Generator, ground rod or not

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dave121

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Location
Central Wisconsin
I need your help to clear up this ground rod install at a generator.
Our installs are on irrigation systems, supplied from a 3 phase, 4 wire, 480 volt engine mounted generator. The generator is only supplying the 3 phase 480 volt load.
The irrigator is anchored to a concrete encased electrode system, with a #4 cu. from the control panel to the cee. If the well is at the site, the well casing is also connected to the cce, so now there are 2 electrodes in close proximity.
Should the generator frame;
1. Have its own ground rod driven and be separate, not connected to the other electrode system? I'm pretty sure this is improper.
2. Be connected to the other system without an additional rod? Just an external conductor from the generator frame connected to the electrodes.
3. Not connected to the gec system at all except through the equipment grounding conductor run with the supply conductors from the generator to the irrigator? The EGC is connected to the generator frame in the wire box of the generator.
Thanks
 
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petersonra

Senior Member
Location
Northern illinois
Occupation
engineer
I don't believe there is a requirement that a generator have a separate grounding electrode system installed. So presumably one could use the existing GES.
 
don_resqcapt19

don_resqcapt19

Moderator
Staff member
Location
Illinois
Occupation
retired electrician
dave121 said:
I need your help to clear up this ground rod install at a generator.
Our installs are on irrigation systems, supplied from a 3 phase, 4 wire, 480 volt engine mounted generator. The generator is only supplying the 3 phase 480 volt load.
The irrigator is anchored to a concrete encased electrode system, with a #4 cu. from the control panel to the cee. If the well is at the site, the well casing is also connected to the cce, so now there are 2 electrodes in close proximity.
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Is the equipment in a building and the concrete encased electrode part of the structure for the building?
Should the generator frame;
1. Have its own ground rod driven and be separate, not connected to the other electrode system? I'm pretty sure this is improper.
Click to expand...
The generator frame must be bonded to a grounding electrode system.
2. Be connected to the other system without an additional rod? Just an external conductor from the generator frame connected to the electrodes.
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If the generator has a main breaker, the grounding electrode conductor must be connected to the system at the generator and the system bonding jumper will be located at the point of connection of the GEC. If there is no main breaker at the generator, the GEC connection and system bonding jumper would be located at the system main disconnect. In that case, there would be a system bonding jumper run between the generator and the location of the main disconnect.
3. Not connected to the gec system at all except through the equipment grounding conductor run with the supply conductors from the generator to the irrigator? The EGC is connected to the generator frame in the wire box of the generator.
Thanks
Click to expand...
The concrete encased electrode and the well casing if available would be the only electrodes required. I expect this SDS is outside, so the rules in 250.30(C) cover the required grounding electrodes.
 
don_resqcapt19

don_resqcapt19

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Location
Illinois
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retired electrician
dave121 said:
No buildings involved, outside in a field. Generator has a main fused disconnect. We will connect the GEC there.
Thanks to you all.
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Not sure you really have a concrete encased electrode. That must be in a footing or foundation. If the generator is just on a concrete pad, it would be my opinion that you don't have a CEE.
 
kwired

kwired

Electron manager
Location
NE Nebraska
don_resqcapt19 said:
Not sure you really have a concrete encased electrode. That must be in a footing or foundation. If the generator is just on a concrete pad, it would be my opinion that you don't have a CEE.
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I'm guessing he has something typical to what I may see around here. Center pivot irrigation machine, the center pivot attaches to a concrete pad, whether or not the pad has a CEE depends on construction of the pad. Some may have a footing and pad all in one concrete pour. The generator is likely powered by diesel engine that also drives the well pump. There is no utility power, only the on site derived power from said generator. Generator powers the center pivot machine.

Separately derived term as used when talking about transfer switches doesn't apply, there is no transfer switch.

Separately derived term would only mean it is on site derived supply and not a utility supply (service). There is not ordinarily any 277 volt loads so dealing with neutral conductors isn't an issue either than that it does have a neutral from the supply and it gets bonded usually right at the generator and from there on is EGC and/or GEC. Won't say they are always done to code here, but are pretty much never inspected either so nobody is enforcing code. Don't know I ever seen a GEC connected directly to one, is usually at first disconnect - usually within the center pivot control panel.

Most are only 10 kVA generators also.
 
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dave121

Member
Location
Central Wisconsin
It is ufer, full 20’ rerod encased in concrete, cement pad minimum 10’ sq. plus.
Also, just found out from the state that with the CEE no supplemental rod is required.
The generator main disc. which is connected to the generator frame, (bonded) will need to be connected to the grounding electrode system. All good.
Thanks for the help.
 
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dave121

Member
Location
Central Wisconsin
To make sure we are doing things to code, which in this case we were, we ask questions from our inspectors when we see them on site. We are fortunate here in Wi. to have our inspectors, state and otherwise so available to stay in touch with the code and to ask questions. Our installs are regularly inspected. We look at it as not so much a nuisance but as an opportunity to gain knowledge.

Thanks to all,
Got to go, just saw a White Walker
 
don_resqcapt19

don_resqcapt19

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Staff member
Location
Illinois
Occupation
retired electrician
kwired said:
.. Don't know I ever seen a GEC connected directly to one, is usually at first disconnect - usually within the center pivot control panel.

Most are only 10 kVA generators also.
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If there is no OPCD at the generator, the GEC connection and system bonding jumper at the first disconnect is fine. If there is an OCPD at the generator, the code requires those connections at the generator.
 
kwired

kwired

Electron manager
Location
NE Nebraska
don_resqcapt19 said:
If there is no OPCD at the generator, the GEC connection and system bonding jumper at the first disconnect is fine. If there is an OCPD at the generator, the code requires those connections at the generator.
Click to expand...
You probably don't want to know how many are out there with a 30 amp miniature 500 volt fuse block attached to back side of generator peckerhead cover for OCPD at the generator, and still no GEC until you get to the pivot panel, which may be within 10 feet or could be 2000 feet away.
 
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