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Old 06-29-2012, 09:56 PM   #16
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Wiring Generator to Backfeed Breakers - Neutral and Ground Wires?


My research leads me to respectfully disagree.

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Old 06-29-2012, 09:58 PM   #17
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Wiring Generator to Backfeed Breakers - Neutral and Ground Wires?


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My research leads me to respectfully disagree.
So where in the NEC do you believe you can have two separate N-G connections? You can always just purchase a generator with a floating neutral, or install a 3 pole transfer switch, the option is yours.

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Old 06-29-2012, 10:11 PM   #18
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Wiring Generator to Backfeed Breakers - Neutral and Ground Wires?


Is a portable generator a separately derived system or non-separately derived system?
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Old 06-29-2012, 10:12 PM   #19
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Wiring Generator to Backfeed Breakers - Neutral and Ground Wires?


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Is a portable generator a separately derived system or non-separately derived system?
Thats not what determines it, the transfer switch does.

IF you have a solidly connected grounded (neutral) connection, then you do not have a SDS, if you break the grounded (neutral) connection then yes, you do have a SDS, and the generator then requires ground rods.


With that said, you MUST know if the generator you are wiring has a N-G connection before you can make the correct transfer switch selection.


This may help you digest some of the info I posted...http://www.imsasafety.org/journal/ma03/ma5.htm

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Old 06-29-2012, 10:15 PM   #20
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Wiring Generator to Backfeed Breakers - Neutral and Ground Wires?


How would you use a 3 pole transfer switch for the OP'S installation?
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Old 06-29-2012, 10:21 PM   #21
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Wiring Generator to Backfeed Breakers - Neutral and Ground Wires?


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How would you use a 3 pole transfer switch for the OP'S installation?
The only way you can use a interlock kit legally is if his generator has a floating neutral. Otherwise, he would need a manual 3 pole transfer switch.
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Old 06-29-2012, 10:43 PM   #22
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Wiring Generator to Backfeed Breakers - Neutral and Ground Wires?


Simpliest thing to do is to wire it up as is and see if the gfci trip on the generator, if it does then the simplest way to get it working is to float the ground coming from the generator inside the panel. Legalities of it can be argued for days. Keep in mind that the code only contains info on how to wire it up to the electrical system. the actual internal generator wiring is a UL standard that has to be followed by the manufacturer.

In all honesty there's a bunch of ways to wire them, if you look in the genny manual it will most likely tell you that you need either a 3 pole or 4 pole transfer switch if it has a bonded neutral inside. If it has a floating neutral then it will recommend a 2 pole transfer switch.

Safest and most expensive way is to leave the generator as is as to not void your warranty and actually spend the money on the recommended transfer switch for your particular unit.
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Old 06-30-2012, 02:06 AM   #23
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Wiring Generator to Backfeed Breakers - Neutral and Ground Wires?


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Hi! I'm planning on using an interlock kit (code approved model) when connecting my generator to my home's main power panel, as follows (drawing attached):

7500W generator (Generac GP7500E) with L14-30 generator cable connecting generator's 240V 30A outlet to an L14-30 inlet box (on house), then connect the inlet box to 30A dual-pole backfeed breakers in the primary power panel using 10/4 wire.

Backfeed breakers and main panel input breaker will be mutually exclusive using interlock (only one can be on at any given time).

My question is do I run both the neutral and ground wires from the inlet box to the neutral bus bar in this primary power panel, or just the neutral wire? If just the neutral wire, what's done with the ground feed? Anything?

One other secondary question: Are backfeed breakers unique from standard breakers? Do I need to find specifically backfeed breakers, or will your standard 30A dual-pole breakers work for this application?

Thanks for your help!
This would not be a separately derived system since your interlock does not open the neutral connection to the utility grounded conductor which has earth grounding both at the service equipment and utiltiy transformer.
Being a non separately derived system the the NEC would require that no neutral to ground bonds exist load side of the service equipment. You would technically, in order to be code compliant, need to determine if the neutral and ground are separated at the generator. In the event you do not isolate then your equipment grounding conductor will be energized due to the connected neutral of the utiltiy at the service equipment of the home with the generator neutral.
Bottom line is portable generators were designed to serve as power sources for job sites and cord and plug equipment not standby power for a home and therefore have neutral and ground bonded in acccordance with 250.30 while considering 250.34(A). Think of them as service equipment.

Now having said that I would venture to say 80% of portable generators powering homes with transfer switches or interlocks that do not switch the neutral do not have their neutrals isolated from ground. NOT because it isn't required but because they simply are not familiar with that rather confusing part of the NEC.

It would be advantageous to all of us to start a new thread about grounding of generators and in particular portable ones and when and when not to requrie ground rods at the generator. I would bet it will generate some eye opening. If we all tie in the NEC articles to back up the discussion I actually think we could reach a professional consensus on the code compliance requirements for grounding portable generators.

I would suggest providing graphics/drawings as well as Nec articles and subsections to make your points would be great. I'll start it and we can see where it goes... It would be better IMO if we do not link to other written articles and provide our own explanations to which others can add.

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Old 06-30-2012, 09:02 AM   #24
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Wiring Generator to Backfeed Breakers - Neutral and Ground Wires?


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What type of interlock device? Who makes it?
This one: http://www.interlockkit.com/InstrK8210GENewDsn.pdf
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Old 06-30-2012, 09:21 AM   #25
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Wiring Generator to Backfeed Breakers - Neutral and Ground Wires?


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Unfortunately installation of this kit is a violation of 110.3b. Wyle Labs lost its listing capabilities and it is not listed by any other recognized listing labs. Sorry.
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Old 06-30-2012, 09:29 AM   #26
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Wiring Generator to Backfeed Breakers - Neutral and Ground Wires?


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Unfortunately installation of this kit is a violation of 110.3b. Wyle Labs lost its listing capabilities and it is not listed by any other recognized listing labs. Sorry.
It was my understanding that anything previously listed by Wyle is still in force and legal. Those listings were not revoked.

They are no longer able to list any new products by the recent action of losing their certification.
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Old 06-30-2012, 09:39 AM   #27
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Wiring Generator to Backfeed Breakers - Neutral and Ground Wires?


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Old 06-30-2012, 10:06 AM   #28
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Wiring Generator to Backfeed Breakers - Neutral and Ground Wires?


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Unfortunately installation of this kit is a violation of 110.3b. Wyle Labs lost its listing capabilities and it is not listed by any other recognized listing labs. Sorry.
Interesting....
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Old 06-30-2012, 10:12 AM   #29
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Wiring Generator to Backfeed Breakers - Neutral and Ground Wires?


First, thanks to everyone for their thoughtful responses! I hadn't imagined that my query would garner such a lengthy discussion.

Frankly, I was hoping to use the interlock solution in order to make use of all of the circuits in the house during an outage, as you probably have guessed. Having over 20 individual circuits in the house, I didn't want to be limited to powering 10. Not that I'd power all 20-some-odd circuits at once with a 7500W generator, but it would be nice to have the flexibility to pick and choose from all 20 at any given time.

The differing opinions about how or if to connect the ground line in my proposed application leaves me feeling a bit sketchy about using the interlock solution, but I'm not sure that a transfer switch solution looks much different when it comes to the N and G connections.

This video (http://www.youtube.com/watch?v=5dKfV...e_gdata_player) shows the neutral and ground wires being used for the Reliance transfer switch solution. In part 1 of this video series (http://www.youtube.com/watch?v=7--oK...e_gdata_player), connecting the transfer switch to the power panel is shown, and both the ground and the neutral wires are used and connected to the neutral bar in the main panel. Once the transfer switches are put in the generator position, how does this differ from my interlock solution in regard to the NG connections? There is no mention in the videos about whether the N and G are bonded at the generator or not.

Sounds like a thread on grounding generators would be in order, and I'd like to know if anyone starts one, but I'd still like to know how to handle my situation.

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Old 06-30-2012, 10:19 AM   #30
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Wiring Generator to Backfeed Breakers - Neutral and Ground Wires?


Quote:
Originally Posted by tjnoff View Post
First, thanks to everyone for their thoughtful responses! I hadn't imagined that my query would garner such a lengthy discussion.

Frankly, I was hoping to use the interlock solution in order to make use of all of the circuits in the house during an outage, as you probably have guessed. Having over 20 individual circuits in the house, I didn't want to be limited to powering 10. Not that I'd power all 20-some-odd circuits at once with a 7500W generator, but it would be nice to have the flexibility to pick and choose from all 20 at any given time.

The differing opinions about how or if to connect the ground line in my proposed application leaves me feeling a bit sketchy about using the interlock solution, but I'm not sure that a transfer switch solution looks much different when it comes to the N and G connections.

This video (http://www.youtube.com/watch?v=5dKfV...e_gdata_player) shows the neutral and ground wires being used for the Reliance transfer switch solution. In part 1 of this video series (http://www.youtube.com/watch?v=7--oK...e_gdata_player), connecting the transfer switch to the power panel is shown, and both the ground and the neutral wires are used and connected to the neutral bar in the main panel. Once the transfer switches are put in the generator position, how does this differ from my interlock solution in regard to the NG connections? There is no mention in the videos about whether the N and G are bonded at the generator or not.

Sounds like a thread on grounding generators would be in order, and I'd like to know if anyone starts one, but I'd still like to know how to handle
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...

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