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I read previous posts that explained that the Sub Panel has a separate connection for ground and separate for neutral, while the Main Panel does not separate the ground & neutral - this is exactly how my panels are setup. My Sub Panel has all of the house's breakers and the panel is completely full. My Main Panel has the one Main Cut Off with areas to add breakers. I'm wanting to add a double breaker to the Main Panel for a 240 volt generator.

I have two questions:

  1. When I wire the generator inlet to the Main Panel, do I wire both the ground wire and neutral wire to the same connector as is done now with the ground & neutral at the Main Panel?
  2. The generator's owner's manual states that it's "neutral floating". I was intending to ground the generator (8' copper rod with 6 ga. solid copper). Does the floating neutral on the generator change anything?
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    What are you going to do for an interlock, to make it mechanically impossible for utility and generator breakers to be on at once? Reason I ask is it's often easier to do that at the subpanel, even if it means moving a few loads to the main or adding a sub-subpanel. Pix of both panels would also help if you want to go further down that line of inquiry. – Harper - Reinstate Monica Oct 4 at 17:15
  • Yes, using an interlock allowing one breaker on at one time - I've already installed the double breaker and interlok in the Main Panel. Since sub panel is full and main panel closer to generator, I went with the main panel. I've installed breakers before in sub panels and always connected the ground wire to the ground terminal and the neutral to the neutral terminal. However, my main panel has one connector that connects both, the neutral & ground - they are not separated. Question is whether to connect both the ground and neutral wires from generator to the same connector in main. – George Oct 4 at 19:18
  • I would post a photo but don't know how. I believe my main panel setup is called neutral/ground bus bar. Guess I'm concerned as I never connected both, the ground & neutral to the same connector. – George Oct 4 at 19:21
  • Hello, and welcome to Home Improvement. Post the URL of a picture, and someone will be along to edit it into your question. And, props for taking our tour; few newcomers do. – Daniel Griscom Oct 5 at 15:44
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The floating neutral is good news, but you don't need a ground rod for this

The fact that your generator has a floating neutral is actually quite fortunate for you, as breaker-interlock-based transfer setups are largely incompatible with generators that have bonded neutrals (the more common case). However, since you're plugging your generator into your house, which already has a grounding electrode system (ground rods, etc), you don't need to add a ground rod at the generator, as the house supplies both the grounding electrodes and the neutral-to-ground bond point.

As to the inlet, since it's your main panel, you can land both wires on the same bar

A common "shortcut" in main panels (esp. in residential work) is to slobber all the neutrals and grounds onto the same bar, since that's where neutral and ground meet. Since most panels where this is done don't have separate ground bars fitted to begin with, you're left with little choice but to continue this practice, unless you wish to buy a ground bar kit for your specific make and model of panel and add a separate ground bar.

  • Thank you very much for the well-explained answer. Although not necessary, would there be an issue if I added a ground rod for peace of mind? – George Oct 5 at 1:04
  • @George -- if you wish to do it, simply attach it to the grounding terminal on your generator, presuming it provides an earth-grounding post somewhere on the frame (if not, just attach it to bare metal on the frame) – ThreePhaseEel Oct 5 at 1:33
  • I asked about the ground rod because the manual states "The ground terminal is connected to the frame of the generator, the metal non-current-carrying parts of the generator, and the ground terminals of each receptacle. Before using the ground terminal, consult a qualified electrician, electrical inspector, or local agency having jurisdiction for local codes or ordinances that apply to the intended use of the generator. I've always assumed that the grounding rod was a definite. – George Oct 5 at 12:13
  • @George -- when powering a house, the house supplies the ground rod. If your generator was set up to power things standalone, with a bonded neutral, then using it as a portable wouldn't require a ground rod either, see NEC 250.34(A) for details – ThreePhaseEel Oct 5 at 14:19
  • Thank you again. – George Oct 5 at 18:25

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