers that determines which of those sources are providing power to the circuits. Batteries can provide extra current when on mains and provides all power when mains is down. The generator is on autostart when the batteries are down to a preset voltage and the generator will receive a stop signal when the batteries are charged and reach float current. The mains panel is the only bond in this whole scenario which is very important, all else must remain unbonded to ground.
It would be nice if generators came with a switch for converting a bonded neutral to a floating neutral. I think your idea for dealing with this situation looks good, but instead I dealt with the situation that appears to be the common way. My generator wiring is very similar to your generator. I removed the neutrals from the ground wire at the generator and combined them together while leaving the ground wire attached to the generator housing.
Thanks for the comment. I will do a video shortly on how I will add a toggle switch to allow for manual operation of a neutral-ground bond.
It all sounds like good, proper advice, except Generac in particular does not make a good generator set, perhaps unless you get one so big that it is liquid cooled and 1800 rpm. Which will of course be a fuel guzzler.
Thanks for this awesome video... In trying to understand all of this, I kind of have a side/related question. The dangerous condition where you're showing abnormal neutral current on the ground parallel path.... don't alot people have this condition in their homes currently (with no generator in play at all) with electric dryers that bond the neutral and ground at a "second" (perhaps one of many including stoves etc..) location? How dangerous is it having additional neutral/ground bonds connected to your "system"? i.e. what are the scenarios that would get you shocked/killed with a bonded generator (without ground lift) and even with 3 wire dryer/stove/etc scenarios?
Thank you for the questions! It is a Code violation to have multiple neutral-ground bond paths due to concerns with circulating ground currents that can be hazardous. As with many things in the world, many homes have very dangerous wiring that results in both death and fires every year.
It is fairly easy to correct for multiple neutral-ground bonds, just break the bond and run a separate ground, if necessary.
The scenario that can cause injury or death is when someone comes in contact with a ground loop (i.e. exposed metal surface) and simultaneously makes contact with a separate bonded surface in which current passes through the body/heart. It's serious enough to warrant changes in Code to account for it.
Hey so if I want to use the watchdog connect with the Generator to my house back up. The generator is self is floating neutral. if the only way I got power out with out error code, i bound the generator but When I feed to my house it has own neutral. Surge protector not seeing the neutral through my house only allowing power when I bounded. If this case it's gonna be 2 neutral. What to do at this point?
If you connect the generator to your house before you start it and leave the neutral floating, I'm guessing the error goes away because it sees the bond in the house. Can you verify that?
@@richardvedvik979 yes I tried both ways. Just connect the surge protector and start the generator. It is giving me open neutral error then hook the house power to the watch dog, Turn off the breaker and tired again same problem. But if I hook up the house power to the other outlet on the generator the watchdog is works just fine but house power through the watchdog it’s not detecting the neutral
Let me ask a slightly different question but sometimes equally as confusing. I installed a hot tub a few years ago it is a 3 wire 240 volt only system it has a GFCI breaker outside at the remote shutoff area which is actually an additional question of can a GFCI breaker actually work as a GFCI breaker on a three wire hot tub? But the current question is when I installed it I did not completely understand path back ground fault situations as you have been discussing and I installed a earth ground rod at the actual hot tub or very near it... so I currently have two Earth grounding rods they are probably separated by at least 25 or 30 ft... can this create a problem during a lightning strike or a ground fault event?
Several Code sections require additional earthing ground rods for exterior loads. No concern.
A GFCI breaker is required for 240V Hot Tubs and can work properly if it is installed properly.
@@richardvedvik979 ok ..and i connected the green on the hot tub to this earth ground rod near the hot tub as well as through the GFCI box green all the way back to the main panel separate form the neutral. Actually with a 3 wire tub the neutral coming form the main panel to the GFCI box it just an unused wire? because the tub only has terminals for L1 L2 and ground
Thank you for a well put video on bonding, I have a question, do you know anything about BLUETTI 500pro?
I can include this product in a future video that focuses on solar and other renewables. Thanks!
How would you setup an off grid solar system with a backup generator? 48 volt all in one inverter 3500 watt output connected to a sub panel breaker box on the feed out side of the inverter.
This is a pretty in-depth question. I'm happy to talk through this with you, but email would be more useful start so product links and cut sheets can be shared.
@richardvedvik979 I would greatly appreciate any insight you may be willing to share. Give me a few days to put it together on what my system is and how I have it set up currently and what my concerns are with the grounding for this system. Thanks for your interest in this matter. Best regards, David
I'm going to back up my home electrical power with an inverter/generator. My generator comes from the factory with a bonded neutral so I need to do something to avoid using the generator neutral bonding along with the neutral bond in the home electrical panel. What if I just leave the ground wire from the panel to the connection box for the generator power floating - not connected to the generator? Will that fix the problem without having to modify my generator? Is it okay to do this?
Missed your question, sorry for the delay. In this video I make the case for the ground at the connection box to come from the generator, not the panel, because the connection box is only powered from the generator and not the panel.
Very good, I understand. In my case the connection box is plastic - non conducting and has nowhere to make a ground connection on the box. So the ground wire from the generator comes to the box and is terminated - going nowhere to prevent the generator Neutral to Ground bond from interfering with the utility bond. Therefore, generator power is bonded through the same bonding connections as utility power. Does this sound correct? Thanks for your reply to my questions. 🙂@@richardvedvik979
@gjlaird what you describe is the same as my recommendations. Nice work. A plastic box is a useful here.
If you disconnect the ground at the generator receptacle, the neutral is bonded to ground in the panel, why do you need a ground rod? A bonded generator is bonded both at the generator and the panel. The panel is already grounded from the utility.
Sorry for the delay. I show the ground rod because that is a requirement of the generator manufacturer and the NEC. But in my personal application, I do not need to connect a separate ground rod because, as you state, the grounding of my home panel is modern, legal, and functions as needed. Simply put, I showed it for legal concerns because there are scenarios where the ground fault sensors may not function properly if panelboard grounding is insufficient.
I have a generator that has a RV Y receptacle so to me that means a neutral and a black 120 and a red 120 but no ground. Is it legal to use an adapter RV to 4 prong 30 Amp receptacle? Or use an extension cord Rv to a RV receptacle on the house. Either way would not connect the ground.
If grounds are not being connected, then a separate ground rod is required. There should be a reference to earth. You also want to make sure that you have 240V between black and red if you're going to back-feed your panel. If you just have two 120V outputs then feeding devices directly with extension cords (and maybe an EZ Generator Switch) would be the safe option.
An RV 30 amp system has 1 hot, 1 neutral, and 1 ground. It is 120 volts only, no 240 volts.
Hello Richard. I am in the process of connecting my newly purchased Firman generator which is N-G bonded to TWO circuit panels which are fed from a single meter through a dual log set up. One panel is 150 amp and the other is 100 amp. My plan is to connect the 50 amp outlet from the generator to the 150 amp panel, and the 30 amp outlet from the generator to the 100 amp panel. The generator has a 50 amp total draw capacity; but I want to be able to power the whole house while staying below the capacity of the generator. Having two panels from same meter through dual log doesn’t change your theory of lifting neutral at the inlet boxes, correct? I don’t like my two panel setup, but this is how the house was built. Assuming the theory doesn’t change, is there a difference in lifting ground at the inlet boxes or at the panels? (I.e., just don’t connect ground to ground bar at the panel). Will appreciate feedback on this situation
Hi! Only one N-G bond can exist in your system. Not one per panel but one in total on the property. Only one. And likely at the meter where the feed is split. You need to evaluate this first, then report back.
Hi. I checked the setup of my dual service panels and here is how they are wired. The GEC is first bonded at the 150 amp panel to neutral. Then, a “jumper” grounding wire is tapped to the GEC via a split bolt. The grounding wire is bonded again in the second panel. Both panels are also bonded to water piping system with meter imperfections Your comment about bonding at one point in the building got me concerned. So I researched this and apparently bonding should take place at the very first disconnect point, which in my case are the two separate panels. Maybe this point is open for debate. With that said, what is the ‘safe’ way to connect my two separate generator inlet boxes? Your input is appreciated
@@samerjomaa5134 what is the wiring between the service entrance to each panel? Are there two phases, a neutral, and a ground wire for each panel? That would be 4 wires total to each panel.
Hi. So the service entrance is dual log as I had explained. Two hot lines, and a neutral are run from meter panel to each electric panel. These are basically branched out from the two hot lines and the one neutral from utility. A grounding wire first goes to 150 amp panel and then a jumper is run to 100 amp panel. So each panel is considered a first means of disconnect for the circuits they serve. But the two panels are basically fed from the same service lines. Hope this was clear.
What happens if a ground fault occurs inside the cord itself? One where the ground wire is completely severed, and the hot is only touching the part of the ground wire that leads to the j-box? And what If the frame of the generator gets struck by lightning, the absence of a copper ground leading to earth could result in problems no? On a different note, if the generator was a floating neutral orientation, what even is the point of having a 4 wire cord, other than for lightning protection?
You'll notice that I show a ground rod in the diagrams, for the concerns you've noted above. If you have two N-G bonds, you intentionally put current on grounded parts every time you use the generator. If I have to choose between energizing metal parts every time its used versus a concern with a rare scenario, I'll chose the latter. Cords should be inspected prior to use, to your point. A connection to earth (grounding) is certainly recommended when connecting to your house since a home is a likely target for lightening. But if you run a generator in a stand-alone application, as portable generators are, there is never a ground rod present. The way we design lightning protection is with the "rolling sphere" method, and in most cases, the home protects the generator given the height difference and proximity to the base of the building.
Can you use extension cord and cut off male end and use a replacement male end and tie all three wires too ground ( nothing to hot or neutral blades ) wrap end up with. green electrical tape . Çut off
Female end of existence cord and put all three wires into a circle fitting crimped (3-wires) no hot or neutral wires. Tape that end with green electrical tape to identify it as a bonding to earth then connect to generator ground bolt and plug the male end into home to gain access to your homes ground rods.
How do earth ground rods protect from utility or generator faults. In general, electrons have a very hard time traveling through dirt. The impedance of dirt is quite high. I would say earth ground rods are good for lighting protection.
Sorry I missed this. It's not that we have electrons travelling through earth like we do the "hot" or "neutral". The earth is just a consistent voltage reference. You see, voltage is a potential difference that is relative to the "reference". We use earth as the reference for consistency. You can see what happens when we lose this reference when grounding is removed from a system; voltage will fluctuate wildly. We do use ground rods for a low impedance path for lightning but we also use ground rods for a voltage reference.
I like this video, i am an electrician. Only thing im not sure about is why you want a floating neutral for only a permanently installed generator? Why wouldn’t you want the same for a portable? My portable has a floating neutral. My bond is in my meter which has a 100 amp breaker.
Thank you for the comments. We need a floating neutral for permanantly connected generators that use a 2-pole transfer switch (solid neutral). We can only have one N-G bond in the system.
However, if we want to use the generator in a portable scenario, we need the generator to be bonded internally. The latter scenario is why I made the video, for people that have a portable generator that they want to remain useful in portable applications.
I have a 7500w Generac portable that was factory wired with a bonded neutral. The owner’s manual has both schematic and physical wiring diagram illustrations. I found the n-g bond at the duplex receptacle on the generator. I was able to remove that single bonding wire to make it a floating neutral.
As I typically use my generator for house panel hook-up (via a 2 pole transfer switch), I made this change to the generator wiring. I also took a 3 wire male plug and made a bonding plug, jumping the ground to neutral, in the event that I wanted to "re-bond" the generator externally for stand alone use, if needed.
I would love to have you as my neighbor. 😂
Frankly, I don't see how anyone can follow this video. The picture is blurry so the words on the diagrams are near impossible to read and at a glance the diagrams appear too similar. You need to POINT to the items you are talking about.
Great feedback, thank you. The differences in each image are the highlights, but I was disappointed in how the program rendered the high resolution images into the final video. I'm viewing on a large monitor, and I don't think a phone is a sufficient device for reading the diagrams. The images are intending to support what I'm proposing and are really only necessary for those looking to critique technically or follow along with my process for determining if the ground-lift approach is safe.
To read the diagrams I had to view full screen on a computer monitor.
@@massengineer7582 agreed. There is just too much detail to view on a phone. I chose to use a traditional one-line diagram format so those in the industry would recognize the symbols. I chose to not simplify the concept with playful animation. I'm not sure how I would make such fine detail visible on a phone. I spent a decent amount of time playing with visibility but I think there is an opportunity for future videos to have higher resolution and maybe simpler animations. Happy to take recommendations for animation software.
I’m looking at Tri fuel generators. How important is an inverter style generator?
The inverter-type generators produce much less distortion (THD) than traditional multi-fuel generators. The concern with high THD (greater than 10%) is the impact on sensitive electronics in modern devices. People have reported issues with modern furnaces and their sensitive electronics. So the importance of limiting generator THD depends on what you are powering with it.
In South Africa we use the TNCS earthing system (bond is done in the meter kiosk located outside of your property) the code prohibits you from relying on the utility bond for a small scale embedded generation device such as a generator, we are to install a transfer switch that switches both the hot and neutral legs from utility to alternative supply so essentially when you switch to mains you remove the bond in the generator this way there is no parallel path either when getting supplied from the grid or alternative supply, a grounding rod is also compulsory with a earth resistance not higher than 3ohm for alternative supplies the ground rod must be bonded to main consumer earthing terminal, personally i like your setup much more but this is what you get if you live in a 3rd world country
A transfer switch that also switches the neutral is the preferred solution, for sure. Great comment!
At 10:42 when you are discussing lifting the NG bond in the generator, is this essentially the setup for a floating neutral generator where this is no NG bond to start with?
Correct, except we won't operate it as "floating" because we will connect to the home first, using the N-G bond in the home.
@@richardvedvik979 Thanks. We have new bonded and floating neutral generators (at different houses) that were purchased after the recent ice storm and I was wondering what the different hookup would be for the bonded vs the floating style. Your video actually helped me understand each type.
hi Richard. I am very suspicious of the TDH spec of < 5 % on this generator (XT8500EFI). This is as good as an invertor but this generator is not an invertor. have you ever measured the THD and after 1 year do you still recommend this generator for house backup with lots of sensitive electronics inside.
I had the same concerns as you. It seemed hard to believe considering they didn't establish additional technology other than the fact that it's fuel injected. So, I could always reach out to the engineers at generac since I can interact with them when I specify their larger commercial generators. I'll let you know what I find out. I do expect that that THD is at no load. But considering that it was so much low than others published and I can run my entire house on it for as long as I want and use everything in it with no issues I can honestly say that I'm still happy with the decision.
@@richardvedvik979 Thanks I am interested in what they say about it. The only thing I wish is that it was dual fuel but other then that it is far less expensive then an Inverter of the same output. Other then that it ticks all the boxes for me. I am installing a Genlink on my house to connect it to
Very informative video but for someone (like me) that might not fully understand what was in the video I have one question. I am going to purchase a generator that has a bonded neutral. I am going to have an electrician install the sliding interlock device on my house panel. The question is, should I disconnect the white wire in the generator (and secure) to make it a floating neutral and/or will the electrician do some kind of magic in the house panel to compensate for that?
You will want the generator bond broken in the Generator to make it non-separately derived. Just know it won't work stand-alone without being connected to the home.
@@richardvedvik979 Thanks for the reply. That is what I thought. Just to be sure, using terminology I see on UA-cam, in order to use a portable generator connected to the house panel through a power inlet box it should have a 'floating' neutral and to use a generator as a true stand alone unit to operate power tools, etc it should have a 'bonded' neutral.
@@goodeye2179 your understanding of terminology is correct. Nice work.
Well done
Thanks
what is the JB mounted to, overlapping the PVC ?
Secured to the exterior wall with blocking for support/standoff.
Whats the problem connecting a 120 gen. to one side or both legs of the panel box ?
This can be a long answer but you certainly do not want to do both phases, or "legs", because any 240V loads could be damaged and certainly the 120V generator can be quickly overloaded.
Assuming you had a mechanical interlock and assuming you fed an interlocked 2-pole breaker of appropriate size from a 120V source, opened any 2-pole breakers, and you managed 120V loads to prevent overloading, it may function.
@@richardvedvik979 Thanks for the reply, Could I just put the circuits I want on just one leg and supply 120 from a 120 gen to just that leg ?
Wondering if you made any headway with regards to connecting the F150's bonded-neutral generator function with the lifted ground that you illustrate here. I appreciate all your efforts and explanations! Very well done.
That is a topic for a video that I need to do more research on before I go public with recommendations. I need to dig in a bit more on exactly what that system entails and get some schematics of what it looks like. Thanks for the reminder and the comment, appreciate it.
@@richardvedvik979 Someone referenced your video here as a information about lifting the ground for this set up.
@@bohalrantipolThank you for letting me know.
I will soon have a Ford F-150 Lightning EV that has a 30amp 240v connection like a generator. Ford sells a very elaborate system to power your home with the truck costing thousands for the hardware then more for the installation. So People are trying to feed their panel with the trucks power through a generator outlet/interlock but they have found the trucks GFCI will trip immediately because the truck and main service panel both have a bonded neutral/ ground. People have gotten past this by doing what you said by not connecting the grounds in the generator outlet box. (Some comment that this is not safe) The only part that doesn’t match your setup is that the truck would not have a ground bar. Your thoughts?
This is a unique scenario. I need to study the schematics for the EV to comment. Hold tight
@@richardvedvik979 any updates?
Utilities at least in my area won't re-install the meter unless you have the city inspect it first. The city won't inspect the work without a permit for the work you did. I just turn the main breaker panel off when I'm doing work inside my main panel. If a city inspector saw what you're showing the video, they would fine me for not having all that wire inside conduit or inside wall. Maybe codes are different where you are.
My work is permitted and inspected by my local city. I have a good relationship with my local building inspectors. I agree with turning off the main when working in a panel, but you should also ensure the incoming lugs on the main breaker are insulated. I like using a 3M Mastic for this purpose (applied with 1000V insulated tools if the line is hot). In my case, I was able to fully insulate the incoming lugs before the panel was energized since I did the panel swap (also inspected and permitted). The wiring added is in conduit, because ENT is an acceptable form of raceway in the NEC. You just don't see ENT very often because it's ugly. In my case, I couldn't use metallic conduit because it would result in undesired bonding, and two N-G bonds is much worse than the aesthetics of ENT.
we can't read the words in the diagram....can you make it bigger...thanks
Excellent point, I should upload a copy of these slides and then share a link. I'll do that at my next availability. Thank you for your comment.
So... if I understand your diagrams, it looks like you will have a separate ground rod for your Generac portable generator, which is bonded, since you lifted the ground at the generator receptacle, correct? My ground is not lifted on my setup, which is using a mechanical interlock on the main box, and my generator is neutral bonded. If I understand correctly, it appears that I should either remove the neutral bond at the generator itself (which doesn't seem to be typically recommended per internet research) or lift the ground at the generator receptacle, and install a ground rod specifically for my portable generator. Do you agree? Thanks for the great video!
I will publish a video on lifting neutral-ground bonding in a portable generator soon. It is perfectly fine to lift that bond if you never intend on operating the generator independently and you just connect the generator to your home (breakers off) BEFORE you try starting it. But this video explains how to connect a bonded generator to a bonded service panel and eliminate the dual neutral-ground bonds.
This video was very informative. My only question is the use of an additional grounding rod at the generator for the last illustration (bonding at Generator and Panel, lifted ground at generator receptacle and generator source). Since this setup is using a shared neutral, the generator is still tied back to the dwelling ground rod through the neutral and the bonded panel.
@@stevelovato7577 the ground rod is not required by NEC 250.34 if certain conditions are met. Bonding of the generator frame to unit-mounted receptacle ground pins is required. This should be the case for most installations.
Thanks for this solution Richard. Ive been trying to figure out a cost effective way to hook up the F150 onboard generator for backup power and I think you're on to something here. Im wondering if this would work if you connect the generator receptacle box directly to the grounding rod instead of the generator frame?
Since you cannot modify the truck inverter (since it needs to operate stand-alone), I would use my solution if I had the F150 generator and wanted to back-feed a mechanically-interlocked breaker/generator receptacle for my own home.
Yes, the generator receptacle box can be grounded directly, you can run an EGC directly from the box to a ground rod.
@@richardvedvik979 The 150 is a floating neutral. A separately derived system...the question is will Ford let you bond your neutral without issues?
@@ezgeneratorswitch4u Why do you say the F150 is a floating neutral? It is my understanding that it is bonded.
@@Rahbeckm Bonded to what? the truck sits on 4 tires.
Hello Richard, I liked your video. I have a stand alone solar panel array powering batteries and a Xantrex X2000 inverter. I would like to use the inverter instead of a generator to supply power to the house in case of a power outage. The inverter has it's neutral and ground bonded internally. Would your way of not connecting the ground wire from the generator to the ground in the junction box work with using the inverter? It seems as though it should. One thing that I am not sure about is dealing with GFCI outlets. Do the GFCI outlets need to see a neutral ground bonding connection? I would love it if you could do another video on interfacing a single phase 120V sine wave inverter to a main circuit breaker box to supply electrical power to the home. Thanks, Richard Phillips
Interesting idea, but a popular idea using solar and an inverter to power items directly, stand alone. Let me do some research and sketch pathway.
Using a 3 pole transfer switch is the primary recommendation as it allows for two neutral-ground bonds.
@@richardvedvik979 I thought of that except I was thinking of 2 pole transfer switch for the hot and neutral. Right now, I have a Generac transfer switch with a 14L30 male plug for use with a generator. The Generac transfer switch use single pole switches that only switches the hot line. I was hoping the use the Generac transfer switch with the inverter. But, you run into have two bonded neutral-ground instances. I think that I like your idea in your video the best.
@@richardphillips2405 Ah, I see now that you have a 120V output inverter and not a 240V output. I understand your though. Could you swap the switches in the Generac manual transfer switches with two pole versions, like the ones used in the EZ Generator Switch box? Are you still thinking that you want to keep the gas generator hook up available, I assume? If so, how do you plan on interlocking them?
I would probably put EZ Generator Switches for each load at the transfer switch so you can just connect between the inverter and the loads with a standard cord. Then you are protected against any possible back--feed arrangement and you can keep continuous bonding for the solar arrays. I assume you have dedicated ground rods for the solar system.
Hi Richard, thank you for great video. I am confused on one point in the video right around 14:06 mark. In the case of open at receptacle, you mentioned about the need of ground rod for generator. I thought that the neutral line has been bonded with earth grounded at the main breaker. Therefore, the neutral is at earth ground. Since the neutral is bonded to the ground at generator, the generator ground is approximately earth grounded. Are you considering the distance potential distance (length of cable) to the main breaker ground rods? Therefore, the ground at generator may not be as close to the earth ground. On the other hand, at 13:54 mark, you mention that the ground line should be at the same level throughout. I may be missing some concept at this point of the video. I appreciate it if you can help in resolving my confusion.
Thank you for a very attentive question. I show the generator ground rod as a CYA, because that is what the generator manufacturer requires. However, as you point out, as long as the home has a ground rod, I do not see the need for a second for the portable generator.
@@richardvedvik979 Thank you for the clarification.
I'm new to all of this. I saw a video that the generator (duromax 9000) should not be bonded if I want to use it as backup power to my house.
The guy said the bond needs to be disconnected before doing so. Is this so?
That is correct. That is what I am discussing here. You want to open the neutral -ground bond on the generator when you plan on connecting to your house. You won't be able to use it in stand alone mode with it disconnected though. So you'll connect generator to home with cord BEFORE starting it. After running, you close the generator breaker (with main off, obviously).
@@richardvedvik979 thanks. Good to know.
Is this also the case when using a Generlink, if you're familiar with the use of those?
@@aholmes6612 if you have a transfer switch, you can get either 3-pole or 2-pole. The latter requires you break the generator neutral -ground bond, the former means you leave it
How are you liking your generac 8500efi? I am torn between that one and a champion dual fuel 8000 but the THD rating is making me lean towards the ganerac. I like the idea for dual fuel because I have a propane tank for our house but also concerned about electronics.
I was on the same fence you are. Really liked propane option and wanted to build a setup with 30lb tanks and a switchover system. But it would be expensive to get the tanks, regulators, piping, shed, etc.
The Generac is great, runs the whole house, quiet, and very well made. THD being low means we can run WiFi, TV, Computers, etc.
@@richardvedvik979 if it wasn't for your propane issue and the cost would you have still gone with a champion dual fuel with a THD of 12-20%?
@@alexgenereux4704 no, the distortion out of the dual fuel was a deal breaker for me.
@@richardvedvik979 I suspect my Firman will have some distortion. If I run my router/wifi through a UPS, do you think that will help?
@@craigdrogers Most residential UPS are just letting power pass through the UPS and then switch over to battery when the outage occurs. There may be some filtering, but not enough to eliminate harmonics. There was a company that provided large inductors as harmonic filters, since they acted like low pass filters. They were pricey though, since it was basically a spool of 10awg wire around a core.
I actually have a question about a slightly different implementation that I've been trying to get some clarity on. I would like to pick your brain on the subject if you're willing to share a little expertise with me.
Sure thing. What's the question?
@@richardvedvik979 so this may end up being a bit more of an in-depth conversation than me being able to just pose it here. Is there a way I can reach you directly? (email, discord, voice chat, etc?)
@techmonkie2199 an email is fine and if we transition to a phone call, that is fairly common. My contact info should be in my account profile.
@@richardvedvik979 thank you for your willingness to chat! I just sent an email outlining the problem statement. Feel free to reach out with any questions or if this would be better served as a conversation vs email chain. Thanks again!
My DIY mechanical interlock for odd ball breaker and box combo.
As long as it's interlocked, it's good. A UL Listed product is great, but a functional product is just as safe when used properly.
Thank you very much for posting this video and your thorough explanation. In your scenario where you want your generator to remain portable and you are keeping the generator neutral bonded, but lifting the panel ground wire at the receptacle how are you grounding the generator? I don't think it was shown in the video. I'm assuming you would drive a new rod and then connect to the generator only when using it? Doesn't seem very convenient, but would be necessary I guess.
I discuss this around 14:20, that a separate ground rod is a mfr requirement. When portable, using GFCI receptacles is sufficient. And when connected to the building, we do have a path to ground through the home neutral-ground bond.
There is a possibility the generator cord could be damaged and energize the wet ground. The existing ground rod should suffice here, but I'm sure the mfr wants to play it safe, so my official recommendation matches theirs.
@@richardvedvik979 I understand and thank you for your quick response. Great use of diagrams and I wish all content was like yours. I spent a couple hours googling, etc to solve this exact problem until I found your videos.
@@randyg1524 thank you, Randy. I've wanted to make this for a year but the diagram portion held me up. Ideally they would be fancy animations but I don't have time for that!
@@richardvedvik979 I'm revisiting your video because I still haven't gotten my wiring complete and wanted a refresh on the lifted ground at the receptacle. I understand that in this situation the"official" recommendation from both you and the generator mfg is to have a dedicated ground rod for the generator. Why not just connect a permanent ground rod directly to the metal receptacle box? This would seem to satisfy all the requirements, but keep the generator portable.
I reviewed your comment above and see you've kinda already answered that. If the cord from the generator to the receptacle were damaged it would be better to have the ground rod connected directly to the generator frame. Low probability, but something to consider
This is the most confusing thing ever. Just use a floating neutral generator and run all four wires to the bonded service panel and connect appropriately. This provides for a single point of bonding and keeps from creating a parallel path on the generator ground. 🙄🙄🙄🙄🙄🙄
A floating neutral generator cannot be used in stand-alone, which is why they come bonded. I mention your point in this and my other video, and I agree it is preferred to leave the generator floating then connect the extension cord to the house, with the generator breaker open, before starting the generator. But now we're making the sequence complicated and given most homeowners not understanding sequence, this option works for some but not most.
Basically, the point of this video is to provide another way to do something when a floating neutral generator is not an option because people aren't going to modify the generator they have.
Telling people that if they want to connect a generator they own, to their house, they can't and have to have to buy a different generator isn't helpful. Portable generators that are floating, and large enough for a house, aren't that common.
Hate to say it....but I don't understand this video. All I know is that my electrician installed a 40 amp 240v breaker in my outside panel, used 8-3 with ground, attached the white wire to the neutral bar, ground to ground, and wired up the four prong 30 amp twist lock socket/box. Have no idea if this is a problem or not. I plan on purchasing an inverter generator...somewhere in the 5,000 to 7,000 running watt range. I don't want to damage my home. Perhaps this is what I'm looking for..."in order to use a portable generator connected to the house panel through a power inlet box it should have a 'floating' neutral and to use a generator as a true stand alone unit to operate power tools, etc it should have a 'bonded' neutral."
In your case, you want the generator to have a floating neutral. This is because your home bonds the neutral in the panel.
@@richardvedvik979 Thanks. What happens if I want to use this new generator without the direct connection to the house wire system....like using simple extension cords to a refrigerator, etc. I ask this because when my home was wired I had the electrician wire a separate emergency wire system in the house...with a few dead outlets in various locations and two power cords in a storage garage. I've used this several times with a small generator during prolonged power outages.
@@richardvedvik979 So I did some testing...my current generator, which I only used in terms of 120v extension cords (actually a supplemental wiring system in the house with two power cords in a storage garage), has continuity between the neutral and ground on its 120v outlets. Thus it's a bonded generator...correct?
Second, if bonded vs open (or floating if that is the same meaning) is important (which it sure sounds like it is), then why are manufactures not putting a switch on the control panel to change the generator over from one to another concerning neutral? Or do some?
And third, if I make my new (yet to be purchased) generator floating neutral is there an easy way to convert it back to bonded if in the event I don't want it directly connected to the house wiring system? Thanks in advance.
@@spacecoastz4026 If your genny has a floating neutral (for use when plugged into house panel/bond), a simple way to bond your genny ground/neutral for independent use (NOT connected to the house panel), is a male 15/20 amp plug end from the Home Depot (no cord at all) where you make an internal connection between ground and neutral screws and plug it into a 15/20 amp outlet on your genny when needing the bonding. You can also BUY one of these on feebay.
Couldn't this accomplished the generator cord so that the building wiring remains code correct?
The issue I see with lifting the ground in the cord is that the receptacle enclosure would then be ungrounded from the source side, which would be a Code violation and a more dangerous situation. Because the receptacle enclosure is never energized from the building side (due to the mechanical interlock) there is no risk. If the receptacle enclosure and any other junction boxes in the system were non-metallic, then what you propose could be done.
@@richardvedvik979 It's not installed yet but my inlet enclosure will always be grounded through the EMT back to the main panel.
@@johnd9279 Ah. In that case your best bet would be to just break the neutral-ground bond at the generator and leave the grounds connected at the receptacle. I plan on making a video describing this process and showing this. I plan on adding a toggle switch to give me the ability to switch.
Hmm, at 8:00 you claim there is no parallel neutral/GND current with the lifted ground situation. But you didn’t draw in the conductive path between the ground rod at the panel and the ground Rod at the generator. That is definitely a parallel path you neglected to talk about, no?
Thank you for being attentive. :) The soil resistance will vary greatly based on soil type and moisture levels (RHO), but it is not a low-impedence path for current, unlike the conductors shown. We use the ground (GEC or earthing) as a voltage reference to utility, as a way to dissipate static electricity, dissipation of EMF-induced current, and a path for lightning strikes. We recognize that we do not have appreciable current present on that conductor under normal operation, not from the typical source or pathway. We size the GEC for voltage drop, not current. All of this is on the secondary side of the utility transformer - which is the source for our home, and is the place where all current (normal or fault) is trying to return to.
I show the ground rod because it is recommended by the manufacturer and to avoid liability by omitting it in the diagram. Installing a transfer switch that switches the neutral is one way of avoiding the scenario presented here.
@@richardvedvik979 thanks for the reply. But assuming the ground is wet, the impedance could be well under 100 ohms, right? That could give you quite a surprise.
@@richardvedvik979 My generator sits next to the ground rod for my panel. Is it OK to use the same rod for both? Using a bonded generator with your lifted ground.
@@fredsmith9380 if you used the same ground rod, you would have a low impedance bonded ground.
Mike Holt says one ground rod per property….?
NEC requires two ground rods if you cannot use metallic water piping as one GEC. And additional ground rods are required by several sections in NEC. Here is a Mike Holt reference: forums.mikeholt.com/threads/ground-rod-requirements.2561457/
All the grounds can be connected BUT only the neutral is bonded at the first means of disconnect
Correct. Sadly, with portable generators, there are usually two neutral-ground bonds in the system. I agree that the preferred solution is to break the neutral-ground bond in the generator, but that requires modifying the portable generator in a way that prevents it from being used in a "stand alone" scenario. I have a video in the works to describe this.
@@richardvedvik979 Here what I think the real issue is >>> Not everyone is bonding their generators to a ground rod, 99% of all generators are sitting on some type of material of isolation (wheels or rubber pads) and I would guess that 99% of homeowners are not driving a ground rod so there fore when do you really have the generator grounded? Just my 2 cents :)
@@ezgeneratorswitch4u I concur with your concern. What happens for most people is they just live with the two N-G bonds that inevitably occur. What I'm proposing still provides a path using the home's EGC but it does travel on the neutral to do it. The path exists, I don't like the path, but at least there is one.
Professionelles Never use car or pump fuel even not in a lawnmower, because it builds gum which block fuel passages in a carb. also in a low pressure injection systems ! It’s not only the ethanol ( corrosion) which harms a seldom used system . Use Akylat (Aspen . Stiehl ect.
Or aviation fuel (AVGAS) it has a shelf life of 2 years ( for aviation use) . Yes it’s more expensive , but how much do we need ?
All valid points. For fuel storage, we need enough to run the genset for the longest duration we expect. That means 10-15 gallons is likely needed for a few days worth of runtime while being conservative and shutting it off frequently. One gallon per hour is a good plan per 5kW, and you hope to do better than that.
Is Ground Rod required at generator under this conditions?
You'll note that I showed the ground rod when the portable generator was not able to utilize the existing ground rod. The easiest way to accomplish this would be to drive a separate ground rod and bond it to the connection box ground point for the generator.
Could you just make up a ground cord. Extension cord cut male end strip all three wires and connect to ground plug only. Then cut female end off, strip all three wires and attach a grommet to attach to your ground post on generator. Wrap green tape on both male and female end to identify it for grounding only
I have a permanently installed generator and it came with the neutral bonded. All of my transfer switches are 3 pole switches. So this means from what I've researched that this generator is technically not a separately derived system. Do I have to take the bond off since all of my transfer switches are all 3 pole?
Yes, your understanding of separately derived is correct. If those transfer switches have bonded neutrals then you want to lift the N-G bond in the generator. This breaks the neutral-ground loop.
I've seen 3-pole switches without neutrals on 480V systems where they didn't have 277V lighting and remained balanced at 480V. We used high-impedance bonding resistors on the gensets to keep the neutral from floating (wye connected).
@@richardvedvik979 what I'm asking is do I need to lift the bond at the generator. Being that my transfer switches are not 4 pole switches. I thought the only way I could have a separately derived generator is by having 4 pole transfer switches. Maybe I'm wrong
@@TheArtOfConduitBending sorry I wasn't clear. You should lift the neutral-ground bond in the generator if the transfer switches have solid/bonded neutrals (meaning the neutral conductors for both sources and load are on the same terminal block). It's the neutral bonding that matters, which typically (but not always) occurs in 3-pole ATS.
@@richardvedvik979 oh yes solid neutral right. That's how I was sure it had to be. For some reason I doubted myself when the supervisor told me otherwise. After he left I thought about it for a second and thought wait I couldn't have been wrong.
Next time please use a pointer when discussing diagrams. I was scanning all over. Great content otherwise.
@@slawomirlisznianski7537 great feedback, thanks!
Thanks for this wonderful video. Like you, I would like to do this evil thing of backfeeding the house panel with a portable generator in the least evil way. Sorry but dropping the ground at the receptacle is just something I cannot do. Having a receptacle on the side of the house with a ground contact that is not grounded can't be justified to me no way no how. What if somebody comes along and plugs a floating neutral generator into that receptacle? So the evils I am left to choose from is unbonding my generator which seems like the right way, or connecting a neutral-bonded generator. The problem with unbonding the generator is what happens when somebody comes along and takes that generator camping and plugs some electric tools in it? That seems to present a real potential safety hazard. The other evil, connecting a bonded generator, would violate code, but would not present a hazard in a fault situation, at least according to your video. In normal operation with either utility or generator power, the main problem seems to be that the ground wire between the panel and the generator will carry some of the neutral return current. I understand this is a bad idea especially in sub-panel installations, but in this situation where the only equipment connected to that ground wire is the generator, what is the big safety concern? This option would seem to me to be the safest, or the least potentially evil of the three options you consider. I must be overlooking something major, so please clue me in.
Thank you for the comment. As you can see, there is no "fool proof" solution here. Connecting a generator to a home service panel presents a host of safety concerns, including electrocution hazards.
This approach allows for the floating neutral generator to be left as-is, without modification and without inducing current on the ground. I've been hesitant producing a video showing generator modification, but I will soon. Current on a ground is the most dangerous scenario of the options listed because that means any metal surface (panel, receptacle, generator frame, etc.) can present another path for neutral current... you! And since most people touch the receptacle door to lift it, or touch the panel door, or touch the generator frame - I want to avoid what I see as the main hazard.
Maintaining the ground connection from the receptacle to the only source (generator) is what keeps that enclosure safe, when a proper mechanical interlock is present. This means there is no chance the conductors from the panel can be energized without the generator as the source. I do not recommend anyone back-feed a panel without a mechanical interlock, and my other video on generators provides alternate solutions. The approach presented here also allows the portable generator to be used in a stand-alone mode. Note that ungrounded systems exist in millions of homes, as that was the original standard. And it is legal to use a GFCI device to protect 2-wire receptacles in homes, where no EGC is present.
The best scenario is to use a transfer switch that switches the neutral. But that isn't an option for everyone. In my other video, I show a meter base transfer switch that would be the cheapest and easiest method of adding a transfer switch, but not all utility companies will allow that product. It would be a good thing to research, if you're concerned.
Now, the safety feature of my generator is that when the neutral-ground bond is lifted in the generator, it will not start. So, in my case, I can lift the N-G bond and not worry about a stand-alone operation. My new solution, in my case, will be to install a toggle switch on my generator that allows for selection of either bonded or floating, which is the topic of my next video (almost done).
@@richardvedvik979 Thanks for the informative comments! I guess my main error was the failure to appreciate the danger of current in the grounding conductor. I was aware of this as an issue with open neutrals, but didn't consider the risk in the bonded-neutral generator backfeeding the main panel. After reading your response I did some actual math (something I try to avoid) and was shocked to discover that it is not that difficult to contrive a scenario whereby the generator frame or receptacle could give a serious or potentially lethal shock with a bonded-neutral generator connected to the main panel. I was simplistically thinking that the grounding conductor is essentially at 0V potential, and the human touching the generator frame would present such a high resistance that the current taking the human path would be insignificant. The math proved me wrong. I'm un-bonding my generator and attaching a bonding plug with warnings and instructions spelled out. I'm going to make a bonding plug using an L14-30P, and leave that plug in the generator with instructions screaming "do not remove unless connecting to house". Then the generator will be safe to use as a stand-alone, and cannot be attached to the house cord without removing the bonding plug. Thanks for helping me to think this through, and thanks again for the great videos.
One question about your comment: "This approach allows for the floating neutral generator to be left as-is, without modification and without inducing current on the ground." If you lift the ground at the receptacle then attach a floating-neutral generator then you absolutely have to have a ground rod for the generator, right? Otherwise there is no ground fault protection for the generator. Or am I again missing something?
I appreciate your dedication to the cause! Thanks!
The ground rod does not, ironically, provide ground fault protection. A GFP device (like a GFCI receptacle) does not need a "ground" or EGC in order for the ungrounded circuit to be protected. The GFP device looks at the neutral and does not reference the ground or EGC. It is for this reason that you can protect the ungrounded receptacles in a home with a GFCI receptacle (either in each location or at the first receptacle in the circuit with the remaining on the load side of the receptacle.
Another way to look at it is that the neutral-ground bond in the home panel provides a pathway for an earthing reference (ground or GEC) back to the generator neutral, just in a different route that is adequate (because the neutral conductor is full-sized).
You'd be waiting 6 - 12 months to get the utility company out to your house here for a disconnect.
The struggle is real. If someone needs to work inside their panel with the utility live and the main breaker off, I recommend using 1000V insulated tools to apply a layer of 3M insulating mastic over any exposed areas (i.e. incoming breaker lugs and exposed wiring).