residential remote service grounding

[mltech]

I have a new home going up that requires an overhead 400amp service attached to a remote garage 120' away from the main house it supplies. There is a 100kw generator with service rated transfer switch between the meter can and 400MDP. Can I run a seperate conduit to the home in the same trench as the 400 amp feeders for the uffer ground and cold water bond? My goal is to use the Transfer switch as the single point of bonding the service, drive a ground rod (or 2) and then hit the house.
Any thoughts are appreciated.
Thanks,
Mike

 

[augie47]

With a detached garage, I would simply follow 250.32, and other than the required equipment grounding conductor , not try to interconnect the grounding electrode systems.

 

[winnie]

Each building will require its own grounding electrode system.

In the building with the service, the grounding electrode system will be bonded to the electrical system neutral.

The feeder to the detached building will require an EGC.

In the detached building, the grounding electrode system will be connected to the EGC.

I see no code requirement for an additional GEC or electrode bonding conductor from one building to the other.

There might be a design reason for such an additional conductor, for example to provide additional protection from earth currents caused by lightning strikes, but evaluating that is beyond the scope of the NEC and well beyond my experience. I could imagine current flowing into an electrode at one building, via the EGC to the other building, and out the electrode there...but have no basis in fact to back up that imagining.

I see no code prohibition preventing such additional GEC or electrode bonding conductor joining the grounding electrode systems of the two buildings if one is desired.

-Jon

 

[mltech]

What if there is no water at the existing building and since it is existing no footer bond.
Just 2 driven ground rods would have to be sufficient...

 

[Dennis Alwon]

Just 2 driven ground rods would have to be sufficient...

That is correct.

 

[Dennis Alwon]

Make sure that you are only bringing one feeder from the garage to the house. Two feeders would be a violation--- 225.30. Paralleled feeder is, of course, accepted.