Portable Generator Grounding when not connected to any utility panel

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jimaldri

Member
Location
Massachusetts
Occupation
Retired Electrician
Sorry if the question sounds dumb. I've hooked up many separately -derived systems, in hospitals, using 4-wire transfer switches and always did them correctly. I have a small 240/120 generator that I want to connect to my house, but just using a small panel with outlets underneath. Never touches utility wiring. Generator neutral and ground are connected at the generator. 4-wire cord plugs into outlet on generator, and goes to 4-wire inlet at house. 4-wire from there to sub-panel, which has un-grounded neutral bar and separate ground bar. Panel would have no utility power in it. Does the generator frame, which is grounded, need to be connected to the grounding electrode system of the house? It would be easy to do since there is a driven rod electrode, part of the EGS, close by. I was just concerned that the ground-fault breaker on the generator may not work correctly if I do. I've read 250. many times and keep getting confused.
 

tom baker

First Chief Moderator
Staff member
A ground rod is not as important as system bonding. In the event of a line to case fault, the electrons need to get to source ie generator windings, via the bonding jumper.
is the generator neutral bonded or floating?
 

jimaldri

Member
Location
Massachusetts
Occupation
Retired Electrician
generator neutral is bonded at the generator. Since the generator supply never enters any device containing utility supply, I didn't think I would need to bond the generator to the house's grounding electrode system. 250. says I need to if it connects to premises wiring, but I'm unclear as to the definition in my case.
 

kwired

Electron manager
Location
NE Nebraska
At the very least you technically have more than one premises wiring system though and they both need to tie to the building's GES.
 

don_resqcapt19

Moderator
Staff member
Location
Illinois
Occupation
retired electrician
If you have a panel that is physically installed at or to some structure, you are supplying premises wiring.
 

kwired

Electron manager
Location
NE Nebraska
If you have a panel that is physically installed at or to some structure, you are supplying premises wiring.
Looking at art 100 definition anything attached to the building can be premises wiring system.

Generator and drop cords is not a premises wiring system, generator supplying a fixed receptacle on the building is.

Items within an appliance, luminaire, motor are not included.
 

jimaldri

Member
Location
Massachusetts
Occupation
Retired Electrician
Thank You all for your replies. I must agree with the premise wiring definition, every now and then I get into circular arguments with myself and need a detached opinion.
 
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