Gen set grounding

[Isaiah]

I have a small Genset of 25kW for temp power to a lighting panel that is 480/277V
Electricians are want to ground the neutral at both the generator and the panel board.
But it appears the neutral can be grounded at the Panelboard only as long as the system bonding jumper and GEC are intact at the Panelboard


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[ActionDave]

You are correct, there should only be one bond, at the panel or at the generator.

If I was your electrician I'd be more apt to go ahead and bond at the panel and not worry too much about the generator either way. What is the reason for them wanting to bond both?

 

[texie]

I have a small Genset of 25kW for temp power to a lighting panel that is 480/277V
Electricians are want to ground the neutral at both the generator and the panel board.
But it appears the neutral can be grounded at the Panelboard only as long as the system bonding jumper and GEC are intact at the Panelboard


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You need to determine whether the transfer switch has a switched neutral or not. This will dictate how it should be set up. If it is an non switched neutral TS, you must remove the generator bond and run an EGC back to the genset. If they are using a switched neutral TS, it must be set up as a SDS and have the bond at the genset and a GES attached.

 

[Isaiah]

You are correct, there should only be one bond, at the panel or at the generator.

If I was your electrician I'd be more apt to go ahead and bond at the panel and not worry too much about the generator either way. What is the reason for them wanting to bond both?

Thanks Dave


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[Isaiah]

You need to determine whether the transfer switch has a switched neutral or not. This will dictate how it should be set up. If it is an non switched neutral TS, you must remove the generator bond and run an EGC back to the genset. If they are using a switched neutral TS, it must be set up as a SDS and have the bond at the genset and a GES attached.

There is no transfer switch


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[texie]

There is no transfer switch


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OK, I did not get that part. Assuming the genset has a main breaker then the bond jumper should be at the genset. From the breaker on it is a feeder.

 

[Isaiah]

OK, I did not get that part. Assuming the genset has a main breaker then the bond jumper should be at the genset. From the breaker on it is a feeder.

The genset neutral is inherently bonded within the equipment from the manufacturer.
The question is whether hot not the neutral should be taken to an earth electrode (ie GEC) at the generator or the Panelboard....or at both locations. I think the GEC should be grounded only once.
In our case it would be easier to do this at the Panelboard.


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[Little Bill]

The genset neutral is inherently bonded within the equipment from the manufacturer.
The question is whether hot not the neutral should be taken to an earth electrode (ie GEC) at the generator or the Panelboard....or at both locations. I think the GEC should be grounded only once.
In our case it would be easier to do this at the Panelboard.


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Your panel board should be treated as a sub panel, with the bond already in place at the generator, the GEC should be connected there. Now if the panel board is in/at a separate structure, then a GES should be there as well. Only difference is the GEC would not land on the neutral bar, it should be on the ground/EGC bar. Of course a 4-wire feeder should be run from the generator.

 

[LarryFine]

There you go: the generator is your house's main panel and the panel is your detached garage.

 

[ActionDave]

The genset neutral is inherently bonded within the equipment from the manufacturer.
The question is whether hot not the neutral should be taken to an earth electrode (ie GEC) at the generator or the Panelboard....or at both locations. I think the GEC should be grounded only once.
In our case it would be easier to do this at the Panelboard.


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I misread your OP. I thought the question was about bonding the neutral at the generator and the panel. This is a question about earthing the generator and the panel.

Bill and Larry are correct, float the neutral at the panelboard and hook the GEC up to the equipment ground bar if you have a separate equipment ground running from the generator. However, I stand by my original statement, since 99% of the time it's a rubber cord from the generator to the equipment being fed, having the neutral bonded at both places is no big deal.

I don't think you need a GEC for a portable generator, but it's not hurting anything.

 

[Isaiah]

Your panel board should be treated as a sub panel, with the bond already in place at the generator, the GEC should be connected there. Now if the panel board is in/at a separate structure, then a GES should be there as well. Only difference is the GEC would not land on the neutral bar, it should be on the ground/EGC bar. Of course a 4-wire feeder should be run from the generator.

Yes the generator is outside the building where the panelboard resides.
So what your saying is basically it’s treated like a service with GEC’s at both locations.


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[Isaiah]

I misread your OP. I thought the question was about bonding the neutral at the generator and the panel. This is a question about earthing the generator and the panel.

Bill and Larry are correct, float the neutral at the panelboard and hook the GEC up to the equipment ground bar if you have a separate equipment ground running from the generator. However, I stand by my original statement, since 99% of the time it's a rubber cord from the generator to the equipment being fed, having the neutral bonded at both places is no big deal.

I don't think you need a GEC for a portable generator, but it's not hurting anything.

Agreed.


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[Little Bill]

Yes the generator is outside the building where the panelboard resides.
So what your saying is basically it’s treated like a service with GEC’s at both locations.


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Yes

 

[Dnavarro]

hi
Anyone can help on this , wiring 1200A load side breaker inside a gen set in a FMC 6’ long to the wall of the aluminum enclosure of the unit. Using 3 4/0 wires per each of the 3 phases and 3 4/0 for neutral plus one 4/0 as ground . How can we run this set of wires please ?thanks a lot for any advice.

 

[roger]

hi
Anyone can help on this , wiring 1200A load side breaker inside a gen set in a FMC 6’ long to the wall of the aluminum enclosure of the unit. Using 3 4/0 wires per each of the 3 phases and 3 4/0 for neutral plus one 4/0 as ground . How can we run this set of wires please ?thanks a lot for any advice.

I don't think running the wires is your problem, 3 4/0's will not get you to where you need to be. You need to get an experienced EC or EE involved.

You probably need to start a new thread with your question(s)

 

[Dnavarro]

I don't think running the wires is your problem, 3 4/0's will not get you to where you need to be. You need to get an experienced EC or EE involved.

You probably need to start a new thread with your question(s)

Will tell you what someone did : they make 4 holes to run 4 FMC , 3 of them with 3 4/0 mtw rated open air 405A each inside , then an extra conduit , FMC as well with 3 neutrals 4/0 same kind as phrases and a single 4/0 as ground . This is a UL unit and I don’t think they did it by code . The way I think should be done is une set of wires per conduit and neutral and ground with them in each conduit .the stationary genset unit will be feeding an emergency panel in the other side of a wall where this unit will be installed

 

[Dnavarro]

Roger I have being building generators for the last 10 years and also kind of updated in the code rules but this is an specialty and I see irregularities made , before I point a fingiré I want to be very sure , I am very please for any advice ok , and read all mike holt ‘ books , a great engineer !

 

[hillbilly1]

I don't think running the wires is your problem, 3 4/0's will not get you to where you need to be. You need to get an experienced EC or EE involved.

You probably need to start a new thread with your question(s)

If they are the temporary welding cables that usually come with the rental, the op is good, but if using standard building wire, you are correct.

 

[Dnavarro]

No wire welding are used Roger ,will attache a pic , this wire is allowed for use inside the machine only but no wire welding , it is an stationary unit , not rental

 

[Dnavarro]

The pics