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Old 06-29-2012, 04:25 PM   #1
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Wiring Generator to Backfeed Breakers - Neutral and Ground Wires?


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!
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Old 06-29-2012, 08:16 PM   #2
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Wiring Generator to Backfeed Breakers - Neutral and Ground Wires?


What type of interlock device? Who makes it?

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Old 06-29-2012, 08:29 PM   #3
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Wiring Generator to Backfeed Breakers - Neutral and Ground Wires?


You would use an ordinary breaker for backfeed purposes.

The best way to arrange ground and neutral for a backfed generator is to unbond the neutral from the generator's frame and ground connection inside the generator. Occasionally this cannot be done easily in which case I would be tempted to leave the green wire unhooked somewhere in the wiring between panel and generator. I would not mutilate a generator to get its neutral and ground unbonded.
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Old 06-29-2012, 08:54 PM   #4
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Wiring Generator to Backfeed Breakers - Neutral and Ground Wires?


Connect the neutral and the ground wires from the generator to the load center. DO NOT tamper with the generator.
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Old 06-29-2012, 08:57 PM   #5
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Wiring Generator to Backfeed Breakers - Neutral and Ground Wires?


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Connect the neutral and the ground wires from the generator to the load center. DO NOT tamper with the generator.
If you cannot remove the N-G bond at the generator, then you must switch the grounded connector at the transfer switch.
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Old 06-29-2012, 09:05 PM   #6
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Wiring Generator to Backfeed Breakers - Neutral and Ground Wires?


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If you cannot remove the N-G bond at the generator, then you must switch the grounded connector at the transfer switch.
And why would that be?
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Old 06-29-2012, 09:27 PM   #7
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Wiring Generator to Backfeed Breakers - Neutral and Ground Wires?


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And why would that be?

You can only have one point where your N-G are bonded together.
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Old 06-29-2012, 09:32 PM   #8
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Wiring Generator to Backfeed Breakers - Neutral and Ground Wires?


What do you think would be the consequences? It works fine on my personal home and others I have done.
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Old 06-29-2012, 09:39 PM   #9
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Wiring Generator to Backfeed Breakers - Neutral and Ground Wires?


A generator is not considered a permanent part of the electrical system. Removing the bond in the generator voids the warranty. Also if the generator is used for anything other than back feeding the house it could be potentially dangerous with the bond removed.

Oddly enough this is one of the reason a genny panel switches out the neutral that you argued so much about not needing.

brric, what's you've in essence done is run a ground and a neutral in parallel with each other, in theory they can both carry some of the current.
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Last edited by andrew79; 06-29-2012 at 09:42 PM.
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Old 06-29-2012, 09:43 PM   #10
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Wiring Generator to Backfeed Breakers - Neutral and Ground Wires?


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What do you think would be the consequences? It works fine on my personal home and others I have done.
Its a code violation, plain and simple. And just because it works, doesn't make it correct.
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Old 06-29-2012, 09:44 PM   #11
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Wiring Generator to Backfeed Breakers - Neutral and Ground Wires?


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A generator is not considered a permanent part of the electrical system. Removing the bond in the generator voids the warranty. Also if the generator is used for anything other than back feeding the house it could be potentially dangerous with the bond removed.

Oddly enough this is one of the reason a genny panel switches out the neutral that you argued so much about not needing.

brric, what's you've in essence done is run a ground and a neutral in parallel with each other, in theory they can both carry some of the current.
That is correct. It is a temporary plug and cord connection. It is not intended to be permanent. Also, removing the bond would create a possible generator fault clearing issue.
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Old 06-29-2012, 09:45 PM   #12
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Wiring Generator to Backfeed Breakers - Neutral and Ground Wires?


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Originally Posted by andrew79 View Post
A generator is not considered a permanent part of the electrical system. Removing the bond in the generator voids the warranty. Also if the generator is used for anything other than back feeding the house it could be potentially dangerous with the bond removed.

Oddly enough this is one of the reason a genny panel switches out the neutral that you argued so much about not needing.
I didn't argue anything, I told you current doesn't seek the earth.
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Old 06-29-2012, 09:46 PM   #13
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Wiring Generator to Backfeed Breakers - Neutral and Ground Wires?


i should have clarified, only the last bit of that post was directed at you brric, the first was for stickboy.

never thought of the fault issue, good point.
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Old 06-29-2012, 09:46 PM   #14
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Wiring Generator to Backfeed Breakers - Neutral and Ground Wires?


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That is correct. It is a temporary plug and cord connection. It is not intended to be permanent.
And is still a violation.
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Old 06-29-2012, 09:47 PM   #15
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Wiring Generator to Backfeed Breakers - Neutral and Ground Wires?


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i should have clarified, only the last bit of that post was directed at you brric, the first was for stickboy.
I know.

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