Generator grounding

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  #1  
Old 08-20-20, 02:02 PM
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Generator grounding

So as not to hi-jack WRDIY's post (https://www.doityourself.com/forum/o...ml#post2859396), I stated a new thread.

CWBuff replied to WRDIY thread to my question...

Quote:
If I understand the grounding requirements correctly a portable generator need not be separately grounded except when it is providing power to a house through a transfer switch.

My reply "It's my understanding that if it's bonded then that requirement is not needed, because grounding takes place at the house transfer switch. Am I wrong?"

CW again replied with..."I found this article that quotes OSHA requirements -
https://www.jadelearning.com/blog/gr...le-generators/"

Which I read.


I'm still confused.
My generator/inverter (Ryobi model i2300 with floating neutral) is connected directly to my cabin's circuit box. I asked the question back in Nov this past year (https://www.doityourself.com/forum/e...grounding.html) and was advised that a grounding rod was not necessary, grounding would take place via the cabin electrical box.
I also have a Coleman Powermate (PM0435001 with floating neutral) hook to my home via transfer switch but not grounded with a rod at the generator. Should I?
Thought I had this sorted out.
 
  #2  
Old 08-20-20, 02:26 PM
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No ground rod is needed at the gen when the gen is connected to a house electrical system. The earth ground is provided by the house electrode system. There needs to be a equipment ground connection from the gen to the house. You may be confused about the equipment ground vs. the electrode ground to earth. Electrode is for diverting lightning strikes whereas the equipment ground is for cleaning fault current. Floating neutral on the gen is correct.
 
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Old 08-20-20, 02:36 PM
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OK sounds reasonable. So when do I want to use a rod stuck in the ground? Or do I ever need to?
 
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Old 08-20-20, 05:04 PM
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Rod should be installed when gen is used in a place such as a camp site, construction site, off grid cabin.
 
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Old 08-20-20, 05:14 PM
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OK, understood. And how does bonded or unbonded affect that scenario?
Also if the generator is connected to the house, even though it's not providing power to the house, but I'm using one of the taps to say run a skill saw outside, do I need to ground the unit with a rod?
 
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Old 08-20-20, 05:54 PM
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OK, understood. And how does bonded or unbonded affect that scenario?
Bonded. Because you need a way for any ground fault current to get back to the source, and the neutral-ground bond accomplishes that when not connected to house. The ground rod isn't for a ground fault, but for lightning/surges.

Also if the generator is connected to the house, even though it's not providing power to the house, but I'm using one of the taps to say run a skill saw outside, do I need to ground the unit with a rod?
I don't think a ground rod is necessary, because you have a path for lightning or other surge to be diverted to earth. Namely, along the ground wire in your connection to the house panel, and from there via the grounding electrode conductor to your grounding electrodes.

Pros please correct me if I'm mistaken!

Edit: I'm assuming your connection to the house doesn't switch off the ground when the generator is connected, but house is running on PoCo power. In an interlock setup, only the hots are switched off, the ground and neutral remain in place.
 
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Old 08-20-20, 06:22 PM
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Thanks to both pattenp and cartman for clarification.
 
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Old 08-21-20, 07:49 AM
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This is what my generator manual says - " If this generator is used only with cord and plug connected equipment, National Electric Code does not require that the unit be grounded." That seems clear. If you are running off plug ins (i.e. tools or extension cords) no separate ground is required.

It is less clear about other circumstances. In those instances the manual simply says "Other methods of using the generator may require grounding . . . . . " "Consult an electrician." My assumption of a common other circumstance would be a generator wired to a transfer switch.

I think both those statements agree with the OSHA requirement.
 
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Old 08-21-20, 08:07 AM
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Mike Holt has an excellent (but long) video that explains about floating neutral vs bonded neutral generators in minute detail. It's worth a watch for sure.

https://www.youtube.com/watch?v=yS7usLY9zL4&t=116s
 
 

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