Ground rods in Fairfax Co. Va

[larry4406]

I called the County again today and spoke with someone else in the inspections department. He said that 2 ground rods are required for a detached structure (without grounding through rebar)

So I am going to go ahead and put them in. Can't hurt and it seems like it's required by code. I'll ask the inspector who the first guy was when he comes out

This answer of ground rods now is because you did not do the UFER at time of concret pour and now have no choice.

 

[BillK]

I'll ask the inspector who the first guy was when he comes out

Probably not a good idea. At least not till you get your final. Even then I would probably keep my mouth shut.

 

[Lelandwelds]

I would probably keep my mouth shut.

Excellent general rule.

UFER actually work really well. I have plastic underslab so used a ground rod. Electrician insisted burying it sideways in the trench. I used four wire for the well house. Have another at pole from former panel.

What about noise from ground loops with multiple rods? They must be at different potentials right?

 

[wyliesdiesels]

I'm also in Fairfax County - and had the same issue years ago when I built my detached garage. Randy Bowman was my inspector and a knowledgeable, helpful sort. While, they do not require a ground rod/UFER gnd for a sub panel fed with a 4-wire system,...

Either you misunderstood him, or he's not knowledgeable. Judging by other comments about that county, I'd say the latter.

The number of wires feeding a subpanel has NOTHING to do with whether a GES/electrodes are required.

A subpanel in the same structure as the main service panel or primary subpanel does NOT require any electrodes whatsoever. Again, # of wires doesn't matter.

A subpanel in a detached structure has ALWAYS required a GES/electrodes, regardless of number of wires in the feeder.

....if you install one, its OK. In my case, I installed both gnd rods and a UFER system also connected to the rebar mesh under the slab.

The UFER/CEE is far superior and there is likely no benefit to installing rods as a supplemental to the CEE

Excellent general rule.

UFER actually work really well. I have plastic underslab so used a ground rod. Electrician insisted burying it sideways in the trench. I used four wire for the well house. Have another at pole from former panel.

What about noise from ground loops with multiple rods? They must be at different potentials right?

There is no such thing as noise from ground loops between rods. Where did you hear about this?

Ground rods are for suppressing lightning. No amount of fault current flows on ground rods.

 

[lakelandcat]

I called the County again today and spoke with someone else in the inspections department. He said that 2 ground rods are required for a detached structure (without grounding through rebar)

So I am going to go ahead and put them in. Can't hurt and it seems like it's required by code. I'll ask the inspector who the first guy was when he comes out

Make sure they are 6' apart and 2" below grade

 

[Lelandwelds]

Either you misunderstood him, or he's not knowledgeable. Judging by other comments about that county, I'd say the latter.

The number of wires feeding a subpanel has NOTHING to do with whether a GES/electrodes are required.

A subpanel in the same structure as the main service panel or primary subpanel does NOT require any electrodes whatsoever. Again, # of wires doesn't matter.

A subpanel in a detached structure has ALWAYS required a GES/electrodes, regardless of number of wires in the feeder.



The UFER/CEE is far superior and there is likely no benefit to installing rods as a supplemental to the CEE



There is no such thing as noise from ground loops between rods. Where did you hear about this?

Ground rods are for suppressing lightning. No amount of fault current flows on ground rods.

Lurking on electronics forum discussing electrical noice likely from surge protectors and multiple grounding rods. Claimed excess voltage was dumped through grounding system.

 

[wyliesdiesels]

If it was an issue for power systems, the NEC wouldve addressed it.

Also, if you reread what i wrote, you would see that i alluded to the ground rods not being the thing that generates the noise.

Another device is creating the noise and its injecting it into the equipment grounding system and GES.

Ground rods on their own cannot create noise.

BTW, it would've been good to backup your statement with a reference.

 

[mm08822]

Lurking on electronics forum discussing electrical noice likely from surge protectors and multiple grounding rods. Claimed excess voltage was dumped through grounding system.

Ground loops is a phenomenon often associated with small signal applications rather than in power -- that is, a potential difference between two ground paths could introduce noise. It could also be an issue in power with respect to ground potential in case of lightning strikes, etc but is more covered by the NESC rather than by the NEC because it addressed in distribution/transmission issues rather than in utilization applications.

Electrical noise from surge suppressors is the result of them doing their job - clipping/attenuating spikes off of the system. Multiple ground rods has nothing to do with this.

Excess voltage from static electricity and lightning strikes gets brought to earth in a quick and more deterministic path - e.g. - ground rods, ufers. This is needed for occupant safety.

How many homes haves small signal applications as in industry? Relevance to this thread?

G.E. systems installed at a residence is not going to address noise impressed upon transmission lines.

 

[sberry]

This is somewhat a reoccuring problem. Electronics guys often think they are special and exempt from codes because they "don't understand" which is rational for doing it some other way instead of following the instructions. If one doesn't understand real logic says then maybe do it the way they say. Our phone company had a couple of these dandys, got to wonder how much it cost them and customers.
I asked one, you ever have a class or any training? Nope, hand to mouth and riding in the truck for a month and then turned loose on your property.
Btw, there should not be potential differences here, all are sposed to be connected together via the ground wire no matter how many or where the rods are.

 

[sberry]

I wired a house for a retired electrical engineer. Apparently you can get a degree in this without opening a code book and he isn't the only one I have ran across.

 

[rlitman]

LOL above, here in the big city they require both a UFER and two 8' rods. City amendments to the code. Drives the sparkys I know nuts, never got a reason from the city about why. "Because they can" is assumed. Maybe "backlash" in response to 100s of non-compliant structures.

Could it be related to your local soil conditions. Around here, on sandy soil with a shallow water table, grounding is very easy. That's not the case everywhere though.

 

[Ryan]

Cleaned this thread up a bit. Guys. If you can’t talk about this stuff without arguing, please find another forum.