Ground Rod at Standby Generator

[ceb58]

I have to join don with the question as I see nothing in 250.50 that leads me to think a grounding electrode is required. Can you elaborate ?

And I join in with Gus and Don. Unless the mfg. instructions tell you you must install a ground rod then one is not needed. If you check your ground buss on the gen. I bet you will find it connected to the frame and nothing else is needed.

 

[romeo]

Ground Rod at Standby Generator

I agree that a GE is not required. The EGC is connected to the grounded neutral and the GES at the transfer switch. Ground rod or rods not required by the NEC at the generator. It seems to me if the mfg. wanted a grd rod at the generator they would provide a means to terminate it.

 

[tom baker]

Secondly, in my opinion, according to 250.50, all Permanently Installed Generators are going to require a Grounding Electrode at the Generator. How and where you wire in the Grounding Electrode Conductor to this Grounding Electrode depends on whether the Generator is Separately Derived or Nonseparately Derived.

The NEC does not require a grounding electrode system at all permanently installed generators, only those that are a SDS. A non SDS generator is grounded at the building electrical service and bonded via the main bonding jumper. See the required sign in 701.7(B)

 

[taylorp]

I agree that a GE is not required. The EGC is connected to the grounded neutral and the GES at the transfer switch. Ground rod or rods not required by the NEC at the generator. It seems to me if the mfg. wanted a grd rod at the generator they would provide a means to terminate it.

The NEC does not require a grounding electrode system at all permanently installed generators, only those that are a SDS. A non SDS generator is grounded at the building electrical service and bonded via the main bonding jumper. See the required sign in 701.7(B)

250.50 requires a Grounding Electrode and Grounding Electrode Conductor at each structure. I suppose we could argue until Christmas whether an Optional Standby Generator is a separate ?structure.? If you poured a concrete slab which contained 20 feet of reinforcing rods and put your generator on top of it, then you have built a separate structure and you are required to have a GEC and Grounding Electrode at this structure. It all depends on what your definition of is is.

By my definition, a Permanently Installed Generator installed in a separate location is a separate structure. What the AHJ says is another matter.

As far as Generator design, how do manufactures know how you will install your generator? A separately derived system clearly requires a GEC and GE at the generator according to 250.30. As I have said in an earlier post, many generator manufacturers have not kept their designs up to date with changes in the NEC in my opinion.

By installing a GEC and GE at the Generator, no matter whether it is a Separately Derived System or not, connection to the earth should limit the voltage imposed by lightning, line surges, or unintentional contact with higher-voltage lines and will stabilize the voltage to earth during normal operation.

 

[romeo]

Ground Rod at Standby Generator

250.50 requires a Grounding Electrode and Grounding Electrode Conductor at each structure. I suppose we could argue until Christmas whether an Optional Standby Generator is a separate ?structure.? If you poured a concrete slab which contained 20 feet of reinforcing rods and put your generator on top of it, then you have built a separate structure and you are required to have a GEC and Grounding Electrode at this structure. It all depends on what your definition of is is.

By my definition, a Permanently Installed Generator installed in a separate location is a separate structure. What the AHJ says is another matter.

As far as Generator design, how do manufactures know how you will install your generator? A separately derived system clearly requires a GEC and GE at the generator according to 250.30. As I have said in an earlier post, many generator manufacturers have not kept their designs up to date with changes in the NEC in my opinion.

By installing a GEC and GE at the Generator, no matter whether it is a Separately Derived System or not, connection to the earth should limit the voltage imposed by lightning, line surges, or unintentional contact with higher-voltage lines and will stabilize the voltage to earth during normal operation.

It may be ok to install a GES if it is not separately derived but remember that a egc is still required and the grounded conductor must be kept isolated. JMO

 

[augie47]

250.50 requires a Grounding Electrode and Grounding Electrode Conductor at each structure......................

(I didn't copy the entire quoted post, but enough to identify)

Since you quoted 250.50, I assumed the "stricture" was where you were leading, and I agree that the NEC "structure" definition makes such calls difficult as has been discussed on several earlier threads (one involved a external MCC).
An AHJ can obviously make that call but I can see a couple of "problems" in doing so. 1st, are we "feeding" the "septarate structure".. more correctly that "structure" is feeding the house. 2nd, if we do approach it from the 250.50 section, are we going to require a service rated disconnect on the circuits used to supply the heater/charger, etc on the generator ? How about the control circuits ? Do any of these violate 225.30 ??
The "generator" is a separate structure is a path I don't think most would wish to pursue.

 

[don_resqcapt19]

I agree that the generator is a structure, but I don't agree that it requires a grounding electrode as it is not a structure that is supplied by a feeder from another structure. In most cases the generator structure is supplied by a branch circuit. I don't see a code rule that requires the generator structure to have a grounding electrode system, unless it is supplied by a feeder.

 

[George Stolz]

The generator supplies a building, it is not supplied. You might have a branch circuit supplying a heater and/or a battery charger at the generator, but that is a branch circuit. I agree with Gus and Don, 250.50 does not apply to a non-SDS.

 

[hillbilly1]

The small Kohler that I installed a couple of months ago did not have a lug for the GEC. Unlike Generac's units. The homeowner wanted it on a hill behind his house about 60' away, so I installed a lug on the frame to a ground rod just for the off chance of a possible lightning strike nearby and the generator being up high.

 

[ceb58]

The small Kohler that I installed a couple of months ago did not have a lug for the GEC. Unlike Generac's units. The homeowner wanted it on a hill behind his house about 60' away, so I installed a lug on the frame to a ground rod just for the off chance of a possible lightning strike nearby and the generator being up high.

And try to get Generac to explane why they require a ground rod. They cant or wont. So you are stuck with 110.3 B

 

[tkb]

...

 

[Billybob1]

System Bonding Jumper

System Bonding Jumper

I recently failed an inspection for not removing the system bonding jumper at the transfer switch. This was not a seperately derived system.

 

[romeo]

Ground Rod at Standby Generator

I recently failed an inspection for not removing the system bonding jumper at the transfer switch. This was not a seperately derived system.

If the jumper is bonding the grounded conductor to transfer switch then it is a violation, if it is bonding the egc it is correct. 250.34 and 35 IMO

 

[stickboy1375]

I have a Kohler Generator that I installed, my first one, and it has a poly enclosure. The Generacs I have done previously are pretty straight forward, with a lug on the enclosure to connect the grounding electrode conductor. The Kohler has no such provision, and was wondering if there is anyone out there that has installed one, and what they have done to install one. Did you even install one? Is it required with a poly enclosure?

TIA

Brendon

I install these units all the time, and as already mentioned, a ground rod is not required...

 

[Gudenkauf Electric]

J Gudenkauf

J Gudenkauf

My thought is that if it is not a metal inclosure it does not need the ground rod. That the ground rod is just for the inclosure grounding for stray voltage. Or it would be in the Specs of the generator.

 

[navyman]

I've been studying this issue for four days now. mainly reading about it on the internet to understand it "electrically". Also looking at different diagrams I have found online.
From what I understand..most "portable generators" have the neutral and ground tied together and connected to the frame....Same as your service entrance(neutral and ground together). A "portable generator is designed to be used say on a job site for portable tools with three prong plugs and gfci protection. Once the generator is used to supply your house and your neutral is not switched from the Gen.(non-sds system) you create a parrallel path for current to flow. GFCIs will sense current on the ground and trip. A service neutral and ground can only be tied together at on point, If you notice when a sub-panel is installed...neutral -ground is seperated. So if the neutral is solidly connected from Gen. to service entrance it's a non-sds system requiring a grounding electrode.

 

[augie47]

And try to get Generac to explane why they require a ground rod. They cant or wont. So you are stuck with 110.3 B

I spent an hour on the phone one day with a Generac engineer attempting to learn as to why there was a need for a GE on a Generac non SDS unit.
He insisted that it was necessary in the event there was a "short" ahead of the generator OCP device. He claims there are electronics with the generator that rely on the ground rod to provide proper protection.
I was never convinced, but perhaps that has a lot to do with my thick head..... I ended up going back to 110.3(B)

 

[hillbilly1]

I spent an hour on the phone one day with a Generac engineer attempting to learn as to why there was a need for a GE on a Generac non SDS unit.
He insisted that it was necessary in the event there was a "short" ahead of the generator OCP device. He claims there are electronics with the generator that rely on the ground rod to provide proper protection.
I was never convinced, but perhaps that has a lot to do with my thick head..... I ended up going back to 110.3(B)

They gave you a good non-answer, A short ahead of the generator OCP, would likely stall the motor since the ground and neutral is bonded together at the service. :roll: