Generator Neutral & Ground Question

Got a portable generator recently. Would like to eventually wire in a tran sfer switch for my house and run a few selected rooms. My generator has th e neutral bonded to the frame. You are also supposed to ground the generat or frame. Seeing as it's portable they tell you to pound a grounding rod i nto the ground and wire your ground lug on the frame to that.
I'm going to jack it into my house, so I think I can just use the same grou nd that runs through my house. Every 120V outlet will have a ground connec tion so getting to this ground be easy with a custom cable or modified exte nsion cord.
If I ground my generator to the same ground that the power company provided to my house, I believe I can use a standard 2-Pole transfer switch that do es not have the special third pole to switch my house circuits over to my g enerator neutral....basic transfer switches just connect the neutrals toget her (house and generator). So that's what I want to do. House Neutral is c onnected to Generator Neutral. House Neutral is also bonded to House Groun d (by the power company, not me) and Generator Ground (frame of generator) is connected to house ground (this one by me). I think this avoids all the problems with ground loops and GFIC outlets on the generator tripping....
I can't see why this doesn't work BUT there are articles all over the inter net describing this problem. I've not seen this simple solution mentioned. It's always you need to buy a special and more expensive transfer switch or you need to modify your generator and remove the ground-neutral bond. I t seems to be a source of great confusion.
Can anyone see a problem with method I'm describing?
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On 09/10/2017 11:39 AM, snipped-for-privacy@gmail.com wrote:

According to all codes I've ever seen the only place where neutral and ground may share the same bus is in the distribution panel itself.
If not, there could potentially be a ground loop which could negate the safety of any GFC outlets.
Though may never run into a problem , I'd err on the side of safety and wire your generator according to code.
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+1
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On Sunday, September 10, 2017 at 1:03:26 PM UTC-4, philo wrote:

transfer switch for my house and run a few selected rooms. My generator ha s the neutral bonded to the frame. You are also supposed to ground the gen erator frame. Seeing as it's portable they tell you to pound a grounding r od into the ground and wire your ground lug on the frame to that.

ground that runs through my house. Every 120V outlet will have a ground co nnection so getting to this ground be easy with a custom cable or modified extension cord.

ided to my house, I believe I can use a standard 2-Pole transfer switch tha t does not have the special third pole to switch my house circuits over to my generator neutral....basic transfer switches just connect the neutrals t ogether (house and generator). So that's what I want to do. House Neutral is connected to Generator Neutral. House Neutral is also bonded to House G round (by the power company, not me) and Generator Ground (frame of generat or) is connected to house ground (this one by me). I think this avoids all the problems with ground loops and GFIC outlets on the generator tripping. ...

nternet describing this problem. I've not seen this simple solution mentio ned. It's always you need to buy a special and more expensive transfer swi tch or you need to modify your generator and remove the ground-neutral bond . It seems to be a source of great confusion.

They don't ever share the same bus, they are bonded together.


I can see issues like that causing false tripping, but I'm having a hard time visualizing a scenario where it causes a GFCI to fail to work.
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On 09/10/2017 12:29 PM, trader_4 wrote:

My house was recently re-wired and it passed the electrical inspection. In the breaker box the grounds and neutrals share the same bus.
Don't know exactly what you mean.

I also cannot see how a GFCI would fail to work but I'd still follow the electrical code to the letter.
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On Sunday, September 10, 2017 at 4:29:52 PM UTC-4, philo wrote:

a transfer switch for my house and run a few selected rooms. My generator has the neutral bonded to the frame. You are also supposed to ground the g enerator frame. Seeing as it's portable they tell you to pound a grounding rod into the ground and wire your ground lug on the frame to that.

e ground that runs through my house. Every 120V outlet will have a ground connection so getting to this ground be easy with a custom cable or modifie d extension cord.

ovided to my house, I believe I can use a standard 2-Pole transfer switch t hat does not have the special third pole to switch my house circuits over t o my generator neutral....basic transfer switches just connect the neutrals together (house and generator). So that's what I want to do. House Neutra l is connected to Generator Neutral. House Neutral is also bonded to House Ground (by the power company, not me) and Generator Ground (frame of gener ator) is connected to house ground (this one by me). I think this avoids a ll the problems with ground loops and GFIC outlets on the generator trippin g....

internet describing this problem. I've not seen this simple solution ment ioned. It's always you need to buy a special and more expensive transfer s witch or you need to modify your generator and remove the ground-neutral bo nd. It seems to be a source of great confusion.

I was reading "bus" but thinking conductor. What I meant was that the equipment grounds should not be carrying current, only the neutral should. At the bus level you're right, assuming it's the main panel and that is where the neutral and the grounding electrode conductor are tied together, then it's OK to have the grounds and neutral on the same bus and if they are on separate buses, then the two buses are bonded together. Sorry for the confusion.
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On 09/10/2017 06:15 PM, trader_4 wrote:

Doesn't take much to confuse me.
Think we are both on the same page now.
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snipped-for-privacy@gmail.com wrote:

CW-
You do not need to switch the generator ground, but you do need to disconnect it from the frame when connecting to your house system.
Whether you can do it or not depends a lot on the generator. Some make it nearly impossible to separate ground from neutral. Others have a short green jumper wire from one outlet's ground to the frame.
I get around the problem by not connecting into the house system. I run a heavy extension cord from the generator into the house. Only a few lights and appliances get plugged in. In an emergency, I figure lights, a microwave, a refrigerator and a coffee maker are all that I need.
My refrigerator keeps ice frozen for at least 8 hours, so I do not run the generator while asleep. That saves gas and the generator is less likely to be stolen!
Fred
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On Sunday, September 10, 2017 at 1:57:00 PM UTC-4, Fred McKenzie wrote:


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What is the benefit to disconnecting the frame from the ground at the gener ator? I can see one big negative, the frame is now ungrounded and if a hot wire in the generator comes in contact with it the frame is energized. Tou ch it and the return current path is through you, through earth, back to th e house grounding electrode. Am I missing something?
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Yeah definitely want to ground the generator frame no matter what. I was t hinking I could ground the frame through a household ground wire. In a str ange way, if I use a standard 2-Pole transfer switch, just by connecting th e generator 220 plug to the transfer switch I have connected the generator frame and my generator neutral & ground to my household ground distribution . Assuming I modify nothing at all, that's what would happen.
So in your example the hot wire comes loose in the generator hits the frame and is shorted to the ground connection in my house. Similar to what happ ens when a hot wire comes loose in a lamp with a grounded metal frame plugg ed into a wall outlet.
I'm struggling to see why that doesn't work but I'm probably under-thinking this. The only thing I've been noodling is ground(s) potential difference s. So the ground I'm standing on beside the generator (generator is on pla stic wheels), could be at a different potential from the ground wherever my house transformer is grounded. But I'd expect that problem to be minor ot herwise you'd have this issue on outdoor lights and outlets.
Just trying to understand it all a little more.
Regardless, after more thought, I'm just going to install it all the right way. I'll ground the generator frame locally at the generator and install a neutral-switch type transfer switch. Generac sells a neutral switch kit for their transfer switches and reliance controls has the X-Series models w hich are designed for this very problem.
I'm just thinking through it all. Right now I just have a generator :)
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On Sunday, September 10, 2017 at 4:10:35 PM UTC-4, snipped-for-privacy@gmail.com wrote:

thinking I could ground the frame through a household ground wire. In a s trange way, if I use a standard 2-Pole transfer switch, just by connecting the generator 220 plug to the transfer switch I have connected the generato r frame and my generator neutral & ground to my household ground distributi on. >Assuming I modify nothing at all, that's what would happen.
See my other reply I just made to my own post. I agree, you're on the right track. What you stated above is all good and code compliant, as long as *the neutral is not connected to ground at the generator*. Doing some googling, it looks like some generators they are, some are not, some have a jumper.

me and is shorted to the ground connection in my house. Similar to what ha ppens when a hot wire comes loose in a lamp with a grounded metal frame plu gged into a wall outlet.
Agree.

ng this. The only thing I've been noodling is ground(s) potential differen ces. So the ground I'm standing on beside the generator (generator is on p lastic wheels), could be at a different potential from the ground wherever my house transformer is grounded. But I'd expect that problem to be minor otherwise you'd have this issue on outdoor lights and outlets.

See my discussion about the issue of whether the neutral is connected to ground at the generator in the other post. If it's not, then what you're describing is fine, code compliant. But if the generator has the neutral connected to ground, you then have 3 paths for neutral current to flow between the house and generator:
1 - neutral wire in the cord, which you want
2 - ground wire in the cord, which is bad and a code violation
3 - through the earth ground at the house, through earth, back to generator
That is the issue, whether the neutral is connected at the generator or not. If it is, then you have to treat it as a separately derived system and switch the neutral at the transfer switch, which complicates things. And then the generator is the place where the system neutral and earth ground are tied together and you need an appropriate earthing system that meets code, not a 2 ft ground rod that some Chinese generator manual talks about. Which is why I'd avoid that choice.

t way. I'll ground the generator frame locally at the generator and instal l a neutral-switch type transfer switch. Generac sells a neutral switch ki t for their transfer switches and reliance controls has the X-Series models which are designed for this very problem.

Either way is right, the issue is whether that neutral is grounded at the generator or not. I'd much prefer the first method, using the house earthing system. It's likely a good earthing system, why install another one and one that you have to remember to connect the generator to? It's more than just using the typical one cord, something someone else could easily overlook, forget, etc.
And if you have a panel that you can get an Interlockit kit for, you can do it for the cost of that, a breaker, and an inlet. I'd bet that's a lot less than a transfer switch.
Hope that helps.
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On Sunday, September 10, 2017 at 7:57:12 PM UTC-4, trader_4 wrote:
e:

as thinking I could ground the frame through a household ground wire. In a strange way, if I use a standard 2-Pole transfer switch, just by connectin g the generator 220 plug to the transfer switch I have connected the genera tor frame and my generator neutral & ground to my household ground distribu tion. >Assuming I modify nothing at all, that's what would happen.

,

rame and is shorted to the ground connection in my house. Similar to what happens when a hot wire comes loose in a lamp with a grounded metal frame p lugged into a wall outlet.

king this. The only thing I've been noodling is ground(s) potential differ ences. So the ground I'm standing on beside the generator (generator is on plastic wheels), could be at a different potential from the ground whereve r my house transformer is grounded. But I'd expect that problem to be mino r otherwise you'd have this issue on outdoor lights and outlets.

or

ght way. I'll ground the generator frame locally at the generator and inst all a neutral-switch type transfer switch. Generac sells a neutral switch kit for their transfer switches and reliance controls has the X-Series mode ls which are designed for this very problem.

I had the same problem. If the neutral and ground are tied together in your panel (they are) and th ey are also tied together in the generator, then when you feed the house, s ome of the load current will flow through the grond wire and trip the GFI i n the generator.
The solution I used was to UNBOND the the neutral and ground in the generat or. Keep the ground connected to the frame for safety, but disconnect it f rom the neutral. This way, the frame remains safely grounded, and no load current can try to pass though the ground wire.
So the possible danger with that is due to static electricity the two load wires can build up a voltage above ground and can arc over the insulation. For this reason I connected the ground to the neutral through a MOV instea d of a direct bond. This prevents any high voltage from building up on the wingdings.
This is a pretty complicated issue actually.
mark
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On Sunday, September 10, 2017 at 9:40:40 PM UTC-4, snipped-for-privacy@yahoo.com wrote:

ote:

was thinking I could ground the frame through a household ground wire. In a strange way, if I use a standard 2-Pole transfer switch, just by connect ing the generator 220 plug to the transfer switch I have connected the gene rator frame and my generator neutral & ground to my household ground distri bution. >Assuming I modify nothing at all, that's what would happen.

ot,

frame and is shorted to the ground connection in my house. Similar to wha t happens when a hot wire comes loose in a lamp with a grounded metal frame plugged into a wall outlet.

inking this. The only thing I've been noodling is ground(s) potential diff erences. So the ground I'm standing on beside the generator (generator is on plastic wheels), could be at a different potential from the ground where ver my house transformer is grounded. But I'd expect that problem to be mi nor otherwise you'd have this issue on outdoor lights and outlets.

ator

or

right way. I'll ground the generator frame locally at the generator and in stall a neutral-switch type transfer switch. Generac sells a neutral switc h kit for their transfer switches and reliance controls has the X-Series mo dels which are designed for this very problem.

:)

they are also tied together in the generator, then when you feed the house, some of the load current will flow through the grond wire and trip the GFI in the generator.

ator. Keep the ground connected to the frame for safety, but disconnect it from the neutral. This way, the frame remains safely grounded, and no loa d current can try to pass though the ground wire.

d wires can build up a voltage above ground and can arc over the insulation .
I don't see how that can happen. The two load wires, the windings, are still tied to earth ground via the neutral to earth connection at the house panel. It would be like attempting to put static charge on the positive end of a battery while the negative end is earthed.
You have anything that documents this, shows it happening?
For this reason I connected the ground to the neutral through a MOV inste ad of a direct bond. This prevents any high voltage from building up on the wingdings.

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On Sunday, September 10, 2017 at 9:50:41 PM UTC-4, trader_4 wrote:
e:

wrote:

I was thinking I could ground the frame through a household ground wire. In a strange way, if I use a standard 2-Pole transfer switch, just by conne cting the generator 220 plug to the transfer switch I have connected the ge nerator frame and my generator neutral & ground to my household ground dist ribution. >Assuming I modify nothing at all, that's what would happen.

e

not,

he frame and is shorted to the ground connection in my house. Similar to w hat happens when a hot wire comes loose in a lamp with a grounded metal fra me plugged into a wall outlet.

thinking this. The only thing I've been noodling is ground(s) potential di fferences. So the ground I'm standing on beside the generator (generator i s on plastic wheels), could be at a different potential from the ground whe rever my house transformer is grounded. But I'd expect that problem to be minor otherwise you'd have this issue on outdoor lights and outlets.

erator

or

es

ng

ator

e right way. I'll ground the generator frame locally at the generator and install a neutral-switch type transfer switch. Generac sells a neutral swi tch kit for their transfer switches and reliance controls has the X-Series models which are designed for this very problem.

r :)

d they are also tied together in the generator, then when you feed the hous e, some of the load current will flow through the grond wire and trip the G FI in the generator.

erator. Keep the ground connected to the frame for safety, but disconnect it from the neutral. This way, the frame remains safely grounded, and no l oad current can try to pass though the ground wire.

oad wires can build up a voltage above ground and can arc over the insulati on.

yes i agree with you, when the generator is connected to a house with the g round a neutral bonded, static electricity cannot happen.
but if the modified generator is used to power an isolated load like it was intended where nothing is bonded, then it could happen.
I guess another solution would be to use add a switch to the generator, unb ond when feeding a house, bond when feeding an isolated load.
mark
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On Sun, 10 Sep 2017 18:56:24 -0700 (PDT), snipped-for-privacy@yahoo.com wrote:

Unbond the generator for connection to the house. To re-bond for portable use, simply make a bobd jumper" - a 3 wire plug with the white and green jumpered that you plug into one of the outlets for portable use (or just put a switch in the bonding wire)
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On Sun, 10 Sep 2017 22:25:21 -0400, snipped-for-privacy@snyder.on.ca wrote:

The only other legal alternative is to use a 3 pole transfer switch (separately derived system)
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On Sunday, September 10, 2017 at 9:56:32 PM UTC-4, snipped-for-privacy@yahoo.com wrote:

ote:

m wrote:

. I was thinking I could ground the frame through a household ground wire. In a strange way, if I use a standard 2-Pole transfer switch, just by con necting the generator 220 plug to the transfer switch I have connected the generator frame and my generator neutral & ground to my household ground di stribution. >Assuming I modify nothing at all, that's what would happen.

the

*.

re not,

the frame and is shorted to the ground connection in my house. Similar to what happens when a hot wire comes loose in a lamp with a grounded metal f rame plugged into a wall outlet.

r-thinking this. The only thing I've been noodling is ground(s) potential differences. So the ground I'm standing on beside the generator (generator is on plastic wheels), could be at a different potential from the ground w herever my house transformer is grounded. But I'd expect that problem to b e minor otherwise you'd have this issue on outdoor lights and outlets.

ed

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the right way. I'll ground the generator frame locally at the generator an d install a neutral-switch type transfer switch. Generac sells a neutral s witch kit for their transfer switches and reliance controls has the X-Serie s models which are designed for this very problem.

tor :)

at

and they are also tied together in the generator, then when you feed the ho use, some of the load current will flow through the grond wire and trip the GFI in the generator.

enerator. Keep the ground connected to the frame for safety, but disconnec t it from the neutral. This way, the frame remains safely grounded, and no load current can try to pass though the ground wire.

load wires can build up a voltage above ground and can arc over the insula tion.

ground a neutral bonded, static electricity cannot happen.
After I posted that I thought about it some more and realized the same thing, ie that the generator isn't always connected to the house or even to anything at times, so the windings are effectively isolated.

as intended where nothing is bonded, then it could happen.

nbond when feeding a house, bond when feeding an isolated load.

+1
That would allow it to be used either way. Of course then the problem becomes people remembering to put the switch in the right position. I'd try to make the switch very obvious, big labeling, etc.
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trader, looking at interlockit now. thank you for recommending. that is a very go od option. may have same issue though with generator and neutral-frame bon ding right? i haven't had time to look at it closely yet, but seems like i would...if so, that method is worth me getting in and unbonding the neutra l line from the frame. i didn't want to mess with that but now thinking i might after realizing the flexibility i will get from the interlockit.
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On Tuesday, September 12, 2017 at 9:16:06 PM UTC-4, snipped-for-privacy@gmail.com wrote :

good option. may have same issue though with generator and neutral-frame b onding right?
Yes, to be code compliant, the neutral can't be connected to ground at the generator.
i haven't had time to look at it closely yet, but seems like i would...if so, that method is worth me getting in and unbonding the neutral line from the frame. i didn't want to mess with that but now thinking i might after realizing the flexibility i will get from the interlockit.
I've been thinking more about the whole issue of whether the neutral is connected at the generator or not. From what I see, the code issue is clear, that unless you switch the neutral at the transfer switch, then the neutral and ground cannot be connected at the generator. And if you do switch it, then you need a code compliant grounding system for the generator.
But the next question is, why is this and what are the possible safety implications if you didn't follow it. Note that I'm not saying you shouldn't follow the code, just trying to figure out what the possible scenarios are, what the code is trying to do, what goes wrong if you don't follow it. In other words, I was trying to figure out the physics and what the safety issues are.
If you have the neutral and ground connected at both the panel and the generator and use a 4 wire cord, then as I pointed out previously you have three paths for neutral current to flow between the house and generator:
1 - Via the neutral conductor
2 - Via the ground wire
3 - through the earth
Suppose instead you eliminate the ground wire in the cord. Then you have the neutral and ground connected at the house and at the generator. This is exactly how the power company service is wired in. I was trying to think what can go wrong here, what is inherently unsafe about wiring it that way. I can't think of a scenario where there is a safety problem beyond any that you already have with any portable generator. Maybe I'm missing something. Can anyone here see some safety issue I'm missing? And note I'm not saying you should wire it that way, it's a code violation. I'm just wondering why, ie what's the hazard that exists, what have I missed?
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I would not recommended cutting the ground (green) wire in the connecting cable. If there should be an open fault in the neutral wire, the frame of the generator will become energized via the load and this is obviously VERY dangerous.
there are 2 problems of having the neutral and ground bonded both at the house panel and at the generator.
1) if the generator has a GFI, it will trip. this is obviously an operational problem.
2) some load current will flow in the ground (green) wire. It will be shared by the neutral (white) wire and the ground (green) wire. This is a code issue but not an actual safety issue that I can see.
If there is no GFI involved, then there not really any safety issue. Just let it be bonded at both places. Its the GFI that makes it more complicated.
mark
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