portable generator bonding

[MDS75]

Installed 30 amp 4 wire recep and used interlock on a square d meter/combo panel. Have not seen generator yet to see if neutral is bonded to frame but if so my understanding is the neutral and ground need to be split on generator frame because the neutral is not switched and It is not a SDS. Since neutral and grounds are bonded in panel I need to break bond in generator or am I wrong on this?

 

[George Stolz]

You're right, also see 702.7(C) for the inlet signage required.

 

[infinity]

Many new portable generators have the neutral factory bonded to the frame. According to Generac they do not recommend that you un-bond the neutral. Having said that doing so isn't very difficult but can create a problem if the generator is used for stand alone power without connection to a structure where the service has a main bonding jumper.

 

[K8MHZ]

Many new portable generators have the neutral factory bonded to the frame.

Some do, some don't, some offer both options for the same model. They should be labeled as to the configuration.

 

[Radioman91]

Portable Generator Connection

Portable Generator Connection

Installed 30 amp 4 wire recep and used interlock on a square d meter/combo panel. Have not seen generator yet to see if neutral is bonded to frame but if so my understanding is the neutral and ground need to be split on generator frame because the neutral is not switched and It is not a SDS. Since neutral and grounds are bonded in panel I need to break bond in generator or am I wrong on this?

Not only does GENERAC recommend NOT removing the neutral-ground bond on portable generators, doing so will likely void the warranty (unauthorized modification). Your best bet for installing a portable generator connection is to do so as a separately derived system using a transfer switch that switches the neutral (i.e. Reliance XS series). This leaves in place the factory installed neutral-ground bond and the unit remains safe for use as a portable generator (i.e. camping, hunting, jobsite, etc.).

Also by removing a factory installed neutral-ground bond you are by definition removing a "safety device" from a consumer product. IMHO this is a very poor idea! I would strongly advise that you have a discussion of this practice with your legal council prior to proceeding.

Your MUST also properly label the portable generator power inlet as required by NEC 702.7(C).

 

[infinity]

I removed the bond from my Generac home generator which is about a 5-10 minute job. If needed I can put it back in the same amount of time.

IMO these should come with a switching mechanism so they can be used either with or without the neutral bonded. Leaving it bonded and installing it as an SDS with a transfer switch seems to be overkill when for $100 you can buy an inlet box and a breaker interlock and operate the system safely.

 

[George Stolz]

IMO, if someone is going to blunder in and connect a generator without understanding what any of this means (Joe Homeowner), then I would like a main bonding jumper covering my fanny, and if they commit a code violation by having a second bonding jumper in the system, then the objectionable current that flows is on their conscience - and entirely unnoticed.

-The Guy Who Found Another Missing Jumper On A 20-Year-Old Detached Garage Yesterday.

 

[infinity]

Just put up the proper sign and all is good.

 

[K8MHZ]

What is the worst thing that could happen as a result of having the N-G bond at both the generator and the service panel?

 

[infinity]

What is the worst thing that could happen as a result of having the N-G bond at both the generator and the service panel?

You would end up with a parallel neutral in the cord set. Not much would happen.

 

[K8MHZ]

You would end up with a parallel neutral in the cord set. Not much would happen.

Then why is it taboo? Or am I not understanding the code correctly?

 

[Little Bill]

It will not let the GFCI set.

 

[ActionDave]

Then why is it taboo? Or am I not understanding the code correctly?

It is similar to other cases where you re-bond the neutral. As a general rule, under the NEC, we don't do that because we don't want objectionable current on metal parts.

It is not always a big deal with portable generators because usually you have a rubber cord that connects it to the house so you are not putting neutral current on any metal that is not supposed to carry current. One time it does cause a problem is what Bill mentioned when you have ground fault protection.

 

[qcroanoke]

What is the worst thing that could happen as a result of having the N-G bond at both the generator and the service panel?

Not much. But if the outlets on the genset are GFI they won't stay on with the N/G bond in it.

 

[GoldDigger]

Not much. But if the outlets on the genset are GFI they won't stay on with the N/G bond in it.

Let me correct that slightly:

If there are GFCI outlets on the generator, the GFCI will trip if there are loads downstream of the outlet and there is an N-G bond downstream of the GFCI as well as an N-G bond upstream of the GFCI.

If there is an N-G bond upstream but not downstream it should not trip the GFCI.
The problem comes when you run a non-SDS configuration at the transfer switch or remote load on the generator and that lets the generator circuit see that downstream bond.

 

[tom baker]

Mike Holt would have a graphic done.

 

[qcroanoke]

Let me correct that slightly:

If there are GFCI outlets on the generator, the GFCI will trip if there are loads downstream of the outlet and there is an N-G bond downstream of the GFCI as well as an N-G bond upstream of the GFCI.

If there is an N-G bond upstream but not downstream it should not trip the GFCI.
The problem comes when you run a non-SDS configuration at the transfer switch or remote load on the generator and that lets the generator circuit see that downstream bond.

Correct, I left out the bond in the service......

 

[shortcircuit2]

Neutral to Ground Bond

Neutral to Ground Bond

If using a portable generator for portable applications the generator should have a bonded neutral to ground at the generator?

I just read both instruction manuals for the HONDA EU2000i and the EU3000is inverter generators which are primarily used for portable applications and the neutral is NOT bonded in the generator.

Both Honda generators do NOT have a GFCI protected receptacle outlet on the generator and if one uses a portable GFCI cord inline with the tool or appliance used, the GFCI would not operate without that neutral to ground bond?

Shouldn't these generators be bonded internally?