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Old 06-30-2012, 10:26 AM   #31
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Wiring Generator to Backfeed Breakers - Neutral and Ground Wires?


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Originally Posted by stickboy1375 View Post
I know i stirred the pot on the issue, but the reality of it is, everyday generators are installed incorrectly by licensed contractors, and the like... Most people don't feel it is a real issue with the multiple N-G connection in a portable generator installation, well, because it still works in the end, and most likely will never be an issue. but still a violation none the less, and under the right circumstances could create a serious issue. Its one of those items that just gets installed either by lack of knowledge, or just the way we do it mentality...
So, in your opinion (one of several here, I realize), would you float the ground or not do this at all? I'm not of a mind to unbond N and G at the generator. (I haven't found for sure that they are bonded in the manuals yet, but it's a standard Generac portable unit, so I'd have to assume they are.)

And where does grounding the generator itself play into this? Do it or not?

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Old 06-30-2012, 11:13 AM   #32
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Wiring Generator to Backfeed Breakers - Neutral and Ground Wires?


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Originally Posted by tjnoff View Post
So, in your opinion (one of several here, I realize), would you float the ground or not do this at all? I'm not of a mind to unbond N and G at the generator. (I haven't found for sure that they are bonded in the manuals yet, but it's a standard Generac portable unit, so I'd have to assume they are.)

And where does grounding the generator itself play into this? Do it or not?
Personally, you can only undo the N-G bond at the generator if it is allowed by the manufacture, with that said, I would just install a 3 pole transfer switch and switch the neutral. Im betting 99% of portable generators contain a N-G bond, and with the growing number of manufactures supplying 30 amp GFCI protected receptacles, you will have no choice to deal with this scenario sooner or later.
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Old 06-30-2012, 11:29 AM   #33
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Wiring Generator to Backfeed Breakers - Neutral and Ground Wires?


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Originally Posted by stickboy1375 View Post
Personally, you can only undo the N-G bond at the generator if it is allowed by the manufacture, with that said, I would just install a 3 pole transfer switch and switch the neutral. Im betting 99% of portable generators contain a N-G bond, and with the growing number of manufactures supplying 30 amp GFCI protected receptacles, you will have no choice to deal with this scenario sooner or later.
So, either float the ground between the generator and the transfer switch or between the transfer switch and the power panel, but pass neutral all the way through to the neutral bar in the power panel, yes?

What about grounding the generator itself outside, as directed in the user's manual?
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Old 06-30-2012, 11:34 AM   #34
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Wiring Generator to Backfeed Breakers - Neutral and Ground Wires?


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Originally Posted by stickboy1375 View Post
Personally, you can only undo the N-G bond at the generator if it is allowed by the manufacture, with that said, I would just install a 3 pole transfer switch and switch the neutral. Im betting 99% of portable generators contain a N-G bond, and with the growing number of manufactures supplying 30 amp GFCI protected receptacles, you will have no choice to deal with this scenario sooner or later.
In this case, with the GFCI protected receptacle, I would consider using an ungrounded but otherwise ordinary extension cord to connect the generator up with. The generator could be put on a platform to reduce any hazards introduced by lack of an equipment grounding conductor.

The only difference between a generator with neutral floating within and the above hookup is that the body of the generator is at neutral potential instead of ground potential.
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Last edited by AllanJ; 06-30-2012 at 11:41 AM.
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Old 06-30-2012, 03:01 PM   #35
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Wiring Generator to Backfeed Breakers - Neutral and Ground Wires?


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In this case, with the GFCI protected receptacle, I would consider using an ungrounded but otherwise ordinary extension cord to connect the generator up with. The generator could be put on a platform to reduce any hazards introduced by lack of an equipment grounding conductor.

The only difference between a generator with neutral floating within and the above hookup is that the body of the generator is at neutral potential instead of ground potential.
The goal here is to power circuits in the house with the generator through the main power panel. I'm not sure how I'd do that with an extension cord.

I'm guessing that the issue with a floating ground is that it can have a current potential (vice true ground), and could therefore be a shock hazard... maybe even an explosion hazard on a gasoline generator.

Just removed the cover from my panel. Both bus bars (ground and neutral?) are physically tied together. If I'm right that those are G and N bus bars, they're both at ground potential.

While I understand electricity fairly well, I'm not sure why having ground and neutral bonded in two places (generator and bus bar) is an issue. They're both at the same potential.

I'm not saying it's not a problem - I apparently don't understand some things here - I'm just not seeing the issue.
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Old 06-30-2012, 03:14 PM   #36
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Wiring Generator to Backfeed Breakers - Neutral and Ground Wires?


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Originally Posted by tjnoff View Post
The goal here is to power circuits in the house with the generator through the main power panel. I'm not sure how I'd do that with an extension cord.

I'm guessing that the issue with a floating ground is that it can have a current potential (vice true ground), and could therefore be a shock hazard... maybe even an explosion hazard on a gasoline generator.

Just removed the cover from my panel. Both bus bars (ground and neutral?) are physically tied together. If I'm right that those are G and N bus bars, they're both at ground potential.

While I understand electricity fairly well, I'm not sure why having ground and neutral bonded in two places (generator and bus bar) is an issue. They're both at the same potential.

I'm not saying it's not a problem - I apparently don't understand some things here - I'm just not seeing the issue.
well what you've basically got now is a ground and a neutral connected together at two ends, some of the current naturally will travel along the ground wire, this will cause the gfci on the generator to trip.
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Old 06-30-2012, 03:38 PM   #37
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Wiring Generator to Backfeed Breakers - Neutral and Ground Wires?


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well what you've basically got now is a ground and a neutral connected together at two ends, some of the current naturally will travel along the ground wire, this will cause the gfci on the generator to trip.
OK, that's making a bit more sense. By the two 30A breakers on the 240V outlet of the generator are basically GFCI breakers. So, just being bonded at one end (at the generator) doesn't allow that to happen.

It sounds to me like the best solution is to not connect the generator ground to the panel bus bar, but to ground the generator itself outside, per the owner's manual.
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Old 06-30-2012, 04:17 PM   #38
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Wiring Generator to Backfeed Breakers - Neutral and Ground Wires?


If you use an ungrounded extension cord (or unhook the green wire from the male receptacle on the side of the house) you eliminate the duplicate return path from the house panel via the ground wire and permanently bonded neutral and ground in the generator and thus prevent the generator GFCI from tripping under otherwise normal operation.

The generator GFCI will still protect persons from electrocution from generator power because the generator neutral is the ultimate return destination and the generator hot and neutral are monitored by the GFCI.

With an interlock transfer (any kind) set for utility power, there is no current flowing on the generator line to the house so there would not be a voltage drop on the neutral. In turn there could not be a floating above zero volts of the generator body still bonded to that neutral. (Zero volts relative to the other end of the generator neutral which is at the neutral bus and connection to the grounding electrode conductor.)
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Last edited by AllanJ; 06-30-2012 at 04:36 PM.
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Old 06-30-2012, 07:20 PM   #39
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Wiring Generator to Backfeed Breakers - Neutral and Ground Wires?


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Originally Posted by AllanJ View Post
If you use an ungrounded extension cord (or unhook the green wire from the male receptacle on the side of the house) you eliminate the duplicate return path from the house panel via the ground wire and permanently bonded neutral and ground in the generator and thus prevent the generator GFCI from tripping under otherwise normal operation.

The generator GFCI will still protect persons from electrocution from generator power because the generator neutral is the ultimate return destination and the generator hot and neutral are monitored by the GFCI.

With an interlock transfer (any kind) set for utility power, there is no current flowing on the generator line to the house so there would not be a voltage drop on the neutral. In turn there could not be a floating above zero volts of the generator body still bonded to that neutral. (Zero volts relative to the other end of the generator neutral which is at the neutral bus and connection to the grounding electrode conductor.)
Yes, I see that. I was somewhat confused by the term "extension cord." I was picturing an extension cord like you might use to use a drill away from an outlet in your house.

I'll be using the 240V 30A NEMA L14-30 outlet on the generator, and, therefore, a heavy, 4-conductor cable (L14-30P - L14-30 R) from the generator to a L14-30P inlet box, then wire the inlet box to either a transfer switch or to two 30A backfeed breakers in the main panel (if I opt to use an interlock on the panel).

In either event, I won't connect the ground line from the generator to the transfer switch or the main panel... just let it float.

So, again, my remaining question: Should I physically ground the generator (to a grounding rod or some such) as specified in the owner's manual? I'm assuming that I should.

Thanks again!

Last edited by tjnoff; 07-06-2012 at 08:19 PM.
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Old 07-06-2012, 04:13 PM   #40
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Wiring Generator to Backfeed Breakers - Neutral and Ground Wires?


Hi!

I'm going through the same exact thing as tjnoff is. I have a Champion 7000/9000w generator and I bought a "generator inlet" box that I mounted outside. I have that wired to my main panel and have a 30 amp 2 pole breaker. On the generator, I purchased a 240v L14-30 4 conductor cable that I plug into the generator and then into the inlet. From what I read, it's a white, ground, and two hots on the inlet and outlet on generator. Nothing else is connected to the generator. No ground, nothing for the 120v outlets, nada.

I assumed everything is grounded through the panel and sent to the generator via the ground in the cable. I want to do it the right way and that's why I'm asking.


Thanks!
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Old 07-06-2012, 08:33 PM   #41
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Wiring Generator to Backfeed Breakers - Neutral and Ground Wires?


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Hi!

I'm going through the same exact thing as tjnoff is. I have a Champion 7000/9000w generator and I bought a "generator inlet" box that I mounted outside. I have that wired to my main panel and have a 30 amp 2 pole breaker. On the generator, I purchased a 240v L14-30 4 conductor cable that I plug into the generator and then into the inlet. From what I read, it's a white, ground, and two hots on the inlet and outlet on generator. Nothing else is connected to the generator. No ground, nothing for the 120v outlets, nada.

I assumed everything is grounded through the panel and sent to the generator via the ground in the cable. I want to do it the right way and that's why I'm asking.


Thanks!
There was a further discussion of this here: A discussion on the Proper grounding for portable generators

The consensus was that the best solution for wiring a portable generator to your main power panel (where neutral and ground are bonded together) was to run all four conductors (both hots, neutral and ground) from the generator through the inlet box to the power panel, and connect both neutral and ground to the panel's bus bar, but only if ground and neutral are UNbonded on the generator. This is probably a couple of wires in the actual generator part of your portable generator.

Also, were you ever to use your generator stand-alone, to power tools in the field, for instance, you MUST rebond neutral and ground on the generator.
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Old 07-06-2012, 08:56 PM   #42
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Wiring Generator to Backfeed Breakers - Neutral and Ground Wires?


Thanks for the shortened version. I didn't check the link, but in a short and sweet answer, what could happen if you don't unbound the neutral and ground on the generator?

Also, what happens in situations where the ground is to the EMT conduit? It doesn't get grounded to the bus bar through a cable, however, the neutral is grounded, as far as I know. So, essentially, the ground goes to the EMT which is grounded to the neutral....

Confusing stuff.

Thanks again for the short and sweet version!
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Old 07-06-2012, 09:03 PM   #43
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Wiring Generator to Backfeed Breakers - Neutral and Ground Wires?


your ground could potentially carry some current.
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Old 07-06-2012, 09:07 PM   #44
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Wiring Generator to Backfeed Breakers - Neutral and Ground Wires?


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your ground could potentially carry some current.
Being that it's the same size, it will carry half the current.
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Old 07-06-2012, 10:34 PM   #45
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Wiring Generator to Backfeed Breakers - Neutral and Ground Wires?


It is my belief that nothing bad will happen if the generator cannot easily have neutral and ground unbonded (and that step/process/instruction/mandate was therefore omitted/skipped/neglected) and also the panel was not revamped to separate grounds and neutrals, whether or not the ground connection (equipment grounding conductor) between the generator and panel is a metal conduit or a wire.

It would be a good idea to check the link to that other thread on proper grounding and reading the entirety thereof.

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Last edited by AllanJ; 07-06-2012 at 10:41 PM.
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