Ground Loop location

[faresos]

1. How far the ground loop needs to be a way from the foundation? Normally I locate it at 36" away from the foundation, but the contractor saying he can not locate the ground loop at this location because of rocks back filling, he says it will be about 10' away from the foundation. Is this acceptable?

2. Does the ground rods needs to be inserted in undisturbed earth (not in back filled earth)?

 

[infinity]

What kind of structure are you wiring that would cause you to use a ground ring? (At least I think you meant a ground ring not a ground loop).

 

[gndrod]

What kind of structure are you wiring that would cause you to use a ground ring? (At least I think you meant a ground ring not a ground loop).

I don't think he meant loop either. That is used in electronics more as a signal feedback term. At one time long ago, I had the opportunity to install an earth ground ring system around a new transmitter station. The ring was required to diametrically be radially buried around the building about in a ten foot radius from the hut. rbj

 

[faresos]

It's for lightning purpose and I'm not sure what is the different between a ground loop and a ground ring. The structure of the building is steel and precast exterior wall. It is anticipated that the entire perimeter of the exterior of the building will be backfilled with stones to prevent water buildup against the waterproofed grade beam wall. Shouldn't the grounding ring be install outside of this area receiving stone backfill as the loop will not ground properly if placed in rock? Would be any issues to install the ground ring 10' from the foundation?

Thanks again,

 

[infinity]

Would be any issues to install the ground ring 10' from the foundation?

Thanks again,

No, the farther from the building to larger the ground ring. Why are you using a ground ring in the first place? Is this a job specification?

 

[iwire]

I'm not sure what is the different between a ground loop and a ground ring.

Well the NEC describes how to make a ground ring but is silent about ground loops.

As far as the NEC is concerned as long as the ring encircles the building and is in contact with the earth it is acceptable

Take a look at 250.52(A)(4) and 250.53(F)

The NEC does not prohibit ground rods in back fill, but IMO the backfill would have to be 'earth' and to me crushed stone is not earth.

Take a look at 250.52(A)(5), 250.53(A), and 250.53(G)

 

[stickboy1375]

The NEC does not prohibit ground rods in back fill, but IMO the backfill would have to be 'earth' and to me crushed stone is not earth.

Take a look at 250.52(A)(5), 250.53(A), and 250.53(G)

Bob, correct me if I'm wrong, when I read 250.53(G), it seems the first option is to actually drive the rod, but if you hit rock then a 45 degree angle is acceptable, if that doesn't work then you are allowed to just throw em' in a 30" deep ditch... But must still be in contact with soil.

 

[dereckbc]

I have designed a lot lightning protection systems for telephone companies and wireless carriers and what you are getting into is a design issue rather than a NEC issue.

If you go by UL-96 or NFPA-780 design guidelines the proper technique is the down conductors go directly to a ground rod at the foundation perimeter, then bonded to a buried ground ring. So yes the ring can be located some distance from the building foundation.

 

[ItsHot]

loop vrs. ring

loop vrs. ring

Well the NEC describes how to make a ground ring but is silent about ground loops.

As far as the NEC is concerned as long as the ring encircles the building and is in contact with the earth it is acceptable

Take a look at 250.52(A)(4) and 250.53(F)

The NEC does not prohibit ground rods in back fill, but IMO the backfill would have to be 'earth' and to me crushed stone is not earth.

Take a look at 250.52(A)(5), 250.53(A), and 250.53(G)

I had a similar question/post once. Is a ground loop what they usually install around a cell phone tower?

 

[faresos]

No, the farther from the building to larger the ground ring. Why are you using a ground ring in the first place? Is this a job specification?

It's for lightning system for a data center.

Thanks for all for their responses.

 

[dereckbc]

First it is called a GROUND RING, not a loop. Second there should not be any detail left to the discretion of the contractor for this type of application. All materials, connections, mechanical execution of work should be very specific and detailed. If the engineer in charge did not do this both the contractor and engineer are in for some nasty surprises.