Should ground be disconnected on my generator?

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  #1  
Old 08-11-20, 03:55 PM
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Should ground be disconnected on my generator?

I'm about to purchase a Generac GP6500E generator which comes with neutral bonded to ground. The generator will be connected via a double throw safety switch which I've been able to confirm here does not create a separately derived system. (Thanks to Geochurchi and Pjmax for your assistance.) My understanding is that a double ground should be avoided. Given that the generator is neutral bonded to ground and I don't have a separately derived system, should I disconnect the bonded neutral on the generator.

I may be way off in my question and I'm sorry if that's the case but I'd rather not get fried. Also, I'm sorry for not building this into my earlier post but only decided on my generator a short time ago.
 
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08-12-20, 11:42 AM
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The warranty being void if removing the neutral bond is just a bunch of hype. The neutral bond connection is a simple process of removing a screw and disconnecting the jumper neutral wire on one end. If you ever have an issue with the generator that the warranty needs to be invoked just hook the neutral jumper back up before taking the generator for warranty work. You just don't need to tell the warranty police that you had disconnected the neutral jumper. I can tell you I have seen where the manufacture has stated wrong information about not removing the neutral bond when the generator is connected to a house electrical system and I have see some manufactures show in their instructions how to remove the neutral bond. All I can say is it is stated by one of the leading experts in the electrical industry as it relates to safety code (Mike Holt) is to remove the neutral bond to ground at the generator. By Mike Holt for EC&M magazine. Generator – If the grounded (neutral) conductor in a transfer switch is not opened, then the grounded (neutral) from the generator will be solidly connected to the utility’s service grounded (neutral) conductor. Under this condition, the generator is not a separately derived system, and a neutral-to-case bond shall not be made at the generator or at the generator disconnect .
Watch this: https://www.youtube.com/watch?v=yS7usLY9zL4&t=116s
 
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Old 08-11-20, 04:17 PM
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The neutral should not be bonded to ground at the generator if the generator is being connected to a house electrical system. There should be a jumper on one of the outlets that creates the bond that can be removed. Check the wiring diagram that comes with the generator for the neutral bond. Actually it appears the bond is under the cover of the alternator end. Also there is no need to install a grounding electrode (rod) at the generator.

P.S. If you remove the neutral bond you need to place a label stating that the generator has a floating neutral bond. If you ever need to use the generator as a portable you can make up a neutral bonded plug to place in one socket to establish the neutral bond when needed.
 
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Old 08-11-20, 06:23 PM
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I would not do anything to the generator that would void the warranty. This includes disconnecting the neutral to frame (ground) bond if that is quite hidden inside and not specified in the instructions..

While the generator should not have neutral and ground bonded if there is a neutral to ground bond elsewhere in the electrical system, nothing bad will happen if you fail to unbond the generator.
 
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Old 08-11-20, 07:39 PM
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While the generator should not have neutral and ground bonded if there is a neutral to ground bond elsewhere in the electrical system, nothing bad will happen if you fail to unbond the generator.
So a neutral-ground bonded generator can be connected to a main panel (interlock setup) that has the green neutral-ground bonding screw, without any issues?
 
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Old 08-12-20, 04:16 AM
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Usually there will be no issures.

The exceptin is that occasionally a generator owner will have a ground fault circuit interrupter in the generator trip because of the unbroken neutral to ground bond. One method of fixing this is to unhook the green wire somewhere between the generator and the house panel.

If you had to pry apart the inlet box on the outside wall to unhook the green wire there and damaged it, you only broke the warranty on a $25.00 inlet box, not a $2500.00 generator.

If a GFCI unit trips elsewhere in the house then that has nothing to do with imperfect generator connection methods. GFCI units in the house will continue to function the same way as they do with utility power.
 
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Old 08-12-20, 05:52 AM
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OK, I think I sort of get it. Since a neutral bonded generator backfeeding a main panel has two neutral-ground bonds, some of the current flows back to the generator on the ground line. And as @AllanJ points out, this can trip a GFCI breaker on the generator.

And this ground line between the backfed panel and genny is the only ground line that will have this 'stray' current, so it won't affect GFCI circuits in the house.

Since you don't want to break the neutral ground bond on the main panel (which you need for when you're on utility power), and since breaking the bond in the generator would void the warranty, disconnecting the ground wire between main panel and genny would force all the return current to genny onto the neutral wire, which solves any nuisance GFCI tripping on the genny.

But what about the case of a ground fault, where a hot somewhere in the house is touching an appliance metal frame or a junction box? That current is going to flow along the ground wire back to the main panel, and then along the ground wire (and neutral wire since neutral and ground are bonded at the main panel) back to the genny, where it would energize the frame of the genny?
 
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Old 08-12-20, 07:14 AM
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If you have a ground fault up in the house then what happens is the same whether or not you are on generato r power.

Typically the fault (unwanted abnormal) current, here going down the equpment grounding conductor in the branch circuit after energizing the appliance frame, will get to the main panel, take the panel ground/neutral bond to the neutral, and go out to either the utility service drop or the generator. If the fault current is large enough which it usually is, then it will trip the offending branch circuit's breaker in the panel.
 
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Old 08-12-20, 11:42 AM
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The warranty being void if removing the neutral bond is just a bunch of hype. The neutral bond connection is a simple process of removing a screw and disconnecting the jumper neutral wire on one end. If you ever have an issue with the generator that the warranty needs to be invoked just hook the neutral jumper back up before taking the generator for warranty work. You just don't need to tell the warranty police that you had disconnected the neutral jumper. I can tell you I have seen where the manufacture has stated wrong information about not removing the neutral bond when the generator is connected to a house electrical system and I have see some manufactures show in their instructions how to remove the neutral bond. All I can say is it is stated by one of the leading experts in the electrical industry as it relates to safety code (Mike Holt) is to remove the neutral bond to ground at the generator. By Mike Holt for EC&M magazine. Generator – If the grounded (neutral) conductor in a transfer switch is not opened, then the grounded (neutral) from the generator will be solidly connected to the utility’s service grounded (neutral) conductor. Under this condition, the generator is not a separately derived system, and a neutral-to-case bond shall not be made at the generator or at the generator disconnect .
Watch this: https://www.youtube.com/watch?v=yS7usLY9zL4&t=116s
 
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Old 08-13-20, 07:56 AM
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I had the same exact question. Old generator had a floating neutral, new one has a bonded neutral. The new Westinghouse generator manual even gives me clear instructions on how to remove that bond. Being my new transfer switch will be tied into my distribution panel which has neutral bonded to ground, transfer switch instructions say to tie both neutral and ground onto the neutral bar. In that case, if I'm reading this post correctly, I should remove the bond at the generator, correct???
 
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Old 08-13-20, 08:20 AM
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""... The neutral bond connection is a simple process of removing a screw and disconnecting the jumper neutral wire on one end. ...""

When it is that simple, yes, unbond neutral and ground in the generator if needed. But read the instructions and the warranty to see what is and what is not covered.

But if it is complicated like having to take apart some rubber motor mounts and lift the engine and prop it up to get at the bond, or remove the voltmeter from the front panel to get at the bond, then it makes sense to skip that step and go on t the next step of the project and live with the consequences, namely objectionable although not hazardous current flow on equipment grounding conductors.

Even expert Mike Holt, in his video (q.v. preceding) said that the generator left bonded does not pose a hazard.
 
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Old 08-13-20, 08:40 AM
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^ That's pretty much where I come out on this. If I were to only connect generator to main panel, I'd unbond the generator. But since I'll also use it to run tools occasionally as well as to 'exercise' it periodically, it's just simpler to leave it bonded and live with some current flowing black to generator on ground wire between generator and main panel.
 
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Old 08-14-20, 07:23 AM
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Don't buy a generator that includes the nonsense that you would void the warranty if you connected it to a residence in a manner that complies with code. Don't buy one for residential use that makes removing the bond difficult. Write to the manufacturer and tell them why. It might be interesting to use a "contact us" button on their web site to engage in a dialog.

Portable generators should include a bonding switch with clearly stated caution, bonded for separately derived use as at a contractor site or just use of extension cords, and unbonded for typical residential connection to home.
 
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Old 08-14-20, 03:11 PM
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If you think about it, utilities may have a neutral-ground bond at the transformer before the service even hits your house. Then, per NEC requirements, the service entrance has to have a N-G bond, regardless if there is one upstream or not. So a gen set with a N-G bond would not be much different than a utility transformer, just that the gen may have GFCI on its output that will nuisance trip if there is an intentional bond downstream of it.
 
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Old 08-14-20, 03:34 PM
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Portable generators should include a bonding switch
Never happen. Way too much liability. It can not be assumed that an operator can read.

 
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Old 08-14-20, 05:15 PM
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But I say you should unbond the generator neutral and ground when needed if that step is easy to do and included in the instructions.

Even if it is inconvenient like you need to unbond it for household use and rebond it for stand alone use out in the field.

My suggestion to leave it bonded is for a situation when the unbonding process is complicated and where one false move could damage the generator.
 
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Old 08-14-20, 05:23 PM
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Me...... personally.... I only un-bond a generator if it has a GFI breaker on it.
All my Hondas are bonded and are used for direct connection as well as out in the field.
 
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Old 08-14-20, 06:56 PM
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Possible simple solution for mixed use. Unbond generator, assuming it's not difficult. Use as is for backfeeding panel. Get a male plug and run a jumper wire connecting neutral and ground prongs of plug. Stick the plug in one of the outlets when using generator in the field. That should do it, right?

Label plug, put it on a lanyard and attach to genny's frame so it doesn't wander off.
 
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Old 08-15-20, 09:50 AM
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^ Nevermind above post. I see that @pattenp made this suggestion all the way back in the 2nd post in this thread. I'm just now wrapping my head around the whole neutral bonded vs floating neutral generator concept!
 
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Old 08-16-20, 09:58 AM
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Looking at that generator, that bonding is not intended to be removed.
If we do not look at rules, but try to analyze the risks of having bonding in Generator and in main panel.
You get e a considerably larger power carrying capacity with both ground and neutral in paralell so if one them fails,the other one will most likely do the job. When everything is OK the risk of voltage to ground between generator frame, and real ground is small. Does any risks be larger? Yes, if someone is working on the system and separates neutral and ground it may be a risk of electrocution, but not larger than when you do the same with regular power. All systems in other houses, and on the transformer the N and gnd is connected.

I may of course be something I do not understand here, but this seems to end up as what the Aussies called MEN (multiple Earthed Neutral).


Regards from Norway
dsk
 
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Old 08-17-20, 07:13 AM
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Is there something wrong with doing it right when connecting a generator to a household service when not switching the neutral?
 
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Old 08-17-20, 08:00 AM
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Old 08-17-20, 08:45 AM
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It is always best to do it right, and as patmurphey said earlier: "Don't buy a generator that includes the nonsense that you would void the warranty if you connected it to a residence in a manner that complies with code. Don't buy one for residential use that makes removing the bond difficult. Write to the manufacturer and tell them why. It might be interesting to use a "contact us" button on their web site to engage in a dialog.

Portable generators should include a bonding switch with clearly stated caution, bonded for separately derived use as at a contractor site or just use of extension cords, and unbonded for typical residential connection to home."

My point is that the risk by doing it "wrong" seems to be small in this case.

My only experience with US systems are limited to 277/480V systems in one single place.
By pointing out my analyzes of the risk, a good answer here might learn me more about electric systems.

 
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