Portable generator to generator subpanel bonding

C

clemver

Member
Location
PA
Occupation
Electrician
Hi all! I'm having some trouble wrapping my head around this one. I have a 5wk portable generator that I'll be hooking up to a ProTran2 generator subpanel/transfer switch. I'll have an inlet on the house with 3-wire ran to the generator panel. And 30A 2 pole from main panel to feed the generator panel. My question is where do I keep the neutral bonded?

My instincts tell me keep everything bonded in the main panel. Bring off a ground and neutral into the generator sub. Of the circuits I'm moving to the generator panel, move the neutrals over but keep the EGCs in the main panel. I'm certain that the generator will be bonded, so keep the subpanel unbonded. Since, while on generator power, the generator breaker is acting as the 1st disconnect (bonded), and the subpanel would be unbonded.

And while on regular power, it's still acting as a subpanel so unbonded neutral within is still fine. Just hoping I have that right. Thanks.
 
This is a system with 2 solutions and you need pick the generator and transfer switch together. If you have a bonded generator and can't unbond it, you must use a 3 wire feed from generator to xfer switch (hot-hot-neut), and you need a 3 pole transfer (that switches the neutral) and a ground electrode system for the generator. If you use a floating neutral generator, you use a 4 wire feed from generator to transfer switch (hot-hot-neut-ground) and a 2 pole transfer switch (solid neutral). In this latter case, the building ground electrode system and main bonding jumper take care of the grounding.

Make sure to read about the signage requirements in 702 for how you label the generator inlet and and warning signs about removing the ground electrode conductor.
 
suemarkp said:
This is a system with 2 solutions and you need pick the generator and transfer switch together. If you have a bonded generator and can't unbond it, you must use a 3 wire feed from generator to xfer switch (hot-hot-neut), and you need a 3 pole transfer (that switches the neutral) and a ground electrode system for the generator. If you use a floating neutral generator, you use a 4 wire feed from generator to transfer switch (hot-hot-neut-ground) and a 2 pole transfer switch (solid neutral). In this latter case, the building ground electrode system and main bonding jumper take care of the grounding.

Make sure to read about the signage requirements in 702 for how you label the generator inlet and and warning signs about removing the ground electrode conductor.
Click to expand...
Got it. With the ProTrans panel/transfer switch I dont think theres anyway to switch the neutral. These things transfer each individual circuit, not the feed in so I'd have to unbond his generator. But then if he wants to utilize one of the 120v receptacles on the generator, wouldn't that then be an issue? If a ground fault happened on an extension cord, the generator breaker wouldn't clear that, correct?

*EDIT*
The generators 120v duplex receptacles are GFI, so I may have answered my own question.
 
There are many floating neutral generators with local receptacles. A fault isn't hazardous because the generator isn't connected to the earth. You would need multiple faults to create a hazard. Local GFCI receptacles on the generator helps mitigate this hazard.

I think OSHA rules may have effectively prohibited floating neutral generators. But if this isn't a jobsite or business, then those rules don't matter. It may limit your generator choices though if the manufacturer wants to sell the same unit to jobsites and homeowners. Having the generator bonding switchable would help a lot. My generator says absolutely nothing about bonding. I had to determine that it was floating neutral.
 
suemarkp said:
There are many floating neutral generators with local receptacles. A fault isn't hazardous because the generator isn't connected to the earth. You would need multiple faults to create a hazard. Local GFCI receptacles on the generator helps mitigate this hazard.

I think OSHA rules may have effectively prohibited floating neutral generators. But if this isn't a jobsite or business, then those rules don't matter. It may limit your generator choices though if the manufacturer wants to sell the same unit to jobsites and homeowners. Having the generator bonding switchable would help a lot. My generator says absolutely nothing about bonding. I had to determine that it was floating neutral.
Click to expand...
What I also don't like is when this cheap little portable generator eventually takes a crap, homeowner buys another one same size same cord and plugs it right in and uses it. Now he has bonding at both ends. I could place signage and tell him about a floating neutral but let's be honest he won't care/remember. Seems almost unavoidable to have improper bonding with portable generators.
 
You are supposed to put a sign for just that reason as of 2020 or 2023 code. Given that the connection to a portable generator is going to be a rubber cord having the generator bonded isn't so terrible. I'm not saying that all appropriate steps and rules should not be followed.
 
suemarkp said:
This is a system with 2 solutions and you need pick the generator and transfer switch together. If you have a bonded generator and can't unbond it, you must use a 3 wire feed from generator to xfer switch (hot-hot-neut), and you need a 3 pole transfer (that switches the neutral) and a ground electrode system for the generator. If you use a floating neutral generator, you use a 4 wire feed from generator to transfer switch (hot-hot-neut-ground) and a 2 pole transfer switch (solid neutral). In this latter case, the building ground electrode system and main bonding jumper take care of the grounding.

Make sure to read about the signage requirements in 702 for how you label the generator inlet and and warning signs about removing the ground electrode conductor.
Click to expand...
Very good explanation!
 
clemver said:
What I also don't like is when this cheap little portable generator eventually takes a crap, homeowner buys another one same size same cord and plugs it right in and uses it. Now he has bonding at both ends. I could place signage and tell him about a floating neutral but let's be honest he won't care/remember. Seems almost unavoidable to have improper bonding with portable generators.
Click to expand...
Yes for sure. Seems like most generators are bonded neutral. There are issues when the generator has GFCI protection and the type of transfer switch. Like you say that’s lost on most home owners, they just want power in an outage.
 
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