Grounding Questions, Electrical

   #1  

Diggin It

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I have two ground rods within 5' of the house, 10' apart, connected with #6 THHN. Closest rod is connected to panel with #6 solid.

Shed/Barn out behind house has a 12/2 UF for power for some lights and general outlets. Planning on changing that to 10/2 at some point. Ground is provided that way, no separate ground rod.

LP tank is 100' from the house, out by the road. Gas line is poly/plastic, so no ground connection via pipe.

Considering a third ground rod at the house, but do I want it in a straight line from the others along the house? Or should it go out, away from the house, forming a T or L?

Do I need a ground rod out by the LP tank since it uses poly pipe and is not tied to any existing ground?

Do I need another ground rod at the shed tied to the ground of the UF?


Sketch is NOT to scale.


Grounding.png
 
   #2  

LittleBill21

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there is no requirement to add a 3rd ground per nec. you should not have separate derived grounds, it causes more trouble, all grounds should be tied to the same point, if they are all tied to the same panel.
 
   #3  

etpm

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For power supplied from one source all the grounds and neutral must also come from the same source. For example, I recently installed and had inspected a generator transfer switch/breaker panel combination. I passed the inspection. So now I have two load centers, AKA breaker panels. For the second panel I had to not only bring power from the main panel I also had to bring the ground and neutral. The second panel supplies power to some of the house circuits but also powers a structure a couple hundred feet from the house . To meet code I had to run the power wires, plus the neutral and ground, out to the structure. The structure has 240 volts as well as two 120 volt circuits. I could add another load center in the structure but the ground and neutral would still need to come from the main panel at the house. The inspector from the state quizzed me on the ground and neutral wiring and told me this was one of the most common mistakes he saw, having separate grounds but not separate power sources. So you don't need another ground rod. If the building was metal you could ground it with another rod but then you would need to make sure it could never be connected to the same ground as your wiring. If you do run new wires to the building you will need 3 wires for 120 volts and 4 for 240 volts, one of those wires being the ground and one being the neutral.
Eric
 
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grsthegreat

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you do not need to ground a propane tank. you also do not need to set a ground rod at outbuilding if its fed by 2 or less circuit (ie uf cable). as you do not need a panel in an outbuilding if there is only 2 or less circuits feeding building.

if you install a breaker panel, at least where i work, you have to feed that panel with 4 wires (2 hots,neutral and ground) and you need to add a ground rod tied onto incomming ground wire. the new panel would be required to separate grounds and neutrals.

but since you dont have a need for a panel, dont worry about any of this.
 
  
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Diggin It

Diggin It

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The 12/2 UF (w/ground) goes to a two space panel with two 15A breakers, so there is only 120V out there. That's just really to allow me to turn power off out there if I need to do anything. I have no need for 240V.

When I change and run 10, I may go ahead and use 10/3 UF (w/Ground) just for future. But that will still all be tied to the existing two ground rods as all of the ground wires are tied back there.

The notion of a third ground rod is as much for lightning or other faults as anything else.

I wasn't sure about the LP tank though.
 
   #6  

grsthegreat

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One thing I don’t remember, and too lazy to look up, is whether changing it to 10/3 and going 30 amps, I think a subpanel is required. Mind you, I never bother running a circuit to another structure at less than 50 amps. I like power wherever I go.
 
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sandman2234

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One thing I don’t remember, and too lazy to look up, is whether changing it to 10/3 and going 30 amps, I think a subpanel is required. Mind you, I never bother running a circuit to another structure at less than 50 amps. I like power wherever I go.
I am in agreement with you, if I am going to dig a ditch or however it is run, I am going to run the biggest cable I can afford. I am also going to run 220 so I have the most chance at the most power at the remote site.
The current set up is with 12/2 with ground feeding two 15 amp breakers. Seems like he is already behind on his wire size if I am not mistaken. I thought it took 10 ga to pull run 30 amps that far (although not to scale was noted)!
David from jax
 
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grsthegreat

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He’s only running 15 amps, not 30. He’s not combining the circuits. The wire size is fine.
 
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RalphVa

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I have two ground rods within 5' of the house, 10' apart, connected with #6 THHN. Closest rod is connected to panel with #6 solid.

Shed/Barn out behind house has a 12/2 UF for power for some lights and general outlets. Planning on changing that to 10/2 at some point. Ground is provided that way, no separate ground rod.

LP tank is 100' from the house, out by the road. Gas line is poly/plastic, so no ground connection via pipe.

Considering a third ground rod at the house, but do I want it in a straight line from the others along the house? Or should it go out, away from the house, forming a T or L?

Do I need a ground rod out by the LP tank since it uses poly pipe and is not tied to any existing ground?

Do I need another ground rod at the shed tied to the ground of the UF?


Sketch is NOT to scale.


View attachment 716951
Think I'd put a ground by the LP tank. There's a ground by our generator and also at each building: house and carriage house.
 

grsthegreat

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Generators should not be grounded either. Generac did away with grounding generators about 10 years ago, the grounding was done thru the ground wire run to house. Too many separately derived grounds are not a good thing.

multiple ground rods HAVE to be tied together, and actually are not desirable.

I have never seen anyone ground a propane tank.
 

skipmarcy

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My Generac generator bought new in 2019 has the grounding lug on the frame - I use a #6 copper wire from it to my ground rod in the ground below my electric meter - just use a pair of vise-grips to attach the wire to the top of the rod.
 

grsthegreat

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generac did away with the grounding lug back around 2015ish. They even put out a statement to the fact not to use a ground at generator, as it created a separately derived grounding situation. Basically they redesigned their systems to ground thru building wires. I’m surprised your 2019 unit had one.
 

ponytug

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Doesn't it depend on the details of how the generator is constructed and how it is wired in? If you are interested, you can see OSHA's fact sheet here.

I have to admit, I follow the logic of not wanting ground loops, and why you wouldn't want ground currents traveling through conduits, but I have seen out buildings treated both to separate ground rods, and ground wires derived from the main panel.

Caveat: I am not an electrician and don't play one on TV! I don't know the current NEC regulations at all well. I have seen well thought out opinions by "experts" go both ways. Certainly one interpretation of the post 2008 electrical code has a ground loop design, others don't.

Anyone who is an expert care to weigh in?

All the best,

Peter
 
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Diggin It

Diggin It

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Doesn't it depend on the details of how the generator is constructed and how it is wired in?

Anyone who is an expert care to weigh in?
GRS is a factory trained rep for Generac with decades of experience on many of their models. When it comes to 'expert' on generator installations, you won't find another here on this board that can exceed that.

Mine has #6 from the generator to the ATS that is tied to the main panel and meter which are tied to two ground rods, all within 15' of each other. I just wasn't sure if a third ground rod tied to the first two would either help or hurt

As far as grounding in general, one of the lineman here on the board may have some additional comments.
 

skipmarcy

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My Generac is a portable unit and I use it exclusively with extension cords only - the ground lug wired to the house's ground rod is the only ground the whole system has - I do not have any interface with the house wiring at all.
 

grsthegreat

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Ah…portable. That’s a whole different thing. Portable generators still come with ground lugs, because they are generally used remotely to power equipment and not tied into a house system. I was referring to standby units not needing grounding rods.
 
 
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