Hi Everyone I have a question about the Ground Rods For A Duplex.

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cgamad550

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Hi everyone I have a question. If you have a duplex apt. 2 units and you have 2 meters and Service disconnects side by side. Do you need 2 ground Rods for each Meter/Service? So basically 2 Ground Rods for Unit A and then 2 Ground Rods for Unit B??
Thanks in advance.
 
infinity said:
Two ground rods, from the rods a #6 GEC to first service disconnect, split bolt tap another #6 to the GEC and run that to the second disconnect.
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Ok thanks. So just to verify 2 Ground Rods and then split off the first GEC to the 2nd Disconnect. So just 1 set of Ground Rods for Both Services. And yes they are Both 100 amp services.
 
cgamad550 said:
Thanks Larry I appreciate it.
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You're welcome.

To add, multiple electrodes must be bonded together anyway, to avoid lightning-driven voltage gradients from causing unwanted currents through common conductors like the neutrals.

Thus, you effectively have a single electrode system for the premises service, regardless of the number of meters and service disconnects. You would be driving four rods for one service.
 
LarryFine said:
You're welcome.

To add, multiple electrodes must be bonded together anyway, to avoid lightning-driven voltage gradients from causing unwanted currents through common conductors like the neutrals.

Thus, you effectively have a single electrode system for the premises service, regardless of the number of meters and service disconnects. You would be driving four rods for one service.
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Ok so I actually drive 4 round rods at least 6 feet apart and connect all with one #6 and the split bolt from there to both disconnects?
 
cgamad550 said:
Ok so I actually drive 4 round rods at least 6 feet apart and connect all with one #6 and the split bolt from there to both disconnects?
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No. Only a total of two rods are necessary. My apologies for the misleading mention of four.

I meant that you would otherwise unnecessarily be driving four when only two are needed.

An unbroken GEC need not go all the way to either panel, just to where it can be tapped/split.
 
I'm not sure if what I think you mean as a bridge qualifies.

A bus-bar would, but small spit-bolts are cheap and easy.
 
cgamad550 said:
Ok so basically can I connect it to a grounding Bridge and run line to each disconnect from there? Would that be within code?
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If by grounding bridge you mean an IBT then no. They're only for bonding communication equipment not for the splicing bonding jumpers to a GEC.

cgamad550 said:
Ok so the 2 rods and the just a split bolt to connect the 2nd disconnect
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That is just one way of doing it. Since your services are 100 amps you could also run a #6 GEC and tap off to each service disconnect with a #8.
 
cgamad550 said:
Hi everyone I have a question. If you have a duplex apt. 2 units and you have 2 meters and Service disconnects side by side. Do you need 2 ground Rods for each Meter/Service? So basically 2 Ground Rods for Unit A and then 2 Ground Rods for Unit B??
Thanks in advance.
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First to check... Is this new construction? If so, why don't you mention a Concrete encased electrode?

Second. To simplify other post. You need one grounding electrode system for the building. It will be made up of all grounding electrodes allowed and required by 250.52 and installation per 250.53. From there, you can run a grounding electrode conductor sized per 250.66 to each meter from any one of the grounding electrodes to each meter, or to one meter and then split to the other meter. I am saying the meters, because usually, the Utility requires a GEC to the meter anyway. Technically it can be boded to any point prior to the disconnects.
 
tried to edit:

Technically it can be bonded to any point at or prior to the disconnects. If you go to the meters, then you don't need to run any type ground or bond wire between the meters and the disconnects. Just bond the neutral to the disconnect enclosure.


So, scenario. 400A service. 2 sets of 4/0 aluminum. #6 copper between two ground rods. #4 from the foundation. #6 split bolted to the #4 and #4 split bolted to the #4 and then each #4 to a meter enclosure. (all split bolts underground.) Intersystem ground bar to either #4 just below the meter. Bond neutrals to disconnect with green screw at each disconnect. Run neutral and ground to each interior panel.
 
Strathead said:
tried to edit:

Technically it can be bonded to any point at or prior to the disconnects. If you go to the meters, then you don't need to run any type ground or bond wire between the meters and the disconnects. Just bond the neutral to the disconnect enclosure.


So, scenario. 400A service. 2 sets of 4/0 aluminum. #6 copper between two ground rods. #4 from the foundation. #6 split bolted to the #4 and #4 split bolted to the #4 and then each #4 to a meter enclosure. (all split bolts underground.) Intersystem ground bar to either #4 just below the meter. Bond neutrals to disconnect with green screw at each disconnect. Run neutral and ground to each interior panel.
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If the two disconnects are side by side chances are they are supplied by a single service drop or lateral. The GEC can be connected anywhere between the service disconnect(s) and the point of connection to drop or lateral.
 
kwired said:
If the two disconnects are side by side chances are they are supplied by a single service drop or lateral. The GEC can be connected anywhere between the service disconnect(s) and the point of connection to drop or lateral.
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We don't know the size of the service conductors or the disconnects. If we want to get technical, in the 400A scenario, I put above, I would use a single 400A conductor, I would just run a riser up for each meter at 200 amps and let the POCO splice them to whatever service drops they bring over. This could also be two meters in a single enclosure, or smaller service, etc. I wasn't trying to cite code, but offer a method. 250 is too big and convoluted to cite without EXACT scenario, as I know that you are fully aware of. Others will read this though, so I clarified. :cool:
 
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