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Old 12-07-2012, 06:07 AM   #16
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Generator: Floating the neutral


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Originally Posted by speedster1 View Post
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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Old 12-07-2012, 11:13 AM   #17
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Generator: Floating the neutral


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...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/...Bulletin20.pdf

Bottom line: Generators are not "plug and play"
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Old 12-07-2012, 12:05 PM   #18
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Generator: Floating the neutral


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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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Old 12-07-2012, 12:11 PM   #19
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Generator: Floating the neutral


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Originally Posted by speedster1 View Post
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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Old 12-07-2012, 01:19 PM   #20
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Generator: Floating the neutral


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...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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Old 12-07-2012, 01:52 PM   #21
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Generator: Floating the neutral


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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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Old 12-07-2012, 01:54 PM   #22
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Generator: Floating the neutral


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Originally Posted by Billy_Bob View Post
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".
Thanks for the listing some of the things to think about with this kind of setup.
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Old 12-07-2012, 04:07 PM   #23
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Generator: Floating the neutral


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/Prod...x_series&c=&f=
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Old 12-07-2012, 04:10 PM   #24
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Generator: Floating the neutral


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Originally Posted by Oso954 View Post
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/Prod...x_series&c=&f=
They also make portable generators with a switch to isolate the neutral bond at the generator.
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Old 12-07-2012, 04:22 PM   #25
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Generator: Floating the neutral


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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Old 12-07-2012, 04:53 PM   #26
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Generator: Floating the neutral


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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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Old 12-07-2012, 06:35 PM   #27
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Generator: Floating the neutral


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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Last edited by AllanJ; 12-07-2012 at 06:52 PM.
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Old 12-07-2012, 10:04 PM   #28
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Generator: Floating the neutral


Neutral and ground are still connected at your outside disconnect.
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Old 12-08-2012, 11:35 AM   #29
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Generator: Floating the neutral


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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Old 12-08-2012, 11:42 AM   #30
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Generator: Floating the neutral


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

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