Portable generator bonding queston

[K8MHZ]

All the portable generators I have seen have the neutral and ground bonded in the generator.

Typically, they use a 4 wire circuit from the generator to the transfer switch. The popular UL approved transfer switches don't switch the neutral. Installing them according to instruction, it seems to me that while the generator is supplying power to the circuits in the transfer switch panel, there exists two points of bonding, one in the genny and one in the HO's panel.

There are thousands of these installed.

Q1: I don't see a safety issue with having the two bonding points, in fact, I would see a safety issue if the bond in the generator was removed. Am I missing something?

Q2: Since the transfer switch is a UL listed device, if it is installed according to instruction does that negate the single neutral/ ground bond requirement of the NEC?

There is not much to the installation of these transfer switches. There is a pair of conductors from each switch (typically 6 switches) that intercepts the desired circuits and are connected in the panel, and one neutral and one EGC going from the panel to the transfer switch. From the transfer switch, 'house wiring' (manufacturers words) connects the transfer switch to an outside receptacle box (supplied with transfer switch) and a cord with L1430 ends on it (also supplied) that goes from the outdoor box to the L1430 receptacle on the generator.

Q3: Is the above installation code compliant for use in a residence? If not, what, exactly, is the violation.

Q4: If the above installation is NOT code compliant, what would need to be changed in order to satisfy the code's requirements?

Here is a typical transfer switch unit: http://www.homedepot.com/h_d1/N-25e...Id=-1&keyword=transfer switches&storeId=10051

View attachment 6460

And, in for the case in question, this generator (labeled that the neutral and ground were bonded in the genny) would be used:

View attachment 6461

http://www.generac.com/Portables/GP/Products/GP6500_and_6500E/

Thanks!!

 

[jumper]

i thought that the ng bond for the genny was supposed to be removed.

 

[K8MHZ]

i thought that the ng bond for the genny was supposed to be removed.

How, exactly, is that supposed to be done? There are no provisions on any portable generator I have ever seen for this.

And if it is done, and used without the transfer switch (just plugging stuff into the receptacles) don't you think that would create a grave safety issue, having the frame floating with no bonding?

 

[ron]

All the portable generators I have seen have the neutral and ground bonded in the generator.

I just bought a Powermate PM0418000 that has a floating neutral. See this list for which have/have not http://www.generlink.com/CompatibleGenerator.pdf

Installs that use a bonded neutral at the gen and a solid neutral transfer must be corrected.

 

[ron]

Interesting bulletin from Honda
http://members.rennlist.org/warren/honda.pdf

 

[K8MHZ]

I just bought a Powermate PM0418000 that has a floating neutral. See this list for which have/have not http://www.generlink.com/CompatibleGenerator.pdf

Installs that use a bonded neutral at the gen and a solid neutral transfer must be corrected.

Cool, that's a great list, but it says that the generator in question has a floating neutral, but the label on the generator says the neutral is bonded to the frame.

:?

 

[texie]

To further complicate things, the latest portable gensets have GFCI to my understanding.

 

[K8MHZ]

To further complicate things, the latest portable gensets have GFCI to my understanding.

Not on the one I am talking about.

 

[ron]

Cool, that's a great list, but it says that the generator in question has a floating neutral, but the label on the generator says the neutral is bonded to the frame.

:?

Use an ohm meter and check from N to G at the receptacle and see ......

 

[K8MHZ]

Use an ohm meter and check from N to G at the receptacle and see ......

If I had the generator here I would. In retrospect, I should have done it when I was there.....I just took for granted that the labeling was correct.

 

[don_resqcapt19]

...
Q2: Since the transfer switch is a UL listed device, if it is installed according to instruction does that negate the single neutral/ ground bond requirement of the NEC? ...

I don't see how anything in any listing can modify a code requirement.

 

[K8MHZ]

I don't see how anything in any listing can modify a code requirement.

We installed a bunch of refrigeration equipment in a large store and the equipment was built with a green wire for thermostat control. It wasn't grounded. The inspector looked at it and said that because it was part of a UL listed piece of equipment and was made that way, the NEC did not apply.

We did not use green for our runs back to the control center.

So, was the inspector incorrect and as such, should have made us tear apart the 50 or so freezers and refrigeration units and try to figure out how to remove the green wire from the thermostat (buried somewhere in the units) and replace it with a wire of a different color?

 

[ActionDave]

All the portable generators I have seen have the neutral and ground bonded in the generator.
Q1: I don't see a safety issue with having the two bonding points, in fact, I would see a safety issue if the bond in the generator was removed. Am I missing something?
!

There are a lot of portable generators that have the neutral floating. Most of the generators I have worked on are non-SDS.

If you have the neutral bonded at the house and the genny you can put neutral current on grounded parts.
Most portable generators are connected with a rubber cord so it may not be a big deal but not a good thing.

 

[T.M.Haja Sahib]

And if it is done, and used without the transfer switch (just plugging stuff into the receptacles) don't you think that would create a grave safety issue, having the frame floating with no bonding?

The neutral from the portable generator should be grounded.Otherwise,ground fault protection devices will not operate.

 

[T.M.Haja Sahib]

Interesting bulletin from Honda
http://members.rennlist.org/warren/honda.pdf

If the neutral to frame bonding were done downstream to GFI on their gen sets,the tripping would not have happened and GFI protected gen sets of Honda would be OHSA compliant.Honda might have corrected this design error by now.........

 

[jwelectric]

I recommend that one look at the UL White Book for FTCN and 590.6(A)(3) of the 2011 NEC.

 

[kwired]

Cool, that's a great list, but it says that the generator in question has a floating neutral, but the label on the generator says the neutral is bonded to the frame.

:?

Someone beat me to it but check continuity from N-G on the generator. I haven't checked a lot of them but can't remember finding one that was bonded when I did check.

The neutral from the portable generator should be grounded.Otherwise,ground fault protection devices will not operate.

It is bonded at the service equipment by the main bonding jumper.

When not used to power a premesis wiring system it is an ungrounded system - perfectly safe to use. If one conductor becomes inadvertently grounded - nothing happens, when a second conductor becomes grounded overcurrent protection trips.

 

[don_resqcapt19]

We installed a bunch of refrigeration equipment in a large store and the equipment was built with a green wire for thermostat control. It wasn't grounded. The inspector looked at it and said that because it was part of a UL listed piece of equipment and was made that way, the NEC did not apply.

We did not use green for our runs back to the control center.

So, was the inspector incorrect and as such, should have made us tear apart the 50 or so freezers and refrigeration units and try to figure out how to remove the green wire from the thermostat (buried somewhere in the units) and replace it with a wire of a different color?

The interal wiring of listed equipment is not subject to the NEC, however I don't see this as an internal wiring issue. It is a system connection issue and is a code violation. UL listings cannot change legally adopted codes.

 

[don_resqcapt19]

If the neutral to frame bonding were done downstream to GFI on their gen sets,the tripping would not have happened and GFI protected gen sets of Honda would be OHSA compliant.Honda might have corrected this design error by now.........

If the neutral to ground bonding is done downstream of the generator GFCI, then the GFCI will not provide any protection.

 

[kwired]

A GFCI does not care where the system bonding jumper is. All it cares about is that all the current leaving one conductor returns on the other(s). If the bonding is done on the load side of GFCI it could mean more problems than if bonding is done on line side. Bonding on line and load side is definately not going to work - which is what has to happen for a floating neutral generator to trip a unit mounted GFCI.