# Generator: Floating the neutral



## AdamBNYC (Aug 15, 2010)

Hello Pro's,

As part of my generator project, I have started reading alot about floating the neutral from the generator. I'd like to make sure I understand this correctly and I have a few questions. Once again, thanks in advance

Quick review of my proposed solution
30 amp 220 breaker with interlock kit in the load panel
connected via 10/3 to a reliance inlet box 14-30 twist
10/3 "extension" cable from Generator to inlet box

From my understanding the generator I am to soon receive has a bonded neutral to the frame (briggs elite 7000). The problem being is that one should not have a bonded neutral to ground in two spot. in my case, one being in the load center and one being in the generator.

From what I am told I can expect is that there is a wire in the generator on one of the 120v outlets that bridges the ground to neutral. It is my understanding that I should remove this wire when backfeeding into the load center and put this wire back if i ever use it stand alone (which will be never)

Does this sound correct so far?
Do I need to ground the generator after this step, or will the generator use my in-house ground?
If I give a 120v extension from the generator to my neighbor to power his fridge, will it be a problem with the floating neutral?

Im sure I will think of some other questions. Thanks in advance!


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## Billy_Bob (Sep 11, 2008)

Lots of reading on that subject! Search google.com for the words...

separately derived system generator

non-separately derived system generator

neutral switching transfer switch

osha generator gfci

osha generator grounding


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## Julius793 (Dec 13, 2011)

No you leave the generator exactly as it was manufactured hook it up when you need and go on with life.


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## AllanJ (Nov 24, 2007)

The typical home has the main panel neutral and ground bonded.

Check the generator instructions on how to unbond neutral and ground within. If you don't find that information, then skip that step, go on to the next step, and connect up the generator.


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## Julius793 (Dec 13, 2011)

AllanJ said:


> The typical home has the main panel neutral and ground bonded.
> 
> Check the generator instructions on how to unbond neutral and ground within. If you don't find that information, then skip that step, go on to the next step, and connect up the generator.


NO you do NOT unbound neural and ground by the generator!


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## Auger01 (Sep 13, 2011)

AdamBNYC said:


> Does this sound correct so far?


Yes. That is the right way to do it.



AdamBNYC said:


> Do I need to ground the generator after this step, or will the generator use my in-house ground?


No. The generator is connected to the house ground via the power cord.



AdamBNYC said:


> If I give a 120v extension from the generator to my neighbor to power his fridge, will it be a problem with the floating neutral?


If the generator is hooked up to your house, then it is fine to use an extension cord to the neighbor. Remember, the neutral and ground of the generator are still connected at the house panel, just be sure not to unplug it from the house.


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## Julius793 (Dec 13, 2011)

Ok now that I got home.... To prove my point that the frame of the generator MUST be bonded to neutral look at 250.34


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## stickboy1375 (Apr 28, 2012)

Julius793 said:


> NO you do NOT unbound neural and ground by the generator!


Technically, it is the correct way to do a generator installation. You cannot bond the neural and ground in more than one location, so you would either need a transfer switch that disconnects the neutral connection, or you would have to do it at the generator manually.

Personally, since the death rate is zero for not disconnecting the neutral/ground bond at the generator, I recommend leaving it alone, and moving on.


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## AdamBNYC (Aug 15, 2010)

Julius793 said:


> Ok now that I got home.... To prove my point that the frame of the generator MUST be bonded to neutral look at 250.34


250.30 is contrary to what your saying




250.30 - CAUTION: The neutral-to-ground connection for a separately derived system cannot be made at more than one location. To do so would create multiple neutral-to-ground connections, which produces multiple neutral current return paths to the grounded (neutral) conductor of power supply, which can create a fire, shock hazard as well as power quality problems from electromagnetic interference. See 250.6 and 250.142(A).


250.34 Generators-Portable and Vehicle-Mounted
(A) Portable Generators. The frame of a portable generator is not be required to be grounded to the earth if:
(1) The generator only supplies equipment or cord-and-plug-connected equipment through receptacles mounted on the generator, or both, and
(2) The metal parts of generator and the grounding terminals of the receptacles are bonded to the generator frame.

(B) Vehicle-Mounted Generators. The frame of a portable generator is not required to be grounded to the earth if:
(1) The generator frame is bonded to the vehicle frame.
(2) The generator only supplies equipment or cord-and-plug-connected equipment through receptacles mounted on the generator, or both, and
(3) The metal parts of generator and the grounding terminals of the receptacles are bonded to the generator frame.



> FPN: Portable generators that supply fixed wiring systems must be grounded in accordance with 250.30 for separately derived systems if they supply a transfer switch that switches the neutral.


I am not using a transfer panel, I'm using an interlock directly back to the load center.


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## Auger01 (Sep 13, 2011)

Julius793 said:


> Ok now that I got home.... To prove my point that the frame of the generator MUST be bonded to neutral look at 250.34


 
250.34 refers to the frame being connected to a *grounding elecrode. *

The way the op is connecting it, the generator frame *is* connected to the grounding electrode. 

Care to try again? :whistling2:


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## AdamBNYC (Aug 15, 2010)

So while I dont think it will "kill" me if I dont disconnect the Neutral from the Generator, the NEC states that it could cause "Power Quality Problems"

So as long as there isnt anything wrong with disconnecting the neutral from the generator, it seems I might get cleaner power this way. Thats a big thing considering how dirty power from a generator could be.


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## stickboy1375 (Apr 28, 2012)

AdamBNYC said:


> So while I dont think it will "kill" me if I dont disconnect the Neutral from the Generator, the NEC states that it could cause "Power Quality Problems"
> 
> So as long as there isnt anything wrong with disconnecting the neutral from the generator, it seems I might get cleaner power this way. Thats a big thing considering how dirty power from a generator could be.


No, and not even sure how you came to that conclusion?


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## speedster1 (May 13, 2009)

In leau of starting a seperate thread is there any issues with me using an interlock kit and backfeeding a 200 amp subpanel through a 30amp double pole breaker via an outside reliant box and 4 prong nema cord? I have an 8000w generac genset and my subpanel's neutral and ground are not bonded.


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## TTW (Nov 23, 2012)

speedster1 said:


> In leau of starting a seperate thread is there any issues with me using an interlock kit and backfeeding a 200 amp subpanel through a 30amp double pole breaker via an outside reliant box and 4 prong nema cord? I have an 8000w generac genset and my subpanel's neutral and ground are not bonded.


An interlock is designed to prevent you from backfeeding your main panel, and possibly the transformer on the power pole, and zapping the lineman working to restore power.

Oh maybe I read it wrong. Wait, you have a 200 amp sub panel? What is your main service? That's one heck of a sub panel...


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## speedster1 (May 13, 2009)

Well its actually my main circuit breaker but since I have a 200amp disconnect at my meter outside this box is technically considered a subpanel and the neutral and ground are unbonded.

I just wondered if floating the neutral came into play in my case since I'm backfeeding a breaker box with an unbonded neutral/ground


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## stickboy1375 (Apr 28, 2012)

speedster1 said:


> Well its actually my main circuit breaker but since I have a 200amp disconnect at my meter outside this box is technically considered a subpanel and the neutral and ground are unbonded.
> 
> I just wondered if floating the neutral came into play in my case since I'm backfeeding a breaker box with an unbonded neutral/ground


But they are still bonded back at the service disconnect... 


This is just a random rant, not directed at anyone directly....

It's funny how people read a few threads on the internet, but really have no idea about grounding and bonding, personally, hire an electrician to do your generator. Some of these installations are just not DIY projects.


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## Billy_Bob (Sep 11, 2008)

stickboy1375 said:


> ...It's funny how people read a few threads on the internet, but really have no idea about grounding and bonding, personally, hire an electrician to do your generator. Some of these installations are just not DIY projects.


I agree. Of all things electrical, connecting a generator to a home's wiring is a *very* advanced electrical project!

Some of the issues surrounding this leave even seasoned electricians scratching their heads!

Part of the problem is with generators designed to be used as portable generators on a construction site which have integral GFCIs. There are all sorts of OSHA and other rules all about that which conflict with connection of a generator to a house.

And the ultimate mind boggler is a portable generator which will be used half and half - part time connected to a home's wiring and part time as a construction site portable generator.

Then to add to all this confusion, some generator manufacturers put out technical bulletins like the following, but other generator manufactures DO NOT!...
http://www.gen-tran.com/assets/pdfs/HondaGeneratorServiceBulletin20.pdf

Bottom line: Generators are not "plug and play"


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## speedster1 (May 13, 2009)

stickboy1375 said:


> But they are still bonded back at the service disconnect...


In my case considering the 200 amp breaker in the "subpanel" is in the off position the neutral connection back to the service disconnect is broken at that point. So I believe the only bonding at that point is at my generator. 

I admit I'm not that knowledgable about electrical systems. I'm just trying to understand and learn some things.


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## Techy (Mar 16, 2011)

speedster1 said:


> In my case considering the 200 amp breaker in the "subpanel" is in the off position the neutral connection back to the service disconnect is broken at that point. So I believe the only bonding at that point is at my generator.
> 
> I admit I'm not that knowledgable about electrical systems. I'm just trying to understand and learn some things.




Negative, main only opens the hot (ungrounded) conductors. Neutral(grounded) and ground are not broken.


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## Billy_Bob (Sep 11, 2008)

speedster1 said:


> ...I admit I'm not that knowledgable about electrical systems. I'm just trying to understand and learn some things.


This is one of those things which has a *long* list of things to learn about! And when I make a list for something, like to go shopping, I always leave something off! 

Anyway I will try to list the various issues / things to learn about...

First of all electrical codes/rules are not "wiring instructions to get it to work", rather many of those rules are for safety in case "something happens". An electrical malfunction, an unauthorized person is able to come along and flip a switch which causes a dangerous situation, future home owners might be placed in danger by plugging something in, etc.

And those rules have been created because of terrible things which have happened in the past. People have been electrocuted, homes have burned to the ground, etc.

So one thing to learn about is what all can go wrong...

-A wire becomes disconnected between the generator and the home's electric panel. What can happen if that wire is one of the hot wires? If a neutral wire? If a ground wire? (Or a combination of the above?)

If the neutral wire came loose between the house and the generator, is the generator wired to the house in a manner which could cause the metal frame of the generator to become energized? Perhaps a small child or animal touching the generator could become electrocuted?

-The power from the electric company goes out, you are not home. Other people in the house go to the electric panel and start flipping breakers / switches. Is there a possible way they could cause electricity from the generator to be sent out "backwards" on the electric company's lines? Might someone think a down power line near your house was not live, but in fact it is live (powered by your generator)?

-Ground loops and electrical "noise" caused by multiple grounds.

-Read about how a "main" electric panel has a neutral/ground bond, but a subpanel does not. Why is this?

-A generator with an integral GFCI and neutral/ground bonds on either side of that GFCI - The GFCI keeps tripping. Why is that?

-A generator can power 50 amps, then is connected to a house electric panel and in turn to a 75 amp load (things turned on in the house). How is the generator protected? Could someone other than you do this accidentally when you are not home?

-Could a generator be connected to a home's wiring system so that the 3rd grounding plug on outlets no longer functioned properly? Could this cause metal cases on appliances to become "hot" and electrocute someone touching them if there was a loose connection on one of the wires to the generator?

That is all I can think of. Basically overcurrent protection which protects the wires from becoming temperature hot and causing a fire. Protection from electrocution if any particular wire loses its connection or otherwise. Protection to keep the generator's electricity from going out on the electric company's power lines no matter who is flipping breakers or operating the generator. And problems with "ground loops".


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## speedster1 (May 13, 2009)

Techy said:


> Negative, main only opens the hot (ungrounded) conductors. Neutral(grounded) and ground are not broken.


You are correct. Your post got me thinking about how the panel is wired. The two hot lugs are disconnected from the mains but the neutral and ground at direct wired. 

I'm glad I read stuff like this because it helps me visualize things and in a small way helps me get a basic understanding of how things work.


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## speedster1 (May 13, 2009)

Billy_Bob said:


> This is one of those things which has a *long* list of things to learn about! And when I make a list for something, like to go shopping, I always leave something off!
> 
> Anyway I will try to list the various issues / things to learn about...
> 
> ...


Thanks for the listing some of the things to think about with this kind of setup.


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## Oso954 (Jun 23, 2012)

They do make generator transfer switches that will switch the neutral.
Properly installed, they will resolve a lot of the "issues" that seem to be troubling you.

http://www.reliancecontrols.com/Products.aspx?pl=x_series&c=&f=


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## stickboy1375 (Apr 28, 2012)

Oso954 said:


> They do make generator transfer switches that will switch the neutral.
> Properly installed, they will resolve a lot of the "issues" that seem to be troubling you.
> 
> http://www.reliancecontrols.com/Products.aspx?pl=x_series&c=&f=


They also make portable generators with a switch to isolate the neutral bond at the generator.


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## speedster1 (May 13, 2009)

So is the rule is that if you are backfeeding a load center the generator neutral and ground should not be bonded because the load center neutral is already bonded? On the flipside if you are using the generator to power a tablesaw or a standalone product the generator neutral should be bonded?


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## stickboy1375 (Apr 28, 2012)

speedster1 said:


> So is the rule is that if you are backfeeding a load center the generator neutral and ground should not be bonded because the load center neutral is already bonded? On the flipside if you are using the generator to power a tablesaw or a standalone product the generator neutral should be bonded?


The problem arises that you can only have one neutral ground bond, and that occurs at the main service disconnect, a portable generator also contains a neutral ground bond, this is where the violation occurs, when you use a generator as a portable unit, it is imperative that the generator contain a neutral ground bond, for the simple reason that without this bond, the grounding conductor would be useless and any appliance that had a ground fault would not trip the OCPD...


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## AllanJ (Nov 24, 2007)

The overcurrent protection device (fuse or circuit breaker) is in the hot current path, which means that improper grounding will not prevent blowing/tripping in case of an overload (overcurrent).

When a generator is used out in the field (not connected to a building electrical system) neutral and ground should be bounded within. A generator will perform perfectly well with ground and neutral not bonded within when connected to a building system with neutral and ground bonded in the panel.

The difficulty arises when it is difficult to unbond neutral and ground inside the generator. In this case I recommend leaving it bonded rather than dismantling the generator. Nothing bad will happen considering that the destination of the generator return current is the generator, not the earth.

Caution: If neutral of the panel is disconnected from neutral of the utility service as part of neutral/ground unbonding, this should not be a separate manual step, and should be omitted unless it can be part of the same maneuver as disconnecting the hot lines. Operating the system for any length of time under utility power with the utility NEUTRAL not bonded to the system NEUTRAL is very dangerous.


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## JACK HOTTEL (Dec 15, 2011)

Neutral and ground are still connected at your outside disconnect.
Jack Hottel


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## speedster1 (May 13, 2009)

I took the panel and cover off of my generac and its not clear to me where the bonding wire is.


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## stickboy1375 (Apr 28, 2012)

Personally, I would leave it alone, My own personal portable generator still has the ground/neutral bond at the generator.


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## oncall (Dec 8, 2012)

Hi I'm new here. But I'm interested in the netural/bond issue. I'm not an electrican but do have knowledge and some experience on wiring of homes and circuits for things such as HVAC and som eletronic equipment.

If it's alright I like to ask a question. From what I'm seeing if you use a generator for home you have a few options:

1. you can run the generator and just use the 120V outlets on the generator unit. And not worry about the netural/bond on the generator.
2. You can hook up to your house panel by means of a Transfer switch with a switching netural if you have the netural/bond on the generator. 
3. *Or* you can make the generator a floating netural and hook up with an transfer switch without a switching netural to house panel box.(if codes allow).
4. If you do not have the Netural/bond on the generator then it is not a issue. and you should not hook up to the house panel with a transfer switch with switching netural. You would need to hook up the netural from the generator being connected with the house netural bar.

Am I on the right path here?

Again I'm new here and just trying to understand, thanks in advance


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