Outdoor generator

[hhsting]

I have outdoor generator set with main breaker located 50 feet away from the building it serves. The gen main breaker is not within sight of building. So right where the gen feeders enter the building their is disconnecting means call it Disco A.

The gen is separtely derived and is grounded with GEC, system bonding jumper and GES. Main breaker of Gen feeds Disco A.

The Disco A is also grounded and GEC goes to building GES.

Gen grounded I understand but Disco A grounded again is something which is weird. So when asked why Disco A is grounded again with GEC going to building GES the engineer says its per NEC 2014 Article 250.32(B)(2)(a).

Is the engineer correct or incorrect about the above?

 

[hhsting]

Attached is sketch. No one has any input. Gen is separately dervied with main breaker and grounded with system bonding jumper, GEC to its own GES. Gen and main bkr is outside 50 feet away from BKR #1. Bkr #1 is outside building wall.

BKR #1 in sketch can it be grounded again with GEC going to building GES per NEC 2014 Article 250.32(B)(2)(a) correct or incorrect?

 

[LarryFine]

I'm having trouble answering because I'm not sure what you're asking. See if I have it correctly:

Generator has a neutral-ground bond and electrode(s). Building has a neutral-ground bond and electrode(s).

If you're asking whether the two separate electrode systems should be interconnected, the answer is NO.

The reason is that the interconnection would carry neutral current. Earth does not qualify as an interconnection.

 

[hhsting]

I'm having trouble answering because I'm not sure what you're asking. See if I have it correctly:

Generator has a neutral-ground bond and electrode(s). Building has a neutral-ground bond and electrode(s).

If you're asking whether the two separate electrode systems should be interconnected, the answer is NO.

The reason is that the interconnection would carry neutral current. Earth does not qualify as an interconnection.

Post #2 attachment Gen has neutral to bond, grounding electrode conductor (GEC) to grounding electrodes.

Post #2 attachment BKR #1 has GEC to building grounding electrode system (GES) and has NO neutral to bond. Neutral is isolated.

Reason for above is NEC 2014 Article 250.32(B)(2)(a). Is it correct or incorrect reason? Is that what NEC 2014 Article 250.32(B)(2)(a) says?

 

[synchro]

Bonding Brkr #1 panel to equipment ground wire coming from generator, and also to local GEC is correct according to pages 119 - 120 of:

https://books.google.com/books?id=pmFdDgAAQBAJ&printsec=frontcover#v=onepage&q&f=false
​​​​​​

 

[hhsting]

250.32(A) says building supplied by feeders shall have GES or GE in accordance with Part III of Article 250. The GEC shall be connected in accordance with 250.32(B) or (C).....

Post #2 attachment shows that generator is not supplying entire building but only those load on the load side of ATS. Which comes to question does the genrator feeder supply the building. However, if one reasons that should the ATS switches to generator side then generator feeder I guess would supply building since all the other loads not on ATS would not be supplied but would that be considered genrator feeder is supplying the building. Would 250.32 apply in Post #2 BKR #1 situation?

 

[Jim_SWFL]

I have a similar issue to the OP where section 250.32 was raised as a requirement for generator feeders to a remote building that has it's own dedicated service. I have attached a PDF to represent the situation. The top diagram shows the present design, with the conductive path of the EGC shown in green. The bottom diagram represents what the plans reviewer is asking for (shown in red) to satisfy sections 250.32(B)(1) and (B)(2)(a). Electrically I don't see the benefit to adding this second path.

The code requires the EGC to be "run with the supply conductors and be connected to the building or structure disconnecting means and to the grounding electrode(s)" and be "sized in accordance with 250.122".

My position would be that the EGC that is supplied with the feeder is connected the buildings disconnecting means and to the grounding electrode by the path shown in green in the attachment, and that there is no requirement for it to be larger than required by 250.122.

 

[jap]

I have a similar issue to the OP where section 250.32 was raised as a requirement for generator feeders to a remote building that has it's own dedicated service. I have attached a PDF to represent the situation. The top diagram shows the present design, with the conductive path of the EGC shown in green. The bottom diagram represents what the plans reviewer is asking for (shown in red) to satisfy sections 250.32(B)(1) and (B)(2)(a). Electrically I don't see the benefit to adding this second path.

The code requires the EGC to be "run with the supply conductors and be connected to the building or structure disconnecting means and to the grounding electrode(s)" and be "sized in accordance with 250.122".

My position would be that the EGC that is supplied with the feeder is connected the buildings disconnecting means and to the grounding electrode by the path shown in green in the attachment, and that there is no requirement for it to be larger than required by 250.122.

And I would agree with you.

JAP>

 

[ron]

Since the Neutral and ground are isolated at the 2nd disco, the fact that they connected the 2nd disco enclosure to the Grounding electrode system is fine. I typically have all metal objects (gen skid, enclosures, fence, door frames, etc) in the vicinity connected to the grounding electrode system. It would reduce side flash or touch potential in the event of a abnormal electrical incident.

 

[jap]

It's not only fine, it's required.

JAP>

 

[Jim_SWFL]

It's not only fine, it's required.

JAP>

Thanks for the replies.