Greg1707
Senior Member
- Location
- Alexandria, VA
- Occupation
- Business owner Electrical contractor
Sharing ground rods with adjacent service
- Thread starter Greg1707
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jumper
Senior Member
- Location
- 3 Hr 2 Min from Winged Horses
Is it really going to be two services or one service drop shared?
Is this really considered two structures?
Is this really considered two structures?
Last edited:
winnie
Senior Member
- Location
- Springfield, MA, USA
- Occupation
- Electric motor research
If you read 250.53, I believe that code requires not only separate ground rods, but that the ground rods be separated by a minimum distance.
If you share the ground rods, then you have the same sort of problem associated with common metallic water piping: neutral current flowing via the shared grounding electrodes and through the neighbor's neutral.
Physics wise, I think it would be preferable to share the ground rods; otherwise currents through the soil could enter one set of ground rods, travel through the neutral wires, and exit the other set of ground rods. But I don't think that is what the code says.
-Jon
If you share the ground rods, then you have the same sort of problem associated with common metallic water piping: neutral current flowing via the shared grounding electrodes and through the neighbor's neutral.
Physics wise, I think it would be preferable to share the ground rods; otherwise currents through the soil could enter one set of ground rods, travel through the neutral wires, and exit the other set of ground rods. But I don't think that is what the code says.
-Jon
Greg1707
Senior Member
- Location
- Alexandria, VA
- Occupation
- Business owner Electrical contractor
- Occupation
- Licensed Electrician
Following up on jumper's second question, how is this not one structure?
- Location
- Chapel Hill, NC
- Occupation
- Retired Electrical Contractor
Imo, you can share the rods
- Occupation
- Licensed Electrician
Yes, but can he have two services.
Greg1707
Senior Member
- Location
- Alexandria, VA
- Occupation
- Business owner Electrical contractor
two houses
two houses
two houses
There are two houses. There is a meter on the rear on one and we will be installing a meter on the side of the other house.
kwired
Electron manager
- Location
- NE Nebraska
- Occupation
- EC
Is what is shown both of those houses? End result being a two family dwelling.
IMO if service disconnects are grouped at one location it kind of doesn't matter if it is considered two structures or not, common grounding electrodes should be fine.
If you only had a single metal water pipe supplying both dwellings - you don't have to install a second metal water pipe just because there is two service disconnecting means.
- Location
- Chapel Hill, NC
- Occupation
- Retired Electrical Contractor
They appear very much attached. Are they both on the same property?
And as noted, a single service drop is one service no matter how many service entrance conductors split off of it. The AHJ and POCO may call it separate services if it supplies more than one property.
texie
Senior Member
- Location
- Fort Collins, Colorado
- Occupation
- Electrician, Contractor, Inspector
Based on the photo in the OP, this is one structure. 250.58 requires all services, etc. to use the same GES. Installing a SEPARATE GES of, say, 2 more ground rods is not compliant. The OP could add 1 or more ground rods if desired but all electrodes would have to be bonded together to form a single GES.
kwired
Electron manager
- Location
- NE Nebraska
- Occupation
- EC
If a multi occupancy building you possibly can have more then one service.
If there is only one service drop or lateral it is still one service though.
If there is only one service drop or lateral it is still one service though.
- Location
- Bremerton, Washington
- Occupation
- Master Electrician
Exactly...In Washington we have a state code rule that prohibits sharing ground rods since you will have the bldg. neutrals in parallel and will have objectionable current.
kwired
Electron manager
- Location
- NE Nebraska
- Occupation
- EC
How many older neighborhoods do you have with metal water piping and all services bonded to that water piping?
And the metal shields on telephone, CATV all connected to every service as well?
electrofelon
Senior Member
- Location
- Cherry Valley NY, Seattle, WA
- Occupation
- Electrician
I dont see how you can say that just looking at the photo. Clearly its Pretty common to have several buildings, often a whole block, physically touching each other.
Greg1707
Senior Member
- Location
- Alexandria, VA
- Occupation
- Business owner Electrical contractor
I thought the Grounding Electrode System was connected through metal water pipe and service neutral so that the entire system was bonded together? That is all structures in the city sharing water pipe and all of the neutrals and ground rods through the system are bonded into one huge system?
texie
Senior Member
- Location
- Fort Collins, Colorado
- Occupation
- Electrician, Contractor, Inspector
I think you are confusing the requirement to have individual electrodes such as ground rods to have a minimum separation of 6' as required in 250.53. This only applies to the INDIVIDUAL ground rods-not the grounding electrode system. All electrodes in a GES must be bonded together.
And as I mentioned in my previous post, 250.58 requires all systems in a building use the same GES.
As for Tom's remarks about Washington State requirements for separate GES for each disconnect, well, I'm not sure what to say about that as it is a direct violation of the NEC.
IMO there is only one condition which determines one vs. two GES's, and that is whether or not the buildings are on one or two properties.
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