Grounding detached building...Home

[electricontr]

We installed a new service on a garage and fed the house overhead from the garage with a fourplex loop, two hots, one neutral(grounded conductor) and a bare grounding conductor. We drove two ground rods at the garage. We also connected a #6 cu from the water service to the panel on the house. In my mind, the house is grounded by the the water service pipe and the grounding conductor from the ground rods at the garage via the fourplex grounding conductor. The inspector disagrees. He says that we need ground rods at the house too. Comments

 

[kwired]

We installed a new service on a garage and fed the house overhead from the garage with a fourplex loop, two hots, one neutral(grounded conductor) and a bare grounding conductor. We drove two ground rods at the garage. We also connected a #6 cu from the water service to the panel on the house. In my mind, the house is grounded by the the water service pipe and the grounding conductor from the ground rods at the garage via the fourplex grounding conductor. The inspector disagrees. He says that we need ground rods at the house too. Comments

Inspector is correct.

Each structure needs it's own grounding electrode system. This requirement is in 250.50

The garage GES is a separate GES from the house.

250.53(D)(2) requires a metal underground water pipe to be supplemented by another electrode

ADD: the supplemental electrode doesn't have to be a ground rod - it can be any electrode mentioned in 250.52(A)(2) through (8) - which is all electrode types except for the water pipe which is (A)(1). Most people just drive rods if there is no other electrode present.

 

[ActionDave]

Your inspector is correct. 250.53(D) says that a water pipe needs a supplemental grounding electrode. It doesn't have to be a ground rod but that is one of the easiest qualifying electrodes on the list.

 

[JFletcher]

Thought you needed a #4 to buried copper water line?

 

[ActionDave]

Thought you needed a #4 to buried copper water line?

Depends on the service conductor size.

 

[kwired]

If ungrounded supply conductors are #2 copper, 1/0 aluminum or smaller the GEC is only required to be 8 AWG copper.