Portable Generator for Back feeding Residential Panel

wmeek

Senior Member
Location
Texas
Occupation
Electrician
I'm confused. So when back feeding a residential panel with a 50A-4 wire cord from Generator to Inlet Outlet using a mechanical Interlock device, which label do you use from 702.7(C). If you check continuity from neutral to ground on Generator and have no continuity would you use floating neutral label and if you had continuity between neutral and ground do you use bonded neutral label. I am thinking you would want to use the floating Neutral system and use building GEC.
 

wmeek

Senior Member
Location
Texas
Occupation
Electrician
I have a Question again. I am using a 50A Inlet and Interlock System for Portable Generator Hookup. I talk to Generator Manufacturer Tech Support and will remove the Bonding jumper from Generator to create a floating neutral system and use Main Panel for the bonding of the neutral. I will use a Decal of floating Neutral System Only per 702.7(C) on Inlet Box. Question is where can I get a Tag for Generator showing the changes made to generator, so if someone wanted to use it in the field they would see that the change was made
 

LarryFine

Master Electrician Electric Contractor Richmond VA
Location
Henrico County, VA
Occupation
Electrical Contractor
I will use a Decal of floating Neutral System Only per 702.7(C) on Inlet Box. Question is where can I get a Tag for Generator showing the changes made to generator, so if someone wanted to use it in the field they would see that the change was made
Same decal.
 

wmeek

Senior Member
Location
Texas
Occupation
Electrician
So when I remove the bond from the portable Generator to create the floating neutral for this hook up, what kind of labeling is required by code. I have vinyl stick on labels but what else is approved to use that would be easier to change back and forth when removing bond and replacing bond to be able to use Genny for this set up and to use it in Field as well.
 

jap

Senior Member
So when I remove the bond from the portable Generator to create the floating neutral for this hook up, what kind of labeling is required by code. I have vinyl stick on labels but what else is approved to use that would be easier to change back and forth when removing bond and replacing bond to be able to use Genny for this set up and to use it in Field as well.
An electrician.

If an "average Joe" ends up with this generator after the bond has been removed, and they don't know any better, they will more than likely just use it as they bought it.

JAP>
 

jap

Senior Member
Could do it the old fashioned way.

Remove the bonding jumper on the generator.

Makeup a 15a male cord cap with a jumper from the neutral to the ground prong.

Hang it off the generator on a piece of string with a sign on it that says "Plug in to bond neutral to ground when needed". :)

JAP>
 

infinity

Moderator
Staff member
Location
New Jersey
Occupation
Journeyman Electrician
I have a Question again. I am using a 50A Inlet and Interlock System for Portable Generator Hookup. I talk to Generator Manufacturer Tech Support and will remove the Bonding jumper from Generator to create a floating neutral system and use Main Panel for the bonding of the neutral. I will use a Decal of floating Neutral System Only per 702.7(C) on Inlet Box. Question is where can I get a Tag for Generator showing the changes made to generator, so if someone wanted to use it in the field they would see that the change was made
In what section is the label requirement for the generator?
 

wmeek

Senior Member
Location
Texas
Occupation
Electrician
So the easiest way is to just remove the bond on Generator to create a Floating neutral application and hang a tag off of generator to let anyone who uses the Generator for a Stand Alone know that bond wire has been removed and needs to be reattached to create a Bonded Neutral .
I will install the interlock and Inlet and label everything for a floating neutral only. By using this system there is no way to control others from hooking up a bonded neutral system to this other than the Warning Label on Inlet box and Panel.
 

synchro

Senior Member
Location
Chicago, IL
Occupation
EE
Why not add a labeled switch?
If you added a 7.5K 5W resistor in parallel with the switch then a GFCI would trip if there's more than 6 ma of leakage to the EGC, even if the switch is left open when it should be closed. And when the switch is used properly the resistor would be shorted across by either the N-EGC bond in the panel or by the added switch (and so the resistor would have no effect).

It probably wouldn't trip with a plug-in tester because the 7.5K resistor would be in series with the resistor inside of the tester, and would therefore reduce the test current to about 5 mA. But that's because of the limitations of cheap testers which use a resistor instead of providing a constant current load.
 
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jap

Senior Member
The opening and closing of the switch would simply determine where the bond is taking place.

Either at the generator or at the service being fed.

What effect, if any, would this have on the GFI protection of the generator outlets?

JAP>
 

edward

Senior Member
Location
CA
Occupation
Electronologist
Use a NC contactor with a momentsry switch. When the generator is used for the house the neutral will be disconnected by the momentary switch and the contactor. When the generator is used out in the field the NC contactor keeps the neutral bonded.

Works like a charm.

IMO, don't leave the neutral disconnected on the portable generator. It may be an accident waiting to happen.
 
Use a NC contactor with a momentsry switch. When the generator is used for the house the neutral will be disconnected by the momentary switch and the contactor. When the generator is used out in the field the NC contactor keeps the neutral bonded.

Works like a charm.

IMO, don't leave the neutral disconnected on the portable generator. It may be an accident waiting to happen.
IMO floating neutral is safer for a portable generator.
 

Dsg319

Senior Member
Location
West Virginia
Occupation
Journeyman Electrician
Use a NC contactor with a momentsry switch. When the generator is used for the house the neutral will be disconnected by the momentary switch and the contactor. When the generator is used out in the field the NC contactor keeps the neutral bonded.

Works like a charm.

IMO, don't leave the neutral disconnected on the portable generator. It may be an accident waiting to happen.
Not being a butt, just curious what posses as danger for leaving the generator floating.
 

infinity

Moderator
Staff member
Location
New Jersey
Occupation
Journeyman Electrician
It would be simple enough to design the portable generator so that the user needs to select bonded or un-bonded before starting it. A simple selector switch that resets to OFF when the generator is shutdown would work. Prior to starting the user would need to select bonded or un-bonded.
 
Not being a butt, just curious what posses as danger for leaving the generator floating.
Nothing. We are just irrationally obsessed with grounding here in the states. Most hear the word "ungrounded" or "floating" and the hands start wringing and the therapist gets called. Just look at how long we held off on ungrounded PV systems, which are superior.
 

edward

Senior Member
Location
CA
Occupation
Electronologist
Not being a butt, just curious what posses as danger for leaving the generator floating.
You are not. Somebody has to keep me on my toes.
The only thing that come to mind, if the frame of the generator gets energized with the neutral disconnected from the frame.
 
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